1. International Joint Laboratory of New Energy Materials and Devices of Henan Province, School of Physics and Electronics, Henan University, Kaifeng 475004, People's Republic of China
2. Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore 487372, Singapore
3. National Demonstration Center for Experimental Physics and Electronics Education, School of Physics and Electronics, Henan University, Kaifeng 475004, People's Republic of China