Nanoscale Local Contacts Enable Inverted Inorganic Perovskite Solar Cells with 20.8 % Efficiency

Abstract Inorganic perovskite solar cells (IPSCs) have gained significant attention due to their excellent thermal stability and suitable band gap (~1.7 eV) for tandem solar cell applications. However, the defect‐induced non‐radiative recombination losses, low charge extraction efficiency, energy level mismatches, and so on render the fabrication of high‐efficiency inverted IPSCs remains challenging. Here, the use of 3‐amino‐5‐bromopyridine‐2‐formamide (ABF) in methanol was dynamically spin‐coated on the surface of CsPbI 2.85 Br 0.15 film, which facilitates the limited etching of defect‐rich subsurface layer, resulting in the formation of vertical PbI 2 nanosheet structures. This enabled localized contacts between the perovskite film and the electron transport layer, suppress the recombination of electron‐hole and beneficial to electron extraction. Additionally, the C=O and C=N groups in ABF effectively passivated the undercoordinated Pb 2+ at grain boundaries and on the surface of CsPbI 2.85 Br 0.15 film. Eventually, we achieved a champion efficiency of 20.80 % (certified efficiency of 20.02 %) for inverted IPSCs with enhanced stability, which is the highest value ever reported to date. Furthermore, we successfully prepared p‐i‐n type monolithic inorganic perovskite/silicon tandem solar cells (IPSTSCs) with an efficiency of 26.26 %. This strategy provided both fast extraction and efficient passivation at the electron‐selective interface.