TiO₂/SnO₂ Bilayer Electron Transport Layer for High Efficiency Perovskite Solar Cells

The electron transport layer (ETL) has been extensively investigated as one of the important components to construct high-performance perovskite solar cells (PSCs). Among them, inorganic semiconducting metal oxides such as titanium dioxide (TiO₂), and tin oxide (SnO₂) present great advantages in both fabrication and efficiency. However, the surface defects and uniformity are still concerns for high performance devices. Here, we demonstrated a bilayer ETL architecture PSC in which the ETL is composed of a chemical-bath-deposition-based TiO₂ thin layer and a spin-coating-based SnO₂ thin layer. Such a bilayer-structure ETL can not only produce a larger grain size of PSCs, but also provide a higher current density and a reduced hysteresis. Compared to the mono-ETL PCSs with a low efficiency of 16.16%, the bilayer ETL device features a higher efficiency of 17.64%, accomplished with an open-circuit voltage of 1.041 V, short-circuit current density of 22.58 mA/cm², and a filling factor of 75.0%, respectively. These results highlight the unique potential of TiO₂/SnO₂ combined bilayer ETL architecture, paving a new way to fabricate high-performance and low-hysteresis PSCs.