Expanding the low-dimensional interface engineering toolbox for efficient perovskite solar cells

Three-dimensional/low-dimensional perovskite solar cells afford improved efficiency and stability. The design of low-dimensional capping materials is constrained to tuning the A-site organic cation, as Pb 2+ and Sn 2+ are the only options for the metal cation. Here we unlock access to a library of low-dimensional capping materials with metal cations beyond Pb 2+ /Sn 2+ by processing a full precursor solution containing both metal and ammonium halides. This enables easier synthetic control of the low-dimensional capping layer and greater versatility for low-dimensional interface engineering. We demonstrate that a zero-dimensional zinc-based halogenometallate (PEA 2 ZnX 4 ; PEA = phenethylammonium, X = Cl/I) induces more robust surface passivation and stronger n–N isotype three-dimensional/low-dimensional heterojunctions than its lead-based counterpart. We exhibit p–i–n solar cells with 24.1% efficiency (certified 23.25%). Our cells maintain 94.5% initial efficiency after >1,000 h of operation at the maximum power point. Our findings expand the material library for low-dimensional interface engineering and stabilization of highly efficient three-dimensional/low-dimensional perovskite solar cells. The design of low-dimensional interface materials for perovskite solar cells is limited in the choice of the metal cation. By processing metal and ammonium halides together, Ye et al. expand the metal cation library for these interface materials.