Improved organic electrochemical transistor stability using solvent degassing and chemical doping

Abstract

Organic mixed ionic–electronic conductors (OMIECs), which can be used to build organic electrochemical transistors (OECTs), are of potential use in flexible, large-area and bioelectronic systems. Although hole-transporting p-type OMIECs are susceptible to oxidation, and oxygen leads to OECT instability, it is unclear whether oxygen also behaves as an uncontrolled p-dopant. We show that oxygen dissolved in a solvent can act as a p-dopant in OMIECs and OECTs by filling traps to enable effective electrochemical doping. To address the fact that the presence of oxygen simultaneously jeopardizes OECT stability, we develop a two-step strategy in which we first degas the solvent, and then dope the OMIEC in a controlled manner using a chemical dopant. Our approach improves the stability of both p-type and n-type OECTs, while increasing the on–off ratio, tuning the threshold voltage and enhancing the transconductance, charge carrier mobility, and the µC* product—that is, the product of mobility and the volumetric capacitance. The stability and performance of organic electrochemical transistors can be improved using a two-step technique in which oxygen is first removed from the solvent and then a chemical dopant is introduced into the organic mixed ionic–electronic conductor.