1College of Physics, Optoelectronics and Energy, Center for Energy Conversion Materials & Physics (CECMP), Jiangsu Key Laboratory of Thin Films, Soochow University, Suzhou 215006, People’s Republic of China
2State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, People’s Republic of China
3Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States