Stabilizing black-phase (α) FAPbI₃, the most promising candidate for perovskite solar cells (PSCs), has aroused great interest. Although many efforts have been made, such as adopting various primary ammoniums as additives, FAPbI₃ films and PSCs are still fragile in highly humid air. We herein report the use of secondary ammoniums (dimethylammonium (DMA), diethylammonium (DEA) and diisopropylammonium (DiPA)) to stabilize α-FAPbI₃ and elucidate their substituent-dependent distributions and functions in FAPbI₃ films. While the smallest DMA entering the FAPbI₃ lattices is detrimental to humidity stability, the linear DEA and bulky DiPA mainly locating on the surface and at the grain boundary of the FAPbI₃ film, respectively, block water invasion and lead to prominent phase stability under a high relative humidity of 60%∼80%. Moreover, the surface-enriched DEA can efficiently passivate the defects of the FAPbI₃ film, offering efficiencies of 23.38% for PSCs based on a doped hole transport layer (HTL) and 21.14% for those based on a dopant-free HTL with outstanding humidity stability. This work demonstrates that secondary ammoniums with an appropriate molecular configuration can be an effective solution to fortify the phase stability of FAPbI₃ for efficient PSCs.

中文翻译：

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用仲铵稳定潮湿空气中的黑相 FAPbI3

稳定黑相（α）FAPbI ₃是钙钛矿太阳能电池（PSC）最有希望的候选者，引起了极大的兴趣。尽管已经做出了许多努力，例如采用各种初级铵作为添加剂，但 FAPbI ₃薄膜和 PSC 在高度潮湿的空气中仍然很脆弱。我们在此报告了使用仲铵（二甲基铵 (DMA)、二乙基铵 (DEA) 和二异丙基铵 (DiPA)）来稳定 α-FAPbI _{3并阐明它们在 FAPbI 3}薄膜中的取代基依赖性分布和功能。虽然进入 FAPbI ₃晶格的最小 DMA 不利于湿度稳定性，但线性 DEA 和庞大的 DiPA 主要位于 FAPbI 的表面和晶界₃膜分别在 60%∼80% 的高相对湿度下阻止水侵入并导致显着的相稳定性。此外，表面富集的 DEA 可以有效地钝化 FAPbI ₃薄膜的缺陷，基于掺杂空穴传输层 (HTL) 的 PSC 的效率为 23.38%，而基于具有出色湿度的无掺杂 HTL 的 PSC 效率为 21.14%稳定。这项工作表明，具有适当分子构型的仲铵可以成为增强 FAPbI ₃相稳定性以实现高效 PSC 的有效解决方案。