1. Organic Semiconductor Materials and Applied Technology Research Centre of Gansu Province, School of Materials Science and Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China
2. National Green Coating Equipment and Technology Research Center, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China
3. Department of Chemistry, KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea