Theoretical study on a series of iridium(III) complexes with low-efficiency roll-off properties for application in OLEDs

To find a series of suitable materials for phosphorescent organic light-emitting diodes (OLEDs), in this paper, we design six phosphorescent Ir(III) complexes that have low-efficiency roll-off properties. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to study the properties of (1-methyl-3-phenyl-2H-1λ^4,3λ^4-benzodiazole [dfbmb])2Ir(acetylacetonate [acac]), (dfbmb)2Ir(picolinate [pic]), (dfbmb)2Ir((Z)-5-tert-butyl-N'-(trifluoroethanimidoyl)pyridine-2-carboximidamide [tptz]), (1-(4-fluorophenyl)-3-methyl-2H-1λ^4,3λ^4-benzodiazole [F-dfbmb])2Ir(acac), (F-dfbmb)2Ir(pic), and (F-dfbmb)2Ir(tptz). Here, the main ligands are dfbmb and F-dfbmb, while the auxiliary ligands are acac, pic, and tptz. The advantages of these complexes were analyzed in terms of electronic structure, frontier molecular orbital (FMO) properties, spectral properties, electron affinities, ionization potentials, and OLED display effect. We hope that our research will contribute to the development of the OLED industry.