1. National Center for International Research on Photoelectric and Energy Materials School of Materials and Energy Yunnan University Kunming 650091 P. R. China
2. College of Materials Science and Engineering Kunming University of Science and Technology Kunming 650093 P. R. China
3. Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information Huazhong University of Science and Technology (HUST) Wuhan 430074 P. R. China
4. Department of Applied Chemistry Interdisciplinary Research Center of Smart Sensor School of Advanced Materials and Nanotechnology Xidian University Xi'an 710126 P. R. China
5. Centre for Translational Atomaterials Swinburne University of Technology Hawthorn 3122 Australia
6. Department of Electrical and Computer Engineering University of Houston Houston TX 77204 USA
7. Texas Center for Superconductivity University of Houston Houston TX 77204 USA