Atomic Real-Space Imaging of the Phase Distribution in Halide Perovskites.

Crystalline materials are not perfectly ordered periodic structures but present obvious disordered characteristics, which determine their intrinsic properties. Halide perovskites typically consist of ordered and disordered phases due to continuous octahedral rotations among the α, β, and γ phases. However, unraveling the spatial phase distribution requires a real-space imaging method with sufficient resolution. Here, we apply low-dose electron microscopy to study the rotation angle phase distribution in perovskites and reveal the factors affecting the phase structure and spatial distribution. Phase structures can be quantified by measuring the rotational angles of octahedra atomically. Then, we investigate how crystal size, temperature, surface, and interface structures affect the spatial phase distribution. These results provide local structural information about the phase distribution in halide perovskites for further applications and provide crucial insights into the ordered and disordered nature of crystalline materials in real space.