Side-Chain Engineering Enabled Stretchable Indacenodithiophene-Based Polymers for High-Performance Organic Electrochemical Transistors

Abstract

The combination of mechanical and electrical properties in organic mixed ion-electron conductors (OMIECs) is crucial for their application in flexible, stretchable organic electrochemical transistors (OECT) intended for biological use. However, research on the simultaneous regulation of both the mechanical and electrical properties of OMIECs remains limited. In this work, poly[indacenodithiophene-alt-3,3'-dimethoxy-2,2'-bithiophene] (IDT-OTOT) based polymers were designed to finetune the balance between their mechanical and electrical properties by varying the ratios of ethylene glycol to alkyl side chains (from 100% to 50%). Our findings indicate that when the ratio of ethylene glycol to alkyl side chains was reduced to 80%, the resulting polymer P80-gIDT-OTOT exhibited superior stretchability as well as an enhanced product of the charge carrier mobility and volumetric capacitance (μC*), along with improved device stability compared to other counterparts. The OECTs utilizing P80-gIDT-OTOT demonstrated outstanding performance and remarkable stability. Furthermore, OECTs constructed with stretched P80-gIDT-OTOT exhibited strain-independent characteristics within a stretching range of 10–50%, highlighting its excellent mechanical properties. This work establishes a structure-property relationship between side chains and the mechanical and electrical properties of OMIECs, which will be beneficial for advancing next-generation flexible and wearable bioelectronics.

Keywords

Organic mixed ion-electron conductors / Side-chain engineering / Indacenodithiophene-based polymers / Mechanical-electrical properties / Organic electrochemical transistors / Stability / Stretchability

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