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 TiO2 as electron transport layer, undesirable charge recombination at TiO2/CH3NH3PbI3 interface is one of the crucial issues to the photovoltaic performance of the device. Moreover, exposure of TiO2 under long-term solar illumination may also cause deep trap states at TiO2 surface and seriously influence the device stability. Herein, we introduce an insulating ultra-thin Al2O3 interfacial layer between the mesoporous TiO2 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 Al2O3-modified perovskite solar cells exhibit a strong stability under long-term light exposure compared with the common device without the Al2O3 interfacial layer