Spectroscopic ellipsometry Investigation of PEDOT:PSS films in water and air ambient

Conducting polyplex poly(3, 4-ethylenedioxythiophene) : polystyrene sulfonate (PEDOT:PSS) is an interesting polymer material with a potential to be used in bio-electronic devices. However, the conduction mechanism of these films is not sufficiently understood, particularly when the film is in contact with water. We report variable angle spectroscopic ellipsometry(VASE) measurements, which were performed with a goal to determine the electrodynamic properties of the films under observation. The optical model based on Fresnel’s equations in combination with an electrodynamic model enables the fitting of complex dielectric function from the measured ellipsometric angles psi and delta. The measurements were performed for various film thicknesses and under varied ambient conditions (water/air). The applied model fits the data with sufficient accuracy and the electrodynamic parameters and thickness obtained by fitting falls within reasonable range of values.