1. College of Physics Science and Technology, Hebei University, Baoding 071002, China
2. National & Local Joint Engineering Laboratory for New Energy Opto-electronics Devices, Hebei University, Baoding 071002, China
3. Province-Ministry Co-construction Collaborative Innovation Center of Hebei Photovoltaic Technology, Hebei University, Baoding 071002, China
4. Office of International Cooperation, Hebei University, Baoding 071002, China
5. State Key Laboratory of Photovoltaic Materials & Technology, Yingli Solar, Baoding 071051, China