Electron-Ion Coupling Breaks Energy Symmetry in Bistable Organic Electrochemical Transistors

TL;DR

This paper investigates how the interaction between the polymer semiconductor PEDOT:PSS and ionic liquids influences the bistable, non-volatile behavior of organic electrochemical transistors, revealing the electrolyte's role in charge dynamics and device performance.

Contribution

It uncovers the fundamental electron-ion coupling mechanisms that break energy symmetry, demonstrating how electrolyte interactions modify molecular order and energetics in OECTs.

Findings

Electrolyte modifies channel composition and molecular order.

Bistability arises from asymmetric doping/dedoping energetics.

Direct electron-ion interactions drive distinct charge pathways.

Abstract

Organic electrochemical transistors are extensively studied for applications ranging from bioelectronics to analog and neuromorphic computing. Despite significant advances, the fundamental interactions between the polymer semiconductor channel and the electrolyte, which critically determine the device performance, remain underexplored. Here, we examine the coupling between the benchmark semiconductor PEDOT:PSS and an ionic liquid to explain the bistable and non-volatile behavior observed in OECTs. Using X-ray scattering and spectroscopy techniques, we demonstrate how the electrolyte modifies the channel composition, enhances molecular order, and reshapes the energetic landscape. Notably, the observed bistability arises from asymmetric and path-dependent energetics during doping and dedoping, resulting in two distinct paths, driven by a direct interaction between the electronic and ionic charge carriers. These findings highlight the electrolyte's role in tuning charge carrier dynamics, positioning it as a powerful yet underutilized lever for enabling novel device functionalities.