Numerical Modeling of an Organic Electrochemical Transistor

Abstract

We develop a numerical model for the current-voltage characteristics of organic electrochemical transistors (OECTs) based on steady-state Poisson’s, Nernst’s and Nernst–Planck’s equations. The model starts with the doping–dedoping process depicted as a moving front, when the process at the electrolyte–polymer interface and gradually moves across the film. When the polymer reaches its final state, the electrical potential and charge density profiles largely depend on the way the cations behave during the process. One case is when cations are trapped at the polymer site where dedoping occurs. In this case, the moving front stops at a point that depends on the applied voltage; the higher the voltage, the closer the stopping point to the source electrode. Alternatively, when the cations are assumed to move freely in the polymer, the moving front eventually reaches the source electrode in all cases. In this second case, cations tend to accumulate near the source electrode, and most of the polymer is uniformly doped. The variation of the conductivity of the polymer film is then calculated by integrating the density of holes all over the film. Output and transfer curves of the OECT are obtained by integrating the gate voltage-dependent conductivity from source to drain.

High yield manufacturing of fully screen-printed organic electrochemical transistors

“…This allows for polarization of the gate and channel that causes charge accumulation/depletion of the channel, which is driven by the application of a gate-source voltage. OECTs were first introduced by Mark S. Wrighton in 1984 9 and were later, especially with the advent of poly(styrene sulfonate)-doped poly (3,4-ethylenedioxythiophene) (PEDOT:PSS) 10 , improved and further developed 8 . When complexed with PSS, PEDOT is oxidized and highly conducting 11 and may be switched to its semiconducting state when reduced to its neutral state via the exchange of cations.…”

Finding the equilibrium of organic electrochemical transistors

“…Some model relax the assumption of a direct proportionality between V GS − Φ(x) and p ion (x) and instead calculate the density of injected ions from basic drift-diffusion equations. For example, Shirinskaya et al 18 used a 1D numerical model to determine p ion (x) and hence the conductivity of the organic semiconductor as a function of position inside the transistor channel σ(x). Coppedè et al 19 proposed an analytical 1D solution for the ionic current injected into PEDOT: PSS under the assumption of a constant electric field inside the electrolyte.…”

Dynamic Model of the Short-Term Synaptic Behaviors of PEDOT-based Organic Electrochemical Transistors with Modified Shockley Equations

“…Shirinskaya et al described the doping–de-doping interface as the moving front, based on which a numerical model for the current–voltage characteristics of OECTs was developed. 43 Tybrandt et al proposed a time-dependent approach based on the drift–diffusion–Poisson equation and phase separation. Their model successfully describes the experimental data.…”