Power conversion efficiencies of inverted perovskite solar cells (PSCs) based on methylammonium- and bromide-free formamidinium lead triiodide (FAPbI₃) perovskites still lag behind PSCs with a regular configuration. Here we improve the quality of both the bulk and surface of FA_0.98Cs_0.02PbI₃ perovskite films to reduce the efficiency gap. First, we use dibutyl sulfoxide, a Lewis base additive, to improve the crystallinity and reduce the defect density and internal residual stress of the perovskite bulk. Then, we treat the surface of the perovskite film with trifluorocarbon-modified phenethylammonium iodide to optimize the energy levels, passivate defects and protect the film against moisture. The inverted PSCs simultaneously achieve 25.1% efficiency (24.5% from the reverse current–voltage scan measured by a third-party institution) and improved stability. The devices maintained 97.4% and 98.2% of their initial power conversion efficiencies after operating under continuous 1-sun air mass 1.5 G illumination for 1,800 h and under damp heat conditions (85 °C and 85% relative humidity) for 1,000 h, respectively.

基于不含甲基铵和溴化物的甲脒三碘化铅（FAPbI ₃）钙钛矿的倒置钙钛矿太阳能电池（PSC）的功率转换效率仍然落后于常规配置的PSC。_{在这里，我们提高了 FA 0.98} Cs _0.02 PbI ₃的本体和表面质量钙钛矿薄膜可缩小效率差距。首先，我们使用路易斯碱添加剂二丁基亚砜来提高钙钛矿块体的结晶度并降低缺陷密度和内部残余应力。然后，我们用三氟碳改性苯乙基碘化铵处理钙钛矿薄膜的表面，以优化能级、钝化缺陷并保护薄膜免受潮湿。反向 PSC 同时实现了 25.1% 的效率（第三方机构测量的反向电流电压扫描为 24.5%）并提高了稳定性。在连续 1-sun 空气质量 1.5 G 光照下运行 1,800 小时和在湿热条件（85 °C 和 85% 相对湿度）下运行 1,000 小时后，器件分别保持了初始功率转换效率的 97.4% 和 98.2%。