Isovalent B-Site Cation Engineering Enables Multimode Optical Storage in Metal Halide Perovskite

Systematic strategies for modulating trap distributions through B-site cation engineering in metal halide phosphors remain elusive. Here, we employ density functional theory to guide the isovalent substitution of Cd 2+ with Zn 2+ in Cs 3 Cd 2 Cl 7 :Sb 3+ afterglow phosphors. By leveraging the electronegativity difference and ionic radius mismatch between Zn 2+ and Cd 2+ , we perturb the local bonding environment while preserving the [SbCl 6 ] 3– emission framework. Zn 2+ incorporation modifies the local structural and electronic environments, while thermoluminescence spectroscopy reveals a broadened trap distribution. The optimized composition, Cs 3 Cd 1.95 Zn 0.05 Cl 7 :0.04Sb 3+ , exhibits prolonged afterglow exceeding 180 s-substantially longer than that of the undoped counterpart, while maintaining green self-trapped exciton (STE) emission centered at 518 nm. These engineered defects enable multimode optical readout via thermal stimulation, 980 nm photostimulation, and X-ray excitation. This work establishes a clear correlation between B-site cation identity and defect energetics, providing actionable design principles for next-generation optical storage materials.