Phosphorescence energies of organic light-emitting diodes from spin-flip Tamm-Dancoff approximation time-dependent density functional theory.

The phosphorescence energy in organometallic transition-metal compounds relevant for organic light-emitting diodes is calculated using spin-flip time-dependent density functional theory within the Tamm-Dancoff approximation, a technique presented by Wang and Ziegler. This method is implemented in the TURBOMOLE program suite by modifications of the present code. The predictions of the triplet-singlet transition energies with the spin-flip approach using functionals of the local density approximation are significantly more stable than those obtained from the indirect calculation as singlet-triplet excitation with conventional time-dependent density functional theory. They are also more stable than those of Δ-SCF, even if more sophisticated generalized gradient or hybrid functionals are used for the latter.