1. Institute of Photoelectronic Thin Film Devices and Technology , Renewable Energy Conversion and Storage Center, Solar Energy Conversion Center, Nankai University , Tianjin 300350 , P. R. China
2. Key Laboratory of Photoelectronic Thin Film Devices and Technology of Tianjin , Tianjin 300350 , P. R. China
3. Engineering Research Center of Thin Film Photoelectronic Technology of Ministry of Education , Tianjin 300350 , P. R. China
4. Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) , Tianjin 300072 , P. R. China