Engineering donor–acceptor conjugated polymers for high-performance and fast-response organic electrochemical transistors

To date, high-performance organic electrochemical transistors (OECTs) are all based on polythiophene systems. Donor-acceptor (D-A) conjugated polymers are expected to be promising materials for OECTs owing to their high mobility and comparatively low crystallinity (good for ion diffusion). However, the OECT performance of D-A polymers lags far behind that of the polythiophenes. Here we synergistically engineered the backbone, side chain of a series of diketopyrrolopyrrole (DPP)-based D-A polymers and found that redox potential, molecular weight, solution processability, and film microstructures are essential to their performance. Among the polymers, P(bgDPP-MeOT2) exhibited a figure-of-merit (μC*) of 225 F cm–1 V–1 s–1, over one order of magnitude higher than previously reported D-A polymers. Besides, the DPP polymers exhibited high hole mobility over 2 cm2 V−1 s−1, significantly higher than all D-A polymers employed in OECTs, leading to fast response OECTs with a record low turn-off response time of 30 μs. The polymer also exhibited better stability than polythiophene systems with current retention of 98.8% over 700 electrochemical switching cycles. This work provides a systematic solution to unleash the high-performance and fast-response nature of D-A polymers in OECTs.