Review on Anion Exchange of Lead‐Halide Perovskite Nanocrystals: Process, Methods, and Applications

Lead‐halide perovskites are a new class of semiconductor materials that have excellent optoelectronic properties and can be easily transformed into bright luminescent colloidal nanocrystals. These characteristics bring great prospects for the development of high‐efficiency optical devices. These materials possess unique anion‐exchange properties that allow for post‐synthesis adjustment of the bandgap. Anion exchange typically initiates at the surface: Perovskite nanocrystals have flexible lattice properties, which allow ions to gradually diffuse into the interior of the crystal with the help of vacancies, resulting in the formation of complete or mixed‐phase perovskites. Various methods, such as liquid phase, gas phase, and solid phase anion exchange, enable precise control over the composition and bandgap modulation, thereby tuning the emission wavelengths of nanocrystals across the visible spectrum. The flexibility and precision offered by anion exchange facilitate effective phase control and engineering of the optoelectronic properties of lead‐halide perovskites. This, in turn, opens up opportunities for their application in light‐emitting diodes, solar cells, and detectors, thus driving further advancements in anion‐exchange technology.