Surface Cation Cross‐Locking Enables Non‐Destructive “On‐Demand” Synthesis of Anion‐Exchanged CsPbX ₃ Perovskite Nanocrystals

Abstract Post‐synthetic halide anion exchange is considered a “double‐edged sword” for perovskite nanocrystals (PNCs), which offer unique access to color tunability while bringing about surface defects. Herein, a novel surface cation cross‐locking (SCCL) strategy is proposed to achieve the anion‐exchanged CsPbX 3 PNCs (X is Cl, Br, I) with non‐destructive emissions. This is achieved using a dendritic ligand of Pentaerythritol tetrakis (3‐mercaptopropionate) (PETMP) as a surface cross‐locker, which can form the multiple coordination to the surface Pb cation of octahedral [PbX 6 ] 4− during the fast halide anion exchange via four end‐thiolates and four side‐carboxylates. As a result, the red‐ and blue‐emitting anion‐exchanged CsPbX 3 PNCs exhibit high photoluminescence quantum yield (PLQY) values of >97%, close to the parent green‐emitting CsPbBr 3 PNCs. Moreover, the “on‐demand” synthesis of anion‐exchanged CsPbX 3 PNCs is also performed via autonomous robotic in‐flow experimentation. This work provides a new general post‐synthetic way for the full‐color CsPbX 3 PNCs with compositions that are inaccessible via direct synthetic routes.