Long persistent self-activated luminescence enhanced by Cd2+ in CaGa4O7 for optical information storage

Comparing long persistent luminescence (LPL) materials, typically doped or optimized with lanthanide or transition metal ions, the optimization of the intrinsic LPL performance in dopant-free, self-activated luminescent materials remains largely underexplored. In this study, we report a surprising enhancement of LPL in a self-activated material, CaGa₄O₇, through the introduction of Cd²⁺ ions—an element not traditionally associated with luminescence centers. This modification extended the afterglow duration from just 6 min to almost 2 h, a substantial improvement that has not been previously observed. Through thermoluminescence analysis and first-principles calculations, we elucidate that this enhancement arises from the formation of oxygen vacancies (V_O), which are promoted by the incorporation of Cd²⁺. In addition, this material can store and read information with the aid of temperature, demonstrating its potential applications in information storage and anti-counterfeiting areas. Our findings offer a promising strategy for further engineering the intrinsic LPL properties of self-activated materials, paving the way for their functional applications in the future.