ABSTRACT We report a comprehensive spectroscopic investigation of poly3,4‐ethylenedioxythiophene (PEDOT) thin films, including both those synthesized from solution in the doped state and from commercial PEDOT:PSS (poly(styrene sulfonate)) formulations. Variable‐angle spectroscopic ellipsometry is combined with transmittance and reflectance measurements spanning the UV to mid‐infrared spectral range. Data from the different techniques are consistently analyzed within a unified framework based on the complex dielectric function of each film. Uniaxial optical modeling assuming an edge‐on molecular orientation reveals a markedly anisotropic response, with the ordinary (in‐plane) component exhibiting significantly higher conductivity than the out‐of‐plane dielectric component. Notably, the synthesized PEDOT films show enhanced in‐plane optical conductivity, in agreement with sheet resistance measurements. The molecular structure and anisotropy of PEDOT are further corroborated by grazing‐incidence wide‐angle X‐ray scattering (GIWAXS), which reveals an intra‐lamellar structure characterized by π–π stacking of PEDOT chains at a distance of approximately 3.9 Å and an interlamellar periodicity of about 15.7 Å. Overall, these results represent a significant step toward a deeper understanding of the electronic and optical properties of this distinctive class of macromolecules and their potential use in photonics and optical metamaterials.
Bisio et al. (Mon,) studied this question.