Interface modification via Al2O3 with retarded charge recombinations for mesoscopic perovskite solar cells fabricated with spray deposition process in the air

In common perovskite solar cells utilizing TiO 2 as electron transport layer, undesirable charge recombination at TiO 2 /CH 3 NH 3 PbI 3 interface is one of the crucial issues to the photovoltaic performance of the device. Moreover, exposure of TiO 2 under long-term solar illumination may also cause deep trap states at TiO 2 surface and seriously influence the device stability. Herein, we introduce an insulating ultra-thin Al 2 O 3 interfacial layer between the mesoporous TiO 2 film and perovskite layer. The power conversion efficiency of the solar cells fabricated via spray deposition in the air increased from 9.36% ( V oc  = 0.86 V, J sc  = 17.21 mA cm −2 , FF = 0.63) to 12.79% ( V oc  = 0.93 V, J sc  = 21.56 mA cm −2 , FF = 0.64). The significantly improved photovoltaic performance is mainly attributed to the efficient reduction of charge recombination. Meanwhile, the Al 2 O 3 -modified perovskite solar cells exhibit a strong stability under long-term light exposure compared with the common device without the Al 2 O 3 interfacial layer.