外源金属阳离子在CsPbBr3纳米晶合成中的作用及其与三级胺的相互作用
Exogenous Metal Cations in the Synthesis of CsPbBr3 Nanocrystals and their Interplay with Tertiary Amines
AI总结：
研究通过引入外源金属阳离子优化CsPbBr3纳米晶合成，发现其与三级胺的相互作用可提高发光效率并重塑纳米晶形貌。
摘要：
当前合成CsPbBr3卤化物钙钛矿纳米晶（NCs）的方法依赖于过量的Pb²+前驱体，导致最终过程仍有未反应的铅离子。在我们的CsPbBr3 NCs合成方案中，我们用不同的外源金属阳离子（M）替代了多余的Pb²+，并研究了它们对合成产物的影响。这些阳离子可分为两组：第一组产生以油酸物种封端的单分散CsPbBr3立方体（如当Pb²+过量时的情况），其发光量子效率（PLQY）可高达90%（某些阳离子，例如M=In³+）；第二组产生形状不规则的CsPbBr3 NCs，具有宽广的尺寸分布。在两种情况下，合成过程中添加三级铵阳离子（二十二烷基甲基铵，DDMA+），在NCs成核后重塑NCs为单分散的截断立方体。这些NCs具有混合的油酸/DDMA+表面终止，其PLQY值可高达90%。对于第一组阳离子，只有当铵阳离子以盐的形式（DDMA-Br）直接添加时才会发生这种情况；而对于第二组阳离子，即使使用相应的三级胺（DDMA）代替DDMA-Br，也会发生这种情况。这归因于只有第二组阳离子才能促进DDMA被反应环境中过量的油酸质子化。在所有研究的情况下，M阳离子的掺入是微小的，NCs的重塑过程是短暂的：如果反应时间较长，截断立方体将转化为立方体。
英文摘要：
Current syntheses of CsPbBr3 halide perovskite nanocrystals (NCs) rely on over-stoichiometric amounts of Pb2+ precursors, resulting in unreacted lead ions at the end of the process. In our synthesis scheme of CsPbBr3 NCs we replaced excess Pb2+ with different exogenous metal cations (M) and investigated their effect on the synthesis products. These cations can be divided into two groups: group 1 delivers monodisperse CsPbBr3 cubes capped with oleate species (as for the case when Pb2+ is used in excess) and with photoluminescence quantum yield (PLQY) as high as 90% with some cations (for example with M= In3+); group 2 yields irregularly shaped CsPbBr3 NCs with broad size distributions. In both cases, the addition of a tertiary ammonium cation (didodecylmethyl ammonium, DDMA+) during the synthesis, after the nucleation of the NCs, reshapes the NCs to monodisperse truncated cubes. Such NCs feature a mixed oleate/DDMA+ surface termination with PLQY values up to 90%. For group 1 cations, this happens only if the ammonium cation is directly added as a salt (DDMA-Br) while for group 2 cations this happens even if the corresponding tertiary amine (DDMA) is added, instead of DDMA-Br. This is attributed to the fact that only group 2 cations can facilitate the protonation of DDMA by the excess oleic acid present in the reaction environment. In all cases studied, the incorporation of M cations is marginal and the reshaping of the NCs is only transient: if the reactions are run for a long time the truncated cubes evolve to cubes.
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