ИСТИНА

Finding the best phosphorescent emitters for OLEDs in silico is an urgent problem. An ab initio simulation is performed for the low-lying excited states in the two cyclometallated iridium complexes. The energies of the ground and excited states are calculated using the XMCQDPT2/CASSCF approximation [1]. Two types of excited states are considered: metal-to-ligand charge transfer (MLCT) and ligand-centered (LC) ones. It is found that MLCT triplets have lower energies than LC triplets in both complexes, which explains their efficient phosphorescence. Spin-orbit coupling effects in MLCT states are taken into account using one-electron Breit–Pauli spin-orbit operator [2]. The spin-orbit splitting in the MLCT state and the radiative constants of phosphorescence are calculated. Therefore, the energy transfer pathways between the spin-mixed states in the complex are tracked and the emission efficiency of the complex is estimated.