Enhanced electron extraction using SnO2 for high-efficiency planar-structure HC(NH2)2PbI3-based perovskite solar cells

Planar structures for halide perovskite solar cells have recently garnered attention, due to their simple and low-temperature device fabrication processing. Unfortunately, planar structures typically show I-V hysteresis and lower stable device efficiency compared with mesoporous structures, especially for TiO2-based n-i-p devices. SnO2, which has a deeper conduction band and higher electron mobility compared with traditional TiO2, could enhance charge transfer from perovskite to electron transport layers, and reduce charge accumulation at the interface. Here we report low-temperature solution-processed SnO2 nanoparticles as an efficient electron transport layer for perovskite solar cells. Our SnO2-based devices are almost free of hysteresis, which we propose is due to the enhancement of electron extraction. By introducing a PbI2 passivation phase in the perovskite layer, we obtain a 19.9 +/- 0.6% certified efficiency. The devices can be easily processed under low temperature (150 degrees C), offering an efficient method for the large-scale production of perovskite solar cells.