1. College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, P. R. China
2. Institute of Environmental Energy Materials and Intelligent Devices, School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology. Chongqing 401331, P. R. China
3. Key Laboratory of Optoelectronic Technology and System of Ministry of Education, College of Optoelectronic Engineering, Chongqing University, Chongqing 400030, P. R. China