crystallization caused low-quality films and Sn 2+ oxidation induced p-doping. [4,5] These are accompanied by defects generated in perovskites, which always leads to quick reduction of the PCE and durability of tin-lead PSCs. [6] Tremendous efforts have been made to reduce the intrinsic defects in Sn-Pb PSCs by developing perovskite processing methods and customizing additives. [7][8][9][10] With advances in past years, the PCE of Sn-Pb PSCs has been elevated to more than 23%, which is still smaller but close to the Pb-based counterparts. [11,12] However, much larger challenges remain in the long-term stability of Sn-Pb PSCs.One concerning observation is that Sn-Pb perovskite photovoltaic devices still degrade much faster under light than Pb perovskites even when they are stored in inert condition or fully encapsulated to separate moisture and oxygen. [13] Recent studies show that they are not only caused

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