Lead-halide perovskites increasingly mesmerize researchers because they exhibit a high degree of structural defects and dynamics yet nonetheless offer an outstanding (opto)electronic performance on par with the best examples of structurally stable and defect-free semiconductors. This highly unusual feature necessitates the adoption of an experimental and theoretical mindset and the reexamination of techniques that may be uniquely suited to understand these materials. Surprisingly, the suite of methods for the structural characterization of these materials does not commonly include nuclear magnetic resonance (NMR) spectroscopy. The present study showcases both the utility and versatility of halide NMR and NQR (nuclear quadrupole resonance) for probing the structure and structural dynamics of CsPbX₃ (X = Cl, Br, I), in both bulk and nanocrystalline forms. The strong quadrupole couplings, which originate from the interaction between the large quadrupole moments of, e.g., the ³⁵Cl, ⁷⁹Br, and ¹²⁷I nuclei, and the local electric-field gradients, are highly sensitive to subtle structural variations, both static and dynamic. The quadrupole interaction can resolve structural changes with accuracies commensurate with synchrotron X-ray diffraction and scattering. It is shown that space-averaged site-disorder is greatly enhanced in the nanocrystals compared to the bulk, while the dynamics of nuclear spin relaxation indicates enhanced structural dynamics in the nanocrystals. The findings from NMR and NQR were corroborated by ab initio molecular dynamics, which point to the role of the surface in causing the radial strain distribution and disorder. These findings showcase a great synergy between solid-state NMR or NQR and molecular dynamics simulations in shedding light on the structure of soft lead-halide semiconductors.

中文翻译：

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卤化物磁共振观察到的块状和纳米晶铯卤化铅钙钛矿。

钙钛矿卤化钙越来越吸引研究人员，因为它们表现出高度的结构缺陷和动力学特性，但仍具有与结构稳定且无缺陷的半导体的最佳实例相当的出色的（光电）电子性能。这种非常不寻常的功能需要采用实验和理论上的思维方式，并且需要重新审查可能独特地适合于理解这些材料的技术。令人惊讶地，用于这些材料的结构表征的方法套件通常不包括核磁共振（NMR）光谱。本研究展示了卤化物NMR和NQR（核四极共振）在探测CsPbX ₃的结构和结构动力学方面的实用性和多功能性（X = Cl，Br，I），均为块状和纳米晶形式。强大的四极耦合源于³⁵ Cl，⁷⁹ Br和¹²⁷ I原子核的大四极矩与局部电场梯度之间的相互作用，因此对微小的结构变化（静态和静态）高度敏感。动态。四极相互作用可以解析结构变化，其精度与同步加速器X射线衍射和散射相当。结果表明，与本体相比，纳米晶体的空间平均位错大大增强，而核自旋弛豫的动力学表明纳米晶体的结构动力学增强。从头算证实了NMR和NQR的发现分子动力学，指出表面在引起径向应变分布和无序中的作用。这些发现证明了固态NMR或NQR与分子动力学模拟在软卤化铅半导体结构上的巨大协同作用。