One of the major challenges confronting organic electronics is the development of high-mobility semiconducting materials, especially n-channel and ambipolar semiconductors. Solution-processable semiconducting polymers have attracted much attention because of their tunable properties and their suitability for the fabrication of large-scale devices. Aza substitution has proven effective in electron-transport small-molecule semiconductors; however, high-performance polymeric semiconductors prepared by aza substitution are still lacking. We started with a computational screening procedure to introduce nitrogen atoms into isoindigo-based polymers and then proceeded with the synthesis and fabrication of field-effect transistors. The resulting 7,7′-diazaisoindigo-based polymers exhibit extensive π conjugation and high crystallinity with hole mobilities exceeding 7 cm 2 V −1 s −1 with bottom-gate/bottom-contact configuration and ambipolar transport properties with top-gate/bottom-contact configuration in air. These properties make diazaisoindigo a promising building block for polymeric semiconductors.

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-2,6diyl]-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.