Robust and flexible organic electrochemical transistors enabled by electropolymerized PEDOT

Organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene) (PEDOT) have been extensively studied, yet devices fabricated via electropolymerization remain underexplored in terms of the underlying ionic dynamics and the potential for flexible integration. In this work, we demonstrate robust OECTs based on electropolymerized PEDOT, exhibiting negligible drain current degradation after 1000 cycles of operation in aqueous NaCl. Compared to inkjet-printed devices, they offer markedly superior cycling stability, which is further enhanced by the incorporation of the small anionic dopant ClO₄ ^-. We also show flexible, lightweight OECTs by electropolymerizing PEDOT on ultrathin parylene substrates, achieving stable performance under mechanical strain. Furthermore, Electrochemical Quartz Crystal Microbalance with Dissipation (EQCM-D) analysis reveals distinct ion transport behavior in PEDOT:ClO₄, where dopant ejection dominates doping/dedoping process, unlike in PEDOT:PSS. This study underscores the advantages of electropolymerization and small-ion doping, offering new mechanistic insights and advancing the design of high-performance, flexible OECTs for bioelectronic applications.