Etude des Caractéristiques de la cellule photovoltaïque à Base de CIGS. Modélisation de la Tenue Mécanique.

Abstract

Our ultimate goal is to develop a sputter deposition process only; for the development of CIGS-based solar cells. In addition, achieving a reduced environmental mark, led us to remove both the selenization step and the cadmium material from the fabrication process. An original deposition process for the absorbent layer (CIGS) will be presented; it brings together the three main guidelines, namely the use of a single quaternary target, the absence of the Sebased process and a limited thermal budget. The mechanical holding of the different layers composing a CIGS based solar cell is believed to highly affect the longevity of this cell. Therefore, studying fundamental mechanical properties of the different layers composing a CIGS solar cell is a real need. Following the analytical model of Jönsson and Hogmark, the resulting the resulting mark of the nano indentation is used to deduce the mechanical properties of the studied material. Magnetron sputtering technique was used for the deposition of these layers except for the cadmium sulphide (CdS) layer which was deposited using chemical bath deposition process. We performed several indentation tests on the individual layers, i.e. molybdenum (Mo) back contact layer, CIGS absorber layer, CdS and alternative zinc sulphide oxide (ZnOS) buffer layers, and zinc oxide (ZnO)-AZO (aluminium-doped zinc oxide) transparent window layer; all were deposited on glass substrates. We report the values of the hardness (H) and of the Young's modulus (E) for each material, using indentation tests and an analytical model. The Mo layer remained the hardest and the most rigid, with H = 8.7 GPa and E = 185 GPa, while the CIGS layer has shown poor mechanical properties with H = 3 GPa and E = 58 GPa. On the other hand, the observed similarity in mechanical properties of the ZnO and ZnOS layers might be attributed to the similarity of their microstructures. The same work has been reproduced on multilayer structures using the analytical model of Rahmoun and Iost