Greenish yellow organic light emitting devices based on novel iridium complexes containing 2-cyclohexenyl-1-phenyl-1H-benzo[d]imidazole

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 (η_c) 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.