1. State Key Laboratory of Electronic Thin Films and Integrated Devices; University of Electronic Science and Technology of China; Chengdu 610054 P. R. China
2. Hunan Provincial Key Laboratory of Thin Film Materials and Devices; School of Materials Science and Engineering; Xiangtan University; Xiangtan 411105 Hunan P. R. China
3. State Key Laboratory of Material Processing and Die and Mould Technology; School of Materials Science and Engineering; Huazhong University of Science and Technology; Wuhan 430074 P. R. China
4. College of Physics; Optoelectronics and Energy; Center for Energy Conversion Materials and Physics (CECMP); Soochow University; Suzhou 215006 P. R. China