Dipartimento di Scienza e Alta Tecnologia and To.Sca.Lab, Università dell'Insubria , via Valleggio 11, I-22100 Como, Italy.
Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir Prelog Weg 1, CH-8093 Zürich, Switzerland.
ACS Nano. 2017 Apr 25;11(4):3819-3831. doi: 10.1021/acsnano.7b00017. Epub 2017 Apr 14.
Crystal defects in highy luminescent colloidal nanocrystals (NCs) of CsPbX perovskites (X = Cl, Br, I) are investigated. Here, using X-ray total scattering techniques and the Debye scattering equation (DSE), we provide evidence that the local structure of these NCs always exhibits orthorhombic tilting of PbX octahedra within locally ordered subdomains. These subdomains are hinged through a two-/three-dimensional (2D/3D) network of twin boundaries through which the coherent arrangement of the Pb ions throughout the whole NC is preserved. The density of these twin boundaries determines the size of the subdomains and results in an apparent higher-symmetry structure on average in the high-temperature modification. Dynamic cooperative rotations of PbX octahedra are likely at work at the twin boundaries, causing the rearrangement of the 2D or 3D network, particularly effective in the pseudocubic phases. An orthorhombic, 3D γ-phase, isostructural to that of CsPbBr is found here in as-synthesized CsPbI NCs.
高发光胶体纳米晶（NCs）中 CsPbX 钙钛矿（X = Cl、Br、I）的晶体缺陷研究。在这里，我们使用 X 射线总散射技术和 Debye 散射方程（DSE），提供了这些 NCs 的局部结构始终表现出 PbX 八面体在局部有序子域内的正交倾斜的证据。这些子域通过孪晶边界的二维/三维（2D/3D）网络连接，通过该网络，整个 NC 中的 Pb 离子的相干排列得以保留。这些孪晶边界的密度决定了子域的大小，并导致高温变体中平均出现更高对称性的结构。PbX 八面体的动态协同旋转可能在孪晶边界处起作用，导致 2D 或 3D 网络的重新排列，在准立方相中尤为有效。在此，我们在合成的 CsPbI NCs 中发现了与 CsPbBr 同构的正交、三维 γ 相。
