1. College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
2. Henan Key Laboratory of Photovoltaic Materials, Xinxiang 453007, China
3. Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
4. College of Electronic and Electrical Engineering, Henan Normal University, Henan 453007, China