Locally Symmetry-Broken 2D Dion–Jacobson Mixed Halide Perovskites for Efficient Photodetectors
Two-dimensional (2D) Dion–Jacobson (DJ) phase perovskites are promising for photodetection but suffer from inefficient charge carrier extraction and significant ion migration. This study introduces Br− doping into the axial halide sites of (DMPD)Pb(I0.96Br0.04)4 (DMPD = 3-(dimethylamino)-1-propylammonium), inducing local structural symmetry breaking. This symmetry breaking leads to energy band splitting, increased activation energy for ion migration, and relaxed microstrain, as confirmed by theoretical and experimental analyses. The modified lattice and electronic band structures synergistically reduce charge carrier recombination, enhance transport and extraction, and suppress ion migration. Consequently, the single-crystal photodetector achieves a detectivity of 7.12 × 10^12 Jones, among the highest for 2D DJ phase perovskite devices. These findings provide a design strategy for efficient 2D perovskites for advanced optoelectronics.