2-Cyclohexenyl-1-phenyl-1H-benzo[d]imidazole (Hcyclopbi) and its heterocyclometalated iridium complexes bis[2-cyclohexenyl-1-phenyl-1H-benzo[d] imidazole](acetylacetonate)iridium(III) [(cyclopbi)2Iracac] and bis[2-cyclohexenyl-1-phenyl-1H-benzo[d]imidazole][2-(3-(trifluoromethyl) -1H-pyrazol-5-yl)pyridinate]iridium(III) [(cyclopbi)2IrCF 3] were firstly designed and synthesized. Owing to the strong electron withdrawing ability of 2-(3-(trifluoromethyl)-1H-pyrazol) compared to that of acetylacetonate, blue shifted phosphorescence 542 nm was obtained for (cyclopbi)2IrCF3 compared to that of (cyclopbi) 2Iracac 545 nm with photoluminescence quantum yields (φ) 0.22 and 0.25, respectively, as well the highest occupied molecular orbit (HOMO) energy level was estimated to be -5.10 eV for (cyclopbi)2IrCF3, 0.19 eV lower than that of -4.91 eV for (cyclopbi)2Iracac. When (cyclopbi)2Iracac was doped into 4,4′-bis(9H-carbazol-9-yl) biphenyl (CBP) as the emitting layer, high efficiency organic light emitting devices (OLEDs) were obtained with maximum current efficiency (ηc) 22.3 cd/A at 3.1 mA/cm2 and maximum brightness 16,300 cd/m2 at 171.6 mA/cm2, which were comparable to those of bis(2-phenylpyridine)(acetylacetonate)iridium(III) [(ppy) 2Iracac] with the same device structure. This results indicate that (cyclopbi)2Iracac and (cyclopbi)2IrCF3 are potential phosphorescent dyes used for OLEDs.
Bibliographical noteFunding Information:
This work was supported by Outstanding Young Scientists Research Award Fund of Shandong Province ( BS2010NJ021 ), Shandong Provincial Natural Science Foundation ( ZR2011BZ007 ), Qingdao Municipal Science and Technology Program (11-2-4-22-hz), and State Key Laboratory of Luminescent Materials and Devices (South China University of Technology) . We thank Dr. Xiao Li and Haijun Chi for the NMR analysis in University of Science and Technology Liaoning.
- Greenish yellow phosphorescence
- Heterocyclometalated iridium complexes
- Organic light emitting devices
ASJC Scopus subject areas
- Chemical Engineering(all)
- Process Chemistry and Technology