Surface passivation via post-treatment is an important strategy for improving power conversion efficiency and operational stability of perovskite solar cells. However, so far the interaction mechanisms between passivating additive and perovskite are not well understood. Here, we report the atomic-scale interaction of surface passivating additive 2,2-difluoroethylammonium bromine (2FEABr) on the MAPbI₃. It is found that the bulky 2FEA⁺ cations tend to distribute at film surface, while the Br⁻ anions diffuse from surface into bulk. A combination of ¹⁹F, ²⁰⁷Pb, and ²H solid-state NMR further reveal the Br⁻ anions’ partial substitution for the I⁻ sites, the restricted motion of partial MA⁺ cations, and the firmed perovskite lattices, which would improve charge transport and stability of the perovskite films. Optical spectroscopy and ultraviolet photoelectron spectroscopy demonstrate that the 2FEABr induced surface passivation and energetic modification suppress the nonradiative recombination loss. These findings enable the efficiency of the p-i-n structured PSC significantly increasing from 19.44 to 21.06%, accompanied by excellent stability. Our work further establishes more knowledge link between passivating additive and PSC performance.

通过后处理进行表面钝化是提高钙钛矿太阳能电池能量转换效率和运行稳定性的重要策略。然而，到目前为止，钝化添加剂和钙钛矿之间的相互作用机制还不是很清楚。_{在这里，我们报告了表面钝化添加剂 2,2-二氟乙基溴铵 (2FEABr) 在 MAPbI 3}上的原子级相互作用。结果发现，大体积的 2FEA ⁺阳离子倾向于分布在薄膜表面，而 Br ^-阴离子则从表面扩散到体积中。¹⁹ F、²⁰⁷ Pb 和² H 固态 NMR的组合进一步揭示了 Br ^-阴离子部分取代 I ^-位点、部分 MA ⁺阳离子的受限运动和坚固的钙钛矿晶格，这将改善钙钛矿薄膜的电荷传输和稳定性。光学光谱和紫外光电子能谱表明，2FEABr 诱导的表面钝化和高能修饰抑制了非辐射复合损失。这些发现使p - i - n结构的 PSC 的效率从 19.44 显着提高到 21.06%，同时具有出色的稳定性。我们的工作进一步在钝化添加剂和 PSC 性能之间建立了更多的知识联系。