Tuning the Organic Electrochemical Transistor (OECT) Threshold Voltage with Monomer Blends

Abstract A novel approach is introduced to modulate the threshold voltage of organic electrochemical transistors (OECTs) that are fabricated by electropolymerizing the channel material between the source and drain electrodes. To achieve this, we adjust the ratio of two water‐soluble tri‐thiophene monomers, which share the same backbone, but present either anionic or zwitterionic sidechains, during channel formation. This approach allows for a continuous modulation of both the electropolymerization onset potential and the native doping state of the film. We attribute the effect of monomer blends displaying properties that are a weighted average of their components to the formation of nanoscale monomer aggregates that have a uniform internal charge density. Through an investigation of monomer aggregation behavior, polymer film growth, and device properties of OECTs fabricated by electropolymerization, we highlight the importance of monomer aggregation in the electropolymerization of conducting polymers. The ability to tune both electropolymerization onset and the OECT threshold voltage has significant implications for the development of more complex circuits for integrated neuromorphic computing, biosensing, and bioelectronic systems.