(111) Facet-engineered SnO2 as an electron transport layer for efficient and stable triple-cation perovskite solar cells†

In this study, we report (111) facet-engineered cubic phase tin(IV) oxide (C–SnO₂) as a novel electron transport layer (ETL) for triple-cation mixed-halide Cs_0.05(FA_0.83MA_0.17)_0.95Pb(I_0.83Br_0.17)₃ perovskite solar cells (PSCs). The C–SnO₂ layer was prepared via a normal sol–gel process followed by the spin-coating technique. The (111) facet C–SnO₂ layer provides a larger surface contact area with an adjacent perovskite layer, enhancing charge transfer dynamics at the interface. In addition, the well-matched overlapping band structures improve the charge extraction efficiency between the two layers. Using (111) facet C–SnO₂ as an ETL, we obtain PSCs with a higher power conversion efficiency of 20.34% (0.09 cm²) than those employing a tetragonal phase SnO₂ ETL. The PSCs with the C–SnO₂ ETL retain over 81% of their initial efficiency after 480 h. This work concludes with a brief discussion on recombination and charge transport mechanisms, providing ways to optimize the C–SnO₂ ETL to improve the PSCs' performance and stability.