Density functional theory and time-dependent density functional study a series of iridium complexes with low-efficiency roll-off properties

A series of blue phosphorescent heteroleptic cyclometalated Ir(III) complexes with mesitylphenyl-imidazole ligands for organic light-emitting devices have been theoretically studied. We want to find their electronic structures, spectroscopic properties, and application value for organic light-emitting devices. (fppz)2Ir(acac), (fppz)2Ir(tpip), (dfbdp)2Ir(fppz), (F-fppz)2Ir(acac), (F-fppz)2Ir(tpip), and (dfbdp)2Ir(F-fppz) are investigated with DFT and TD-DFT approaches, where, for (fppz)2Ir(acac), (fppz denotes 2-(5-(trifluoromethyl)-4H-pyrazol-3-yl)pyridine, and acac denotes acetylacetonate); for (fppz)2Ir(tpip), tpip denotes tetraphenylimido-diphosphinate; and, for (F-fppz)2Ir(acac) and (F-fppz)2Ir(tpip), F-fppz denotes 2-(5-fluoro-4H-pyrazol-3-yl)pyridine.