A promising phosphorescent heteroleptic iridium complex with carbazole-functionalized substituent: SYNTHESIS, photophysical and electroluminescent performances
Li X., Zang T., Yu L., Zhang D., Lu G., Chi H., Xiao G., Dong Y., Cui Z., Zhang Z., Hu Z.
A promising heteroleptic iridium complex with carbazole-functionalized substituent, i.e., (cbbt)2Ir(acac), in which cbbt was 2-(4-(4-(9H-carbazol-9-yl)butoxy)phenyl)benzo[d]thiazole and acac acetylacetonate, was designed, synthesized and structurally characterized. The complex emitted intensely orange phosphorescence upon photoexcitation with high luminescent quantum efficiency (0.30), short triplet lifetime (0.15 μs) and high decomposition temperature (310°C). The electronic properties of (cbbt)2Ir(acac) were also examined according to the density functional theory calculations. Organic light-emitting diodes using (cbbt) 2Ir(acac) as doped emitter exhibited orange electrophosphorescence with prominent performances. An extremely high brightness of 17,910 cd m -2 at a high voltage (17 V) and a maximum luminance efficiency of 25.5 cd A-1 were achieved. More importantly, those devices exhibited low efficiency roll-off of 30-35% from 10 to 100 mA cm-2, which was probably attributed to the short triplet lifetime of (cbbt)2Ir(acac). © 2012 Elsevier B.V. All rights reserved.