Triplet energies of π-conjugated polymers

We report time-dependent density functional theory calculations of singlet–triplet splittings (S0–T1) and triplet–triplet (T1–Tn) excitation energies of a range of conjugated polymers with relevance as light emitting diode materials. The errors obtained from the computed results are discussed in terms of maximum and mean deviation values in comparison with experimental data. The theoretical methodology shows in general a sufficient agreement to warrant its use for prediction of polymer (S0–T1) and (T0–T1) excitation energies. We confirm that spin contamination of the triplet state is not a serious problem when computing triplet–triplet spectra of organic oligomers.