Lattice dynamics and vibrational spectra of polythiophene. II. Effective coordinate theory, doping induced, and photoexcited spectra

Abstract

It is shown that the infrared and Raman spectra of polythiophene, pristine, doped or photoexcited as well as the spectra of the oligomers pristine and doped are accounted for by the effective conjugation coordinate theory. An effective conjugation force constant associated with the delocalization of the π electrons is measured. It is proven that delocalization extends at least over five thiophene rings and that the samples of the polymer consist of a distribution of conjugation lengths with a confinement length of at least five thiophene rings. The infrared spectrum of the doped and photoexcited polymer is consistent with the existence of a bipolaronic conjugational defect confined within ∼5 thiophene rings.