Synthesis and optical properties of ordered-vacancy perovskite cesium bismuth halide nanocrystals

Perovskite-phase cesium bismuth halide (Cs₃Bi₂X₉; X = Cl, Br, I) nanocrystals were synthesized using a hot-injection approach. These nanocrystals adopted ordered-vacancy perovskite crystal structures and demonstrated composition-tunable optical properties. Growth occurred by initial formation of Bi⁰ seeds, and morphology was controlled by precursor and seed concentration. The Cs₃Bi₂I₉ nanocrystals demonstrated excellent stability under ambient conditions for several months. Contrary to previous reports, we find that photoluminescence originates from the precursor material as opposed to the Cs₃Bi₂X₉ nanocrystals.