Raman spectroscopy and DFT calculations of PEDOT:PSS in a dipolar field

Abstract

The conductive polymer–electrolyte interface plays an important role in many electrochemical devices. An unusual situation arises when a solvent-free ionic liquid (SF-IL) is used as the electrolyte because it behaves as a molten salt rather than an electrolyte solution. On the basis of Raman spectra, it was found that the presence of ion pairs of SF-IL in the vicinity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) results in a decrease in the oxidation level of the polymer and an increase in the HOMO–LUMO gap. The process of polymer “dedoping” and the modification of the electronic structure of the polymer are illustrated by quantum chemical calculations.