Green-emitting CsPbI3 nanorods decorated with CsPb2I5 and Cs4PbI6 nanoclusters†

Lead halide-based perovskites (CsPbX₃; X = Cl, Br, I) are prominent luminescent materials with pure red, green, and blue emissions; however, when mixed to obtain multiple emissions, they undergo spontaneous anion exchange reactions, which lead to undesirable changes in their photoluminescence (PL) and optical properties. This study presents iodide-based perovskites that can be color-transformed by controlling and coupling their phases in the nanoscale. The green-emitting CsPbI₃ nanorods decorated with Cs₄PbI₆ and CsPb₂I₅ nanoclusters (MP-nanorods) were produced by sequential transformation using the hot chemical method with the assistance of zirconium tetraisobutoxide and 1-octadecene. At room temperature, MP-nanorods exhibit narrow-band green emission with line widths of around 20.5 nm, originating from the multiphase heterojunction of CsPbI₃ nanorods coupled with Cs₄PbI₆ nanoclusters. Additionally, they can maintain and differentiate their initial photoemission in the colloidal mixture in the presence of red-emitting CsPbI₃ quantum dots without suffering from peak merging. The obtained results open the possibility of applications that require a stable mixture of multi-band gap systems such as complex anticounterfeiting, tandem rainbow solar cells, and white LED applications because they can retain their initial color purity without losing their original optical properties.