1. Institute of Materials Research and Engineering Agency for Science, Technology and Research (A*STAR) 2 Fusionopolis Way, Innovis, #08‐03 Singapore 138634 Singapore
2. Innovative Centre for Flexible Devices (iFLEX) Max Planck–NTU Joint Lab for Artificial Senses School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
3. School of Electronic Science & Engineering and Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210023 P. R. China
4. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Optoelectronic Engineering Shenzhen University Shenzhen 518060 P. R. China
5. Innovation Center for Chemical Science College of Chemistry Chemical Engineering and Materials Science Soochow University Suzhou 215123 P. R. China