Session category overview

A03_Transparent conductive films and smart coatings

Date: 27-05-2024

Time: 13:45-16:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Investigation of Oxygen Vacancies in sputtered GDC thin films probed via operando XAS and Raman Spectroscopy

Nunzia COPPOLA

Abstract

Nowadays it is well known that the introduction of a Gadolinium Doped Ceria (GDC) barrier layer at the cathode/electrolyte interface is able to increment the performances of Solid Oxide Fuel Cells (SOFCs). Although the GDC’s main role is to reduce interface diffusion, its ionic conductivity plays also a central role. Once the Gd doping percentage is fixed, the ionic conductivity of the GDC layer depends upon the specific structure, granularity, defect incorporation and the number of oxygen vacancies induced in the film’s lattice.

In past works, we reported a huge increment of output current (up to +78%) and a decrement of ohmic resistance (up to -42%) in SOFCs in which the barrier layer is a room-temperature sputtered GDC thin film, compared to fully screen-printed industrial SOFCs. We correlated the performance improvement to the reduced grain size in the GDC layer annealed at lower temperature; nonetheless, in these studies no information could be extrapolated about the density and activity of oxygen vacancies in the thin film.

Element and valence sensitive probes such as quantitative X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Absorption Spectroscopy (XAS) allow to achieve the atomic level characterization of the nanostructured granular GDC layers deposited on polycrystalline anode/electrolyte bilayer substrates and the interplay between morphology and stoichiometry in determining the Ce3+/Ce4+ ratio that rules their ionic and electronic conductivity.

Here we show the results obtained on three GDC room-temperature RF-sputtered GDC thin films, annealed with the same annealing ramp but at different plateaux temperatures, making use of XPS measurements to investigate the unreacted surface and the operando XAS to monitor the changes in Ce3+/Ce4+ ratio in different reactive atmospheres (namely neutral, oxidating and reducing). The measurements were conducted making use of the ambient pressure cell available at APE-HE beamline (Elettra synchrotron in Trieste, Italy) and allowed to determine the annealing parameters role in the number of available oxygen vacancies in oxygen-reduction reaction (ORR), highlighting different changes induced in the investigated samples by the annealing ramp.

Raman Spectroscopy meaurements performed on the same samples hinted that the different response to gas atmospheres of the two samples and the different Ce3+ Ce4+ dynamic can be ascribed to a different Gd defects mobility inside the lattice.

A Highly-intermixed Nanocomposite as a Thin Film Air Electrode in a Solid Oxide Cell

Fjorelo BUZI

Abstract

Thin film technology has been widely employed for materials engineering for both fundamental studies on novel systems and on established systems for improvement of their functionalities through nanoengineering approaches. In the case of thin film-based air electrodes for solid oxide cells (SOCs), several strategies have been reported for performance enhancement such as heterostructuring, multilayering and grain-boundaries engineering^1-4. Efforts to improve oxygen reduction reaction (ORR) kinetics and films durability at high temperatures were made. Nonetheless, the path for the implementation of thin films into real devices presents many challenges. In this work, thin film-based cathodes 3 orders of magnitude thinner than commonly used bulk electrodes (200 nm-thick ca.), produced via large-area pulsed laser deposition technique, were introduced as novel oxygen electrode layers in Ni-YSZ anode-supported SOCs for reversible operation. A thin barrier layer was deposited in between the electrolyte/cathode interface as a protective interlayer to block cations interdiffusion⁵. Specifically, a novel self-assembled nanocomposite layer of lanthanum strontium cobaltite (LSC) and samarium-doped ceria (SDC) was investigated using a suite of complementary techniques for structural, compositional and electrochemical investigation, including atom probe tomography. Performances of the nanocomposite film as an air electrode in a full SOC unveil a unique combination of good electrochemical activity for reversible operation (310 mW.cm^-2 peak power density reached at 0.6 V in fuel cell mode and electrolysis current density of 590 mA.cm^-2 at 1.4 V, both recorded at 700 ºC) and long-term stability (5.1% V.kh^-1 degradation rate at 700 ºC under 0.2 A.cm^-2in fuel cell mode). This work reveals the potential of thin-film heterostructuring for obtaining high-performance air electrodes with long durability and minimized use of critical raw materials.

1. Baiutti, F. et al. Nat. Commun. 12, 2660 (2021).

2. Sirvent, J. D. D. et al. ACS Appl. Mater. Interfaces 14, 42178–42187 (2022).

3. Chiabrera, F. et al. Adv. Mater. 31, 1805360 (2019).

4. Buzi, F. et al. Submitted (2024).

5. Bernadet, L., Buzi, F. et al. APL Energy 1, 036101 (2023).

Prediction of oxygen electrode performance of high-entropy perovskites La0.8Sr0.2(Co,Fe,Mn)O3 with machine learning based on spectroscopic characterization data

Carlota BOZAL-GINESTA

Abstract

Lanthanum, strontium-based perovskites (ABO3) are among the state-of-the-art cathode materials for solid oxide fuel cell operating at intermediate and low temperatures (<800 ºC). However, the effects of the composition on the nanostructure and the intrinsic properties of the materials and on the electrochemical performance are typically non-linear and hard to generalize. Machine learning techniques have emerged as an unprecedented tool to identify complex patterns in large datasets, also in heterogeneous electrocatalysis. Herein, we have applied these techniques to delve deeper in the composition-property-performance relationships of La0.8Sr0.2(Mn,Co,Fe)O3±𝞭 and predict performance maps that can help optimize these materials. High-throughput characterization of a compositional map of La0.8Sr0.2(Mn,Co,Fe)O3±𝞭 has been carried out: information on the metal stoichiometry, the crystallinity, electrochemical performance, the structural symmetry, and the electronic configuration was obtained from X-ray diffraction (XRD), X-ray fluorescence (XRF), electrochemical impedance spectroscopy (EIS), Raman spectroscopy and ellipsometry, respectively. We processed the raw data to derive characteristic features and match the samples from different measurements. Then, a variety of supervised and unsupervised modern machine learning methods were utilized to build highly generalizable models correlating experimental features relative to the composition, the optical properties and electrochemical properties of the materials, and to identify the most relevant ones. Experimental data from Raman and ellipsometry and XRD measurements have been demonstrated to model the material composition and the electrochemical performance with R2 >0.9 and mean absolute errors < 0.2 with 5-fold cross-validation.

Combining High-Throughput Analysis and Data-Driven Electrochemistry for Advanced Characterization of Si-Ge-Sn Thin Films as Li-Ion Anodes

Aleksei SANIN

Abstract

The increasing demand for high energy density storage solutions, particularly in the electric vehicle industry, necessitates the development of advanced battery components. Conventional graphite anodes in lithium-ion batteries have limited energy density, so alternative anode materials are needed. This challenge requires not only materials research, but also a paradigm shift in the experimental materials science approach. This research addresses this challenge by employing a synergistic approach combining combinatorial thin-film synthesis and high-throughput characterization techniques with autonomous robotics and machine learning for the discovery and investigation of new energy storage materials.

In this study, a thin film of Si_xGe_ySn_z alloy (x = 0.15 – 0.63, y = 0.15 – 0.68, z = 0.10 – 0.64) with a gradient composition distribution was synthesized using combinatorial magnetron sputtering. This thin-film ternary material library was electrochemically characterized as a lithium-ion anode on a millimeter-scale using a three-electrode half-cell scanning droplet cell. The experimental protocol was driven by automated on-the-fly electrochemical analysis and Bayesian optimization with Gaussian process to find the chemical composition with the highest specific capacity and minimize the number of measurements. Comparative analysis revealed a significant improvement in Li-ion battery performance with the best performing Si-Ge-Sn anodes outperforming those with conventional graphite anodes, with increases in gravimetric and volumetric energy densities of over 30% and 60%, respectively. Advanced high-throughput µ-XRF and Raman spectroscopy provided valuable insights into the composition-structure-property relationships of the Si-Ge-Sn system. Additionally, the results of XPS and EIS studies were used to elucidate the discrepancies between theoretical and experimental reversible capacities of Si- and Ge-rich compounds.

This contribution advances energy storage research by demonstrating the effectiveness of integrating combinatorial synthesis, high-throughput characterization, and machine learning in the discovery of superior Si-Ge-Sn anodes, setting a new benchmark in thin-film battery research and combinatorial materials science.

A multi-technique thin-film deposition platform for combinatorial development of mixed-anion semiconductors

Andrea CROVETTO

Abstract

In this contribution, I will present a newly installed suite of thin-film deposition tools for combinatorial growth of metal phosphochalcogenide and chalconitride semiconductors. To my knowledge, thin-film synthesis of materials from these exotic mixed-anion chemistries has only been reported in four publications so far, and none of them deal with vacuum-based deposition. This lack of experimental studies is unfortunate because these material families have a remarkable degree of chemical diversity that could enable exciting applications in e.g., photovoltaics, battery technology, catalysis, and non-linear optics [1-4].

The film deposition platform consists of three glove-box integrated setups. The main combinatorial deposition setup is a reactive sputtering chamber with access to PH₃, H₂S, NH₃, N2 reactive gases, as well as to a sulfur/selenium cracking source. Both the reactive gases and the cracking source are set up with closed-loop process control to maintain the desired matrix of combinatorial film compositions on a single substrate. Two perpendicular gradients in film composition can be produced when depositing a quaternary compound. The first goes from sulfur- or selenium-rich to phosphorus- or nitrogen-rich. The second gradient goes from metal A rich to metal B rich. The deposition suite also includes a rapid thermal annealing furnace with access to the same reactive sources as the sputter chamber, as well as a separate evaporator for incorporating volatile metals without contaminating the main sputter chamber.

To demonstrate the relevance of this deposition platform, I will present experimental results on Cu3PS4 films, the first vacuum-deposited phosphosulfide films. Cu₃PS₄ turns out to be a very promising semiconductor for optoelectronic applications (such as photovoltaics and light-emitting diodes) due to its long carrier lifetimes. I will also present collaboration opportunities and important safety aspects of this deposition platform.

[1] Han and Ebert, ACS Applied Materials & Interfaces 13, 3836–3844 (2021).

[2] Kang et al., Nature 58, 785–789 (2020).

[3] Kibsgaard et al., Angewandte Chemie 53, 14433–14437 (2014).

[4] Kamaya et al., Nature Materials 10, 682–686 (2011).

Designing electrocatalysts for energy conversion reactions using high-throughput materials science

Hannah-Noa BARAD

Abstract

To mitigate climate change, the world is turning toward renewable and clean power sources. A very promising method to produce clean power is by electrochemical catalytic reactions, electrocatalysis, which can be powered by renewables for near-zero emissions. In electrocatalysis, the desired products are fuels and energy carriers, for instance, electrocatalytic reduction of CO2, which can lead to valuable molecules, such as CH4 and CH3OH. Another important reaction is water electrolysis, especially the sluggish oxygen evolution reaction (OER) anodic component, which can promote a H2 economy. The catalysts used by the industry today contain expensive and non-abundant elements such as Pt, Ir, and Ru. Thus, there is a pressing need to discover new, low-cost, and highly active catalysts that will yield process efficiencies comparable to those we have today for energy related electrocatalytic reactions. These reasons emphasize the motivation to accelerate the process of finding new materials with varying nanostructures and optimized functionality, by systematic exploration of several parameter spaces.

Here we present the progress in the development of catalysts using high-throughput physical vapor deposition techniques to form different types of material compositions and nanostructures as functional catalysts for electrocatalytic reactions, such as OER. To this end, we have used combinatorial materials synthesis of large material libraries prepared by sputtering and glancing angle deposition (GLAD). We then use custom-made high-throughput operando scanning systems to investigate the chemical, physical, morphological, and electrocatalytic properties of the materials libraries. For example, we developed a scanning electrochemical system that can go to predetermined positions on the library to investigate a specific composition activity. The insights we gain, show a dependence of catalytic activity on composition and nanostructuring, which the standard experimental techniques cannot achieve. As a result, these parameter spaces must be incorporated into the study of future catalysts. This can be done by high-throughput experimentation design, combined with machine learning tools, which will assist with appropriate pathways and ensure rational studies on new catalysts.

High throughput screening of (La,Sr)(Mn,Co,Fe)O₃ oxygen electrode materials for application in solid oxide fuel cells

Juande SIRVENT

Abstract

The use of accelerated research methodologies represents an emerging field towards the discovery of novel materials for energy. These approaches require the development of advanced material fabrication and characterization techniques. Employing thin film combinatorial methods for the simultaneous growth of complete material libraries has been proven helpful for obtaining self-sustained experimental datasets^1,2. In this context, investigating material libraries applied as oxygen electrodes in solid oxide cells (SOCs) is of great interest for energy sustainability. While SOCs are the most efficient technology for energy conversion, the materials utilized for the oxygen reaction are one of the main bottlenecks for their implementation in real systems. The need to extend the material space explored to full material libraries is of critical interest in this field.

In this contribution we have carried out a thorough study of a complete thin film (La,Sr)(Mn,Co,Fe)O₃ (LSMCF) material library fabricated by combinatorial pulsed laser deposition. Combinatorial deposition allows to fully characterize the material library under the same conditions, reducing experimental uncertainty associated to sample variability. The library was characterized by X-ray fluorescence spectroscopy, X-ray diffraction, Raman spectroscopy and spectroscopic ellipsometry for mapping the compositional, crystallographic, structural and electronic properties. The oxygen kinetics at 400 °C was probed by means of isotopic exchange depth profiling coupled with secondary ion mass spectrometry. The electrochemical performance was studied by impedance spectroscopy, resulting in mapping the activation energies and area specific resistances for the oxygen reduction reaction in the 675-750 °C temperature range. The screening carried out repsents an extended analysis covering the overall properties of the compositional family. Ultimately, coupling the obtained experimental results with machine learning modelling approaches is introduced as a promising strategy for gaining deeper knowledge of the LSMCF library.

References

(1) Usiskin, R. E.; Maruyama, S.; Kucharczyk, C. J.; Takeuchi, I.; Haile, S. M. Probing the Reaction Pathway in (La0.8Sr0.2)0.95MnO3+δ Using Libraries of Thin Film Microelectrodes. J. Mater. Chem. A 2015, 3 (38), 19330–19345. https://doi.org/10.1039/c5ta02428e.

(2) Saranya, A. M.; Morata, A.; Pla, D.; Burriel, M.; Chiabrera, F.; Garbayo, I.; Hornés, A.; Kilner, J. A.; Tarancón, A. Unveiling the Outstanding Oxygen Mass Transport Properties of Mn-Rich Perovskites in Grain Boundary-Dominated La0.8Sr0.2(Mn1- xCox)0.85O3±δ Nanostructures. Chem. Mater. 2018, 30 (16), 5621–5629. https://doi.org/10.1021/acs.chemmater.8b01771.

Machine learning approach of surface elastic chemical potential for morphological evolution of strained films

Luis MARTÍN ENCINAR

Abstract

The implementation of Deep learning for simulating surface dynamics during deposition emerges as a trustworthy and efficient tool to support and anticipate costly experiments. In strained thin films, the calculation of elastic energy term demands resorting to computationally intensive approaches, which remains the bottleneck when dealing with time evolutions. In this work, we explored the possibility of by-passing the explicit solution of the elastic problem by using a convolutional Neural Network (NN) to immediately predict the με profile associated to any surface profile. To this goal, we trained a NN on a dataset, composed of surface profiles and associated με, and showed that the NN reported an accurate prediction of με associated to any arbitrary surface geometry. Then, the NN is applied to the time integration of morphological evolutions in strained thin films, as shown by the performance of some cases (e.g. island growth and coarsening including substrate wetting effects), in which accuracy and numerical robustness are proven on large domains and long times. First, we use a dataset where με is computed based on a Green's function approximation. In light of using a more accurate and quantitative solution, the same approach has been tested on a training set based on Finite Element Method (FEM) calculations of the elastic field. In this case, NN predictions reported the same accuracy as conventional numerical methods and, more notably, a 10⁴ computational speed-up was achieved against FEM solver, which would allow to replicate scenarios that would otherwise be unfeasible. The proposed method could be extended or modified to include more complex phenomena (e.g. anisotropic surface energy density or the presence of plasticity-related objects such as dislocations).

Epsilon-near-zero metal oxide-based spectrally selective reflectors

Sraboni DEY

Abstract

Solar energy management, a key component of sustainable energy generation, is an area of wide topical interest wherein spectrally selective coatings form an important domain of research. Design and fabrication of durable, cost-effective coatings that are scalable in fabrication and compatible with diverse surfaces remain open challenges. Engineering spectral selectivity of surfaces is a favorable way to optimize the efficient utilization of solar energy, as discussed here in the context of developing a coating that spectrally displays an idealized step-function-like reflectivity i.e. complete absorption of light in the visible and high reflectance in the infrared, demarcated by a cut-in wavelength. Strategies for inducing such selectivity have broadly focused on assembling the right materials (semiconductors, metals, and dielectrics) in conducive form factors like multilayers or composites with structuring. Degenerately doped, wide band gap metal oxides indium tin oxide (ITO), doped CdO, etc. have been utilized to develop innovative new functionalities enabled by their large and controllable carrier density which allows tuning of their plasma frequency and thus the dielectric to metallic transition wavelength, known as the epsilon near zero (ENZ) wavelength (λ_ENZ). A niche application of ENZ materials and their plasmonic properties is evidenced in the development of spectrally selective coatings, where the optical property of a surface can be modified with the ability to selectively absorb light below a pre-defined wavelength λ_o and reflect at longer wavelengths. Studies have been conducted where various methods are employed to control the absorption and emission of light from surfaces including photonic crystals, optical metamaterials, multilayer thin films, and nanostructures.

Here we demonstrate the evolution of spectrally selective optical properties on ubiquitous substrates like stainless steel (SS) and glass from visible to IR utilizing ITO as the key ENZ material. A surface engineering has been executed through a coating of ITO/Cr/Cr₂O₃ of ~200 nm thickness on opaque stainless steel and transparent glass with an elementary periodic grating of ITO nanostructures over the coated substrate. Investigated from 400 – 4000 nm, the coated substrates show high average absorption (~90%) over the entire visible up to a particular cut-in wavelength λ_o beyond which the reflectivity becomes ~ 80% (emissivity ~20%) in IR. In other words, the reflection coefficient is like a “step function” at that particular wavelength λ_o (here ~1500 nm), which is a wide-angle feature realized between 0° to 60°. Importantly, this λ_o is tunable based on the selection of materials which has been showcased here through an ENZ material i.e. ITO in thin film as well as nanostructured form supported by the absorbing coating underneath. This straightforward design with high stability will find applications in thermal management.

A04_Transparent conductive films and smart coatings

Date: 27-05-2024

Time: 16:30-18:30

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Development of New Optoelectronic Thin Film Materials for Solar Cells

Monica MORALES-MASIS

Abstract

Photovoltaics (PV) is vital for the energy transition, and thin-film PV aims to provide cost-effective and environmentally friendly solutions that can complement established technologies such as crystalline-Si PV. However, the development of sustainable semiconductors for low-cost and efficient solar cells remains a challenge. In this presentation, we discuss the development, thin film growth and understanding of new semiconductor materials for solar cells, including photoactive light-absorbers and transparent electrodes with either n- or p-type conductivity.

The first part focuses on the development of transparent conducting materials (TCMs), from n-type transparent conducting oxides with tunable microstructure, high conductivity and transparency^1-3. These properties enabling good carrier extraction and minimum parasitic absorption losses in solar cells. Further, we present the experimental demonstration of transparent p-type conductive materials, a long-standing challenge in optoelectronics. By exploring halide and chalco-halide systems, semiconductors with a disperse valence band that exhibit improved hole mobility are achieved.⁴

Lastly, the presentation showcases our recent developments in pulsed laser deposition of hybrid organic-inorganic metal halide perovskites^5,6. We discuss how PLD allows for controlled growth, from polycrystalline to epitaxial films and photoactive phase stabilization. We demonstrate PLD of MAxFA1-xPbI3 thin films andintegration into solar cell devices with power conversion efficiencies above 17%.

In summary, the presentation highlights the significant contributions of controlled synthesis, material design, and the integration of new materials into proof-of-concept devices for the development of efficient and sustainable solar cell technologies.

References

[1] https://doi.org/10.1002/admt.202000856

[2] https://doi.org/10.1038/s43246-022-00260-4

[3] https://doi.org/10.1021/acsmaterialslett.3c01166

[4] https://doi.org/10.1016/j.matt.2023.10.003

[5] https://doi.org/10.1021/acs.chemmater.1c02054

[6] https://doi.org/10.1002/adfm.202300588

Optimizing the catalytic activity of the ternary metal chalcogenide ZnIn₂S₄ with hierarchical porosity

Marco SIGL

Abstract

Optimizing the activity of photocatalysts is of great interest towards realizing the transition to greener energy sources. Unlike photovoltaics, which converts sunlight into electrical energy, photocatalysts directly use sunlight for waste water treatment or the synthesis of so-called solar fuels and reactants for chemical reactions.^1,2 Heterogeneous catalysts offer advantages like easy handling and recyclability. However, such heterogeneous catalysts commonly show the problem of very low surface-area. Moreover, thin films show great potential to incorporate them into flow reactors. Therefore, we applied a single source precursor method using metal xanthates for the synthesis of the established photocatalyst zinc indium sulfide as structured thin films. Zinc indium sulfide has a tunable band gap from 2.0 to 2.8 eV, and all its polymorphs are reported to induce water splitting and dye degradation under visible light.³ We prepared hierarchically porous zinc indium sulfide thin films combining microsphere lithography^4,5 with the xanthate conversion to the metal sulfide.⁶ This provided macropores in the 300 nm regime and micropores around 1.6 nm, greatly enhancing the available surface area. Furthermore, we showed a 3.3 - fold increase in specific photocatalytic activity compared to the bulk films in the photodegradation of Rhodamine B. These results can help to optimize the photocatalytic activity of metal sulfide thin films by introducing multiscale porosity.

References

1 H. Qian, Z. Liu, Z. Guo, M. Ruan and J. Ma, J. Alloys Compd., 2020, 830, 154639.
2 T. Yan, Q. Yang, R. Feng, X. Ren, Y. Zhao, M. Sun, L. Yan and Q. Wei, Front. Environ. Sci. Eng., 2022, 16, 131.
3 T. Zhang, T. Wang, F. Meng, M. Yang and S. Kawi, J. Mater. Chem. C, 2022, 10, 5400–5424.
4 E. Vakalopoulou, T. Rath, F. G. Warchomicka, F. Carraro, P. Falcaro, H. Amenitsch and G. Trimmel, Mater. Adv., 2022, 3, 2884–2895.
5 J. Yu, Q. Yan and D. Shen, ACS Appl. Mater. Interfaces, 2010, 2, 1922–1926.
6 E. Vakalopoulo, T. Rath, M. Kräuter, A. Torvisco, R. C. Fischer, B. Kunert, R. Resel, H. Schröttner, A. M. Coclite, H. Amenitsch and Trimmel Gregor, ACS Appl. Nano Mater., 2022, 5, 1508–1520.

[Ni(ipki)2] as a novel ALD precursor for the synthesis of Nickel oxide films

Samuel PORCAR GARCÍA

Abstract

NiO_xthin films have potential applications in photovoltaic solar cells and batteries. In this work, we will present the deposition of NiO_x thin films via open-air Atmospheric-Pressure Spatial Atomic Layer Deposition (AP-SALD) using bis(4-(isopropylamino)pent-3en-2-onato)nickel(II) ([Ni(ⁱpki)₂]), a precursor so far not tested in any ALD approach. NiO_xthin films could be obtained at temperatures of only 170^ᵒC, while a temperature window was observed between 230^ᵒC and 250^ᵒC. The growth per cycle obtained in the ALD window was 0.023 nm/cycle. The optical properties of the film were also studied by UV-Vis, showing a high transmittance (> 97%) in the visible region with a band gap of 3.69 eV. Scanning electron microscopy (SEM) illustrated highly homogeneous films. The uniformity of the NiO_x film and its particle size was measured using a transmission electron microscope (TEM). XRD and RAMAN analysis confirms a cubic structure without secondary phases. Near edge X-ray absorption fine structure (XANES) spectrum showed the appearance of Ni-O bonds associated with NiO cubic structure. XPS confirms the presence of the NiO and NiOOH in the films. Our results show that [Ni(ⁱpki)₂] is a suitable precursor for the open-air, fast deposition of NiO_x thin films.

Near-Infrared emissivity tuning of VO-based thermochromic stacks with silver nanowire networks

Amaury BARET

Abstract

In the ever-increasingly important context of energy-efficient building technologies, the development of low-emissivity coatings is of particular significance. Among the noteworthy approaches contributing to this advancement are thermochromic materials, which allow for dynamic control of light transmission through reversible, thermally-induced transitions in optical properties, thereby enhancing energy efficiency in buildings. In particular, the unique properties of vanadium dioxide (VO₂) have captured considerable attention within the scientific community, primarily owing to its favorable characteristics such as a relatively low and easily adjustable transition temperature (68°C).
In this work, we present the design of a VO₂-based thermochromic stack that allows for optimal solar modulation (∆T_sol) and luminous transparency (T_lum) with tunable near-infrared emissivity. Given the recent advancements in the investigation of the low-emissivity properties of silver nanowire (Ag NW) networks, our investigation focuses on the development of a Ag NW-coated stack of SiO₂/TiO₂/VO₂/Ag/TiO₂/SiO₂/Glass that makes use of optical impedance matching (SiO₂and TiO₂) [1] and solar modulation enhancer (Ag) layers. The transfer-matrix approach is employed to model light propagation in this multilayered structure and to derive its associated optical properties. The optimal values of thicknesses for each layer are determined in order to maximize the thermochromic properties. This innovative design yields impressive simultaneous ∆T_sol and T_lumvalues, reaching up to 13.5% and 71%, respectively. Subsequently, the impact of the deposition of silver nanowire networks on the system’s emissivity is simulated based on the results and model of S. Hanauer et al. [2]. This simulation enables the deduction of the thermal emissivity (ε) of the stack and shows that it can easily be tuned by adjusting the density of the deposited network. The quantification of this emissivity’s tuning on the aforementionned thermochromic properties serves as a valuable reference for the design of low-emissivity coatings for energy-saving applications. Importantly, our findings reveal that the emissivity of the stack can be reduced by more than 50% by keeping T_lum> 50% and ∆T_solaround 10%. This insight underscores the potential for substantial emissivity reduction in the pursuit of energy-efficient technologies.

References
[1] C. Sol et al., ACS Appl. Mater. Interfaces, 2020, 12, 8140–8145.
[2] S. Hanauer et al., ACS Appl. Mater. Interfaces, 2021, 13, 21971–21978.

Carrier collision processes in TiO2 thin films for photocatalysis applications

Pierre GILLIOT

Abstract

Thin layers of TiO2 anatase are the base of industrial self-cleaning glazing products of Saint-Gobain, but a global picture of the charge carrier dynamics from their generation by UV sunlight absorption to the degradation of pollutants by photocatalysis is missing. In this work, the recombination dynamics of the photocarriers have been studied in TiO2 anatase by mean of time-resolved photoluminescence and pump-and-probe experiments, in order to figure out the carrier states and the processes governing their recombination after a femtosecond UV excitation. A rigorous signal analysis approach has been used to unveil that the carrier dynamics follows a single power law over a time range from ps to µs. The same behavior has been observed in thin layers deposited on glass as well as in single crystal anatase. Pump probe transmittance experiments cover the carrier dynamics up to room temperature where the luminescence signal is too weak and show the same power law at any temperature.

This demonstrates that a single common mechanism, dominated by collisions between carriers, governs the recombination. It is still efficient at very low carrier densities, longtime after the excitation. At low temperature, collisions occur between self-trapped excitons that get ionized into polarons with increasing temperatures. Collisions explain both the loss of carriers and their trapping at the surface. This step is essential to realize surface oxidoreduction reactions. A correlation has been finally observed between the sample microstructure and the local conductivity measured by c-AFM demonstrating the influence of the morphology on the charge carrier extraction.

Keywords: TiO2, Anatase, photocatalysis, carrier dynamics, time-resolved

Thin films of photoswitchable metal-organic frameworks: From light-induced chirality and molecular motors to photoactuation

Lars HEINKE

Abstract

The dynamic control of physical and chemical properties is one of the key challenges for functional, smart materials. An intriguing realization of materials with remote-controllable properties is based on photochromic molecules incorporated in thin films metal-organic frameworks (MOFs). Under the irradiation with light of different wavelengths, molecules like azobenzene, can undergo reversible trans-cis isomerizations. By preparing the MOF material in the form of well-defined films directly on the substrate (referred to as SURMOFs), using a layer-by-layer method, the properties of the photoresponsive material can be spectroscopically explored in detail.

For MOFs with azobenzene side groups, our work shows that such MOFs allow the dynamic control of the chirality by circularly polarized light (CPL).^[1] CPL causes chiral photoresolution of the initially optically inactive MOF, resulting in an optically active material. The chirality of the MOF is reversibly controlled by the handedness of CPL.

An array of oriented molecular motors, where the rotor moieties point into the pores, is realized by the incorporation of overcrowded alkene in the SURMOF films.^[2] The homogenous morphology of the thin SURMOF films enables the characterization of the activation energy for the light-powered molecular motor rotation by UV-vis spectroscopy. Moreover, we show that the uptake and diffusion properties of guest molecules in the motor-SURMOF are modified by switching between the different states during the motor rotation.

An oriented crystalline array of diarylethene (DAE)-based photoactuators, arranged in a way to yield an anisotropic response, was prepared by using the SURMOF approach on functionalized substrates.^[3] By the ring-open/-closed DAE photoisomerization, the extension of the molecular DAE linker changes, which multiplies to yield mesoscopic and anisotropic length changes in the SURMOF. Due to the special architecture and the substrate-bonding of the SURMOF, these length changes are transferred to the macroscopic scale, leading to the bending of a cantilever and performing work. This research shows the potential of assembling light-powered molecules into SURMOFs to yield photoactuators with a directed response, presenting a path to advanced actuators.

In the presentation, further aspects of photoswitchable MOF thin films will be discussed.

References:

^[1] A.B. Kanj, J. Bürck, N. Vankova, C. Li, D. Mutruc, A. Chandresh, S. Hecht, T. Heine, L. Heinke, J. Am. Chem. Soc., 143 (2021) 7059−7068.

^[2]Y. Jiang, W. Danowski, B.L. Feringa, L. Heinke, Angew. Chem. Int. Ed., 62 (2023) e202214202.

^[3] Y. Jiang, Y. Liu, S. Grosjean, V. Bon, P. Hodapp, A.B. Kanj, S. Kaskel, S. Bräse, C. Wöll, L. Heinke, Angew. Chem. Int. Ed., (2023) e202218052.

Self cleaning solar mirrors coatings: from laboratory to prototype tests on field

Anna CASTALDO

Abstract

Solar mirrors play a crucial role in concentrating sunlight for various applications, such as solar power generation and industrial processes [1]. However, the efficiency of these mirrors can be significantly compromised by the accumulation of dirt, dust, and other contaminants on their surfaces, leading to reduced reflectivity and hence overall performance of solar plants. For restoring solar mirrors optical performance, maintenance procedures require cleaning periodical operations, that use tons of water (precious resource in desertic areas) and impact on levelized cost of electric energy produced, LCOE [2]. To address this challenge, the development of advanced surface coatings, known as self-cleaning coatings, has gained prominence in the field of solar mirrors technology [3]. Self-cleaning coatings are specifically designed to mitigate the negative effects of soiling on solar mirrors, ensuring a reduction of water requirements in cleaning procedures savings of O&M costs and sustained energy capture over time. As a result, solar mirrors coated with such materials exhibit enhanced durability, improved cleaning efficiency and prolonged operational lifespans.

This work aims to explore the significance of self-cleaning coatings in the context of solar mirrors, highlighting their role in overcoming the challenges associated with environmental factors that can compromise the performance of solar energy systems. By addressing the issue of soiling, new materials contribute to the overall efficiency and viability of solar mirror applications, making them a key component in the pursuit of sustainable and clean energy solutions. Starting from the research of different solutions for modifying wetting properties of solar mirrors layer exposed to the pollution, a library of new coatings has been developed on a lab scale, tailoring chemical physical properties in function of mirrors architectures, type of soiling, geographical positioning of solar field and desired costs/performance ratio.

A low cost and robust process for scaling up research results has been proposed as innovative method for covering real solar mirrors with a self-cleaning material based on auxetic aluminium nitride [4], that is photocatalytic, transparent in the full solar range and can be applied on back surface and front surface solar mirrors, replacing the alumina covering layer. Preliminary outdoor testing results of self-cleaning solar mirrors positioned in the demonstrative CSP plant ENEASHIP located in Casaccia (Rome) ENEA research centre will be shown.

[1] SolarPACES, CSP-how it works, 2016.

[2] T. Sarver et al, Renew. Sustain.Energy Rev. 22, (2013) 698-733.

[3] Siafiq et al Sol. Energy 162, (2018) 597-619.

[4] Castaldo et al, Energies 14(20), (2021) 6668; https://doi.org/10.3390/en14206668

A05_Functional Oxide Thin films

Date: 28-05-2024

Time: 08:45-10:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Thermochromism of magnetron sputtered VO2 thin film for smart windows applications

Eduard LLORENS BALADA

Abstract

Transition metal oxides have gained significant interest due to their optoelectronic properties. Among them, VO2 possesses a metal-to-insulator or insulator-to-metal transition temperature (MIT) at around 68°C. In the insulator state, VO2 manifests a monoclinic structure that shows high resistance and high transmittance at around 2000nm wavelength, while at the metallic state, the monoclinic structure distorts to rutile implying a decay of its resistance and transmittance at the near infrared spectrum. This thermochromic property motivates possible applications for smart windows.

In this study thin films were deposited by radio-frequency (RF) magnetron sputtering from a VO2 target on top of fused silica substrates to evaluate the effect of substrate temperature and oxygen gas flow on the MIT properties. Furthermore, the MIT formation was correlated with optoelectronic (transmittance, resistivity) and analytical properties (composition, crystallinity).

When used for smart windows, the MIT layer should be combined with a transparent conductive oxide (TCO). For this reason, the VO2 target was also used to deposit a thermochemically active layer on top of Al-doped ZnO (AZO). This endeavor revealed significant challenges as the VO2/AZO structure exhibited a flattening or even complete disappearance of the MIT. However, we are reporting that post-annealing or proper tuning of the sputtering parameters can be used to recover or even improve the thermochromic performance of the VO2/AZO thermochromic configuration.

XPS and XRD characterizations were performed for oxidation state, and crystalline structure analysis, respectively. The results suggest that a high content of V4+ oxidation state, and fine tuning of the oxygen flow are a must to avoid the formation of other vanadium oxide compounds that contribute negatively to the thermochromic performance. Moreover, crystalline VO2 is required to reveal the thermochromic effect. The use of an AZO seed layer promotes the formation of (020) oriented phase in detriment of the (011) orientation observed on the VO2 deposited on fused silica. The MIT of VO2/AZO structure was characterized optically as to avoid distortions of electrical measurements by Joule effect. When using AZO as a seed layer, either the deposition time must be reduced to reduce stress improving the MIT, or an annealing process must be carried out, to release stress and enhance the thermochromic effect. Finally, we provide alternatives routes for possible improvements of the VO2/AZO structure to support the possible use for the fabrication of smart windows.

High-Throughput and Machine Learning Strategies for the Optimization of Optoelectronic Thin-Film Devices

Maximilian WOLF

Abstract

The optimization of optoelectronic thin-film devices poses a difficult challenge, especially when the preparation method consists of multiple parameters which influence the resulting properties. Even if the individual materials and processes are well established, their combination may not be straight-forward and requires fine-tuning of the process parameters. In this case, combinatorial and high-throughput approaches are advantageous since they allow for fast screening of the full-factorial parameter space. Further acceleration can be achieved through the utilization of machine learning methods which are able to uncover complex relations.

In a previous work, we demonstrated the performance of p-type Cu₂O layers in photovoltaic devices which show high rectification and an open circuit voltage of 940 mV, thus implicating the applicability as hole-transport layers. The heterojunctions are fabricated on indium-tin-oxide (ITO)-coated glass by stacking ultrasonic spray pyrolyzed (USP) Ga₂O₃ with reactively sputtered Cu₂O [1]. The latter material is also achieved in a water-based USP process [2], paving the way to all-sprayed photovoltaic devices. Additionally, the USP is well-suited to create combinatorial composition gradients [3], enabling high-throughput screening of dopant inclusions to further optimize the material’s performance. To this end, a platform for combinatorial device characterization is developed, designed to measure a matrix of 8x8 individual solar cells on a single sample of 25x25 mm² size.

However, the transition from established processes introduces several challenges. Foremost, the Ga₂O₃ layer changes the reaction kinetics of the Cu₂O USP deposition, yielding a mixture of copper oxide phases. This results in impeded device performance and reduced yield of functioning cells on the 8x8 matrix. In order to obtain the USP process parameters which lead to pure Cu₂O and defect-free interfaces, a data-driven approach is followed. To this end, Latin hypercube sampling [4] is employed to efficiently represent the multidimensional parameter space by only 12 deposition experiments. This preliminary data is used to obtain surrogate models, based on Gaussian processes [5], which are subjected to Bayesian optimization [6]. Following this approach, the USP process is optimized in terms of precursor concentration, flow rate, temperature, nozzle to substrate distance, nozzle speed, and number of deposition cycles, to obtain all-sprayed Cu₂O-Ga₂O₃ heterojunctions.

[1] Dimopoulos T., et al. “Heterojunction devices fabricated from sprayed n-type Ga2O3, combined with sputtered p-type NiO and Cu2O.” Nanomaterials (2024, Accepted Manuscript).
[2] https://doi.org/10.1002/cnma.202000006
[3] https://doi.org/10.1039/D3MA00136A
[4] https://doi.org/10.1080/00401706.2000.10485979
[5] Gramacy, Robert B. Surrogates. “Gaussian process modeling, design, and optimization for the applied sciences.” CRC press (2020).
[6] https://doi.org/10.48550/arXiv.1807.02811

Visible Light-Responsive Advanced Ternary Composite for Efficient Photocatalytic Degradation of Endocrine Disrupting Chemical in Aqueous Environment

Manisha SAIN

Abstract

Silicon epitaxy assisted by solution chemistry: A platform for integrated oxide devices

A. Carretero-Genevrier

Institut d´Électronique et des Systèmes (IES) UMR 5214, CNRS – Université de Montpellier

Oxides are robust materials that can exhibit outstanding electric, magnetic, optical, mechanical, and thermic properties. The control of their atomic structure, crystallographic orientation, crystallinity, chemical composition and dimensions make possible the synthesis of oxide-based materials with enhanced physical properties. In this light, integration of metal-oxide thin films on silicon can be used to produce highly efficient micro and nano-devices due to their physical and chemical properties. As a consequence, metal oxides thin films and nanostructures are considered as an important material family to diversify the functionalities of silicon technology in a More than Moore vision. For instance, it is expected that the epitaxial integration of piezoelectric oxide material on silicon in the form of thin films from few nanometers to several tens of microns is the most suitable approach towards the fabrication of a high quality piezoelectric micromachined transducers and actuators. However, the grow of piezoelectric oxides on silicon is challenging because the oxygen partial pressure and silicon temperature must be controlled to avoid the formation of amorphous SiO2 or silicate layers at the first stage of growth which might inhibit epitaxy. Therefore, most of piezoelectric materials are only available as bulk crystals and currently no effective and cost-effective processes for their deposition in single crystal thin film form on silicon exist at industrial level. In this work, I will present different examples of successful On-chip direct integration of functional oxides thin films and nanostructures by using exclusively chemical solution deposition technologies i.e.: (i) nanostructured epitaxial α-quartz thin films [1], (ii) novel 1D epitaxial ferroelectric SrMn8O16 hollandite oxide thin films [2], (iii) nanostructured and dense epitaxial lead-free perovskite oxide heterostructures [3], and (iv) an unprecedented epitaxial integration of ZnO on silicon. All these functional oxides are piezoelectric materials, abundant, cheap and harmless that are currently used in different projects to produce scalable and cost-efficient highly sensitive sensors [4], ultra-efficient catalyst or micro energy harvesters among others applications. Some of these developed devices application will be detailed and discussed along this talk.

All these works have received funding from the European Research Council (ERC) program under grants agreements No 803004 (SENSiSOFT).

[1] ACS Appl. Mater. Interfaces 2020, 12, 4, 4732–4740

[2] Nanoscale, 2021, 13, 9615

[3] Small 2017, 1701614

[4] Adv. Mater. Technol. 2021, 6, 2000831

A06_Functional Oxide Thin films

Date: 28-05-2024

Time: 10:30-12:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Chemical synthesis of CoFe2O4-BiFeO3 multiferroic nanocomposites for energy harvesting

Karla MENA AGUILAR

Abstract

Energy harvesters play a crucial role in addressing the unsustainable energy demands of digital devices and thus contribute to the digital and ecological transitions aimed by the European Union. Recently, multi-energy source harvesters have gained special interest, as they could more effectively meet the desired power requirements. This is particularly useful when one of the sources is not continuously available, such as solar light. An intriguing and unexplored approach involves harvesting both low-frequency magnetic fields from ambient magnetic noise and solar energy using a single system. A potentially attractive candidate for this purpose could be a nanocomposite combining lead-free multiferroic and photoabsorber perovskite BiFeO₃ (BFO), and magnetostrictive spinel CoFe₂O₄(CFO). In this configuration, the magnetic-field-induced strain over the CFO is transferred to the piezoelectric BFO, generating an electric polarization. To maximize this magnetoelectric coupling, the structure, strain state, and architecture of the composites need to be optimized.

In this work, we approach this challenge by preparing the BFO-CFO nanocomposite using two different architectures, a matrix-embedded nanoparticle system (0-3) and a nano-laminates system (2-2). The composites are synthesized using cost-effective methods, namely Atomic Layer Deposition and Chemical Solution Deposition. The chemical synthesis of individual oxides is revised and optimized to ensure the high quality of the resulting composites. Nano-embossing techniques are applied to enhance structural control over the architectures. Thin films are deposited on SrTiO₃ (001) substrates to induce epitaxial growth. For physical characterization, samples utilize La_0.7Sr_0.3MnO₃ (LSMO) as bottom electrode. We investigate the influence of thickness and annealing temperature on both structural and functional properties. Measurements through Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) reveal a homogeneous morphology in the composites. X-ray diffraction measurements confirm that we obtained crystalline BFO-CFO composites and provide information on epitaxial growth, film thickness, and strain analysis. The first results show a trend where higher CFO phase ratios correlate to higher magnetization values. These initial findings establish a reliable platform for further exploration into the ferroelectric and photovoltaic response of these strain-engineered composites, aiming to utilize them effectively as multi-source energy harvesters.

Keywords: chemical methods, thin films, nanostructures, complex oxides, energy harvesting

Advanced ZnO-based Thin Films Exhibiting High Photoelectrochemical Activity

Ladislav KAVAN

Abstract

Thin films (35-120 nm) from n-ZnO (wurtzite) were prepared on four different substrates, i.e., FTO, quartz, Si, and Si/SiO₂ by pulsed reactive magnetron sputtering combined with radio frequency electron cyclotron wave resonance plasma. For comparison, the ZnO films were also grown by traditional spray pyrolysis. Their characterization was referenced, if relevant, to the (0001)- and (000-1)-oriented ZnO single crystal. Thin films were composed of crystallites (12 to 26 nm in size), indicating that they consisted of about 2-10 monolayers of single nanocrystallites. They were sintered into a virtually non-porous compact body exhibiting excellent rectifying function on the electrochemical interfaces. On all types of substrates, spray-pyrolyzed films were more anisotropic. The Si substrate is prone to air oxidation during spray pyrolysis. Photo/electrochemical studies demonstrate limitations of (i) the classical Gärtner model of carrier dynamics in ZnO photoanodes and (ii) the Mott-Schottky analysis of its electronic structure. Specifically, the analysis by electrochemical impedance spectroscopy in aqueous and aprotic media overestimates the donor concentrations, compared to values found by Hall-effect measurements. The experimentally determined donor densities are sometimes even larger than the effective density of conduction-band states in ZnO (wurtzite), which would erroneously point at degenerate semiconductors. A similar paradox follows from many earlier studies of ZnO but is usually ignored by the authors. The work functions of ZnO/air interfaces specifically distinguish the effects of calcination and UV-excitation, which were attributed to the erasing of oxygen vacancies near the surface. The work functions at the electrochemical interface specifically address the growth protocol of the ZnO electrodes, but not the effects of crystallinity and calcination. Very high photocurrents of water oxidation were observed by linear sweep voltammetry under chopped UV light, but exclusively on the virgin films. They were by two orders of magnitude larger than the photocurrents on TiO₂ or SnO₂ thin films tested under comparable conditions. However, the photocurrents rapidly attenuated (already during the first voltage scan), and the drop progressed in repeated measurements. We are not aware of reporting this effect in any of the earlier ZnO photoelectrochemical studies, though several authors noted an instability of the ZnO photoelectrode. This spectacular phenomenon is discussed in terms of changes in work function by UV light. To prevent photocorrosion, various passivation layers were grown by ALD from SnO₂ and TiO₂ (crystalline, quasi-amorphous, Li-doped).

Lead-free perovskite oxides: towards an opto-electronic based on abundant elements and low temperature synthesis

Ilhem ELGARGOURI

Abstract

The depletion of natural resources today necessitates a reevaluation of technological development, considering both material abundance and energy-efficient processes while maintaining device efficiency. This research presents a comprehensive investigation into the design and synthesis of advanced thin films materials for improved optoelectronic applications. By exploring the unique properties of lead-free perovskites oxides, we aimed at engineering materials with enhanced electrical conductivity, stability, and optical properties.

For this work, we chose two types of perovskites oxides: SrSnO₃ and LaVO₃. The reason behind this choice is the combination of abundancy, non-toxicity and low-cost production of these materials along with the tunable bandgap, the stability and durability.

In this study, we will detail the tailored synthesis process with sol-gel method using different percentages of doping. We discuss the systematic characterization of the resulting thin films through various analytical tools.

Nontoxic, relatively cheap precursors, and solvents were used without generating waste materials. The viscosities were in the range of 50-60 mPa·s. The resulting resins were spin-coated on Silicon and Quartz. The wet films were then annealed at 673 K to remove organic material and crystallized at 1173 K for 1h in air. Using scanning electron microscopy, the film thickness was found to be around 200nm with a highly uniform and homogeneous surface, X-ray diffraction confirmed the perovskite phase with an intense peak at 32°, and optical measurements proved the transparency of 80% in the visible range with an absorption in the UV range around 300nm.

The results reveal a clear correlation between the synthesis parameters and the optoelectronic performance of the materials, demonstrating the feasibility of optimizing these materials characteristics through precise control of the synthesis process.

The objective of this work is the realization of optoelectronic components (pn junction) based on doped perovskite oxide semiconductors (SrSnO₃: Sb@SrSnO₃: Al on ITO and LaVO₃) synthesized using an ecofriendly environmental synthesis (sol-gel process). Application as light absorbers or barrier layers in highly efficient solar cells are foreseen. Other applications are also possible (e.g., LEDs).

This work contributes to the ongoing efforts to develop sustainable and efficient materials for optoelectronic devices and underscores the pivotal role of advanced material synthesis techniques in achieving this goal.

Keywords: thin films, perovskites oxides, sol-gel synthesis, optoelectronic device, sustainable development.

Understanding the morphology of molecular self-assembled monolayers on iron oxide nanoparticles to clean water from hormones

Lukas MÜLLER

Abstract

Access to clean water is recognized as a human right by the United Nations. However, anthropogenic molecular pollutants, like hormones are present in our ground water and find their way into drinking water due to careless disposal and insufficient remediation. Already at the trace concentration level such compounds have been shown to have severe effects on aquatic flora and fauna, but also to us humans, especially children. Still consequences of long term exposure are often unknown.

Therefore, it exists a big demand in affordable and efficient removal of such organic contaminants from water. Having this in mind, we are en route to develop a promising concept to solve this problem. Superparamagnetic iron oxide nanoparticles (SPIONs) are surface-functionalized with thin films composed of self-assembled monolayers (SAMs). These consist of permanently binding phosphonic acid derivates to address certain interaction motifs of selected hormones. Such particles attract the pollutants and can be easily remediated from water by an external magnetic field due to the magnetic moment of its cores. Basing on previous successful remediation of the herbicide glyphosate, micro- and nanoplastics as well as crude oil via single major interaction motifs (covalent binding – electrostatic interactions – hydrophobic interaction respectively), we pursue the next logical step. We establish the interaction of rationally designed binary SAMs on SPIONs with dedicated trace organic pollutants, i. e. various estrogen derivates. Therefore, we envision sorbent systems that are not only thermodynamically attractive for the pollutants of choice by combination of multiple interaction motifs, but also present suitably-sized cavities in the binary SAM. To characterize these systems, we approach the problem from several angles. Via 2D and 0D model system we combine state-of-the-art analytical techniques (e.g. grazing incidence wide angle X-ray scattering (GIWAXS) or solid state magic angle spinning 2D nuclear magnetic resonance (NMR)) with small angle neutron scattering (SANS) on the SPIONs backed up with molecular dynamics simulations. This approach benefits from synergy of experimental materials science and analytical chemistry as well as simulations to tailor nanoparticulate water cleaning agents.

Chemical Vapour Deposition of Bismuth Oxyiodide Thin Films for Energy Conversion Applications

Robert HOYE

Abstract

The past decade has witnessed the rapid increase in popularity of bismuth-based semiconductors as potential nontoxic alternatives to lead-halide perovskites that may replicate its defect tolerance [1]. Such materials are referred to as ‘perovskite-inspired’ because they are identified on the basis of having a similar electronic structure as lead-halide perovskites at the band-extrema, which is believed to be important for achieving defect tolerance. One such material we have worked on is BiOI, which we have shown to be air-stable without encapsulation for hundreds of days [2]. This talk discusses our development of this material for optoelectronics, focussing on how the morphology and preferred orientation of thin films of this material are controllable through chemical vapour deposition. We discuss initial demonstrations in solar cells (with EQEs reaching up to 80% at 450 nm wavelength) [2], through to the discovery of its potential for indoor energy harvesting [3], and applications for oxide artificial leaves [4]. Notably, we achieved oxide-based photoelectrochemical tandems (using BiOI and BiVO4 as the active layers) capable of bias-free syngas production [4]. We discuss the important role carrier-phonon coupling plays in this material, how it influences non-radiative recombination and charge-carrier transport, and how these effects may be overcome [5].

[1] Ganose, Scanlon, Walsh, Hoye,* Nat. Commun., 2022, 13, 4715.

[2] Hoye,* et al. Adv. Mater., 2017, 29, 1702176.

[3] Peng, Huq, Mei, ..., Hoye,* Pecunia,* Adv. Energy Mater., 2020, 11, 2002761.

[4] Andrei, Jagt, … Hoye,* Reisner,* Nat. Mater., 2022, 21, 864

[5] Jagt, Bravić, …, Hoye,* Nat. Commun., 2023, 14, 2452

A07_Functional Oxide Thin films

Date: 28-05-2024

Time: 13:45-16:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Evaluation of Zn(DMP)₂ as an Alternative Non-Pyrophoric ZnO Precursor for Open-Air SALD for Silver Nanowire Stability Enhancement

Liam JOHNSTON

Abstract

Although diethyl zinc (DEZ) is widely accepted as an industry standard for the ALD of ZnO,¹ its highly pyrophoric nature makes it challenging to use in an open-air setting. In this context, recent developments in precursor engineering have suggested bis-(N,N-dimethylaminopropyl) zinc [Zn(DMP)₂] could be a performant non-pyrophoric alternative to DEZ when thin-film properties, process parameters, and safety are considered.^2–4

Our approach relied on spatial ALD (SALD) specifically carried out in an open-air setting using a close proximity manifold injection head,⁵ which sequentially exposed different parts of the substrate to the different precursors resulting in a ZnO thin-film with high purity, conformality, crystallinity, and with a precisely controlled thickness.

The work constitutes the first vacuum-free instance of Zn(DMP)₂ being used to produce ZnO thin-films on a centimetric scale, and builds upon previous works using Zn(DMP)₂ for millimetre-scale patterning and ALD.^2–4 Using a wide array of techniques such as GI-XRD, XRR, SEM, TEM, XPS, we report process parameters leading to an ALD window from 140 to at least 180 °C with growth per cycle (GPC) values around 0.7 Å/cycle which, combined with the shorter cycle times needed, resulted in a faster growth rate (18.4 nm/min) than conventional ZnO ALD using DEZ.⁶

In addition, silver nanowire (AgNW) networks were coated with a thin shell of ZnO to improve their electrical stability which was compared with previous works involving DEZ⁷ in order to prove conformality and functionality of the coating. A modified ALD process at 150 °C was shown to yield conformal shells around AgNW networks with growth rates around 0.4 Å/cycle, which provided a similar electrical stability improvement as shells prepared using DEZ.

These AgNW networks may be used as transparent conductive nanocomposites,⁷ while bulk doping of these films with Al or Ga can serve for indium-free transparent conductive oxides.¹ Though most films exhibited a-axis growth, conformal thin-films with textured c-axis growth could be obtained at 260 °C, further allowing for piezoelectric applications.⁸

References:

1. Macco, B. & Kessels, W. M. M. (Erwin). Appl. Phys. Rev. 9, 041313 (2022).

2. Mai, L. et al. Small 16, 1907506 (2020).

3. Philip, A., Mai, L., Ghiyasi, R., Devi, A. & Karppinen, M. Dalton Trans. 51, 14508–14516 (2022).

4. Stefanovic, S. et al. Small 19, 2301774. (2023)

5. Muñoz-Rojas, D. & MacManus-Driscoll, J. Mater Horiz 1, 314–320 (2014).

6. Lujala, V., Skarp, J., Tammenmaa, M. & Suntola, T. Appl. Surf. Sci. 82–83, 34–40 (1994).

7. Khan, A. et al. ACS Appl. Mater. Interfaces 10, 19208–19217 (2018).

8. Consonni, V. & Lord, A. M. Nano Energy 83, 105789 (2021).

Advancing Electrochromic Technology: Deposition of Flexible Niobium Oxide Thin Films for Cutting-Edge Applications

Alice MARIA DA COSTA MARCIEL TRABULO

Abstract

Electrochromic technology has undergone significant advancements in recent years, transitioning from rigid to flexible devices. However, the fabrication of flexible electrochromic devices remains challenging, primarily due to the intricate interplay between growth techniques, the physical properties of substrates, and electrodes (Marciel et al., 2021; Wang et al., 2021).

In the current study, niobium oxide (NbO_x) thin films were grown on flexible ITO-coated PET substrates. The reactive DC magnetron sputtering technique was employed to prepare the NbO_x thin films, with variations in the O₂/Ar flow rate ratio and growth time, resulting in thickness ranging from 51 to 88 nm.

A structural transition was observed based on the O₂/Ar flow rate ratio, shifting from a crystalline to an amorphous nature. Additionally, there was a transformation from a nontransparent, metallic-like conductivity appearance to transparent and dielectric behavior. Despite predominantly exhibiting a compact/dense and unremarkable morphology on both top view and cross-section, a subtle texturing was evident on the top view of samples with extended growth time.

The thin film presented a surface roughness (sq) of about 4 nanometers with a maximum optical transmission in the visible range is 81%.

The electrochromic response of the NbO_x thin film deposited on ITO-coated PET substrate demonstrated a maximum coloration efficiency of 30 cm²C^-1 and a reversibility of 96%. The mechanical performance of the thin films grown on flexible substrates was assessed through automated bending tests, suggesting that electrical resistance increases while varying the bending radius.

Marciel, A., Graça, M., Bastos, A., Pereira, L., Kumar, J. S., Borges, J., Vaz, F., Peres, M., Magalhães, S., Lorenz, K., & Silva, R. (2021). Molybdenum oxide thin films grown on flexible ito-coated pet substrates. Materials, 14(4), 1–20. https://doi.org/10.3390/ma14040821

Wang, J. L., Sheng, S. Z., He, Z., Wang, R., Pan, Z., Zhao, H. Y., Liu, J. W., & Yu, S. H. (2021). Self-Powered Flexible Electrochromic Smart Window. Nano Letters, 21(23), 9976–9982. https://doi.org/10.1021/acs.nanolett.1c03438

Modelling the atomic layer deposition process of ferroelectric oxide perovskites

Ji LIU

Abstract

Atomic layer deposition (ALD) is widely used in microelectronics and semiconductor industry to deposit metal and its oxide and nitride thin films as part of device fabrication in nano- or subnano-dimensions. The key advantages of ALD are the conformality and precise thickness control at the atomic scale, which are difficult for physical or traditional chemical vapor deposition methods. The atomic scale understanding of ALD is vital and essential to design and optimize the deposition process, where density functional theory (DFT) calculations play an important role in providing detailed reaction mechanism, theoretical screening of suitable precursors and estimated growth-per-cycle (GPC).

In this study, we present our DFT results of a recently funded Horizon Europe project to apply ALD techniques to enable low-temperature integration of epitaxial functional complex oxides. This presentation will focus on the chemistry promoting the direct low-temperature deposition of orientated crystalline films BaTiO3 (BTO). We first show the process of selecting reactive precursors including Ba(acac)2 and Ba(CpiPr3)2 and co-reactants including water (H2O) and ozone (O3). These gas-phase precursors are screened using DFT calculations to identify plausible ligand elimination pathways. They are then placed on top of metal oxides to study the ligand elimination mechanism for ALD process. The effect of metal oxide terminations, for example O-termination and metal atom termination, is additionally evaluated in detail.

Our results of modeling the reactions of ALD can offer new low temperature direct epitaxial deposition techniques for BTO.

Sustainable low-temperature solution deposition methods for the integration of ferroelectric oxide thin films into flexible devices

Maria Lourdes CALZADA

Abstract

Advanced materials’ developments are indispensable today because they can provide game-changing solutions driving the twin green and digital transformation addressed in the priority policies for Europe. Ferroelectric oxide materials are optimum candidates to achieve these demands. They can be integrated in electronic systems, operating with multiple functions in a single device. In addition, they can harvest energy from multiple sources (mechanical, thermal or solar). Among ferroelectrics, lead-free compositions based on the BiFeO₃ perovskite are promising to address these applications. Even more, smart, cheap, lightweight, autonomous and mobile devices are required in this scenario, which necessary lead to the deposition of the film on flexible substrates. These substrates do not withstand the high temperatures required for the crystallization of the ferroelectric oxide. Therefore, it is mandatory the investigation of new low-temperature thin film deposition methods. In this regard, Chemical Solution Deposition (CSD) is well positioned to integrate metal oxide thin films with flexible substrates, as a large-area, low-cost, high throughput fabrication technique.

This presentation shows disruptive solution strategies developed in our group for the low-temperature fabrication of ferroelectric BiFeO₃-based thin films on different types of flexible substrates (plastic, metal foil or mica). Novel solution deposition approaches based on the molecular design of the metal complexes synthesized in solution, the use of UV-light as an alternative energy source to the thermal energy, or the self-seeding of the precursor solutions by sonochemistry or solvent-engineering, will be discussed here. Planar or interdigital capacitors have been fabricated with these flexible materials to evaluate their functional properties and determine their potential use in electronic devices (sensors, memories and harvesters).

Funded by the Spanish Projects PID2022-136790OB-I00/AEI/10.13039/501100011033, CNS2022-135743 and TED2021-130871B-C21/AEI/10.13039/501100011033/Unión Europea Next-Generation EU/PRTR. M.E. acknowledges financial support from Spanish “FPU” Programme (FPU22/01677).

Cost- and resource-efficient deposition of Gadolinium doped Ceria films by ultrasonic spray pyrolysis for high-temperature electrolysis

Niklas MAYR

Abstract

While solid oxide electrolyser cells (SOEC) are a proven technology for the co-electrolysis of water and carbon dioxide, their limited lifetime and high cost have prevented their large-scale application to date. [1] By utilizing thin film deposition methods, both issues can be addressed: functional layers of Gadolinium-doped Ceria (GDC) substantially extend the SOEC lifetime by preventing the formation of non-ion-conductive, secondary phases between the oxygen electrode and the electrolyte. [2] Simultaneously, the high cost related to the materials scarcity can be proportionally reduced by depositing thinner layers.

A cost-effective, environmentally friendly, and scalable deposition method is ultrasonic spray pyrolysis (USP). [3] For the optimization of the GDC films by USP, the impact of the relevant of process parameters was investigated, following a thorough central composite design of experiments (DoE). [4] To quantify the deposition quality, the whole sample surface was recorded using light microscopy and at the nano-regime scanning electron microscopy (SEM). Thereby all possible defects ranging from the mm-scale to the nano-scale can be identified, with the help of image segmentation neural networks. [5]

With that optimised recipe, homogenous crystalline GDC films, with structural integrity, a thickness of ~250 nm and practically no defects (<0.1 % of the area coated) can be deposited on different substrates, including yttria-stabilized zirconia solid electrolytes. To conclude we demonstrate how image segmentation neural networks enable the application of statistical design of experiments methods enable and thereby substantially accelerate the development of USP recipes. The next steps are the development and optimisation of a USP recipe for the deposition of the LSCF-electrode, with which full cells will be manufactured and electrochemically characterised.

[1] C. Graves, T. L. Skafte, S. H. Jensen, Co2 electrolysis, in: High-Temperature Electrolysis: From fundamentals to applications, IOP Publishing Bristol, UK, 2023, pp. 16–1.

[2] A. Mitterdorfer, L. Gauckler, La2zr2o7 formation and oxygen reduction kinetics of the la0. 85sr0. 15mnyo3, o2 (g)— ysz system, Solid State Ionics 111 (3-4) (1998) 185–218.

[3] D. Perednis, Thin film deposition by spray pyrolysis and the application in solid oxide fuel cells, Ph.D. thesis, ETH Zurich (2003)

[4] K. Siebertz, T. Hochkirchen, D. van Bebber, Statistische versuchsplanung, Springer, 2010.

[5] O. Ronneberger, P. Fischer, T. Brox, U-net: Convolutional networks for biomedical image segmentation, in: Medical Image Computing and Computer-Assisted Intervention–MICCAI 2015: 18th International Conference, Munich, Germany, October 5-9, 2015, Proceedings, Part III 18, Springer, 2015, pp. 234–241.

Ultrafast Sodium Storage of Copper Sulfide and Phosphorus Composite as High-Performance Anode for Sodium-Ion Batteries

Jong Min YUK

Abstract

The electrocaloric effect (ECE) is a promising clean and efficient alternative to the vapor-compression technology for refrigeration applications near room temperature (RT) [1]. Electrocaloric (EC) materials generate an adiabatic temperature change (ΔT) upon varying the electric (E) field, which maximizes at the Curie temperature (T_C) of ferroelectric transitions [2]. Advantageous over their well-known magnetocaloric counterparts due to the ease of application of E fields, EC materials have been in the spotlight for little more than a decade [1], following the observation of a giant ECE (ΔT ⁓ 12 K) in a PbZr_0.95Ti_0.05O₃ thin film [3]. Ferroelectric thin films promote strong EC responses since they withstand higher E fields, however, the largest values have been obtained in Pb-based systems. Lead-free EC materials in thin-film form are thus sought after to implement sustainable cooling solutions.

Aurivillius phases, composed by n perovskite-like layers (A_n-1B_nO_3n+1)^2- sandwiched between bismuth oxide layers (Bi₂O₂)²⁺ along the c-axis, are promising EC materials because of their high dielectric strength and endurance upon E field cycling [4]. Recently, we have studied the EC properties of bulk lead-free compositions of five-layer Sr₂Bi₄Ti₅O₁₈ (SBTO) with T_C ~ 560 K. By applying La/Nb codoping, the ECE is successfully tuned near RT, reaching ΔT ~ 0.3 K at 355 K for the optimum composition [5]. To enhance the ECE of these Aurivillius phases, we have tackled their investigation in thin film form. High-quality epitaxial thin films of SBTO with thickness in the range 75-200 nm, have been grown by pulsed laser deposition on (001)-oriented SrTiO₃ single crystals. Targets with 10 and 20 wt% excess of the Bi₂O₃ precursor were used to compensate for bismuth losses due to its strong volatility, and several deposition temperatures were examined (650 - 850 ºC). The X-ray diffractograms confirm that the films are single-phase and c-axis-oriented with high crystalline quality. Optimal growth conditions have been determined to yield the pure n = 5 periodicity. Atomic force microscopy characterization confirms a low roughness value of 2 nm. Surface diffraction measurements at I07 beamline of Diamond synchrotron were also performed in a representative film, which validated the heteroepitaxial growth. Finally, in-plane polarization versus field curves were measured as a function of temperature in selected films using interdigital electrodes (10 μm finger gap), patterned by optical lithography. Results of the ECE derived from well-known thermodynamic formulations [2,3], will be presented and correlated with the growth conditions, structure and morphology of the films.

[1] X. Moya and N. D. Mathur, Science 370, 797 (2020); [2] X. Moya et al., Nat. Mater. 13, 439 (2014); [3] A. S. Mischenko et al., Science 311, 1270 (2006); [4] T. Correia & Q. Zhang (Eds.), Electrocaloric Materials: New Generation of Coolers, Springer-Verlag (2014); [5] S. Lafuerza et al., J. Alloys Compd. 983, 173923 (2024)

Kraft Black Liquor Used as Precursor for the Carbon Coating of Na₃V₂(PO₄)₂F₃-type positive electrode materials for Sodium-Ion Batteries

Romain POUPART

Abstract

Opportunities of functional oxides for applications in electronics and energy applications are huge. However, there are challenges stemming from both intrinsic and extrinsic materials problems, e.g. composition, defect and interface control. Also, current thin film deposition routes cannot always deliver the performance of bulk materials. This talk looks at some of the reasons for the aforementioned challenges and shows ways to overcome them. Recent examples from my group are given, highlighting unrivalled device properties across different applications, with a particular focus on oxide for non-volatile memory and neuromorphic computing using resistive switching.

A08_Chemical Vapor Deposition and Atomic Layer Deposition

Date: 29-05-2024

Time: 08:45-10:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Graphene assisted III-V epitaxy towards substrate recycling

Naomie MESSUDOM

Abstract

III-V materials, such as GaAs have attracted a lot of interest for many years due to their wide range of applications, including solar cells. To date, solar cells based on III-V materials are the most efficient but also the most expensive, because III-V materials have to be grown epitaxially on expensive monocrystalline wafer (like GaAs substrate). As a result, their use in photovoltaics is limited to niche markets. The cost of the monocrystalline substrate can go up to 80% of the solar cell production cost. To reduce this part, we explore here a strategy to recycle these costly substrates using a 2D material-based layer transfer (2DLT) method. This approach involves inserting a 2D material (graphene) onto the substrate prior to epitaxial growth of the III-V material. Due to weak Van der Waals (VdW) bonds at the graphene layer plane, the epitaxially grown III-V material can be detached from the native substrate and re-used.

Since 2017, the growth of bulk materials on graphene, central for the development of the 2DLT technique, has gained significant attention. Two main growth mechanisms emerge: remote epitaxy and VdW epitaxy. In remote epitaxy, monocrystalline films are grown on a graphene coated substrate by following the substrate’s crystallinity via a remote interaction through the graphene. For VdW epitaxy, the epilayer is seed into graphene's holes and epitaxially aligned with graphene. Obtaining a monocrystalline film in both cases crucially depends on the quality of the graphene layer, growth or transfer method, and epitaxy conditions. A Ni-assisted dry transfer method using an aircushion press was developed and used to transfer a graphene layer from a native Ge substrate to a GaAs substrate. The transferred graphene layer was found to be free of organic and oxide contamination, as confirmed by XPS and Raman analysis¹. Experimental results showed that remote interactions through the graphene were not enough to achieve epitaxial growth of GaAs. Epitaxial misalignment with GaAs substrate was observed in GaAs islands grown on graphene-coated GaAs substrate. In contrast, selective nucleation of GaAs at graphene holes were achieved, followed by a lateral overgrowth. Slits in the graphene along the [100] crystallographic direction of the substrate enhanced lateral overgrowth towards planar GaAs layers, while avoiding the insertion of defective twin planes. Surface adatoms were strongly directed from the graphene mask towards the openings, which is in contrast to the finding reported for silica masks².

This study provides a guideline for the growth of a bulk material on a 2D materials, showing promise for III-V material transfer and for the integration of 2D materials in III-V material applications.

¹ Macías, C. et al. Graphene assisted III-V layer epitaxy for transferable solar cells. in Physics, 30 (SPIE, 2023).

² V.G. Dubrovskii, “Theory of diffusion-induced selective area growth of III-V nanostructures,” Phys. Rev. Mater. 7(2), 026001 (2023).

Advancing Material Performance: ZnO Thin Films for Dual-Action UV Protection and Mechanical Resilience in Cork and Rubber

Belgacem TISS

Abstract

The deleterious impact of the sun's ultraviolet (UV) rays on outdoor materials, such as cork and rubber, is well-documented, leading to ageing and discoloration. In addition, they may suffer severe mechanical wear when subjected to friction and/or mechanical wear. Both materials possess unique properties, including high elasticity, porosity, and thermal/acoustic insulation, making them integral to various applications, from wine stoppers and gym flooring to footwear and aerospace industries. Balancing the preservation of these inherent characteristics with the need for enhanced UV protection and mechanical durability presents a significant challenge. Despite the inherent difficulties associated with coating temperature-sensitive, granulated, deformable, rough surfaces, , ZnO thin films were successfully deposited on both cork and rubber using magnetron sputtering (MS) and atomic layer deposition (ALD). The resulting ZnO thin films exhibit UV-blocking capabilities with a threshold of λ ~ 320 nm, a parameter that can be optimized by adjusting the film thickness to achieve λ ~ 380 nm. This tunability significantly influences the UV protection and mechanical resilience of ZnO-coated cork and rubber. Furthermore, the adhesion strength of the deposited ZnO films on cork and rubber was assessed through tensile testing, confirming robust adherence. The successful integration of ZnO thin films not only addresses the challenges posed by UV exposure but also enhances the mechanical wear resistance of cork and rubber, opening avenues for their extended use in diverse applications.

Transition Metal Oxide Catalysts for Zinc-Air Batteries

Douglas IVEY

Abstract

Rechargeable Zn-air batteries (ZABs) have received considerable interest in recent years as potential alternatives to Li-ion batteries (LIBs), particularly for stationary applications. ZABs are safe, inexpensive and environmentally benign. The main components consist of a metallic Zn electrode, a porous air electrode (typically carbon-based), an alkaline electrolyte (concentrated KOH) and a separator. Battery performance is limited by the kinetics of the oxygen evolution (charging) and oxygen reduction (discharging) reactions (OER/ORR) at the air electrode. Kinetics can be improved through the use of catalysts, such as precious metals (e.g., Pt and Ru) or lower cost transition metal oxides (e.g., Fe, Co and Mn oxides). In this presentation, various catalyst infused air electrodes, using transition metal-based oxides, are prepared and incorporated into ZABs. Fabrication methods include atomic layer deposition (ALD), electrodeposition and infiltration. The electrodes are characterized using microstructural methods, such as electron microscopy and x-ray diffraction (XRD), and electrochemically tested in half cell and full cell configurations. These methods do not require dangerous reactants and high temperatures and are able to incorporate catalyst material throughout the thickness of the air electrode, enhancing ZAB stability during prolonged cycling.

High Surface Area Photocatalytic ZnO Films via Molecular Layer Deposition

Halil AKYILDIZ

Abstract

Semiconductor metal oxide films are of interest for wastewater treatment applications due to their photocatalytic properties. For faster and higher performance, the surface area of the photocatalytic material plays a key role. Many studies in the literature reduce the size of the photocatalytic semiconductors to nanoparticles. However, such an approach is problematic since a nanoparticle separation process is necessary after the wastewater treatment is completed. On the other hand, the immobilization of the particles or films on the planar substrates limits the performance of the photocatalytic material. In this study, fibrous textile substrates are used for immobilization, to keep the photocatalytic materials’ surface area high. Since the molecular layer deposition offers conformal films on high surface area substrates, fibers can be uniformly coated, thus increasing the performance while eliminating the problems of using nanoparticles. Organic-inorganic hybrid zincone films are deposited on the glass fibers, after which the organic components are removed via calcination. This way, porous ZnO films are formed, which show high-performance photocatalytic properties. The photocatalytic activity of the films is investigated via the methylene blue degradation method. Films were characterized via SEM, BET, and XRD methods showed that the calcination parameters played a significant role in the porosity of the films and their photocatalytic performance.

Assessing the environmental impact of ALD

Matthieu WEBER

Abstract

Due to concerns on resources depletion, climate change and overall pollution, the quest toward more sustainable processes is becoming crucial. ALD is a versatile technology, allowing for the precise coating of challenging substrates with a nanometer control over thickness. Due to its unique ability to nanoengineer interfaces and surfaces, ALD is widely used in many applications. Although the ALD technique offers the potential to tackle environmental challenges, sustainability considerations urge for greater efficiency and lower carbon footprint. Indeed, the process itself has currently a remarkable impact on the environment, which should ideally be reduced as the technique gets progressively implemented in a wider range of products and applications. In this presentation, the assessment of the environmental impact of ALD will be presented, and pathways to reduce this impact will be suggested thanks to green chemistry principles. In particular, the optimization of the reactor and processing parameters, the chemical design of greener precursors, and the use of high- throughput processes such as spatial ALD (SALD) are proposed as efficient routes to improve ALD sustainability.1 A comparative life cycle assessment between conventional ALD and SALD will also be presented, focusing on the deposition of a 20 nm alumina thin film from TMA (trimethylaluminum) and water at 200 °C as the functional unit. To ensure realistic representation, we consider typical lab-scale reactors and employ the close-proximity approach for SALD. The assessment encompasses different region-based scenarios, and our study quantifies and compares the environmental impacts associated with both ALD and SALD processes. Overall, it has been found that SALD performs significantly better with an environmental footprint being approximately 40% than the one of ALD.2

1 Weber et al., ACS Mater. Au 2023, 3, 4, 274–298

2 Niazi et al., ACS Sust. Chem. Eng. 2023, 11, 41, 15072-15082

A09_Chemical Vapor Deposition and Atomic Layer Deposition

Date: 29-05-2024

Time: 10:30-12:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Improvement of silicon/graphite anode performance by atomic layer deposited ZnO films

Karol FROHLICH

Abstract

Silicon is a promising anode material for Li-ion batteries due to its high theoretical capacity (4200 mA h g-1) and abundant presence in the earth's crust. However, significant volume expansion of silicon during lithiation and formation of an unstable solid electrolyte interphase result in a decrease of the Si-based anodes performance.

It was already shown that the operation of the silicon-based anode can be improved by surface modification. Atomic layer deposited (ALD) thin oxide films can be used for this modification as this technique allows for growth of ultrathin conformal films of excellent quality on complex surface at low temperatures.

In our contribution we present performance improvement of the silicon/graphite anode coated by ALD ZnO films. Silicon/graphite anode was fabricated by mixing 80 wt% of ball milled silicon/graphite as active material, 10 wt% of carbon black as the conductive agent, and 10 wt% of S-alginate as the binder. The slurry was then cast onto a copper foil using doctor blade technique. Resulting porosity of the fabricated anode was about 70%.

ZnO films were deposited by ALD at 100 °C using diethyl zinc (DEZn) and deionized water as a precursor and reactant, respectively. 5-40 ALD cycles of ZnO deposition was performed to obtain different thickness of the oxide films. A modified deposition parameters of the ALD process were used for porous substrates, which involved longer precursor doses and increased purging times. Growth on the silicon control wafer in the same deposition run revealed growth per cycle of 0.17 nm per cycle. Fabricated silicon/graphite anodes were analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and electrochemical measurements.

Charging/discharging measurements revealed improved rate capability (higher discharge capacity) for the ALD coated electrodes. At the charging/discharging rate of 2 C (fully charging in ½ hour) the discharge capacity of the ZnO coated was nearly 5 times higher than the uncoated pristine anode. Impedance spectroscopy unveiled lower solid electrolyte interphase layer and charge transfer resistances for ZnO coated samples. For long term cycling differential capacity analysis detected degradation of the silicon part of the anode, while ZnO coating remained more stable. The XPS analysis of the pristine and 20 ALD cycles of ZnO on silicon/graphite anode showed an increase of Li2CO3 in the pristine sample after cycling. The ZnO protected silicon/graphite electrode minimized the amount of the carbonate formation during cell cycling. It has been well established in the literature that Li2CO3 is a product of electrolyte reduction. The protection of the anode surface by ALD ZnO layer seems to be an effective way for stabilizing the electrode/electrolyte interphase to achieve better performace.

The authors acknowledge the support from VEGA 2/0162/22 and APVV-19-0461 projects.

Passivation of ‘5 V’ porous composite electrodes by atomic layer deposition

Matthias AUDREN-PAUL

Abstract

The increase of the battery energy and power density is a priority to extend the driving range of electrical vehicles and to reduce the charge duration. In addition, it is essential to reduce the overall ecological impact and the cost of batteries, from the mine to the wheel. Replacing conventional layered oxides with LiNi_0.5Mn_1.5O₄ (LNMO) as a positive active material would be a significant step forward in addressing these issues. Indeed, on one hand the absence of cobalt and the low Ni content in the material would reduce significantly the toxicity and the cost of positive electrodes. On the other hand, this material that operates at a higher potential (~5 V vs Li+/Li) [1] and has a tridimensional crystalline structure favourable to fast lithiation/delithiation, would be an asset for both energy and power densities. Unfortunately, this potential lies outside the stability window of liquid electrolytes, leading to detrimental interfacial reactions and to a rapid deterioration of Li-ion cell performance.

This work aims to develop a passivation layer through an Atomic Layer Deposition (ALD) process, covering the whole active surface of the composite electrode, in order to prevent the oxidation of the electrolyte. Thanks to a self-limiting process, this chemical vapor deposition technique allows to deposit nanometric and conformal layers [2] even within porous materials such as composite electrodes.

To address the inherent constraints imposed by the ALD process, the PVdF binder (Tm ~170°C) [3] commonly used in composite electrodes is replaced by a polyimide. The stability under vacuum and temperature (up to 350°C) of polyimide-based composite electrodes is thoroughly investigated by X-ray Photoelectron Spectroscopy (XPS) and electrochemical analyses. We show, despite the slight reduction of Mn⁴⁺ at the surface, that the electrochemical behaviour is unchanged compared to PVdF-based electrodes.

Regarding the passivation layer, LiF was chosen due to its high anodic stability [4]. After the optimization of the ALD process, the influence of this passivation layer on electrochemical performance is then assessed during cycling of this electrode in a half-cell configuration.

REFERENCES

[1] Pieczonka, N.P.W. et al. (2013) ‘Understanding Transition-Metal Dissolution Behavior in LiNi0.5Mn1.5O4 High-Voltage Spinel for Lithium Ion Batteries’, The Journal of Physical Chemistry C, 117(31).

[2] Detavernier, C. et al. (2011) ‘Tailoring nanoporous materials by atomic layer deposition’, Chemical Society Reviews, 40(11).

[3] Pham, H.Q. et al. (2019) ‘Non-flammable LiNi0.8Co0.1Mn0.1O2 cathode via functional binder; stabilizing high-voltage interface and performance for safer and high-energy lithium rechargeable batteries’, Electrochimica Acta, 317.

[4] Zhu, Y. et al. (2015) ‘Origin of Outstanding Stability in the Lithium Solid Electrolyte Materials: Insights from Thermodynamic Analyses Based on First-Principles Calculations’, ACS Appl. Mater. Interfaces, 7 (42).

Molecular Layer Deposition of Hybrid Materials: Insights from Simulations

Michael NOLAN

Abstract

In Atomic Level Processing, exemplified by Atomic Layer Deposition (ALD), Thermal Atomic Layer Etch (tALE), Molecular Layer Deposition (MLD) and Vapour Phase Infiltration (VPI), the key chemistry takes place at surfaces which also drives the self-limiting characteristics of these processing techniques. Surface chemistry (in a broad sense) includes nucleation at the initial substrate, which can be a solid or a polymer, first precursor adsorption or interaction in infiltration processes, co-reactant adsorption and reaction, surface conversion and ligand exchange or attachment. This surface driven chemistry can be elucidated using state of the art first principles simulations, primarily with density functional theory (DFT).

In this talk, I will present our DFT results on the chemistry of some selected MLD and VPI processes.

The first topic is the mechanism of MLD of alucones as the prototypical reaction in MLD. Experimental results indicate different thickness and growth rates for ethylene glycol and glycerol where the major difference is the presence of a third -OH group in the glycerol molecule in addition to the -OH terminations. We show the preference of both molecules to lie flat but the glycerol uses the protruding -OH group to drive further reactions with TMA. Given the lack of ambient stability in these alucones, we present functionalized phenyl rings as rigid alternative and show that the flat-lying double reaction is disfavoured so the molecules remain upright. Subsequent work on titanicones with both DFT and experiment, using rutile/anatase and these aromatic precursors, confirms the enhanced stability of MLD films using aromatic molecule, which also show high growth rates.

For VPI we will present results exploring infiltration of some metal precursors in different polymers to assess differences between polymers for a given reactant and for different reactants within a given polymer. The first examples if the infiltration of the RuO4 ToRuS precursor into PMMA and polystyrene (PS) to understand selective Ru deposotion in block copolymer templates of PMMA and PS. The latter shows RuO4 infiltration, while PMMA does not. The simulations show that there is no favourable interaction between sites on PMMA and the precursor but there are favourable interactions with PS. Furthermore, introduction of H2 is shown to reduced RuO4, depositing Ru metal and releasing water; this allows for templated deposition of metal lines, but is promising for other materials including oxides. We will present current work in the group on modelling further VPI chemistries, including TMA in a series of polymers and other metal precursors.

This presentation demonstrates how first principles simulations are vital to understand MLD and VPI processes, giving new insights into experimental results or enabling the development of entirely new process chemistries.

Vacancy Engineering of Vanadium Carbide MXene: Synthesis Strategies and Supercapacitor Applications

Rutuparna SAMAL

Abstract

Silver nanoparticles and thin films have shown strong benefits to enhance the properties of materials used in catalysis, light harvesting using its plasmonic properties and heat management through its high reflectance. Usual deposition methods rely on liquid-phase deposition, which is limited to thick films of nanoparticles, or on physical vapour deposition (magnetron sputtering), which cannot cover 3D complex substrates and usually requiring high vacuum and large equipment pieces. Atomic layer deposition (ALD) could solve part of these issues by providing high-quality films with good control of the properties at the lowest length scale and highly conformal deposition.

By using plasma-enhanced atomic layer deposition (PE-ALD), we demonstrate how we can tune the morphology of silver nanoparticles, and consequently their plasmonic resonance in a large spectral range. We have further extended the range of morphologies obtained using the same precursors by using an original pulsed-plasma chemical vapour deposition (PP-CVD) method, demonstrating the harvesting of a wide range from visible to near infrared light. Both processes show strong potential for uniform large-scale deposition of silver, including conformal deposition in 3D structures, which has been demonstrated using lateral high aspect ratio structures. Moreover, the films obtained by PP-CVD are highly compact, and a post-treatment leads to highly conductive continuous films, showing good infrared reflectivity. When stacked with metal oxide layers obtained also by ALD, this opens to the realisation of heat reflective coatings on complex surfaces such as curved glass.

The strong tunability of the properties, combined with the high conformal deposition obtained by these techniques, is of strong potential for building up complex 3D plasmonic and optical functional coatings, which are of strong interest for applications based on light harvesting and heat management. The films deposited by these techniques however still show limitations as compared to their counterparts obtained by magnetron sputtering, and I will discuss the next steps towards integrating the ALD of silver films into future applications.

A10_Chemical Vapor Deposition and Atomic Layer Deposition

Date: 30-05-2024

Time: 08:45-10:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Interface modifications for thermoelectric materials by a variety of ALD techniques

Amin BAHRAMI

Abstract

In thermoelectric materials, phase boundaries are crucial for carrier/phonon transport. Manipulation of carrier and phonon scatterings by introducing continuous interface modification has been shown to improve thermoelectric performance. In this presentation three different ALD methods for the interface engineering of thermoelectric materials will be presented:

Powder ALD: A strategy of interface modification based on powder atomic layer deposition (PALD) is introduced to accurately control and modify the phase boundary of pure bismuth. Ultrathin layers of Al₂O₃, TiO₂, and ZnO are deposited on Bi powder by typically 1–20 cycles. All of the oxide layers significantly alter the microstructure and suppressed grain growth. Interface modifications aid in the formation of an energy barrier by the oxide layer, resulting in a substantial increase in the Seebeck coefficient that is superior to that of most pure polycrystalline metals. The ALD-based approach can be easily applied to other thermoelectric materials.

Non-epitaxial multilayers of 2D materials by ALD: A detailed study was performed on these so-called ferecrytals of Sb2Te3 and SbOx, which has been grown at the same temperature as Sb₂Te₃. Without post-annealing, the electrical and thermoelectric characterisation of the highly ordered samples have been performed with the ZT-chip setup. In general, the carrier mobility is very high >150 Vs²/cm² and is even improved when the thickness of the Sb2Te3 layers is reduced and the number of SbO_x layers (typically 2 nm thickness) is increased. We have also grown ferecrystals based on Sb₂Te₃ and Sb₂Se₃ with tetrahedral and orthorhombic crystal structure, respectively. The p-type hole carrier concentration of Sb₂Te₃ films can be enhanced through the sublayer doping of Sb₂Se₃. Reduction of the Sb2Te3 thickness resulted in a high Seebeck coefficient of 172 μV/K at room temperature.

Encapsulation of thermoelectric modules: We will demonstrate that the ALD coating of 3D structure of thermoelectric modules significantly enhances the lifetime of thermoelectric

Precursor reactivity and film stability in ALD/MLD: Co-organic thin films as model system

Topias JUSSILA

Abstract

The strongly emerging atomic/molecular layer deposition (ALD/MLD) technique for hybrid inorganic-organic materials [1] has the same working principle as the parent atomic layer deposition (ALD) technique for pinhole-free and conformal inorganic coatings. Unlike the traditional solution-based fabrication techniques of inorganic-organic materials, the gas-phase ALD/MLD enables both fabrication of nanoscale solvent-free thin films and in-situ integration of the deposited material with other device components. The most important aspects to consider when developing new ALD/MLD processes and aiming at new functional inorganic-organic thin films for practical applications are (i) the reactivity of the organic precursor and (ii) the stability of the resultant thin film.

Both the reactivity and stability are largely affected by the choice of the reactive group of the organic precursor molecule. To systematically study the effect of different reactive groups on these two properties, we developed novel ALD/MLD processes for three different materials: Co-benzenedithiolate (Co-BDT), Co-hydroquinone (Co-HQ), and Co-terephthalate (Co-TP). All the organic precursors have the same backbone (benzene ring) but different reactive groups (SH, OH, COOH) which enables the systematic study. The new Co-precursor employed, Co(tmsaedma)2 [2], had not been used in any gas-phase depositions before; this nitrogen-coordinated precursor provided higher reactivity compared to the often-used metal β-diketones, which enabled low deposition temperatures and good compatibility with the organic precursors.

All the three novel Co-organic deposition processes were successfully developed and found to yield high-quality and uniform thin films with desired composition. A variety of characterization techniques such as FTIR, XRR, XPS and RBS were employed. We show that the TP precursor is most reactive and provides the most stable Co-organic thin films, presumably owing to its acid groups. The reactivities of BDT and HQ were of the same level, but the Co-BDT films were found to be more stable than the Co-HQ films. This enhanced stability of the SH-based Co-BDT films is a very attractive result, since OH-based films (HQ) have often poor stability whereas acid precursors such as TP suffer from low volatility. The thiol precursors (BDT) can thus provide proper stability and reactivity together with high volatility. We foresee that these Co-organic thin films could be employed in flexible battery applications [3]. Moreover, the excellent performance of the novel Co-precursor as found here paves a way for other similar metal precursors for ALD and ALD/MLD.

[1] J. Multia and M. Karppinen, Adv. Mater. Interfaces 9, 2200210 (2022).

[2] D. Zanders, N. Boysen, M. A. Land, J. Obenlüneschloß, J. D. Masuda, B. Mallick, S. T. Barry, and A. Devi, Eur. J. Inorg. Chem. 2021, 5119 (2021).

[3] H. Ou, Q. Xie, Q. Yang, J. Zhou, A. Zeb, X. Lin, X. Chen, R. C. K. Reddy, and G. Ma, CrystEngComm 23, 5140 (2021).

Nitrogenated-Carbon heterostructures for electrocatalytic hydrogenation reactions

Christian SCHRÖDER

Abstract

Biomass and biomass‑derived bio-oil have the potential to become a sustainable carbon feedstock, lowering the dependence on fossil fuels. This bio-oil needs to be upgraded to produce fuels and fine chemicals. Hydrogenation reactions are a well-established way to do this. Thermal hydrogenation is an energy intensive process with the need for an external supply of hydrogen. Electrocatalytic hydrogenation (ECH) bypasses these drawbacks, and when powered by renewables, offers a way to store renewable energy in chemicals. State of the art catalysts for ECH are precious metals, which inhibits the scale up of this technology, due to their cost and scarcity. To make ECH a real alternative, new catalyst materials are needed.

Herein, we present our work on MoS2/N-Carbon heterostructures for the ECH. These heterostructures have recently been shown to have promising activity for the hydrogen evolution reaction, where the performance can be modulated through the choice of carbon substrate. Carbon has a list of properties which make it a promising candidate for reduction reactions; they are widely available, environmentally benign, stable at cathodic potentials and can be tailored towards specific applications. One way of tailoring the carbon is through doping with heteroatoms, for example nitrogen.

Nitrogenated-carbon thin films were synthesised in a two-step process, containing dc-magnetron deposition, followed by thermal annealing. This allows good control over the properties of the films. In a subsequent CVD step, MoS2 was grown on the films, using a close proximity method. These model electrodes were investigated in the ECH of Benzaldehyde. The obtained results give insights into the mechanistic of the ECH and allow us to outline possible design principles for developing electrocatalysts for the ECH based on functional carbons.

[1] Nolan, H.; Schröder, C.; Brunet-Cabré, M.; Pota, F.; McEvoy, N.; McKelvey, K.; Perova, T. S.; Colavita, P. E., MoS2/carbon heterostructured catalysts for the hydrogen evolution reaction: N-doping modulation of substrate effects in acid and alkaline electrolytes. Carbon 2023, 202, 70-80.

Electrochemical Performance of Oxidative Chemical Vapor Deposition of Polypyrrole on Carbon Fiber for Flexible Supercapacitor

Fika FAUZI

Abstract

Supercapacitors play a crucial role in rapidly storing and releasing short-term energy, offering high power density and cyclic stability. However, enhancing their energy density while maintaining stability remains a challenge. Current research aims to enhance energy density by utilizing conducting polymers with pseudo-capacitive behavior. However, the issue of volume shrinkage during charge storage reduces the cycling stability. Combining conducting polymers with carbon materials emerges as an attractive solution to address these challenges and maintain the cycling stability of carbon materials¹.

Ensuring good contact between a conducting polymer and carbon-based materials is crucial for efficient charge transfer and preventing interfacial failure. Traditional solvent-based processing techniques face challenges in achieving conformal coating on carbon substrates, potentially impacting electrode performance due to issues like surface dewetting, and interfacial tension effects². To address this, we employ the oxidative chemical vapor deposition (oCVD) method to deposit a sub-micron-thick layer of polypyrrole (PPy) onto carbon fiber for a flexible electrode of supercapacitor. The flexibility of carbon fiber effectively mitigates the volume shrinkage of PPy, ensuring prolonged cycling stability. Fine-tuning oCVD parameters, such as deposition time and gas carrier flow, enables control over PPy layer thickness and morphology at the nanoscale. This porous structure of PPy-carbon fiber electrode with excellent interface will improve the charge transport, the scan rate performance, specific areal capacitance and energy density. By enabling the deposition of PPy at the nanoscale, it opens to the exciting prospect of miniaturizing functional devices, such as creating a flexible and compact supercapacitor.

References

[1] Ahmed, S., et al. Critical review on recent developments in conducting polymer nanocomposites for supercapacitors. Synthetic Metals, 2023, 295, 117326.

[2] Dianatdar, A., et al. Oxidative chemical vapor deposition of polypyrrole onto carbon fabric for flexible supercapacitive electrode material. Synthetic Metals, 2023, 298, 117444.

A11_Photovoltaics

Date: 30-05-2024

Time: 10:30-12:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Free-standing Pd-based nanostructures by Atomic layer deposition for cogeneration hydrogen electrolyzers

Zahra HAGHEH KAVOUSI

Abstract

Water electrolysis for hydrogen production is an alternative renewable energy source but it is currently inefficient and expensive. A significant portion of the electricity demand required by electrolyzers to produce green hydrogen, almost 90%, is consumed by the oxygen evolution reaction (OER), due to its slow kinetics [1]. By replacing OER with the oxidation of biomass-based compounds like glycerol (GOR), the energy input of the electrolyzer can be significantly reduced by two times. However, the most crucial obstacle in producing hydrogen fuel is to design electrocatalysts able to reduce drastically (reactions) overpotentials leading to a limitation of the electricity required by electrolyzers. Atomic layer deposition (ALD) is a superior method for attaining precise thickness and composition control, making it a valuable technique for growing high-quality nanostructured materials that are crucial for achieving ideal electrochemical properties [2].

In this work, we report the growth of Pd-Ni-based nanostructures directly on gas diffusion electrode (GDE) by ALD and highlight the advantages of Pd-Ni bimetallic nanostructure electrodes for hydrogen evolution reaction (HER) and GOR in half-cell and in a complete electrolyzer configuration. Electrochemical characterization techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) were used to measure the electrocatalytic activity (current density, charge transfer resistance, stability, etc.). The thermal treatment to convert GDE-Pd-NiO into GDE-PdNi nanoalloys led to bimetallic-based electrodes that act synergistically and exhibit superior electrocatalytic performance: high current density at low potentials (below 1 V vs RHE) for GOR and as a reduced overpotential at the metric current density of 10 mA cm^-2 during HER. Additionally, EIS indicated a significant decrease in charge transfer resistance. The integration of bimetallic GDE-PdNi as positive and negative electrodes in a glycerol fueled electrolyzer resulted into an efficient and dual H₂ (cathode) and valuable organic molecules (anode) production system with cell voltage below 1 V, which could have significant implications for sustainable energy production.

[1] Y. Holade et al., Catalysis Science & Technology 2020, 10, 3071-3112.

[2] M. Weber et al., Applied Catalysis B: Environmental 2019, 257, 117917.

Plasma Assisted Atomic Layer Deposition of III-Nitride

Noureddine ADJEROUD

Abstract

In the last few decades, there has been a phenomenal rise and progress in the field of III–Nitride semiconductors. Now, the materials group III-N is changing the path of high-performance integrated circuits (IC) technology in high power and high frequency regimes and has received much attention due to its wide and direct bandgap, high electron mobility and high breakdown electrical field.

III-N semiconductors are largely present in the industry, through chemical vapor deposition (CVD) techniques such as Metalorganic vapour-phase epitaxy (MOVPE). Those deposition techniques use conventionally the reaction of ammonia (NH3) with industrially relevant precursors such as trimethylaluminum (TMA), trimethylgallium (TMG) or trimethylindium (TMI) at high temperatures (750-900 °C) [1]. Plasma-assisted Atomic Layer Deposition (PA ALD) is becoming a trustworthy alternative to the standard CVD deposition techniques, and it appears as a solution for highly conformal coating and low temperature processing as two important assets to tackle growth temperatures of the nitride films not interfering with CMOS circuitry.

This work is based on the optimization and engineering of the plasma ALD of c-axis highly oriented aluminium nitride (AlN) films we proposed [2]. The pathway was further extended to facilitate low temperature (<450 °C) deposition of other III-N materials, such as GaN semiconductors with wide bandgap. In this work we utilized a gas mixture of H2/Ar/N2 as nitrogen precursor for nitride thin films initiated by a plasma source. The mix of Ar and H2 allows both to stabilize the plasma phase and to induce an optimized reducing of the ligands of the organometallic precursors reducing the carbon contaminants measured in the materials. We observed by XPS stoichiometric III-N films with no detectable carbon contaminants and also a low level (<5%) of oxygen contaminants in the nitride films. The XRD and TEM analysis confirm privileged hexagonal crystalline structure of the thin film below 100 nm thickness.

Insights on the ALD set-up and specific sequence of the deposition process will be presented for the growth of aluminium nitride (AlN).

Those results have the potential to pave a way for both buffer-oriented seed films for post-growth, and also films with tailor made electronics properties for the next-generation of III-Nitride/CMOS components and functional coatings with piezoelectric and semiconducting properties for MEMS applications with transducing capabilities.

Reference list

[1]. A. V. Kondratyev et al., physica status solidi (c), volume 5, issue 6 (2008)

[2]. Tai Nguyen, Noureddine Adjeroud, Sebastjan Glinsek, Yves Fleming, Jérôme Guillot, Patrick Grysan, and Jérôme Polesel-Maris, APL Materials 8, 071101 (2020)

Tuning optoelectronic properties in type II Silicon Clathrate films for photovoltaic applications

Anil Kumar BHARWAL

Abstract

Silicon materials have been extensively studied for their applications in solar technology over the past seven decades. Recently, there has been a growing interest in exotic forms of silicon, particularly silicon clathrates, which exhibit attractive optoelectronic properties for solar technology [1]. Type II silicon clathrate (Na_xSi₁₃₆), an open-cage polymorph of silicon with unique structural properties capable of accepting or releasing Na atoms, was first discovered in powder form in 1965 [2]. However, research on NaxSi136 films is a relatively recent development and carries significant implications for advancing photovoltaic technologies due to the direct band gap of 1.9 eV [1] . Notably, the optoelectronic properties of these cages in Na_xSi₁₃₆ films can be significantly altered by inserting or removing Na, making them versatile for various energy-related applications [3-6]. However, it is essential to understand the impact of Na occupation within the Na_xSi1₃₆ cages on optoelectronic properties.

This research focuses on investigating the electronic properties resulting from the insertion and removal of Na atoms in Na_xSi₁₃₆ films using Kelvin Probe-Ambient Pressure Photoemission Spectroscopy (KP-APS) for the first time. Films of Na_xSi₁₃₆ clathrates were fabricated on different types of silicon wafers and subjected to Thermal Press Annealing to enhance the overall film quality. Using KP-APS and optical measurements, we probed the energy levels and accurately constructed the band diagram for each of the tested clathrate systems. By varying the Na composition parameter (x) from 0 to 23 within Na_xSi₁₃₆ films, we observed the closure of the band gap, with the Fermi energy level moving towards the conduction band, consistent with density functional theory (DFT) calculations. This work highlights the great potential of processing and doping strategies for clathrate films to optimize their use in photovoltaic devices with a novel heterojunction configuration, as well as their potential application in diverse energy-related fields.

Acknowledgement

The present project is financed by ANR Exosil- Exotic Silicon: silicon clathrate films (project-ANR-22-CE50-0025).

References

[1] R. Vollondat et al., J. Alloys Compd., vol. 903, p. 163967, 2022.

[2] J. S. Kasper et al., Science, vol. 150, no 3704, p. 1713‑1714, 1965.

[3] T. Fix et al., J. Phys. Chem. C, vol. 124, no 28, p. 14972‑14977, 2020.

[4] A. Dopilka et al., Adv. Energy Sustain. Res., vol. 2, no 5, p. 2000114, 2021.

[5] Y. Liu et al., Inorg. Chem., vol. 62, no 18, p. 6882‑6892, mai 2023.

[6] R. Vollondat et al., J. Chem. Phys., vol. 158, no 16, 2023.

ALD-metal oxide materials and surface modification for perovskite solar cells

Nathanaelle SCHNEIDER

Abstract

Though perovskite solar cells (PSCs) have reached very high efficiency levels, it is accompanied by concerns on long-term stability and open questions about upscaled manufacturing. Atomic layer deposition (ALD) is a technique that can provide unique contributions to both issues. In particular, dedicated interface engineering and innovative charge transport layers (CTL) are critical for improving device stability, and ALD-grown metal oxide films have drawn immense attention for the fabrication of stable PSC.

Mostly, ALD-CTL are integrated below the metal halide perovskite (MHP) absorber, namely TiO₂ or SnO₂ as electron transport layer (ETL) in n-i-p configuration, or NiO_x as hole transport layer (HTL) in p-i-n configuration. We have investigated the incorporation of niobium in TiO₂ and SnO₂ by a supercycle strategy, i.e inserting a single Nb₂O₅cycle between a series of TiO₂ or SnO₂ cycles. This has allowed controlling the incorporation of Nb and tuning the film properties. These latter were applied as ETL in n-i-p PSCs and showed an improvement of the cell performances (stability, power conversion efficiency).

However, despite the advantages of ALD, the deposition of metal oxides directly on bare perovskite has so far not been achieved without damaging the perovskite layer underneath. In fact, the changes to the physicochemical and electronic properties at the perovskite interface upon exposure to the ALD precursors can alter the material and hence device functionality. We have developed low temperature ALD processes for SnO₂ and NiO_x that are compatible for a deposition on top of the MHP absorber. Their interfaces with the MHP were investigated by synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES) and evidenced the formation of new chemical species that in some case lead to detrimental band bending that could be mitigated by additional interlayer.

Finally, these challenges have prompted us to develop an original in situ instrumentation setup , which combines ellipsometry and photoluminescence in order to correlate film property (thickness) and function (passivation, charge extraction).

Exploring Metal Oxide-Ferroelectric Interfaces for Cutting-Edge Piezocatalytic Water Splitting and Pollution Control

Abinaya KRISHNAMURTHY

Abstract

Perovskite materials, characterized by their distinctive crystalline structure (ABX₃, A = Cs⁺, CH₃NH₃⁺, CH(NH₂)²⁺; B = Pb²⁺, Sn²⁺; X = I^-, Br^-, Cl^-) and outstanding electronic properties, are highly promising (materials or candidate) for diverse applications. Notably, they find application as key constituents of advanced energy devices, with a significant focus on photovoltaics. All-inorganic cesium lead triiodide (CsPbI₃) perovskites exhibit high potential in photovoltaics due to excellent thermal stability and a suitable bandgap (Eg≈1.72 eV) ideal for tandem devices. However, the performance of CsPbI₃ perovskite solar cells (PSCs) is hindered by challenging crystal quality control, resulting in elevated nonradiative recombination processes[1]. The structural instability of black-phase CsPbI₃ (α, β, and γ) at room temperature, prone to spontaneous evolution into the photoinactive δ-phase, further limits its potential. This transition can be accelerated by ambient moisture, leading to diminished power conversion efficiency (PCE). Consequently, stabilizing black CsPbI₃ at room temperature becomes crucial. However, the nucleation and growth processes of this material are largely uncontrollable, resulting in defects from conventional coating methods. Herein, understanding the fundamental mechanism of film formation, specifically in nucleation and growth, is crucial for adjusting film crystallization kinetics precisely. Additive engineering optimization has proven successful in developing Cs-based photovoltaic devices with improved efficiency and stability. This work aims to obtain a stable CsPbI₃ polycrystalline thin film by modulating various parameters in the solution processing, including the solvent, additives modifying solution chemistry, and alternative Pb sources like DMAPbI₃[2]. Here we proposed to synthetize DMAPbI₃ through hydrolysis and using it directly as a lead source, achieving a better stoichiometric control involving DMA⁺, that ultimately leads to higher-quality films. Intermediate complex formation during crystallization, such as the inclusion of Cl⁻ ions in the precursor solution, positively impacts perovskite nucleation. Importantly, Cl⁻ ions aid nucleation without becoming part of the perovskite lattice, leading to films with enhanced optoelectronic properties, suggesting improved light interaction. The presented strategies investigate the effect on nucleation and the impact of solute–solvent crystalline intermediate phases on chemical reaction kinetics. Finally, optimized films have been integrated and tested in solar cells, showing a substantial improvement of performances.

[1] Shuang Li et al. ACS Appl. Energy Mater. 2023, 6, 3514−3524

[3] Yunhe Pei et al iScience 15, 165–172, May 31, 2019

A12_Photovoltaics

Date: 30-05-2024

Time: 13:45-16:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Low-thermal budget grown SiO2 passivation layers for silicon solar cells

Prathap PATHI

Abstract

Fabrication of high-efficiency solar cell requires low-thermal budget processes in order to protect the electronic quality of silicon substrate that results in high minority carrier lifetime. SiO2 is a potential candidate for the high-efficiency cell structures such as PERC (passivated emitter rear contact) in view of optical gain from rear surface of the cell. Usually, SiO2 layers are grown using thermal oxidation (wet or dry) at the temperatures > 900 oC at which the silicon substrate is prone to induce lattice defects due to thermal stress. In this report, a procedure to achieve a very high level of surface passivation for silicon wafers at low-thermal budget is elaborated. Electro-chemical oxidation of silicon was used to grow silicon di-oxide (SiO2) layers at room-temperature. Growth kinetics of SiO2 layers was investigated at a constant source voltage for different time intervals and an optimum condition for the growth of oxide layer is discussed. Evolution of thickness of oxide layer was studied using spectroscopic ellipsometry, and a maximum thickness of ~ 60 nm was observed in 180 min. Passivation characteristics of SiO2 layers was investigated using minority carrier lifetime (teff) measurements. The highest quality of surface passivation was obtained for the SiO2 layers grown for a duration of 15 min, for which teff is found to be 278 µs with a surface recombination velocity of 37 cm/s and an implied open-circuit voltage (iVoc) of 622 mV after a short hydrogen treatment at 400 oC that corresponds to contact annealing process. The SiO2 layer showed an improvement of 20 mV in open-circuit voltage of the solar cell device, implying the effectiveness of the passivation layer. Interface between SiO2 layers and silicon was characterized by capacitance and conductance measurements.

Surface functionalization of inorganic hole transporting materials at the recombination junction of two-terminal silicon / perovskite tandem solar cells

Pia VASQUEZ

Abstract

The recombination junction (RJ) in monolithically integrated tandem solar cells is a critical component in device design in terms of the compromise between layer requirements (optical transparency, carrier selectivity, etc) as well as keeping the physical connection between the subcells. Additionally, the challenge of Indium suppression in the solar cells industry constraints the choice of materials suitable for the RJ. In the case of silicon heterojunction (SHJ) / perovskite (PK) tandem solar cells, power conversion efficiency records (> 33% by the end of 2023) have been demonstrated mostly using Indium-tin oxide (ITO) tin films in small aperture areas (~1 cm²).

In this work, we have investigated the electronic properties at the surface of three In-free, inorganic hole transporting candidates (materials 1, 2 and 3) to be integrated in a two-terminal SHJ / PK tandem solar cell with inverted polarity (p-i-n). The layers, featuring around 20 nm each, were connected with the SHJ bottom cell through a nanocrystalline silicon (nc-Si :H) tunnel recombination junction (TRJ) and to the PK top cell absorber either directly, either through a thin, carbazole-based self-assembled monolayer (SAM). Modifications induced by the SAM on the electronic properties of HTL surfaces were studied through measurement of the contact potential diference at the surfaces, and its effect on the electrical behavior at the interface TRJ / HTL were characterized with dark IV measurements. We have found for materials 1 and 2 that surface work functions increased up to 0.7 Ev and were related to the formation of a barrier at the contact Au/SAM, which can be a marker of the dipole alignment for efficient holes extraction.

Furthermore, the presence of the SAM at the interface between the HTLs and the PK absorber was characterized by the XPS emission peaks P2p and N1s around 133 and 400 Ev respectively, and found in all samples. However, an increment on the photoluminescence spectroscopy emission intensity of the perovskite absorber (around 1.7 Ev) up to a factor of 10 was observed in the samples that showed increased work functions and formation of Schottky barriers at the contacts (materials 1 and 2). In contrast, for material 3, we have found no significant differences in surface work function, IV characteristics nor PL intensity by effect of the SAM. These results show that chemical detection of the SAM is not enough to assess its role on holes extraction and the surface functionalization of the underlayers. In terms of tandem performance, we have found that, for a tandem solar cell with material 1 as HTL, device efficiency can increase from 2.5 to 12.5% (aperture area of 9 cm²) by including SAM interlayer between the HTL and the PK absorber.

Thermal and Photo-Degradation Study of 𝜶-FAPbI3-Based Perovskite Probed by In Situ characterization techniques

Julie RUELLOU

Abstract

Hybrid halide perovskite has established its credibility as high performance thin film photovoltaic technology. In only one-decade, the hybrid organic-inorganic halide perovskite solar cell achieved to compete with all mature crystalline technologies, by reaching a certified 26.1 % power conversion efficiency (PCE) on cells and 17.9 % PCE on small modules. Perovskite’s strength stem from their remarkable opto-electronic properties, including bandgap tunability by composition engineering, direct electronic transition (α ≈ 2.10⁴ cm^-1), low exciton binding energies (< 25 meV) and long-lived of the excited states exceeding the microsecond time scale. Another major benefit lies from their potential low energy cost production, low materials resources which translate into cost-benefits for the end users.

However, the technology still requires significant considerations regarding lead utilization on one hand and the multi-faceted stability issues which may engender rapid degradation under various external stressors on the other hand (temperature, humidity, light and electrical bias). This latter still constitutes a barrier to bring the technology at higher TRL than 6.

To cope with the stability issue, it is mandatory to precisely understand the multiple degradation pathways of the perovskite. In situ characterization techniques are key tools to probe the pathways of degradation. In this communication, we will be discussing the degradation of α-FAPbI₃ on the basis of temperature-controlled in situ x-ray diffraction (XRD), corroborated with in situ electron spin resonance spectroscopy (ESR). In particular, we clarify the thermal stability of the perovskite and the degradation pathways under different experimental conditions. Based on in situ XRD, we report that α-FAPbI₃ degradation is substantially accelerated when temperature is combined with illumination and when it is interfaced with the extraction layers. In addition, by contrast to in darkness for which α-FAPbI₃ degrades directly into PbI₂, we reveal the existence of a temperature gap under illumination involving an intermediate step with a non-crystalline phase resulting from the perovskite degradation and contributing to the formation of PbI₂by-product. The latest results obtained by EPR spectroscopy allowed to understand the thermal degradation mechanism at the electronic scale, and helped elucidate that the intermediate phase indirectly observed by XRD under illumination is due to the presence of a lot of defects in the perovskite, created by the irradiation combined with temperature.

Lattice Volume Anchoring Attenuates Natural Performance Loss in Perovskite Solar Cells During Day/Night Cycling

Tiankai ZHANG

Abstract

It is commonly believed that perovskite solar cells (pero-SCs) show enhanced stability under day/night cycling due to reported self-healing effect in the dark.1,2 However, it is discovered that the operational lifetime of highly efficient FAPbI3 pero-SCs is in fact much shorter under day/night cycling mode, being into question the widely accepted approach to estimate the pero-SCs’ operational lifetime based on continuous mode testing. We reveal the key factor to be the lattice volume change during the operation, an effect which gradually relaxes under the continuous illumination mode but cycles synchronously under the cycling mode.3,4 The cycled lattice volume change results in chemical degradation and deep trap accumulation during operation, decreasing the ion migration potential and hence the lifetime under the cycling mode.5 To address the challenges induced by the synchronously cycled lattice volume, we introduce Ph-Se-Cl to stabilize the perovskite lattice during day/night cycling. As a result, the pero-SCs achieved the certified efficiency of 26.3% and a 10-time improved T80 lifetime under the cycling mode (ISOS-LC-2 suggested protocol) after the modification. Our results uncover the unique degradation mechanism caused by the cycling mode and highlight the necessity of lattice volume fixing to prolong the real working lifetime of pero-SCs.

Zinc sulfide interface layer for stable and high performance ultrasonically sprayed Sb₂S₃ solar cells

Hadeer SALEH

Abstract

Antimony sulfide (Sb₂S₃) is a promising candidate for semi-transparent photovoltaic applications due to its band gap of 1.7 eV, high absorption coefficient, abundance in nature and non-toxicity. However, the photoconversion efficiencies are still far from the theoretical values. The recombination of photogenerated carriers at front and back interfaces is one dominant factor hindering the device performance. This research work introduces for the first time the application of ultra-thin interface layer of ZnS in Sb₂S₃ solar cells by the scalable, facile and low-cost Ultrasonic Spray Pyrolysis (USP) technique. The study investigates the influence of ZnS layer incorporation, deposited using ZnCl₂:thiourea=1:2 in ethanol solution (5*10-4M ZnCl₂) at different temperatures ranging from 350℃ to 500℃ on the morphological and structural properties of Sb₂S₃ absorber layer grown by USP, and the FTO/TiO₂/ZnS/Sb₂S₃/P3HT/Au solar cell performance. The optical bandgap of ZnS layer was found to be 3.4 eV. Introduction of ZnS layer promotes the growth of Sb₂S₃ crystallite and their alignment along the (hk1) direction. According to XRD the crystallite size of Sb₂S₃ increased from 34 nm to 46 nm when growing on ZnS layer deposited at 450℃ and texture coefficient of (011), (111) and (211) peaks arise above 1.0 independent of ZnS deposition temperature.

The Sb₂S₃ solar cell efficiency increased from 4.65% to 5.81% by using ZnS interfacial layer obtained by 70 spray cycles at 500℃. This improvement is due to the enhancement in V_oc from 627 mV to 650 mV, J_sc increase from 13.6 mA/cm² to 14.8 mA/cm² and FF from 55% to 61%, being supported by strong increase in device shunt resistance. In this study we demonstrated that ZnS interface layer by simple USP method is able significantly reduce the recombination at TiO₂/Sb₂S₃ interface and improve the photogenerated carriers collection. Furthermore, the ZnS-based devices were found to retain about 75% of their initial efficiency after 500 hours, which is 10% higher than the reference devices fabricated directly on the TiO₂ surface.

Keywords: antimony sulfide; ultrasonic spray; ZnS interface layer, thin film solar cell

In situ and ex situ stability studies of solar-selective coatings for concentrated solar power

Matthias KRAUSE

Abstract

An increased operation temperature compared to the current maximum of 575 °C is mandatory for an improved energy efficiency of concentrated solar power (CSP) plants. Stability at high temperatures in air is a main criterion for the material selection. Moreover, the solar absorber should be solar-selective, since the thermal emittance reduces the efficiency of the solar light into heat conversion and finally limits the accessible temperature [1].

In this contribution, stability studies of Al_yTi_1-y(O_xN_1-x)- and WAlSiN-based solar-selective multilayer coatings are presented. In situ RBS and spectroscopic ellipsometry (SE) measurements showed full stability of individual Al_yTi_1-y(O_xN_1-x) layers during thermal cycling between RT and up to 750 °C in high vacuum. Two complete AlyTi_1-y(O_xN_1-x) solar-selective coating (SSC) stacks were stable in air for 12 h at 650 °C. During cyclic durability tests in air, one multilayer, comprised of a TiN infrared reflector, an Al_0.64Ti_0.36N absorber and an Al_1.37Ti_0.54O top layer, fulfilled the performance criterion (PC) for stability, PC ≤ 5%, for 300 symmetric cycles, each 3 h long, at 600 °C in air [2]. By a slight modification of the deposition parameters, the in-air stability of Al_yTi_1-y(O_xN_1-x)-based coatings could be further improved so that no degradation occurred after 1000 hours of thermal cycling between 300 °C and 700 °C.

W/WAlSiN/SiON/SiO₂ stacks are another solar-selective absorber coating with excellent optical properties. The samples were exposed to heating-cooling cycles between 100 °C and stepwise increased high temperatures of 450 °C, 650 °C, and 800 °C, respectively. In situ RBS revealed full compositional stability of the SSC during thermal cycling. In situ SE indicated full conservation of the optical response at 450 °C and 650 °C, and minimal changes at 800 °C. The analysis of ex situ optical reflectance spectra after the complete thermal cycling gave an unchanged solar absorptance of 0.94 and a slightly higher calculated thermal emittance of 0.16 at 800 °C compared to 0.15 after deposition. Cross-sectional TEM-based element distribution analysis confirmed the conservation of the SSC microstructure after the heating–cooling cycles.

[1] R. Escobar Galindo, M. Krause, K. Niranjan, H. Barshilia, in Sustainable Material Solutions for Solar Energy Technologies (ed. Mariana Fraga, Delaina Amos, Savas Sonmezoglu, Velumani Subramaniam, Elsevier, 2021).

[2] R. Escobar-Galindo et al., Sol. Energy Mater. Sol. Cells 185, 183 (2018).

[3] K. Niranjan et al., Sol. Energy Mater. Sol. Cells 255, 112305 (2023).

Lead-Reduced Halide Perovskite Solar Cells - Predicting the Quality of Photovoltaic Materials with Photo-Assisted Kelvin Probe Force System

Ming-Chung WU

Abstract

As the global energy crisis deepens, driven by escalating demand and the dwindling supply of fossil fuels, the urgency to develop sustainable and efficient energy-harvesting technologies has never been greater. Perovskite solar cells (PSCs) have emerged as a notable solution in the field of photovoltaics, achieving impressive power conversion efficiencies of over 26%. Despite their potential, the extensive use of lead (Pb) in PSCs presents significant environmental and health risks, hindering their widespread commercial adoption. In this presentation, I will detail our research group's strategic approach to enhancing perovskite solar cell technology. We will delve into four critical areas: (1) incorporating metal-doped TiO₂ as the electron transport layer (ETL) in perovskite solar cells; (2) employing carbazole-based bifunctional hole-shuttle interlayers; (3) developing lead-reduced perovskite solar cells; and (4) investigating lead-free Ag₃BiI₆ rudorffite solar cells. Our methodology includes using photo-assisted Kelvin probe force system to evaluate the quality of photovoltaic (PV) materials. A comprehensive understanding of these materials' properties, their manufacturing processes, and long-term performance is essential to assess their quality. Typically, PV materials of higher quality demonstrate lower recombination rates, which could lead to increased efficiencies in solar cell applications. The photo-assisted Kelvin probe force microscopy technique, an advanced version of traditional KPFM with integrated sample illumination, is particularly effective for examining PV materials. This method enables us to analyze surface electron behavior under operational-like conditions for solar cells. Our group is dedicated to leading the advancement of PSC technologies, focusing on achieving high efficiency while upholding environmental safety.

Efficient Electrocatalysts with Multi-elemental single Atom Sites for NH3 production

Pei-Cheng WU

Abstract

Cuprous oxide (Cu₂O) is a p-type metal-oxide semiconductor that has a fundamental, direct energy bandgap of 2.1 eV. It has been suggested to be suitable as a solar cell absorber for a long time but so far device efficiencies have been limited to less than 10% ¹. Cu₂O has also been shown to be suitable for water splitting and CO₂ reduction ². In addition, Cu₂O is interesting as an archetype for the observation of large Rydberg excitons with principal quantum numbers up to n = 25 which have been observed only in naturally occurring Cu₂O single crystals ³. It shouldbe noted that the vast majority of Cu₂O layers obtained by using different deposition methods aren't single crystal or comparable to naturally occurring Cu₂O. Nevertheless, single crystal Cu₂O was obtained in the 1960's ⁴via the high temperature oxidation of Cu in air between 1020°C and 1040°C followed by annealing at even higher temperatures but their optical properties were not investigated. It was shown later that it is possible to obtain Cu₂O on par with naturally occurring Cu₂O via the thermal oxidation of Cu in air at 1050 °C and annealing at 1130 °C after observing excitonic absorption up to n = 5 of the Rydberg series at 2 K ⁵. The growth of Cu₂O via the reaction of Cu with O₂at elevated temperatures is still an active topic of interest and quasi-single crystal Cu₂O was obtained recently via stress assisted thermal oxidation of Cu at 1040°C in air followed by annealing at 1050°C under Ar ⁶.

Here we have carried out a systematic investigation and developed a novel strategy for the high temperature oxidation of copper between 1000-1100°C by employing alternately H₂ and O₂. Initially the temperature is increased at 30°C/min followed by pre-annealing of the metallic Cu at 1040°C, both under H₂, in order to remove excessive O₂ from the metal and promote grain growth. The thermal oxidation of the Cu is subsequently carried out under O₂ at 1040°C after extensively purging with Ar in order to remove H₂and prevent the formation of H₂O. The Cu₂O is subsequently annealed at 1100°C under Ar and cool down is carried out controllably at -5°C/min under a reduced flow of H₂ to suppress the formation of CuO on the surface and inside the bulk of Cu₂O. The Cu₂O crystals obtained in this way have a cubic crystal structure belonging to the Pn3m crystallographic space group with a lattice constant of a = 4.2696Å and are semi-transparent similar to naturally occuring red ruby gems. The structural, electrical and optical properties of the Cu₂O crystals obtained in this way will be presented and their potential for the realization devices dicussed.

¹S. Shibasaki et al., Appl. Phys. Lett. 119, 242102 (2021).

²Y. Zhang et al. Dalton Transactions 50, (2021).

³ T. Kazimierczuk, et al. Nature 514, 343–347 (2014).

⁴R.S. Toth et al., J. Appl. Phys. 31, 1117–1121 (1960).

⁵ S. Mani et al., J. Cryst. Growth 311, 3549–3552(2009).

⁶ M.Xiao et al., Adv. Funct. Mater. 32, 2110505(2022).

Synthesis and evaluation of Co₉S₈/CoS supported on N,S-Co-doped carbon as a bifunctional electrocatalyst for Zn-air batteries

Hyunjin LEE

Abstract

A photo-supercapacitor (PSC) is a device that is the result of the integration of a solar cell with a supercapacitor with high potential to provide energy autonomy.

The SC itself consists of two electrodes and an electrolyte between the two electrodes. The selected cell is a dye-sensitized solar cell (DSSC). This assembly forms a three-electrode system. In this work, ZnMn2O4, LiFeO2 and LiMn2O4 electrodes have been prepared by spray pyrolysis and assembled in a SC with three different electrolytes: Na2SO4 (aqueous), polyvinylpyrrolidone (PVP) and an ionic liquid (gel-type), PVP and LiClO4 (solid-type). In this type of SCs, the pseudo-capacitive character is predominant over the double layer. Regarding the PSC, the main electrical characterization is developed by I-V curve, photocharge curves and the galvanostatic discharge curves.

To switch from SC photocharge mode to capacitor discharge mode using the dye solar cell, an external circuit was used to automatically switch the charge/discharge mode during the light and dark periods. The energy density, and therefore the storage efficiency, of the (photo)supercapacitor is proportional to the device voltage supplied by the solar cell. The device with the best efficiency is the one formed by the dye cell and the DSC/ZnMn2O4/LiClO4+PVP/ZnMn2O4supercapacitor. The devices with an aqueous solution of NaSO4 as the electrolyte were the ones that showed the lowest efficiency. However, DSC/ZnMn2O4-PVP-LiClO4-LiFeO2 had the best conversion percentage. The efficiency values obtained by these capacitors are in the range of those obtained by other authors. However, these results are lower than the values obtained with other types of solar cells, such as those made of perovskites. On the other hand, the supercapacitors used suffer from a decrease in specific capacity compared to what would be expected based on the specific capacity results obtained in a three-electrode electrochemical cell. This is related to the geometry of the supercapacitor itself and the nature of the electrolyte used.

This research was funded by PID2020–117832RB-100 (MCIN/AEI/10.13039/501100011033), Spain

A13_Photovoltaics

Date: 31-05-2024

Time: 08:45-10:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Molecular inks synthesis route shows the pathway for kesterite solar cells with efficiency over 15%

David ROVIRA FERRER

Abstract

The synthesis of multinary semiconductors for solar energy conversion applications such as kesterite (Cu₂ZnSn(S,Se)₄, CZTSSe) is extremely challenging due to the complexity of this type of compounds. Having multiple elements in their structure the formation of secondary phases, punctual or extended detrimental defects, and/or singular interfaces is commonly very problematic. In particular, quaternary kesterite-type compounds are not the exception, and all these detrimental issues explain why during almost 10 years the world record efficiency was unchanged. But, the very recent development of molecular inks route with special precursors, allows the accurate control of single kesterite phase with high crystalline quality. In addition, the use of selective diluted alloying has shown a high potential for minimizing detrimental punctual defects formation, contributing to increase the conversion efficiency record of kesterite based solar cells up to 15% in a short time.

This presentation will be focused first in demonstrating how the molecular inks synthesis route was of key relevance for the control of high quality single phase kesterite, through the modification of the synthesis mechanisms. The relevance of the composition of the ink, the precursor salts, and the interaction between the solvent and the cations in the solution is key for a reliable and reproducible high efficiency kestetite production baseline. Then, diluted alloying/doping strategies will be presented including Cu, Zn and Sn partial substitution with elements such as Ag, Li, Cd or Ge, in CZTSSe. The positive impact of these cation substitutions will be discussed in regards of their impact on the kesterite quality, as well as on the annihilation of detrimental punctual defects, allowing for new efficiency records at 15% level.

Finally, very recent and innovative interface passivation strategies will be discussed, showing the pathway to increase the record efficiency beyond 20%.

Synthesis and Characterization of Lead Halide Perovskites

Júlia MARÍ-GUAITA

Abstract

Inorganic lead halide perovskites (ILHP) are being extensively studied because of their outstanding optical properties (narrow emission, bandgap tunability, and high photoluminescence (PL) quantum yield), interesting for their use in optoelectronic applications (light-emitting materials, photodetector, or solar cells).

In this work, we investigate the structural and optoelectronic properties of CsPbX₃ (X=Cl, Br, I) and CsPb(Br_0.5X_0.5)₃ (X= I, Cl) thin films. The perovskites were synthetized from precursors by mixing them at 70 °C while stirring for 1 hour. Thin films were deposited onto different substrates (fused-silica, silicon and ITO) by spin coating using toluene as antisolvent. The structural properties of the deposited films were studied by X-ray diffraction and field emission-scanning electron microscopy, obtaining the expected perovskite phase for all compositions, although some impurities are also found. Their optical properties present a PL emission and absorption edge (by UV-visible absorption spectrophotometry) accordingly to their nominal composition. For assessing their electrical properties, simple test devices were fabricated on silicon substrates with a top Al-contact. Intensity-voltage curves revealed an ohmic behaviour, with resistances of the order of several MΩ. In future works, a light-emitting devices structure will be fabricated, including transport layers and the perovskite materials hereby synthesized.

Earth-abundant nitride alloys with tuneable functional properties as candidates for top-cell material in tandem solar cells

Vegard Standeren OLSEN

Abstract

Ternary II-IV nitrides represent a group of tuneable semiconductor materials that have potential for impacting a broad spectrum of energy applications, e.g., solar cells, LEDs, and photoelectrochemical cells. Among the ternary nitrides, ZnSnN₂ and ZnGeN₂ show particular promise as an earth-abundant alternative to group-III-nitrides such as GaN and InN. Ternary II-IV nitrides replace the group-III cation with a hetero-valent composition of group-II and group-IV elements resulting in materials with direct band gaps that cover the majority of the visible spectrum. As a candidate for top-cell material in a tandem structure with Si, ZnSnN₂ has an ideal optical band gap of 1.65 eV and can be grown with high crystallinity using magnetron sputtering [1,2]. However, these materials face challenges resulting from degenerate as-grown carrier concentration due to intrinsic defects as well as low carrier mobility, limiting their potential.

In this work, we present ZnSn_xGe_1-xN₂ alloys grown by high-power impulse magnetron sputtering (HiPIMS). The alloys exhibit high crystal quality and a tuneable optical band gap in the range 3.1 eV to 1.65 eV as a function of their composition (x), comparable to previous works [3,4]. In addition to estimating the optical band gap from transmittance measurements, the evolution of the band gap narrowing from ZnGeN₂ to ZnSnN₂ has been studied by combining band gap estimates with ultraviolet photoelectron spectroscopy (UPS) measurements. Importantly, we also report on a composition-dependent carrier concentration, and achieve carrier mobilities as high as >150 cm²/Vs for ZnGeN₂-rich compositions. For the ZnSnN₂-rich compositions exhibiting high carrier concentrations, transmittance measurements in the infrared indicate free-carrier absorption. In conclusion, the ZnSn_xGe_1-xN₂ alloy shows promising functional properties as well as tuneability, enabling property tailoring with potential for use energy applications.

[1] V. S. Olsen, et al., Advanced Optical Materials, vol. 9, no. 16., pp. 2100015, 2015.

[2] V. S. Olsen, et al., Physical Review Materials, vol. 6, pp. 124602, 2022.

[3] P. Narang, et al., Advanced Materials, vol. 26, no. 8, pp. 1235-1241, 2014.

[4] A. M. Shing, et al., APL Materials, vol. 3, no. 7, pp. 076104, 2015.

Rear Surface Passivation for Molecular Ink-Based, Submicron CuIn(S,Se)2 Solar Cells

Sunil SURESH

Abstract

Polycrystalline copper indium gallium di-selenide based solar cells have demonstrated power conversion efficiencies (PCE) of 23.35% for small area devices. The direct bandgap of the material allows for extremely thin absorber layers (<2µm), and the optoelectronic tunability permits applications in multijunction devices, that can overcome the Shockley-Queisser efficiency limit. Theoretically, PCEs of ~46% can be achieved by two-junction tandem devices when the rear, and front sub cell exhibit bandgaps of ~0.94 eV and 1.6 eV, respectively. For the rear cell, copper indium sulfo-selenide (CIS) technology offers low carbon footprint, and device efficiencies up to 19.2%. Further reductions in manufacturing costs can be facilitated through the substitution of widely used vacuum deposition processes to high throughput and affordable solution processing methods. However, many drawbacks such as sophisticated nanoparticle synthesis and stabilization, carbon residuals, and low device efficiencies, are still faced today, prohibiting a wide distribution of the technology. Thus, a key limitation thus far has been the availability of high-efficiency low-bandgap absorber layers that can be deposited by low-cost methods.

Herein, a N-N, dimethyl formaldehyde – thiourea based route was used to fabricate submicron (0.55 and 0.75 μm) CIS films addressing challenges of material usage and manufacturing costs. To mitigate recombination losses at the Mo/CIS interface with high recombination resistance, for the first time, a novel rear contacting structure involving a surface passivation layer and point contact openings was developed for solution processed CIS absorber films. For this, an atomic layer deposited Al2O3 film was used to passivate the Mo/CIS interface and the formation of nanosized spherical precipitates in chemical bath deposition of CdS was used to generate nanosized point openings. The Al2O3 rear passivated solar cells with 0.75 μm thick absorber films demonstrated a fourfold increase in the photoluminescence peak intensity, an average minority lifetime of 14 ns, and an open circuit voltage of 578.4 mV. Notably, active area efficiencies of 14.2%, and 12.0% were obtained by rear-passivated devices with 0.75 μm and 0.55 μm thick absorbers, respectively, which represents the highest reported values for CIS solar cells with absorbers of equivalent thicknesses and ink-based deposition processes. In addition, by using stoichiometric precursor inks, the surface roughness of our absorber layers is effectively reduced, and PCEs are increased. The reduced roughness is crucial to realize monolithically interconnected tandem devices, where perovskite absorbers are directly deposited on the CIS bottom cell. Thus, the void-free, and large grained (~500 nm) absorber films obtained challenge the traditional conceptions of inferior material properties for solution processed absorber films and pave the way for the development of high-efficiency printed solar cells.

A14_Photovoltaics

Date: 31-05-2024

Time: 10:30-12:00

Room: CASSIN - GROUND FLOOR

Click here to have the Symposium details as a pdf

Role of the Defects in the i-ZnO Layer on the Performance and Homogeneity of Kesterite Based Thin Film Solar Cells.

Victoria ROTARU

Abstract

Recent achievements in the record efficiency of kesterite based thin film solar cells allowed to reconsider this promising technology for the possible implementation in various applications. One of the crucial points for the industrialization of kesterite based photovoltaic (PV) technology is achieving homogeneity of the deposited layers. On top of improving pixel efficiency at cell level, it involves ensuring large area uniformity and reproducibility using scalable and industrially compatible fabrication processes. This is essential for the successful scale-up and feasibility of the kesterite technology, enabling its commercialization, thus contributing to the EU's transition towards renewable electrification.

One critical aspect to consider when scaling up any thin film PV technology is the presence of shunt paths, which become crucial when dealing with larger areas, as they determine the overall device performance. In the case of kesterite technology, the intrinsic zinc oxide (i-ZnO) nanometric layer deposited at the buffer/TCO interface plays a vital role by providing isolation between the front and back contacts of the devices.

Taking this into account, this study focuses on evaluating the importance of the i-ZnO protection layer in substrate architectures (SLG/Mo/MoSe₂/CZTSe/CdS/i-ZnO/ITO) during the scale-up of the technology. Particularly, this work explores the effect of i-ZnO thickness on the performance of Cu₂ZnSnSe₄ (CZTSe)-based devices by employing an in-depth combinatorial analysis methodology based on such spectroscopic techniques as photoluminescence (PL) and Raman scattering, along with optoelectronic measurements, using large 5×5 cm² samples with an i-ZnO thickness gradient and a set of discrete samples with higher thickness variations.

The results of the device performance in discrete samples show that increasing i-ZnO thickness improves the devices homogeneity. Thus, the coefficient of variation of the FF is reduced from 16.9 % (25 nm of i-ZnO) to 3.8 % (100 nm) without sacrificing the maximum value, while the V_oc of these samples is improved by 15 mV. Together, these two factors define the PCE distribution of the sample towards a positive reduction in dispersion.

Moreover, the results of PL and Raman spectroscopies show the presence of defects in the i-ZnO layer in all samples, the nature and means of observation of which will be discussed during the presentation. The amount of these defects clearly correlates with the optoelectronic parameters of the solar cells and constitutes an additional factor that influences the device performance. This is due to the presence of a nonlinear dependency between the concentration of defects and the i-ZnO layer thickness, which makes important to understand the defect properties of the i-ZnO layer and how they affect the recombination mechanisms in the upper interface of the PV device. These results show that controlling the i-ZnO layer is a key factor for scaling up the CZTSe technology.

Could agricultural aerosols impact reliability of CIGS thin film photovoltaic cells?

Adèle DEBONO

Abstract

With the development of agrivoltaics, flexible thin film solar cells, some of which are already available in the market, are considered as an interesting alternative to conventional crystalline-Si [1]. To adapt the photovoltaic systems to agricultural environments, it is necessary to ensure their reliability, in particular by adapting the reliability tests considering specific pollution (fertilizers, fungicides, …) related to agricultural activities. In this work for the first-time, the effect of atmospheric aerosol pollutants, here (NH₄)₂SO₄ known as corrosive [4], on the performance and degradation mechanisms of Cu(In,Ga)Se₂ (CIGS) thin film photovoltaic cells [2], [3].

The study was conducted on representative models of 1 or 2 layers (sputtered 500 nm-Mo, co-evaporated 1.5 µm-CIGS, ALD-deposited 50 nm-ZnO and 480 nm-Al:ZnO (AZO) on, all on Glass) and on full solar cells with the architecture Glass/Mo/CIGS/Zn(O,S)/ZnMgO/Al:ZnO/NiAl with and without thin-film encapsulation made of 25 nm ALD-Al₂O₃. The accelerated ageing was performed with temperature and humidity cycles and the daily deposition of a drop of (NH₄)₂SO₄ [2]. The chemical evolution of the samples was characterized by ex-situ and in-situ Raman spectroscopy, XRD, SEM-EDS and GD-OES. The cells' performance was evaluated by I-V curves, resistivity measurements, and spectrophotometry.

When aged without pollutant, the loss of performance of the unencapsulated cells was limited to 40%. It could be explained by the presence of new species, Cu_(2-x)Se and Na_xMo_yO_z, which formation was confirmed by in situ Raman [2] and GD-OES, could act as recombination centers or shunt paths.

In 9 days of the test with (NH₄)₂SO₄, both long term performance and main degradation mechanisms were affected. The conversion efficiency of the cell was reduced by 80%. Main degradation in the presence of pollutant was ascribed to the loss of the conductivity of the contacts (especially of the AZO layer) and optical losses (transparency of the AZO) due to the formation of insulating corrosion products such as zinc hydroxysulphate on AZO, Ni(SO₄).nH₂O on NiAl or MoO₃.nH₂O on Mo, evidenced by Raman. Moreover, thin Al₂O₃ encapsulation, although efficient in damp heat test [5] and in cyclic test without pollutant [3], was partly dissolved with (NH₄)₂SO₄ and lost its protective properties [2], [3].

In conclusion, this work demonstrates that atmospheric aerosols in agricultural environments can significantly affect reliability of thin film solar cells and their presence must be considered for the development of reliability tests for agrivoltaic systems.

[1] Spaes, "Photovoltaic shade for greenhouses", PV Magazine (2020)

[2] Debono et al., Progress in Photovoltaics (2023) doi: 10.1002/pip.3742.

[3] Zhang et al., Progress in Photovoltaics (2021) doi: 10.1002/pip.3527.

[4] Leygraf and Graedel, Atmospheric corrosion (2016).

[5] Zhang et al., Sol. Energy Mater Sol. Cells (2021) doi: 10.1016/j.solmat.2020.110914.

Dipole thin films for advanced charge mediation

Eloi ROS

Abstract

Interface design and modification has been one of the main strategies used for developing Organic, Perovskite and Silicon solar cells in the last few years. Among different interface options, dipole thin films have emerged as a solution to improve both efficiency and stability. An interfacial dipole brings steep shifts in surface workfunction, promoting preferential band alignment and enhancing electron/hole conductivity. The resulting tuning allows to increase charge selective properties as well as decrease specific contact resistance across an interface. This holistic approach to interfaces allows to use the same materials in different semiconductors which could eventually prove to be a useful tool for tandem configurations. However, the origin of the interfacial dipole and its effects on device performance are so far not entirely clear. A broad study of different dipole layers including polar organic molecules (amino acids), Self-Assembled Monolayers (APTES), conjugated polyelectrolytes (PFN, PEI), organic biopolymers (DNA) and dendrimers (PAMAM) have been implemented in Metal/Dipole/Semiconductor junctions to shed light into this yet unknown phenomenon. Photon electron techniques are used for material and interface characterization (Xray/XPS, Ultraviolet/UPS, Electron Energy Loss/EELS…). Electric characterization is done both in Transfer Length Method (TLM) structures to characterize the specific contact resistance at the interface, and in solar cells to observe its effect in finished output photovoltaic parameters such as open circuit voltage (Voc), Fill Factor (FF), and short circuit current (Jsc). Correlations between the presence of specific chemical groups in the films and the dipole strength have been seen which could provide a route to further increase the strength and benefits of these dipole layers.

Unweilling the Growth Mechanism of Quasi-2D Halide Perovskite Thin Films for Solar Cells

Thierry PAUPORTÉ

Abstract

The challenge of fully understanding the growth mechanism of thin films of 2D/quasi-2D organo-metal halide perovskite (MHP) persists.[1-3] Here, we present an extensive investigation aiming at unveiling the growth mechanism and crystallization process of MHP films during thermal annealing as the crucial step of most MHP film preparation. We have combined real time glow discharge optical emission spectroscopy (GD-OES) measurements and in situ GIWAXS technique to investigate the film formation process. They have been completed by ToF-SIMs, PL and NMR measurements. By studying the behavior of solvent molecules, elements, compounds, and phases we have been able to unveil the complex relationship between the evolution of the various phases formed, their growth direction and the direction of solvent removal. Furthermore, we have shown that these evolutions are strongly linked with the partial elimination of the spacer cation in the case of the 2D Ruddlesden-Popper compounds.

This study has allowed us to optimize the additives to be used in the perovskite precursor solution and to enhance the power conversion efficiency (PCE) and stability of the perovskite solar cells based on low dimensional perovskite compounds.[4]

References

[1] D. Zheng, T. Zhu, Y. Yan, and Th. Pauporté, Adv. Energy Mater., 12, 2103618 (2022).

[2] D. Zheng, P. Volovitch, and Th. Pauporté, Small Methods, 18, 2200633 (2022).

[3] D. Zheng, F. Raffin, P. Volovitch and Th. Pauporté, Nature Commun., 13, 6655 (2022).

[4] M. Liu, D. Zheng, T. Pauporté, Adv. Mater. Interfaces (2024) 2300773.

Low-Temperature Solution Phase Synthesis of Inorganic Chalcogenide Perovskites Nanoparticles and Thin Films and Their Characterization

Rakesh AGRAWAL

Abstract

The rise of photovoltaics as a key renewable energy source to combat climate change is evident. Halide perovskites have further fortified this domain due to their outstanding optoelectronic traits and low-temperature facile synthesis. Despite their promise, their reliance on toxic lead and susceptibility to environmental factors such as air and moisture limit their potential. Strategies focusing on lead substitution or encapsulation and other measures to enhance stability persist alongside exploring alternate non-toxic materials sharing similar crystal structures.

Chalcogenide Perovskites emerge as a promising substitute, leveraging non-toxic elements abundantly available in the Earth's crust while exhibiting superior resistance to air and moisture. Preliminary studies and first-principle calculations align their optoelectronic properties closely with halide perovskites. However, the historical synthesis of these materials at extremely high temperatures (over 900°C) has hindered their integration into solar cell applications.

Our research introduces innovative low-temperature growth methodologies for BaMS₃ (M=Zr, Hf) chalcogenide perovskites, establishing a comprehensive framework for phase-pure synthesis of nanoparticles and thin films at lower temperatures. We will present diverse solution deposition techniques supporting this framework, from economic metal salt precursors to high-purity organometallic compounds. Notably, our work demonstrates one of the most homogeneous BaZrS₃ films, promising advancements in exploring these compounds for photovoltaic and other electronic applications. We will present the current published^1-4 as well as the most recent unpublished results related to the synthesis and material and optoelectronic characterization of these important and promising class of semiconductors.

1. J. W. Turnley, K. C. Vincent, A. A. Pradhan, I. Panicker, R. Swope, M. C. Uible, S. C. Bart, R. Agrawal, “Solution Deposition for Chalcogenide Perovskites: A Low-Temperature Route to BaMS₃ Materials (M = Ti, Zr, Hf)”, Journal of American Chemical Society, 144, 18234 (2022)

2. A. A. Pradhan, M. C. Uible, S. Agarwal, J. W. Turnley, S. Khandelwal, J. M. Peterson, D. D. Blach, R. N. Swope, L. Huang, S. C. Bart and R. Agrawal, “Synthesis of BaZrS₃ and BaHfS₃ Chalcogenide Perovskite Films Using Single-Phase Molecular Precursors at Moderate Temperatures”, Angew. Chem. Int. Ed. 62, e202301049 (2023)

3. K. C. Vincent, S. Agarwal, J. W. Turnley, and R. Agrawal, “Liquid Flux Assisted Mechanism for Modest Temperature Synthesis of Large-Grain BaZrS₃ and BaHfS₃ Chalcogenide Perovskites”, Advanced Energy and Sustainability Research, 2300010 (2023).

4. S. Agarwal, J. W. Turnley, A. A. Pradhan, and R. Agrawal, “Moderate Temperature Sulfurization and Selenization of Highly Stable Metal Oxides: An Opportunity for Chalcogenide Perovskites”, Journal of Materials Chemistry C, 11, 15817 (2023).

AP01_Poster Session

Date: 28-05-2024

Time: 16:30-18:30

Room: ETOILE - FIRST FLOOR

Click here to have the Symposium details as a pdf

01_1060 Electrodeposition of metallic bismuth catalyst from aqueous media on Mxene support: Morphology and electrochemical study

Sherina HARILAL

Abstract

In this project, ultra-thin Bi (bismuth) plate-like structures were pulse-electrodeposited on Stainless-steel dip coated Ti₃C₂Mxene (SS/Mx) support for electrocatalytic reduction of CO₂to formate. The SS/Mx, which has a large surface area, conductivity, and stability, is an ideal support material for metal nanoparticles. Bi, a favorable catalyst for selective formate production, exhibits a current density lower than 10 mA/cm² in aqueous electrolytes to achieve high Faradaic efficiency. Depositing ultra-thin Bi catalyst with sharp edges on SS/Mx enhanced the electrode's electrocatalytic surface area (ESCA) and current density for electroreduction of CO₂. Dipping the SS/Mx/Bi electrode in the Nafion binder improved the stability of the catalyst. The electrodeposited Bi catalyst on SS/Mx support performed a high catalytic activity with formate Faradaic efficiency reaching 98.92% and a current density of 25 mA/cm² at -0.8 V vs. RHE. SS/Mx electrodes with plate-like Bi catalysts are favorable for high-efficiency CO₂ reduction to formate.

02_1204 Harnessing the Potential of PEDOT:PSS-Infused Graphene for Enhanced Front Electrodes Performance

Maria Isabel RODRIGUEZ

Abstract

Nowadays, silicon-heterojunction (SHJ) solar cells emerge as a reliable low-temperature and high-efficiency solution, where new architectures of electrodes to generate and extract the current in a more efficient way are being required. This technology exhibits high electrical resistance emitters, having need of a transparent conductive front electrode (TCE) for their optimal performance. The conventional choice is a transparent conductive oxide (TCO), typically 80 nm-thick indium tin oxide (ITO) that also plays an antireflective role, showing sheet resistances close to 120 Ω/sqr. However, the scarcity of indium gives rise to the search for new materials to replace it, turning into a hot topic. Given the extraordinary properties of graphene, it emerges as a compelling candidate to improve the electrical properties of such front electrodes. The use of graphene materials and their derivatives has recently sparked considerable interest in photovoltaics, owing to their outstanding characteristics and significant potential for innovation. On the other hand, the efforts describe above to replace ITO by a new class of materials, which are easier to handle and more cost-effective, can also include the use of polymers, as can be the case of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). This polymer has drawn most of the attention due to its relatively high conductivity and remarkable stability in ambient conditions compared to others, as well as its potential to be transparent in the visible spectrum.

Taking above mentioned into account, this work aims to demonstrate the potential of graphene coupled with that of PEDOT:PSS to achieve TCEs with enhanced electrical properties. For this purpose, graphene dispersions were prepared, incorporating PEDOT:PSS in 1,2-dichlorobenzene, to be deposited by spin coating onto corning glass and silicon substrates. Spin-coating technique, known for its deposition speed, cost-effectiveness, and ease of handling, proves to be more efficient compared to alternative thin film deposition methods. We present the structural, electrical and optical properties of the final thin film electrodes, characterized through RAMAN analysis, four-point probe electrical measurements and Hall effect measurements, and UV/VIS/NIR spectrophotometer. The results show the control of the electrical character and properties thanks to the incorporation of graphene into the dispersion, resulting in clearly opened possibility of a noticeably improvement of TCEs and therefore to further enhance SHJ contact-technology performance.

Acknowledgements: MEDIDA C17.I2G: CIEMAT. Nuevas tecnologías renovables híbridas, Ministerio de Ciencia e Innovación, Componente 17 “Reforma Institucional y Fortalecimiento de las Capacidades del Sistema Nacional de Ciencia e Innovación” funded by the European Union – NextGenerationEU; and Grant PID2020-114234RB-C21 funded by MCIN/AEI/ 10.13039/501100011033.

03_1212 Overview of the Use of Advanced Materials especially Thin Films for Energy Transition

Xenia KNIGGE

Abstract

The energy transition is the global hot topic of our time. But how could it be achieved? One question is which materials play a central role in energy transition. As key elements cobalt, copper, graphite, lithium, neodymium, and nickel are considered. But the mining of these elements sometimes entails major environmental risks. So, the question arises if there are possibilities to substitute these materials by something more sustainable. Here advanced materials come into play. Advanced materials are a heterogeneous group of materials that are rationally designed to have new or enhanced properties, and/or targeted or enhanced structural features [OECD working description].

Thin films as advanced materials are believed to play a central role in providing technical solutions to support the transformation towards a more sustainable society. The reason for this important role is that the surface has a major influence on a variety of material properties. In fuel cells or batteries, the influence on contact and transition resistance plays an important role, in wind turbines the corrosion behavior or temperature resistance is a major issue. Optical properties such as absorption, transparency and reflection are important when using solar energy. All these properties can be advantageously influenced by the clever use of thin films. Typical examples for the use of thin films in energy transition are ceramic nano coatings on solar cells, catalytically effective coatings for H2 production, PVD coatings on rotor blades in wind turbines to protect against environmental influences. Also, the application in photovoltaics can be named and the construction of modern solar cells from various thin layers such as heterojunction cells (HTJ) or perovskite cells or a combination in tandems. The use of these thin layers allows a significant increase in efficiency, but here for example at the cost of a shorter lifetime and the use of the harmful element lead. To estimate the risk for the environment and the human health, the entire life cycle must be considering. In the end, the safety and sustainability is crucial for the successful use of advanced materials in general and thin films in particular in energy transition. Therefore, an overview on advanced materials relevant for technologies to support the energy transition is developed. This poster will present first results of this work with a focus on thin films.

The project is funded by the German Environmental Agency (UBA) under the project number 183352.

04_1255 Control of Side Reactions at the Cathode/Electrolyte Interface in Sulfide-Based All-Solid-State Batteries via Dry Process coating

Dae Ik JANG

Abstract

Lithium-ion batteries, despite their lightweight and high energy density, present safety concerns due to the flammable nature of the organic electrolytes used, leading to potential explosions and fires. A promising solution to enhance safety involves replacing these flammable organic electrolytes with non-flammable solid electrolytes. Among them, sulfide-based solid electrolytes are particularly attractive for all-solid-state batteries due to their ductility and high ion conductivity. However, challenges arise from their narrow electrochemical stability window, especially when coupled with high-voltage transition metal oxide cathodes. This pairing can result in the decomposition of sulfide-based solid electrolytes into undesired byproducts. To address this issue, it becomes imperative to establish a thin and uniform coating layer on the cathode surface. Presently, expensive source materials like Nb and Ta are utilized for this purpose. Unfortunately, the use of solvents in the coating process has notable adverse effects on both the environment and the economy. This study aims to innovate by coating the cathode surface with Li_xB_yO_z through a dry process. This coating layer functions as a uniform passivation layer at the cathode-electrolyte interface, bolstering interfacial stability and controlling unwarranted side reactions such as electrolyte oxidation and cathode/electrolyte mutual diffusion. An additional advantage of this method lies in its use of a low-cost boron source without the need for solvents. This approach not only addresses environmental concerns but also presents a more economically efficient way to coat cathode surfaces. To assess the efficacy of this coating layer, we conducted a comprehensive analysis of electrochemical properties and provided supporting evidence of the coating effects through techniques such as X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The outcomes of this study offer insights into advancing the safety and performance of lithium-ion batteries through innovative cathode surface coating techniques.

05_1277 Effect of modulating the valence band maximum grading around the surface of Cu(In,Ga)Se2 for hydrogen generation

Kana UEDA

Abstract

Photoelectrochemical (PEC) hydrogen production, which utilizes solar energy to split water, is a promising method for hydrogen energy production using decarbonization. Although a narrow bandgap in the photoelectrodes is necessary to capture a wide range of the solar spectrum, the energy potential of the bandgap should also be aligned with the redox potential. Chalcogenide Cu(In,Ga)Se₂ (CIGS) has an appropriate bandgap range (1.0–1.7 eV), which is, theoretically, capable of generating a photocurrent of approximately over 30 mA/cm². Thus, it is a promising material for photoelectrodes [1]. However, the valence band maximum (VBM) position of CIGS is lower than the oxygen redox potential for hydrogen generation. Therefore, to modulate the VBM, Cu-poor phase (Cu-poor-CIGS) was focused on which has a deeper VBM than CIGS. In addition, to modulate the VBM grading around the surface of the CIGS photoelectrode using Cu-poor-CIGS, hydrogen generation can occur keeping optical wavelength to enable absorption. This study investigates the effect of modulating the VBM grading around the surface of CIGS photoelectrodes on hydrogen generation.

Polycrystalline CIGS thin films were deposited using the evaporation method [2]. In addition, In and Se were deposited on the CIGS to form Cu-poor-CIGS/CIGS structure. Owing to the use of the Cu-poor-CIGS/CIGS photoelectrode, the photocurrent density and photovoltage increased, compared with only CIGS photoelectrode. This result suggests that the Cu-poor-CIGS around the surface of the CIGS photoelectrodes contributed to the enhancement of hydrogen generation.

[1] K. Ueda and M. Sugiyama, J. Phys. D: Appl. Phys. 57 (2024) 135103.
[2] A. M. Gabor, et al., Appl. Phys. Lett. 65 (1994) 198.

06_1442 Biomimetic Super-Foldable Composite Film Electrodes Enabled by Responsive Stress Dispersion

Guangtao ZAN

Abstract

Developing both super-foldable and high-energy storage electrodes is critical yet challengingfor flexible electronics and wearable technology. Addressing this challenge, our study presents a brand-new freestanding film cathode, super-foldable C-fiber@NiS-cockscomb (SFCNi), inspired by the complex structures found in silkworm cocoons and cockscomb petals. Thanks to its unique biomimetic structures, the SFCNi cathode demonstrates remarkable endurance, sustaining over 100,000 cycles of true-folding without the usual drawbacks of composite fiber fractures, loss of functional materials, conductivity decline, or compromised electrochemical performance. Real-time SEM observation and mechanical simulations of folding process are used to provide critical insights into the folding dynamics of the electrode. Our findings reveal that atomically-thin wrinkled NiS resembling cockscomb petals can flexibly deform to accommodate bending stress, while the 3D network SFCNi gradually generates a "ε-shaped" folding structure similar to cuit cocoon at the crease, effectively managing stress during bending. Particularly, the SFCNi is intelligently responsive to varying bending degrees by selectively deforming to mitigate stress concentrations and localized deformations. This responsive stress-dispersion not only maintains the chemical bond integrity but also prevents material fractures, thus endowing the material with exceptional super-foldability. This study not only advances our understanding of electrode folding dynamics but also introduces a novel biomimetic approach to the fabrication of super-foldable composite electrodes, paving the way for future innovations in the design of integrated multi-functional super-foldable devices and offering a significant leap forward in the field of flexible electronics.

07_1700 Efficient Intercalation of Al Ions in Electrochemically Activated Mn3O4 for Rechargeable Aqueous Aluminium Ion Batteries

Lalit BHARTI

Abstract

The high theoretical capacity and volumetric energy density of aluminium ion batteries (AIBs) is making them attractive for large-scale energy storage applications. However, the practical realization of aluminium ion battery devices is impeded due to the frequent collapse of the structure of the cathode materials. It is shown that this problem can be solved by a conventional material i.e. Mn₃O₄. This material can be used as a cathode in aqueous aluminium ion batteries. It can deliver specific capacity, rate capability, and cycling stability. The various salts of aluminium were used as an electrolyte to establish the feasibility of Mn₃O₄ to facilitate Al³⁺ intercalation/deintercalation. In AlCl₃ aqueous electrolyte, Mn₃O₄ based cathode exhibits the highest initial discharge capacity of ~ 268 mAh g^-1, at a high current density of 0.5 A g^-1, with an excellent capacity retention and rate capability. This is amongst the best cathode performances reported for aqueous AIBs. AlCl₃ aqueous electrolyte also exhibits superior benefits than Al₂(SO₄)₃ and Al(NO₃)₃ aqueous electrolytes in terms of offering higher Al³⁺ storage capacity in Mn₃O₄. The performance improvement as a function of cycling in attributed to the in operando transition of Mn₃O₄ to layered MnO₂. The reasons why Mn₃O₄ must be used instead of MnO₂ is also explained.

08_1720 Combinatorial thin film deposition of iron alloyed SnWO4 with pulsed laser deposition

Ingvild BERGSBAK

Abstract

Continuous composition spread pulsed laser deposition (CCS-PLD) is a combinatorial deposition technique that enables growth of functional thin films with either vertical or horizontal composition gradients. Conventional CCS-PLD alternates between targets of different composition to achieve the gradient in the film. The introduction of segmented targets eliminates the need for time-consuming target exchanges during deposition, significantly speeding up the process and accelerating the pace of material discovery [1]. The composition gradient of the film enables efficient, high-throughput characterization of relevant material parameters for identification of optimal composition for specific applications.

In this work, the indirect band gap semiconductor α-SnWO4 alloyed with Fe has been studied. Structural and electronic properties have been investigated and their dependence on the Fe content have been explored. Pure α-SnWO4 has a band gap ̴1.9 eV and is considered as a candidate for photoelectrochemical cells [2]. It is hypothesized that the band gap can be narrowed by alloying, by e.g., Fe. If the band gap can be narrowed to around 1.7 eV, it may also be a potential top cell absorber material in tandem with a Si bottom cell [3]. Potential top cell absorber materials should, in addition to a band gap of 1.7 eV, have good absorbing properties, carrier concentration below 1017 cm-3, high mobility and high carrier lifetime. Fe alloyed α-SnWO4 will be grown with CCS-PLD, and the combinatorial film will be used to screen a range of compositions as potential top cell absorber material candidates.

The goal of the project is twofold: identification of potential top cell absorber materials for Si-based tandem solar cells and further development of the CCS-PLD technique.

References

[1] M. Lorenz, H. Hochmuth, H. von Wenckstern, and M. Grundmann, Rev. Sci. Instrum. 94, 083905, doi: 10.1063/5.0142085 (2023).

[2] M. Kölbach, I. J. Pereira, K. Harbauer, P. Plate, K. Höflich, S. P. Berglund, D. Friedrich, R. van de Krol, and F. F. Abdi, Chem. Mater. 30, 22, pp. 8322–8331, doi: 10.1021/acs.chemmater.8b03883 (2018).

[3] T. Todorov, O. Gunawan, and S. Guha, Mol. Syst. Des. and Eng. 1, 4, pp. 370–376 doi: 10.1039/C6ME00041J (2016).

09_1803 Characteristics of the absorption layer according to the length controlled SAMs molecular arrangement state and the characteristics of 2-terminal CIGS/Perovskite solar cells

Hyo Jeong JO

Abstract

The efficiency of perovskite solar cells (PSCs) with a P-I-N structure is no longer achievable due to limitations in charge selection. In order to overcome efficiency limitations and be applied to tandem solar cells, interface engineering techniques for electron transport (ETL) and hole transport (HTL) layers have the potential to significantly improve the efficiency of solar cells. While many studies are currently underway, especially the interfacial engineering techniques for hole extraction in particular have received little attention until now. This paper shows that the molecular form that can be controlled at the interface self-assembling monolayers (SAMs) were presented. Depending on the interface arrangement of the SAM, not only does the crystallization form of the perovskite absorber layer vary, but it also affects the hole extraction rate. The molecule is based on carbazole moiety with a variety alkyl length and can form self-assembling faults (SAMs) from various oxides. The SAMs are designed to produce an energetically aligned interface with the perovskite light-absorbing layer without the need for a reduction in efficiency due to specific radiation. To investigate the effects of different groups on the photophysical, electrochemical, hole extraction, and bulk properties such as photovoltaic efficiency of p-i-n perovskite solar cells. In this study, not only the device effect of the perovskite solar cells but also the photovoltaic performance of the 2-terminal tandem solar cell were confirmed.

10_1882 Dendrite-free Zinc Anodes: Exploring Polar-Face-Rich 2D ZnO Interfacial Layers for Rechargeable Zn-Ion Batteries

Hu XUEQING

Abstract

Zinc metal holds promise as an anode material for zinc-ion batteries (ZIBs), but its widespread adoption is impeded by the growth of dendrites in aqueous electrolytes. Dendrites lead to undesirable side reactions, including hydrogen evolution, passivation, and corrosion, resulting in decreased capacity over extended cycling. This study addresses this challenge by directly cultivating 1D zinc oxide (ZnO) nanorods (NRs) and 2D ZnO nanoflakes (NFs) on Zn anodes, creating artificial layers to enhance ZIB performance. The incorporation of ZnO onto the anode provides both chemical and thermal stability, leveraging its n-type semiconductor nature to facilitate the formation of ohmic contacts. This ensures efficient electron transport during Zn ion plating and stripping processes. Consequently, ZnO NFs-coated Zn anodes exhibit significantly improved charge storage performance, achieving 348 mAh g-1, compared to ZnO NRs (250 mAh g-1) and pristine Zn (160 mAh g-1) anodes when evaluated in full cells with V2O5 cathodes. A notable advantage of ZnO NFs lies in their highly polar surfaces, fostering strong interactions with water molecules and rendering them exceptionally hydrophilic. This characteristic enhances the desolvation of Zn2+ ions by ZnO NFs, contributing to improved charge storage performance. Overall, this study underscores the promising potential of 2D ZnO nanostructures as effective coatings for Zn anodes, advancing the development of high-performance ZIBs with enhanced cyclability and capacity retention.

11_1910 Hydrogen permeation barrier coatings: preliminary results on the development of oxide coatings through chemical vapor deposition

Francesca VISENTIN

Abstract

In the framework of hydrogen exploitation for green energy production, it is pivotal for safe and effective H₂ production, storage, and delivery, to develop hydrogen permeation barrier (HPB) coatings able to prevent the hydrogen embrittlement (HE) of metallic pipelines and tanks.

Among various materials, alumina (Al₂O₃) is a promising barrier material because of its low hydrogen permeability, high thermal and chemical stability, and hardness. However, the coefficient of thermal expansion of alumina is lower than that of the metal constituting the material of the infrastructure for hydrogen storage and transport, typically steel. This can cause stress and/or defects in the barrier layer, consequently limiting its blockade properties. One strategy to alleviate the thermal mismatch is the insertion of an inter-layer of another material, having an intermediate thermal expansion coefficient between that of the metal and alumina. Compared to the single-layer counterparts, such materials often perform high hydrogen permeation reduction factor (PRF) because they form a barrier film that can simultaneously take advantage of the properties of the different materials and the interface can further increase the resistance to hydrogen permeation, acting as a hydrogen trap. Moreover, in the presence of nano-multilayers, the tendency for the formation of grains with a columnar structure, which are generally preferential routes for the diffusion of hydrogen, is strongly reduced. Titania (TiO₂), having a thermal expansion coefficient intermediate between that of alumina and steel, can improve the adhesion of the Al₂O₃ film to the metal substrate.

In this preliminary study, TiO₂/Al₂O₃ composite films were deposited employing metal-organic chemical vapor deposition (MOCVD) technique. The MOCVD method can be used to prepare single layers, as well as for multilayer systems. Preliminary chemical, morphological, and structural characterizations of deposited composite materials were carried out. Moreover, the life cycle assessment (LCA) was carried out to highlight the environmental hot spots of the procedure.

12_1922 Graphene metamaterials for advanced Si nanophotonic applications

Yunyi YANG

Abstract

Metamaterials are artificially designed and structured materials with subwavelength inclusions and strikingly unconventional properties at optical frequencies. Graphene-based 2D materials have demonstrated extraordinary optical, electronic, and thermal properties and enabled various applications in energy harvesting, photodetectors, and light-emitting and optical communication devices. Recent advances have shown that metamaterials consisting of graphene and dielectric layers demonstrate superior optical behaviours, which are desirable to address these challenges. For Si photovoltaic applications, an interface modification by a graphene coating is inferior if the 2D layers do not conformably encapsulate the 3D Si nanostructures, since it is important to suppress the reflection and recombination loss at the Si–air interface to the maximum extent, especially from the sidewalls and bottom surfaces. In the meantime, a large-area uniform coating with a thickness accuracy on a nanometer scale is another essential requirement to achieve a tailored antireflection effect. However, conventional mechanical exfoliation and deposition methods with complicated transfer processes fail to fabricate uniform films on high-aspect-ratio 3D structures, especially for perpendicular sidewall areas. Other coating methods based on the typical semiconductor technology, such as PECVD and atomic layer deposition (ALD), require sophisticated semiconductor deposition, are complicated and are not applicable to the demanded graphene metamaterials. Meanwhile, solution-based exfoliation methods, such as dip coating and spray coating, can only result in a suspended film over the Si nanostructures due to their superhydrophobic nature.

Here we present the concept of a 3D conformal coating using graphene metamaterials (GM), which enables in situ conformal coating of GM onto the complex 3D curvature of silicon nanostructures and textured Si solar cells via our successfully developed liquid-phase layer-by-layer approach with monolayer control accuracy. GMs, which are artificially structured materials with alternating graphene and dielectric layers, are designed and demonstrated to attain high optical modulation and electrical response. This particularly designed and constructed multilayer GM structure can realize monolayer thickness control with scalability, which is appealing for energy-harvesting and other nanophotonic applications.

13_1955 Synthesis of thin-film multilayers by magnetron sputtering at room temperature.

Hassan BENAIT

Abstract

Magnetron sputtering represents a thin-film deposition technique within the domain of physical vapor deposition methods, acknowledged for its widespread application on an industrial scale. Its foundational principle involves the controlled bombardment of a target, called cathode, by argon ions (Ar⁺). These ions, generated through the ionization of argon gas within a deposition chamber under the influence of a potential difference with a substrate, transfer their momentum to the target atoms, expelling them towards the substrate. This ongoing process culminates in the formation of a thin film endowed with precisely defined physico-chemical properties.

Magnetron sputtering manifests in two prominent modes: the elemental sputtering mode and the compound sputtering mode. In the elemental mode, a neutral atmosphere, typically comprising argon, is employed for the deposition of thin metal films. Conversely, in second mode, the introduction of reactive gases, such as nitrogen (N₂) or dioxygen (O₂), facilitates the deposition of compound films, including nitrides or oxides.

In our research, the primary focus lies in the synthesis of thin films on a silicon substrate (100) at room temperature, utilizing a sputtering machine equipped with three cathodes. This distinctive configuration allows for the continuous superposition of multiple layers of material without interruption between intermediate layers. During the elemental mode, we synthesize thin metallic layers of silver (Ag) and titanium (Ti). In compound mode, our emphasis is on the synthesis of oxides, encompassing silicon dioxide (SiO₂) and hafnium oxide (HfO₂), as well as nitrides, specifically silicon nitride (Si₃N₄) and aluminum nitride (AlN). Ultimately, we will illustrate an example of stacking, starting with a thin layer of silver, followed by the superposition of N layers of oxides and nitrides. Precise monitoring of thickness, composition, and optical properties across various layers is achieved respectively through the use of a stylus profilometer, transmission electron microscopy, and Fourier transform infrared spectrometry.

14_2353 GeS Crystalline Thin Films for High-Performance Visible Range Photodetectors

Audrius DRABAVICIUS

Abstract

Germanium monosulfide (GeS) in the past few years gained significant attention from the scientific community as a promising 2D semiconductor material, because of its excellent optical and electronic properties, high stability in harsh environments and potential applications for various optoelectronic devices. Previous works on GeS photodetectors were mainly focused on the synthesis of nanocrystals and nanoribbons following exfoliation of nanostructures and device fabrication. However, the reports of polycrystalline GeS thin film device is still lacking. Our research suggests the approach to the synthesis of crystalline GeS thin films for photodetection applications.

GeS thin films were deposited via the close space sublimation (CSS) method onto commercial platinum interdigitated electrode (IDE) substrates. Subsequent annealing was used to facilitate crystallization of the predeposited layers. By systematically adjusting the deposition and annealing parameters we synthesized films with different crystalline texture coefficients. Subsequently we performed structural analysis, charge carrier dynamic studies and intensity dependent current-voltage measurements enabling determination of responsivity and detectivity parameters. Responsivity measurements were performed under 532nm laser illumination, revealed a wide range of R from 0.001 to 2 A/W for different samples, showcasing the influence of crystalline texture on responsivity. Remarkably, detectivity values spanned orders of magnitude, ranging from 1·10¹⁰ to 9·10¹²Jones, with variations attributed to the diverse crystalline structures achieved. All measurements were conducted at a modest 1V bias.

The measured detectivity (D*) values of synthesized GeS thin-film photodetectors are very similar and even outperforms some of the reported devices fabricated using monocrystalline GeS flakes or nanocrystals with the reported D* values for GeS photodetectors spanning from 1.1·10¹¹ to 1.74·10¹³ Jones [1]. Compared to devices fabricated from other transition metal chalcogenide 2D materials such as widely studied MoS2 our device detectivity is higher, the former reporting D values ~1·10¹¹ [2].

This study explore the potential of crystalline GeS thin films as a candidate for photodetection application. High responsivity and detectivity values indicate the significant potential of GeS thin-film photodetectors of visible spectra. The results suggest the need for further investigation, positioning GeS thin films as strong candidates for improving optoelectronic technologies.

[1] Solution synthesis of GeS and GeSe nanosheets for high-sensitivity photodetectors. Ramasamy, P., Kwak, D., Lim, D.-H., Ra, H.-S., & Lee, J.-S. (2016). Journal of Materials Chemistry C, 4(3), 479–485.

[2] High Detectivity and Fast MoS2 Monolayer MSM Photodetector. Singh, R., Patel, C., Kumar, P., Dubey, M., Sriram, S., and Mukherjee, S. ACS Applied Electronic Materials 2022 4 (12), 5739-5746.

15_2383 Fully printed energy storage devices on cellulose-based substrates: An eco-friendly approach for low-cost and disposable Smart electronics system

Elena PALMIERI

Abstract

The integration of electronic devices into wearable applications has revolutionized the way we interact with technology. What makes it even more remarkable is the utilization of sustainable materials that align with the principles of environmental consciousness. In this context, we propose the fabrication of an energy storage device via screen printing, prepared following a ‘‘green approach’’, starting from the substrate used for its fabrication, i.e., cellulose-based materials, to the material used as both electrolyte and interlayer, i.e. sodium-alginate water-based solutions.

The use of cellulose-based polymers as a substrate has great potential given that they are extensively used in the pharmaceutical industry, food sector and electronics and are commercially available in a vast range of molecular weights and substituents. However, there are still limitations associated with the integration of such materials in electronic processes, as they can be easily degraded if exposed to strong chemicals and are typically susceptible to water. To address these challenges, we employed common copy paper as a reference material and fabricated a novel cellulose-based material prepared with Ethyl Cellulose (EC). The EC substrate, produced via solvent casting from a polymer solution, owns good transparency and tuneable mechanical properties depending on the solvent used for the solution preparation. Films prepared from toluene solution exhibit superior mechanical properties (up to 12% elongation), at the expense of the eco-friendliness of the process. On the other hand, those obtained from ethanol, which represents a greener alternative, show inferior mechanical characteristics (up to 1% elongation). However, solutions prepared with butanol, butyl acetate, and ethyl acetate, offer viable and sustainable alternatives, with mechanical properties close to those obtained with toluene dispersions. Regardless of the solvent used, the EC substrate exhibits exceptional resistance to alkali and water, demonstrating complete hydrophobicity. The electrode component of the supercapacitor is carbon based, and the calculated surface area of the carbon ink is 2.7 m²/g. The use of sodium alginate water-based solutions as both electrolyte and interlayer (between the electrolyte and the carbon-based electrode) stands out as a remarkable advancement in terms of process sustainability. Sodium alginate, derived from renewable sources, offers high ionic conductivity and film-forming capabilities. By utilizing sodium alginate solutions at different concentrations as both the electrolyte and interlayer, the need for additional materials is minimized, simplifying the fabrication process, and reducing the device's ecological footprint. The obtained interdigitated supercapacitor has a power in the order of µW/cm².

This approach paves the way for the development of eco-friendly, personalised, and low costs smart electronics that seamlessly integrate with our everyday lives.

16_2448 Exploring the Dynamics of Formation of Pulsed Laser Deposited Halide Perovskite through In-situ Photoluminescence at High Deposition Rates

Vojtech KLINER

Abstract

Metal halide perovskites (MHPs) have garnered significant scientific interest due to their outstanding optoelectronic properties and high efficiencies in solar cell photoconversion. The development of MHPs has relied primarily on solution-based methods as the growth techniques. Although physical vapor deposition (PVD) techniques have been explored less (with the exception of co-evaporation), they present unique advantages in terms of conformal growth and precise control over film uniformity and thickness – factors critical for upscaling and incorporating thin films in heterostructures such as tandem solar cells.

Pulsed laser deposition (PLD), though less common among PVD techniques for solar cells, is noteworthy for its unique ability to deposit complex chemical compositions from a single source in one step. Based on this, PLD provides unique deposition flexibility for investigating a large range of MHP compositions and tune the deposition thickness and rate.

To gain insights into the MHP evolution during growth, our research employs in-situ photoluminescence (PL) measurements during the PLD growth of MHP. Monitoring PL evolution provides insights into the material quality and defect formation processes. We present an analysis of PL evolution during the fabrication of thin films by PLD, with deposition rates ranging from 5 nm/min to 80 nm/min. Our findings reveal a striking similarity in the PL intensity evolution across this range of deposition rates, indicating that the underlying mechanisms of perovskite formation are not significantly altered by the enhanced deposition rate. These findings demonstrate the feasibility of faster deposition rates with PLD, which is a key factor in increasing the throughput of vapor deposited MHPs. Furthermore, we observed that the most pronounced changes in PL intensity occur at the very beginning of the deposition. This early-stage evolution is likely attributable to the coalescence of perovskite grains and the consequent formation of defects at grain boundaries. Beyond a certain film thickness, the PL signatures stabilize and do not exhibit significant variations.

In light of these findings, our future research will focus on investigating the initial stages of perovskite film growth, aiming to control nucleation and grain coalescence processes better. Achieving this precise control will allow the fabrication of high-quality films in shorter times using a vapor deposition technique.

17_245 Magnetoelectric BiFeO3-PbiTO3 thin films on Ni substrates for flexible energy harvesting devices

Adriana BARRETO

Abstract

The miniaturization of multiferroic devices from bulk technologies into thin film ones is crucial due to several reasons. Smaller scales not only reduce material usage and production costs, they also enable higher device integration on a single chip. Also, boosting sensitivity in capturing smaller magnetic stimuli could be achieved, expanding their potential from sources previously inaccessible at larger scales. In order to fabricate multifunctional metallic Micro Electro Mechanical Systems (MEMS), such as dual-source energy harvesters, simple and cost-effective methods are needed to integrate ferroelectric perovskite oxides into active metallic substrates. In the context of magnetic base metals, nickel stands out as an excellent choice, due to its magnetostrictive properties and wide commercial availability. Meanwhile, BiFeO₃-PbTiO₃ (BFO-PTO) solid solution was selected as the ferroelectric layer because of its dielectric behavior and high piezoelectric response. This system exhibits an enhancement of these coefficients at the Morphotropic Phase Boundary (MPB), where both rhombohedral and tetragonal polymorphs coexist. Also, the system shows low ferroelectric/ferroelastic domain wall activities and a high Curie temperature.¹ The main difficulty remains in finding suitable conditions for depositing this lead-containing ferroelectric system on metallic Ni without unwanted chemical reactions, as Ellingham diagrams show that there is not a processing window of temperature and PO₂ where the reduction of PbO and the oxidation of Ni can occur without one interfering with the other. Several strategies have been explored to lessen the effects of this low-κ parasitic interfacial nickel oxide, as it diminishes the overall capacitance, where it functions as a series capacitor element. In this study, a flexible magnetoelectric heterostructure was fabricated by the solution deposition of MPB BiFeO₃-PbTiO₃ film on a flexible Ni foil, studying the effect of buffer La_0.7Sr_0.3MnO₃ (LSMO) conductive layers. This interlayer, strategically positioned within the heterostructure, would play a dual role: firstly, acting as an interdiffusion barrier, and secondly, serving itself as bottom electrode. Simultaneously, we have investigated the possibility of kinetically limiting the formation of nickel oxide at the film-nickel interface by taking advantage of recent advances in low-temperature solution processing of ferroelectric thin films. The resulting films have enhanced ferroelectric properties and showed a ME voltage coefficient of 40 mV·cm^-1·Oe^-1, due to a better interfacial bonding among the heterostructure. This study contrasts these new system responses with prior findings documented by the research group and those available in the literature.

[1] L. Zia et al., J. Am. Ceram. Soc., 2022, 105, 888–900.

Funded by the Spanish Projects TED2021-130871B-C21/AEI/10.13039/501100011033/Unión Europea Next-GenerationEU/PRTR and PID2022-136790OB-I00/AEI/10.13039/501100011033

18_2547 Interfacial DMI Characterization in Sputtered Terbium Iron Garnets Thin Films

Stefano FEDEL

Abstract

Chiral magnetic structures have attracted great interest owing to their intriguing and potential applications in next-generation magnetic technologies. At the heart of chiral magnetism lies the Dzyaloshinskii-Moriya interaction (DMI), an antisymmetric exchange interaction arising from the spin-orbit coupling in structures with broken inversion symmetry [1]. DMI promotes the perpendicular alignment of neighboring spins and gives rise to exotic magnetic textures such as skyrmions [2] and chiral Néel domain walls (DW) [3]. DMI can be present in both bulk materials [4] and at interfaces of ferromagnet/normal metal (NMs) [5]. Recently the interfacial DMI in rare-earth iron garnets (REIGs) with perpendicular magnetic anisotropy (PMA) has been the focus of many studies [6]. REIGs are a relevant family of materials for spintronic applications thanks to their highly tunable magnetic properties through composition, strain, stoichiometry, and temperature [7].

Among them, Tb3Fe5O12 (TbIG) is highly attractive due to its compensation temperature close to room temperature, which is relevant for ultrafast and efficient DW and skyrmion dynamics [8]. The origin of the interfacial DMI in the substrate/REIG/NM structures, however, remains elusive. While some reports claim the bottom interface substrate/REIG to be the main source of DMI [8], others show evidence that heavy ions at the REIG/NM interface are instead primarily responsible for this interaction [9].

This work aims to study the interfacial DMI in substrate/TbIG/NM heterostructures to tune its strength and understand the role of the NM. To do so, ultrathin films of TbIG were deposited by magnetron sputtering on a Gd3Ga5O12 substrate. On this substrate, TbIG grows epitaxially with PMA due to the compressive strain [10]. The effective field of the interfacial DMI (HDMI) is quantified through current and field-induced DW de-pinning, optically detected with a wide-field polar MOKE setup. First, we studied the TbIG thickness dependence with Pt(4 nm) as the NM top layer and found the highest HDMI in TbIG(4 nm)/Pt(4 nm). Then, we investigated the effect of the top interface by inserting a thin Cu spacer layer, which reduced the HDMI by a factor of 3. Finally, replacing Pt with W increased the HDMI by an order of magnitude, proving the criticality of the top interface. This work is relevant for designing DW and skyrmion racetracks based on REIGs.

[1] Dzyaloshinsky, I. J. Phys. Chem. Solids 4(4) (1958) 241-255

[2] Fert, A., et al. Nat. nanotech. 8(3) (2013) 152-156

[3] Tetienne, J. P., et al. Nat. comm. 6(1) (2015) 6733

[4] Beille, J., et al. Solid State Commun. 47(5) (1983) 399-402

[5] Bode, M., et al. Nature 447(7141) (2007) 190-193

[6] Avci, C. O., et al. Nat. nanotech. 14(6) (2019) 561-566

[7] Dionne G. F. Magnetic Oxides. Springer New York, NY (2009)

[8] Stanciu, C. D., et al. Phys. Rev. B 73(22) (2006)

[9] Xia, S., et al. Appl. Phys. Lett. 116(5) (2020)

[10] Damerio, S., et al. J. Appl. Phys. 133(7) (2023)

19_2663 Study of optical and electrical properties of non-fullerenes Langmuir-Schaeffer and drop-casting films

Clarissa A OLIVARI

Abstract

Due to the search for sustainable energy generation alternatives and their technologies, in recent years there has been great progress in the advancement of new photovoltaic devices and in the discovery of new materials that can provide, through studies, an increase in efficiency and a reduction in cost of production. In this work, organic semiconductors were used to manufacture thin films through the Langmuir-Schaefer and Drop-Casting techniques to produce Y6:PM6 films. The introduction of non-fullerene acceptors in the manufacture of organic photovoltaic devices has boosted efficiency to over 18% due to improved light absorption and adjustable electron affinities, according to the literature. The reasons for its high efficiency are not fully understood, and are the focus of this work, but may be related to the wide absorption range, a long exciton scattering length, and exceptionally large morphology well-organized. The Langmuir techniques have shown to be very promising to produce thin films compared to the others, as they offer some advantages such as material thickness control, and mainly a molecular ordering of thin films. The control of the structure can lead to an improvement in the properties of the films, favoring the performance of optoelectronic devices, in which the organization of the material is directly connected to the molecular organization of the processed material. Through these studies, it was possible to obtain information related to the supramolecular structure of organic thin films, using UV-Visible absorption measurements and electrical characterization, to improve the understanding of the organization of layers based on Langmuir techniques and comparing the results with Drop-Casting films.

Keywords: non-fullerene; drop-casting; Langmuir films; electrical characterization.

20_2687 ALD-Free Monolithic Perovskite/Perovskite/Silicon Triple-Junction Solar Cells with Efficiencies over 22%

Yeo Jin CHOI

Abstract

Halide perovskites (PVSKs) are promising materials for use as absorber in solar cells due to their superior optoelectronic properties. A certified power conversion efficiency (PCE) of 26.1% has already been achieved in single-junction (1J) solar cells. Their easy bandgap tunability makes PVSKs suitable for tandem applications, surpassing the Shockley–Queisser limit with a certified PCE of 33.9% PCE in PVSK/Si double-junction (2J) solar cells. Despite the potential for higher efficiencies in PVSK/PVSK/Si triple-junction (3J) tandem solar cells, the current best efficiency of 3J tandems is still significantly lower than PVSK/Si 2J counterparts.The primary reasons for the low efficiency of 3J solar cells are the chemical degradation of the PVSK middle cell caused by solvents and the poor performance of the PVSK top cell.

In this study, we utilize a volatile solvent mixture of acetonitrile (ACN) and methylamine (MA) in ethanol for wide-bandgap PVSK top cell to prevent solvent penetration across the recombination layer between the two PVSK subcells. Through proton nuclear magnetic resonance (1 H NMR) spectroscopy analysis, we confirmed that the volatile solvent was removed immediately after spin-coating, with no residual solvent detected in PVSK wet films. Additionally, the performance of the wide-bandgap PVSK top cell with Eg of 1.96 eV could be significantly improved from 6.4% to 13.9% by including a urea additive, which enhances the crystallinity of the PVSK thin film. Finally, we could fabricate highly efficient PVSK/PVSK/Si triple-junction tandem solar cells without an ALD-deposited protection layer. The best 3J tandem cell exhibits a high PCE of 22.23%, with J_sc, V_oc, and FF values of 10.18 mA/cm², 2.78 V, and 78.6%, respectively.

21_2870 Slowed-down phase separation in thin films drying under microgravity and sounding rocket conditions for the application of organic photovoltaics.

Ishita JALAN

Abstract

Solution‐processed polymer organic photovoltaic devices have gained serious attention during the last decade and are one of the leading low-cost next generation photovoltaic technologies. The active layer of a polymer solar cell consists of a thin solid film of an electron donor blended with an electron acceptor. The morphology of the active layer is one of the important factors for the solar cell performance. To control the morphology, a fundamental understanding and control of the molecular interactions that contribute to the formation of structures within the molecular blend thin films is needed. The rapid evaporation of the solvent during the drying process induces a swiftly developing concentration gradient, ultimately leading to an ongoing phase separation in the film morphology.

In this work, we aim to use microgravity conditions to study the slowed down phase separation kinetics. Under microgravity conditions, it becomes feasible to observe the initial stages of morphology formation.

We have already seen differences when thin films were prepared under microgravity conditions under parabolic flights. Slower phase separation was seen for film prepared under microgravity as compared for films prepared under 1g. But also due to the short time span of 0 g and hyper-gravity phase it was challenging to ensure that the films completely dried under 0 g. In order to guarantee that the entire drying process occurs under microgravity conditions, it was necessary to perform the fabrication process during sounding rocket experiments. This will give us a longer microgravity stage, and therefore a deeper understanding of the morphology formation and phase separation at a molecular level.

22_2878 High-Current Middle-Bandgap Solar Cells for Si/Perovskite/Perovskite Triple-Junction Tandem Solar Cells.

Lim SUNG YEON

Abstract

The pursuit of efficient and sustainable energy sources has led to significant advancements in perovskite solar cell. To achieve high efficiency, research on perovskite multi-junction tandem solar cells have been vigorously conducted. However, fabricating efficient triple or higher junction photo-systems still remains challenging, and further research should be conducted to address the barriers in the fabrication of high-quality solar cells of these types.

In this study, we confirmed that the current of the triple-junction tandem cells is limited by the current of middle-bandgap solar cells and attempted to improve it. First, we controlled the ratio of cesium in the perovskite composition to enhance the current of the middle-bandgap cells. As a result, we successfully reduced the bandgap from 1.57eV to 1.54eV, leading to an average short-circuit current (J_sc) improvement from about 22 mA/cm² to about 23 mA/cm². Furthermore, we focused on improving the thickness of the carrier transfer layers (CTLs) to further enhance the current of the middle-bandgap cells. In the triple-junction solar cells, since the light absorption range of the CTLs overlaps with that of the front cells, the increase in the thickness of the CTLs improves the performance of the middle-bandgap cell without reducing the current. Additionally, we achieved an increased open-circuit voltage (V_oc) of the middle-bandgap cells by adding the self-assembled materials (SAMs) in the precursor. With these improved middle-bandgap cells having a J_sc of about 25 mA/cm², the J_sc of the triple-junction tandem cells increased from 9.74 mA/cm² to 10.33 mA/cm², resulting in a high power conversion efficiency (PCE) of 22.23%.

23_2887 All inorganic perovskite quantum dots and paper-based graphene photodetectors

Yining ZHAO

Abstract

Due to its excellent photoelectric properties, the perovskite quantum dots show great potential in various photoelectric applications. Paper is an ideal platform for creating flexible and eco-friendly electronic systems. When combined with 0D and 2D materials, it holds significant potential across various Internet-of-Things applications, covering from wearable electronics to intelligent packaging solutions. Here, we present photodetectors (PDs) on a paper substrate composed of graphene and CsPbBr3 perovskite quantum dots (PQDs). Hybrid structures combining PQDs with graphene offer a promising approach for quantum sensors. It benefits from robust quantum confinement in PQDs alongside improved light interaction, tuneable spectra, reduced phonon scattering, and enhancing photoconductive gain mechanism in graphene, all at room temperature. We use Sonoplot Microplotter for the lithographic printing of graphene, source and drain electrodes, and PQDs, to fabricate PDs on paper. These PDs have an external responsivity ∼82,000 AW-1 at 520 nm for an operating voltage of < 1 V. Thus, our combination of 0D and 2D materials via microplotting on paper substrate shows promise for wearable and flexible applications.

24_3012 In-situ solution-based doping of CdS for CdS/CdTe solar cell applications

Jose-Manuel FLORES-MARQUEZ

Abstract

CdS is an n-type semiconductor typically used in CdS/CdTe solar cells as window material due to high optical transparency, wide band gap (2.28-2.50 eV), manipulable thickness less than 100 nm, low temperature deposition process (< 75 ºC) and compatibility with several kind of substrates. Usually, CdS is deposited by chemical bath deposition (CBD), which is a simple and inexpensive solution-based process. Moreover, the ability of changing the doping element concentration during CdS in-situ CBD process could lead to a potential optimization in device performance and will allow the development of other novel structures, including some ternary compounds. In this sense, increasing CdS band gap energy by introduction of impurities without a major lattice deformation and therefore increasing the number of photons that adsorbed by the absorber layer improves the blue response and could lead to an improvement in solar cells efficiency. This work propose study the influence of selected O, Ag and Al elements either doping CdS or adding other semiconductor thin films, to modify the CdS photogeneration behavior. CdS, CdS:Ag, CdS:Al and CdO thin films was grown by thermostatic chemical bath deposition technique (CBD) on FTO (SnO₂:F) substrate at 75±0.1°C / 8 minutes and 80±0.1°C / 40 minutes for doped CdS, and CdO thin film respectively. The doped CdS by in-situ CBD process uses CdCl₂ (0.1 M), SC(NH₂)₂ (0.3 M) as precursor solutions, NH₄Cl (0.2 M), NH₄OH (2 M) were used to promote the formation of complex compounds and AgNO₃ (1 ml) or AlCl₃ (1 ml) for incorporate the Ag or Al dopant element respectively. The CdO thin films were deposited by CDB with CdCl₂ (0.4 M) and NH₄OH (5.3 M) as precursor solutions and H₂O₂ 30% ACS reagent as reducing agent. Comparison of some physical properties was studied, including optical and structural properties.

Keywords: CdS, Nanostructured CdO, CdS:Ag, CdS:Al, CBD, CdTe Solar cells.

JMFM gratefully to projects SIP 20240539, 20240550, 20240551 and 20240552 from IPN, JMFM and CHV are grateful to CONAHCYT-México.

25_3014 New methodology to allows reduce the toxic waste generated in CdS thin films process by CBD technique

Roberto Carlos RUIZ ORTEGA

Abstract

Cadmium sulfide (CdS) n-type semiconductor is one of the most used as a window layer in CdTe, CIS, CIGS, and CZTS solar cells. Chemical Bath Deposition (CBD) technique had been reported to obatin CdS thin films. Chemical waste derivated of CBD process is a problem, due to the high prescursor solutions quantity used. The aim of this work is study and analyze how the amount of precursor solutions used for CdS growth modified the physical properties of CdS. The CdS thin films were deposited on soda–lime/SnO2:F substrates (FTO) in areas of 4 cm2 and 100 cm2, the thicknesses varied from 30nm to 120nm. Morphological measurements reveal different surface formations depending on the precursor solution quantity used for the growth, resistivity values of around 105 Ω*cm were measured, transmittance values of 45–94% in visible region and band gap energy values of around 2.1 eV–2.4 eV were obtained. CdS thin films with adequated physical properties and an efficient CBD process were obtained when the FTO substrates were located near the bottom of the reactor container with the FTO side down, reducing the amount of precursor solutions allowing to reduce the toxic waste generated and improving the environmental impact.

Key words: CdS, CBD, toxic waste, efficient process.

Aknowledgments: IPN Projects: SIP20240539 and SIP20240551

26_3018 Solid lubricant coatings based on chromium nitride and metal sulfide layers deposited by reactive magnetron sputtering

Rubenson MAREUS

Abstract

In the realms of academia and industrial research, CrN coatings have gained recognition for their exceptional mechanical properties, positioning them as the preferred material for applications demanding elevated hardness and robust adhesion. This study focuses on the deposition of CrN-type coatings infused with molybdenum (Mo) and tungsten disulfide (WS2) lubricants through reactive magnetron sputtering. These hard/auto-lubricant coatings, with a thickness equal to or exceeding 1 µm, were meticulously deposited at 0.5 Pa, room temperature, and 200 °C onto Si (100) and stainless steel 440 substrates. Specifically, they are designed for dry mechanical applications which requires good tribological properties without any additional lubricant during lifetime service.

The morphology and crystal structure of the coatings underwent thorough examination using scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Mechanical properties were assessed using a Nano Indenter in the continuous stiffness measurement mode (CSM) with a Berkovich indenter. The tribological characteristics of the coatings were scrutinized utilizing a HFRR (High-Frequency Reciprocating Rig) tribometer.

The resulting multilayer coatings exhibited a columnar microstructure, comprising alternating monolayers with a thickness of 100 nm. These monolayers demonstrated a cubic NaCl-type crystal structure, displaying a preferential orientation along the [111] direction. The infusion of solid lubricants into CrN proved instrumental in enhancing both the mechanical and tribological attributes of the coatings.

Finally, an in-depth comparative analysis will be conducted to evaluate the mechanical and tribological properties of these coatings against other materials such as Ti₂AlC MAX-phase carbides and Ti₂AlCN carbonitride.

Keywords: magnetron sputtering, solid lubricant coating, sulfide, chromium nitride, mechanical and tribological properties.

27_426 Towards large area growth of superconducting REBCO coated conductors by Transient Liquid Assisted Growth

Vittorio BERTINI

Abstract

Towards large area growth of superconducting REBCO coated conductors by Transient Liquid Assisted Growth (TLAG)

Superconductors are materials with unparalleled electrical and magnetic properties at low temperatures. Despite this, their real-world application to various engineering problems has been limited. This is not only because their operation requires cryogenic installations but also because of their difficult and complex fabrication, leading to very high production costs. Most state-of-the-art methods for producing desirable high-temperature superconductors (HTS) require high vacuum installations and achieve very low growth rates measured in few nm/s (<20 nm/s). This work represents a significant step towards the large-area growth of superconducting REBCO coated conductors, potentially addressing the limitations that have hindered widespread practical applications of high-temperature superconductors. The presented research contributes to the ongoing development of a disruptive technology with promising implications for the field.

The Transient Liquid Assisted Growth – Chemical Solution Deposition (TLAG-CSD) technology for the fabrication of REBa₂Cu₃O_7-x (RE=rare earth, REBCO) layers offers growth rates 2 orders of magnitude faster than most currently employed methods without the need of extensive vacuum installations. It is based on a non-equilibrium process where a transient liquid growth is combined with Chemical Solution Deposition (CSD) [1,2,3]. Beyond the process parameters and liquid composition, the selection of the RE (Y, Gd, Yb) allows further tuning of the growth temperature which is crucial to avoid reactivity of the liquid with the buffers. The TLAG-CSD-method is already finely tuned towards the deposition of superconducting film on small (5x5mm) single crystalline substrates as model systems with Jcs of up to 5 MA/cm² [1]. We investigate the optimal growth parameters of propionate based REBCO precursor solution on different commercially available substrates on smaller spin-coated samples which are characterized with various techniques (XRD, SEM, optical microscopy, Tc and Jc).
At the same time the optimal parameters for achieving high quality thin films of the precursor solution on larger substrates through slot-die coating are presented. The samples are then grown in the conditions found to work best at a smaller scale and success is measured through the Jc of the obtained samples of larger scale.

[1] Nature Communications 11, 344 (2020)
[2] ACS Applied Materials and Interfaces 14, 48582 (2022)
[3] Advanced Science 2022, 2203834, doi.org/10.1002/advs.202203834

28_690 Functionalized Interfacial Cover Design toward Pure Silicon Anode for High Power Density Lithium-Ion Capacitor

Min Ju OH

Abstract

The lithium-ion capacitor, comprising a capacitor-type positive electrode and a battery-type negative electrode, was proposed to achieve high power and energy density. Nevertheless, integrating different charge storage mechanisms into a single cell naturally leads to a kinetic mismatch between the two electrodes, which limits the potential for high power densities. To address this issue, there is an emerging need for high-capacity anode materials that can reduce the thickness of the negative electrode. Silicon (Si), known for its high specific capacity, is considered a promising anode material for enhancing both energy and power density. However, the rapid capacity fading and increase in internal resistance due to volume changes during cycling make it difficult to use a pure Si anode. In this study, functional layers, comprised of functionalized herringbone-type carbon nanofibers, are applied to both sides of the electrode to protect it from Si degradation. The polar functional groups on the cover weakly interact with both the native oxide layer of the Si surface and the carboxyl groups of the binder, ensuring stable contact through repeated cycles. Furthermore, the conductive functional layer promotes uniform fluxes of Li ions and electrons, aiding in the formation of a stable solid electrolyte interphase layer. This study investigates the effects of this strategy on pure Si electrodes through surface morphology analysis, assessment of chemical interactions, and electrochemical testing. The approach holds the potential to overcome the degradation issues of Si electrodes, significantly contributing to the improvement of the power and energy density of lithium-ion capacitors.

29_695 Advanced Ceramic Separators Enabling High-Performance Lithium Metal Batteries

Jun Sun EOM

Abstract

Lithium metal is regarded as an optimal anode material for both Li-S and Li-O₂ battery systems, primarily due to its impressive high theoretical capacity and low electrochemical potential. With a theoretical capacity reaching 3,860 mAh/g and an electrochemical potential of -3.04 V relative to the standard hydrogen electrode (SHE), lithium metal stands out as a crucial component in the development of advanced, high-performance batteries for future generations.

However, the utilization of lithium metal in batteries faces critical challenges during repeated charging and discharging cycles. The formation of dendrites on the anode surface, a result of lithium deposition, poses a significant risk. These dendritic structures can lead to short circuits, thereby raising serious safety concerns. Various strategies have been investigated to enhance the cycle life of lithium metal anodes. These include modifying the lithium metal surface and applying coatings to separators using different materials. Despite these efforts, many solutions compromise the battery's energy density and ionic conductivity due to the addition of ceramic elements and binders.

Focusing on the separator component, ceramic functional separators have been designed to bolster the durability of lithium metal anodes. Their primary benefit lies in promoting a uniform distribution of lithium ions, essential for consistent and efficient charge and discharge cycles. Traditional production methods for these separators, mainly slurry coating, result in micron-scale coatings that improve thermal stability but can reduce the battery's rate capability and energy density. This situation underscores the need for advanced separator designs that strike a balance between thermal stability and overall performance.

Our study introduces a novel approach by employing nanoscale ceramic-coated separators, significantly enhancing the endurance of lithium metal anodes. Breaking away from conventional techniques like slurry coating, we employ electron beam coating technology. This method achieves a nanoscale, uniform distribution of metal oxide particles on conventional PE separators. It addresses the issue of uneven lithium ion flow and effectively minimizes dendritic lithium metal growth. Notable improvements were observed in the LiFePO₄-Li cell tests, demonstrating increased Coulombic efficiency with ceramic-coated separators compared to standard PE separators.

30_766 Sonochemistry for the low-temperature solution processing of metal oxide thin films with applications in flexible electronics

Maria ECHANIZ-CINTORA

Abstract

Nowadays, the rapidly evolving electronic industry is demanding high performance electronic devices, which must be cheap, lightweight and flexible devices with multiple functionalities, with the aim of fulfilling the expectations generated by the Internet of Things (IoT). Due to their endless properties, metal oxides are considered the best candidates to work as the building blocks of these electronic devices. In general, metal oxides require high processing temperatures to attain the structure responsible for their functional properties. However, these temperatures are not compatible with the integration of the metal oxides with the substrates used in flexible electronics, which have low degradation temperatures. Hence, the preparation of flexible electronic devices demands low processing temperatures to successfully achieve the integration of functional oxides in these devices.

Chemical Solution Deposition (CSD) is a method based on the deposition of precursor solutions on substrates for the fabrication of thin films. It is shown as one of the most viable methods for the integration of films with flexible substrates due to important advantages like low-cost, large-area deposition or high chemical and stoichiometric control. On the other hand, sonochemistry has been traditionally used for the preparation of crystalline nanoparticles. It uses acoustic cavitation (ultrasound radiation 20 kHz - 10 MHz) to initiate ultrasound activated chemical reactions. For these reactions to take place, the creation, growth and collapse of bubbles formed by ultrasound in a liquid is needed. When these bubbles collapse, high temperatures are produced at local scale. These conditions have been traditionally used for the crystallization of nanoparticles in supersaturated solutions.

This work utilizes for the first time high-frequency ultrasound for the seeding of metal oxide precursor solutions, which are later used for the CSD preparation of thin films. The nanoparticles generated by acoustic cavitation in the solution can act as nucleation sites in the deposited film for the initial formation and growth of the functional oxide. As a result, the activation energy for crystallization can be reduced by the heterogeneous nucleation promoted by these nanoparticles. This translates into a decrease in the thermal budget used for the processing of the metal oxide film. Through this novel approach, we intend to overcome the thermal limitations associated with the integration of functional metal oxides in flexible electronics.

This work is part of the Spanish Projects PID2022-136790OB-I00 (funded by MCIN/AEI/10.13039/501100011033) and CNS2022-135743. M.E-C. acknowledges financial support from the FPU grant of the Spanish Ministry of Science, Innovation and Universities (FPU22/01677).

31_773 Quantitative in-depth characterization of thin film stacks with sub-monolayer sensitivity using reference-free X-ray spectrometry

Philipp HÖNICKE

Abstract

Reference-free X-ray spectrometry techniques [1] allow for an absolute quantitative and in-deth characterization on nanolayers and nanolayer stacks. The underlaying exerimental techniques
rely on radiometrically calibrated instrumentation, which is a unique feature of the Physikalisch-Technische Bundesanstalt. Various instruments and different beamlines are available at PTB’s laboratory at
BESSY II in the spectral ranges of soft and hard X-rays (78 eV to 60 keV).
With reference-free X-ray spectrometry, a nondestructive and quantitative characterization of nanolayers in a broad regime with respect to their thickness is enabled. Sub-monolayers
of material as well as complex stacks of different nanoscale materials can be characterized with respect to their mass depositions, their depth dependent composition [2] or their chemical
species composition.
For example, in the case of atomic-layer deposition, the deposited amount of material per cycle and the lateral homogeneity of the initial growth from the first deposition cycle on can be
quantitatively characterized [3] also on complex sumbstrates.

[1] B. Beckhoff, Nanomaterials (2022) 12, 2255
[2] P. Hönicke et al., J. Vac. Sci. Technol., A (2019) 37, 041502
[3] D. Hiller et al., Sol. Energy Mater. Sol. Cells (2020) 215, 110654

32_830 Integration and testing of synthesized materials based on sulfur in Li sulfur batteries

Luisa Roxana MANDOC

Abstract

Current trends in technology clearly show the need for durable, high performance and safer batteries throughout their entire life cycle. This is mainly due to developments in the digital economy, renewable energy and low carbon mobility. The transition to a climate neutral Europe requires fundamental changes in the way we generate and use energy. In other words, rechargeable batteries are a key technology for the transition to a climate neutral society. As all economic sectors advance rapidly, they ultimately need new battery technologies to meet the demand for ever higher energy densities. Also, the environmental footprint of the entire battery value chain is currently generating heated debates, for example: the replacement of CRM (critical raw material, such as Lithium, Cobalt and most likely Nickel, which will become critical in the near future), the socio-economically problematic use of Cobalt, recycling and long-term stability. A shift to new materials is therefore necessary.

In this study, the synthesized materials based on sulfur, were integrated as cathode electrodes in CR 2032 coin cells. These cells were characterized electrochemically by cyclic voltammetry and EIS – electrochemical impedance spectroscopy, and subsequently were galvanostatically tested by plotting charge and discharge curves.

Key words: energy storage, lithium–sulfur batteries, carbon–sulphur electrode, electrochemical performance

Acknowledgments

The work was supported by the grant of the Romanian Ministry of Research, Innovation, and Digitalization, project PN 23 15 02 01, 119111 - Implementing storage technologies based on post-Li batteries: new insights into the transition to a new generation of sodium and sulfur batteries – BatNaS and by the grant of the Romanian National Authority for Scientific Research and Innovation, CCCDI-UEFISCDI, PN3-P3-428/2021, project number ERANET-M-SMICE-Li.

33_831 Imaging Spectroscopic Ellipsometry (ISE): Optical Properties and Thin Film Metrology of ALD printed Microstructures

Peter H. THIESEN

Abstract

ATLANT 3D Nanosystems develops a disruptive 3D printing technology for micro and nano device rapid prototyping. The initial 3D printer prototype will be able to process only oxide materials at first, such as SiO₂, TiO₂, Al₂O₃, ZnO with resolution of 50-200 um. Later on, we will add processing of other materials, such as metals, sulfides, nitrides etc., also with a better selection of resolution down to 1 um. Thin film metrology of printed structures requires a fast measurement technique that is sensitive to thinnest films and offers a high lateral resolution also suited for the next development steps. Imaging Ellipsometry is an all-optical, non-contact metrology technique. It combines microscopic imaging with the measurement principles of spectroscopic ellipsometry and reaches a spatial resolution of about 1 µm. Ellipsometry is based on the sample’s interaction with polarized light and enables the characterization of ultra-thin films.

The thickness of ALD-structures, printed at variable process parameters or with different materials was characterized by imaging ellipsometry. The standard characterization was done with a fixed angle of incidence system, equipped with a high power LED-HUB (SIMoN, Park Systems GmbH) at an AOI of 60° and selected wavelength. Additionally, microscopic maps at different AOIs and wavelength of selected samples were recorded (EP4, Park Systems GmbH). The optical modelling for these different methods will be one focus of the presentation.

35_952 Chemical bath deposition of Ternary Cu2SnS3 thin films for solar cells application

Alexander BENKOVSKI

Abstract

Multicomponent chalcogenides are promising materials in photovoltaics with their chemical stability, suitable electro-physical properties and variety of synthesis approaches. In this work we present a simple and easy way for depositing of Cu₂SnS₃ (CTS) thin films by chemical bath deposition in aqueous solution on glass substrates. The layers are formed by precipitation of coordinated by EDTA metal ions with sulfide ions at temperatures raised at about 90^oC. The composition of the layers depends on the metals’ ion ratio in the solution and for better crystallization the samples are subject of annealing up to 180^oC. The stoichiometric Cu₂SnS₃ layers exhibit optical band gap near 1.1 eV for direct transitions with small deviations as temperature of annealing increases up to 250^oC. XPS analysis shows the constituents ions in their state of Cu⁺, Sn⁴⁺, and S^2-, respectively. The XRD data reveals formation of well crystalized cubic phase of CTS. Work function measurements of CTS thin films shows levels near 4.1 eV for stoichiometric compositions. The I-V (current–voltage) analysis of thin films stack structures with Soda lime glass/ITO/CTS/Me with different metal (Me) contacts shows p-type conductivity of the CTS layer, and ohmic or non-linear behavior, depending on the nature of the metal.

36_958 VO2-Based Multilayered Structure for the Temperature-Adaptive Control of Both Solar and Infrared Radiation

Myeongkyu LEE

Abstract

Energy-saving smart windows have drawn growing interest in recent years. For this purpose, solar radiation (0.4-2.5 micrometer) and thermal infrared in the atmospheric window range of 8-13 micrometer should both be controlled by the window. VO2 is an attractive thermochromic material that exhibits a volatile transition between insulating and metallic phases. Thus, VO2-based window coating structures have been extensively investigated. However, simultaneously achieving large changes in solar transmission and thermal emission remains a challenge. In this study, we present a multilayered coating structure that enables the temperature-adaptive control of both solar and infrared radiation. The structure consists of a VO2 top layer, a dielectric spacer layer, and oxide/metal/oxide bottom layers. The VO2 layer modulates solar transmission and thermal emissivity according to its temperature-dependent phase, whereas the bottom layers partially transmit solar radiation but completely reflect infrared. Therefore, the structure forms a Fabry-Perot cavity at infrared wavelengths, and the dielectric spacer plays a role to exhibit an emission peak in the 8-13 micrometer range. The functionality of the presented structure is experimentally verified.

AP02_Poster Session

Date: 29-05-2024

Time: 13:45-15:30

Room: ETOILE - FIRST FLOOR

Click here to have the Symposium details as a pdf

01_137 Growth Facet Control of Metallic Anodes for High-Energy Metal Batteries

Yanpeng GUO

Abstract

In the past decade, metal batteries have attracted enormous attention for its unprecedented energy densities in comparison to their metal ion counterparts. Amid these metal batteries, the non-aqueous lithium metal batteries and the aqueous zinc metal batteries are the two hottest systems. However, the use of metallic anodes introduces the knotty plating/stripping behaviours. The repeated deposition/dissolution of metal at the anode side could easily trigger the severe dendrite growth, dead Li formation and incessant electrolyte-related adverse reactions that leads to poor reversibility, cyclability and rate capability. Fundamentally, these drawbacks are closely associated with the crystallographic facet orientations of the metal deposits. In this regard, it is highly pivotal to control the growth facets of the metal deposits to promote the electrochemical performances of metal batteries. Here we propose two strategies to effectively manipulate the growth facets of metal deposits including the adoption of substrate with 1) highly responsive ferroelectricity and 2) ultraweak substrate-metal interactions.

Typical ferroelectric materials were selected and coupled into the conductive substrate. Upon external applied voltage, the ferroelectric material could spontaneously polarize to generate two charged ends to separately absorb metal ions and cations within the electrolyte. Besides, the instantly-generated opposite polarized electric field within the substrate could balance the applied electric field at the interface. When adopted for Li plating, the deposition of wild Li dendrites was reshaped to regular Li crystals that manifest in hexagonal or rectangular shapes to maximally expose low-energy (110) facets to achieve better cycling performances.

The substrate-metal interaction also largely determines the facet orientations of metal deposits which generally includes reaction-based interaction, strong chemical bonding, and weak physical bonding. With strong interactions, the deposition of metals could be kinetically affected and thus the metals may be unable to show their intrinsic thermodynamically stable facets. Take Zn metal for example, it displays a typical hexagonal closely packed structure and 002 facets are the most stable and benefit the horizontal Zn growth. However, the Zn deposits in most reported literatures show a 100- or 10-oriented growth which poses high risks to dendrite growth and side reactions. In this regard, a ultraweak substrate-metal interaction is introduced and corresponding Zn deposits show extremely high peak intensity ratios for 002/100 and 002/101 that is equivalent to an unprecedented 002 facet proportion over 99%. These 002-oriented Zn anodes thus exhibit extraordinary anti-corrosion capability and low-rate cycling stability.

02_1423 Chitosan-based resist formulations for DUV lithography for sub-micron resolution at pilot scale

Flávia MESQUITA CABRINI

Abstract

Within nanofabrication, photolithography represents a fundamental process for the patterning of thin films of resists. It involves the use of high volumes of polymer-based resists, solvents and alkali-based solutions, among which chemicals known to be harmful to human health and the environment. Knowing that the semiconductor ecosystem is committed to reach carbon neutrality in 2050 to reduce greenhouse gases, preserve energy and water, alternative and suistainable options to current oil-based resists systems are required.

Photolithography includes 3 main steps: 1) the deposition of the resist onto the substrate, typically the spin coating of polymer formulations containing a photoactive agent; 2) the UV or DUV light exposure within the use of a mask for the patterning of the resist upon the generation of latent images on the exposed-non exposed areas; and 3) the development of the resist, aimed for revealing the latent image once generated by removing either parts of the resist that were exposed (positive type of photoresists) or not-exposed (negative type of photoresists).

While several groups have been working on greener approaches such as the use of bio-sourced resists (polysaccharides, egg and silk proteins, etc.) at lab scale, our group has been the first one to demonstrate the feasibility of using chitosan-based resists fully developable in aqueous solutions to obtain sub-micrometer pattern resolution at pilot scale using 193 nm lithography on preliminary results.^1-4 Although encouraging, the challenges related to the industrial use of such approach still remains. Further efforts are required to improve photosensitivity and resolution (step 2) as well as a good film homogeneity within large substrates employed at 200 or 300 mm industrial scale on silicon wafers (step 1) and suitable development conditions (step 3). In this sense, we have been working on new formulations for obtaining films that are more homogeneous, more sensitive to the UV light and presenting a better resolution of patterns. Formulations containing photoacid generators (PAG) and photoinitiators have been studied, and promising approaches with increased sensitivity (improved by a factor of 2) were obtained, allowing the fabrication of patterns down to 400 nm size.

¹ P. Durin et al, J. Vac. Sci. Technol. 2023, B 41, 062204.

² I. Servin et al., Micro and Nano Engineering 2023, 19, 100202.

³ I. Servin et al., Proc. SPIE 12498, Advances in Patterning Materials and Processes XL 2023, 1249818.

⁴O. Sysova et al., ACS Appl. Polym. Mater. 2022, 4, 6, 4508.

03_1501 Importance of MgO Interlayer in CsPbI2Br Perovskite Solar Cells

Zhuldyz YELZHANOVA

Abstract

Recently, there has been a notable increase in interest in perovskite solar cells (PSCs) due to their ever-improving power conversion efficiency (PCE) and cost-effective manufacturing processes. Over the past decades, the PCE of single-junction PSCs has increased from 3.8% to a recent record value of 26.1%, indicating a huge potential for this type of photovoltaics in the community.

Currently, one of the main challenges of PSCs is their device instability, which remains a barrier to future commercialization. All-inorganic perovskites with excellent stability under high temperatures have been intensively investigated as an alternative absorber layer in PSCs. Among all-inorganic perovskites, CsPbI₂Br perovskite has an optimal band gap of 1.92 eV with high phase stability for solar applications. The device performance is strongly affected by the defects in the bulk of the materials and at the interface. Meanwhile, the intrinsic instability of PSCs mainly occurs at the interface between the constituent layers. In this study, we propose a method to improve the device stability by effective interfacial engineering using magnesium oxide (MgO) as an interlayer between the zinc oxide (ZnO) electron transport layer and the CsPbI₂Br absorber. It is found that the incorporation of MgO as an interlayer can induce enlargement of the perovskite grain size compared to the perovskite grown directly on ZnO. The surface properties of ZnO and ZnO/MgO are investigated. The optical and electrical characteristics of these layers are also systematically studied. The stability tests are performed on both materials and devices. The prepared samples stored in ambient air and glove box have been monitored for a long duration. The perovskite samples grown on MgO interlayer exhibit better material stability compared to the control sample. Moreover, the PSCs with MgO interlayer maintained 88% of the initial PCE while the control sample exhibited 69% of remaining PCE after 35 days. The results of our work show a significant positive effect of MgO interlayer on PSC performance, providing useful information to the community for interfacial engineering of Cs-based PSCs.

04_1521 Morphological Control of Cs2PbX4 Nanostructures for Interfacial Engineering of CsPbI2Br Perovskite Solar Cells

Gaukhar NIGMETOVA

Abstract

The photovoltaic (PV) technology has been driven by rapid advancements in material science, significant improvements in device efficiency, and the development of cost-effective manufacturing processes. The global efforts towards sustainable and renewable energy sources have pushed forward the research and investment in PV technology. The emergence of perovskite solar cells (PSCs) has made a breakthrough in the community by exhibiting high power conversion efficiencies (PCEs) of 26.1%. However, the stability of PSCs is still a bottleneck before their commercialization. To address the stability issues, this study explores a controllable technique for obtaining highly stable 3D/2D perovskite thin films for solar cell applications.

The morphology control of 2D all-inorganic perovskite on 3D Cs-based perovskite thin films is established in this work. We demonstrate a controllable crystallization route of Cs₂PbX₄ (X = mixed halide system) 2D perovskite on the surface of CsPbI₂Br. Our experiments reveal that Cs₂PbX₄ perovskite can effectively passivate surface defects, enhancing both photovoltaic performance and device stability of CsPbI₂Br-based solar cells. With the optimized interfacial engineering technique developed in this work, we achieved an improvement in device PCE from 10.53% to 13.8%. After the protonated irradiation, 87.5% of the initial PCE can be retained compared to the nearly dead control device. Our study demonstrates that incorporation of optimized 2D Cs₂PbX₄ perovskite on CsPbI₂Br can significantly enhance the performance of solar cells. The results obtained from this work provide useful information for future in fabricating large-scale PVs with incorporation of 2D perovskite nanostructure as an interfacial engineering approach.

05_1523 Boron doped Zinc Oxide thin film as ETL alternative candidate in perovskite single-junction solar cell

Fiorella TRINGALI

Abstract

The development of innovative and better-performing materials that fulfill device’s requirements and overcome limiting factors is crucial to improve the performance of future solar cells. Therefore, our research aims to contribute on reducing the recombination rate of photo-generated carriers by investigating C₆₀/BZO (Fullerene/Boron doped Zinc Oxide) as innovative Electron Transport Layer (ETL) combination on the back side of single junction p-i-n perovskite solar cells.

Optimal ETL material should combine a low minority carrier recombination rate with low resistivity and high optical reflectance, which is essential to ensure efficient light trapping and absorption. To pursue these requirements, an in-depth examination of the properties and characterization of low-concentration Boron doped Zinc Oxide thin films, deposited via Magnetron Sputtering, was carried out. Sputtering deposition is a widely employed technique in microelectronics and photovoltaics industries, due to its versatility and higher throughput as compared to thermal evaporation. Moreover, this technique allows for depositions under highly controlled conditions, enabling the reproducible growth of films with high purity, good quality and strong adhesion to substrates.

BZO (2 at.% of Boron) was deposited by RF, DC and Pulsed DC magnetron sputtering, using a 4-inches BZO target (99.99% purity), under different sputtering powers (150W, 200W) and a range of Argon working pressures (from 5.0·10^-3 mbar to 9.0·10^-3 mbar). Additionally, more sets of samples were deposited in either Ar-O₂ or Ar-H₂ atmospheres. XRD analyses revealed a polycrystalline structure in all the deposited samples. Further results showed that samples deposited at lower sputtering power (i.e. 150W) and high working pressure (9.0·10^-3 mbar) exhibit low absorbance and high optical reflectance. Conversely, the high-power (i.e. 200W) and low-pressure (5.0·10^-3 mbar) deposited samples demonstrated more prominent electrical properties but poorer optical performances. These results could be attributed to differences in the growth kinetics within the sputtering chamber, i.e. different mean free path of sputtered atoms in relation with the working pressure, yielding films with different structure.

Given the promising properties of BZO deposited by sputtering, a new single-junction perovskite solar cell was designed, incorporating C₆₀ combined with a ~30 nm BZO thin film as ETL, replacing the standard C₆₀/BCP (Bathocuproine) employed in the analogue reference cell. Despite BZO not being a conventional material for this application, several tests returned optimal results, indicating a Power Conversion Efficiency (PCE) of ~10% and V_oc of ~1000 mV – results that are comparable with the performance of the established reference cell. These preliminary findings are both innovative and encouraging, suggesting that C₆₀/BZO could be a viable alternative as ETL in single-junction perovskite solar cells.

06_1594 Cu Nanoparticle by Laser Ablation in Liquid in film arrangement film for green hydrogen production

Cristiano LO PÒ

Abstract

Hydrogen (HER) and Oxygen (OER) evolution reactions play a fundamental role in the field of green sustainability, because they are key reactions for water electrolysis. The high-performance materials are platinum for HER, while iridium and ruthenium oxide for OER. These materials are precious and rare, thus in economic terms, earth abundant and non-pollutant electrocatalyst should be employed. Transition metals represents a good alternative as catalyst, both in the metallic and oxide phases. In this work copper nanoparticles (NPs) are produced using Pulsed Laser Ablation in Liquid (PLAL) because this technique is economic, does not produce waste and is able to produce a large amount of NPs in a short time. Using water as liquid medium is reported to produce oxide nanostructures, while organic solvent typically led to metallic NPs.

Copper NPs are synthetized using a Nd:YAG ns-pulsed laser in different solvents (λ =1064 nm, 12ns, 5W, 10Hz, solvent 8mL, ablation time 8min). The modifications (shape, size, etc.) and properties (metal, oxide, etc.) of the Cu nanostructures were studied as a function of the used solvent: methanol, ethanol and acetone.

Morphological and structural characterizations have been performed by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-Ray (STEM-EDX) spectrometry analysis. The crystalline phase of NPs has been determined by X-Ray Diffraction (XRD) analysis and Raman Spectroscopy, while the surface of the NPs was investigated using X-Ray Photoelectron Spectroscopy (XPS).

Cu NPs show a metallic nature, are surrounded by carbon, does not present oxide shell and follow a lognormal size distribution with most representative radii of 2.1nm, 3.3nm and 2.7nm respectively in methanol, ethanol and acetone.

Electrodes have been realized by drop casting 100µl of the three colloidal suspensions on 1cm² of nickel foam (NF). For each type of electrode, the catalyst loading was estimated about 1µg/cm². Electrochemical measurements have been performed in electrolyte consisting of 1 M KOH. A three-electrode setup has been used with platinum wire as the cathode and a saturated calomel electrode (SCE) as the reference electrode. The HER and OER activities were investigated using Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS).

The catalytic activity of the NPs is relevant already at 10mA/cm² and he improvement with respect to the bare substrate become more evident at higher current densities. The performance in terms of overpotential (η) at the standard current density of 10mA/cm² reaches the value of η=0.2V in HER and η=0.3V in OER. The ultra-low amount of the catalyst material makes these electrodes competitive in terms of mass activity (up to 14A/mg at 10mA/cm²) compared to the state of the art.

This work was funded by European Union (Next Generation EU), through the MUR-PNRR project SAMOTHRACE (Grant No.ECS00000022).

07_1661 Application of vanadate glasses containing different metal oxides to rechargeable batteries

Nobuto OKA

Abstract

Cathode materials with high charge-discharge capacity are expected for Li-ion battery and metal-air battery to be applied to hybrid and electric cars. We have developed new cathode materials using vanadate glasses containing different metal oxides for these types of rechargeable batteries. Conductivity of barium iron vanadate glass, 20BaO·10Fe₂O₃·70V₂O₅ and its analogs, could be “tunable” over a wide range (10-7-10-1 S∙cm-1) by isothermal annealing.

First, we present the application of the conductive vanadate glass to a cathode active material of Li-ion battery. Crystalline LiCoO2 and LiFePO4 have so far been utilized as the cathode active material. The latter is known to have a discharge capacity of 160 mAh/g. It is expected that more Li+ ions could be stored in glassy materials since they have larger specific volume. In this study, cathode active materials of vanadate glass were prepared by the melt-quench method, of which composition was expressed by 15Li₂O‧10Fe₂O₃‧5P₂O₅‧xCr₂O₃‧(70-x)V₂O₅ and 15Li₂O‧(10-x)Fe₂O₃‧5P₂O₅‧xCr₂O₃‧70V₂O₅ (x=0, 3 and 5). Annealing of the glass samples was conducted at 500 ^oC for 90 min. Charge-discharge capacity was investigated at room temperature using a half-cell of coin type. X-ray diffraction of vanadate glasses measured before annealing revealed an amorphous structure. After annealing, several crystalline peaks were observed, indicating a formation of glass-ceramics. Very high discharge capacity of 250-300 mAh/g was achieved when discharged from 3.5 to 1.5 V.

Second, we present the results of air-electrode (cathode) catalysts containing vanadate glasses for metal-air rechargeable battery. Metal-air battery has a very high energy density because it could use atmospheric oxygen as the electrode active material. This rechargeable battery needs bifunctional catalytic materials, which involve effective oxygen reduction/evolution at the air electrode in the discharge/charge process. New catalytic materials have been developed using vanadate glasses containing MnO2 and NiO, 20BaO·5MnO₂·5NiO·70V₂O₅ glass. For the preparation of the air electrode, pulverized vanadate glass was mixed with poly (tetrafluoroethylene), which was hot-pressed on the gas diffusion layer over a Ni metal mesh. 8M KOH aqueous solution and a Pt mesh were placed inside the Teflon cell as the electrolyte and the counter electrode, respectively. Temperature of the Teflon cell was kept constant at 60 °C. Discharge and charge polarization curves were recorded in a potentiostat. The prepared vanadate glass electrode showed an excellent bifunctional oxygen reduction/evolution activity, being more than that of the materials reported in the literature, such as polycrystalline LaNiO₃. This vanadate glass proved to be a highly potential candidate for the bifunctional catalytic material for the rechargeable metal-air battery.

Detailed information on the local structure will be presented at the conference, which was available from Mössbauer measurements at RT.

08_1682 Calcium Niobium Oxide Nanosheet for Application in Proton Exchange Membrane Fuel Cell

Mohammad Atiqur RAHMAN

Abstract

Developing an efficient proton conducting materials showing high power density and long term durability is highly challenging. Perovskite metal oxides have found significant interests for applications in electrochemical energy conversion devices because of their extraordinary physical and chemical properties. However, ion conduction in perovskite-related materials is rare, and the mechanism of proton conduction is still unclear.¹ Herein we have fabricated Dion–Jacobson (D–J)-type layered perovskites, potassium calcium niobium oxide (KCa₂Nb₃O₁₀) using solid state reaction followed by protonation and exfoliation to get the calcium niobium oxide (CNO) nanosheet. Thin film membrane of CNO was fabricated using vacuum filtration. The fabricated membrane showed flexibility with good mechanical strength. Proton conductivity and proton exchange membrane fuel cell performance was evaluated while varying both humidity and temperature. CNO membrane represents a proton conductivity of 8.14 × 10^-5S cm^-1 at 90 ℃ and 100 % RH condition with activation energy, E_a, of 0.11 eV. Additionally, measurement of proton exchange membrane fuel cell performance using 22 µm CNO membrane give rise to an optimum power density of 2.29 mW cm^-2 with a current density of 4.67 mA cm^-2 at 90 ℃ and 100 % RH condition. Additionally, observation of the open circuit voltage (~0.97 V) indicates that CNO membrane has low fuel crossover. These results imply that CNO membrane has potential for application as electrolyte in proton exchange membrane fuel cell.

Reference:

[1]. Yuichi Sakuda, Taito Murakami, Maxim Avdeev, Kotaro Fujii, Yuta Yasui, James R. Hester, Masato Hagihala, Yoichi Ikeda, Yusuke Nambu, and Masatomo Yashima, Dimer-Mediated Cooperative Mechanism of Ultrafast-Ion Conduction in Hexagonal Perovskite-Related Oxides, Chem. Mater. 2023, 35, 22, 9774–9788.

09_1709 Vanadium carbide Mxene-reduced graphene oxide composite for high-performing supercapacitor with redox modified electrolyte

Rahul RAVINDRAN

Abstract

It is clear that we are entering an era where energy storage technologies will become more prominent and large scale storge technologies would become a necessity. MXene is one of the newly discovered materials that have shown tremendous potential as an electrode material for high-performance supercapacitors. In this work we report the performance of vanadium carbide MXene-reduced graphene oxide composite with redox modified electrolyte. Herein, the vanadium carbide-reduced graphene oxide composite was successfully synthesised without using HF acid and is used as the electrode material in a supercapacitor. Density functional theory analysis proved the metallic nature of the vanadium carbide MXene. The performance was evaluated for 3M KOH with the addition of redox additive, potassium ferricyanide((K₃[Fe(CN)₆]), in various concentration, viz., 2mM, 4mM, 6 mM and 8 mM. The composite showed significant improvement in the electrochemical performance and the addition of the redox additive resulted in further performance enhancement of nearly about 3 times. The material also exhibits very high cycling stability of 99% even after 3000 cycles. The fabricated full cell device showed a very high energy density of over 80 Wh/Kg and power density over 900 W/Kg at 1 A/g current density, which proves its significance for large scale energy storage application.

References

1. Chandra et. al., Electrochem. Sci. Adv.2022;2:e2100030.

2. Gogotsi et. al., J. Phys. Chem. Lett. 2015, 6, 2305−2309

10_1714 Carbon Decorated Zif-67 Composite for Next Generation Energy Storage Device

Shyamal SHEGOKAR

Abstract

A novel strategy of incorporating conducting additive to enhance the performance of ZIF-67 based Al-ion supercapacitors is presented. The porous ZIF-67 and composites of ZIF-67 with different forms of carbon viz., rGO and CNS were synthesized by a simple co-precipitation method. Physiochemical characterizations like XRD, BET, FTIR, etc. were performed to confirm the successful synthesis of ZIF-67 and its composites. The electrochemical behaviour of the as-synthesized materials were studied using three electrode measurements. Amongst all the synthesized materials, composite of ZIF-67 with rGO performed best due to increased electrical conductivity and higher specific surface area. Further, electrolyte modification was carried out using 6 mM KFCN as redox additive and all the synthesized composites were tested again. Here, the specific capacitance of ZIF-67_rGO composite enhanced to 346 Fg-1 at 1 A g−1 current density which was nearly two times the value exhibited by pristine ZIF-67. It also delivered good cycling stability with excellent coulombic efficiency of 89% and 95% after 1000 cycles, at 5 A g-1 current density, respectively.

11_1754 Doped phosphite compound for enhanced electrochemical characteristics as active electrode material for Li-ion battery

Hassna BELHAJ

Abstract

Lithium-ion batteries have become the go-to technology for many energy storage applications. Research and development continue to explore new materials to improve the features and make these batteries even more powerful and efficient. Phosphorous polyanionic compounds such as LiTi₂(PO₄)₃[1], LiFePO₄[2], Li₃V₂(PO₄)₃[3] have been widely investigated as potential electrode materials for LIBs. Their polyanion groups act as frameworks for accommodating Li⁺ ions, contributing to their high theoretical capacity. With the extensive research on phosphorous-based materials, phosphite structures (HPO₃)^2- are emerging as open frameworks in the battery field. Their use as negative electrodes for LIBs has been initiated by MANAPSE laboratory[4], [5]. Lithium titanium phosphite (LTP), in particular, has piqued electrochemical interest due to its long cycle life[6]. However, this anode material requires further optimization in terms of specific capacity. Some promising strategies to go beyond this setback include carbon coating, morphology control, or incorporation of foreign elements within the crystal lattice. The doping strategy was chosen as an effective way to improve the electrochemical properties of LTP phosphite, targeting the improvement of its capacity and ion diffusion during charge/discharge cycling. In this work, ion-doped materials were synthesized via a mild hydrothermal reaction. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). To study their electrochemical performances, galvanostatic charge-discharge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy measurements were carried out. The results showed that doping LTP anode can improve its electrochemical properties. Higher specific discharge capacities compared to the pristine material were obtained due to better electronic conductivity and faster ion transport.

[1] C. Delmas, A. Nadiri, and J. L. Soubeyroux, Solid State Ionics, vol. 28−30, pp. 419–423, 1988.

[2] A. K. Padhi, K. S. Nanjundaswamy, C. Masquelier, S. Okada, and J. B. Goodenough, J. Electrochem. Soc., vol. 144, pp. 1609–1613, 1997.

[3] J. Gaubicher, C. Wurm, G. Goward, C. Masquelier, and L. Nazar, Chem. Mater., vol. 12, pp. 3240–3242, 2000.

[4] S. Idrissi, Z. Edfouf, O. Benabdallah, A. Lallaoui, and F. Cherkaoui El Moursli, IEEE, vol. 3, pp. 1–5, 2018.

[5] A. Lallaoui, Z. Edfouf, O. Benabdallah, S. Idrissi, M. Abd-Lefdil, and F. Cherkaoui El Moursli, Int. J. Hydrogen Energy, vol. 45, pp. 11167–11175, 2020.

[6] F. C. El Moursli, A. Lallaoui, Z. Edfouf, I. Saadoune, and M. Abd-Lefdil, WO 2019/013609, 2019.

12_1975 Nonfunctionalized Mo2C: The game changer for better supercapacitors

Wonge Lisheshar IBRAHIM

Abstract

2-molybdenum carbide (Mo2C) is a member of the MXene family of two-dimensional materials, which has garnered substantial global research attention due to its fascinating electrochemical properties. The properties of MXenes include wide interlayer spacings, hydrophilicity, intrinsic conductivity, a high surface area, and surfaces that resemble transition metal oxides and can undergo rapid redox reactions. Mo2C has an outstanding theoretical capacitance of 3.2 mFcm-2, which is equivalent to 9816 Fg-1 in specific gravimetric capacitance. The most popular technique for obtaining MXenes is selective etching, which unavoidably leads to functional terminations since chemicals like hydrofluoric acid are required for the etching process. These functional terminations improve the intercalated pseudocapacitance and surface chemistry, but they also reduce the MXenes' conductivity and the overall supercapacitor performance. In this work, we synthesize nonfunctionalized MXenes by chemical vapor deposition. The performance of supercapacitors built using these pristine MXenes and 1M Na2SO4 electrolytes is then investigated. At a scan rate of 2 mVs-1, the electrodes with a thickness of 48.6 nm were found to have an incredible specific area capacitance of 39.5 mFcm-2, which is equal to 928.4 Fg-1. An initial specific gravimetric capacitance (SGC) of 442.6 Fg-1 at a current density of 0.5 Ag-1 was found by further examination utilizing galvanostatic charge-discharge analysis. This SGC gradually decreased to 13.4 Fg-1 at 10 Ag-1. Remarkably, the MXene supercapacitors retained 85% of their initial capacitance over 10,000 cycles of charge and discharge. These findings contribute to the progression of our understanding of MXene-based energy storage systems and pave the way for practical applications in high-efficiency supercapacitors. The research highlights the potential of non-surface-terminated MXenes synthesized through chemical vapor deposition as a viable alternative for the widely used etching procedure. It is expected that the study's findings will have a substantial impact on the advancement of high-performance supercapacitors and other energy storage devices.

14_2118 Enabling Mg metal powder anode via ex-situ deposition of a stable intermetallic interphase

Martina ROMIO

Abstract

Magnesium-ion batteries (MIBs) are a promising chemistry to potentially achieve higher energy densities at lower cost than lithium-ion batteries for stationary energy storage applications. This is possible thanks to the natural abundancy, low costs, environmental sustainability, and electrochemical properties of magnesium (Mg)^[1]. However, the major obstacle in the further development of MIBs is the incompatibility of Mg metal anodes with conventional electrolytes (e.g. Mg(TFSI)₂ in glymes). These solutions decompose at the surface of metallic Mg, forming a passivation layer that inhibits Mg²⁺ diffusion and electronic transport^[2].

A safe and sustainable wet-chemical approach is designed to develop an anode material by tailoring a protective intermetallic interphase onto the surface of Mg metal powder particles. This coating layer will prevent electrolyte decomposition and Mg passivation, while maintaining Mg²⁺ cation diffusion. The native oxide layer is removed from the Mg powder surface, using environmentally friendly acid solutions under inert atmosphere (e.g. citric acid). At the same time, Bi and Sn-based precursors will react with the fresh Mg surface, depositing a stable intermetallic Mg–X interphase. The as-protected Mg metal anode is expected to achieve long cell lifetimes (> 1000 hours) at low current densities (e.g. 1 mA cm^-2), while having a low overpotential (0.2 V). A high voltage, low-critical raw material MgMn₂O₄ cathode is employed to perform a comprehensive electrochemical characterization of the bare and coated Mg metal powder anode. In this way, the average voltage potential, cycle stability (> 100 cycles), charge and discharge capacities (> 80 mAh g^-1 upon discharge) are obtained.

Experimental methods and computational calculations (e.g. density functional theory) are synergistically used to characterise the properties of the intermetallic interphase. Microscopic (scanning electron microscopy, SEM), spectroscopic (X-ray photoelectron –XPS–, Raman and infrared spectroscopies), diffractometric (X-ray diffractometry), and electrochemical techniques (galvanostatic cycling, electrochemical impedance spectroscopy and cyclic voltammetry) will be applied to evaluate the composition, morphology, transport properties, and stability of the artificial protective layer after synthesis. First principles and machine learning potential calculations will be performed to gain mechanistic and molecular-level insights on the intermetallic interphases at ideal conditions, such as: phase stability and energetics, bandgap energies and electronic conductivities.

References:

1. J. Niu, Z. Zhang, D. Aurbach, "Alloy anode materials for rechargeable Mg ion batteries", Adv. Energy Mater., 10, 2000697, 2020.

2. D.-T. Nguyen, R. Horia, A. Y. S. Eng, S.-W. Song, Z. W. Seh, "Material design strategies to improve the performance of rechargeable magnesium-sulfur batteries" Mater. Horizons, 8, 830-853, 2021.

15_2128 2D Transition Metal Disulphide Alloys on Silicon Heterojunction Photodetectors

Aleksandr AVERCHENKO

Abstract

Silicon is the core material in modern optoelectronics, privileged from its scalable low-cost manufacturing technology. Nevertheless, the demand for highly efficient p-n heterojunction devices for sensing and energy harvesting applications motivate the quest for new technological veins to be integrated into this mature industry. Two-dimensional transition metal dichalcogenides (2D-TMD) such as MoS2, WS2, MoSe2 and WSe2 are promising candidates for building such 2D/3D heterojunctions with silicon, as they are layered semiconductors possessing considerably large and tuneable bandgaps ranging from (1-2 eV) with strong optical absorption. [1]

However, pristine 2D-TMD suffer from several shortcomings that can restrict their performance. Among them, deep-level defects (DLD) within the bandgaps of 2D-TMD represent a substantial issue for 2D-TMD heterostructure photodetectors, which causes degradation of photocarrier generation. DLD originate from chalcogen vacancies that are formed during growth. A practical approach to tackle this obstacle is alloying of transition metal dichalcogenides (e.g. Mo1-xWxS2), which can drastically convert the DLD into shallow traps, leading to enhancement in overall photodetection process and leveraging the carrier transport properties. Additionally, alloying broadens the operating spectral response for 2D/3D heterojunction devices.

Furthermore, a method for synthesis of 2D-TMD alloy films directly onto 3D silicon can be beneficial for the industrialisation of these novel optoelectronic heterojunctions. A suitable growth method that meets these criteria is the solution-based synthesis, which can produce large-scale, highly uniform 2D-TMD alloy films; with high yield and short processing time; and it can be combined seamlessly with silicon technology.

Here, we propose such a rapid manufacturing approach for heterojunction photodetectors consisting of 2D-Mo1-xWxS2 films, synthesised onto silicon substrates, by thermal decomposition in inert environment of single source thiosalts precursors films at atmospheric pressure. The resulting composition of 2D-Mo1-xWxS2 alloys is determined by adjusting the volume ratio of (NH4)2MoS4 and (NH4)2WS4 in the initial solution. Raman spectroscopy confirmed the successful growth of alloy films on silicon and revealed the composition of the resulting material.

The electrical response of the alloy/silicon devices was investigated, in dark conditions, to study the rectifying behaviour of the heterojunctions. A comparative study of the main photodetection figures of merits such as photocurrent, responsivity, spectral response, and rise/fall switching times, at different operating wavelengths will be presented for the heterostructures with different compositions.

[1]. Tian, W. et al. Low-dimensional nanomaterial/Si heterostructure-based photodetectors. InfoMat 1, 140–163 (2019).

16_2142 Systematic effect of chalcogen atom in the piezoelectric performance of PVDF/ MoS2xSe2(1-x) based piezoelectric nanogenerator

Vishal SINGH

Abstract

Systematic effect of chalcogen atom in the piezoelectric performance of PVDF/ MoS2xSe2(1-x) based piezoelectric nanogenerator

Vishal Singh, Bharti Singh*

CFMRL, Department of Applied Physics, Delhi Technological University, Delhi-110042, India

Abstract: This study explores a novel approach by systematically investigating the influence of chalcogen atoms in Transition Metal Dichalcogenides (TMDCs) MoS2Se2(1-x) (x = 1, 0.75, 0.5, 0.25, 0) in conjunction with polyvinylidene fluoride (PVDF) on the piezoelectric performance of fabricated piezoelectric nanogenerators. The research focuses on synthesizing flexible PVDF/TMDCs composite thin films to assess the impact of TMDCs as fillers in the PVDF matrix. XRD, Raman and XPS studies were used to confirm the successful synthesis of various TMDCs. FTIR spectroscopy analyses revealed an augmented piezoelectric behavior attributed to an increase in the polar β-phase content of PVDF following the incorporation of TMDCs. Remarkably, the PVDF/MoSSe based nanogenerator exhibited the highest piezoelectric properties among all fabricated devices. Piezoelectric coefficients, open circuit voltage and short circuit current were also calculated to check the enhancement in piezoelectric behavior of the fabricated thin films. Notably, this enhancement was achieved solely by introducing TMDCs without any additional treatment. The improved piezoelectric performance is credited to synergistic contributions from the intrinsic piezoelectric properties of the synthesized TMDCs and intensified β-phase in PVDF/TMDCs composites. The lack of reflection symmetry in the MoSSe structure resulted in additional out-of-plane electric polarizations, enhancing the already robust in-plane piezoelectric effects. The generated output demonstrated practical applications by powering various real time devices. In essence, this study introduces a pioneering method to boost piezoelectric performance by systematically introducing asymmetry to the out-of-plane crystal structure of 2D TMDCs within the PVDF matrix.

Keywords

Piezoelectricity, PVDF, Transition metal dichalcogenides, MoSSe, piezo nanogenerator, thin films.

18_2301 Structural control of semiconductor polymer D18 used in organic photovoltaics

Jesika ASATRYAN

Abstract

Organic photovoltaic devices typically include an electron donating semiconducting polymer and an electron accepting small molecule in their active layer. Among the champion polymers is the so-called D18, which stands out from their counterparts, as it develops high-degrees of structural order (in comparison with other OPV polymers, which are more disordered).

In order to gain more insights into the special structural characteristics of D18, we performed a deep and comprehensive investigation of structural aspects of D18 combining GIWAXS, fast scanning calorimetry, TEM and polarized microscopy. First, we resolve the actual solid-state microstructure and morphology of D18 when processed similarly as in devices and we understand its thermotropic phase behavior. But more interestingly, we discover that we are able to readily select the “type” of structural organization in D18, by playing with processing conditions,. Specifically, we are able to promote either a “liquid-crystalline-like” ordering, featuring exceptionally intense (100) reflection in XRD while almost null π-π reflection or “crystal-like” order, characterized by an intense π-π reflection. Moreover, our study reveals markedly different mechanical behavior for D18 showing distinct structural organization.

19_2368 Electro-dehydrogenation of amines into nitriles used as Liquid Organic Hydrogen Carriers

Francisco FABREGAT-SANTIAGO

Abstract

Storing and transporting hydrogen is one of bottlenecks for the transition to CO2-free energy sources. The small size and light weight of hydrogen makes it very difficult to confine and implies that all the natural gas transportation network needs to be fully refurnished before being able of transporting pure H2. To avoid this massive cost, alternative ways to transport large amounts of hydrogen are needed. One of the most promising ones is using liquid organic liquid organic hydrogen carriers (LOHCs), i.e. liquid molecules that can be hydrogenated (charging) and dehydrogenated (discharging). Hydrogenation and dehydrogenation processes typically need more or less harsh chemical conditions, that may include the need of strong chemicals, and high temperature and pressure. This study presents a gentle strategy to store hydrogen using the pair amine/nitrile as LOHC.1–5 we demonstrate that it is possible to dehydrogenate the amine into nitrile electrochemically in aqueous solution under environmental conditions of temperature and pressure at a high rate and with molecular hydrogen as the sole byproduct. These conditions offer a potential solution for the industrial use of amine/nitrile as LOHC. To end this work the strong and well differentiated interaction of the amine with the NiOOH electrode used to perform the electrochemical reaction, will be demonstrated by means of impedance spectroscopy.

References

(1) Cho, J.; Kim, B.; Venkateshalu, S.; Chung, D. Y.; Lee, K.; Choi, S. Il. Electrochemically Activatable Liquid Organic Hydrogen Carriers and Their Applications. J Am Chem Soc 2023, 145 (31), 16951–16965. https://doi.org/10.1021/jacs.2c13324.

(2) Preuster, P.; Papp, C.; Wasserscheid, P. Liquid Organic Hydrogen Carriers (LOHCs): Toward a Hydrogen-Free Hydrogen Economy. Acc Chem Res 2017, 50 (1), 74–85. https://doi.org/10.1021/acs.accounts.6b00474.

(3) Teichmann, D.; Arlt, W.; Wasserscheid, P.; Freymann, R. A Future Energy Supply Based on Liquid Organic Hydrogen Carriers (LOHC). Energy and Environmental Science. August 2011, pp 2767–2773. https://doi.org/10.1039/c1ee01454d.

(4) Crabtree, R. H. Nitrogen-Containing Liquid Organic Hydrogen Carriers: Progress and Prospects. ACS Sustain Chem Eng 2017, 5 (6), 4491–4498. https://doi.org/10.1021/acssuschemeng.7b00983.

(5) Crabtree, R. H. Hydrogen Storage in Liquid Organic Heterocycles. Energy and Environmental Science. 2008, pp 134–138. https://doi.org/10.1039/b805644g.

20_2455 Optimizing Li/electrolyte interface stability in solid-state batteries: The effects of solid electrolyte composition and particle size, anode surface, and interphases by spatial atomic layer deposition

Omer Ulas KUDU

Abstract

Current lithium-ion battery technology is reaching its limit in terms of energy density and safety^1,2. By replacing the flammable organic solvents with solid electrolyte (SE) layers, the risk of flammability is greatly reduced. Furthermore, the use of SEs potentially enables the use of alternative chemistries such as lithium metal anodes and high capacity/voltage cathode materials^3,4. Among the SE candidates, sulfide- and halide-based materials are investigated intensely owing to their high RT Li+ conductivities (>10-3 S.cm-1)^5–7. Before the ASSBs consisting of lithium metal anodes and sulfide/halide-based SEs can reach the market, chemo-mechanical and (electro)chemical stability issues at the Li/SE interfaces should be resolved7,8. Artificial solid-electrolyte-interphases deposited by atomic-layer-deposition (ALD) show encouraging results in terms of stabilizing the Li/SE interfaces^9–11. In our work, we first investigated the effect of the SE particle size on (electro)chemical stability at the Li/SE using electrochemical impedance spectroscopy and galvanostatic Li plating stripping experiments, post-mortem scanning electron microscopy and energy dispersive X-ray spectroscopy analyses. Secondly, we studied the effect of Li metal surface chemistry on (electro)chemical stability at the Li/SE interface by using different commercial thin Li anodes. In addition, we used spatial ALD to deposit ultra-thin (<5 nm) conformal coatings of AlOx and LiF on the best performing Li metal anodes, and tested their effect on (electro)chemical stability at the Li/SE (sulfide- and halide-based) interface.

1) J. Janek and W. G. Zeier, Nat. Energy (2023) https://www.nature.com/articles/s41560-023-01208-9.

2) Q. Wang, L. Jiang, Y. Yu, and J. Sun, Nano Energy, 55, 93–114 (2019) https://doi.org/10.1016/j.nanoen.2018.10.035.

3) J. B. Goodenough and M. H. Braga, Dalt. Trans. (2017) http://xlink.rsc.org/?DOI=C7DT03026F.

4) J. Janek and W. G. Zeier, Nat. Energy, 1, 16141 (2016) http://www.nature.com/articles/nenergy2016141.

5) R. Schlem et al., Adv. Energy Mater., 11, 2101022 (2021) https://onlinelibrary.wiley.com/doi/10.1002/aenm.202101022.

6) S. Ohno et al., Prog. Energy, 2, 022001 (2020) https://iopscience.iop.org/article/10.1088/2516-1083/ab73dd.

7) T. Koç, F. Marchini, G. Rousse, R. Dugas, and J. M. Tarascon, ACS Appl. Energy Mater., 4, 13575–13585 (2021).

8) Y. He, C. Lu, S. Liu, W. Zheng, and J. Luo, Adv. Energy Mater., 9, 1–40 (2019).

9) L. Han, C. Te Hsieh, B. Chandra Mallick, J. Li, and Y. Ashraf Gandomi, Nanoscale Adv., 3, 2728–2740 (2021).

10) J. Liu and X. Sun, Nanotechnology, 26, 24001 (2015) http://dx.doi.org/10.1088/0957-4484/26/2/024001.

11) Y. Jiang et al., Energy Storage Mater., 28, 17–26 (2020) https://doi.org/10.1016/j.ensm.2020.01.019.

21_262 Dielectric and phase engineering of van der Waals Sb2O3 films via PLD

Jing YU

Abstract

Van der Waals dielectrics are broadly utilized to retain the intrinsic properties of two-dimensional (2D) electronic devices. As a 2D inorganic molecular crystal, Sb2O3 have attracted many research interests as a promising high k gate dielectric with low-cost and CMOS compatibility. However, fabricating 2D Sb2O3 film with controllable dielectric constant and crystal phase is challenging. Here, we designed an oxygen-assisted PLD method for the phase-selective growth of α- and β- Sb2O3 thin films with super-high κ (>100) and good homogeneity by PLD. This is realized by tuning the oxygen gas pressure in the growth products to obtain two phases Sb2O3. This phase-controlled bottom-up synthesis offers a simple and efficient way for manipulating the relevant device structures and provides a general approach for producing other multi-phase materials with unique properties and allows us to characterize their intrinsic optical and electrical properties. Using dielectric and electrical measurements, we show that α phases exhibit good dielectric performance. Our Sb2O3 dielectric film not only show higher κ than other conventional dielectrics in terms of compatibility to CMOS processes, but also keeps their comparative advantages in the fabrication of high-performance electronic devices over conventional dielectrics. Our approach of fabricating Sb2O3 dielectrics using PLD may open promising opportunities to promote such unprecedented 2D devices to industry applications.

22_2769 NiMo/CoMoO4 Heterostructure with Confined Oxygen Vacancy for Active and Durable Alkaline Hydrogen Evolution Reaction

Ebrahim SADEGHI

Abstract

The sluggish kinetics of electrocatalysts in the alkaline hydrogen evolution reaction (HER) is a critical challenge to attain efficient progress in water electrolysis for carbon-neutral hydrogen production. Here, we present a high-performance and durable heterostructure of NiMo/CoMoO4 for the alkaline HER constructed via a two-pot in situ growth strategy on a nickel foam (NF). The density of active sites and the surface area of the hybrid catalyst augmented almost three-fold compared to those of pristine CoMoO4. The heterostructure composed of metallic NiMo and oxygen vacancy (Ov)-confined CoMoO4 facilitated the H adsorption on the metallic side and OH adsorption on the oxide side. The hierarchical hybrid catalyst on NF featured a low overpotential of 102 mV at 10 mA cm–2, approaching that of platinum on carbon (83 mV) in 1.0 M KOH. The turnover frequency of 0.012 s–1 at the overpotential of 100 mV of NiMo/CoMoO4 is six times higher than that of CoMoO4, 0.002 s–1. In addition, the fabricated heterostructure is a highly durable HER catalyst at 30 mA cm–2 for 30 h. The Faradaic efficiency recorded by a gas chromatograph at 10 and 100 mA cm–2 revealed nearly 100 and 86–95% hydrogen production efficiency, respectively.

23_277 In-situ monitoring and electrocatalytic hydrogen evolution enhancement mechanism study of Pd alloy thin film-based micro/nanodevices

Wen LUO

Abstract

In the face of the global energy crisis, the search for and utilization of renewable energy sources has become a hotspot of attention worldwide. Hydrogen, as a clean and renewable energy source, presents itself as one of the pathways to mitigate the energy crisis. The electrocatalytic hydrogen evolution reaction (HER) is a key process for hydrogen production via water electrolysis, and factors such as the number of active sites, effective reaction interface area, stress, defects, and doping of electrocatalysts all influence the reaction rate of hydrogen evolution to varying degrees. Pd-based alloy films, as a novel class of electrocatalyst materials, have attracted widespread attention in renewable energy solutions. Ultrathin two-dimensional (2D) materials have garnered significant interest due to their large surface area, unique electronic properties, and excellent mass transfer, providing distinct advantages in terms of morphological structure. This is particularly beneficial for surface-sensitive catalytic reactions. The interaction between Pd metal in the thin film structure and other alloy components forms a unique electronic structure and surface properties, thereby exhibiting outstanding performance in catalytic HER. The experimental results demonstrate a significant enhancement in the catalytic activity of the palladium film after sputtering platinum metal particles under alkaline conditions. The thin film sputtered for 30 s exhibits a overpotential of only 0.19 mV at an applied current density of 10 mA cm^-2, which is lower than the pre-sputtering value of 0.41 mV. This study offers a new avenue for developing efficient and cost-effective hydrogen production technologies, thereby making a positive contribution to addressing the global energy crisis.

24_2820 Free-standing WO3 electrode for efficient photo-rechargeable Li-ion batteries

Tariq SAJJAD

Abstract

The increasing demand for sustainable energy emphasizes the necessity for more efficient solutions in energy conversion and storage. Photo batteries with bi-functional electrode materials offer a unique approach to address this energy deficit by simultaneously harvesting and storing energy in a single device architecture. However, such photochargeable devices often face challenges related to poor charge separation and high charge recombination, stemming from inadequate interfaces and energy level mismatches.

To address these challenges, we developed a free-standing, photo-active WO3-based electrode capable of both energy harvesting and Li-ion storage. This electrode forms quasi-heterojunctions with carbon, establishing a pathway for desired charge separation, transport, and Li-ion storage. To further enhance performance, hole scavengers were introduced to suppress the charge recombination losses in the device, and a reusable split photocell was employed to reduce manufacturing costs. Under light, our battery showed a remarkable initial capacity of 6000 mAh g-1 at 0.1 C. Subsequently, we achieved cyclic stability at around 1800 mAg-1, which is three times higher than the theoretical capacity (693 mAg-1) and more than double the specific capacity (800 mAg-1) obtained under dark conditions. Even at a rate of 1 C, it maintains a high capacity of 621 mAh g-1 after 400 cycles, demonstrating a very low capacity fading of only 0.08% per cycle. Importantly, the Coulombic efficiency is ~ 90% during all the cycles. The higher capacity observed under light can attributed to the increased surface area, conductivity, and porous structure of WO3, providing a channel for efficient electron transport and energy storage.

25_2826 Transfer-free wafer-scale graphene electronics on sapphire

Oliver FENWICK

Abstract

The realisation of commercial graphene solid-state electronics devices has been held back by challenges of processing high-quality monolayer graphene at scale. However, progress in this area could lead to low power electronics that exploits the high charge mobility and small dimensions of graphene. In this work, we used wafer-scale graphene as the electrode in selected electronic devices, notably OLEDs [1] and memristors. The graphene was grown by Paragraf Ltd using tto produce high quality, monolayer graphene grown directly onto 50 mm sapphire wafers in batches of up to 37 wafers in metal-organic chemical vapour deposition (MOCVD) reactors. All processes in device production are compatible with semiconductor production lines, and we find graphene to be remarkably robust to these processes.

Graphene memristors in non-volatile memory or neuromorphic computing applications could ultimately offer high integration density as well as robustness against common memristor degradation mechanisms. The latter includes oxygen vacancy diffusion into the electrode and unwanted metal ion diffusion from the electrodes, both of which are prevented by the in-plane covalent bonding of graphene. Wafers containing 2520 memristors of different sizes with graphene electrodes were fabricated. The as-fabricated graphene memristors showed a high ON/OFF ratio of 107 ~ 108 when under a bias pulsing rate of 0.5Hz – 1Hz, robust endurance (switching remained stable after >2700 cycles), stability (no device degradation after 1.8 hrs of switching at 26Hz – 46Hz) and low voltage operation (low Vset ~1.6V and Vreset ~-1.55V).

Graphene is considered as a promising material for replacing ITO, which has long term supply issues due to its limited elemental abundance, but for this to become possible. The as-grown graphene was patterned using photolithography and its conductivity was enhanced by doping with nitric acid prior to deposition of the OLED stack. The electrical and optical performances of the as-fabricated graphene-based OLEDs were identical to control devices with conventional ITO anodes.

[1] Wafer‐Scale Graphene Anodes Replace Indium Tin Oxide in Organic Light‐Emitting Diodes, Weng Z et al., Advanced Optical Materials, 2101675-2101675 (2021).

26_2840 Tuning Electrochemical Hydrogen-Evolution Activity of CoMoO4 through Zn Incorporation

Sanaz CHAMANI

Abstract

Designing cheap, efficient, and durable electrocatalysts on three-dimensional (3D) substrates such as nickel foam (NF) for the hydrogen-evolution reaction (HER) is in high demand for the practical application of electrochemical water splitting. In this work, we adopted a simple one-step hydrothermal method to realize the incorporation of Zn into the lattice of CoMoO4 with various atomic concentrations—Co1-xZnxMoO4 (x = 0, 0.1, 0.3, 0.5, and 0.7). The morphological studies demonstrated that parent CoMoO4 consists of nanoflowers and nanorods. However, as the concentration of Zn increases within the host CoMoO4, the portion of nanoflowers decreases and simultaneously the portion of nanorods increases. Moreover, the substitution of Zn2+ in place of Co2+/Co3+ creates oxygen vacancies in the host structure, especially in the case of Co0.5Zn0.5MoO4, giving rise to lower charge-transfer resistance and a higher electrochemically active surface area. Therefore, among the prepared samples, Co0.5Zn0.5MoO4 on NF showed an improved HER performance, reaching 10 mA cm−2 at an overpotential as low as 204 mV in a 1.0 M KOH medium. Finally, the Co0.5Zn0.5MoO4 electrode exhibited robust long-term stability at an applied current density of 10 mA cm−2 for 20 h. The Faradaic efficiency determined by a gas chromatograph found that the hydrogen-production efficiency varied from 94% to 84%.

27_3003 Enhancement of Optical Parameters in Nanostructured CuSbS2 Material using Glancing Angle Deposition (GLAD) Technique: Investigationof the Substrate Temperature Effect.

Mouna IDOUDI

Abstract

Enhancement of Optical Parameters in Nanostructured CuSbS₂ Material using Glancing Angle Deposition (GLAD) Technique: Investigationof the Substrate Temperature Effect.

Mouna IDOUDI^1,*, Ferid CHAFFAR AKKARI¹, BrunoGallas²and Mounir KANZARI¹

¹ Université de Tunis El Manar, Ecole Nationale d’Ingénieurs de Tunis, Laboratoire de Photovoltaïque et Matériaux Semi-conducteurs, 1002, Tunis, Tunisie

²SorbonneUniversité, CNRS, Institut des NanoSciences de Paris, INSP, Paris, F-75005 France

^* Corresponding author: idoudimouna12@gmail.com

Abstract:

CuSbS₂ is a promising material that has increased significant attention in the field of photovoltaic, gas sensor, optoelectronics and energy conversion devices. It belongs to the family of chalcogenide semiconductors and exhibits unique optical and electronic properties. CuSbS₂ has emerged as a potential candidate for various applications due to its favorable bandgap, high absorption coefficient, and earth-abundant constituent elements.

According to these properties of this materials, our research is focused to fabricated and characterized CuSbS2 thin films by vacuum thermal evaporation onto glass substrates and heated at various temperatures (100, 150, 200, and 250°C) as well as unheated substrates with varying incidence angles of deposition (00-85°). The structuralstudy of the powder revealed thatCuSbS2 crystallizes with chalcostibite structure and it belongs to orthorhombic system. The space group of structure is Pnma. The reflection and transmission spectra show interference fringes in all samples, whereas the latter has absorption edges that rise with substrate temperature. The thicknesses of our thin films decrease as the substrate temperature rises. A high absorption coefficient of more than 105 cm-1 was reported. The band gap of CuSbS2 films is close to the optimum band gap (1.5eV) required for highest theoretical photovoltaic conversion efficiency.

Keyword: Substrate temperature, CuSbS₂, Thin film, GLAD, optical and structural properties.

28_44 Additive Engineering Mechanisms in Antimony Chalcogenide Solar Cells

Matthew SUTTON

Abstract

Antimony chalcogenide (Sb2X3, X = S, Se) solar cells are an attractive alternative solar cell technology with high inherent stability, good absorption and versatile deposition methods. However, the efficiency has lagged behind other technologies, and currently sits at a record of 10.7%. This record, along with an earlier 10.5%, were both achieved using chemical additives. The use of chemical additives, therefore, is of great importance to the drive of increasing the performance of these cells. However, often the chemical mechanisms behind these additives are not understood, or are assumed from the resultant film quality/cell performance, leading to an outcome which is less useful or even detrimental for researchers looking to build upon these works. In this work, we investigated the chemical mechanisms behind the use of ethylenediaminetetraacetic acid [ETDA], which was used to achieve 10.5% efficiency. We used a variety of chemical and physical techniques to probe the behaviours of EDTA and its interactions with the precursor materials, in order to find and/or design a molecule which can out-perform EDTA, and to understand why it does so.

29_470 Investigating the impact of AlInN/Si interface engineering on III-nitride solar cell efficiency

Fernando NARANJO

Abstract

In the pursuit of advancing the photovoltaic technology, the optimization of the interface between the constituent materials plays a fundamental role for improving the power conversion efficiency of heterojunction solar cells.

In this work, we study the effect of AlInN/Si interfaces on the solar cell performance. Three types of AlInN/Si interfaces were examined, each consisting of ~260 nm thick AlInN layers deposited by RF sputtering on Si(100) substrates. The first interface considers the direct deposition of the AlInN layer on the Si substrate (X1). For the second interface (X2), an intermediate layer of ~15 nm of amorphous silicon (a-Si) was deposited between the AlInN layer and the substrate. The deposition conditions and thickness of this a-Si was previously optimized by our group [1]. For the third interface (X3), the silicon substrate was subjected to nitrogen plasma during 5 min, considering that previous studies by our group indicated that prolonged nitridation times (up to 60 min), led to a significant degradation in the solar cell performance.

X-ray diffraction measurements of the samples show an AlInN wurtzite structure with Al mole fraction 0.3±0.05 oriented along the c-axis, with a degradation of the layer quality for the sample X3. Optical transmittance performed in samples deposited on sapphire show an apparent band-gap energy in the range of 2±0.1 eV. Furthermore, Transmission Electron Microscopy measurements reveal a discernible SiO_x layer of ~3 nm in sample X1. Contrastingly, the oxidation of the silicon substrate is reduced for sample X2 (partially oxidized). Finally, X3 lacks any oxide at the interface and instead, an amorphous layer of SiN_x of 4-5 nm is formed.

Structures were processed into solar cell devices of ~0.5 cm² area. Current-voltage (I-V) curves were measured in the dark and under 1-sun AM1.5G illumination. A slight decrease in series resistance occurs in sample X2, while a threefold increase is observed in sample X3. Conversely, the shunt resistance doubles from 1.1 kΩ.cm² to 2.1 kΩ.cm² for the nitridated device, but notably increases to 58 kΩ.cm² for X2.

Analyzing the illuminated I-V curves, the device X3 exhibits a fully degradation in performance, showing an S-shaped I-V curve. For X1 we obtained values of Jsc = 19.3 mA/cm², Voc = 0.41 V and FF = 41.5%, achieving a device efficiency of 3.3%. For X2 values of Jsc = 18.6 mA/cm², Voc = 0.37 V and FF = 54.3%, are obtained, with an improvement of efficiency to 3.8%. This improvement is tentatively associated with an increased band energy separation at the interface, and a reduction of the interfacial recombination rate [1].

In conclusion, devices with a nitridation >5 min suffer from a degraded electrical characteristic, while the incorporation of an a-Si interlayer enhances their performance. Further investigation into optimization strategies includes the shortening of the nitridation time.

[1] M. Sun et. al., Mater Sci. in Semicon. Processing, under review, 2024.

30_614 Scalable Solution-Processed Hole Transport Layer for Efficient Inverted methylammonium-free Wide Band Gap Perovskite Solar Cells

Yassine RAOUI

Abstract

Efforts to surpass the Shockley-Queisser (SQ) limit in single-junction solar cells have become a reality through tandem integration. In this context, inverted wide band gap (WBG) perovskite solar cells (PSCs) present a viable solution owing to their low-temperature fabrication process. However, the scalable solution processing of the hole transport layer (HTL) in p-i-n structured perovskite solar cells remains challenging. This study introduces a scalable solution processing approach for the HTL using Nickel oxide nanoparticles (NiOx-np) through a blade-coating (BC) technique. As a result, the BC process not only reduces the amount of solution usage but also offers an homogeneous surface, a crucial factor in supporting self-assembled monolayer molecule (Me-2PACs) deposition. Consequently, methylammonium-free inverted wide-bandgap PSCs achieved a champion power conversion efficiency of 18.50% based on the HTL scalable solution-processed of NiOx-np, demonstrating less hysteresis compared to traditional spin-coating techniques. This innovative approach not only propels the efficiency of perovskite solar cells but also promises a low-cost, high-efficiency, and scalable method for the hole transport layer in inverted wide band gap configurations.

31_684 ZnMn2O4 and LiMn2O4 thin films as electrodes in transparent supercapacitors for integration into photosupercapacitors

Francisco De Paula MARTIN JIMENEZ

Abstract

Supercapacitors (SCs) are alternative devices to batteries for energy storage due to their high power density, high stability and cyclability, although with the drawback of low energy density. Thin film supercapacitors have attracted interest for their potential use in transparent electronics. Manganese oxide-based materials are interesting for SCs due to their high theoretical specific capacitance, excellent capacitive performance in aqueous electrolytes, multivalence, low cost, and environmental friendliness. In this work we have obtained symmetric and asymmetric supercapacitors whose electrodes are formed by thin films of ZnMn₂O₄ and LiMn₂O₄ grown on ITO/Glass by spray pyrolysis. The selected thin film thickness showed the best compromise between transparency, surface electrical resistance, and specific capacitance. Two types of electrolytes have been used: an aqueous Na₂SO₄ solution embedded in an acetate membrane, and another of a solid nature obtained by mixing polyvinylpyrrolidone (PVP) and LiClO₄. The electrolyte used plays an important role not only on the capacitance but also on the chemical stability of the electrodes and therefore on the percentage of retention of the specific capacitance with the galvanostatic charge-discharge cycles (GCD).

It has been determined in these supercapacitors that the main contribution is the pseudocapacitance, and would be a consequence of the redox processes involving the reversible intercalation/deintercalation of Zn²⁺ or Li⁺. Lithium ions, with the smallest non-hydrated radius, can be reversibly intercalate/deintercalated in LiMn₂O₄, in the case of ZnMn₂O₄ it can reversibly replace Zn²⁺.

The supercapacitors were formed by 30 nm ZnMn₂O₄ films with 72% transmittance in the visible (D65, integrated value from 380 nm to 770 nm), a specific capacitance value of 752 F g^-1, three-electrode electrochemical cell, and 70% retention in 3000 GCD cycles at 0.5 A g^-1; and LiMn₂O₄ thin films with 74% transmittance in the visible (D65, integrated value from 380 nm to 770 nm), which achieved specific capacitance values of 500 F g^-1, three-electrode electrochemical cell, and 50% specific capacitance retention for 3000 GCD cycles at 0.5 A g^-1.

A problem with this type of thin film supercapacitors is the drop in specific capacitance in the device relative to that expected based on the specific capacitance determined in the three-electrode electrochemical cell. It was shown that the retention of specific capacitance in the supercapacitors depends on the type of electrolyte used. These mixed-oxide thin film supercapacitors were integrated with dye solar cells to obtain photosupercapacitors, devices with the ability to capture and store solar energy in a single device.

This research was financed by PID2020–117832RB-100 (MCIN/AEI/10.13039/501100011033), Spain.

32_73 Bi2S3/Cu2S@carbon nanotubes photocatalytic coatings for wastewater treatment

Alexandru ENESCA

Abstract

The diversification of pollutants type and concentration in wastewater has underlined the importance of finding new alternatives to traditional treatment methods. Advanced oxidation processes (AOPs), among others, are considered as promising candidate to efficiently remove organic pollutants such as pharmaceutical active compounds (PhACs) from wastewater.

The present work focus on the development of Bi2S3/Cu2S heterostructure using carbon nanotubes (CNs) as nucleation sites for the metallic semiconductors. The photocatalytic activity was testes toward ampicillin and amoxycillin from wastewater. The diffraction analysis indicates the presence of crystalline structure corresponding to the heterostructure components. The coatings have a porous morphology and the specific surface varies from 38.2 m²/g for WO₃ to 247 m²/g for Bi₂S₃/Cu₂S@carbon nanotubes.

The photocatalytic experiment were made in the presence of UV-Vis irradiation and the results indicate that Bi2S3/Cu2S@carbon nanotubes is able to remove 86.3% ampicilline in 10h, and 88.54% of amoxycilline. The results indicate that the use of carbon nanotubes as nucleation sites serve as triple benefits: (1) homogenous surface distribution, (2) higher active surface area and (3) energy network for the charge carriers involved in oxidative species generation.

AP03_Poster Session

Date: 30-05-2024

Time: 16:30-18:30

Room: ETOILE - FIRST FLOOR

Click here to have the Symposium details as a pdf

01_1030 Enhanced efficiency in large-area CIGS solar cells through controlled structure of Ag network electrode

Yoo HYESUN

Abstract

The efficiency disparity between lab-scale solar cells and modules arises from dead areas generated through repetitive P1, P2, P3 processes. While Cu(In,Ga)Se₂ (CIGS) modules usually use a monolithic approach, drawbacks like increased resistance with longer TCO lengths and consequent dead area formation significantly contribute to the efficiency gap. With monolithic width conventionally limited to ~5 mm, innovative strategies, such as applying a metallic grid on TCO, are explored to increase monolithic width and reduce TCO usage.

Ongoing research primarily uses photolithography for effective metallic grid application, but this study proposes a simpler method: utilizing acrylic resin solution for natural drying and crack formation, serving as sacrificial templates for metallic network fabrication. Applying a metallic grid is expected to decrease TCO sheet resistance, leading to increased FF and simultaneous decreased J_sc, determining efficiency. This study examines the impact of TCO sheet resistance, transparency, and their Figure of Merit (FOM) on solar cell efficiency. Surprisingly, FF is more influenced by FOM than sheet resistance, but a higher FOM does not consistently result in higher efficiency. Further exploration identifies an optimal covered area enhancing CIGS efficiency, with observed changes in V_oc, J_sc, FF related to covered area.

Applying this insight to a solar cell with an area expanded to over five times (from 0.2025 to 1.0609 cm², total area), it is confirmed that FF improves with the increase in metallic network density, especially when the covered areas of Ag networks are similar. In experimental validation, the application of Ag networks on CIGS solar cells enhances efficiency from 12.0% to 12.7% without any anti-reflection coating or PDT process. Moreover, reducing AZO from 350 to 150 nm in CIGS solar cells, applied with Ag networks, elevates efficiency from 10.5% to 11.6%, highlighting the significance of FF increase compensating for J_sc reduction. This study illuminates the intricate relationship between covered area, metallic network density, and performance enhancements in CIGS solar cells. The proposed approach offers a promising avenue for optimizing large-area solar cell efficiency by controlling metallic grid application and has the potential to bridge the efficiency gap between lab-scale solar cells and modules.

02_1106 Stereo lithographically assisted printed technology for energy conversion and storage application

Suvani SUBHADARSHINI

Abstract

The pursuit of uncovering a carbon-free energy source for relinquishing the soaring global energy demand has become a subject of significant research interest. Keeping in mind the irreversible outcomes of the irrational energy generation; via coal sources; carbon-less energy production remains at the forefront of the sustainable research and development. A majority of sustainable energy research is directed towards the generation of hydrogen gas and oxygen gas utilizing the renewable sources of energy like sunlight, wind energy, nuclear energy, sound energy, and mechanical energy to name a few. Secondly, the sustainable research is also favoured towards efficient energy storage in supercapacitors devices (SCD). The SCDs store energy and provide continuous supply of energy when the generation of hydrogen and oxygen gas becomes insufficient. Photo/electro-catalytic water splitting helps in generating fuels like H2 and O2 directly by utilizing sunlight. They act as vital technologies for achieving clean energy economy. The biggest problem encountered for the overall water splitting lies in the fact that it demands a large potential exceeding 1.8V. Hence, the aim of material research is to design non noble metal-based material which would be used for complete water splitting units and achieve the splitting in the full cells at low potential values. Hence in this present work we have focussed on transition metal chalcogenides. Electrode fabrication process is associated with a major issue cantered around the physical state in which the catalyst materials are obtained. These materials are usually available as powders. Hence, they require support surfaces or substrates which are conductive in nature. Hence, to take care of the mentioned issues we introduce additive engineering for the construction of the substrate or the matrix. We have focussed on stereo lithographically assisted (SLA) printing of the substrate in the desired patterns in order to obtain free-standing catalysts and 3D printed supercapacitor devise. As 3D printing gas not been explored much in the field of energy storage and conversion hence the present work will open a myriad of opportunities for exploring more additive manufacturing techniques add apply them for constructing metal-free substrates for energy research.

03_1162 Investigation of p-GaN/AlN/AlGaN/GaN MOS-HEMT on GaN Substrate

Jyun-Yi LEE

Abstract

The fabrication of the enhancement-mode (E-mode) and depletion-mode (D-mode) metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) by p-GaN/AlN/AlGaN/GaN structure on the novel GaN substrate has been demonstrated. In the research, the etching stop layer technology is used to not only effectively control the p-GaN etching, but also improve the surface etching uniformity. The gate oxide film, Al2O3, deposited by using atomic layer deposition (ALD) not only reduces current leakage, but also increases the operating voltage of E-mode devices. In order to analyse the performances of the E/D-mode MOS-HEMTs, I-V characteristics, subthreshold behaviour, gate leakage current, low-frequency noise, radio-frequency performance, and reliability measurement have been conducted. According to these results, the proposed p-GaN/AlN/AlGaN/GaN structure can be applied to electronic products such as logic circuits that require both E-mode and D-mode characteristics.

04_1193 Understanding the Li Ion Storage Mechanism in Ruddlesden-Popper Structured Li2La2Ti3O10

Mi JANG

Abstract

In the current landscape of energy storage technology, research into innovative anode materials for enhancing the energy density and lifespan of lithium-ion batteries (LIBs) is gaining increasing momentum. In this study, Ruddlesden-Popper structured Li₂La₂Ti₃O₁₀ (RPLLTO) is presented as a new anode material for LIBs. The material was synthesized through an ion exchange reaction method, and as a result of powder X-ray Diffraction(XRD) Rietveld refinement, it was confirmed to have a layered perovskite structure including a Li ion path layer. As a result of electrochemical property evaluation, it showed a unique charge/discharge reform with a capacity of 170 mAh·g^-1 and two plateau voltages. X-ray Absorption Near Edge Structure(XANES) was analyzed to identify the Li ion storage reaction corresponding to the two plateau voltages, and the reduction reactions of Ti⁴⁺/Ti³⁺ and Ti³⁺/Ti²⁺ were confirmed, respectively. Analysis of crystal structure changes during lithiation using In-situ XRD and Extended X-ray Absorption Fine Structure(EXAFS) revealed that RPLLTO undergoes complementary expansions along the a/b axes and contractions along the c axis, leading to about a 1.8% volume change. This structural stability is evidenced by an 88% capacity retention after 1000 cycles. This study is a report on the Li ion storage ability of RPLLTO and contributes to the development and scalability of perovskite anode materials of various compositions and structures.

05_1269 Unraveling Morphological Instability in Polyol-Grown Silver Nanowires: A Path to Enhanced Stability for Transparent Conducting Materials Applications

François BALTY

Abstract

Transparent conducting materials play a pivotal role in various applications including energy harvesting. Among them, metallic nanowire networks on optically transparent substrates have garnered considerable attention in the last decade, especially those based on polyol-grown silver nanowires. Indeed, in addition to their remarkable combination of excellent electrical conductivity with high optical transparency, they can be synthesized via solution-based processes that enable cost- and energy-effective manufacturing, making them viable even for large-scale production. Despite their promising attributes, their susceptibility to morphological instability at relatively low temperatures, typically in the range of 300°C, poses a significant technological challenge, limiting their applicability. This instability has been acknowledged in the literature and is often associated with Rayleigh's description of liquid jet morphological instability. However, this model is only partially accurate as its numerical predictions hold true only in terms of order of magnitude. Another theoretical description, proposed by McCallum et al. in 1996, offer a more accurate depiction of this phenomenon. In this communication, we delve into experiments we conducted on polyol-grown silver nanowires to demonstrate the superior alignment of McCallum et al. model with empirical measurements compared to Rayleigh's theory. The mean discrepancy between the instability wavelength predicted by Rayleigh deviates from our experimental results by 22%, whereas it is only 6.6% with McCallum et al.’s model. This refined depiction holds profound implications, providing a robust theoretical framework to comprehend and address the morphological instability in metallic nanowires. By offering insights into the fundamental aspects governing nanowire stability, our results pave the way for innovative strategies to enhance their robustness, thereby overcoming a critical barrier in the development of transparent conducting materials.

References :

V. H. Nguyen et al. “Advances in Flexible Metallic Transparent Electrodes”. Small, 18, 2106006 (2022).

M. S. McCallum et al. “Capillary instabilities in solid thin films: Lines”. J. Appl. Phys. , 79, 7604–7611 (1996).

07_1368 High-Throughput Screening of REBCO Superconductors via Combinatorial Inkjet Printing

Emma GHIARA

Abstract

In the realm of material design, high-throughput screening (HTS) has emerged as a pivotal paradigm, marking a transformative shift towards accelerated discovery, development, and optimization of materials through data-driven approaches. This study investigates the potential of drop-on-demand inkjet printing (IJP) for conducting combinatorial investigations, leveraging its versatility to fabricate compositionally graded materials with precise spatial control. Specifically, we utilize IJP to blend precursor solutions of superconducting REBCO with diverse rare earth (RE) elements, resulting in the production of Y(1-x)GdxBa2Cu3O7 superconducting thin films. The uniformity of deposition in combinatorial samples is designed with computational methods and confirmed by energy-dispersive X-ray spectroscopy (EDX) and high-resolution X-ray diffraction (XRD) [1].

Emphasizing the efficacy of this approach, our exploration extends to optimizing the epitaxial growth of high-temperature REBCO superconducting films using the novel transient liquid assisted growth (TLAG), a method which has demonstrated ultra-fast growth rates of up to 1000 nm/s [2,3]. Advanced characterization methodologies, including in situ synchrotron growth experiments, are customized to complement the combinatorial strategy, demonstrating their indispensable role in HTS schemes. The presented experimental framework plays a fundamental role in generating extensive datasets, laying the foundation for the integration of machine learning in material design.

[1] A. Queralto, et al. ACS Appl. Mater. Interfaces 13, 9101, https://doi.org/10.1021/acsami.0c18014

[2] L. Soler, J. Jareño, J. Banchewski et al. Nat Commun 11, 344 (2020). https://doi.org/10.1038/s41467-019-13791-1

[3] S. Rasi, A. Queralto et al. Adv. Sci. 9, 2203834. https://doi.org/10.1002/advs.202203834

The authors acknowledge the funding of this research by ERC-2014-ADG-669504 Ultrafast growth of ultrahigh performance superconducting tapes (ULTRASUPERTAPE), H2020-ERC Proof of Concept Industrial Manufacturing Process for A high temperature superconducting Coated conductors Technology (IMPACT), HORIZON ERC Proof of Concept “Scalable Method for Synthesis of multifunctional colloidal INKs for Superconductors, SMS-INKS” and FUNFUTURE-FIP-2020 High-Throughput Screening and Data-Driven Optimization of High Temperature Superconducting Coated Conductors (DATOPTICON).

08_1381 Plasma-processed Ni-based catalytic film for urea oxidation reaction

Dan LI

Abstract

Electrocatalytic water splitting for H2 generation and CO2 electroreduction in chemical production play crucial roles in sustainable energy systems. However, the oxygen evolution reaction (OER) at the anode poses a challenge due to low energy conversion efficiency, limiting broader practical applications. An alternative anodic reaction with high thermodynamic favorability is the urea oxidation reaction (UOR). Unfortunately, current highly efficient nickel-based catalysts face challenges related to dependence on specific nickel oxidation states and passivation reactions at high potentials, rendering urea oxidation inefficient and impractical.

In our recent investigation, we employed advanced characterization techniques, encompassing in-situ electrochemical impedance spectroscopy, in-situ Raman spectroscopy, quasi in-situ X-ray diffraction (XRD), quasi in-situ X-ray photoelectron spectroscopy (XPS), and post-reaction characterization to scrutinize the conventional Ni-based catalytic film. Our exploration delved into comprehending the characteristics of Ni(OH)2 and analogous compounds such as NiFe-LDH under anodic reaction conditions, encompassing their electrochemical behavior and materials evolution. Mechanisms such as the transfer of catalytic active sites with material phase transitions and the reasons for passivation reactions at high potentials were discussed. Furthermore, we incorporated plasma etching techniques and implantation methods to modify the catalysts, enhancing their catalytic activity, particularly in terms of achieving high current output at elevated voltages. Utilizing the modified catalytic electrodes, the assembled urea oxidation coupled hydrogen production device exhibited excellent energy-saving and passivation-avoidance characteristics, highlighting the application potential of the prepared catalytic electrode.

Overall, our work provides both theoretical and experimental evidence supporting the rational design and improved utilization efficiency of catalysts. Additionally, our findings suggest that plasma treatment emerges as a valuable tool for materials modification, altering the electrochemical properties of catalysts.

References

[1] Dan Li, Paul K. Chu, et al., Advanced Functional Materials, 2023, 2313680

[2] Dan Li, Paul K. Chu, et al., Applied Catalysis B: Environmental, 2023, 324, 122240

[3] Dan Li, Paul K. Chu, et al., Journal of Energy Chemistry, 2022, 71, 150-158

09_1413 Electrochemical Performance Analysis of High-Voltage 3D Printed Supercapacitors: Aqueous Electrolytes versus Sustainable 3D printed Deep Eutectic Solvent

Chirag MEVADA

Abstract

Electrolytes are among the key components significantly affecting the performance of supercapacitors (SCs). SCs employ a categorization of electrolytes that falls into three primary classes: aqueous, organic, and ionic liquids. Explorations into novel electrolytes, known as deep eutectic solvents (DESs), have commenced with the objective of elevating the operating voltage of SCs. These DESs are under investigation because of their impressive electrochemical stability, environmental friendliness, and cost-effectiveness, all of which suggest the potential for improved device performance. The unique advantage of DES is its ability to enable the creation of energy cells under normal atmospheric conditions, unlike energy cells that depend on organic electrolytes and require glove-box setups for ionic liquids. To investigate the impact of DES, we employed a synthesized choline chloride-urea (1:2 molar ratio) DES known as Reline and compared its electrochemical performance with an aqueous electrolyte (NaCl:water: 1:5 wt.%.). The electrodes were fabricated through a 3D printer (Neotech AMT GmbH, Germany) using activated carbon (Kuraray YP-80F) ink, which was subsequently coated onto a current collector made of graphite ink. The DES electrolytes were printed using the 1K dispenser tool of a 3D printer without the addition of a binder, while the loading of aqueous electrolytes was done using a micropipette. To evaluate the electrochemical characteristics of the electrolyte, 3D-printed devices with dimensions of 50 mm × 80 mm × 0.4 mm were fabricated. The maximum capacitance achieved through galvanostatic charge-discharge measurements was 1325 ± 20 mF at a constant current of 1 mA for DES (2 SCs in series), significantly surpassing the capacitance observed when the SC fabricated with aqueous electrolyte, which measured at 690 ± 20 mF (3 SCs in series). Furthermore, the equivalent series resistance for DES and aqueous electrolyte was found to be 33 ± 2 Ω and 50 ± 2 Ω, respectively. The obtained results highlight the significance of the DES as a supercapacitor electrolyte that is safe, environmentally friendly, low-cost, and anticorrosive, with competitive features such as ease of synthesis and operation in ambient conditions, availability, and biodegradability. The fabricated devices can be useful for running low-power wireless sensors as a substitute for environmentally harmful lithium-ion batteries.

10_147 The Prospects of Magnetron Sputtering for Developing Advanced Catalysts for (photo)electrochemical water splitting

Farid ATTAR

Abstract

Recent efforts actively pursued developing cost-effective catalysts for oxygen evolution reactions (OERs) and hydrogen evolution reactions (HERs) for alkaline water electrolysis. However, fabricating efficient and stable catalysts remains a major challenge. Most recent studies reported intricate synthesis procedures for catalysts development, complicating their implementation in practical industrial applications. The potent technique of magnetron sputtering offers an effective approach for producing intricate catalysts in a single step. In this study, we employ magnetron tri- and co-sputtering to synthesise trimetallic NiFeMoN and NiMoC, which serve as proficient catalysts for OER and HER. By utilising the design of experiments (DOE) and response surface methodology (RSM), we optimised the synthesis parameters, with Analysis of Variance (ANOVA) confirming the model's accuracy. The optimised sputtered OER and HER catalysts demonstrated superior performance with a low overpotential of 216 mV and 26 mV at 10 mA cm^-2, respectively. Furthermore, both catalysts exhibited excellent stability of over 7 days at 10 mA cm^-2 and 100 mA cm^-2, illustrating their potential for application in industrial electrolysers. Further statistical analysis confirmed the significance and relative importance of the synthesis parameters. Our detailed characterisation studies reveal uniform distribution of elements and demonstrate the role of nitrogen and carbon on OER and HER performance by vacancy generation and electric conductivity improvement. The sputtered catalysts, which also could provide chemical protection for semiconductors against corrosion in harsh alkaline electrolytes, are integrated into decoupled photoelectrodes for photo-electrochemical (PEC) water splitting. The PEC results show high applied-bias photon-to-current efficiency (ABPE) over 70 hours of stability. To examine our catalyst at high current density, the performance of HER catalyst is evaluated at zero-gap alkaline water electrolyser. The cell voltage for current density of 0.5 A cm^-2 is 1.78 which is stable for 70 h at 70°C. This work highlights the profound potential of employing magnetron sputtering in developing other complex catalysts for different energy conversion systems such as N2 fixation and CO₂ conversion.

11_1656 Low-temperature plasma constructed Ni-doped W18O49 nanorod arrays to boosted electrocatalytic oxygen evolution and urea oxidation

Qingdong RUAN

Abstract

Low-temperature plasma doping controls electrocatalytic active sites of the electrocatalyst are receiving widespread attention. In this study, Ni-doped W18O49 nanorod arrays were prepared using a hydrothermal method followed by low-temperature plasma treatment. The results indicate that Ni doping induces the generation of defects and amorphous structures in W₁₈O₄₉, leading to an increase in oxygen defects. Furthermore, accoupling with high valence W result in Ni active site transfer to more NiOOH at low overpotential during OER, enables CC/WO-Ni-4 exhibit excellent OER performance and its UOR performance was further explored. Specifically, to deliver 10 mAcm^-2 current density, it only requires low overpotential of 265 mV for OER in 1.0M KOH, and it merely needs ultra-low potential in 1.0 M KOH + 500 mM urea, which is 172 mV lower than the required potential in 1.0M KOH. Low-temperature plasma treatment technology provides new ideas for the preparation of highly efficient OER and UOR electrocatalysts.

12_1681 Improved performance of LiFePO4 cathodes with ultrathin atomic layer deposited films

Prangya Parimita SAHOO

Abstract

LiFePO4 (LFP) cathodes, with a theoretical capacity of 170 mAhg-1, are stable, safe, and eco-friendly. Surface modification using ultrathin alumina films by atomic layer deposition (ALD) enhances Li-ion charge transfer and rate performance in both half-cell and full-cell configurations, contributing to extended cycle life and excellent charging/discharging in Li-ion batteries.

The half cells used in our study consisted of Li anode and LFP cathodes whereas for full cell configuration graphite and LFP electrodes were used as anode and cathode, respectively. The LFP electrode had a thickness of 70 μm and the average LFP particle size was 2 μm (commercial NANOMYTE BE-60E (NEI Corp.).

Ultrathin Al2O3 films were grown on LFP cathodes by ALD at 100 °C using trimethyl aluminum and water vapors. The growth rate of the Al2O3 films was 0.1 nm/cycle. ALD layer thickness linearly depends on the number of cycles, ranging from 0.2 to 5 nm for 2 to 50 cycles.

Galvanostatic charging/discharging experiments were performed to evaluate the rate capability of the electrodes. Pristine and Al2O3 coated LFP electrodes were laser cut to 18 mm diameter circular electrodes, inserted in the electrochemical test cells PAT-Cell (EL-CELL), and tested using PAT-Tester-x-8 analyzer. LFP with Al2O3 protecting layers was compared to the pristine LFP electrode in half-cell and full-cell configurations. The electrodes protected by Al2O3 film exhibited superior rate capability than the pristine sample. High-temperature charging/discharging measurements confirmed better cycling stability of the Al2O3 coated cathodes.

The authors acknowledge the support from VEGA 2/0162/22 and APVV-20-0111 projects.

13_1843 Evaluation the Impact of Fe Catalyst Dimension on the Graphitization to Anode Materials for Lithium Ion Batteries Applications

Jui-Yu TUNG

Abstract

Coffee grounds, derived from agricultural wastes, were employed as the precursor material for lithium-ion batteries (LIBs) in this study. Generally, complicated purification processes involving carbonization and graphitization as well as energy consumption were required to utilize coffee grounds as an anode material. Alternatively, this study proposed improved graphitization processes by applying Fe powders with diameter ranging from 35-45 nm, 6-8 μm, or 60 μm as catalysts. In addition, the lower graphitization temperature was investigated at 1500, 2000, and 2500°C, apart from the conventionally employed temperature for graphitization industrially (2500-2800°C). The results showed that the Fe-catalyzed carbon samples made by coffee grounds, graphitized at 1500°C with the diameter of 6-8 μm, demonstrated an outstanding specific discharge capacity of 332 mAh·g^-1, comparing with the commercially available synthetic graphite that delivered 350 mAh·g^-1.

The rationale to prepare Fe-catalyzed carbon is because carbon materials exhibit industrial significance for the applications as electrodes in energy storage systems including LIBs, sodium-ion batteries (SIBs), and electric double-layer capacitors (EDLCs). Different carbon allotropes are categorized according to their morphology, structure, and types of chemical hybridization, such as graphite, graphene, diamond, carbon nanotubes, and amorphous carbons.

In addition, coffee grounds (CGs) were employed as a precursor for the synthesis of carbon-based materials. Initially, coffee grounds were collected and carbonized in the furnace at 1000°C under an argon atmosphere with a flow rate of 100 Lh^-1. For the graphitization, the carbonized cCGs were mixed with Fe powder with 1:1 ratio in mass. Different diameter of Fe powders was utilized as catalysts: 35-45 nm, 6-8 μm, or 60 μm. The graphitization temperature was selected at 1500, 2000, or 2500°C, and the resultant samples were denoted as g-(Fe-cCGs)_1500, g-(Fe-cCGs)_2000, and g-(Fe-cCGs)_2500, respectively. Furthermore, the as prepared g-(Fe-cCGs) ink were then constructed on dendritic copper foil, served as the current collector. The electrochemical analyses on the g-(Fe-cCGs)||Li metal cells were conducted using Swagelok T-cells configured with a three-electrode system. The performance at various C-rates for the g-(Fe-cCGs) was assessed through constant current charge/discharge cycling (CCC) experiments, employing specific (dis)charge currents ranging from 0.1 to 10 C.

The effects of graphitization temperature and size of Fe catalyst on the crystallinity, structural, and surface properties of g-(Fe-cCGs) and its influence on the electrochemical performance when used as anodes in LIBs were investigated. With the graphitization temperature increased from 1500 to 2500°C, the degree of graphitization increased from 65 to 90%. Furthermore, g-(Fe-cCGs)_1500 with diameter of 6-8 μm on Fe catalyst delivered a remarkable specific discharge capacity of 332 mAh·g^-1.

14_223 P3-Na0.45Ni0.2Mn0.8O2/Na2SeO4 Heterostructure Enabling Long-Life and High-Rate Sodium-Ion Batteries

Tianyi SONG

Abstract

Sodium-based layered oxide cathodes are competitive candidates for commercial sodium-ion batteries owing to their high theoretical capacities, low costs, and simple synthesis. P3-type layered oxides with large open channels enable fast Na+ transport and hence good rate performance. However, the lower crystal symmetry of P3-type oxides and variation of Na+ contents in the Na layer during desodiation/sodiation lead to large electrostatic repulsion changes between TMO2 slabs (TM=Transition Metal), resulting in irreversible phase transitions, and fast performance degradation. Herein, a potential Na+ conductor, Na2SeO4, is first found to be easily in situ grown on P3-Na0.45Ni0.2Mn0.8O2 to form a novel heterostructure, P3-Na0.45Ni0.2Mn0.8O2/Na2SeO4. The synergy between P3-Na0.45Ni0.2Mn0.8O2 and Na2SeO4 functions in promoting Na+ diffusion and suppressing P3-O3 phase transitions upon deep sodiation, which results in recorded high-rate capability (68.2% capacity retention with retained 83.9 mAh g−1 capacity at 6400 mA g−1) and superior cycling stability (capacity retention 75% after 1000 cycles) among all reported P3-type cathodes. Thus, it is believed that this novel heterostructure design opens a new pathway to promote practical applications for layered oxide cathodes in sodium-ion batteries.

15_2239 Growth of epitaxial superconducting REBa2Cu3O7-X layers at ultrafast growth rates

Carla TORRES

Abstract

High Temperature Superconducting materials are ready to be used for many applications. However, their manufacturing costs are still too high due to the need of high thickness epitaxial films of km-length. We are developing a novel method, the Transient Liquid Assisted Growth (TLAG), which is able to grow epitaxial REBa₂Cu₃O_7-X (REBCO) films at even 2000 nm/s with controlled supersaturation conditions and it is compatible with low costs chemical solution deposition. The TLAG is a non-equilibrium process, so kinetic parameters play a relevant role [1,2].

We use an environmentally friendly chemical solution using propionate salts, giving us a highly reproducible deposition and pyrolysis process that ensures a homogeneous nanocrystalline solid prior to the TLAG process [3].

In this work, we modify the rare earth ion (RE=Y, Gd) to change the supersaturation conditions during the TLAG process and facilitate the epitaxial growth. The TLAG give us the possibility to work in a wide range of oxygen pressure and temperature. So, we can explore different growth conditions and correlated them with the layer morphology, microstructure and superconducting properties. Advanced TEM was used to evaluate the defect microstructure, and SQUID magnetometry and electrical transport measurements where performed to evaluated the superconducting properties. In particular, we have explored the epitaxial window for both RE, yttrium and gadolinium, which modify the RE solubility in the transient liquid, supersaturation conditions, nucleation density and growth rates.

In-situ XRD synchrotron experiments were carried out at Soleil and Alba, in a designed system installation built on a mobile rack, with a 2D detector acquiring images in the range of 100ms/image to 9ms/image. Additionally, this installation incorporates an in-situ mass spectrometer and an in-situ resistivity measurement. These experiments enable us to evaluate the phase evolution from XRD during the growth process as well as the evolution of the resistivity which enables us to determine the growth rates and correlate it with the microstructural and superconducting properties. Our present understanding of the ultrafast growth mechanisms associated to the REBCO TLAG process will be reported.

[1] Soler, L., et al. Nat. Commun 2020, 11, 344.

[2] Rasi, S., et al. Adv. Sci. 2022, 2203834.

[3] Saltarelli, L., et al. Applied Materials & Interfaces 2022, 14 (43), 48582-48597

16_2290 Impact of molecular weight on the solid state structure in semiconducting polymers for photovoltaics

Matteo SANVITI

Abstract

Semiconducting conjugated polymers garnered through the years considerable scientific impact owing to their remarkable electronic properties, stability, and processability[1]. Nevertheless, their functional properties are strongly related to the internal structure, which is of no trivial interpretation, showing in some cases complex configurations such as paracrystallinity or semi-paracrystallinity[2]. Consequently, ensuring certain standards out of these materials necessitates a fundamental comprehension of the structural arrangement of their complex phases, which are also dependent on molecular weight[3].

In this study, we analyse two semiconducting polymers at different molecular weights, PBnDT-FTAZ and D18(Cl), which respectively exhibit lower and higher degrees of order in their chain packing. The main goal of the study is to point out the impact of the chain length on the structure of these polymers, providing valuable information about possible trends for formulation/structure-like predictions. The investigation of the intrinsic configurational order was carried out with the help of GIWAXS (also by in-situ temperature ramp experiments) and AFM techniques, while fast scanning calorimetry allowed the investigation of all those processes involving phase transitions or internal dynamics. The resulting set of results reveals different thermal processes which are directly linked to the inherent structure of the polymers themselves. Furthermore, the in-depth characterization of melting and crystallization phenomena provides insights into how molecular weight influences the kinetics of these phase transitions.

This research contributes to the essential comprehension of semiconducting polymers, offering valuable insights into their complex structures and thermal behaviours, thereby creating opportunities for improved design and application of these materials in present and future technologies.

References

[1] R.M. Pankow, B.C. Thompson, The development of conjugated polymers as the cornerstone of organic electronics, Polymer (Guildf) 207 (2020) 122874. https://doi.org/10.1016/j.polymer.2020.122874.

[2] Z. Peng, L. Ye, H. Ade, Understanding, quantifying, and controlling the molecular ordering of semiconducting polymers: From novices to experts and amorphous to perfect crystals, Mater Horiz 9 (2022) 577–606. https://doi.org/10.1039/d0mh00837k.

[3] F.P.V. Koch, J. Rivnay, S. Foster, C. Müller, J.M. Downing, E. Buchaca-Domingo, P. Westacott, L. Yu, M. Yuan, M. Baklar, Z. Fei, C. Luscombe, M.A. McLachlan, M. Heeney, G. Rumbles, C. Silva, A. Salleo, J. Nelson, P. Smith, N. Stingelin, The impact of molecular weight on microstructure and charge transport in semicrystalline polymer semiconductors-poly(3-hexylthiophene), a model study, Prog Polym Sci 38 (2013) 1978–1989. https://doi.org/10.1016/j.progpolymsci.2013.07.009.

17_2400 Pulsed Laser-Deposited NiCoCuFeMoMn High Entropy Alloys: Tailored Synthesis and Electrochemical Proficiency for Hydrogen and Oxygen Evolution Reactions

Hossein MAHDAVI

Abstract

High entropy alloys (HEAs), a distinctive class of alloys incorporating more than five principal elements in equimolar or non-equimolar ratios, have garnered considerable attention for their diverse applications. Benefiting from synergistic effects, severe lattice distortion, and high-entropy and cocktail effects, HEAs have recently demonstrated significant potential in various electrocatalytic applications, including Hydrogen Evolution Reaction (HER), Oxygen Evolution Reaction (OER), Nitrogen Reduction Reaction (NRR), and CO2 Reduction Reaction (CO2RR).

This study delves into the electrocatalytic potential of NiCoCuFeMoMn high entropy alloy thin films synthesized via Pulsed Laser Deposition (PLD) under an open-air atmosphere, with a primary focus on the first-time assessment of their performance in HER and OER. Meticulous control of the PLD process enables precise deposition of NiCoCuFeMoMn high entropy alloy films, ensuring a well-defined and homogeneous structure characterized through SEM, TEM, XPS, and XRD analyses. Leveraging the unique composition of high entropy alloys and their inherent diversity of elemental combinations, we strategically enhance catalytic performance. Preliminary results reveal HER and OER potentials of 285 mV and 192 mV, respectively. Tafel slopes obtained are promising when compared with Pt/C and RuO2. In this presentation, I will provide an overview of the design strategies and controlled synthesis of NiCoCuFeMoMn HEAs, emphasizing their electrocatalytic activities and potential in water splitting.

18_2414 Substrate Temperature Effect on the Optical Properties of CuSbS2 Thin Films Deposited at Oblique Incidence.

Mouna IDOUDI

Abstract

Substrate Temperature Effect on the Optical Properties of CuSbS2 Thin Films Deposited at Oblique Incidence.

Mouna IDOUDI1,*, Ferid Chaffar AKKARI1, B. Gallas2,and Mounir KANZARI1,3

1 Laboratory of Photovoltaics and Semiconductor Materials, National School of Engineers of Tunis, Tunis El Manar University, Le Belvédère, 1002 Tunis, Tunisia.

2 Paris-CNRS-University Pierre and Marie Curie, 140 rue de Lourmel, 75015 Paris, France.

3 Preparatory School for Engineering Studies of Tunis, University of Tunis, Montfleury, 1089 Tunis, Tunisia.

Haut du formulaire

Abstract

The goal of this research is to fabricate and characterize CuSbS2 thin films that are produced by vacuum thermal evaporation onto glass substrates heated at various temperatures (100, 150, 200, and 250 °C) as well as unheated substrates with varying incidence angles (00-85°). We have shown that the diffractogram of CuSbS2 powder only contains the orthorhombic CuSbS2 phase, which has a main orientation along the (111) plane. The reflection and transmission spectra show interference fringes, whereas the latter has absorption edges that rise with substrate temperature. The thicknesses of our thin films decrease as the substrate temperature rises. A high absorption coefficient of more than 105 cm-1 was reported. The permitted direct transitions decrease with substrate temperature, ranging from 1.17 to 2 eV.

Keyword: Substrate temperature, CuSbS2, Thin film, GLAD, Incident angle.

19_2450 Electrocatalytic activity of FePS3 and NiPS3 for the hydrogen evolution reaction (HER) in basic electrolytes.

Fabrice LEARDINI

Abstract

Water electrolysis has recently been proposed as a potential approach to green hydrogen production by using large-scale renewable energy plants. The technical challenge to developing this technology at a large scale and low cost is to get efficient electrodes based on earth-abundant elements and scalable production technologies. To this aim, the synthesis and characterisation of Fe and Ni phosphosulfides as electrode material for room-temperature electrolysers will be shown in this work.

Fe and Ni phosphosulfides, FePS3 and NiPS3, respectively, belong to the Metal phosphorous chalcogenide family with general formula MPXy where M is a metal (Fe, Co, Ni, Mn…), X is a chalcogen (S or Se), and Y could be usually 3 or 4. They are layered materials in which weak van der Waals forces hold the layers together and, therefore, they can easily be exfoliated in sheets. In their structure, within each layer, the phosphorus and metal atoms are in between the chalcogen ones.

Fe and Ni phosphosulfides (FePS3 and NiPS3) have been synthesised by CVT (Chemical Vapour Transport) from their precursors, sulfur and P2S5 powders, and the corresponding metal, Fe or Ni, respectively. The chemical reaction occurred in a previously evacuated closed ampoule under an inert Ar atmosphere. A two-zone furnace allowed the establishment of the temperature at 750ºC in the precursor zone and 70ºC lower in the extreme in which the phosphosulfides were synthesised for 100 hours.

FePS3 and NiPS3 powders obtained have been characterised by SEM-EDX (Scanning electron microscopy - Energy dispersive X-ray analyser), XRD (X-ray diffraction) and Raman Spectroscopy to identify their morphology, chemical composition, and crystalline phases. Afterwards, powders were exfoliated and deposited on screen-printed electrodes from Metrohm (Dropsenes150), and their electrochemical properties were investigated in an aqueous solution of 1.0M KOH. Cyclic Voltammetries are typically used to determine the overpotentials for the OER (Oxygen evolution reaction) and HER (Hydrogen evolution reaction). In this work, the overpotential for the HER at a cathodic current of 2 mA was measured with each phosphosulfide and compared to the value obtained with a Platinum foil electrode. The following values of the overpotentials were obtained: 0.4V, 0.65V and 0.7V. As a result of these measurements, besides the cathodic currents at a given bias potential, the electrocatalytic activity of the phosphosulfides has been demonstrated, making NiPS3 the best electrocatalyst, even better than Pt. Results from Tafel slopes confirm this trend as well.

The analysis and detailed discussion of all results will be exposed in the presentation.

20_259 Fe2O3 Photocathodes for Stable and Efficient Photorechargeable Li-Ion Batteries

Shubham CHAMOLA

Abstract

Photorechargeable batteries (PRBs) present a paradigm shift in electrochemical energy storage devices by integrating simultaneous solar energy harvesting and electrochemical energy storage within a single device [1-2]. The emerging technology eliminates the need for separate solar cells and energy storage devices, offering reduced ohmic losses, cost-effectiveness, and improved portability [3]. PRBs hold immense potential for powering Internet of Things (IoT) devices, remote sensing applications, and off-grid energy solutions. However, current PRBs often suffer from limitations such as instability, low output voltages, complex synthesis routes, and most of them employ intercalation mechanisms to store Li-ions. To improve the performance of PRBs, meticulous selection of active materials with tailored band gaps, well-aligned transport layers, and in-depth investigations of charge carrier dynamics are crucial.

In order to overcome such limitations, we investigated α-Fe₂O₃ as an active material for a two-electrode PRB due to their suitable bandgaps and high theoretical capacities resulting from the conversion and alloying mechanism. Synthesized pristine and composite materials were characterized using advanced optical, optoelectronic, and electrochemical characterization techniques to achieve the optimum performance. Multi-walled carbon nanotubes (MWCNTs) and PCBM are employed to facilitate efficient charge carrier transport in the Fe₂O₃-based PRB. This innovative approach yielded a remarkable 92.96% enhancement in the specific capacity under illumination (12 mW cm^-2) at a current rate of 2000 mA g^-1 and 94% enhancement in the CV swept area at 5 mV s^-1 scan rate. Fe₂O₃-based Li-PRB achieved a remarkable photoconversion and storage efficiency of 1.988%, representing a significant advancement in this field [4]. In-situ measurements revealed that illumination enhances the kinetics of the PRB, leading to decreased resistance, prolonged discharge time, and improves overall performance. The fabricated prototype Li-PRBs powered a commercial 3V LED and digital hygrometer for 7 days. These findings signify substantial progress in the field of PRBs, offering a new outlook for the investigation of novel materials and designs, facilitating future breakthroughs in this field of study.

References

[1] S. Ahmad, C. George, D. J. Beesley, J. J. Baumberg, M. De Volder, Photo-Rechargeable Organo-Halide Perovskite Batteries. Nano Lett 18, 1856–1862 (2018).

[2] B. D. Boruah, A. Mathieson, B. Wen, S. Feldmann, W. M. Dose, M. De Volder, Photo-rechargeable zinc-ion batteries. Energy Environ Sci 13, 2414–2421 (2020).

[3] A. D. Salunke, S. Chamola, A. Mathieson, B. D. Boruah, M. de Volder, S. Ahmad, Photo-Rechargeable Li-Ion Batteries: Device Configurations, Mechanisms, and Materials. ACS Appl Energy Mater 5, 7891–7912 (2022).

[4] S. Chamola and S. Ahmad, High Performance Photorechargeable Li‐Ion Batteries Based on Nanoporous Fe₂O₃ Photocathodes. Adv Sustain Syst 7 (2023).

21_275 Photonic Curing of Electron Transport Layers for Antimony Selenide Solar Cells

Udari WIJESINGHE

Abstract

High-throughput fabrication of metal oxide thin films as electron transport layers is always a bottleneck for current solar cell manufacturing due to the requirement of a high temperature sintering step. Current thermal annealing processes take tens of minutes and are impractical in high web speed manufacturing for future photovoltaics. This study focuses on a low thermal budget rapid curing process, with a well-controlled train of short light pulses, to produce high-quality crystalline TiO₂ and SnO₂ thin films used as electron transport layers in Sb₂Se₃ thin film solar cells. Detailed investigations of curing and sintering conditions were performed to understand the impact of photonic curing conditions on the electrical performance of the electron transport layers. The strong dependency of the pulse energy and pulse length on the optoelectronic performance of the devices is investigated. A correlation between the chemical properties of the as-cured TiO₂ and SnO₂ and the interface quality and sequence on device properties is established. Furthermore, it shows that an intense pulse curing process removes the organic and chloride residuals in TiO₂ and SnO₂, respectively. These improved interface qualities facilitate lower interfacial recombination compared to thermally annealed electron transport layers. The photonic-cured TiO₂ and SnO₂ films exhibit 42% and 50% enhancement of power conversion efficiency, respectively, comparable to the device performance of thermally annealed TiO₂ and SnO₂ films. The significant reduction in processing time and enabled high-speed fabrication of high-quality metal oxide showed that photonic curing is compatible with roll-to-roll manufacturing in chalcogenide photovoltaics.

22_2766 Electrodeposition of n-Type Cu2O Thin Films: Towards Phase-Pure Layers and Composite Structures

Balasubramaniam KAVAIPATTI

Abstract

Cuprous oxide (Cu₂O) thin films, antithetically exhibiting n-type conductivity, were electrodeposited on Fluorine-doped Tin Oxide (FTO) coated glass substrates. This study focuses on the electrodeposition of n-type Cu₂O in acidic conditions, elucidating the presence of copper impurities in the film. A method is introduced to delay Cu formation, as evidenced by voltammetric data indicating multiple reduction reactions, including Cu₂O-to-Cu conversion aligned with the deposition potential. Chronopotentiometry studies attribute Cu formation to local pH changes from the release of H⁺ ions. Continuous stirring effectively delays Cu formation, allowing for thick Cu₂O layer deposition. Our findings guide experimental protocols for phase-pure n-type Cu₂O or Cu₂O-Cu composite films, facilitating fundamental studies and diverse applications. Phase-pure n-type Cu₂O enables investigations into defect chemistry governing n-type behavior without metallic Cu complications. It serves as an electron transport layer in photo-conversion devices and allows for homojunction devices with p-type Cu₂O. Additionally, Cu₂O-Cu composite films offer insights into applications involving light-driven CO₂ reduction.

23_306 Fabrication of Conductive TiO2 Thin Films by Mist Chemical Vapor Deposition and Its Application for Surface Coating of Polymer Electrolyte Membrane Fuel Cell Separators

Tomohito SUDARE

Abstract

Anatase Ti_1−xNb_xO₂ (TNO) thin films have gained much attention in catalysts, sensors, and electronic devices. TNO epitaxial thin films exhibit low electrical resistivity (2.3×10⁻⁴ Ωcm at 300 K)^[1] and high optical transparency in the visible light range^[1], comparable to Sn-doped In₂O₃ transparent conductive films. Even in polycrystalline films deposited on glass, TNO achieves a resistivity of 7.6×10⁻⁴ Ωcm^[1], showing excellent chemical stability. The high conductivity and chemical stability of TNO are suitable for surface coating materials in stainless steel separators for polymer electrolyte membrane fuel cells (PEMFC). Therefore, in this study, we investigate TNO for the coating of separators. First, polycrystalline TNO thin films are fabricated on glass substrates using mist chemical vapor deposition. Next, the growth conditions are optimized to achieve high conductivity. Finally, we demonstrate the contact resistance of 1.4 mΩ cm² for the carbon-based gas diffusion layer and the TNO-coated stainless-steel separator. These results open up anatase TiO₂ as a promising coating material for PEMFC separators with high power density.

^[1] T. Hitosugi, N Yamada et al., Phys. Status Solidi A 207, 7, 1529–1537 (2010)

24_363 Metal porphyrin-based functionalized electrocatalysts for the artificial fixation of nitrogen to Ammonia

Giorgia SALERNO

Abstract

Ammonia is an essential raw ingredient for fertilizers, a carbon-free hydrogen carrier, and an alternative fuel.

The over one-century old Haber-Bosch process is still used today for the synthesis of ammonia, from nitrogen and hydrogen, but it is strongly energy demanding (ca. 2% of global energy demand) and generates massive greenhouse gases (ca. 2% of global emissions). It is therefore mandatory to develop clean access to ammonia in order to match the net zero decarbonation targets for 2050. Recently, research has focussed attention on alternative routes and, among those proposed, the electrocatalytic reduction from nitrogen to ammonia is the most accredited. The strongly inert N2 molecule can be activated thought an electrocatalytic approach under mild conditions. However, so far, the use of organic-based electrocatalysts is very rare in the literature and systematic studies are almost absent.

Following our previous general approach for organic design for solar generation of green hydrogen,1 in this communication we present our recent preliminary work on the investigation of a series of metallo-porphyrins, which have been properly functionalized in order to enhance nitrogen fixation performance. In particular, we have developed two series of hydrophilic and hydrophobic derivatives, able to show different interactions at the interface with the aqueous electrolytic environment of the electrochemical cell, thus affecting the device interface phenomena and, eventually, the final response.

References:

[1] Boldrini, C. L.; Quivelli, A.F.; Manfredi, N.; Capriati, V.; Abbotto, A., Molecules 2022, 27, 709; Boldrini, C. L.; Manfredi, N.; Perna, F. M.; Capriati, V.; Abbotto, A. ChemElectroChem 2020, 7, 1707; Boldrini, C. L.; Manfredi, N.; Perna, F. M.; Capriati, V.; Abbotto, A. Chem. Eur. J. 2018, 24, 17656; Manfredi, N.; Monai, M.; Montini, T.; Peri, F.; De Angelis, F.; Fornasiero, P.; Abbotto, A. ACS Energy Letters 2018, 3, 85.

25_40 Advances in Graphene-based Multifunctional Hybrid Electrodes for Alternative Energy and the Sustainable Environment

Sanju GUPTA

Abstract

Intense research in alternative sources of renewable and clean energies stimulated by increasing global demand of electric energy. Electrochemical energy conversion/storage systems (EECS) represent the most efficient and environmentally benign technologies for sustainable advancements. Therefore, there is an urgent need for engineered electrochemical electrode materials to enable high-performance next-generation energy storage/conversion devices approaching industrially relevant specific energy and power densities and delivering electrical power rapidly and efficiently. Among carbon-based nanomaterials, graphene and its variants continue to promote extensive research and development since their inception due to exceptionally rich tunable physicochemical properties. In this talk, I will present potent strategies geared towards the rational synthesis of novel multifunctional graphene-based hybrid materials with engineered structural and electrochemical storage properties. We aim at creating an enhanced function from both atomic-scale interfaces and nanoscale morphology, with a strong emphasis on exploring micro(nano) structure-property-activity relationships in these functional materials based on a variety of complementary analytical tools. Specifically, we invoke chemical hybridization and molecular bridging of 2D graphene to 1D carbon nanotubes via electrostatic layer-by-layer assembly and transition metal oxides by electrodeposition as well as interconnected graphene nanosheet-carbon nanotube aerogel monoliths to develop new two- and three-dimensional systems with application potential in electrochemical energy storage, conversion as well as environmental and biochemical sensing. Also, fundamental insights into the dynamic physicochemical processes occurring at the electrode-electrolyte interfaces will be presented gained by using electrochemical microscopy. The experimental findings complement density functional theory that signifies available density of states in the vicinity of Fermi level thus contributing to higher electroactivity.

26_419 Investigating the Degradation Mechanisms and Enhancing Stability of Tin-Lead Perovskite Materials for Advanced Thin Films in Energy and Sustainable Applications

Asayil ALSULAMI

Abstract

The pursuit of highly efficient and cost-effective photovoltaic materials has led to the emergence of organic-inorganic metal halide perovskites. However, their inherent instability poses challenges to their practical application, limiting their lifespan and scalability. Among these perovskites, mixed tin-lead compositions have garnered significant attention due to their unique optoelectronic features and small bandgaps, offering great promise for various applications. Nonetheless, their low ambient stability presents a significant hurdle that requires a thorough investigation into their degradation mechanisms. This study aims to understand the degradation mechanisms of tin-lead perovskites, with a specific focus on the role of halide chemistry and the impact of iodine on their stability. Our findings reveal a cyclic degradation process, where iodine and SnI4 act as key degradation products, compromising the stability of the perovskite material. Furthermore, the presence of triiodide, derived from native iodine oxidants, exhibits a strong correlation with degradation. We observe that the selection of A-site cations significantly influences the oxidation stability of Sn-Pb perovskites. Cesium-rich phases and solar cells demonstrate superior resistance to oxidative stress compared to their methylammonium-based counterparts, primarily due to the limited formation of triiodide. Leveraging this insight, we successfully stabilize sensitive methylammonium-based Sn-Pb perovskite films and devices against oxidation by employing CsI coatings. This practical approach provides essential guidelines for enhancing the stability of perovskite materials and devices. The significance of this study lies in its contribution to the design and engineering of perovskite materials and devices for advanced thin films in energy and sustainable applications. Understanding the role of iodine in perovskite deterioration is crucial for improving their stability and durability, thereby paving the way for their commercialization. By elucidating the degradation mechanisms of tin-lead perovskites, we can develop effective strategies to mitigate their degradation, enhance their stability and lifespan, and unlock their full potential for various photovoltaic applications. This work aligns with the "Advanced Thin Films for Energy and Sustainable Applications" program, as it addresses the challenges associated with the stability of perovskite solar cells. Stable and efficient perovskite solar cells play a vital role in renewable energy production, contributing to a more sustainable and environmentally conscious future. By overcoming the degradation issues and enhancing the stability of tin-lead perovskite materials, this research contributes to the development of advanced thin films for energy and sustainable applications.

27_496 AgxSiO0.7N thin film anode with high rate performance and transparency for transparent thin film battery

Ji-Won CHOI

Abstract

The demand towards next-generation transparent energy sources has arisen in response to the recent acceleration of the development of smart paper, smart windows, medical diagnostic smart lenses, and transparent displays. It is difficult to produce transparent batteries since the electrolyte is the only transparent material used in lithium-ion battery construction. Transparent cathode electrodes, such as Mn-doped LiFePO₄ with 82% transparency, have been explored. It is still necessary to research the transparent anode electrode for an transparent all-solid-state thin-film battery. With its great transparency(88%) and high capacity(1018 mAh g^-1), the SiN_x anode is a promising anode material; nevertheless, its low electrical conductivity hinders its electrochemical performance.

Ag-SiN_x composite thin film is designed in this work to increase the electrical conductivity of SiN_x while preserving its excellent transparency. The best compositions for high electrochemical performance and optical qualities are investigated using the continuous composition spread method, a high throughput method that enables the investigation of several compositions in a single growing procedure. Thus, a thin film battery with Ag nanoparticles added to the anode has a discharge capacity of 242.8 μAh/cm²·μm at 0.2 C, more than six times higher than the SiN_x. Its ability to operate at a high C rate of up to 10 C is another benefit. This is available since the charge transfer resistance of the thin film battery has decreased as a result of the uniform deposition of Ag nanoparticles, which has increased the electrical conductivity of the anode material. The Nyquist plot was performed as a confirmation. Conversely, the optical spectra revealed greater transparency as the Ag concentration decreased. Here, we suggest a number of Ag_xSiO_0.7N anode concentrations for the development of high-rate and high-capacity thin-film batteries in order to best control the trade-off between transmittance and capacity.

28_511 Control of microstructure and composition of reactively sputtered vanadium nitride thin films and application to micro-supercapacitors

Jérémy BARBÉ

Abstract

In this study, we prepared vanadium nitride (VN) thin films by reactive DC magnetron sputtering of a vanadium target using nitrogen as reactive gas. The structural, morphological, and compositional evolution of these films is described based on hysteresis diagrams plotting the sputtering power vs. nitrogen flowrate. These diagrams, measured across various cathode voltages and discharge pressures, unveil three distinct deposition regimes: metallic, intermediate, and contaminated. The microstructure of the films was found to be closely linked to the deposition regime, ranging from dense and amorphous in the metallic regime to porous and crystalline in the contaminated regime, while the composition varies from vanadium-rich to near-stoichiometric VN.

Sputtered VN thin films used as electrodes for micro-supercapacitors were investigated by cyclic voltammetry. Results highlight that the intermediate deposition regime, characterized by high crystallinity and porosity, yields the highest capacitance values, above 900 F.cm^-3. Such high volumetric capacitance is attributed to the highly porous structure and large specific surface area. Besides, in these deposition conditions, films are composed of crystalline VN with a significant amount of amorphous VO_x in surface, which allow these thin film electrodes to behave both as current collector and pseudo-capacitive electrodes.

In the second part of the presentation, the effect of substrate polarisation will be discussed. A large range of techniques, such as electron microscopy, photoelectron spectroscopy, X-ray diffraction and cyclic voltammetry are used to described the effect of substrate polarisation on microstructure and electrochemical performance of sputtered VN thin films. These characterizations indicate that increasing substrate polarisation induces atomic peening effect, which implies a densification and amorphisation of the VN thin films with clear changes in electric double layer capacitance.

This work gives detailed insights on VN thin film microstructure and composition in reactive sputtering, based on hysteresis curves and deposition parameters. It emphasizes how we could target specific microstructure, composition and eventually achieve functional properties. In particular, these findings have important implications for the design and optimization of microstructured electrodes for energy storage applications.

29_559 On-Water Surface Synthesis of Two-Dimensional Polymer Thin Films Toward Sustainable Energy Devices

Zhiyong WANG

Abstract

Synthetic two-dimensional polymers (2DPs) are an emerging class of structurally defined crystalline materials that comprise covalent networks with topologically planar repeat units. Yet, synthesizing 2DP single crystals via irreversible reactions remains challenging. Herein, utilizing the surfactant-monolayer-assisted interfacial synthesis (SMAIS) method, few-layer, large-area, skeleton-charged 2DP (C2DP) single crystals were successfully synthesized through irreversible Katritzky reaction, under pH control. The resultant periodically ordered 2DPs comprise aromatic pyridinium cations and counter BF4- anions. The representative C2DP-Por crystals display a tunable thickness of 2-30 nm and a lateral size of up to 120 μm2. Using imaging and diffraction methods, a highly uniform square-patterned structure with the in-plane lattice of a = b = 30.5 Å was resolved with near-atomic precision. Significantly, the C2DP-Por crystals with cationic polymer skeleton and columnar-like pore arrays offer a high chloride ion selectivity with a coefficient up to 0.9, thus ensuring the integration as the anion-selective membrane for the osmotic energy generation. In addition, as the graphite electrode skin, we demonstrate that C2DP enables to prevent the cation/solvent co-intercalation into the graphite electrode and suppress the consequent structure collapse, leading to enhanced durability of Li battery. Furthermore, we synthesized a fully crystalline viologen-immobilized 2D polymer (V2DP) thin film, which can serve as the color-switching layer in electrochromic devices and exhibits a high coloration efficiency (989 cm2 C-1), and low energy consumption.

Ref.

1. Z. Wang, et al., Nat. Synth. 2022, 1, 69–76

2. Z. Wang, et al., Adv. Mater. 2022, 34, 2106073.

3. D. Sabaghi#, Z. Wang#, et al., Nat. Commun. 2023, 14, 760

30_595 Improving the investigation of defect properties through temperature dependent modulated photoluminescence

Hiba HADDARA

Abstract

The need for non-contact techniques to improve the characterization of electronic defects in materials and components is critical for the assessment of new photovoltaic technologies. Advanced characterization tools are required to study such defects and quantify their density within the material. The Modulated PhotoLuminescence(MPL) technique that can operate in a wide frequency range[10Hz-200MHz] has proven to be a promising candidate. Showing its utility in characterizing defects in semiconductor materials. A previous study by Berenguier et al.[1] revealed singularities in the phase dependence of MPL as a function of frequency, called V-shapes, where the phase is not monotonously varying with frequency, but exhibits a local extremum. On this basis, in our study, we carried out a theoretical analysis by solving the continuity equations, as described in a previous article [2]. This suggests that the existence of a V-shape may be related to the presence of minority carrier traps within the material, but this relationship is not always clear and requires additional explanation. In studying the variation of the V-shape with temperature, we extended previous theoretical work by identifying rules for the appearance and disappearance of the V-shape in the MPL bode diagrams of probed doping material in the presence of Shockley-Read-Hall (SRH) recombination centers. From modelling of such materials in low injection ,by varying the energy level position of the defect and the effective cross-section of minority and majority carriers, we show that the V-shape curves appear when the defect is a minority carrier trap. In this case, we propose a method to extract the information of the defect properties. However, for other conditions 9like higher injection and intrinsic material),V-shapes can appear even if the defect is a majority carrier trap. These results will be illustrated using modelling and experimental works.

[1] B. Bérenguier et al., « Defects characterization in thin films photovoltaics materials by correlated high-frequency modulated and time resolved photoluminescence: An application to Cu(In,Ga)Se2 », Thin Solid Films, vol. 669, p. 520‑524, janv. 2019, doi: 10.1016/j.tsf.2018.11.030.

[2] N. Moron, B. Bérenguier, J. Alvarez, et J.-P. Kleider, « Analytical model of the modulated photoluminescence in semiconductor materials », J. Phys. D: Appl. Phys., vol. 55, no 10, p. 105103, mars 2022, doi: 10.1088/1361-6463/ac39c4.

Keywords: MPL, photoluminescence, modeling, semiconductors, characterization, defect properties

31_638 Pseudocapacitive Storage in Molybdenum Oxynitride Nanostructures Reactively Sputtered on Stainless-Steel Mesh towards All-Solid-State Flexible Supercapacitors

Bhanu RANJAN

Abstract

Exploiting pseudocapacitance in rationally engineered nanomaterials offers greater energy storage capacities at faster rates. The present research reports a high-performance Molybdenum Oxynitride (MoON) nanostructured material deposited directly over stainless-steel mesh (SSM) via reactive magnetron sputtering technique for flexible symmetric supercapacitor (FSSC) application. The MoON/SSM flexible electrode manifests remarkable Na⁺-ion pseudocapacitive kinetics, delivering exceptional ~881.83 F.g^-1 capacitance, thanks to the synergistically coupled interfaces and junctions between nanostructures of Mo₂N, MoO₂, and MoO₃ co-existing phases, resulting in enhanced specific surface area, increased electroactive sites, improved ionic and electronic conductivity. Employing 3D Bode plots, b-value, and Dunn’s analysis, a comprehensive insight into the charge-storage mechanism has been presented, revealing the superiority of surface-controlled capacitive and pseudocapacitive kinetics. Utilizing PVA-Na₂SO₄ gel electrolyte, the assembled all-solid-state FSSC (MoON/SSM||MoON/SSM) exhibits impressive cell capacitance of 30.7 mF.cm^-2 (438.59 F.g^-1) at 0.125 mA.cm^-2. Moreover, the FSSC device outputs superior energy density of 4.26 μWh.cm^-2 (60.92 Wh.kg^-1) and high power density of 2.5 mW.cm^-2 (35.71 kW.kg^-1). The device manifests remarkable flexibility and excellent electrochemical cyclability of ~91.94% over 10,000 continuous charge-discharge cycles. These intriguing pseudocapacitive performances combined with lightweight, cost-effective, industry-feasible, and environmentally sustainable attributes make the present MoON-based FSSC a potential candidate for energy-storage applications in flexible electronics.

Reference: Ranjan, Bhanu, and Davinder Kaur. "Pseudocapacitive Storage in Molybdenum Oxynitride Nanostructures Reactively Sputtered on Stainless‐Steel Mesh Towards an All‐Solid‐State Flexible Supercapacitor." Small (2023): 2307723.

32_644 Higher power density NVPF-MWCNT@Ni//CNF@Ni Configuration via hydrothermal route for flexible Na-ion Capattery

Gagan Kumar SHARMA

Abstract

Considering the electrochemical performance and structural stability of nanohybrids, Na3V2(PO4)2F3 (NVPF), multi-walled carbon nanotubes (MWCNTs), and carbon nanofibers (CNF) are emerging materials to promote the flexible sodium-ion capattery (FNIC) as a hybrid energy storage system. Direct incorporation of hydrothermally synthesized NVPF into MWCNT nanoarrays has been achieved on foldable nickel (Ni) foil via the slurry casting approach. We report an efficient utilization of the synergistic effect of ball-milled nanocomposites to design the FNIC cell from NVPF-MWCNT@Ni (battery-type) and CNF@Ni (capacitor-type) electrodes. The as-obtained FNIC device exhibits a remarkable specific capacitance of 136.17 F g-1 with a corresponding specific capacity of 95.32 C g-1 at a potential scan rate of 1 mV s-1. The charge storage ability is mainly viewed as the synergism stimulated across unique interfacial surface construction provided by NVPF and carbon-derived conductive host materials. Subsequently, the constructed asymmetric NVPF-MWCNT@Ni//CNF@Ni architecture exhibits a maximum working voltage of 0.70 V and a noticeable power density of 15.84 kW kg-1 at 2.50 Wh kg-1. The abundance of conducting pathways in hybrid nanoarrays facilitates intercalation/deintercalation of Na+/SO4-2 ions into the electroactive sites, further endorsing pseudocapacitance. Besides, the flexibility test outcomes illustrate practically unperturbed electrochemical properties at a 160º bending angle, indicating excellent mechanical robustness. The FNIC cell retains 90% of initial capacitance over 2,000 charge-discharge cycles, revealing a longer service lifespan attributed to advanced rate capability. The current study offers new avenues to develop energy storage systems for next-generation portable and wearable electronics at large-scale applications.

33_80 Energy transfer examination of Er3+/Nd3+ to produce a high-performance light conversion layer for enhancing the solar cells' efficiency

Najla ALMULHEM

Abstract

Since their invention as a technology for generating electrical energy, solar cells have suffered from poor efficiency resulting from a loss of light energy that is not appropriate for the solar cell bandgap. Hence, the technology of light conversion layers emerged to adjust the light energy falling on the solar cell to suit it. Trivalent lanthanide (Ln3+) ions are considered optimal in the fields of light conversion, whether up or down conversion. Compared to down-conversion technology, up-conversion, which occurs through converting low-energy photons to high-energy ones, has become common in enhancing the output efficiency of solar cells due to their high ability to convert infrared rays into visible light. It is usually difficult to use the effective ions assigned to achieve a goal as they are, but rather require a host material suitable for the purpose to be achieved. In photonic applications, the use of phosphate glass has spread as it has a low phonon energy, which increases the efficiency of its quantum yield of light emission. Oxide modifiers such as PbO, Na2O, ZnO, etc. enrich the optical, thermal, and chemical properties of the phosphate glass network, but unfortunately, they negatively affect the phonon energy of the glass by increasing it. Therefore, halide metals such as fluorides, chlorides, and bromides are usually added to overcome the dilemma of increasing phonon energy.

Hence, the current study aims to develop and produce a spectral conversion layer based on the energy transfer between Er3+ and Nd3+ ions. A P2O5-ZnO-Pb3O4-NaF-MgF2-Er2O3 glass network was proposed as a host material and reinforced with various concentrations of Nd2O3 ions to study the light conversion resulting from the energy transfer. The main objective of the study, which is spectral upconversion, was examined by pumping the studied glasses at appropriate wavelengths and studying the resulting emission.

References

1. M. Matakgane, T. P. Mokoena, and M. R. Mhlongo, Recent trends of oxides heterostructures based upconversion phosphors for improving power efficiencies of solar cells: A review, Inorganic Chemistry Communications 156 (2023)111202.

2. R. G. Capelo, T. I. Rubio, G. L. Calderón, D. A. de Moraes, E. M. Junior, M. Nalin, and D. Manzani, Effect of silver nanoparticles on the visible upconversion emission of Er3+/Yb3+ co-doped SbPO4-GeO2 glasses, Optical Materials 135 (2023) 113234.

3. R.F. Muniz, V.S. Zanuto, M.S. Gibin, J.V. Gunha, A. Novatski, J.H. Rohling, A.N. Medina, and M. L. Baesso, Down- and up-conversion processes in Nd3+/Yb3+ co-doped sodium calcium silicate glasses with concomitant Yb2+ assessment, Journal of Rare Earths 41(3) (2023) 342-348.

4. V. Chandrappa, C. Basavapoornima, C. R. Kesavulu, A.M. Babu, S. R. Depuru, and C. K. Jayasankar, Spectral studies of Dy3+: zincphosphate glasses for white light source emission applications: a comparative study, Journal of Non-Crystalline Solids 583 (2022) 121466.

34_84 Optimizing Catalyst Design for Selective Seawater Oxygen Evolution Reaction

Seyedmahdi MOUSAVI

Abstract

The oxygen evolution reaction (OER) found as a core reaction for the development of water-splitting systems, essential for clean hydrogen generation. However, the current state-of-the-art technology is based on using noble metals and freshwater for electrocatalysis, presenting two critical challenges in terms of sustainability and accessibility. Noble metals are scarce, and freshwater resources are limited, posing major obstacles to the widespread adoption of this technology. While, Seawater recently has been explored as a promising candidate for water-splitting , it introduces new challenges, particularly in the need for corrosion-resistant catalysts. This requirement arises from the presence of dissolved ions, such as chloride ions (Cl-), which can interfere with the OER at the anode.

Our study focuses on developing a novel two-dimensional (2D) heterostructure catalyst using non-noble metals. This noble catalyst shows high selectivity and specificity when operating in seawater conditions. Remarkably, the catalyst was able to generate nearly 2A with operational stability sustained over 800 h. The success of our catalyst can be attributed to synergistic effect created by 2D-heterostructured and their electronic interactions.

35_86 Electrochemical behavior of nickel oxide nanoelectrocatalyst in diverse electrolytic environments and its application as an effective electrode for supercapacitors

Manisha CHAUHAN

Abstract

In this study, we explore the electrochemical characteristics of nickel oxide (NiO) thin films, highlighting their exceptional activity in the oxygen reduction reaction (ORR) across diverse electrolyte media. Employing a sol-gel method for nanostructured NiO production, we utilized spin coating with varying deposition cycles to fabricate thin films. Structural and morphological analyses through XRD and SEM confirmed the film's integrity, while AFM verified optimal thickness deposition on the substrate. Cyclic voltammetry was employed to assess the electrochemical performance, revealing that a specific number of NiO film depositions outperformed others. The superior electrocatalytic activity is attributed to charge transfer dynamics in the oxygen evolution reaction (OER) mechanism. We optimized the operating pH for these electrodes and demonstrated their suitability for supercapacitors, showcasing a higher specific energy of 15.5 Wh kg^-1 at a specific power of 151 W kg^-1. This underscores the potential of NiO thin films as effective electrode materials for advanced energy storage applications.

36_884 Carbonate electrolyte enriched with fluorine-based co-solvent for dendrite-free lithium metal batteries

Chaeyeon HA

Abstract

Lithium metal batteries are considered ideal anode materials for next-generation batteries due to their high theoretical specific capacity (3,860 mAh g-1) and low electrochemical potential (−3.040 V vs. standard hydrogen electrode), which are essential for high energy density. Nevertheless, a significant obstacle hindering the commercial viability of lithium metal anodes is the occurrence of detrimental dendritic growth on the metal's surface through repetitive cycling. Managing the morphology of lithium plating poses a challenge, particularly in electrolytes based on carbonates, affecting the stable operation of lithium metal batteries.

In this study, we present a novel approach to achieving lithium metal batteries free from dendritic growth. This method involves the use of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as a fluorine-based co-solvent in combination with carbonate electrolytes. The utilization of TTE resulted in a decrease in electrolyte viscosity, enhanced ionic conductivity, and a reduction in overpotential during the lithium plating/stripping process. Moreover, in contrast to electrolytes based solely on carbonates, we attained a more consistent lithium deposition. This led to the development of a dense and stable solid electrolyte interface layer, as verified through field emission scanning electron microscopy and in-situ electrochemical atomic force microscopy. We attained outstanding cycle life performance, maintaining capacity retention of 78% after 300 cycles, employing a thin lithium metal film of 40 µm. Consequently, the stability and efficiency of lithium metal batteries with a high energy density (380 Wh kg-1) utilizing a carbonate electrolyte were significantly enhanced. This research has the potential to bring us a step closer to the commercialization of lithium metal batteries.

37_907 Dendrite suppression by anode HCl treatment in zinc-ion batteries

Huanlin LYU

Abstract

Aqueous zinc-ion batteries (ZIBs) are the most perspective energy storage system because of their low cost, safety, abundant zinc reserves, and environmental friendliness. However, Zn dendrite growth remains the main reason that limits the life span of ZIBs. Recently researchers have proposed various methods to alleviate or inhibit dendrite growth, such as electrolyte additives, modified anodes, alternative cathode materials, etc. However, relatively little research has been done on the zinc structure itself. Herein, a quick and simple hydrochloric acid (HCl) pretreatment of zinc foil before electrochemical operation resulted in a significant reduction of zinc dendrites and an extension of the cycle life of the cell compared to raw Zn foil. By combining ex-situ SEM and ex-situ AFM, it was proved that the initial structural defects of zinc foil determine the subsequent plating/stripping morphology. Appropriate defects on zinc foil can prolong battery cycling life. It is also applicable in flexible batteries with hydrogel as electrolyte. This study provides a simple method for wider commercial application of ZIBs in the future and provides new ideas for the study of zinc dendrite growth.