1. School of Physics and Optoelectronics State Key Laboratory of Luminescent Materials and Devices and Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques South China University of Technology Guangzhou Guangdong 510641 P. R. China
2. The Beijing Municipal Key Laboratory of New Energy Materials and Technologies School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 P. R. China
3. Anhui Province Key Laboratory of Optoelectric Materials Science and Technology Key Laboratory of Functional Molecular Solids Ministry of Education Anhui Normal University Wuhu Anhui 241000 P. R. China