1. School of Materials Science and Engineering, Chongqing Jiaotong University, Chongqing 400074, China
2. Institute of Solid-State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
3. Key Laboratory of Photovoltaic and Energy Conservation Materials, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
4. School of Mechatronics and Vehicle Engineering, Chongqing Jiaotong University, Chongqing 400074, China
5. University of Science and Technology of China, Hefei 230026, China