Single particle fluorescence imaging of perovskite nanocrystal crystallization for illustrating coupled...

Because of the lack of spatiotemporal characterization techniques, it has been of great challenge to investigate the crystallization of nanocrystals. With a high-speed structured illumination super-resolution fluorescence microscopy (SIM), we hereby report an in situ fluorescence imaging technique to monitor the crystallization of perovskite nanocrystals at single-particle level. By correlating the fluorescence intensity with particle size, we illustrate the coupled nucleation-and-growth of perovskite nanocrystals in polymer matrix. The temporal fluorescence intensity analysis of individual nanocrystals reveals the diffusion-controlled growth process with a fast growth at the beginning followed by a slow growth. The analysis of ensemble nanocrystals illustrates the evolution of nucleation rate with the change of precursor concentrations. We further analyze the Gibbs free energy fluctuation of couple nucleation-and-growth. The growth free energy dominates in the continuous nucleation of perovskite nanocrystals, which accounts for the narrow size distribution. In comparison with LaMer model, the coupled nucleation-and-growth provides an alternative model to fabricate narrow sized nanocrystals.