Investigations on the mechanical properties of the elementary thin films composing a CuIn1−xGaxSe2 solar cell using the nano indentation technique

The aim of this work is to assess the mechanical properties of the different layers composing a CIGS based solar cell. Fabrication uses the magnetron sputtering deposition technique (except for the CdS layer which was deposited using chemical bath deposition process). We performed several indentation tests on individual layers (Mo back contact layer, CIGS absorber layer, CdS and alternative ZnOS buffer layers, ZnO-AZO window layer) deposited on glass substrates. We mainly report the values of hardness (H) and Young's modulus (E) on each material, through indentation tests with continuous stiffness measurement (CSM) and using an analytical model. The Mo layer remains the hardest and most rigid with H = 8.7 GPa and E = 185 GPa, on the other hand the CIGS layer has a weaker behavior with H = 3 GPa and E = 58 GPa. One might attribute the similar mechanical properties of the ZnO and ZnOS layers to the similarity of their microstructures.