1. MOE Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, School of Energy & Power Engineering, Chongqing University, Chongqing 400044, China
2. R&D Center, JA Solar Holdings Co., Ltd., Yangzhou 225131, China
3. Chongqing Key Laboratory of Interface Physics in Energy Conversion, Chongqing University, Chongqing 400044, China
4. Chongqing Key Laboratory of Interface Physics in Energy Conversion, College of Physics, Chongqing University, Chongqing 401331, China