First-principles simulations of exciton transfer between N-heterocyclic carbene iridium (III) complexes in blue organic light-emitting diodes

N-heterocyclic carbene (NHC) iridium (III) complexes are promising for the use as blue emitters in organic light-emitting diodes. Exciton transfer between such organometallic complexes is investigated using time-dependent density functional theory calculations. Casida's equation is solved to study absorption and emission of the neutral and charged complexes using the ORCA package. The Sternheimer equation implemented in the Octopus code is extended to take into account spin-orbit coupling and is applied to investigate triplet excitations. Real-time propagation as implemented in the Octopus code is used to simulate exciton dynamics in an emitter dimer and to extract the exciton coupling via explicit integration of transition densities.