1. Department of Optoelectronic Engineering Key Laboratory of Optoelectronic Technology and Systems Ministry of Education Chongqing University Chongqing 400044 P. R. China
2. Department of Optoelectronic Engineering Chongqing Key Laboratory of Laser Control & Precision Measurement Chongqing University Chongqing 400044 P. R. China
3. Chongqing Institute of Green and Intelligent Technology Chinese Academy of Sciences Chongqing 400714 P. R. China
4. School of Materials Science and Engineering Georgia Institute of Technology Atlanta GA 30332 USA
5. Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing 100083 P. R. China