Fédération de Recherche PhotoVoltaïque

Abstract Mixed halide perovskites have attracted a strong interest in the photovoltaic community as a result of their high power conversion efficiency and the solid opportunity to realize low-cost and industry-scalable technology. Light soaking represents one of the most promising approaches to reduce non-radiative recombination processes and thus to optimize device performances. Here, we investigate the effects of 1 sun illumination on state-of-the-art triple cation halide perovskite thin films Cs0.05(MA0.14, FA0.86)0.95 Pb (I0.84, Br0.16)3 by a combined optical and chemical characterization. Competitive passivation and degradation effects on perovskite transport properties have been analyzed by spectrally and time-resolved quantitative imaging luminescence analysis and by X-ray photoemission spectroscopy (XPS). We notice a clear improvement of the optoelectronic properties of the material, with a increase of the quasi fermi level splitting and a corresponding decrease of methylammonium MA+ for short (up to 1 h) light soaking time. However, after 5 h of light soaking, phase segregation and in-depth oxygen penetration lead to a decrease of the charge mobility.

Solar cells based on epitaxial silicon layers as the absorber attract increasing attention because of the potential cost reduction. In this work, we studied the influence of the deposition rate on the structural properties of epitaxial silicon layers produced by plasma-enhanced chemical vapor deposition (epi-PECVD) using silane as a precursor and hydrogen as a carrier gas. We found that the crystalline quality of epi-PECVD layers depends on their thickness and deposition rate. Moreover, increasing the deposition rate may lead to epitaxy breakdown. In that case, we observe the formation of embedded amorphous silicon cones in the epi-PECVD layer. To explain this phenomenon, we develop a model based on the coupling of hydrogen and built-in strain. By optimizing the deposition conditions to avoid epitaxy breakdown, including substrate temperatures and plasma potential, we have been able to synthesize epi-PECVD layers up to a deposition rate of 8.3 Å/s. In such case, we found that the incorporation of hydrogen in the hydrogenated crystalline silicon can reach 4 at. % at a substrate temperature of 350 °C.

Abstract The effect of copper substitution by alkali metals on the properties of chalcopyrite-type materials for tandem applications in photovoltaics is investigated at the first-principles level, using an exchange-correlation hybrid functional optimized to yield a description of the structural, electronic, and dynamic properties of these materials in good agreement with experiment. Since the target values of the band gap for tandem applications should be between 1.5 and 1.8 eV, one part of the results concerned the variation of calculated band gap values under the effect of substitution. A systematic study of the effects of Li, Na, K, Rb, and Cs on the structural, electronic, and thermodynamic properties of CuGaS2, CuGaSe2, CuInS2, and CuInSe2 has been performed. The evolution of the crystallographic cell with the concentration of alkali metals turned out to be of two types: (i) the substitution of Cu with Li and Na in CuInS2, irrespective of concentration, leaves the underlying chalcopyrite structure unchanged, affecting only the lattice parameters; (ii) the substitution of Cu with Na (with the exception of CuInS2), K, Rb, and Cs at sufficiently high concentration brings about a phase transition. In all cases, the band gap increases with the alkali concentrations, whereby only the indium-based chalcopyrites reach the above-mentioned target values for applications in tandem photovoltaic devices. The static stabilities of the substituted materials have been further discussed in terms of substitution energies and energies of formation, with the latter being evaluated to secondary phases plausible in the process of synthesis. The comparison with the experimental situation and the impact of the novel predictions are discussed.

Thermal treatment of the cell samples after dc sputtering of the Au electrodes enhanced the reproducibility of the perovskite cell efficiencies because the thermal annealing induced the strong adhesion between each layer of the cells.

Conjugation of low‐cost and high‐performance semiconductors is essential in solar‐driven photoelectrochemical (PEC) energy conversion. Sb2S3 is a wide‐bandgap (≈1.7 eV) semiconductor with the potential to deliver a maximum photocurrent density of 24.5 mA cm−2, making it highly attractive for PEC water splitting applications. However, bulk Sb2S3 exhibits intrinsic recombination issues and low electron–hole separation, posing a limit to photocurrent generation. This study clarifies the carrier dynamics by ultrafast spectroscopy measurements and proposes the design of a heterojunction between Sb2S3 and SnO2, with suitable band‐edge energy offset. The SnO2/Sb2S3 heterojunction enhances the charge separation efficiency, resulting in improvement of the photocurrent. The SnO2/Sb2S3 photoanode, fabricated entirely by vapor deposition processes, demonstrates photoelectrochemical water oxidation with a photocurrent density up to ≈3 mA cm−2 at 1.38 V versus RHE.

C-AFM and KPFM techniques have been applied to investigate advanced junctions that are currently involved in highly efficient silicon solar cells. Our first study focuses on silicon heterojunctions and notably hydrogenated amorphous silicon (a-Si:H)/crystalline silicon (c-Si) P/n or N/p heterostructures which band bending at the interface forms a 2D channel. This conductive channel was indeed evidenced for the first time by cross-sectional investigations by C-AFM confirming the analysis of macroscopic planar conductance measurements. A second example of nanoscale characterization concerns the passivating selective contacts consisting in a thin silicon oxide (SiOx) layer between the c-Si and a highly doped polysilicon (poly-Si) layer. The electrical carrier transport is here not limited by the oxide layer and it is assumed that tunnelling through the oxide and/or the presence of pinholes are the main competitive mechanisms. For this specific heterostructure KPFM reveals local surface potential drops of 15- 30 mV, which do not exist on samples without SiOx. These potential drops suggest the presence of pinholes that are formed during the poly-Si annealing process performed in the range of 700-900°C. Finally, in a third study, we concentrate on p-i-n radial junction (RJ) silicon nanowire (SiNW) devices that are investigated under illumination by KPFM, in the so-called surface photovoltage (SPV) technique. This work focuses on the possibility of extracting the open-circuit voltage (VOC) on single isolated SiNW RJ by local SPV measurements using different AFM tip shapes and illumination directions in order to minimize shadowing effects.

This chapter focuses on the parameter estimation of proton exchange membrane fuel cells (PEMFCs) in the context of transportation applications. With the increasing demand for clean and sustainable energy sources, PEMFCs have emerged as a promising technology due to their high efficiency, low operating temperature, and environmental friendliness. Accurate parameter estimation plays a crucial role in achieving reliable simulation and performance prediction of PEMFC systems. Various optimization-based methods have been employed to estimate the parameters of PEMFCs, considering the non-linear nature of the equations and characteristic curves involved. In this chapter, we explore the application of metaheuristic optimization algorithms. Besides, this chapter provides insights into the optimization-based techniques employed in the transportation sector to enhance the efficiency and reliability of PEMFCs, contributing to the development of sustainable power generation in transportation applications.

Tin oxide (SnO x ) layers fabricated via atomic layer deposition (ALD) effectively serve as electron transport or sputter-resistant buffer layers in perovskite, silicon, and tandem solar cells, mitigating the interface defect density induced by transparent conductive oxide (TCO) in heterojunction (HIT) photovoltaic devices. This study introduces a 7 nm SnO x layer between P-doped amorphous Si (n-a-Si:H) and TCO to significantly enhance the minority carrier lifetime (MCLT). The incorporation of SnO x increased the MCLT of silicon wafers by approximately 32.5%, from 1328 to 1760 μs, measured at an excess carrier density of 1.0 × 10 15 cm –3 . UV–visible spectroscopy analysis determined the SnO x film bandgap to be 3.48 eV, facilitating effective absorption of plasma-induced radiation and substantially reducing damage during TCO deposition. X-ray photoelectron spectroscopy (XPS) reveals that SnO x ( x ≈ 1.8) exhibits n-type conductivity, effectively passivating n-a-Si:H and mitigating plasma damage, enhancing MCLT. Consequently, the optimized photovoltaic device achieved superior performance, exhibiting a short-circuit current density ( J sc ) of 40.84 mA/cm 2, an open-circuit voltage ( V oc ) of 728 mV, a fill factor (FF) of 80.53%, and an overall power conversion efficiency (PCE) of 23.95%. These findings underscore the potential of ultrathin SnO x layers to enhance both efficiency and durability of advanced silicon-based solar cells.

Miniaturizing concentrator cells is beneficial for heat and spreading resistance losses management. With III-V materials, solar cells cannot be designed much less than 0.1 mm2due to edge recombination. We study thin film Cu(In, Ga)Se2 microcells, where the diffusion length is around 1 μm. Thus small devices (−5cm2) perform well, and the benefits of miniaturization can be exploited throughoufully. A 5% absolute efficiency increase on Cu(In, Ga)Se2 microcells at 475 suns is observed. Voc increases up to several thousand suns, temperature increment stays under 20°C at 1000 suns. Features of the high illumination regime are highlighted and modeled.

Perovskite solar cells have achieved remarkable power conversion efficiencies, yet their long-term stability remains a critical challenge. Progress in understanding this issue can be supported by combining modelling and characterization of the experimental behaviour obtained during ageing. Degradation studies often rely on post-mortem analysis, which is time-intensive, costly, and requires expertise. Here, we present a modelling framework that provides insights into the underlying mechanisms using simple electrical measurements performed during ageing tests. Drift-diffusion and transfer-matrix simulations of the cell optoelectronic response are combined with a genetic algorithm to reproduce the measured JV characteristics. By tracking the evolution of correlations between electrical parameters (V OC , J SC and FF), simulated mechanisms are compared with experimental data, enabling discrimination between feasible pathways associated with performance improvement during light soaking and light-induced degradation. These mechanisms are simulated by varying material parameters such as charge-carrier mobilities, doping levels, defect concentrations in the absorber and at the perovskite/transport-layer interfaces, and parasitic resistances. Comparison between experiment and simulation distinguishes mechanisms that are consistent with the measured trajectories from those that are not, while highlighting plausible candidates associated with both performance improvement during light soaking and light-induced degradation, thereby providing new insights into perovskite solar cell stability.

This study presents a comprehensive mechanical and environmental stability assessment of sub-100 nm PECVD-grown silicon nitride (SiN x ) antireflection coatings in single-layer (SLAR) and double-layer (DLAR) configurations for photovoltaic applications. Nanoindentation was performed on SiN x SLAR 75 nm with refractive index as 2.05 and SiN x DLAR as 55 nm/30 nm, R.I = 1.90/2.10 for top and bottom layer films following deposition temperature ranging from 300 to 400 °C. SiN x SLAR thin film exhibited excellent thermal resilience with hardness decreasing only slightly (15.845–15.666 GPa) and reduced modulus remaining stable (∼165 GPa), while SiN x DLAR coatings showed softening with an ∼2.3 GPa drop in hardness and ∼10 GPa in modulus, attributed to hydrogen effusion and matrix relaxation. Mean contact depths remained within 30% of the film thickness, validating the Oliver–Pharr modeling. AFM scans confirmed dense, defect-free surfaces with R q 0.704 nm for SiN x SLAR and 0.355 nm for DLAR, establishing a high-quality baseline for durability tests. Under damp heat aging (85 °C/85% RH), minority carrier lifetime declined by 4.41% in SiN x SLAR and 2.65% DLAR, with subsequent H 2 -forming gas annealing enabling a partial recovery of 4.13% for SLAR and 2.59% for DLAR. These findings highlight the need to balance mechanical durability and thermal stability in designing reliable antireflection coatings for high-efficiency silicon solar cells.

An innovative two-terminal III–V/c-Si multijunction device is constructed using direct electrode connections and extending the bottom area to improve carrier transport and current matching between the top III–V and bottom c-Si devices. A commercial triple junction GaInP 2 /InGaAs/Ge top cell (1 cm 2 ) with a complete cover electrode at the rear is connected directly to a silicon heterojunction (SHJ) bottom device using silver paste. The area of the SHJ bottom device is enlarged from 0.69 cm 2 to 15 cm 2 to match the current density of the top. With a small active area of 0.69 cm 2, the bottom device has a current density of 13.6 mA/cm 2, comparable to the top device’s (13.5 mA/cm 2 ). By optimizing the SHJ bottom, the multijunction device achieves an impressive efficiency of 39.5% with a short circuit current density of 13.5 mA/cm 2, an open circuit voltage of 3.45 V, and an 85% fill factor. This initial design demonstrates the potential to significantly improve the efficiency of a two-terminal III–V/c-Si tandem device by increasing the matching current levels of both top and bottom cells.

The majority of evidence on the relations between young children’s levels of food neophobia (the fear of novel food), categorization abilities and executive functions is cross-sectional, leaving the direction of causality unclear. This study aimed to examine the bidirectional relations between children’s food neophobia, categorization performance and strategies, and executive functions (working memory, inhibition and cognitive flexibility) longitudinally. Children (n = 113; M age = 48.30 months at Time 1) were assessed at two time points over the course of a year of schooling. Controlling for age, early levels of food neophobia significantly predicted lower subsequent categorization performance and executive functions. No significant evidence was found to support the reverse directionality; neither categorization performance, strategies, nor executive functions at Time 1 predicted subsequent levels of food neophobia. The findings provide longitudinal evidence that neophobia hinders the development of categorization and executive functions abilities.

Disgust reactions significantly impact food choices, particularly in meat consumption, yet the factors influencing their intensity and how individuals justify them remain underexplored. This study (n = 217) provides a novel, comprehensive examination of both disgust intensity and justification patterns across seven meat categories: cultured meat, genetically modified meat, game meat, small farm meat, factory-farmed meat, endangered animal meat, and pet meat. Results revealed that disgust sensitivity and gender significantly impact responses, with women reporting higher disgust intensity and greater likelihood to cite moral concerns as justification. Importantly, our study reveals a previously unidentified interaction effect: familiarity moderates the relationship between perceived naturalness and disgust intensity, suggesting a strategy to enhance acceptance of sustainable food alternatives. The justification patterns exhibited systematic variation by meat type. By bridging core and moral disgust research traditions, this work advances our understanding of how disgust functions at the intersection of biological protection and moral judgment.

The transition from descriptive regularities to prescriptive expectations is linked to the inherence heuristic (a cognitive shortcut attributing observed associations to inherent properties), reinforcing the perception of internal characteristics as defining features of social categories and contributing to gender stereotype endorsement. We investigated how inherent reasoning and moderating factors (i.e. generics and individual characteristics) influence the endorsement of gendered activities. Using a 3 (framing: generics vs. "most" vs. "some") × 2 (typicality: typical vs. countertypical gender associations) design, 241 French participants provided descriptive and prescriptive judgments about gendered associations, with justifications coded for inherence. Results showed that generic statements increased prescriptive judgments and reliance on inherent reasoning compared to “most” statements. Inherent justifications increased prescriptive judgments for typical and reduced them for countertypical gender associations. Inherent reasoning fully mediated the effect of generics on prescriptive judgments. These findings underscore the role of language and cognition in sustaining normative gender expectations.

Re-using the substrate is identified as a method for reducing the cost of high efficiency III-V solar cells. The approach investigated here consists in inserting a graphene layer onto a (001)GaAs substrate prior to the epitaxial growth of GaAs. To obtain a monocrystalline GaAs grown layer, the graphene layer is patterned, followed by a two-step epitaxial growth, here performed by molecular beam epitaxy (MBE). The first step is a selective area growth of GaAs in graphene openings, followed by a lateral overgrowth, under a modulated Ga flux. The second step, after reaching coalescence, consists in a regular growth under continuous Ga supply. It is observed that the pattern orientations relative to the crystallographic direction of the GaAs substrate below the graphene have an influence on GaAs morphology and quality. The best result was obtained for patterns oriented along [1̅10]+22,5° with a graphene coverage of 50%, with a significantly reduced roughness down to 3,3nm.

We investigated a semiconductor heterostructure based on InGaAsP multi quantum wells using optical and electrical characterizations in the scope of hot carrier solar cell device. The potential of the investigated quantum well structure to overpass the Schockley Queisser limit is discussed. Population density, temperature and quasi-Fermi level splitting of photogenerated carriers are investigated by fitting the full luminescence spectra using generalized Planck's law. A proper optical study is realized thanks to a detailed description of the absorption of excitons and free carriers in the quantum well. Optical measurements are compared to electrical measurements where the open circuit voltage electrically measured is higher than the minimum absorption threshold. To probe the hot carrier effect in such measurements we look at the changes in thermodynamic properties of carriers in the quantum well and in the barriers when changing the excitation power and the electrical bias.