Charge confinement in polythiophenes using m-phenylene as a molecular insulator

The oxidation state of the film of a series of the polymers, poly[m-phenylene-alt-oligothiophene]s has been analyzed by UV–VIS–Near-IR absorption spectroscopy. Since the m-phenylene insulator can confine various charge carriers within the quantum wells of the polythiophene backbone, the three charge carriers, i.e. polarons, π-dimers and bipolarons, are successively characterized with increasing applied voltage during electrooxidation. The energy of the polaron transitions linearly depends upon the inverse number of the thiophene rings between the consecutive m-phenylene rings.