D. Blanc-Pélissier

Time-resolved photoluminescence for self-calibrated injection-dependent minority carrier lifetime measurements in silicon

Time-resolved photoluminescence (TRPL) was investigated on passivated silicon wafers under modulated square-wave laser illumination. It is shown that time-correlated single-photon counting can be used to record the transient signals on silicon wafers with doping levels commonly used for photovoltaic applications. This article reports the self calibrated evaluation of the injection-dependent effective minority carrier lifetime from the TRPL measurements. The method only requires knowing the doping level, the incident laser power, the reflection coefficient and the sample thickness. TRPL results were found to be in good agreement with photoconductance lifetime measurements. The effect of the surface recombination velocity on the generation of the PL signal was shown experimentally and discussed with PC1D calculations.

Laser ablation compatible substoichiometric SiOx/SiNy passivating rear side mirror for passivated emitter and rear thin-film crystalline silicon solar cells

Fabrication of industrial thin-film crystalline silicon solar cells remains challenging because of the high level of light trapping and surface passivation required to achieve a good conversion efficiency, while reducing the process cost. This work proposes a solution of rear side reflector supplying both passivation and light trapping, and guaranteeing compatibility with a laser process for local opening in order to use the passivated emitter and rear cell architecture. The key element is the use of substoichiometric silicon oxide deposited by plasma-enhanced chemical vapor deposition with a higher silicon concentration than the usual nearly stoichiometric oxide. This material is absorbent at usual ultraviolet laser wavelengths, and thus allows laser ablation with limited substrate heat, greatly reducing substrate damage after ablation. A layer of this oxide is incorporated into a SiOx/SiNy dielectric stack, which shows the expected qualities in term of passivation and reflectivity.

Bifacial crystalline silicon homojunction cells contacted with highly resistive TCO layers

This study explores the needed properties of Transparent Conductive Oxides (TCOs) for bifacial homojunction solar cells with potentially passivated contacts. TCO layers with different electrical and optical properties have been tested on both sides of n-type homojunction cells. The high lateral conductivity provided by the diffused emitter and back surface field (BSF) greatly reduces the constraints on TCO electrical properties in such structures. An understanding of the required properties of TCO for advanced homojunction applications is given. Hence different O2-rich Indium Tin oxide (ITO) layers are analyzed optically and electrically before being implemented in homojunction solar cells to evaluate their influence on the device performances. All in all moderately conductive TCOs are shown to be suitable for such applications, allowing better optical properties without inducing resistive losses in the devices.This study explores the needed properties of Transparent Conductive Oxides (TCOs) for bifacial homojunction solar cells with potentially passivated contacts. TCO layers with different electrical and optical properties have been tested on both sides of n-type homojunction cells. The high lateral conductivity provided by the diffused emitter and back surface field (BSF) greatly reduces the constraints on TCO electrical properties in such structures. An understanding of the required properties of TCO for advanced homojunction applications is given. Hence different O2-rich Indium Tin oxide (ITO) layers are analyzed optically and electrically before being implemented in homojunction solar cells to evaluate their influence on the device performances. All in all moderately conductive TCOs are shown to be suitable for such applications, allowing better optical properties without inducing resistive losses in the devices.