High‐Performance n‐Type Polymeric Mixed Ionic‐Electronic Conductors: The Impacts of Halogen Functionalization

Abstract Developing high‐performance n‐type polymer mixed ionic‐electronic conductors (PMIECs) is a grand challenge, which largely determines their applications in vaious organic electronic devices, such as organic electrochemical transistors (OECTs) and organic thermoelectrics (OTEs). Herein, two halogen‐functionalized PMIECs f‐BTI2g‐TVTF and f‐BTI2g‐TVTCl built from fused bithiophene imide dimer (f‐BTI2) as the acceptor unit and halogenated thienylene–vinylene–thienylene (TVT) as the donor co‐unit are reported. Compared to the control polymer f‐BTI2g‐TVT, the fluorinated f‐BTI2g‐TVTF shows lower‐positioned lowest unoccupied molecular orbital (LUMO), improved charge transport property, and greater ion uptake capacity. Consequently, f‐BTI2g‐TVTF delivers a state‐of‐the‐art µC* of 90.2 F cm⁻¹ V⁻¹ s⁻¹ with a remarkable electron mobility of 0.41 cm² V⁻¹ s⁻¹ in OECTs and an excellent power factor of 64.2 µW m⁻¹ K⁻² in OTEs. An OECT‐based inverter amplifier is further demonstrated with voltage gain up to 148 V V⁻¹, which is among the highest values for OECT inverters. Such results shed light on the impacts of halogen atoms on developing high‐performing n‐type PMIECs.