1 Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
2 Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong 999077, China.
3 Department of Mechanical Engineering, The University of Hong Kong, Hong Kong 999077, China. Electronic address: ylu1@hku.hk.
4 College of Materials Science and Engineering, Guangdong Research Center for Interfacial Engineering of Functional Materials, Shenzhen University, Shenzhen 518060, China.
5 Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China. Electronic address: pengdengfeng@szu.edu.cn.