Reaction-controlled shape evolution and insights into the growth mechanism of CsPbBr₃ nanocrystals

The correlation between structural transformation and optical characteristics of cesium lead bromide (CsPbBr₃) nanocrystals (NCs) suggests insights into their growth mechanism and optical performance. Systematic control of reaction parameters led to the successful fabrication of on-demand shape-morphing CsPbBr₃ NCs. Transmission electron microscopy observations showed that the shape transformation from nanocubes to microcrystals could be accelerated by increasing the precursor:ligand molar ratio and reaction time. Further evidence for orthorhombic CsPbBr₃ NCs was obtained from their selected-area electron diffraction pattern, which exhibits a twin domain induced by the presence of large NCs. Likewise, we observed a substantial decrease in photoluminescence (PL) intensity of CsPbBr₃ due to surface decomposition or surface ligand loss resulting from increased size. In addition, fusion of smaller particles having other dimensionality induced the increase in the PL full-width at half maximum. In particular, existence of larger bulk material caused a reduction in the peak intensity in the absorption spectra and a trend of decreasing tendency in intensity of the absorption bands related to bromoplumbate species provided direct evidence of fully converted Cs-oleate.