CsPbBr3 Quantum Dots 2.0: Benzenesulfonic Acid Equivalent Ligand Awakens Complete Purification

Abstract The stability and optoelectronic device performance of perovskite quantum dots (Pe‐QDs) are severely limited by present ligand strategies since these ligands exhibit a highly dynamic binding state, resulting in serious complications in QD purification and storage. Here, a “Br‐equivalent” ligand strategy is developed in which the proposed strong ionic sulfonate heads, for example, benzenesulfonic acid, can firmly bind to the exposed Pb ions to form a steady binding state, and can also effectively eliminate the exciton trapping probability due to bromide vacancies. From these two aspects, the sulfonate heads play a similar role as natural Br ions in a perfect perovskite lattice. Using this approach, high photoluminescence quantum yield (PL QY) > 90% is facilely achieved without the need for amine‐related ligands. Furthermore, the prepared PL QYs are well maintained after eight purification cycles, more than five months of storage, and high‐flux photo‐irradiation. This is the first report of high and versatile stabilities of Pe‐QD, which should enable their improved application in lighting, displays, and biologic imaging.