Solubility‐Controlled Room‐Temperature Synthesis of Cesium Lead Halide Perovskite Nanocrystals

All‐inorganic lead halide perovskite (IHP) nanocrystals (NC) have demonstrated to be a promising active material in a wide range of optoelectronic applications due to their chemical and thermal stability compared to organic‐inorganic perovskite NCs. However, the synthetic procedure of IHP NC generally requires a high‐temperature reaction of the precursors due to their limited solubility. Alternatively, the affinity of the precursor elements to the solvent was controlled to enhance their solubility in the liquid phase, and thus the enhanced kinetics in the crystallization process. Here, we show how the controlled solubility of Cs salts (i. e., Cs halide, acetate, carbonate) influences on their crystallization process and their optical properties. The formation of highly luminescent CsPbX3 (X=Cl, Br, and mixed Br/Cl and Br/I) NCs with a well‐controlled crystallinity and morphology provide fundamental insights into their crystallization process, broadening their applications in the optoelectronic devices. Controlled solubility of Cs salts (i. e., Cs halide, acetate, carbonate) influences their crystallization process and their optical properties. The formation of highly luminescent CsPbX3 (X=Cl, Br, and mixed Br/Cl and Br/I) NCs with a well‐controlled crystallinity and morphology provide fundamental insights into their crystallization process, broadening their applications in optoelectronic devices.