1. National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
2. Photovoltaic Power Generation Technology Research Association (PVTEC), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
3. Kaneka Corporation, 157-34 Kamiyoshidai, Toyooka, Hyougo 668-0831, Japan
4. Panasonic Corporation, 3-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0237, Japan
5. Fukushima University, 1 Kanayagawa, Fukushima, Fukushima 960-1296, Japan