1. National Center for International Research on Photoelectric and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, P. R. China
2. Kunming Institute of Physics, Kunming 650223, P. R. China
3. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
4. National Engineering Research Center for Marine Aquaculture, Marine Science and Technology College, Zhejiang Ocean University, Zhoushan 316004, P. R. China