Fused Bithiophene Imide Dimer‐Based n‐Type Polymers for High‐Performance Organic Electrochemical Transistors

The development of n‐type organic electrochemical transistors (OECTs) lags far behind their p‐type counterparts. In order to address this dilemma, we report here two new fused bithiophene imide dimer (f‐BTI2)‐based n‐type polymers with a branched methyl end‐capped glycol side chain, which exhibit good solubility, low‐lying LUMO energy levels, favorable polymer chain orientation, and efficient ion transport property, thus yielding a remarkable OECT electron mobility (μe) of up to ≈10−2 cm2 V−1 s−1 and volumetric capacitance (C*) as high as 443 F cm−3, simultaneously. As a result, the f‐BTI2TEG‐FT‐based OECTs deliver a record‐high maximum geometry‐normalized transconductance of 4.60 S cm−1 and a maximum μC* product of 15.2 F cm−1 V−1 s−1. The μC* figure of merit is more than one order of magnitude higher than that of the state‐of‐the‐art n‐type OECTs. The emergence of f‐BTI2TEG‐FT brings a new paradigm for developing high‐performance n‐type polymers for low‐power OECT applications. Two fused bithiophene imide dimer‐based n‐type polymers bearing hydrophilic branched methyl end‐capped glycol side chains were developed, showing a high degree of backbone planarity, favorable polymer chain packing orientation, and substantial electrochemical doping efficiency. As a result, the f‐BTI2TEG‐FT‐based organic electrochemical transistors (OECTs) deliver a record‐high geometry‐normalized transconductance of 4.60 S cm−1.