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

近年来发展的室温慢速卤化铅钙钛矿纳米晶（lead halide perovskite nanocrystals, LHP NCs）合成方法，为原位研究其生长机理提供了重要契机。然而，从分子前驱体到晶核的反应路径仍不明确。本项目旨在达成两大目标：（i）明确卤化铅钙钛矿前驱体（PbBr2-TOPO）在溶液中是以游离分子形式存在，还是三辛基氧化膦（TOPO）组装形成包裹PbBr2团簇的小型胶束；（ii）结合广角X射线全散射（Total Scattering, TS）、小角X射线散射（Small Angle X-ray scattering, SAXS）技术与紫外-可见光谱，原位探究CsPbBr3纳米晶（CsPbBr3 NCs）的成核与生长反应机理。上述方法可实现从原子尺度到纳米尺度的反应全阶段监测。通过本基础研究，将揭示反应早期阶段形成的配体TOPO与PbBr2团簇之间的相互作用。