Concurrent cationic and anionic perovskite defect passivation enables 27.4% perovskite/silicon tandems with suppression of halide segregation

Summary Stable and efficient perovskite/silicon tandem solar cells require defect passivation suppression of light-induced phase segregation the wide-band-gap perovskite. Here, we report how molecules containing both electron-rich electron-poor moieties, such as phenformin hydrochloride (PhenHCl), can satisfy requirements, independent perovskite's surface chemical composition its grain boundaries interfaces. PhenHCl-passivated (?1.68 eV) perovskite p-i-n single-junction deliver an open-circuit voltage (VOC) ?100 mV higher than control devices, resulting in power conversion efficiencies (PCEs) up to 20.5%. These devices do not show any VOC losses after more 3,000 h thermal stress at 85°C a nitrogen ambient. Moreover, PhenHCl improves PCE textured from 25.4% 27.4%. Our findings provide critical insights for improved metal halide surfaces fabrication highly stable perovskite-based cells.