An in situ Fourier-transform infrared study of the electroreduction of polybithiophene

In situ FTIR spectra have been acquired for n-doped polybithiophene (PBT) films on Pt as a function of electrode potential. The spectra are qualitatively similar to those of p-doped PBT: they show a broad electronic band in the near IR and enhanced ring vibration (IRAV) modes. The variation of IRAV band intensities with potential (doping level) can be explained using a model in which carrier–carrier interactions increase linearly with carrier density. This model allows correlation of IRAV and electronic band intensities for both p- and n-doped PBT. Optically determined microscopic conductivities for n-doped PBT are similar to those for p-doped PBT. We find evidence for solvent (acetonitrile) in two types of environment within the film, and observe changes in solvent population within the film via transient (un)doping experiments.