1. Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Guangdong, P. R. China
2. School of Physical Science and Technology, Ningbo University, Ningbo, China
3. State Key Laboratory on Advanced Displays and Optoelectronics Technologies, Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
4. School of Physics and Optoelectronic Engineering, Foshan University, Guangdong, China