Building (001) oriented FAPbI3 films for high-performing perovskite solar cells

The solution processed FAPbI₃ perovskite usually suffers from chaotic orientations. Herein, a template structure of oriented 2D perovskite is used to obtain a high-quality FAPbI₃ film with (001) preferred orientation by cation exchange. The highly oriented BA₂PbI₄ serves as a growth template and promotes the (001) orientation of the 3D perovskite. The dominantly (001) orientated FAPbI₃ perovskite exhibits uniform surface morphology and suppressed film defects.