The prejudicial defects accumulated at the grain boundaries and surface are one of the most important reasons that cause perovskite solar cells (PSCs) to deviate from the theoretical Shockley–Queisser efficiency limit and poor stability. Consequently, it is highly desirable to reduce defect densities of the polycrystalline perovskite film through manipulating perovskite crystallization and introducing passivation strategy. Herein, the synergistic effects of cesium trifluoroacetate (Cs-TFA) as a novel additive are demonstrated, where it not only provides cesium cations (stabilizer) for perovskite lattice, but also can simultaneously modulate crystal growth and passivate grain boundaries defects. The resultant perovskite films possess more regular morphology, larger grain sizes, and lower defect density. The enlarged crystal grains derive from the incorporation of Cs-TFA that slows down nucleation process, which is demonstrated by in-situ laser confocal photoluminescence imaging. As a result, the encouraging efficiency up to 22.82% is realized for the resulting optimized device. Additionally, the unencapsulated devices sustain around 91% of its initial efficiency after storing 850 h in the air with 40–45% relatively humidity (R.H.) under dark.

在晶界和表面积累的有害缺陷是导致钙钛矿太阳能电池（PSC）偏离理论 Shockley-Queisser 效率极限和稳定性差的最重要原因之一。因此，非常希望通过控制钙钛矿结晶和引入钝化策略来降低多晶钙钛矿薄膜的缺陷密度。本文展示了三氟乙酸铯 (Cs-TFA) 作为一种新型添加剂的协同效应，它不仅为钙钛矿晶格提供铯阳离子（稳定剂），而且可以同时调节晶体生长和钝化晶界缺陷。所得钙钛矿薄膜具有更规则的形态、更大的晶粒尺寸和更低的缺陷密度。扩大的晶粒来源于 Cs-TFA 的掺入，它减缓了成核过程，原位激光共聚焦光致发光成像证明了这一点。结果，优化后的器件实现了高达 22.82% 的令人鼓舞的效率。此外，未封装的设备在黑暗条件下在相对湿度 (RH) 为 40-45% 的空气中储存 850 小时后，仍能维持约 91% 的初始效率。