B‐Site Co‐Doping Coupled with Additive Passivation Pushes the Efficiency of Pb–Sn Mixed Inorganic Perovskite Solar Cells to Over 17%

Abstract Pb–Sn mixed inorganic perovskite solar cells (PSCs) have garnered increasing interest as a viable solution to mitigate the thermal instability and lead toxicity of hybrid lead‐based PSCs. However, the relatively poor structural stability and low device efficiency hinder its further development. Herein, high‐performance manganese (Mn)‐doped Pb–Sn–Mn‐based inorganic perovskite solar cells (PSCs) are successfully developed by introducing Benzhydroxamic Acid (BHA) as multifunctional additive. The incorporation of smaller divalent Mn cations contributes to a contraction of the perovskite crystal, leading to an improvement in structural stability. The BHA additive containing a reductive hydroxamic acid group (O═C–NHOH) not only mitigates the notorious oxidation of Sn 2+ but also interacts with metal ions at the B‐site and passivates related defects. This results in films with high crystallinity and low defect density. Moreover, the BHA molecules tend to introduce a near‐vertical dipole moment that parallels the built‐in electric field, thus facilitating charge carrier extraction. Consequently, the resulting device delivers a champion PCE as high as 17.12%, which represents the highest reported efficiency for Pb–Sn‐based inorganic PSCs thus far. Furthermore, the BHA molecule provides an in situ encapsulation of the perovskite grain boundary, resulting in significant enhancement of device air stability.