Side-Chain-Based Cross-Linking of Amorphous Iono-Electronic Conductive Polymers for Thermo-Chemical Stability in Electrochemical Devices

Abstract

Robust electrochemical modulation and environmental stability remain difficult to co-optimize with performance in organic semiconductors. Using a poly (propylenedioxythiophene) (ProDOT)-based polymer as an amorphous model conductor, we show that carbene-enabled and selective formation of covalent linkages between side-chains enhances thermo-chemical robustness while optimizing device performance. While pristine films of ProDOT degrade at ∼130 °C and dissolve in common solvents, cross-linked films retain physicochemical properties, redox activity, and stability (>2000 cycles) under such conditions. Upon cross-linking, mixed conduction follows a nonmonotonic, volcano-like profile, peaking at ∼6 wt % diazirine used as the cross-linker, where transconductance (g_m) is enhanced by ∼35-fold and remains stable under external stress when integrated in organic electrochemical transistors (OECTs). Implementation of cross-linked films in electrochemical random access memory (ECRAM) devices demonstrates a performance profile that uniquely combines analog metrics that are comparable to state-of-the-art─large dynamic range (>30×), robust write/erase endurance (>120,000 pulses), high linearity, and training accuracy (>90%)─with thermo-chemical robustness under harsh conditions, which has been a longstanding bottleneck for the applicability of organic semiconductors in scalable manufacturing. This side-chain-based cross-linking is a versatile strategy to impart robustness and enable facile postsynthetic tuning of mixed conduction, especially for amorphous semiconducting polymers, unlocking their practical use in next-generation iono-electronic and computing hardware.