Selenophene Substitution Enabled High‐Performance n‐Type Polymeric Mixed Ionic‐Electronic Conductors for Organic Electrochemical Transistors and Glucose Sensors

Abstract High‐performance n‐type polymeric mixed ionic‐electronic conductors (PMIECs) are essential for realizing organic electrochemical transistors (OECTs)‐based low‐power complementary circuits and biosensors, but their development still remains a great challenge. Herein, by devising two novel n‐type polymers (f‐BTI2g‐SVSCN and f‐BSeI2g‐SVSCN) containing varying selenophene contents together with their thiophene‐based counterpart as the control, it is demonstrated that gradually increasing selenophene loading in polymer backbones can simultaneously yield lowered lowest unoccupied molecular orbital levels, boosted charge‐transport properties, and improved ion‐uptake capabilities. Therefore, a remarkable volumetric capacitance (C*) of 387.2 F cm⁻³ and a state‐of‐the‐art OECT electron mobility (µ_e,OECT) of 0.48 cm² V⁻¹ s⁻¹ are synchronously achieved for f‐BSeI2g‐SVSCN having the highest selenophene content, yielding an unprecedented geometry‐normalized transconductance (g_m,norm) of 71.4 S cm⁻¹ and record figure of merit (µC*) value of 191.2 F cm⁻¹ V⁻¹ s⁻¹ for n‐type OECTs. Thanks to such excellent performance of f‐BSeI2g‐SVSCN‐based OECTs, a glucose sensor with a remarkably low detection limit of 10 nMm and decent selectivity is further implemented, demonstrating the power of selenophene substitution strategy in enabling high‐performance n‐type PMIECs for biosensing applications.