A density functional theory study of phosphorescence and triplet–triplet absorption for nonlinear absorption chromophores

We report a systematic study of the nonlinear absorption characteristics of π-conjugated chromophores using density functional theory (DFT), namely, the prediction of singlet–triplet splittings (S0–T1), vertical triplet–triplet (T1–Tn) excitation energies, and corresponding oscillator strengths. This is a first application of DFT/time-dependent DFT to a broad range of π-conjugated test molecules for the prediction of the T1–Tn excitation energies and oscillator strengths and the S0–T1 energies, using Becke’s three-parameter hybrid functional. Our results show a good agreement with experimental excitation energies and oscillator strengths. The range of errors obtained from the computed results is discussed in detail.