Synthesis of Stable SnI2·xDMSO Adducts toward Efficient Tin–Lead Perovskite Solar Cells

Sn–Pb narrow-bandgap perovskites are indispensable for achieving highly efficient all-perovskite tandem solar cells as bottom subcells. However, facile oxidation of Sn 2+ into Sn 4+ leads to the poor precursor stability, which largely hinders the development of Sn–Pb perovskite solar cells (PSCs). Herein, we present a novel strategy to synthesize SnI 2 · x DMSO intermedium adducts in situ utilizing a mild one-to-one reaction between molecular SnI 4 and metallic Sn. This approach avoids the formation of low-coordinated SnI 2 · x DMSO clusters ( x ≤ 2), yielding highly coordinated SnI 2 · x DMSO ( x = 3) adducts with enhanced antioxidation ability. The resultant precursor showed outstanding stability and reproducibility. The aged precursor for 7 days maintains its initial properties. Consequently, the resulting Sn–Pb PSCs deliver an impressive efficiency of 22.64% and retain ∼ 90% of their initial value after maximum power point operation under simulated one-sun illumination in air for 530 h under encapsulation. Our finding provides an effective pathway to enhance the intrinsic antioxidant capacity of Sn 2+ in perovskite precursors, paving a way for the development of efficient and reproducible Sn–Pb PSCs.