Atomic layer deposition of a SnO₂ electron-transporting layer for planar perovskite solar cells with a power conversion efficiency of 18.3%

High-efficiency planar type perovskite solar cells were fabricated by atomic layer deposition (ALD) of SnO₂ and subsequent annealing at 180 °C. As-dep. SnO₂ layers prepared by post-annealing at 180 and 300 °C, respectively, were used as electron transporting layers (ETLs). ALD-TiO₂ layers were also prepared by post annealing at 400 °C, and the thicknesses of all ETLs were around 12 nm. PL quenching, optical band gap measurement, UPS, and conductive AFM results show that SnO₂ can more appropriately be used as an ETL compared to TiO₂.