Interchain Electronic Excitations in Poly(phenylenevinylene) (PPV) Aggregates

Abstract

The semiempirical collective electronic oscillators (CEO) approach based on a time-dependent Hartree−Fock approximation is applied to analyze formation of interchain electronic excitations in PPV aggregates composed of two weakly coupled chain segments. Real-space analysis of transition density matrices identifies the origins of electron−hole pairs created upon optical excitation. The singlet intrachain excitons are delocalized along the whole oligomer chain and manifest themselves as strong band edge transitions in the linear spectra. New low-frequency interchain electronic excitations appear upon bringing oligomer chains into close proximity (3−4 Å). These new electronic states localized at the near-contact have no signatures in linear absorption. We argue that they may significantly decrease luminescence quantum efficiency of polymer films.