Oxygen ingression has been shown to substantially decrease the carrier lifetime of Sn-based perovskites, behind which the mechanism remains yet unknown. Our first-principles calculations reveal that in prototypical MASnI₃ (MA = CH₃NH₃), oxygen by itself is not a recombination center. Instead, it tends to form substitutional O_I through combining with native I vacancies (V_I) and remarkably increases the original recombination rate of V_I by 2–3 orders of magnitude. This rationalizes the experimentally observed sharp decline of carrier lifetime in perovskites exposed to air. The significantly enhanced carrier recombination is due to a smaller electron capture barrier of O_I, resulting from lattice strengthening and the suppressed structural relaxation upon electron capture. These insights offer a route to further improve device performance via anion engineering in broad Sn-based perovskite optoelectronics operating in ambient air. Moreover, our results highlight the important role of lattice relaxation for nonradiative carrier capture in materials in general.

中文翻译：

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杂化锡钙钛矿中氧诱导增强非辐射载流子复合的起源

氧气进入已被证明会大大降低锡基钙钛矿的载流子寿命，其背后的机制仍然未知。我们的第一性原理计算表明，在原型 MASnI ₃ (MA = CH ₃ NH ₃ ) 中，氧本身不是重组中心。相反，它倾向于通过与天然 I 空位 (V _I ) 结合形成替代 O _{I ，并显着提高 V I}的原始重组率2-3 个数量级。这合理化了实验观察到的暴露在空气中的钙钛矿载流子寿命的急剧下降。显着增强的载流子复合是由于 O _{I的电子捕获势垒较小}，由晶格强化和电子捕获时抑制的结构松弛引起。这些见解提供了一条途径，通过在环境空气中运行的广泛的 Sn 基钙钛矿光电子学中的阴离子工程进一步提高设备性能。此外，我们的结果突出了晶格弛豫对一般材料中非辐射载流子捕获的重要作用。