Emission and Stability of Zero-Dimensional Perovskite Nanocrystals Across Halide Compositions

The exceptional optical and electronic properties of perovskite materials have attracted tremendous interest for optoelectronic technologies. They offer narrow emission bandwidth, high color tunability, facile chemical synthesis, and excellent charge transport. Stability remains a central consideration for advancing perovskites toward light-emitting devices. Low-dimensional, fully inorganic perovskites show promise to address this issue, with zero-dimensional (0D) cesium lead halide nanocrystals being particularly attractive because their isolated octahedral units avoid corner-sharing connectivity, leading to stronger exciton localization and improved stability. In our work, green-emitting Cs₄PbBr₆ nanocrystals show bright, stable luminescence with high photoluminescence yield, serving as a robust baseline. Extending these syntheses to iodide-rich compositions enables access to red emission but also reveals greater sensitivity to stoichiometry, phase purity, and dispersibility. Structural measurements highlight phase coexistence and cesium variations that influence emission behavior, offering important insights into the compositional factors that govern performance. Placed in the context of recent optimized reports, this comparative study highlights why bromide-based 0Ds are reliably emissive while iodide-rich analogues remain more challenging, and points toward strategies for achieving stable, reproducible, and color-tunable emission in perovskite-based LEDs.