Etude de la passivation de surface du silicium cristallin type P par dépôt de couches atomiques d'alumine pour application aux cellules solaires à haut rendement

摘要

The decrease of solar cell cost as well as the increase in their efficiency are main research topics since the photovoltaic market crisis in 2011. One of the main strategy is to move towards thinner solar cells, in order to decrease raw material consumption. However, the result is a higher impact of surface phenomena on cell characteristics because of a high influence of structure and electronic defects at the surface. These defects can be passivated by Al2O3 coated by PE-ALD (Plasma Enhanced-Atomic Layer Deposition) which has been shown to provide the best surface passivation on p-type silicon. In an as-deposited state, the passivation level of Al2O3 is very low and required an annealing treatment to be "activated". This phenomenon provides an increase of the minority carrier effective lifetime. This thesis founded by the ANR PROTERRA and BIFASOL projects with the financial support of the Ecole Centrale de Lille, focuses on the optimization of the deposition parameters of alumina with a deeper insight on the passivation activation phenomena on samples with and without emitter. The passivation analysis has been performed thanks to coupled lifetime (QSS and micro PCD), surface potential (Kelvin probe), electrical (C-V) and chemical (SIMS, XPS) characterizations. The origin of the chemical and field effect passivation has been determined within the Si/SiO2/Al2O3 stack. The dynamics of the hydrogen contained in bulk alumina is explained. The impact of a SiNx capping layer and a contact alloying anneal at 830°c for 3s is also investigated