1. National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
2. University of Chinese Academy of Science, Beijing 100049, China
3. Changzhou Institute of Optoelectronic Technology, Changzhou 213164, China
4. Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA
5. Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou 213164, China