Low temperature solution-derived TiO2-SnO2 bilayered electron transport layer for high performance perovskite solar cells

Abstract Planar lead halide perovskite solar cells have shown a promising application in the field of printable solar cells. However, high-performance planar perovskite solar cells typically need a high-temperature process to achieve crystallized titanium oxide films as the electron transport layers, which hinders their application in flexible plastic substrates. Here, we demonstrate a bilayered TiO 2 -SnO 2 film as an excellent substitute for electron transport layer using a low temperature liquid phase method. The bilayered TiO 2 -SnO 2 film exhibits efficient electron extraction and hole blocking ability even at a low processing temperature of 150 °C. The as-obtained solar cells exhibit a champion power conversion efficiency of 18.85% (V oc  = 1.100 V, J sc  = 22.52 mA cm −2 and FF = 0.761) under one sun illumination, which is much higher than the devices based on individual SnO 2 or TiO 2 electron transport layers. The higher electron extraction driving force at the SnO 2 /perovskite interface and the stronger hole blocking ability due to the defect-free physical contact at the TiO 2 /FTO interface are suggested to be the main reasons for the improved device performance.