Revealing the Mechanism of Pressure‐Induced Emission in Layered Silver‐Bismuth Double Perovskites

Abstract Pressure‐induced emission (PIE) associated with self‐trapping excitons (STEs) in low‐dimensional halide perovskites has attracted great attention for better materials‐by‐design. Here, using 2D layered double perovskite (C 6 H 5 CH 2 CH 2 NH 3 + ) 4 AgBiBr 8 as a model system, we advance a fundamental physicochemical mechanism of the PIE from the perspective of carrier dynamics and excited‐state behaviors of local lattice distortion. We observed a pressure‐driven STE transformation from dark to bright states, corresponding a strong broadband Stokes‐shifted emission. Further theoretical analysis demonstrated that the suppressed lattice distortion and enhanced electronic dimensionality in the excited‐state play an important role in the formation of stabilized bright STEs, which could manipulate the self‐trapping energy and lattice deformation energy to form an energy barrier between the potential energy curves of ground‐ and excited‐state, and enhance the electron‐hole orbital overlap, respectively.