1. Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, P. R. China
2. SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P. R. China
3. Key Laboratory for Micro-/Nano-Optoelectronic, Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, P. R. China