Interfacial Passivation Enormously Enhances Electroluminescence of Triphenylphosphine Cu4I4 Cube

Abstract Defect is one of the key factors limiting optoelectronic performances of organic–inorganic hybrid systems. Although high‐efficiency bidentate ligands based electroluminescent (EL) clusters reported, until present, only few EL clusters based on monodentate ligands are realized since their structural instability induces more surface/interface defects. Herein, this bottleneck is first overcome in virtue of interfacial passivation by electron transporting layers (ETL). Through using TmPyPB with meta ‐linked pyridines as ETL, photoluminescent (PL) and EL quantum efficiencies of the simplest monophosphine Cu 4 I 4 cube [TPP] 4 Cu 4 I 4 are greatly improved by ≈2 and 23 folds, respectively, as well as ≈200 folds increased luminance, corresponding to a huge leap from nearly unlighted (<20 nits) to highly bright (>3000 nits). The passivation effect of TmPyPB on surface defects of cluster layer is embodied as preventing interfacial charge trapping and suppressing exciton nonradiation.