1. Hebei Key Lab of Optic-electronic Information and Materials, College of Physics Science and Technology, Hebei University, Baoding 071002, China
2. State Key Laboratory of Photovoltaic Materials & Technology, Yingli Green Energy Holding Co., Ltd., Baoding 071051, China
3. Institute of New Energy Technology, College of Information Science and Technology, Jinan University, Guangzhou, 510632, China