Carrier Separation Enhanced by High Angle Twist Grain Boundaries in Cesium Lead Bromide Perovskites.

Abstract

Grain boundaries (GBs) have a profound impact on mechanical, chemical, and physical properties of polycrystalline materials. Comprehension of atomic and electronic structures of different GBs in materials can help to understand their impact on materials' properties. Here, with aberration-corrected scanning transmission electron microscopy (STEM), the atomic structure of a 90° twist GB s in CsPbBr3 is determined, and its impact on electron-hole pair separation is predicted. The 90° twist GB has a coherent interface and the same chemical composition as the bulk except for the lattice twist. Density functional theory (DFT) calculation results indicate that the twist GB has an electronic structure similar to that of the bulk CsPbBr3. An electronic potential at the GBs enhances the separation of photogenerated carriers and promotes the motion of electrons across the GBs. These results extend the understanding of atomic and electronic structure of GBs in halide perovskites and propose a potential strategy to eliminate the influence of GBs by GB engineering.