Electronic absorption and Raman studies of BF4−-doped polythiophene based on the spectra of the radical cation and dication of α-sexithiophene

The electronic absorption and Raman spectra of as-polymerized BF4−-doped polythiophene have been analyzed on the basis of the spectra of the radical cation and dication of α-sexithiophene, viewed as models of a positive polaron and a positive bipolaron, respectively. The Raman spectra taken with laser lines between 632.8 and 1064 nm have been attributed to positive polarons existing in doped polythiophene. The Raman results confirm that the two-band feature observed in the electronic absorption spectra of doped polythiophene is attributable to polarons.