1. Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
2. Henan Key Laboratory of Photovoltaic Materials and School of Physics & Electronics, Henan University, Kaifeng 475004, China
3. Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade 11001, Serbia
4. Department of Natural Sciences, Baruch College, CUNY, New York, New York 10010-5585, United States
5. Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China