1. School of New Energy and Materials, Southwest Petroleum University (SWPU), Chengdu 610500, China
2. Institute of Photovoltaic, Southwest Petroleum University, Chengdu 610500, China
3. Key Laboratory of Low-grade Energy Utilization Technologies and Systems (MoE), School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China
4. Tongwei Solar Co, Ltd., Chengdu 610200, China