Metal halide perovskites (MHPs) have gained considerable attention due to their excellent optoelectronic performance, which is often attributed to unusual defect properties. We demonstrate that midgap defect levels can exhibit very large and slow energy fluctuations associated with anharmonic acoustic motions. Therefore, care should be taken classifying MHP defects as deep or shallow, since shallow defects may become deep and vice versa. As a consequence, charges from deep levels can escape into bands, and light absorption can be extended to longer wavelengths, improving material performance. The phenomenon, demonstrated with iodine vacancy in CH₃NH₃PbI₃ using a machine learning force field, can be expected for a variety of defects and dopants in many MHPs and other soft inorganic semiconductors. Since large-scale anharmonic motions can be precursors to chemical decomposition, a known problem with MHPs, we propose that materials that are stiffer than MHPs but softer than traditional inorganic semiconductors, such as Si and TiO₂, may simultaneously exhibit excellent performance and stability.

中文翻译：

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金属卤化物钙钛矿中缺陷水平在 100 ps 时间尺度上的电子伏特波动

金属卤化物钙钛矿（MHPs）由于其优异的光电性能而备受关注，这通常归因于不寻常的缺陷特性。我们证明了中间间隙缺陷水平可以表现出与非谐波声学运动相关的非常大且缓慢的能量波动。因此，应注意将 MHP 缺陷分为深缺陷或浅缺陷，因为浅缺陷可能会变深，反之亦然。因此，来自深能级的电荷可以逃逸到能带中，光吸收可以扩展到更长的波长，从而提高材料性能。该现象以 CH ₃ NH ₃ PbI _{3中的碘空位证明}使用机器学习力场，可以预期许多 MHP 和其他软无机半导体中的各种缺陷和掺杂剂。由于大规模非谐运动可能是化学分解的前兆，这是 MHP 的一个已知问题，我们建议比 MHP 更硬但比传统无机半导体（如 Si 和 TiO ₂）更柔软的材料可以同时表现出优异的性能和稳定性。