Theoretical study of blue-green iridium(III) complexes with low-efficiency roll-off properties for application in phosphorescent organic light-emitting diodes

To find an array of suitable materials for phosphorescent organic light-emitting diodes (OLEDs), in this paper, we design six blue-green phosphorescent Ir (III) complexes that have low-efficiency roll-off properties. Density functional theory and time-dependent density functional theory were used to study the properties of (2-[4-phenoxyphenyl]pyridine [oppy])2Ir(acetylacetonate [acac]), (oppy)2Ir(picolinate [pic]), (oppy)2Ir(tetraphenylimido-diphosphinate [tpip]), (5-fluoro-2-(4-phenoxyphenyl)pyridine [F-oppy])2Ir(acac), (F-oppy)2Ir(pic), and (F-oppy)2Ir(tpip). Here, the main ligands are oppy and F-oppy, while the auxiliary ligands are acac, pic, and tpip. The advantages of these complexes were analyzed in terms of electronic structure, frontier molecular orbital properties, spectral properties, and OLED display effect. We hope that our research will contribute to the development of the OLED industry. A series of heteroleptic cyclometalated Ir (III) complexes, which are used for OLED application, were investigated by DFT and TD-DFT methods. The frontier molecular orbital character and charge-transfer character shown that they have the advantages of low-efficiency roll-off, which is a "stumbling block" in the process of OLED solid-lighting's development. Namely, means the materials will play an important role in the journey development of OLED.image