1. School
of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 China
2. School
of Information Science and Technology, Sun Yat-Sen University, Guangzhou 510006 China
3. State Key Laboratory of Optoelectronic Materials and Technologies, Guangzhou 510275 China
4. Guangdong Provincial Key Laboratory of Photovoltaics Technologies, Guangzhou 510006 China