Pradhan Narayan
School of Materials Sciences, Indian Association for the Cultivation of Science, Kolkata 700032, India.
Acc Chem Res. 2021 Mar 2;54(5):1200-1208. doi: 10.1021/acs.accounts.0c00708. Epub 2021 Feb 14.
ConspectusThe interactions of halides and ammonium ions with lead halide perovskite nanocrystals have been extensively studied for improving their phase stability, controlling size, and enhancing their photoluminescence quantum yields. However, all these nanocrystals, which showed intense and color tunable emissions, mostly retained the six faceted cube or platelet shapes. Shape tuning needs the creation of new facets, and instead of composition variations by foreign ions interactions/substitutions, these require facet stabilizations with suitable ligands. Among most of the reported cases of lead halide perovskites, alkyl ammonium ions are used as a capping agent, which substituted in the surface Cs(I) sites of these nanocrystals. Hence, new surface ligands having a specific binding ability with different facets other than those in cube/platelet shapes are required for bringing stability to new facets and, hence, for tuning their shapes.In this Account, interactions of alkyl ammonium ions on the surface of perovskite nanocrystals and their impact on surface reconstructions are reviewed. Emphasizing the most widely studied CsPbBr nanocrystals, the usefulness and impact of alkyl ammonium ions on the phase stability, high-temperature annealing, enhancement of the brightness and doping in these nanocrystals are first discussed. Then, nanocrystals formed under limited primary alkyl ammonium ions and also with specific tertiary ammonium ions having new facets are elaborated. Further, the treatment of excess alkyl ammonium halides to these newly formed multifaceted polyhedron nanocrystals under different conditions, which led to armed and step-armed structures, are discussed. The change in optical properties during these shape transformations is also presented. Finally, the shape-change mechanism with alkyl ammonium halide-induced dissolutions of {200} and {112} facets and formation of {110} and {002} facets are discussed. Further, in summary, future prospects of new ligand designing for stabilizing new facets of perovskite nanocrystals and obtaining new shapes and properties are proposed.
综述
卤化物和铵离子与卤化铅钙钛矿纳米晶体的相互作用已被广泛研究，以改善其相稳定性、控制尺寸并提高其光致发光量子产率。然而，所有这些显示出强烈且颜色可调发射的纳米晶体大多保留了六面立方体或片状形状。形状调控需要创建新的晶面，这需要用合适的配体来稳定晶面，而不是通过外来离子相互作用/取代来改变组成。在大多数报道的卤化铅钙钛矿案例中，烷基铵离子被用作封端剂，它取代了这些纳米晶体表面的Cs(I)位点。因此，需要具有与立方/片状形状以外的不同晶面具有特定结合能力的新表面配体，以给新晶面带来稳定性，从而调控它们的形状。
在本综述中，回顾了烷基铵离子在钙钛矿纳米晶体表面的相互作用及其对表面重构的影响。以研究最广泛的CsPbBr纳米晶体为例，首先讨论了烷基铵离子对这些纳米晶体的相稳定性、高温退火、亮度增强和掺杂的有用性及影响。然后，阐述了在有限的伯烷基铵离子以及具有新晶面的特定叔铵离子存在下形成的纳米晶体。此外，还讨论了在不同条件下对这些新形成的多面体形纳米晶体处理过量的烷基卤化铵，从而导致武装和阶梯状武装结构的情况。还介绍了这些形状转变过程中光学性质的变化。最后，讨论了烷基卤化铵诱导{200}和{112}晶面溶解以及{110}和{002}晶面形成的形状变化机制。此外，总结并提出了用于稳定钙钛矿纳米晶体新晶面并获得新形状和性质的新配体设计的未来前景。
