1. Institute of Photovoltaics, Southwest Petroleum University, Chengdu 610500, People’s Republic of China
2. Institute for Clean Energy & Advanced Materials, Faculty of Materials and Energy, Southwest University, Chongqing 400715, People’s Republic of China
3. Panzhihua Engineering Technology Research Center for Graphene, Panzhihua University, Panzhihua 617000, P. R. China