SnO₂ Interacted with Sodium Thiosulfate for Perovskite Solar Cells over 25% Efficiency

Tin oxide (SnO₂) as electron transportation layer (ETL) has demonstrated remarkable performance applied in perovskite solar cells but still accommodated a host of defects such as oxygen vacancies, uncoordinated Sn⁴⁺ , and absorbed hydroxyl groups. Here, we use inorganic sodium thiosulfate Na₂S₂O₃ to modify SnO₂ nanoparticles in a bulk blending manner. Strong interaction between Na₂S₂O₃ and SnO₂ occurs, as reflected from the elemental chemical state change. The interaction has endowed the SnO₂ film with better uniformity, increased conductivity, and more matched energy level with perovskite. Moreover, the modified SnO₂ film as a substrate could promote the crystallization of perovskite by suppressing unreacted residual PbI₂. The trap density from perovskite bulk to the SnO₂ film across their interface has been effectively reduced, thus inhibiting the nonradiative recombination and promoting the transportation and extraction of charge carriers. Finally, the solar cell based on modified SnO₂ has achieved a champion efficiency of 25.2%, demonstrating the effectiveness and potential of sulfur-containing molecules on optimizing the SnO₂ property.