1. Institute of the polymer Optoelectronic Materials and Devices State Key Laboratory of Luminescent Materials and Devices South China University of Technology Guangzhou 510640 P. R. China
2. School of Materials Science and Engineering Guilin University of Electronic Technology Guilin 541004 P. R. China
3. Molecular Materials and Nanosystems & Institute for Complex Molecular Systems Eindhoven University of Technology MB Eindhoven 5600 The Netherlands