Iridium(III) complexes adopting thienylpyridine derivatives for yellow-to-deep red OLEDs with low efficiency roll-off. (March 2019)

• Record Type: Journal Article
• Authors: Niu, Zhi-Gang; Yan, Li-Ping; Wu, Lei; Chen, Guang-Ying; Sun, Wei; Liang, Xiao; Zheng, You-Xuan; Li, Gao-Nan; Zuo, Jing-Lin
• Is Part Of: Dyes and pigments. Volume 162(2019)
• Page Start: 863
• Page End: 871
• Publication Date: 2019-03
• Subjects: Iridium(III) complexes -- Thienylpyridine derivatives -- Tetraphenylimidodiphosphinate -- Organic light-emitting diode -- Low efficiency roll-off; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2018.11.017
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: By introduction of trifluoromethyl and phenyl groups to 2-(2-thienyl)pyridine (thp), four new phosphorescent bis-cyclometalated iridium(III) complexes, (thp)2 Ir(tpip), (cf3 thp)2 Ir(tpip), (cf3 btp)2 Ir(tpip) and (3-cf3 btp)2 Ir(tpip) (cf3 thp = 2-(thiophen-2-yl)-4-(trifluoromethyl)pyridine, cf3 btp = 2-(benzo[ b ]thiophen-2-yl)-4- (trifluoromethyl)pyridine, 3-cf3 btp = 2-(benzo[ b ]thiophen-3-yl)-4-(trifluoromethyl)pyridine, tpip = tetraphenylimidodiphosphinate), were synthesized and fully characterized. The density functional theory and time-dependent DFT calculations show that the frontier orbitals are mainly localized in the Ir(III) ion and the cyclometalated ligands. Thus, the photophysical properties were dominated by the cyclometalated C ∧ N ligand, attributed to 3 MLCT and 3 ILCT transition. These Ir(III) complexes emit in the yellow-to-deep red region with photoluminescence quantum yields in the range 40.5–86.4% in CH2 Cl2 solutions at 298 K. The organic light-emitting diodes (OLEDs) using (thp)2 Ir(tpip), (cf3 thp)2 Ir(tpip) and (cf3 btp)2 Ir(tpip) as yellow, orange and deep red emitters display good electroluminescent performance with low efficiency roll-off. Notably, the device based on (cf3 thp)2 Ir(tpip) possesses very high EL efficiencies with the maximum luminance efficiency and external quantum efficiency (EQE) of 53.9 cd A −1 and 17.9%, respectively. Furthermore, the EQE for this complex could be still retained as 15.4% at a luminance of 1000 cd m −2 . Graphical abstract: Highlights: Four new phosphorescent iridium(III) complexes based on thienylpyridine derivatives were synthesized. These iridium(III) complexes emit in the yellow-to-deep red region with photoluminescence quantum yields of 40.5–86.4%. The yellow-to-deep red OLEDs have good performance with low efficiency roll-off. The best device showed an EQEmax of 17.9%, and the EQE remained as 15.4% at a luminance of 1000 cd m −2 .