Halide perovskites are excellent candidate materials for use in solar cell, LED, and detector devices, in part because their composition can be tuned to achieve ideal optoelectronic properties. Empirical efficiency optimization has led the field toward compositions rich in FA (formamidinium) on the A-site and I on the X-site, with additional small amounts of MA (methylammonium) or Cs A-site cations and Br X-site anions. However, it is not clear how and why the specific compositions of alloyed, that is, mixed component, halide perovskites relate to photo-stability of the materials. Here, this work combines synchrotron grazing incidence wide-angle X-ray scattering, photoluminescence, high-resolution scanning electron diffraction measurements and theoretical modelling to reveal the links between material structure and photostability. Namely, this work finds that increased octahedral titling leads to improved photo-stability that is correlated with lower densities of performance-harming hexagonal polytype impurities. These results uncover the structural signatures underpinning photo-stability and can therefore be used to make targeted changes to halide perovskites, bettering the commercial prospects of technologies based on these materials.

中文翻译：

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组成决定了卤化物钙钛矿的八面体倾斜和光稳定性


卤化物钙钛矿是用于太阳能电池、LED 和探测器设备的优秀候选材料，部分原因是它们的成分可以调整以实现理想的光电特性。经验效率优化已引导该领域开发出在 A 位上富含 FA（甲脒）、在 X 位上富含 I 的组合物，以及额外少量的 MA（甲基铵）或 Cs A 位阳离子和 Br X 位阴离子。然而，尚不清楚合金化（即混合成分）卤化物钙钛矿的具体成分如何以及为何与材料的光稳定性相关。在这里，这项工作结合了同步加速器掠入射广角 X 射线散射、光致发光、高分辨率扫描电子衍射测量和理论建模，揭示了材料结构和光稳定性之间的联系。也就是说，这项工作发现增加八面体标题会改善光稳定性，这与损害性能的六方多型杂质的较低密度相关。这些结果揭示了支撑光稳定性的结构特征，因此可用于对卤化物钙钛矿进行有针对性的改变，从而改善基于这些材料的技术的商业前景。