Optimizing Energy Transfer: Suppressing Cs₂ZnCl₄ Self‐Trapped States and Boosting Ce³⁺ Ion Luminescence Efficiency

Incorporating trivalent cerium ions (Ce 3+ ) into colloidal semiconductor nanomaterials, such as zinc sulfide (ZnS) and cesium lead chloride (CsPbCl 3 ), provides a feasible approach for achieving significant Ce 3+ photoluminescence (PL). However, due to inefficient intersystem crossing and intense non‐radiative decay of host phosphors, most Ce 3+ ‐doped luminophores exhibit low luminescence efficiency, with photoluminescence quantum yield (PLQY) typically <50%. Additionally, these doping systems often encounter challenges with spectral impurity due to unwanted fluorescence emanating from the host material. In this study, an optimal cesium zinc chloride (Cs 2 ZnCl 4 ) nanorod (NR) host matrix is meticulously engineered, that significantly enhances the luminescence of Ce 3+ ions, reaching a PLQY near unity. Furthermore, these NRs display an exceptionally pure Ce 3+ emission spectrum, free from any extraneous emission from the matrix itself. The results from transient absorption and emission experiments reveal a ≈100% energy transfer efficiency from Cs 2 ZnCl 4 to Ce 3+ , coupled with a significant reduction in radiative self‐trapped states within the host.