A theoretical study of a series of iridium complexes with methyl or nitro-substituted 2-(4-fluorophenyl)pyridine ligands with the low-efficiency roll-off performance

A series of heteroleptic cyclometalated Ir (III) complexes, which are used for OLED application, were investigated by DFT and TD-DFT method. The frontier molecular orbital character and charge transfer character shown that they have the advantages of low efficiency roll-off properties, 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. [Display omitted] •Cyclometalated iridium (III) complexes have received special attention as dopants for harvesting the otherwise nonemissive triplet states formed in OLEDs, but now, most of them cannot satisfy to be used for the applications, especially for Bright blue and Near-infrared, since that a fast reduction in efficiency known as roll-off, however, occurs when the drive current increases, this leads to a much lower luminance and more power consumption.•Thus in this paper, in order to find a kind of Bright blue and Near-infrared OLED materials with low efficiency roll-off properties, we theoretical design and investigate a series of Iridium complexes.•The geometries, electronic structures, the lowest-lying singlet absorptions, triplet emissions properties and the application value for organic light emitting devices were all analyzed by theory in this article. A series metal iridium complexes were calculated using the method of DFT and TD-DFT under Gaussian 09 software. H atoms on the N counter in 2-(4-fluorophenyl)pyridine were replaced with methyl and nitro groups, respectively, to obtain two main ligands CFM(2-(4-fluorobrobenyl)-4-methylpyridine) and CFN(2-(4-fluorobrobenyl)-4-nitropyridine), then we obtained six complexes: (CFM)2Ir(acac), (CFM)2Ir(tpip), (CFM)3Ir, (CFN)2Ir(acac), (CFN)2Ir(tpip) and (CFN)3Ir, Where acac is represented as pentane-2, 4-dione, tpip as tetraphenylimido-diphosphinate. The electronic structure, the lowest singlet absorption, the triple excited states as well as the emission spectrum are also theoretically studied.