Naphthalenediimide-Based Copolymers Incorporating Vinyl-Linkages for High-Performance Ambipolar Field-Effect Transistors and Complementary-Like Inverters under Air

We report the synthesis of two novel donor–acceptor copolymers poly{[ N, N ′-bis(alkyl)-1,4,5,8-naphthalene diimide-2,6-diyl- alt -5,5′-di(thiophen-2-yl)-2,2′-( E )-2-(2-(thiophen-2-yl)vinyl)thiophene]} (PNVTs) based on naphthalenediimide (NDI) acceptor and ( E )-2-(2-(thiophen-2-yl)vinyl)thiophene donor. The incorporations of vinyl linkages into polymer backbones maintain the energy levels of the lowest unoccupied molecular orbits at −3.90 eV, therefore facilitating the electron injection. Moreover, the energy levels of the highest occupied molecular orbits increase from −5.82 to −5.61 eV, successfully decreasing the hole injection barrier. Atomic force microscopy measurements indicate that PNVTs thin films exhibit larger polycrystalline grains compared with that of poly{[ N, N ′-bis(2-octyldodecyl)-1,4,5,8-naphthalene diimide-2,6-diyl]- alt - 5,5′-(2,2′-bithiophene)} [P(NDI2OD-T2)], consistent with the stronger π – π stacking measured by grazing incidence X-ray scatting. To optimize devices performance, field-effect transistors (FETs) with three devices configurations have been investigated. The results indicate that the electron mobility of the vinyl-containing PNVTs exhibit about 3–5 times higher than that of P(NDI2OD-T2). Additionally, the vinyl-linkages in PNVTs remarkably enhance ambipolar transport of their top-gate FETs, obtaining high hole and electron mobilities of 0.30 and 1.57 cm 2 V –1 s –1, respectively, which are among the highest values reported to date for the NDI-based polymers. Most importantly, ambipolar inverters have been realized in ambient, exhibiting a high gain of 155. These results provide important progresses in solution-processed ambipolar polymeric FETs and complementary-like inverters.