1. Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, School of Physics and Optoelectronics, Xiangtan University 1 , Hunan 411105, People's Republic of China
2. Hunan Institute of Technology 2 , Hengyang, Hunan 411102, People's Republic of China
3. School of Physics and Optoelectronic Engineering, Shandong University of Technology 3 , Zibo, Shandong 255100, People's Republic of China