Rational Ligand Engineering Enables Emission-Tunable Copper Nanoclusters for High-Performance LEDs.

Metal nanoclusters with atomic precision represent a highly attractive platform for designing optoelectronics, yet achieving controllable emission tuning and translating structural modulation into high-performance electroluminescent devices remains a major challenge. Here we realize precise emission wavelength tuning from yellow to red by rational ligand engineering toward a family of atomically precise Cu2(BINAP)2(SR)2 clusters. The modulation mechanism of the correlations between electron-withdrawing capability of substituents and tunable emission wavelengths was clearly elucidated by density functional theory calculations. Besides, the methyl-functionalized Cu2 clusters show remarkably enhanced photoluminescence intensity, and the cluster-based emitters in light-emitting diodes displays a high external quantum efficiency of 14.53%, together with favorable brightness and efficiency stability. This work not only validates the effectiveness of ligand substitution in tailoring the photophysical properties of copper clusters but also establishes a general design route toward high-performance, color-tunable cluster-based luminescent materials for advanced optoelectronic applications.