1. Department of Materials Science and Engineering
2. University of Science and Technology of China
3. Hefei 230026, P. R. China
4. Key Laboratory of Novel Thin Film Solar Cells
5. Institute of Applied Technology
6. Hefei Institutes of Physical Science
7. Chinese Academy of Sciences
8. Hefei, P. R. China
9. Department of Chemical Engineering
10. University College London
11. London WC1E 7JE, UK
12. Beijing Key Laboratory of Novel Thin Film Solar Cells
13. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources
14. North China Electric Power University
15. Beijing, P. R. China