Theoretical investigation of the electronic structure and photophysical properties of a series of mixed-carbene cyclometalated iridium(III) complexes with different ancillary ligands applied in phosphorescent organic light-emitting diodes

By using density functional theory and time-dependent density functional theory, the geometrical structure, electronic structure and photophysical properties of a series of mixed-carbene cyclometalated iridium(III) complexes with different ancillary ligands have been explored. The frontier molecular orbital components and energy levels for all studied complexes have been investigated. The lowest-lying absorptions were calculated as 327, 322, 333, 332 and 332 nm for these complexes, which have a HOMO → LUMO transition configuration. The lowest energy emissions for these complexes are localized at 413, 399, 498, 418 and 415 nm, respectively, simulated in a CH2Cl2 medium at the M062X level. One designed complex possessed the largest radiative decay rate (kr) value and could be a candidate for blue emitters in organic light-emitting diodes. This theoretical study can provide useful guidance for the design and synthesis of new iridium(III) complexes in phosphorescent materials.