Fast synthesis of iridium(III) complexes with sulfur containing ancillary ligand for high-performance green OLEDs with EQE over 31%
Three green iridium(III) cyclometalated complexes, (4tfmppy)2Ir(dipdtc), (24btfmppy)2Ir(dipdtc) and (TN4T)2Ir(dipdtc), with the sulfur containing ancillary ligand of N,N-diisopropyldithiocarbamate (dipdtc) were synthesized for fifteen minutes at room temperature. The emission colours (peak = 497 - 534 nm) and photoluminescence quantum efficiencies (P = 71.6% - 94.2%) can be effectively regulated by introducing different main ligands of 2-(4-(trifluoromethyl)phenyl)pyridine (4tfmppy), 2-(2,4-bis(trifluoromethyl)phenyl)pyridine (24btfmppy) and 2',6'-bis(trifluoromethyl)-2,4'-bipyridine (TN4T), respectively. Employing these complexes as emitters, the organic light emitting diodes (OLEDs) with double-emitting layers were fabricated. Particularly, the device based on complex (TN4T)2Ir(dipdtc) showed superior performances with a maximum current efficiency of 86.59 cd A-1 and a maximum external quantum efficiency of 31.24% with low efficiency roll-off. These results suggest that the Ir(III) complexes with the four-membered ring Ir-S-C-S backbone containing N,N-diisopropyldithiocarbamate have potential application in OLEDs.