1. School of Physics and Electronic Information, Yantai University, Yantai 264005, People's Republic of China
2. State Key Laboratory of Applied Organic Chemistry (Lanzhou University), Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P.R. China
3. New Energy (Photovoltaic) Industry Research Center, Qinghai University, Xining 810006, People's Republic of China