RAMAN STUDIES OF DOPED POLYTHIOPHENE AND THE RADICAL-CATION AND DICATION OF QUINQUETHIOPHENE

The near-infrared Raman and electronic absorption spectra of an as-polymerized BF4--doped polythiophene film have been measured and analyzed by referring to the data of the radical cation and dication of alpha-quinquethiophene, which are models of a positive polaron and a positive bipolaron, respectively. Similarities between the Raman spectrum of doped polythiophene and that of the radical cation suggest that the observed Raman bands of the doped polymer arise from positive polarons. It is shown that the two characteristic bands in the electronic absorption spectrum of the doped polymer are assignable to positive polarons.