Vapor-deposited copper iodide cluster-based light-emitting diodes for pico-projector

Vapor-deposited metal halide clusters have demonstrated great potential for next-generation lighting and display applications. However, the direct synthesis-on-substrate of highly emissive materials via dry reaction technique is restricted by insufficient chemical reaction and precursor aggregation, leading to inferior device performance compared to their solution-processed counterparts. Here, we report a one-step vacuum synthesis deposition of copper(I) iodide clusters with near-unity photoluminescence quantum yields by engineering the stereohindrance of the organic ligand. When codeposited copper(I) iodide and 3,5-di(9H-carbazol-9-yl)pyridine (35DCzPPy) with minimal steric hindrance near the pyridine group, [35DCzPPy]₄Cu₂I₂ clusters are uniformly assembled without copper-copper aggregation. Consequently, light-emitting diodes (LEDs) based on clusters show a peak external quantum efficiency of 19.4%, a maximum luminance of 34,232 candelas per square meter, and a record operating T₅₀ lifetime of 4186 hours at 100 candelas per square meter. Moreover, we integrated the LEDs onto backplane drivers for active-matrix (AM) cluster LED (CLED) display panels, which enables the prototype of a high-dynamic-range pico-projector. Our results demonstrate the potential of vapor-deposited copper halide clusters for next-generation lighting and displays.