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Multiple time constant modelling of a printed conducting polymer electrode

Publication Type:

Journal Article

Source:

ELECTROCHIMICA ACTA, Volume 56, Number 13, p.4711-4716 (2011)

Keywords:

Poly(3; 4-ethylenedioxythiophene)/poly(styrene-4-sulfonate) (PEDOT:PSS); EIS (electrochemical impedance spectroscopy); CPE (constant phase element); Inkjet; Supercapacitor; RC transmission line; Electrochemical double layer capacitor

Abstract:

Constant phase elements (CPE) are routinely used to describe the
frequency response of electrochemical systems. However, this approach is
often scientifically unsatisfactory because the physical origin of the
phase is unclear. Here we observe CPE-like behaviour in a conducting
polymer
poly(3,4-ethylenedioxythiophene)/poly(styrene-4-sulfonate)(PEDOT:PSS)
film that was inkjet printed onto paper to form a flexible
electrochemical double layer capacitor electrode. We show that the
response of the electrochemically active film can also be described
using a physical model with multiple parallel finite RC
(resistor-capacitor) transmission lines whose lengths and time constants
are determined by the distribution of the measured film thickness. The
modeled volumetric capacitance and ionic conductivity match those
determined experimentally, suggesting that the physical origin of the
constant phase response is a distribution of mass transport limited time
constants. (C) 2011 Elsevier Ltd. All rights reserved.