1. Field Effect Device & Flexible Display Lab, School of Materials Science and Engineering, Anhui University, Hefei 230601, P. R. China
2. School of Integrated Circuits, Anhui University, Hefei 230601, P. R. China
3. Department of Materials Science/CENIMAT-I3N, Faculty of Sciences and Technology, New University of Lisbon and CEMOP-UNINOVA Campus de Caparica 2829-516 Caparica, Portugal