Ozone Treatment of SnO₂ from Oxidating DC-Sputtered Metallic Tin (Sn) for Efficient and Stable Perovskite Solar Cells

Tin dioxide (SnO₂) has emerged as an ideal premier electron transport layer (ETL) material for perovskite solar cells (PSCs) due to its exceptional optical transparency and high electron mobility. Among all of the deposition techniques, magnetron sputtering represents as one of the most mature mass productive processes. This work reports a cost-effective method for fabricating a SnO₂ ETL via direct current (DC) sputtering metallic Sn target followed by thermal oxidation in ambient air, which simultaneously enhanced deposition rates for industrial-scale production and reduced target poisoning risks associated with reactive sputtering. Furthermore, we implemented an industrially compatible ultraviolet-ozone (UV-O₃) treatment strategy to further reduce surface oxygen vacancies (V_O) defects at the SnO₂ surface while optimizing the ETL/perovskite interface through improving energy level alignment, promoting preferential crystal orientation of perovskite films, and enhancing charge extraction efficiency. As a result, the UV-O₃-treated SnO₂-based device delivered a power conversion efficiency (PCE) of 21.17%, which is among the top-performing devices utilizing DC magnetron-sputtered SnO₂ as the ETL. In addition, the unencapsulated devices retained approximately 90% of initial PCE after 1300 h of storage at ∼20% relative humidity, demonstrating their excellent environmental stability. This work provides a straightforward, economical, and effective approach to advance SnO₂ ETL implementation for commercial PSC applications.