Design and synthesis of phosphorescent iridium containing dendrimers for potential applications in organic light-emitting diodes

Three phosphorescent dendrimers (IrC1, IrC3, and IrF2) with an iridium complex core and oligocarbazole or oligofluorene substituted ligands were synthesized and characterized. The structures of the oligocarbazole were designed to maintain high triplet energy of the ligands so that phosphorescence quenching in the resulting dendrimers can be prevented, while the oligofluorene in IrF2 resulted in undesired phosphorescence quenching. Best performance was obtained from an IrC3 based electro-phosphorescent light-emitting device with a maximum luminance of 13 060 cd center dot m(-2) at a driving voltage of 11.5 V and a peak current-efficiency of 4.3 cd center dot A(-1) at a luminance of 3 400 cd center dot m(-2), owing to its high PL efficiency, and efficient energy transfer between the iridium complex core and the ligands.