The open circuit voltage (V_OC) deficit in perovskite solar cells (PSCs) is greater in wide bandgap (>1.7 eV) cells than in ~1.5 eV perovskites.^1,2 Quasi-Fermi level splitting (QFLS) measurements reveal V_OC-limiting recombination at the electron transport layer (ETL) contact.^3-5 This, we find, stems from inhomogeneous surface potential and poor perovskite-ETL energetic alignment. Common monoammonium surface treatments fail to address this; instead we introduce diammonium molecules to modify the perovskite surface states and achieve a more uniform spatial distribution of surface potential. Using 1,3-propane diammonium (PDA), QFLS increases by 90 meV, enabling 1.79 eV PSCs with a certified 1.33 V V_OC, and > 19% power conversion efficiency (PCE). Incorporating this layer into a monolithic all-perovskite tandem, we report a record V_OC of 2.19 V (89% of the detailed balance V_OC limit) and > 27% PCE (26.3% certified quasi-steady-state). These tandems retain more than 86% of their initial PCE after 500 hrs operation.

_{钙钛矿太阳能电池 ( PSC} ) 的开路电压 ( VOC ) 缺陷在宽带隙 (>1.7 eV) 电池中比在 ~1.5 eV 钙钛矿电池中更大。^1,2准费米能级分裂 (QFLS) 测量揭示了电子传输层 (ETL) 接触处的VOC_{限制复合。}^3-5我们发现，这是由于表面电势不均匀和钙钛矿-ETL 能量排列不良造成的。常见的一铵表面处理无法解决这个问题；相反，我们引入二铵分子来改变钙钛矿表面状态并实现更均匀的表面电势空间分布。_{使用 1,3-丙烷二铵(} PDA)，QFLS 提高了 90 meV，从而实现了 1.79 eV PSC，具有经过认证的 1.33 V VOC和 > 19% 的功率转换效率 (PCE)。将该层合并到单片全钙钛矿串联中，我们报告了创纪录_{的2.19 V} VOC（详细平衡VOC限值的 89%）和_> 27% PCE（26.3% 经认证的准稳态）。这些串联在运行 500 小时后仍保留其初始 PCE 的 86% 以上。