1. School of New Energy and Materials, Southwest Petroleum University, Xindu Avenue No. 8, Chengdu 610500, P. R. China
2. Institute of Photovoltaic, Southwest Petroleum University, Xindu Avenue No. 8, Chengdu 610500, P.R. China
3. Institute of New Energy Technology, College of Information Science and Technology, Jinan University, No. 855 Xingye Avenue East, Guangzhou 510632, P.R. China