Regulating morphology of high-performance organic electrochemical transistors through a dual-solvent blade-coating strategy

Organic electrochemical transistors (OECTs) have emerged as promising candidates for bioelectronics because of their efficient ionic‒electronic coupling. However, the realization of balanced ionic‒electronic transport with satisfactory stability is challenging. Herein, we report a dual-solvent-assisted blade-coating strategy to modulate the morphology of hydrophilic ethylene glycol-grafted polythiophene films. The effects of the film thickness and crystallinity on OECT performance are systematically investigated. The well-ordered and uniform edge-on morphology achieved with the dual-solvent system facilitates efficient charge transport without impeding ion penetration, leading to efficient mixed ionic‒electronic transport. More importantly, the operational stability is substantially enhanced compared with films processed using a single solvent, such that even thin films with thicknesses below 20 nm maintain more than 90% of their on-current after thousands of operational cycles. The optimized OECTs are successfully demonstrated for ECG (electrocardiogram) monitoring. This study provides an effective morphology engineering strategy for high-performance OECTs in wearable bioelectronics.