Growth of Highly Stable and Luminescent CsPbX3 (X = Cl, Br, and I) Nanoplates via Ligand Mediated Anion Exchange of CsPbCl3 Nanocubes with AlX3

Two-dimensional metal halide perovskite nanocrystals are attractive for their blue-shifted absorption relative to their 3D counterparts, narrow emission line widths, high absorption cross sections, and high radiative recombination. Herein, we report a ligand mediated anion exchange reaction that transforms CsPbCl3 nanocubes into anisotropic CsPbX3 nanoplates (NPs) through adding a mixture of dodecanethiol (DDT) and AlX3 (X = Cl, Br, I) to a solution of CsPbCl3 nanocrystals. The anion-exchanged nanocrystals consist of mostly plate-shaped CsPbX3 nanocrystals along {010} facets. Although DDT or AlX3 treatment alone results in increased photoluminescence quantum yield, ΦPL, the combination of both DDT and AlX3 leads to the formation of plate-shaped nanocrystals, higher ΦPL, and improved stability as compared to when only one of these is used. We suspect nanocrystal exfoliation driven by ligand penetration and self-assembly both play important roles in transforming the parent nanocubes into NPs. The NPs are highly emissive and stable due to the introduction of both an anion source and surface ligand. Nanoplates synthesized through DDT-AlX3 ligand mediated anion exchange show photoluminescence quantum yields of 47 and 65% for violet and blue emitters (CsPbCl3 and CsPbCl3–xBrx), respectively, near 100% for green emitters (CsPbBr3), and 81% for red emitters (CsPbI3), while maintaining good long-term stability.二维金属卤化物钙钛矿纳米晶因其相较于三维对应体的吸收蓝移特性、窄发射线宽、高吸收截面以及高辐射复合率而备受关注。本文报道了一种配体介导的阴离子交换反应：将十二硫醇（dodecanethiol, DDT）与AlX₃（X=Cl、Br、I）的混合体系加入CsPbCl₃纳米晶溶液中，可将CsPbCl₃纳米立方体转化为各向异性CsPbX₃纳米片（nanoplates, NPs）。经阴离子交换得到的纳米晶主要为沿{010}晶面生长的板状CsPbX₃纳米晶。尽管单独使用DDT或AlX₃处理即可提升光致发光量子产率（photoluminescence quantum yield, ΦPL），但相较于单一试剂处理，同时使用DDT与AlX₃不仅可得到板状纳米晶，还能获得更高的ΦPL以及更优异的稳定性。我们推测，配体渗透驱动的纳米晶剥离与自组装过程，在母相纳米立方体转化为NPs的过程中均发挥了关键作用。由于同时引入了阴离子源与表面配体，所制备的NPs兼具高发光性能与稳定性。通过DDT-AlX₃配体介导的阴离子交换法合成的纳米片，其光致发光量子产率表现优异：紫色发射体（CsPbCl₃）与蓝色发射体（CsPbCl₃–ₓBrₓ）的ΦPL分别可达47%与65%，绿色发射体（CsPbBr₃）的ΦPL接近100%，红色发射体（CsPbI₃）的ΦPL为81%，且该材料同时具备良好的长期稳定性。