1. Laboratory of Advanced Nano-Optoelectronic Materials and Devices, Qianwan Institute of CNITECH, Ningbo, Zhejiang 315336, P. R. China
2. International Joint Research Center of China for Optoelectronic and Energy Materials, Energy Research Institute, Yunnan University, Kunming, Yunnan 650091, P. R. China
3. Laboratory of Advanced Nano-Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Science, Ningbo, Zhejiang 315201, P. R. China
4. Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, P. R. China