High Performance Solution-Processed Deep-Blue Phosphorescence Organic Light-Emitting Diodes with EQE Over 24% by Employing New Carbenic Ir(III) Complexes

Solution-processed phosphorescence organic light-emitting diodes (PHOLEDs) are an increasingly attractive option as compared with vacuum-processed PHOLEDs due to their lower costs, large areas, and flexible production. Currently, the majority of reported solution-processed PHOLEDs are produced using red and green triplet emitters. The earlier reports on blue solution-processed PHOLEDs describe poor Commission International de l'eclairage color coordinates (CIE(x, y)) and low external quantum efficiencies (EQEs). It is difficult to produce efficient solution-processed deep-blue PHOLEDs that meet high EQE and CIE y color coordinate <= 0.15 requirements. The authors design and synthesize three new carbenic homoleptic deep-blue emitting Ir(III) complexes for solution-processed PHOLEDs. The introduction of bulky tert-butyl and trifluoromethyl (-CF3) substituents at a suitable position on the benzylated pyridoimidazole moiety effectively improves solution-processed device performance without compromising CIE(x, y) color purity. The deep-blue PHOLEDs exhibit remarkable maximum EQE (EQE(max)) of 25.3% and excellent CIE(x, y) color of (0.16, 0.10) at a mer-Ir(ptbbp)(3) doping ratio of 50 wt%. In particular, deep-blue PHOLEDs containing mer-Ir(CF(3)pbp)(3) as dopant exhibit excellent CIE(x, y) color coordinates of (0.16, 0.05) and an EQE(max) of 21.2%. This is the first report of deep-blue solution-processed PHOLEDs containing carbene-based Ir(III) complexes with extremely high EQE values and CIE y coordinate requirement.