Theory of triplet exciton polarons and photoinduced absorption in conjugated polymers

Abstract

Triplet exciton polarons in nondegenerate conjugated polymers are studied theoretically. Both electron-electron and electron-lattice interactions are taken into account in the Pariser-Parr-Pople model. The electronic and lattice structures of exciton polarons and their adiabatic energy surfaces are calculated by means of the unrestricted Hartree-Fock and the single-configuration-interaction methods. The calculated absorption spectrum of a triplet exciton polaron explains well the photoinduced absorption (PA) spectrum observed in polydiaectylene. An excitonic effect turns out to be crucial in explaining the narrow-peak profile of the observed PA spectrum. The present theory may well apply to the similar PA observed in poly(p-phenylene vinylene).