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 TammDancoff 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 tripletsinglet 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 singlettriplet excitation with conventional time-dependent density functional theory. They are also more stable than those of ?-SCF, even if more sophisticated generalized gradient or hybrid functionals are used for the latter.