Understanding the Ligand-Assisted Reprecipitation of CsPbBr3 Perovskite Nanocrystals via High Throughput Robotic Synthesis Approach

Inorganic cesium lead bromide (CsPbBr3) perovskite nanocrystals (PNCs) have rendered promising performances in various optoelectronic applications. In contrast to the complex hot-injection synthesis, the ligand-assisted reprecipitation (LARP) method renders a simple route enabling mass-production of high-quality PNCs. However, LARP synthesis is susceptible, and thus, little has been deeply understood about how to control the growth of PNCs and the optical characteristics of the PNCs. Herein, by implementing a high-throughput automated experimental platform, we explore the growth behaviors and colloidal stability of the LARP-synthesized PNCs. Using two distinctive acid-base pairs - oleic acid-oleylamine and octanoic acid-octylamine, we systematically explore the influence of ligands - chain lengths, concentration and ratios - on the particle growths and consequent functionalities of the PNCs. We observe that the short-chain ligands cannot make functional PNCs with desired sizes and shapes, whereas the long-chain ligands provide homogeneous and stable PNCs. The PNCs transform into a Cs-rich non-perovskite structure with poorer emission functionalities and larger size distributions by employing excessive amines or polar antisolvent. This proposes that the diffusion of the ligands in a reaction system crucially determines the structures and functionalities of the PNCs. Our high-throughput exploration provides a detailed guidance on synthesis routes for desired PNCs.