Growth analysis of chemical bath deposited In(OH)/sub x/S/sub y/ films as buffer layers for CuInS/sub 2/ thin film solar cells

Although the deposition of In(OH)/sub x/S/sub y/ by chemical bath deposition has been successfully demonstrated before, the deposition mechanism remains unclear. Using X-ray photoelectron spectroscopy, the authors have identified two growth phases: an initial nucleation of mainly In(OH)/sub x/O/sub y/ followed by rapid, mainly colloidal growth of In(OH)/sub x/S/sub y/. The deposited films are additionally characterized using elastic recoil detection analysis, transmission and scanning electron microscopy. An indirect energy band gap was observed at /spl sim/2.2 eV by optical transmission spectroscopy. The method has been used to make a Cd-free buffer layer for CuInS/sub 2/ thin film solar cells and an efficiency of 9.1% has been achieved.