1. Beijing Key Laboratory of Novel Thin-Film Solar CellsNorth China Electric Power University Beijing 102206 P. R. China
2. State Key Laboratory of Alternate Electrical Power System with Renewable Energy SourcesNorth China Electric Power University Beijing 102206 P. R. China
3. Fujian Provincial Key Laboratory of Photoelectric Functional MaterialsInstitute of Materials Physical ChemistryHuaqiao University Xiamen 361021 P. R. China