Growth of Highly Stable and Luminescent CsPbX3(X = Cl, Br, and I) Nanoplates via Ligand Mediated Anion Exchange of CsPbCl3Nanocubes 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 CsPbCl3nanocubes into anisotropic CsPbX3nanoplates (NPs) through adding a mixture of dodecanethiol (DDT) and AlX3(X = Cl, Br, I) to a solution of CsPbCl3nanocrystals. The anion-exchanged nanocrystals consist of mostly plate-shaped CsPbX3nanocrystals along {010} facets. Although DDT or AlX3treatment alone results in increased photoluminescence quantum yield, ΦPL, the combination of both DDT and AlX3leads 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-AlX3ligand mediated anion exchange show photoluminescence quantum yields of 47 and 65% for violet and blue emitters (CsPbCl3and CsPbCl3–xBrx), respectively, near 100% for green emitters (CsPbBr3), and 81% for red emitters (CsPbI3), while maintaining good long-term stability.