Nanoscale crystals provide model systems to understand the complex kinetics of solid-state transformations. For example, the conversion of lead iodide into methyl ammonium lead iodide involves the intercalation of both a methyl ammonium cation and an iodide anion along with a change in the connectivity of the lead iodide octahedra. This solid-state reaction is one route to produce polycrystalline perovskite semiconductor films for photovoltaic devices, where the grain size and surface faceting of the perovskite films strongly affect device performance and stability. We are using single-particle fluorescence microscopy to directly observe this transformation in crystals with sizes of 10 nm or less. By monitoring the reaction kinetics of hundreds of nanocrystals, we propose a model for this solid-state transformation in which initial intercalation events at the surface activate the nanocrystal for rapid and complete transformation.

Watching single nanocrystal transformations with fluorescence microscopy

256th National Meeting (2018)

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