1. School of Physics Science and Technology, Lingnan Normal University, Zhanjiang 524048, P. R. China
2. Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang 330063, P. R. China
3. School of Materials and Chemical Engineering, Xi’an Technological University, Xi’an 710021, P. R. China
4. School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia