1. Key Laboratory of Flexible Electronics (KLOFE)Institute of Advanced Materials (IAM)Jiangsu National Synergistic Innovation Center for Advanced Materials (SICAM)Nanjing Tech University (NanjingTech) 30 South Puzhu Road Nanjing 211816 P. R. China
2. Department of Educational ScienceLaboratory of College PhysicsHunan First Normal University Changsha 410205 Hunan P. R. China
3. Shanghai Synchrotron Radiation FacilityShanghai Institute of Applied PhysicsChinese Academy of Sciences Shanghai 201204 P. R. China
4. National Laboratory of Solid State MicrostructuresSchool of Physics & Collaborative Innovation Center of Advanced MicrostructuresNanjing University Nanjing 210093 P. R. China
5. Shaanxi Institute of Flexible Electronics (SIFE)Northwestern Polytechnical University (NPU) 127 West Youyi Road Xi'an 710072 P. R. China
6. Key Laboratory for Organic Electronics & Information Displays (KLOEID)Institute of Advanced Materials (IAM)Nanjing University of Posts and Telecommunications 9 Wenyuan Road Nanjing 210023 P. R. China