Enhancing the electrical and thermal stability of organic thin‐film transistors by utilizing fluorinated polyimide and silicon dioxide bilayer gate dielectric

The grand vision of next generation electronics is expected to realize via the wholescale industrialization of organic devices. However, one serious obstacle hindering the practical application for organic devices is their instability regardless of it induced by high temperatures or sustained gate bias stress. Herein, pentacene-based thin-film transistors (TFTs) with both good heat resistance and high electrical stability were realized. The TFTs, where fluorinated polyimide (ODA-6FDA PI) and a silicon dioxide (SiO2) bilayer are used as gate dielectric, exhibit superior electrical stability under protracted gate bias stress for 150 min (Delta V-th similar to 1 V with voltage range of 30 to -60 V) and are extremely less susceptible to annealing treatment for temperatures up to 150 degrees C (Delta mu/mu(0) similar to 2.9%), as compared to counterparts with a single dielectric layer. We demonstrated that the excellent bias-stress stability arises from the higher activation energy of defects of fluorinated PI surface based on exponential barrier distribution model and the suppression of charge injection and back-channel effect via bilayer. Also, the superior thermal stability is ascribed to the restraint of film cracks and phase transformation of pentacene at high temperatures induced by the better match between the thermal expansion coefficients of semiconductor and dielectric. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47013.