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

Abstract

We report the synthesis of two novel\ndonor–acceptor copolymers\npoly­{[<i>N</i>, <i>N</i>′-bis­(alkyl)-1,4,5,8-naphthalene\ndiimide-2,6-diyl-<i>alt</i>-5,5′-di­(thiophen-2-yl)-2,2′-(<i>E</i>)-2-(2-(thiophen-2-yl)­vinyl)­thiophene]} (PNVTs) based on\nnaphthalenediimide (NDI) acceptor and (<i>E</i>)-2-(2-(thiophen-2-yl)­vinyl)­thiophene\ndonor. The incorporations of vinyl linkages into polymer backbones\nmaintain the energy levels of the lowest unoccupied molecular orbits\nat −3.90 eV, therefore facilitating the electron injection.\nMoreover, the energy levels of the highest occupied molecular orbits\nincrease from −5.82 to −5.61 eV, successfully decreasing\nthe hole injection barrier. Atomic force microscopy measurements indicate\nthat PNVTs thin films exhibit larger polycrystalline grains compared\nwith that of poly­{[<i>N</i>, <i>N</i>′-bis­(2-octyldodecyl)-1,4,5,8-naphthalene\ndiimide-2,6-diyl]-<i>alt</i>- 5,5′-(2,2′-bithiophene)}\n[P­(NDI2OD-T2)], consistent with the stronger <i>π</i>–<i>π</i> stacking measured by grazing incidence\nX-ray scatting. To optimize devices performance, field-effect transistors\n(FETs) with three devices configurations have been investigated. The\nresults indicate that the electron mobility of the vinyl-containing\nPNVTs exhibit about 3–5 times higher than that of P­(NDI2OD-T2).\nAdditionally, the vinyl-linkages in PNVTs remarkably enhance ambipolar\ntransport of their top-gate FETs, obtaining high hole and electron\nmobilities of 0.30 and 1.57 cm² V^–1 s^–1, respectively, which are among the highest values\nreported to date for the NDI-based polymers. Most importantly, ambipolar\ninverters have been realized in ambient, exhibiting a high gain of\n155. These results provide important progresses in solution-processed\nambipolar polymeric FETs and complementary-like inverters.