1. Laboratory of Advanced
Materials, Department of Materials Science, Collaborative Innovation
Center of Chemistry for Energy Materials, Fudan University, Shanghai 200438, P. R. China
2. State Key Laboratory for Superlattices and Microstructures, Institute
of Semiconductors, Chinese Academy of Sciences, Beijing 100083, P. R. China
3. College of Materials Science and Opto-Electronic
Technology, University of Chinese Academy of Sciences, Beijing 100083, P. R. China
4. National
Laboratory of Solid State Microstructures, School of Electronic Science
and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China