Addressing transconductance-bandwidth trade-off by three-dimensional electrolyte-surrounded organic electrochemical transistors.

The performance of organic electrochemical transistors (OECTs) is fundamentally constrained by a trade-off between transconductance and temporal response. While increasing channel thickness enhances its capacitance and thereby amplifies transconductance, it simultaneously impedes ion transport kinetics, leading to slower switching speeds. Here, we present a three-dimensional electrolyte-surrounded OECT architecture that redefines ion transport dynamics by enabling multidirectional ion doping to the channel for efficient and rapid switching. Our proposed approach achieves a remarkable enhancement in the operational bandwidth of OECTs, reaching 26 kHz while preserving their high transconductance, notably using a commercially available conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). This is enabled by micro/nanostructured channel design that enhances ion accessibility and minimizes parasitic effects. This advancement allows for continuous, wide-frequency neural signal recording from peripheral nerves. This work offers a robust strategy for achieving both high transconductance and fast switching in OECTs, establishing a foundation for the development of next-generation, high-speed bioelectronic interfaces.