Strategy and Mechanism of Boosting Ion Penetration in Organic Electrochemical Transistors

Abstract Organic electrochemical transistors (OECTs) have emerged as promising platforms for bioelectronics and neuromorphic devices because of their unique ionic–electronic coupling. The key to unlocking high-performance operations lies in achieving rapid and efficient bulk doping, yet this remains critically hampered by limited ion accessibility, particularly within the hydrophobic bulk of organic mixed ionic–electronic conductors (OMIECs). This mini-review highlights recent molecular and processing engineering strategies to enhance ion penetration and ion–electron coupling in OECT channels. Molecular-level tuning, such as side-chain and backbone modulation, in addition to processing approaches, including the use of additives, dopants, cross-linked networks, solvent engineering, patterned transport architectures, and interface microstructure control, are discussed. Throughout, we place special emphasis on elucidating the complex relationships between molecular structure, processing-derived morphology, interfacial environments, and ion–transport dynamics, complemented by advanced characterization approaches that probe ion transport and its coupling with hydration and structural evolution. This holistic understanding is pivotal for rational performance optimization. Finally, we highlight emerging frontiers in advanced characterization, multiscale simulation, and data-driven design, which are expected to expedite the discovery of high-performance OMIECs and OECTs with balanced and enhanced mixed transport properties.