Engineering Tunable Dual‐Dependent Emission in Co‐Doped Cs₇Cd₃Br₁₃ Perovskites

ABSTRACT Cd‐based Cs₇Cd₃Br₁₃ perovskites, featuring both tetrahedral and octahedral polyhedral structures, have garnered significant acclaim for their efficient luminescent performance achieved through multi‐exciton state regulation by doping. However, it remains controversial whether the doping sites are in the octahedra or tetrahedra of Cs₇Cd₃Br₁₃. To address this, we introduced Pb²⁺ and Sb³⁺ ions and, supported by experimental and theoretical evidence, demonstrated that these ions preferentially occupy the octahedra. Among them, Pb²⁺ ions single doping achieves a near‐unity photoluminescence quantum yield of 93.7%, which results in excellent X‐ray scintillation performance, high light yield of 41,772 photon MeV⁻¹, and a low detection limit of 29.78 nGy_air s^–1. Moreover, this incorporation of Pb²⁺ and Sb³⁺ enabled an exciton state regulation strategy, resulting in standard white light emission with CIE chromaticity coordinates of (0.33, 0.33). Additionally, a multifaceted optical anticounterfeiting and information encryption scheme was designed based on the differences in optical properties caused by the different sensitivities of [PbBr₆]⁴⁻ octahedron and [SbBr₆]³⁻ octahedron to temperature and excitation wavelengths. These diverse photoluminescence characteristics provide new insights and practical demonstrations for advanced X‐ray imaging, lighting, optical encryption, and anticounterfeiting technologies.