The　poor　crystallinity　of　Sn-alloyed　perovskite　films　and　the　easy　oxidation　of　Sn2+　are　major　obstacles　to　the　realization　of　efficient　and　stable　Sn-Pb　perovskite　solar　cells　(PSCs).　Here,　we　propose　a　metalorganic　Sn(II)　additive,　stannous　octoate　(SnOct2),　to　prepare　high-quality　FA0.8MA0.2Pb0.5Sn0.5I3　films.　Through　experimental　and　computational　methods,　we　have　demonstrated　the　existence　of　a　strong　coordination　interaction　between　Sn2+　and　Oct−　ions.　This　interaction　effectively　suppresses　the　oxidation　of　surface　Sn2+　by　oxygen.　Simultaneously,　Oct−　ions　exhibit　a　significant　passivation　effect　on　inhibiting　the　formation　of　iodine　vacancies,　effectively　enhances　the　grain　size,　reduces　the　non-radiative　carrier　recombination　within　the　device,　and　ultimately,　leads　to　improved　performance　and　stability　of　the　PSCs.　With　the　addition　of　SnOct2,　the　optimal　power　conversion　efficiency　of　Sn-Pb　alloyed　PSCs　was　increased　from　19.18　%　to　23.12　%.　The　unencapsulated　solar　cells　maintains　83　%　of　the　initial　efficiency　after　1000　h　of　storage　in　N2,　or　43　%　of　the　initial　efficiency　after　500　h　of　storage　in　ambient　atmosphere,　respectively.　This　work　presents　the　promising　future　of　metalorganic　Sn(II)　as　effective　and　ecofriendly　additives　in　manufacturing　Sn-based　PSCs.　©　2025　Elsevier　Ltd