1. School of Future Technology, Henan Key Laboratory of Photovoltaic Materials, Henan University, No.1 Jinming Road, Kaifeng, Henan 475004, P. R. China
2. State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China
3. Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, Anhui 230031, P. R. China