1. Department of Engineering Science, University of Science and Technology of China, Hefei 230026, P. R. China
2. Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, P. R. China
3. Guangdong Key Laboratory of New and Renewable Energy Research and Development, Guangzhou 510640, P. R. China
4. CAS Key Laboratory of Renewable Energy, Guangzhou 510640, P. R. China