1. Technical Institute of Physics and ChemistryChinese Academy of Sciences Beijing 100190 China
2. University of Chinese Academy of Sciences Beijing 100190 China
3. The Beijing Municipal Key Laboratory of New Energy Materials and TechnologiesSchool of Materials Sciences and EngineeringUniversity of Science and Technology Beijing Beijing 100083 P. R. China
4. State Key Laboratory of Luminescent Materials and Devices andInstitute of Optical Communication MaterialsSouth China University of Technology Guangzhou 510641 China
5. Center of Materials Science and Optoelectronics EngineeringUniversity of the Chinese Academy of Sciences Beijing 100049 China