Structural analysis of Cu(In,Ga)Se2 thin-films by depth-resolved XAFS

Cu(In,Ga)Se-2 (CIGS) is a promising material for thin-film photovoltaic devices. Elucidation of the crystal structure of CIGS thin-films is significant for understanding the properties of CIGS solar cells. This study demonstrates the structural evaluation of CIGS thin-films prepared by a three-stage process using Se K-edge depth-resolved X-ray absorption fine structure (XAFS). The CIGS films changed from a Cu-poor to Cu-rich composition during the second stage of the three-stage process. Notably, Cu-2-xSe is generated at the surface of the film at the end of the second stage. After the third stage process, CIGS films have a Cu-poor composition from the surface to a depth of 200 nm. Depth-resolved XAFS technique is sufficiently applicable for evaluation of electronic and crystal structure of CIGS thin-film. This study will provide useful information for the elucidation of the structure of CIGS thin films. (C) 2019 The Japan Society of Applied Physics