Atomic layer deposition-free tin oxide as an electron transport layer for wide-bandgap perovskite solar cells and Si/perovskite tandem solar cells

The electron transport layer (ETL) is critical to the performance and stability of perovskite solar cells (PSCs). Tin oxide (SnO₂) has emerged as a promising ETL due to its high electron mobility, broad optical transparency, and superior chemical stability. However, conventional atomic layer deposition (ALD) for SnO₂ is costly and slow, limiting scalability. In this work, we develop a cost-effective SnO₂ ETL using spray-coated ground SnO₂ nanoparticles (G-SnO₂) mixed with Cs₂CO₃. Wide-bandgap PSCs with G-SnO₂ and Cs₂CO₃-G-SnO₂ achieve efficiencies of 18.27% and 19.77%, outperforming the reference PSC (17.46%). Si/perovskite tandem solar cells using spray-coated G-SnO₂ reach a PCE of 27.3%. This approach provides a scalable, low-cost alternative to ALD-based SnO₂ ETLs, enabling efficient and stable perovskite and tandem solar cells.