Synthesis and Electroluminescent Properties of Red-Emitting Iridium Complexes Based on Benzofuran-Isoquinoline

Three red iridium complexes were designed and synthesized by employing 6-isopropyl-1-(5-methylbenzofuran-7-yl)isoquinoline, 6-cyclopentyl-1-(5-methylbenzofuran-7-yl)isoquinoline and 6-isobutyl-1-(5-methylbenzofuran-7-yl)isoquinoline as main ligands, respectively, and 3,7-diethyl-4,6-nonedione as the auxiliary ligand. Their photophysical, thermal and electrochemical properties were investigated. These complexes have higher photoluminescence quantum yields and shorter phosphorescent lifetime. Three organic electroluminescent devices with same structure were fabrication using the iridium complexes as emitters. They all exhibited red electroluminescent emission with peak values at 637, 635 and 636 nm, respectively and showed low turn-on voltages below 2.8 V. And the highest external quantum efficiency of three devices was 14.1%, 13.4% and 13.3%, the highest current efficiency was 7.0, 7.4 and 7.0 cd/A, and the highest power efficiency was 7.9, 8.3, and 7.8 lm/W, respectively. These data indicate that the three iridium complexes can be used as efficient red phosphorescent materials.