1. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P. R. China
2. Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
3. Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, P. R. China
4. National Synchrotron Radiation Laboratory (NSRL), University of Science and Technology of China, Hefei, Anhui 230029, P. R. China