Single crystal CH₃NH₃PbBr₃ samples are exposed to light illumination, with a light intensity about seven times stronger than the sun while under ultrahigh vacuum (UHV) conditions, in order to investigate their chemical and structural stability from prolonged light illumination. X‐ray photoemission spectroscopy measurements show that within 10 h of illumination, about half of the initial C, N, and Br elemental concentrations leave the surface and about half of the perovskite's Pb is converted into metallic Pb. Light exposures while in the UHV system also significantly roughen the surface, and surprisingly, empty voids form ≈1 to 3 µm down in the light exposed region. A framework based on the Kirkendall effect is put forward to explain the observed void formation. This proposed model may be relevant to the slow degradation of perovskite solar cells, which is sometimes attributed to irreversible chemical reactions from undesired diffusion. These measurements and observations reveal the intrinsic behavior of the CH₃NH₃PbBr₃ single crystals under light illumination while in a UHV system where volatile species are free to leave, in contrast to existing device studies on the photostability of perovskite solar cells.

中文翻译：

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CH3NH3PbBr3单晶在光照下的本征行为

单晶CH ₃ NH ₃ PbBr ₃样品在超高真空（UHV）条件下暴露于光照射下，其光强度比太阳强约7倍，以便通过长时间的光照来研究其化学和结构稳定性。X射线光电子能谱测量表明，在照射后10小时内，约有一半的初始C，N和Br元素浓度离开表面，约一半的钙钛矿Pb转化为金属Pb。在UHV系统中，曝光也会使表面显着粗糙，令人惊讶的是，在曝光区域中空的空隙向下形成了约1至3 µm。提出了基于柯肯德尔效应的框架来解释观察到的空隙形成。该提出的模型可能与钙钛矿太阳能电池的缓慢降解有关，有时归因于不希望的扩散引起的不可逆的化学反应。这些测量和观察揭示了CH的内在行为与现有的钙钛矿型太阳能电池光稳定性的装置研究不同，UHV系统中的₃ NH ₃ PbBr ₃单晶在光照下仍可自由挥发。