An easy to implement strategy for improving organic electrochemical transistor stability: combining chemical doping with solvent degassing

Although p-type organic mixed ionic electronic conductors (OMIECs) are susceptible to oxidation, it has not yet been considered as to whether oxygen could behave as an uncontrolled p-dopant. Here, oxygen dissolved in solvents is shown to be behave as a p-dopant, that fills traps to enable more effective electrochemical doping in OMIECs and organic electrochemical transistors (OECTs). Yet the presence of oxygen is also known to jeopardize OECT stability. A two-step strategy is introduced to solve this contradictory problem, where first the solvent is degassed, and second the OMIEC is doped in a controlled manner using a chemical dopant. This strategy increases on-off ratio, tunes the threshold voltage, and enhances the transconductance, mobility and the µC* product, while having a remarkable impact on both p-type and n-type OECT stability. This simple solution-processing technique is easily implemented, low-cost, and highly effective in an oxygen-rich environment. The data herein suggests that combining chemical doping with solvent degassing could be a broadly applicable technique to improve essential criteria needed to realize organic bioelectronics and more complex OMIEC circuitry