1. Key
Laboratory of Novel Thin Film Solar Cells, Institute of Applied Technology,
Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui 230088, P. R. China
2. University of Science and Technology of China, Hefei 230026, P. R. China
3. Beijing
Key Laboratory of Novel Thin Film Solar Cells, North China Electric Power University, Beijing 102206, P. R. China