1. Division of Solar Cell Technology, Department of Materials Science and Engineering, Uppsala University, Box 534, Uppsala SE-751 21, Sweden
2. Faculty of Electronics and Informational Technologies, Sumy State University, 2 Rymsky Korsakov Str., Sumy 40007, Ukraine
3. Division of Solid State Electronics, Department of Electrical Engineering, Uppsala University, Box 534, Uppsala SE-751 21, Sweden