1. Gansu Province Organic Semiconductor Materials and Applied Technology Research Centre, School of Material Science and Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China
2. National Green Coating Equipment and Technology Research Centre, Lanzhou Jiaotong University, Lanzhou, 730070, P. R. China
3. School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China
4. Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
5. Department of Chemistry, KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
6. State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China