Switching Response in Organic Electrochemical Transistors by Ionic Diffusion and Electronic Transport

Area of Science:

• Materials Science
• Condensed Matter Physics
• Organic Electronics

Background:

• Organic electrochemical transistors (OECTs) exhibit a switching response characterized by transient currents upon voltage perturbation.
• This phenomenon significantly influences OECT performance metrics, including equilibration times, scan rate-dependent hysteresis, and neuromorphic synaptic properties.

Purpose of the Study:

• To develop a comprehensive model unifying vertical ion diffusion and horizontal electronic transport for analyzing OECT time-dependent current responses.
• To classify the transient response to voltage pulses and associated hysteresis effects in OECT transfer curves.

Main Methods:

• Development of a physical analytical model.
• Advanced 2D drift-diffusion simulations.
• Experimental measurements on a poly(3-hexylthiophene) (P3HT) OECT.

Main Results:

• The general model is simplified into time-dependent equations describing ionic/hole concentration, yielding a Bernards-Malliaras conservation equation coupled with a diffusion equation.
• A classification of transient responses to voltage pulses is established.
• The study demonstrates that transient shapes are primarily governed by vertical ion diffusion or electronic current equilibration along the channel.

Conclusions:

• The unified model provides a robust framework for understanding the complex switching dynamics in OECTs.
• The findings offer insights into optimizing OECT performance for various applications, including neuromorphic computing.