All Inorganic Halide Perovskite Superlattices With All Visible Spectral Collective Coherent Emissions

ABSTRACT Self‐assembled inorganic halide perovskite superlattices (HPSLs) have attracted extensive attention for their well‐ordered structure and unique collective photonic properties, which differ from those of individual nanocrystals (NCs). However, the manipulation of ordered HPSLs with all‐halogen and alloyed halogen components, as well as the regulation of their coherent spontaneous emission across the visible spectrum, remains underexplored. In this study, we employ a combination of anion‐exchange reactions and a slow solvent evaporation strategy to self‐assemble monodisperse, uniform all inorganic perovskite NCs into a series of well‐defined, long‐range ordered, and densely packed CsPbX 3 (X = Cl, Br, I, and mixed halide systems such as Cl/Br, Br/I, and Cl/Br/I) superlattices, achieving coherent photoluminescence (PL) emission across the entire visible spectrum (400–700 nm). Notably, the collective coherent emission of all HPSLs exhibits dynamic redshifts and accelerated collective radiative decay due to strong electronic coupling between NCs at cryogenic temperatures (7 K). This study not only systematically investigates all‐halide compositional HPSLs but also paves the way for quantum light source applications across the visible spectrum.