Optical investigations of the effect of solvent and thermal annealing on the optoelectronic properties of Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) films

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most promising conductingpolymers that can be used as transparent electrode or as buffer layer for organic electronic devices. However,whenused as an electrode, its conductivity has to be optimized either by the addition of solvents or by post-depositionprocessing. In thiswork,we investigate the effect of the addition of the polar solvent dimethylsulfoxide (DMSO) toan aqueous PEDOT:PSS solution on its optical and electrical properties by the implementation of the Drudemodelfor the analysis of themeasured pseudo-dielectric function by Spectroscopic Ellipsometry from the near infrared tothe visible–far ultraviolet spectral range. The results show that the addition of DMSO increases significantly thefilm conductivity, which reaches a maximum value at an optimum DMSO concentration as it has confirmed byexperimentally measured conductivity values. The post-deposition thermal annealing has been found to have asmaller effect on the film conductivity.