Measurement Protocols for Reporting PEDOT Thin Film Conductivity and Optical Transmission: A Critical Survey

Abstract

PEDOT is one of the most frequently studied conducting polymers in literature but values for optical transmission and electrical conductivity vary greatly. Therefore measurement protocols are examined and insights are suggested into why the protocols themselves may lead to differences. Reported PEDOT conductivity is the result of contact and non‐contact film thickness and four‐point probe measurements. The soft nature of PEDOT implies that any contact method must be executed with extreme care as values of conductivity ranging from 780 to 2 775 S · cm−1 can be obtained. Similarly, variations in the optical minimum, maximum, and transmission range are found based on different switching voltage protocols. The results present here highlight the need for explicitly stating the measurement protocol used.magnified image

Growth of poly(3,4‐ethylenedioxythiophene) films prepared by base‐inhibited vapor phase polymerization

“…31 To estimate the reliability of R s measurements made with patterned ITO electrodes and two-point contacts, the R s values of the methanol-washed PEDOT films were also calculated using four-point probe measurements taken from the center of the film. Prior to the measurements, the polymer was carefully scraped from the edges of the PEDOT film to avoid PEDOT film contact with the ITO and resulting errors due to electrical conductance of ITO.…”

Partially sulfonated ethylene-vinyl alcohol copolymer as new substrate for 3,4-ethylenedioxythiophene vapor phase polymerization

“…This is probably due to the fact that, in the approximation of a homogeneous dispersion of PEDOT into the EVALS matrix, the conductivity was calculated by taking into account the whole sample thickness ( d = 3.5 µm). Indeed, the maximum surface conductivity of the EVALS32–PEDOT ( σ s ∼ 0.056 S) was comparable or higher than those measured on PEDOT films obtained by EDOT VPP performed directly on the oxidant layer …”

“…The ratio between the measured inner probe voltage ( V ) and the source DC current, passing through the outer probes ( I ), was directly given by a digital multimeter Keithley 2700 (four‐wire resistance mode). The conductivity of each sample was obtained according to the equation for thin films: where d is the thickness of the sample …”

“…where d is the thickness of the sample. 31 Three different measurements of V/I for each sample (three samples per each VPP time period) were carried out.…”

A Compact, Highly Efficient and Flexible Polymer Ultra-Wideband Antenna

“…To make the antenna flexible and lightweight, a PEDOT thin film and sticky tape have been selected as the conductor and substrate respectively. PEDOT is a stable conductive polymers and can be produced using commercial formulations with lowcost manufacturing techniques such as spin or spray coating and screen or inkjet printing [10]. While DC conductivities exceeding 3×10 5 S/m have been reported in the literature [11] for sub-micron thick PEDOT films, it has been proven very challenging to simultaneously achieve sufficient thickness and satisfactory conductivity to satisfy the requirements for microwave antenna applications.…”