Combining wide-bandgap and narrow-bandgap perovskites to construct monolithic all-perovskite tandem solar cells offers avenues for continued increases in photovoltaic (PV) power conversion efficiencies (PCEs). However, actual efficiencies today are diminished by the subpar performance of narrow-bandgap subcells. Here we report a strategy to reduce Sn vacancies in mixed Pb–Sn narrow-bandgap perovskites that use metallic tin to reduce the Sn⁴⁺ (an oxidation product of Sn²⁺) to Sn²⁺ via a comproportionation reaction. We increase, thereby, the charge-carrier diffusion length in narrow-bandgap perovskites to 3 μm for the best materials. We obtain a PCE of 21.1% for 1.22-eV narrow-bandgap solar cells. We fabricate monolithic all-perovskite tandem cells with certified PCEs of 24.8% for small-area devices (0.049 cm²) and of 22.1% for large-area devices (1.05 cm²). The tandem cells retain 90% of their performance following 463 h of operation at the maximum power point under full 1-sun illumination.

结合带隙钙钛矿和窄带隙钙钛矿以构建整体式全钙钛矿串联太阳能电池为光伏（PV）功率转换效率（PCE）的持续提高提供了途径。但是，如今的实际效率因窄带隙子电池的出色性能而降低。此处我们报告一个策略，以降低在混合的Pb-Sn锡空缺窄带隙使用金属锡以降低的Sn的钙钛矿⁴⁺（Sn的氧化产物²⁺）至Sn ²⁺通过相称反应。因此，对于最佳材料，我们将窄带隙钙钛矿中的载流子扩散长度增加到3μm。对于1.22 eV的窄带隙太阳能电池，我们获得21.1％的PCE。我们制造的整体钙钛矿串联电池的认证PCE对于小面积设备（0.049 cm ²）为24.8％，对于大面积设备（1.05 cm ²）为22.1％。串联电池在全日照下在最大功率点运行463小时后，仍能保持90％的性能。