Organic metal halide perovskite nanocrystals are promising candidates for light-emitting diodes due to their narrow emission bandwidth, high photoluminescence quantum yield (PLQY), and color tunability. Nevertheless, these systems suffer from thermal instability, phase impurities, and a sensitivity to processing techniques. This study reports the first synthesis of novel Cs-containing triple cation perovskite nanocrystals with nominal stoichiometry Cs_x(MA_0.17FA_0.83)_1−xPbBr₃ (x = 0–0.15). The effect of Cs⁺ cation incorporation is thoroughly investigated using diffraction, microscopy and solid state MAS NMR techniques. The solid state ¹³³Cs MAS NMR results reveals the distribution of the Cs⁺ cations is highly concentration and particle size dependent, with maximized surface/subsurface Cs⁺ concentrations being achieved with the smaller 5 mol% Cs system. These characteristics directly correlate improved surface passivation and environmental stability of the triple cation system. These triple cation nanocrystals exhibit a maximum photoluminescence quantum yield of ∼93% which upon translation to nanocrystalline LED devices delivers a maximum EQE of 7.4% (30 cd A⁻¹) corresponding to a power efficiency of 34.87 lm W⁻¹. This performance represents a marked improvement compared to CsPbBr₃ nanocrystals (PL quantum yield ∼50%; maximum EQE of 2.5% (7.2 cd A⁻¹)) fabricated under similar conditions.

中文翻译：

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研究三阳离子钙钛矿纳米晶体在发光二极管中的结构-功能关系

有机金属卤化物钙钛矿纳米晶体因其窄的发射带宽，高的光致发光量子产率（PLQY）和颜色可调性而成为发光二极管的有希望的候选者。然而，这些系统具有热不稳定性，相杂质和对加工技术的敏感性。这项研究报告了首次合成具有标称化学计量比Cs _x（MA _0.17 FA _0.83）_{1- x} PbBr ₃（x = 0-0.15）的新颖的含Cs三阳离子钙钛矿纳米晶体。使用衍射，显微镜和固态MAS NMR技术彻底研究了Cs ⁺阳离子掺入的作用。固态¹³³ Cs MAS NMR结果表明，Cs ⁺阳离子的分布高度依赖于浓度和粒径，使用较小的5 mol％Cs体系可获得最大的表面/表面Cs ⁺浓度。这些特性直接与改善的表面钝化和三阳离子体系的环境稳定性相关。这些三阳离子纳米晶体显示出约93％的最大光致发光量子产率，转化为纳米晶体LED器件后可提供7.4％（30 cd A ^-1）的最大EQE，对应于34.87 lm W ^-1的功率效率。与CsPbBr ₃相比，该性能有了显着提高。在类似条件下制造的纳米晶体（PL量子产率约50％；最大EQE为2.5％（7.2 cd A ^-1））。