Analysis of UHV prepared CIS films with surface and bulk sensitive methods

CuInSe₂ was prepared in UHV using conventional bilayer recipes and a novel monolayer approach. The thin film layers were analyzed with surface and bulk sensitive methods. Two different states of the CuInSe₂ surface according to XPS were found: a Cu-rich state containing Cu_2-xSe, and an In-rich state with a Cu/In ratio of 1/3. Direct comparison of surface and bulk compositional data with electrical solar cell device parameters proves that the In-rich surface is essential for reasonable device performance. First results with monolayer-based devices which achieved efficiencies up to 11.5% demonstrate the ability of the simplified process of substitute the bilayer process that is difficult in process control