1. MOE Key Laboratory of Resources and Environmental Systems Optimization College of Environmental Science and Engineering North China Electric Power University Beijing 102206 China
2. College of Materials Science and Engineering Changsha University of Science and Technology Changsha Hunan 410004 P. R. China
3. Electrochemical Engineering Department of Engineering and Physical Sciences University of Southampton United Kingdom
4. Beijing Key Laboratory of Novel Thin Film Solar Cells North China Electric Power University Beijing 102206 China