Robust electron transport layers of SnO₂ for efficient perovskite solar cells: recent advances and perspectives

To date, organic-inorganic hybrid perovskite solar cells (PSCs) have achieved certified efficiencies of 26.1%. Electron transport layers (ETLs) are found to be critical for device performance and stability. The most common ETL material is TiO₂. However, it suffers from low efficiency for charge extraction at the interface, especially in planar solar cells. SnO₂ has similar physical properties to TiO₂ and has higher electron mobility, which could improve the charge extraction ability of the interface. In addition, SnO₂ has the advantages of low cost, low preparation temperature, and a wide band gap, which makes SnO₂ gradually become a stable ETL for high-efficiency PSCs. This article examines the current use of SnO₂ as an ETL material in PSCs, covering the preparation procedure and SnO₂ performance enhancement technologies. The stability of SnO₂-based PSCs is also reviewed as are several scalable process-related preparatory techniques. Finally, we explore the limits of SnO₂ as an ETL and make recommendations for further research.