1. School of Material Science and Engineering, Chongqing University of Arts and Sciences, Chongqing 402160, China
2. Department of Physics, Chongqing University, Chongqing, 400044, China
3. Interdisciplinary Materials Research Center, School of Materials Science and Engineering, Tongji Univ., 4800 Caoan Rd., Shanghai 201804, China
4. Key Laboratory of Photovoltaic and Energy Conservation Materials, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China