1. Key Laboratory of Luminescence and Optical Information Ministry of Education Beijing Jiaotong University Beijing 100044 P. R. China
2. College of Physics and Electronic Engineering Taishan University Taian 271021 P. R. China
3. State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials School of Materials Science and Engineering Zhengzhou University Zhengzhou 450001 P. R. China
4. College of Physics and Electronic Engineering Chongqing Normal University Chongqing 401331 P. R. China
5. Guangxi Key Laboratory of Information Materials School of Material Science and Technology Guilin University of Electronic Technology Guilin 541004 P. R. China