Delayed cation dynamics enables dual-doped organic electrochemical transistors with high current sensitivity

The coupling between ionic and electronic species and their dynamic interplay lay the foundation for organic electrochemical transistors (OECTs) to transduce and amplify bio(chemical) signals through ion-modulated conductivity. However, the operation of most reported OECTs is typically dominated by single ions, e.g. anions for p-type accumulation devices, mainly due to the challenge of regulating ion dynamics to enable both types of ions to play a role during the electrochemical doping process. In this study, we propose that electrochemical doping of an OECT channel can occur via an anion-cation dual-doping mechanism, where cation expulsion and anion injection occur simultaneously. By designing a p-type organic mixed ionic-electronic conductor, Pu2gT, with strong side chain-cation interactions, we successfully decelerate the cation transport dynamics, allowing the dual-doping process to occur. As a result, Pu2gT OECT exhibits improved current sensitivity compared with the anion-dominated counterpart, showing potential in high-quality electrocardiogram signal acquisition and ion concentration discrimination. Furthermore, incorporating crown ether additives into Pu2gT enhances the dual-doping effect by further delaying cation dynamics, leading to even higher device performance. This dual-doping mechanism deepens the understanding of OECT working principles and opens avenues for achieving state-of-the-art bioelectronic devices.