Dual-Stage Reduction Strategy of Tin Perovskite Enables High Performance Photovoltaics

The rapid oxidation of Sn²⁺ in tin-based perovskite solar cells (TPSCs) restricts their efficiency and stability have been main bottleneck towards further development. This study developed a novel strategy which utilizes thiosulfate ions (S₂O₃ ^2-) in the precursor solution to enable a dual-stage reduction process. In the solution stage, thiosulfate acted as an efficacious reducing agent to reduce Sn⁴⁺ to Sn²⁺, meanwhile, its oxidation products were able to reduce I₂ to I^- during the film stage. This dual reduction ability effectively inhibited the oxidation of Sn²⁺ and passivated defects, further promising an excellent stability of the perovskite devices. As a result, thiosulfate-incorporated devices achieved a high efficiency of 14.78 % with open-circuit voltage reaching 0.96 V. The stability of the optimized devices achieved a remarkable improvement, maintaining 90 % of their initial efficiencies after 628 hours at maximum-power-point (MPP). The findings provid research insights and experimental data support for the sustained dynamic reduction in TPSCs.