Formation chemistry of polycrystalline Cu(InGa)Se-2 thin-film absorbers prepared by selenization of Cu-Ga/In stacked precursor layers with H2Se gas

The purpose of this study is to improve the reliability and reproducibility of our fabrication process for polycrystalline Cu(InGa)Se-2 (CIGS) thin-film absorbers and to make a better absorber with higher efficiency. The current baseline process of selenization has been evaluated through the investigation of the formation chemistry of the device-quality CIGS thin-film absorbers with a graded band-gap structure. It has been verified that the current selenization process has been performed in a good balancing point with both Cu/III ratio and thickness of the precursor layer and the total amount of Se through H2Se gas incorporated from the surface during the selenization. A simplified model to explain the formation chemistry of the selenization in this study has been proposed.