Building New Structural Distortion Descriptors through Pressure Engineering toward Enhanced Violet Emission in 2D Hybrid Perovskite

Abstract Building an explicit structure‐property relationship for two‐dimensional (2D) hybrid perovskites is critical to guide the synthesis of highly luminescent materials. However, traditional studies are limited to the deviation of individual intra‐octahedron, which fails to well reflect collective lattice distortion. Here, a set of new structural distortion descriptors associated with inter‐octahedra is introduced for 2D perovskite (C₇H₁₀N)₂PbBr_4, that is,(PMA)₂PbBr₄ through pressure engineering. An experimental conclusion is reached that adjacent Pb displacement, as the inter‐octahedron distortion, is an effective parameter in determining the structural distortion and emission behavior of (PMA)₂PbBr₄ under high pressure. Under high pressure, 2D perovskite (PMA)₂PbBr₄ exhibits two emission behaviors, free excitons (FEs) emission and self‐trapped excitons (STEs) emission. Different types of four‐Pb‐shaped quadrilateral correspond to different emissions: square‐type (only FEs emission), parallelogram‐type (coexistence of FEs emission and STEs emission), kite‐type (only STEs emission). Moreover, an enhanced violet emission at ≈431 nm is achieved under a mild pressure of 1.0 GPa, which is a crucial light source of medical sterilization. The underlying structure‐property relationship is clarified fundamentally deepens the photophysical mechanism of (PMA)₂PbBr₄, thus facilitating the design of high‐efficiency perovskite luminophores.