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

ABSTRACT 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 CsPbBr ₃ 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.