Robust Multi‐Halide Methylammonium‐Free Perovskite Solar Cells on an Inverted Architecture

Abstract Developing efficient wide‐bandgap perovskites is critical to exploit the benefits of a multi‐absorber solar cell and engineering commercially attractive tandem solar cells. Here, a robust, additive‐free, methylammonium‐free triple halide composition for the fabrication of close‐to‐ideal wide‐bandgap perovskites (1.64 eV) is reported. The introduction of low percentages of chloride into the perovskite layer avoided photoinduced halide segregation and lead to an evident improvement in the crystallization process, reaching enhanced open‐circuit voltages as high as 1.23 V. A perovskite of these characteristics is introduced for the first time in a p‐i‐n single‐junction configuration using a self‐assembled monolayer, with devices achieving photoconversion efficiencies of up to 22.6% with ultra‐high stability, retaining ≈80% of their initial efficiency after >1000 h of continuous operation unencapsulated in a nitrogen atmosphere at 85 °C. This result paves the way toward highly efficient multi‐junction tandem solar cells, bringing perovskite technology closer to commercialization.