Powder Atomic Layer Deposition–Enabled Stable Perovskite Phosphors for UV‐Wavelength‐Discriminable Luminescent Films

Abstract All‐inorganic halide perovskites, such as Cs 4 PbBr 6 /CsPbBr 3 , exhibit excellent optical properties and intrinsic stability as 0D materials, rendering them attractive for photonic applications. However, the vulnerability of these materials to moisture and heat necessitates the implementation of stabilization strategies. Conventional solution‐based methods, such as doping or surface passivation, often require solvents that reduce uniformity and degrade optical performance. To overcome these limitations, a solvent‐free powder atomic layer deposition (PALD) technique to coat Cs 4 PbBr 6 /CsPbBr 3 powders with conformal Al 2 O 3 nanolayers is employed. The PALD‐grown layer effectively passivated surface defects, suppressed Br vacancies, and stabilized the crystal structure of the perovskite in steam and polar solvents and under heat exposure. Importantly, relative photoluminescence quantum yield increased by up to 14% compared to the uncoated powders. Based on these strategies, it is fabricated a UV‐responsive photoluminescent film by integrating Al 2 O 3 ‐coated Cs 4 PbBr 6 /CsPbBr 3 (green emission under UVA/UVB) with Al 2 O 3 ‐coated Cs 2 Cu 3 I 5 (blue emission under UVB/UVC), achieving clear wavelength‐discriminable emissions, i.e., green, sky blue, and deep blue under UVA, UVB, and UVC illumination, respectively. This study demonstrates the potential of PALD as a scalable, solvent‐free passivation method that enhances the environmental stability and optical performance of halide perovskites, thereby improving their commercial viability for use in next‐generation optoelectronic devices.