Bulk Passivation Enables Hundredfold Enhanced Electroluminescence of Monophosphine Cu4I4 Cubes.

Electroluminescent (EL) clusters emerged rapidly, owing to their organic-inorganic hybrid feature for comprehensive performance integration and potential for large-scale display and lighting applications. However, despite their good photoluminescent (PL) properties, until present no efficient EL monodentate ligand based clusters were reported, due to structural variation during processing and excitation and exciton confinement on cluster-centered quenching states. Here we demonstrate an effective "bulky passivation" strategy for efficient cluster light-emitting diodes with a monophosphine Cu4I4 cube named [TMeOPP]4Cu4I4. With terminal pyridine groups, an "active" matrix named TmPyPB supports effective host-cluster interplays for configuration fixation, structural stabilization and exciton confinement optimization. Compared to common "inactive" host, the passivation effects of TmPyPB markedly reduce trap-state densities by 24-40% to suppress nonradiation, resulting in the state-of-the-art PL and EL quantum yields reaching 99% and 15.6%, which are significantly improved by about 7 folds. TmPyPB simultaneously increases EL luminance to 104 nits, which is ~100 folds of non-doped analog.