Proton Conduction in Hydrogen-Bonded Networks Enables High-Speed PEDOT:PSS Devices

The speed of organic mixed ionic-electronic conductors (OMIECs) is often attributed to ion size and diffusivity, yet many devices display kinetics that far exceed expectations. Here, we identify proton transport as the fundamental switching mechanism in PEDOT:PSS electrochemical random-access memories (ECRAMs) and demonstrate how ionic liquid chemistry dictates this process. Using isotope substitution, we show that fast kinetics arise from cooperative proton hopping through extended hydrogen-bond networks, and that the 2-position proton of the imidazolium ring plays a decisive role in conduction. Alkylation suppresses transport by limiting water uptake, while imidazole doping restores hydrogen-bond connectivity under rigorously anhydrous conditions, eliminating the reliance on trace water for ultrafast switching. By establishing how subtle molecular features of ionic liquids control proton conduction, this work provides a mechanistic basis for the anomalous speed of OMIEC devices and outlines a molecular design strategy for high-speed neuromorphic and electrochemical technologies.