Marie-Estelle Gueunier-Farret

We report on the integration of a sputtered indium tin oxide transparent top electrode for semi-transparent organic solar cells (ST-OSCs). To mitigate sputtering-induced damage to the underlying organic layers, a MoO3 interlayer is introduced, acting simultaneously as a hole transport layer and as a protective buffer layer during the sputtering process. The best-performing ST-OSC, based on wide-bandgap donor polymer PM6 and acceptor GS-ISO, achieved power conversion efficiencies (PCEs) of 4.6% under bottom illumination and 4% under top illumination. Furthermore, a mild thermal annealing (55 °C) for 5 h leads to a significant performance enhancement for ST-OSC, with PCE reaching up to 5.8%, resulting in improved operational stability compared to conventional opaque OSCs over 200 h testing.

F8T2 solid additive improves the performance of PM6:GS-ISO wide band-gap solar cells thanks to the enhancement of GS-ISO crystallinity. Efficiency up to 10% PCE was achieved under 1 sun, showing potentiality for lateral multijunction architectures.

Very high conversion efficiency is reached with triple junction solar devices integrated in concentrator photovoltaic (CPV) modules. However, reduction of the active area for micro-CPV applications increases the perimeter/area ratio, enhancing losses linked to the edges. It is therefore important to characterize the perimeter influence on the final conversion efficiency. For this purpose, I(V) characterization under dark and/or light could be used as a test of the sidewalls influence. We have designed an experiment to perform I(V) curves using the light of three lasers with adjustable powers at 405, 785, and 980 nm, preferentially absorbed by the top, middle or bottom junction of the device, respectively. This experiment was applied to commercial devices made from a stack of GaInP/GaAs/Ge. In parallel we have developed a numerical calculation modeling the device to reproduce the behaviors observed during I(V) experiments. Junction parameters and influence of leakage resistances are deduced from the fit of experimental results with the numerical calculation. The I(V) experiment as well as the numerical calculation are presented in details. It is also underlined that, combining both experiment and calculation, the I(V) characteristic of each junction as if it was isolated can be determined.

Epitaxial silicon layers were grown on highly doped c-Si substrates using the plasma-enhanced chemical vapour deposition process (PECVD) at low temperature (175 °C). The transport and defect-related properties of these epi-Si layers were characterized by current density-voltage (J–V) and capacitance–voltage (C–V) techniques. The results show that the epi-Si layers exhibit a non-intentional n-type doping with a low apparent doping density of about 2 × 10¹⁵ cm⁻³. The admittance spectroscopy technique is used to investigate the presence of deep-level defects in the structure. An energy level at 0.2 eV below the conduction band has been found with a density in the range of 10¹⁵ cm⁻³ which may explain the observed apparent doping profile.

This paper presents a simple and nondestructive method to determine doping densities and built‐in potential of subcells by adapting the well‐known capacitance‐voltage (C‐V) technique to two‐terminal (2 T) tandem solar cells. Because of the electrical coupling between the two subcells in a monolithic 2 T tandem solar cell, the standard method using a Mott‐Schottky plot (1/C² vs V) cannot be applied. Using numerical modeling, it is demonstrated that, by under chosen illumination conditions where only one subcell can absorb the light, it is possible to explore the bias dependence of the capacitance and to extract the parameters of the other subcell if the appropriate frequency conditions are present. This method is experimentally applied to an AlGaAs/Si tandem cell, and parameters of both AlGaAs and Si cells are extracted. Finally, the validity of that method is assessed by the very good agreement obtained when comparing the values extracted from our measurements on the tandem cell to those extracted from measurements on isotype cells and to the values targeted during the fabrication process of the AlGaAs/Si tandem solar cell.

Halide Perovskites are considered as solid semiconductors since the beginning of their solar cell development. However, on their film or devices, direct and indirect observations of mobile ions are currently reported. Mobile ions are included in the present study within the drift-diffusion approximations, in addition to general carriers. Ion migration inside the perovskite layer and the abnormal hysteresis effect in the current-voltage measurements are simulated in comparison with the experiments of classic perovskite solar cells. The work is promising for the advancements of halide-perovskite-based devices, such as solar cells, light emitting diodes, lasers, photodetectors, transistors, or memoirists.

Passivating the contacts of crystalline silicon (c‐Si) solar cells with a poly‐crystalline silicon (poly Si) layer on top of a thin silicon oxide (SiO _x ) film are currently of growing interest to reduce recombination at the interface between the metal electrode and the c‐Si substrate. This study focuses on the development of boron‐doped poly‐Si/SiO _x structure to obtain a hole selective passivated contact with a reduced recombination current density and a high photo‐voltage potential. The poly‐Si layer is obtained by depositing a hydrogen‐rich amorphous silicon layer by plasma enhanced chemical vapor deposition (PECVD) exposed then to an annealing step. Using the PECVD route enables to single side deposit the poly Si layer, however, a blistering of the layer appears due to its high hydrogen content, which leads to the degradation of the poly‐Si layer after annealing. In this study, the deposition temperature and gas flow ratio used during PECVD step are optimized to obtain blister‐free poly‐Si layer. The stability of the surface passivation properties over time is shown to depend on the blister density. The surface passivation properties are further improved thanks to a post process hydrogenation step. As a result, a mean implied photo‐voltage value of 714 mV is obtained.

Passivating contacts of crystalline silicon (c-Si) solar cells with a poly-silicon layer (poly-Si) on a thin silicon oxide (SiO_x) film offer an interesting approach to decrease the recombination current at the metal/c-Si interface and to increase the cell efficiency. This study focuses on the development of boron-doped poly-Si layers deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) on top of a thin silicon oxide film. First, the deposition and annealing conditions were optimised in order to: (1) reduce the blistering of the poly-Si on the thin SiO_x film and (2) improve the poly-Si conductivity. The passivation properties of the resulting structures have been shown to depend on the blister density and have been improved through a hydrogenation step leading to a maximum implied open-circuit voltage value of 721 mV.