Fine Tuning Phosphonate Synthesis Yields of CsPbBr3 Perovskite Nanocrystals with Enhanced Stability for Applications in Quantum Technologies

In the last few years, lead halide nanocrystals with perovskite mineral structures (PNСs) have attracted increasing attention due to their excellent optical and physical properties, which make them promising for liquid crystal displays, light-emitting diodes, solar concentrators and basic elements of quantum computing systems. Initially, the synthesis of PNСs was carried out using oleic acid and oleylamine as organic surface ligands, and the materials obtained in this way did not have sufficient colloidal and photostability for practical applications. This problem was partially overcome by the use of phosphonic acids and other types of molecules as ligands, but in this case, the reaction is often incomplete, resulting in some of the metal precursors remaining in the product, which in turn leads to a gradual degradation of the optical properties of PNСы. Here, we demonstrate the effective application of a method of additional purification of CsPbBr₃ PNC solutions obtained by colloidal synthesis using tetradecylphosphonic acid as a ligand by gel permeation chromatography. As a result of this procedure, we were able to remove the excess of unreacted precursors from the synthesized nanocrystals, which allowed us to achieve the preservation of a high value of the quantum yield of PNCs fluorescence within 6 months from the moment of their synthesis. The results open perspectives for creation of more efficient material for application in the fields of quantum technologies and, in particular, for creation of single photon sources.