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 (S2O32−) 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. This study firstly proposes sustained dynamic reduction using a dual‐stage reduction strategy to fabricate devices of high efficiency and long‐term stability. Ultimately, a champion power conversion efficiency of 14.78 % and 90 % of initial efficiency after 628 h at maximum power.