1. College of Physics and Energy, Fujian Normal University, Fuzhou, 350117, P. R. China
2. School of New Energy, North China Electric Power University, Beijing, 102206, P. R. China
3. Beijing Huairou Laboratory, Beijing 101400, P. R. China
4. Institute of New Energy, HeXi University, Zhangye, 734000, P. R. China
5. Xiamen Univ. Technol., Sch. Mat. Sci. & Engn., Fujian Prov. Key Lab Funct. Mat. & Applicat., Xiamen, 361024, P. R. China