Unraveling the Humidity Influence on the Electrical Properties of Ionic Liquid Posttreated Poly(3,4-ethylene dioxythiophene):Poly(styrenesulfonate) Films

The conductive polymer blend poly-(3,4-ethylene dioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS), popular for numerous organic applications, is investigated in terms of the influences that ionic liquid (IL) treatment and ambient humidity have on its conductivity properties. PEDOT:PSS thin films posttreated with different concentrations of the IL 1-ethyl-3-methylimidazolium dicyanamide (EMIM DCA) are exposed to different relative humidity (RH) steps from 0% RH up to 90% RH. Simultaneously, the film swelling and increase in the scattering length density (SLD), indicating a water uptake of the films, are monitored in situ with spectral reflectance (SR) and time-of-flight neutron reflectometry (ToF-NR). Additional in situ electrochemical impedance spectroscopy (EIS) shows that the pristine PEDOT:PSS has only an electronic conductivity, while for the IL-treated samples, an additional ionic conductivity contribution is observed. Upon humidity increase, the electronic conductivity of all PEDOT:PSS thin films decreases, while the ionic conductivity for IL posttreated thin films is enhanced by the intake of water molecules.

Automated summary

The conductivity properties of the conductive polymer blend PEDOT:PSS are investigated under the influences of ionic liquid treatment and ambient humidity. The results show that the ionic conductivity of the IL-treated PEDOT:PSS films is enhanced by the intake of water molecules, while the electronic conductivity of all PEDOT:PSS films decreases with increasing humidity.