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

Colloidal tin halide perovskite nanocrystals (NCs) are of interest as an alternative to their lead-based counterparts. While some advancements have been achieved in their synthetic development, the reaction mechanism, especially the precursor chemistry, of tin halide perovskite NCs remains poorly understood. Here, using cesium tin iodide (CsSnI3) perovskite NCs as a model system, we report on the mechanistic insight into the precursor chemistry of tin-based perovskite NCs through a combination of infrared, mass spectrometry, and nuclear magnetic resonance spectroscopy. We identify that the active intermediate complexes, polymeric alkanoate iodides that form via the reaction of the iodide source with oligomers present in the tin(II) carboxylates, play a key role in governing the reactivity of the tin iodide precursor, which leads to the variation in the size, size uniformity, and photoluminescence quantum yield of CsSnI3 NCs. Our work underscores the importance of understanding the precursor chemistry as a key parameter to design and synthesize tin halide perovskite NCs, which not only aids in their syntheses by design but also might benefit the fabrication of high-quality polycrystalline tin-based films.