Localization of electronic excitations in conjugated polymers studied by DFT

We present an extensive density functional theory (DFT) study on the neutral and charged electronic excitations in oligophenylene vinylenes including lowest singlet (S₁) and triplet (T₁) excitons and positive (P⁺) and negative (P^-) polarons. We investigated the vibrational and electronic properties of molecules using five different DFT functionals from pure GGA to long-range-corrected hybrids and found an explicit correlation between the spatial extent of the state and the fraction of the orbital exchange. While solvent effects are found to be negligible for neutral (S₁ and T₁) excitons, they play an important role for charged (P⁺ and P^-) species. S₁ states are observed to be spatially less localized compared to the polaronic wave functions (P⁺ and P^-). This is in contrast to the T₁ states, which exhibit more spatial confinement in comparison to P⁺ and P^- states.