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Size Dependent Ternary Halide Solid Solutions in Perovskite Nanocrystals

Crystalline solid solutions incorporate guest atoms by substituting host lattice sites up to a solubility limit dictated by solute host similarity. Solid solutions enable tuning various material properties, such as the optoelectronic behavior of halide perovskites. In bulk, incompatibility of Cl:I halide mixtures restricts exploration throughout the ternary halide Cl:Br:I compositional range. However, solubility is extended in nanocrystals which better accommodate a wider range of ions within their lattice. Through high throughput synthesis and spectroscopic characterization of over 3000 samples, along with density functional theory and cluster expansion models, we determine the solubility boundaries of ternary halide perovskite nanocrystals and demonstrate their extended size dependent miscibility. Smaller nanocrystals, with sufficient Br content, stabilize the Cl:Br:I solid solutions, suppress planar stacking fault defects and prevent halide segregation.