1. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Electronic Science and Technology and College of Optoelectronics Engineering Shenzhen University Shenzhen 518000 P. R. China
2. Department of Materials Science and Engineering and ARC Centre of Excellence in Future Low‐Energy Electronics Technologies (FLEET) Monash University Clayton Victoria 3800 Australia
3. School of Mathematical and Physical Sciences Faculty of Science University of Technology, Sydney 15 Broadway Street Ultimo 2007 NSW Australia