Atomic‐Scale Insights Into Antisite‐Defect‐Induced Metallicity in Halide Perovskites

Defects are ubiquitous in halide perovskites and play a critical role in determining their structural stability and optoelectronic performance. Achieving atomic-scale identification and understanding of these defects in perovskite is essential for the rational design of high-performance optoelectronic devices. Using an aberration-corrected scanning transmission electron microscope, we directly visualize the atomic structure of the Pb_Cs antisite defect in CsPbBr₃ perovskite. The Pb_Cs antisite was found to shorten the Pb─Pb bond length by approximately 20 pm, inducing a local polarization phenomenon and ∼3% compressive strain around the defect. Based on the identified atomic-scale configuration, first-principles calculations revealed that the Pb_Cs antisite induces a semiconductor-to-metal transition, driven by additional electron donation from the substituted Pb atoms that shift the Fermi level into the conduction band. These findings establish a fundamental understanding among atomic-scale structure, polarization, and electronic structure modulation in antisite defects, providing valuable insights for defect engineering strategies toward stable and efficient perovskite optoelectronic devices.