1. National Laboratory
of Solid State Microstructures, College of Engineering and Applied
Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
2. Collaborative Innovation Center of Sustainable Energy
Materials, Guangxi University, Nanning 530004, China
3. Department of Physics and Astronomy and
Department of Chemical Engineering and Materials Science, University of California, Irvine, California 92697, United States