Ordered Stacking of (001) Facet‐Oriented 3D Perovskite Crystals with an Ultralow Misorientation

Abstract Although the preferred growth of crystallographic facets in polycrystalline perovskite films has been realized, achieving ordered stacking of oriented facets remains challenging. Highly ordered stacking of (001) facet‐oriented perovskite crystals are reported, actualized by depositing a continuous 2D perovskite layer on the surface of the PbI 2 film to induce oriented growth of 3D perovskites based on the two‐step method. The continuous 2D perovskite layer showing oriented (00k) facets and ordered stacks presents matched lattices with 3D perovskites, leading to the preferential growth of (001) facets across the entire 3D perovskite film with the same stacking pattern as the 2D perovskite layer. The resultant perovskite film exhibits an unprecedentedly low misorientation of 3° as evidenced by azimuth curves obtained from the grazing‐incidence wide‐angle X‐ray scattering measurement, representing the highest stacking orientation so far. The improved spatial homogeneity of crystallographic structures endows perovskite films with reduced trap states and increased charge transports, leading to a solar‐cell efficiency of 25.81% (23.09% for 1 cm 2 devices) with excellent stability under illumination and damp heat tests. This work offers an effective strategy to achieve highly ordered crystal stacks in perovskite films, which is significant for further improving performances of various perovskite‐based optoelectronic devices.