1. Research Center for Advanced Information Materials (CAIM), Huangpu Research and Graduate School of Guangzhou University, Guangzhou 510555, China
2. Solid State Physics & Material Research Laboratory, School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
3. School of Physics, Guangdong Province Key Laboratory of Display Material and Technology, Sun Yat-sen University, Guangzhou 510275, China