Dinuclear Ir(III) complexes with asymmetrical bridging ligands as highly efficient phosphors for single-layer electroluminescent devices
Dinuclear Ir(III) complexes are recently emerging with great promise for organic electroluminescent devices, owing to their unique merits such as increased spin-orbit coupling and adjustable photophysical properties. However, most of them need sophisticated doped processes for the engineering and result in high production cost. Herein, we developed novel dinuclear Ir(III) complexes, which become weakly phosphors in solutions but with intensified emission in solid state. The intermolecular interactions-caused quenching are suppressed perfectly and the carrier transport abilities are modulated simultaneously, leading to high emission efficiencies in neat film and balanced charge carrier transporting. Green-emitting single-layer nondoped device achieves promising efficiencies with external quantum efficiency (EQE) value of 11.6% and current efficiency (CE) value of 40.0 cd A−1. Orange-emitting device realizes EQE of 12.9% and CE of 38.4 cd A−1, which are the highest efficiencies for the solution-processed single-layer nondoped devices and even comparable to most of multilayer doping devices.