The effects of sulfon on the structural and optical properties in the low-bandgap conjugated polymer poly (3,4-ethylenedioxythiophene)

The geometric and electronic structure of 3,4-ethylenedioxythiophene oligomers have been calculated with and ab initio Hartree–Fock (HF/6-31G) method. In order to understand the influence of oxidized sulfon units on the electronic structure and optical properties of PEDOT, different octamers, differing by the amount and position of the rings bearing a SO2 group, have been studied. The calculations indicate that the optical transitions are shifted, in the different oligomers containing the sulfon units, with respect to the pure PEDOT. These shifts are due to the charge transfer or the large twisting angles between the repeating units in the polymer