Inhibiting Ion Migration and Oxidation in Sn–Pb Perovskite by Multidentate Chelating Additive Strategy

Abstract Currently, all‐perovskite tandem solar cells have achieved power conversion efficiencies exceeding 29%. The further improvement is limited by mixed Sn–Pb narrow‐bandgap perovskite subcells. The facile oxidation of Sn²⁺ to Sn⁴⁺ poses an inherent challenge that limits the efficiency and stability of Sn–Pb perovskite solar cells. In this study, a multi‐dentate chelating additive, 3‐amino‐2‐chloroisonicotinamide (ACPC), is developed. Its amino group could anchor I⁻ of the perovskite lattice by hydrogen bonds, thereby preventing I⁻ migration and oxidation. On the other hand, the carbonyl group of ACPC as a Lewis base group could coordinate with Sn²⁺, effectively protecting Sn²⁺ from oxidation. Ultimately, the multi‐dentate chelating effect of ACPC helps to suppress the oxidation of Sn–Pb perovskite and its related nonradiative recombination. The resulting Sn–Pb perovskite solar cells obtain a top power‐conversion efficiency (PCE) of 23.09% and a high open‐circuit voltage (V_OC) of 0.902 V while the control values only reach 19.11% and 0.825 V. As a result of the improved performance of the Sn–Pb perovskite solar cells, the corresponding all‐perovskite tandem solar cells achieve a PCE of 27.60%, retaining 85.7% of initial PCE after 500 h continuous 1 sun illumination.