Tunable Crystalline Structures of Diketopyrrolopyrrole (DPP)-based Semiconducting Polymers for High-Performance Organic Field-Effect Transistors

초록

Novel semiconducting polymers containing electron donors (D) and acceptors (A) were synthesized in order to improve the electrical properties of these solid forms in organic electric devices. Here, we prepared solution-processed copolymers with diketopyrrolopyrrole (DPP) acceptor and thiophene (or selenophene) donor groups. In addition, alkyl side-chain components were changed to optimize the solution-processability and directed self-assembly of these polymers during film processes. DPP-based semiconducting polymer films were solution-cast on hydroxyl free gate dielectrics (polymer grafted oxide dielectrics) from various solutions. Some of the cast films were further post-treated to improve these crystallinities and π-conjugated orientations. Electrical properties of the cast DPP polymer films in organic field-effect transistors (OFETs) were characterized and correlated with the corresponding crystal structures, as determined by scanning probe microscopy (atomic force microscopy, AFM, for surface morphology), synchrotron-based grazing-incidence X-ray diffraction (GIXD, for crystalline structure and crystallinity), and near-edge X-ray absorption fine structure (NEXAFS, for orientation of pi-stacked plain).