Description:
<jats:title>Abstract</jats:title><jats:p>Power conversion efficiency (PCE) of lead (Pb)‐free tin (Sn)‐based perovskite solar cells (PVSCs) is much lower than that of their Pb‐based counterparts, which is mainly attributed to large open‐circuit voltage (<jats:italic>V</jats:italic><jats:sub>OC</jats:sub>) loss and poor fill factor (FF). In this work, a strategy via vacuum‐assisted treatment of the Sn perovskite layer to self‐heal defects in Sn perovskite is reported, leading to suppression of nonradiative recombination and enhancement of carrier transport capability. Using this method, a maximum PCE of 10.3% is obtained for dual FA‐MA (MA = methylammonium and FA = formamidinium) cation Sn‐based PVSCs with an improved <jats:italic>V</jats:italic><jats:sub>OC</jats:sub> of 0.631 V and FF of 75.5%. This work suggests a facile approach to finely inhibit the defects in the bulk or at interfaces for Sn‐based devices and further facilitate development of highly efficient Sn‐based PVSCs.</jats:p>