Perovskite‐based photovoltaics (PVs) have garnered tremendous interest, enabling power conversion efficiencies exceeding 25%. Although much of this success is credited to the exploration of new compositions, defects passivation and process optimization, environmental stability remains an important bottleneck to be solved. The underlying mechanisms of thermal and humidity‐induced degradation are still far from a clear understanding, which poses a severe limitation to overcome the stability issues. Herein, in situ X‐ray diffraction (XRD), in operando liquid‐cell transmission electron microscopy (TEM) and ex situ solid‐state (ss)NMR spectroscopy are combined with time‐resolved spectroscopies to reveal new insights about the degradation mechanisms of methylammonium lead halide (MAPbI₃) under 85% relative humidity (RH) at different length scales. Liquid‐cell TEM enables the live visualizations from meso‐to‐nanoscale transformation between the perovskite particles and water molecules, which are corroborated by the changes in local structures at sub‐nanometer distances by ssNMR and longer range by XRD. This work clarifies the role of surface defects and the significance of their passivation to prevent hydration and decomposition reactions.

中文翻译：

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控制湿度下甲基铵卤化铅钙钛矿表面缺陷与稳定性之间相关性的分子级洞察

基于钙钛矿的光伏 (PV) 引起了极大的兴趣，使功率转换效率超过 25%。尽管这一成功在很大程度上归功于对新成分的探索、缺陷钝化和工艺优化，但环境稳定性仍然是一个需要解决的重要瓶颈。热和湿度诱导降解的潜在机制仍远未明确，这对克服稳定性问题构成了严重限制。在此，原位 X 射线衍射 (XRD)、原位液体细胞透射电子显微镜 (TEM) 和非原位固态 (ss) NMR 光谱与时间分辨光谱相结合，揭示了对降解机制的新见解。甲基铵卤化铅 (MAPbI ₃) 85% 相对湿度 (RH) 下的不同长度尺度。液态细胞 TEM 可以实时显示钙钛矿颗粒和水分子之间从中尺度到纳米尺度的转变，这得到了 ssNMR 亚纳米距离局部结构变化和 XRD 更远距离局部结构变化的证实。这项工作阐明了表面缺陷的作用及其钝化对防止水化和分解反应的重要性。