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

• Published in: Chemical physics letters Vol. 838; p. 141080
• Main Authors: Chi, Hao-Yuan, Zhang, Yun-Kai, Ji, Ye, Sun, Yue, Li, Guang-Zhi, Zhu, Yu-Ying, Jiang, Lu, Xiao, Bo, Song, Ming-Xing, Li, Dong-Fei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2024
• Subjects: DFT; Efficiency roll-off; Ir(III) complexes; OLEDs; TD-DFT; DFT; OLEDs; Ir(III) complexes; Efficiency roll-off; TD-DFT
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2024.141080

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, 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 blue phosphorescence cannot satisfy to be used for the applications, since that a fast reduction in efficiency known as roll-off, however, occurs when the drive current increases, this leads to more power consumption.•Thus in this paper, in order to find a series of blue phosphorescence OLED materials with low efficiency roll-off characteristics, we theoretical design and investigate a series of Iridium complexes. 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.