1. Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM); National Jiangsu Synergetic Innovation Center for Advanced Materials (SICAM); Nanjing Tech University (NanjingTech); 30 South Puzhu Road Nanjing 211816 China
2. Division of Physics and Applied Physics; School of Physical and Mathematical Sciences; Nanyang Technological University; 637371 Singapore
3. School of Materials Science and Engineering; Nanyang Technological University; 639798 Singapore
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 China
5. Department of Physics; Faculty of Science; National University of Singapore; 117542 Singapore