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 abranched methyl end-capped glycol side chain, which exhibit good solubility,l ow-lying LUMO energy levels,f avorable polymer chain orientation, and efficient ion transport property, thus yielding aremarkable OECT electron mobility (m e )ofup to % 10 À2 cm 2 V À1 s À1 and volumetric capacitance (C*) as high as 443 Fcm À3 ,simultaneously.Asaresult, the f-BTI2TEG-FTbased OECTs deliver ar ecord-high maximum geometrynormalized transconductance of 4.60 Scm À1 and am aximum mC* product of 15.2 Fcm À1 V À1 s À1 .T he mC* figure of merit is more than one order of magnitude higher than that of the stateof-the-art n-type OECTs.T he emergence of f-BTI2TEG-FT brings an ew paradigm for developing high-performance ntype polymers for low-power OECT applications.

Scheme 1. Synthetic route to the fused bithiophene imide dimer-based n-type polymers f-BTI2g-TVT and f-BTI2g-TVTCN.

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 abranched methyl end-capped glycol side chain, which exhibit good solubility,l ow-lying LUMO energy levels,f avorable polymer chain orientation, and efficient ion transport property, thus yielding aremarkable OECT electron mobility (m e )ofup to % 10 À2 cm 2 V À1 s À1 and volumetric capacitance (C*) as high as 443 Fcm À3 ,simultaneously.Asaresult, the f-BTI2TEG-FTbased OECTs deliver ar ecord-high maximum geometrynormalized transconductance of 4.60 Scm À1 and am aximum mC* product of 15.2 Fcm À1 V À1 s À1 .T he mC* figure of merit is more than one order of magnitude higher than that of the stateof-the-art n-type OECTs.T he emergence of f-BTI2TEG-FT brings an ew paradigm for developing high-performance ntype polymers for low-power OECT applications.