Investigation of Near Ohmic Behavior for Poly(3,4-ethylenedioxythiophene): A Model Consistent with Systematic Variations in Polymerization Conditions

Abstract

The impedance behavior of semiconducting polymer film electrodes based on poly(3,4-ethylenedioxythiophene) (PEDOT) in combination with a series of anionic dopants has been investigated using electrochemical impedance spectroscopy (EIS) over the frequency range from 0.1 Hz to 100 kHz. Films were electrodeposited on gold-coated Pt wire electrodes from a nonaqueous solution containing 3,4-ethylenedioxythiophene (EDOT). EIS results reveal that, under the optimal synthesis conditions, PEDOT electrodes consistently exhibit low, frequency-independent impedance over a wide frequency range (from ∼10 Hz to 100 kHz). These results suggest that the behavior originates from the two-layer homogeneous morphology of the film. A model for conduction in the films that is supported by experimental evidence is proposed, and EIS data for electrodes produced under a variety of electropolymerization conditions are presented.