| The organic electroluminescent (EL) material is the most critical fact of the organic electroluminescent light emitting devices (OLEDs), and the development of the emitting materials is imbalance. The green emitting material has achieved practical need, whereas the blue and red emitting materials-still remain numerous problems. Therefore, it is very important to design and synthesize novel blue and red phosphorescent materials with excellent performance to improve the performance of the organic electroluminescent phosphorescent light-emitting devices (PhOLEDs).In order to obtain excellent blue phosphorescent materials, a new type of cyclemetallic ligand9-(6-(4-phenyl-1H-1,2,3-triazol-1-yl)-hexyl-9H-carbazole (Czphtz) was synthesized from N-hexyl-carbazolyl modificated4-phenyl-1,2,3-triazole. The N-hexyl-carbazolyl moiety increased the solubility of the complexes and the molecular space steric hindrance, and further inhibited the triplet state-triplet state (T-T) exciton annihilation and concentration quenching effectively. Besides, the hole injection and transport ability of the complexes were improved, which enhanced the optical characteristics of the molecules.To adjust the emission wavelength of the complex, Czphtz was used as the main ligand, four auxiliary ligands based on2-(2H-1,2,4-triazole-3-yl)pyridine-(tfmptz, fpptz, tfmpptz and pptz) were applied to synthesis four iridium(III) complexes (Czphtz)2Ir(tfinptz),(Czphtz)2Ir(fpptz),(Czphtz)2Ir(tfmpptz) and (Czphtz)2Ir(pptz). The structures were characterized by proton nuclear magnetic resonance (’H NMR). The photophysical properties and energy-level structure of complexes were investigated by ultraviolet-visble absorption spectra, photoluminescence spectra, phosphorescence spectra, cyclic voltammetry curves and time-dependent density functional theory calculation.The electroluminescent properties of the devices containing (Czphtz)2Ir(tfmpptz) and (Czphtz)2Ir(pptz) were investigated. The results showed that the complexes had holetransporting and electron transporting abilities, and the carrier transmission performance was greatly improved. The maximum luminance was about1173.5cd/m2for the PhOLEDs containing (Czphtz)2Ir(tfmptz) as the emitting layer, the maximum current efficiency was about3.4cd/A, and the maximum power efficiency was1.52lm/W. The PhOLEDs containing (Czphtz)2Ir(pptz)-doped in4,4’-biscarbazolylbiphenyl (CBP) as the emitting layer, exhibited the maximum luminance of1743cd/m2, the maximum current efficiency of2.9cd/A, and the maximum power efficiency of0.95lm/W. The "roll-off" phenomenonof the device was slightly serious, implyingthat the concentration quenching of the molecules was not effectively suppressed. Thus, the Ir complexes are potential blue phosphorescent materials, undoped PhOLEDs could be produced when the concentration quenching was effectively suppressed by further adjustment of the molecular structures.To obtain excellent red phosphorescent material, in this paper, a novel red emitting iridium(III) complex (ppz)2Ir(piq)(ppz=1-phenylpyrazole, piq=1-phenylisoquinoline) was proposed. Compared to the deep blue phosphorescent complexes Ir(ppz)3(nonluminous at room temperature), the introduction of the piq ligand with strong electron affinity made the emission spectrum red-shifted to red-light area. The photophysical properties and energy-level structure of complex were investigated by ultraviolet-visble absorption spectra, photoluminescence spectra, cyclic voltammetry curves and time-dependent density functional theory calculation. The electroluminescent properties of the devices based on (ppz)2Ir(piq)-doped in CBP as the emitting layer exhibited an electroluminescence maximum at616nm, an optimized doping concentration of8-12wt%, a maximum current efficiency of about10cd/A, a maximum power efficiency of4.44lm/W and CIE of (0.65,0.35). This investigation provides an important experimental basis for the application of (ppz)2Ir(piq) as a potential red phosphorescent material in organic electroluminescent devices. |
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