1. Ministry of Education Key Laboratory of Micro and Nano Systems for Aerospace Northwestern Polytechnical University Xi'an 710072 P. R. China
2. State Key Laboratory of Optoelectronic Materials and Technologies and the Guangdong Province Key Laboratory of Display Material and Technology School of Electronics and Information Technology Sun Yat‐sen University Guangzhou 510275 P. R. China
3. Frontiers Science Center for Flexible Electronics (FSCFE) Xi'an Institute of Flexible Electronics (IFE) and Xi'an Institute of Biomedical Materials and Engineering (IBME) Northwestern Polytechnical University Xi'an 710072 P. R. China
4. Faculty of Engineering and Environment Northumbria University Newcastle upon Tyne NE1 8ST UK