1. School of Materials Science and Engineering and Tianjin Key Laboratory of Molecular Optoelectronic Science Tianjin University Tianjin 300072 P. R. China
2. MIIT Key Laboratory of Advanced Display Materials and Devices School of Materials Science and Engineering Nanjing University of Science and Technology Nanjing 210094 P. R. China
3. Institute of Molecular Plus Tianjin University Tianjin 300072 P. R. China