This paper demonstrates efficient ultra-broadband electroluminescence from copper iodide (CuI) nanocluster single emitters. A one-step solution synthesis-deposition process, utilizing carefully designed ligands and solvents, created CuI nanoclusters exhibiting high rigidity and dual-emissive modes (phosphorescence and temperature-activated delayed fluorescence). The resulting light-emitting diodes (LEDs) showed an emission full width at half maximum (FWHM) of ~120 nm, a peak external quantum efficiency of 13%, a maximum luminance of ~50,000 cd m², and an operating half-lifetime of 137 h at 100 cd m². The LEDs performed consistently in inert and air atmospheres without encapsulation, highlighting the potential of CuI nanoclusters for next-generation healthy lighting.
