Ambient-stable, annealing-free, and ambipolar organic field-effect transistors based on solution-processable poly(2,2'-bis(trifluoromethyl)biphenyl-alt-2,5-divinylthiophene) without long alkyl side chains

An ambipolar conjugated polymer CF₃-PBTV, poly(2,22'-bis(trifluoromethyl) biphenyl-alt-2,5-divinylthiophene), consisting of thienylenevinylene as the donor and trifluoromethyl-substituted biphenyl as the acceptor has been successfully synthesized. CF₃-PBTV shows solution-processability without electrically insulating long alkyl side chains. Grazing incidence X-ray diffraction results suggest a nearly equal population of flat-on and end-on domains in CF₃-PBTV thin film. The excellent ambipolarity of CF₃-PBTV is demonstrated by well-equivalent charge mobilities of 0.065 and 0.078 cm² V^-1 s^-1 for p- and n-channel, respectively. The organic field-effect transistors (OFET) also shows very high on/off ratio (≈10⁷) which is attributed to the relatively large bandgap and low-lying highest occupied molecular orbital (HOMO) of CF₃-PBTV. The OFET performance barely changes after the device is stored in ambient conditions for 90 days. The ambient-stability is attributed to the enhanced oxidative stability from its low-lying HOMO and the better moisture resistance from its fluorine contents. The performance of CF₃-PBTV based OFET is annealing independent. It is noteworthy that the solution-processable, ambipolar, and thienylenevinylene-containing conjugated polymer without any long alkyl side chains is reported for the first time. And to the best of our knowledge, it is the first ambient-stable, annealing-free OFET with well-equivalent ambipolarity.