Mechanistic Insight into the Precursor Chemistry of Cesium Tin Iodide Perovskite Nanocrystals

Colloidaltin halide perovskite nanocrystals (NCs) are of interestas an alternative to their lead-based counterparts. While some advancementshave been achieved in their synthetic development, the reaction mechanism,especially the precursor chemistry, of tin halide perovskite NCs remainspoorly understood. Here, using cesium tin iodide (CsSnI3) perovskite NCs as a model system, we report on the mechanisticinsight into the precursor chemistry of tin-based perovskite NCs througha combination of infrared, mass spectrometry, and nuclear magneticresonance spectroscopy. We identify that the active intermediate complexes,polymeric alkanoate iodides that form via the reaction of the iodidesource with oligomers present in the tin(II) carboxylates, play akey role in governing the reactivity of the tin iodide precursor,which leads to the variation in the size, size uniformity, and photoluminescencequantum yield of CsSnI3 NCs. Our work underscores the importanceof understanding the precursor chemistry as a key parameter to designand synthesize tin halide perovskite NCs, which not only aids in theirsyntheses by design but also might benefit the fabrication of high-qualitypolycrystalline tin-based films.