Blue Light-Emitting Bisorthometalated Ir(III) Complex: Origin of Blue Emission and Application in Electrophosphorescent Devices

Abstract

Blue light-emitting bisorthometalated Ir(III) complex with substitutional pyridine and phosphine ligands has been studied. From quantum chemical calculation we suggest that the blue emission can be ascribed to the redistribution of the molecular orbitals after the phosphine ligand has been introduced. This result is not only helpful to investigate the emission mechanism of the Ir(III) complex but also is meaningful for the design of new luminescent materials based on organometallics. The electrophosphorescent polymer light-emitting diodes based on the Ir(III) complex have low turn-on voltages less than 4 V. The brightness and external quantum efficiency (EQE) for the single-layer device reaches 1190 cd/m2 at 12 V and 2.1% at a current density of 9.85 mA/ cm2, respectively. For the multilayer device, because of more balanced carrier injection, the external quantum efficiency reaches 4.0% at a current density of 3.3 mA/cm2.