1. School
of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, P. R. China
2. School
of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States
3. Hubei
Collaborative Innovation Center for Advanced Organic Chemical Materials,
College of Chemistry and Chemical Engineering, Hubei University, Wuhan, Hubei 430062, P. R. China