Cation Effect on Anion Exchange in CsPbX₃ (X = Cl, Br, I) Perovskite Nanocrystals

The anion exchange in lead halide perovskite is a post-synthetic process that replaces the X-site anion with the target halide without phase transition. Various methods for adjusting the anions in perovskite nanocrystals (Pe NCs) have been developed; however, the effect of the cations in halide sources on the anion exchange has rarely been discussed. Here, we investigated the suitable chemicals and tendencies according to the cation in halide sources. NH4Cl and NaI were selected as efficient anion-exchanging chemicals because they effectively provide Cl- or I- anions to Pe NCs, respectively. Additionally, we discussed the hard-soft-acid-base (HSAB) theory. We observed that the anion-exchanged Pe NCs were well-dispersed with the original surface ligands, maintaining high colloidal stability. We believe that these findings would contribute to the improvement of optoelectronic devices, such as solar cells, displays, and light-emitting diodes (LEDs).