The role of Cu(InGa)(SeS)/sub 2/ surface layer on a graded band-gap Cu(InGa)Se/sub 2/ thin-film solar cell prepared by two-stage method

The purpose of this study is to understand the current baseline process for the absorber formation by a two-stage method and make the process more reliable and reproducible through the investigation of the formation chemistry of the Cu(InGa)Se/sub 2/ (CIGS) thin-film absorbers with a graded band-gap structure and Cu(InGa)(SeS)/sub 2/ (CIGSS) surface layer. A 50-cm/sup 2/ aperture-area efficiency of 13% measured at NREL, which has been reported for the first time in a CIGS thin-film solar module with a Cd-free, sulfur-contained Zn-compound buffer layer, should be a good evidence of the role of CIGSS surface layer on the performance of CIGS thin-film solar cells.