Solution processable poly(2,5-dialkyl-2,5-dihydro-3,6-di-2-thienyl-pyrrolo[3,4-c]pyrrole-1,4-dione) for ambipolar organic thin film transistors

Solution processable diketopyrrolopyrrole (DPP)-bithiophene polymers (PDBT) with long branched alkyl side chains on the DPP unit are synthesized. These polymers have favourable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels for the injection and transport of both holes and electrons. Organic thin film transistors (OTFTs) using these polymers as semiconductors and gold as source/drain electrodes show typical ambipolar characteristics with very well balanced high hole and electron mobilities (μh = 0.024 cm2 V−1 s−1 and μe = 0.056 cm2 V−1 s−1). These simple and high-performing polymers are promising materials for ambipolar organic thin film transistors for low-cost CMOS-like logic circuits.

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► We report two solution processable diketopyrrolopyrrole (DPP)-based polymers that can be easily synthesized.
► These polymers possess very small band gaps and favorable energy levels for ambipolar charge carrier injection.
► These polymers show ambipolar field effect with high and balanced hole and electron mobilities.
► Unusual molecular ordering and charge transport dependences on annealing temperature are found.