NaI‐Mediated Dispersion of Cuprous Halide Clusters via Ball‐Milling for Efficient White Light‐Emitting Diodes

Cuprous (Cu(I)) halide clusters have garnered significant attention for light‐emitting devices (LEDs) due to their high photoluminescence quantum yields and broadband emission, both originating from self‐trapped excitons. However, their practical implementation is impeded by poor solution processability and challenges in fabricating high‐quality films. Herein, we report a facile, scalable mechanochemical synthesis of highly luminescent Cu(I) halide clusters via direct ball milling under ambient conditions. Notably, the incorporation of sodium iodide enhances the dispersibility and solution processability of these clusters without deteriorating their emission properties, enabling the preparation of stable colloidal dispersions and the one‐step solution deposition of smooth, uniform films. The resultant electroluminescent devices achieve a peak external quantum efficiency of 5.9% and exhibit uniform yellow emission over a large area of 5 × 5 cm 2 . Through judicious selection of charge‐transport layers, we further demonstrate broadband white electroluminescence with voltage‐tunable color temperature. Our strategy provides a practical pathway to efficient, scalable, and low‐toxicity Cu(I) halide cluster LEDs, while offering key design principles for developing high‐performance solution‐processable emissive materials in next‐generation solid‐state lighting.