Size and Shape Tunability of Cesium Lead Bromide Nanocrystals by Pb(II) Counter Anions

The size modulation of perovskite nanocrystals is a well-established practice in existing literature, achieved through adjustments in reaction temperature or ligand chain lengths. However, our study introduces a novel approach, aiming to govern the dimensions (including shape, size, and phase) of these nanocrystals by manipulating the counter anions of Pb(II) during the synthesis by hot-injection method. We utilize diethyl 2-bromomalonate as the bromide precursor for this purpose. The resulting tunability is ascribed to the specific counter anion present in the Pb(II) salts. For instance, lead acetate, lead bromide, lead oxide, and lead nitrate resulted in the formation of 1D (nanorods), 2D (nanoplatelets), 3D (nanocubes), and quantum dots, respectively. Despite the diverse range of sizes and shapes achieved, all CsPbBr3 nanocrystals consistently exhibit a high photoluminescence quantum yield (PLQY > 90%) with considerable excited state lifetimes (τ ~ 18-20 ns). Moreover, these nanocrystals remain highly stable when exposed to air in colloidal solutions.