Unraveling the role of the precursors and the nucleation and growth mechanisms during lead halides perovskites nanocrystals formation by SAX

The recently developed slow room-temperature synthesis of lead halide perovskite nanocrystals (LHP NCs) has provided an opportunity to study their growth mechanism in situ. However, the reaction pathway from molecular precursors to nuclei remains unclear. This project aims to: (i) determine whether LHPs precursors (PbBr2-TOPO) are free molecular species in solution or whether TOPO is organized in small micelles embedding PbBr2 clusters, and (ii) to study the reaction mechanism of CsPbBr3 NCs nucleation and growth in situ thanks to a combination of wide-angle X-ray Total Scattering (TS) or Small Angle X-ray scattering (SAXS) techniques and UV-visible spectroscopy. These methods will allow the different stages of the reactions to be monitored from the atomic to the nanometer length scales. With this fundamental study, the interaction between the ligand TOPO and the PbBr2 clusters forming at the early stages of the reaction will be unveiled