1. Key
Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, Anhui 230031, People’s Republic of China
2. Department
of Engineering Science, Faculty of Informatics and Engineering, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan
3. CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi,
Saitama 332-0012, Japan
4. School
of Renewable Energy, North China Electric Power University, Beijing 102206, People’s Republic of China