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

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 CsSnI3-xBrx 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 ((sic)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.