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

Abstract

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.