Real space analysis of the nonlocal optical response of PPV oligomers

Abstract

We investigate the linear optical polarizabilities of poly(p-phenylene vinylene) oligomers using the time dependent Hartree Fock procedure. Our analysis is based on the computation of a nonlocal response function, which describes the effects of an interaction with the electromagnetic field at one carbon atom on the distribution of charges at other atoms. This provides physical insight into intramolecular charge dynamics and the anisotropic tensorial properties of the linear polarizabilities. The results are analyzed using the coupled electronic oscillator (CEO) representation, which allows the assignment of absorption peaks to distinct transitions between Hartree Fock orbitals. The size dependence of the linear absorption shows that at 10 repeat units the optical gap has almost converged to its infinite size value, and the oscillator strength of the lowest absorption line scales linearly with size. This implies that the sizes studied exceed the exciton coherence size and the resulting spectra should mimic the infinite size limit.