1. School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, P. R. China
2. Future Display Institute of Xiamen, Xiamen 361005, P. R. China
3. Department of Materials Science and Engineering and Centre for Functional Photonics (CFP), City University of Hong Kong, Kowloon, Hong Kong SAR 999077, P. R. China
4. Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, P. R. China
5. Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Xiamen University, Xiamen 361005, P. R. China