Role of Acid–Base Equilibria in the Size, Shape, and Phase Control of Cesium Lead Bromide Nanocrystals

[Image: see text] A binary ligand system composed of aliphatic carboxylic acids and primary amines of various chain lengths is commonly employed in diverse synthesis methods for CsPbBr(3) nanocrystals (NCs). In this work, we have carried out a systematic study examining how the concentration of ligands (oleylamine and oleic acid) and the resulting acidity (or basicity) affects the hot-injection synthesis of CsPbBr(3) NCs. We devise a general synthesis scheme for cesium lead bromide NCs which allows control over size, size distribution, shape, and phase (CsPbBr(3) or Cs(4)PbBr(6)) by combining key insights on the acid–base interactions that rule this ligand system. Furthermore, our findings shed light upon the solubility of PbBr(2) in this binary ligand system, and plausible mechanisms are suggested in order to understand the ligand-mediated phase control and structural stability of CsPbBr(3) NCs.