1. State Key Laboratory of Luminescent Materials and Devices; South China University of Technology; Guangzhou 510641 P. R. China
2. Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province; South China University of Technology; Guangzhou 510641 P. R. China
3. Department of Electronic Materials; School of Materials Science and Engineering; South China University of Technology; Guangzhou 510640 P. R. China