Ionic Liquid-Induced Inversion of the Humidity-Dependent Conductivity of Thin PEDOT:PSS Films

Area of Science:

• Materials Science
• Polymer Electronics
• Conducting Polymers

Background:

• Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a widely used conducting polymer.
• Its electronic properties are sensitive to environmental conditions like humidity.
• Understanding and mitigating humidity effects is crucial for device stability.

Purpose of the Study:

• To investigate the influence of humidity on the resistance of post-treated PEDOT:PSS films.
• To evaluate the effect of ethyl-3-methylimidazolium dicyanamide (EMIM DCA) post-treatment on PEDOT:PSS properties.
• To elucidate the mechanisms behind humidity-induced resistance changes.

Main Methods:

• Thin film preparation of PEDOT:PSS.
• Post-treatment with varying concentrations of EMIM DCA.
• Controlled humidity exposure and resistance measurements.
• In situ grazing-incidence small-angle X-ray scattering (GISAXS) for morphology analysis.
• Electrochemical impedance spectroscopy (EIS) for charge carrier analysis.

Main Results:

• Untreated PEDOT:PSS shows increased resistance with higher humidity.
• EMIM DCA post-treated samples exhibit decreased resistance at higher humidity.
• GISAXS reveals humidity-induced changes in PEDOT domain spacing affecting hole transport.
• EIS confirms the contribution of ionic charge carriers in treated films.

Conclusions:

• EMIM DCA post-treatment significantly alters the humidity response of PEDOT:PSS films.
• The study proposes a model for hole and cation transport influenced by humidity.
• This research offers insights into developing more stable organic electronic materials.