Samsung Advanced Institute of Technology

Achieving large external quantum efficiencies, narrow bandwidths, and a long operational lifetime at high brightness remains the largest hurdle to developing organic blue-emitting devices. In this research, we demonstrate a materials strategy that can meet these conditions. The strategy is based on linear heteroleptic Au(I) complex exciton harvesters and multi-resonance thermally activated delayed fluorescence emitters. Our organic electroluminescence devices produce blue emission with Commission Internationale de l'？clairage chromaticity coordinates of (0.108, 0.160), a narrow full-width at half-maximum value of 20 nm, and a maximum external quantum efficiency (EQE) as high as 30.2％. Notably, the EQE value remains 22.2％ at 2000 cd m^-2, whereas conventional control devices with an organic exciton harvester suffer from huge roll-offs in quantum efficiency. An additional benefit of our device is a one-order-of-magnitude improvement in its operational lifetime compared with that of the control device. The effectiveness of using Au(I) complex exciton harvesters is further demonstrated for green-emissive electroluminescence devices. Our investigations reveal that the improvements are attributable to the unique ability of the Au(I) complexes for ultrafast triplet exciton harvest. In addition, the Au(I) complexes can facilitate resonance energy transfer to the fluorescence emitter, with effective suppression of hazardous triplet-triplet Dexter energy transfer. We believe that our research will be helpful in commercializing high-efficiency and stable blue electroluminescence devices.