Ruddlesden–Popper layered perovskites have emerged as a promising solution for overcoming the moisture instability of three-dimensional hybrid perovskite materials. Given that the optoelectronic properties of these layered perovskites strongly depend on the dimensionality (n) of the phases present, understanding of the microstructure and order in such materials is important. Typically, the dimensionality of phases present is inferred from optical measurements rather than diffraction measurements which are a more direct probe of structural order. Here we use a combination of grazing-incidence transmission wide-angle X-ray scattering and transmission wide-angle X-ray scattering techniques to probe the in-plane microstructure of highly textured Ruddlesden–Popper hybrid perovskite films with a target dimensionality of n = 4. By being able to resolve the in-plane diffraction peaks corresponding to the periodic repeating of layered phases that are often obscured by the substrate horizon in grazing incidence measurements, we are able to directly characterise structural order in such films. Despite having a target dimensionality of n = 4, only diffraction peaks corresponding to n = 2, 3 and ∞ phases are observed. Observations from X-ray measurements are combined with optical absorption measurements to show that there is increasing structural disorder in low-n phases with increasing dimensionality. Further analysis of peak positions and peak widths in the X-ray scattering patterns indicate that stacking fault defects are the origin of structural disorder in layered perovskite films, with increasing disorder with increasing n. We also present a complete indexing of grazing-incidence wide-angle X-ray scattering patterns of highly textured layered perovskite films and confirm the structurally ordered n = 3 and ∞ phases as the dominant crystalline phases in such films. This work provides guidance for the reliable characterisation of structural order and orientation in layered perovskite thin films from X-ray scattering measurements which will assist with assessing n-phase purity and photovoltaic device optimisation.

中文翻译：

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通过X射线散射测量直接评估层状混杂钙钛矿薄膜的结构顺序和堆叠缺陷的证据

Ruddlesden-Popper层状钙钛矿已经成为克服三维杂化钙钛矿材料水分不稳定性的有前途的解决方案。鉴于这些层状钙钛矿的光电性质强烈依赖于维数（n在目前的阶段中，了解此类材料的微观结构和顺序非常重要。通常，存在的相的尺寸是从光学测量而不是衍射测量中推断的，后者是结构顺序的更直接的探针。在这里，我们结合使用掠入射透射广角X射线散射和透射广角X射线散射技术来探测目标尺寸为n的高度织构的Ruddlesden-Popper混合钙钛矿薄膜的面内微观结构＝ 4。通过能够解决与层相的周期性重复相对应的面内衍射峰，所述层相的周期性重复在掠入射测量中经常被衬底水平掩盖，我们能够直接表征这种膜的结构顺序。尽管目标尺寸为n = 4，但仅观察到与n = 2、3和∞相相对应的衍射峰。X射线测量的观察结果与光吸收测量结果相结合，表明低n相的尺寸增加。对X射线散射图谱中峰位置和峰宽的进一步分析表明，堆垛层错缺陷是钙钛矿层状膜结构无序的根源，随着n的增加，无序性增加。我们还提出了高度织构化钙钛矿薄膜的掠入射广角X射线散射图的完全索引，并确认了结构有序的n = 3和∞相为此类薄膜中的主要结晶相。这项工作为从X射线散射测量中可靠地表征层状钙钛矿薄膜的结构顺序和取向提供了指导，这将有助于评估n相纯度和光伏器件的优化。