Structural Distortions and Ionic Diffusion Mechanisms in the Quasi-1D Copper Halide Perovskite CsCu₂I₃

Copper-based all-inorganic halide perovskites have garnered increasing attention due to their distinctive quasi-one-dimensional crystal structures and promising optoelectronic and ionic transport properties. Among them, CsCu₂I₃ stands out as a widely studied model system, exhibiting efficient Cu⁺ ion diffusion with low activation energy, along with strong photoluminescence and broadband emission. In this study, we employed high-resolution synchrotron X-ray diffraction to elucidate the crystal structure of CsCu₂I₃ and uncovered subtle local distortions, indicating a deviation from the previously accepted structural model. By integrating temperature-dependent synchrotron measurements with advanced structural analysis, we probed the Cu⁺ ion transport mechanism and quantified the corresponding activation energy. Our findings reveal a strong coupling between local structural distortions and ionic mobility, offering critical insights for the rational design and optimization of copper-based halide perovskites in optoelectronic and energy-related applications.