Lead halide perovskite semiconductors have become a major research focus because of their huge potential for applications in optoelectronic devices. However, the mechanism of the underlying solid-state transformation typically used to grow perovskite crystals still remains unclear. We demonstrate that fluorescent microscopy is an effective tool to observe the transformation of single lead bromide nanocrystals into methyl ammonium lead bromide perovskite nanocrystals. We monitor the solid-state transformation in situ to reveal the reaction dynamics of individual nanocrystals. Fluorescence trajectories of lead bromide nanocrystals during the incorporation of methylammonium halide indicate that individual nanocrystal possess a distribution of incubation times before rapid conversion to the perovskite phase. We find that the distribution of waiting times becomes narrower with increasing concentration of methylammonium bromide. These data support a reaction mechanism where initial ion intercalation events activate the nanocrystal towards complete conversion. This study provides new insight into the solid-state transformation used to grow perovskite crystals and may be used to improve the quality and stability of this material.

In situ study of the transformation of lead halide nanocrystals into lead halide pervoskite nanocrystals using fluorescent microscopy

256th National Meeting (2018)

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