Locally Symmetry-Broken 2D Dion–Jacobson Mixed Halide Perovskites for Efficient Photodetectors

• • Achieved detectivity of 7.12 × 10^12 Jones in 2D DJ perovskite photodetectors, ranking among the highest reported, enabling ultrasensitive light detection for imaging and sensing applications. • • Br− doping at axial halide sites increases activation energy for ion migration, suppressing dark current and improving operational stability, critical for long-term device reliability. • • Local symmetry breaking induces energy band splitting and relaxes microstrain, reducing charge carrier recombination and enhancing transport, leading to improved photoresponse. • • The single-crystal device demonstrates a detectivity of 7.16 × 10^12 Jones, validating the effectiveness of the symmetry-breaking strategy for high-performance optoelectronics.