Enlarging grain sizes for efficient perovskite solar cells by methylamine chloride assisted recrystallization

The quality of MAPbI3 film prepared by solvent engineering process highly depends on environment and antisolvent control. Here, we provided a simple methylamine chloride (MACl) solution treatment using a two-step process to enlarge the perovskite crystal grain sizes to more than 1 μm. Other than treatment on the film surface, the MACl solution diffuses into the MAPbI3 films to assist the recrystallization of small crystal at the bottom of perovskite film. The imitative contact between perovskite and substrate is formed. Meanwhile, the enlargement of grain size and ten times enhancement of crystalline reduce trap-assisted recombination of perovskite films. Thus, the significant improvement of cell efficiency of 20.89% as well as device stability is obtained with the MACl treatment.