Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1, CH-8093Zürich, Switzerland.
Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600Dübendorf, Switzerland.
Nano Lett. 2023 Jan 25;23(2):667-676. doi: 10.1021/acs.nanolett.2c04532. Epub 2023 Jan 6.
Despite broad interest in colloidal lead halide perovskite nanocrystals (LHP NCs), their intrinsic fast growth has prevented controlled synthesis of small, monodisperse crystals and insights into the reaction mechanism. Recently, a much slower synthesis of LHP NCs with extreme size control has been reported, based on diluted TOPO/PbBr precursors and a diisooctylphosphinate capping ligand. We report new insights into the nucleation, growth, and self-assembly in this reaction, obtained by synchrotron-based small-angle X-ray scattering and optical absorption spectroscopy. We show that dispersed 3 nm Cs[PbBr] agglomerates are the key intermediate species: first, they slowly nucleate into crystals, and then they release Cs[PbBr] monomers for further growth of the crystals. We show the merits of a low Cs[PbBr] monomer concentration for the reaction based on oleate ligands. We also examine the spontaneous superlattice formation mechanism occurring when the growing nanocrystals in the solvent reach a critical size of 11.6 nm.
尽管人们对胶体卤化铅钙钛矿纳米晶体（LHP NCs）很感兴趣，但它们的快速内在生长阻碍了对小单分散晶体的控制合成和对反应机制的深入了解。最近，基于稀释的 TOPO/PbBr 前体和二异辛基膦酸酯封端配体，报道了一种 LHP NCs 合成速度极慢且具有极端尺寸控制的方法。我们通过基于同步加速器的小角 X 射线散射和光吸收光谱，报告了在该反应中对成核、生长和自组装的新见解。我们表明，分散的 3nm Cs[PbBr] 团聚物是关键的中间体：首先，它们缓慢地成核为晶体，然后释放 Cs[PbBr] 单体以进一步生长晶体。我们展示了基于油酸配体的低 Cs[PbBr] 单体浓度对反应的优点。我们还研究了当溶剂中的生长纳米晶体达到 11.6nm 的临界尺寸时，自发超晶格形成机制的发生。
