Designing Thermally Stable Conjugated Polymers with Balanced Ambipolar Field-Effect Mobilities by Incorporating Cyanovinylene Linker Unit

Abstract

We present a developed highly balanced and thermally stable ambipolar semiconducting polymer PBCDC consisting of diketopyrrolo[3,4-c]pyrrole and benzo[1,2-b:4,5-b′]dithiophene building blocks connected by a cyanovinylene linker unit. Stabilization of the frontier molecular orbitals and delocalization of the LUMO on the whole structural unit were realized by introducing the strong electron-withdrawing cyanovinylene linker. In addition to such electronic effects, the molecular stacking and crystallinity of the polymer film were significantly controlled by the presence of the cyanovinylene linker, which was preserved with no variation at different annealing temperatures. As a result of these electronic and structural effects of cyanovinylene, organic field-effect transistors based on the PBCDC exhibit highly balanced hole and electron mobilities of μh,max ∼ 0.2 cm2 V–1 s–1 and μe,max ∼ 0.2 cm2 V–1 s–1, respectively, which are virtually independent of the annealing temperature over the range of 80–250 °C.