Backbone Engineering of Indacenodithiophene-Based Polymers for High-Performance Vertical Organic Electrochemical Transistors and Efficient Glucose Sensor

Organic mixed ionic-electronic conductors (OMIECs) play a fundamental role in the performance of organic electrochemical transistors (OECTs) and their applications. Although several depletion mode and accumulation mode OMIECs have been utilized for efficient OECT-based glucose sensors, there are still persistent drawbacks such as including biocompatibility, instability, or high detection limits. In this work, a series of indacenodithiophene-based polymeric OMIECs (gIDT, gIDT–T, and gIDT–DTBT) are developed, where the influences of backbone structure on their optical bandgap, energy level, electrochemical propriety, charge transfer and transistor performance, are systematically investigated. By applying KPF₆ electrolyte and vertical device structure, gIDT–DTBT-based vertical OECTs (vOECTs) achieved a maximum output current of –15.63 mA, a maximum transconductance of 39.99 mS, and stable output current (less than ∼2% decay) over 1000 switching cycles. In addition, such vOECTs are employed to detect glucose concentrations ranging from 0.9 to 22.5 μM. A low limit of detection (0.1 μM) and good selectivity are demonstrated. This study indicates that the combination of regulating OMIECs’ backbone structure, selecting appropriate electrolytes, and implementing a vertical device structure can help optimize OECT performance and its biosensor applications.