Fast Anion-Exchange in Highly Luminescent Nanocrystals of Cesium Lead Halide Perovskites (CsPbX₃, X = Cl, Br, I)

TLDR

Postsynthetic ion‑exchange of colloidal nanocrystals enables compositional fine‑tuning and access to otherwise unavailable materials, yet anion‑exchange remains underexplored compared to the common cation‑exchange. The study reports rapid, low‑temperature anion‑exchange—partial or complete—in highly luminescent CsPbX₃ perovskite nanocrystals. The authors achieve fast, low‑temperature anion‑exchange by mixing CsPbCl₃, CsPbBr₃, and CsPbI₃ nanocrystals in specific ratios, enabling uniform mixed‑halide compositions via internanocrystal exchange. The method tunes photoluminescence across 410–700 nm with quantum yields of 20–80 % and narrow 10–40 nm linewidths, and achieves uniform mixed‑halide compositions via fast internanocrystal exchange.

Abstract

Postsynthetic chemical transformations of colloidal nanocrystals, such as ion-exchange reactions, provide an avenue to compositional fine-tuning or to otherwise inaccessible materials and morphologies. While cation-exchange is facile and commonplace, anion-exchange reactions have not received substantial deployment. Here we report fast, low-temperature, deliberately partial, or complete anion-exchange in highly luminescent semiconductor nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, I). By adjusting the halide ratios in the colloidal nanocrystal solution, the bright photoluminescence can be tuned over the entire visible spectral region (410–700 nm) while maintaining high quantum yields of 20–80% and narrow emission line widths of 10–40 nm (from blue to red). Furthermore, fast internanocrystal anion-exchange is demonstrated, leading to uniform CsPb(Cl/Br)3 or CsPb(Br/I)3 compositions simply by mixing CsPbCl3, CsPbBr3, and CsPbI3 nanocrystals in appropriate ratios.