1. Nanjing Tech Center of Research and Development, Nanjing Tech University, Nanjing 211816, People’s Republic of China
2. Division
of Physics and Applied Physics, School of Physical and Mathematical
Sciences, Nanyang Technological University, Singapore 637371
3. Key Laboratory of Flexible Electronics (KLOFE) and Institue of Advanced
Materials (IAM), National Jiangsu Synergistic Innovation Center for
Advanced Materials (SICAM), Nanjing Tech University (Nanjing Tech), 30 South Puzhu Road, Nanjing 211816, People’s Republic of China
4. Key Laboratory for Organic Electronics and Information Displays (KLOEID)
and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210023, Jiangsu, People’s Republic of China
5. Department of Physics,
Faculty of Science, National University of Singapore, Singapore 117542