Four-membered red iridium(iii) complexes with Ir–S–C–S structures for efficient organic light-emitting diodes

Abstract

Three sulfur atom containing ligands (diphenylcarbamodithioate (dpdtc), di-p-tolylcarbamodithioate (medtc) and bis(4-(trifluoromethyl)phenyl)carbamodithioate (cf3dtc)) were prepared for three red iridium(III) complexes. All (tfmpqz)₂Ir(dpdtc), (tfmpqz)₂Ir(medtc) and (tfmpqz)₂Ir(cf3dtc) complexes were synthesized rapidly at room temperature in 5 min with high yields owing to strong coordination ability between sulfur and iridium atoms, in which 4-(4-(trifluoromethyl)phenyl)quinazoline (tfmpqz) was used as the main ligand. Three Ir(III) complexes show distinct PL emissions in the range of 617–629 nm with a high phosphorescence quantum yields of up to 83%, respectively. With these complexes as dopants, the organic light-emitting devices (OLEDs) with the double-emissive-layer structure of ITO/HATCN (hexaazatriphenylenehexacabonitrile, 5 nm)/TAPC (bis(4-(N,N-ditolyl-amino)phenyl)cyclohexane, 30 nm)/Ir(III) complexes: TCTA (4,4′,4′′-tris(carbazol-9-yl)-triphenylamine) (12 wt%, 10 nm)/Ir(III) complexes: 26DCzppy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine) (12 wt%, 10 nm)/TmPyPB (1,3,5-tri((3-pyridyl)-phen-3-yl)benzene, 30 nm)/LiF (1 nm)/Al (100 nm) achieved good performances. In particular, the device employing the (tfmpqz)₂Ir(cf3dtc) complex exhibits champion performances with a maximum luminance of 30 740 cd m⁻² and a maximum external quantum efficiency of 26.10%, respectively.