1. Innovative Center for Flexible Devices (iFLEX)School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
2. Institute of Materials Research and Engineering Agency for Science, Technology and Research (A*STAR) 2 Fusionopolis Way Singapore 138634 Singapore
3. College of Chemical Engineering and Materials ScienceQuanzhou Normal University Quanzhou 362000 Fujian Province P. R. China