Organic‐Free and Lead‐Free Perovskite Solar Cells with Efficiency over 11%

Abstract Organic‐free and lead‐free CsSnI₃ perovskite solar cells (PSCs) have recently gained growing attention as a promising template to mitigate the thermal instability and lead toxicity of hybrid lead‐based PSCs. However, the relatively low device efficiency due to the high content of Sn(II)‐related defects hinders its further development. Herein, highly performed CsSnI_3−xBr_x compositional perovskite‐based PSCs are achieved by using dimethyl ketoxime (C₃H₇NO, DMKO) as a multifunctional additive. As a commercially used deoxidant, DMKO can effectively neutralize the oxygen molecule and reduce Sn⁴⁺ back to Sn²⁺, enhancing the oxidation resistance of the film. Besides, the electron‐rich oxime group (NOH) in DMKO tends to interact with Sn²⁺ ions with extremely low adsorption energy less than −15 eV and inhibits defect formation, resulting in films with low defect density. The corresponding PSCs deliver a considerable open‐circuit voltage (V_oc) of 0.75 V with a record efficiency as high as 11.2%, which represents the highest reported efficiency for lead‐free all‐inorganic PSCs thus far. More importantly, the grain surface distributed DMKO provides an in situ encapsulation of the perovskite, which results in greatly enhanced ambient stability of the un‐encapsulated devices.