Facilitating Near‐Infrared Persistent Luminescence in Cr3+‐Doped Gadolinium Gallium Garnets

Abstract Near‐infrared persistent luminescence (NIR PersL) materials provide great potential in the fields of night vision, biological imaging, and information encryption. However, among various crystal structures, Cr 3+ ‐doped gallium garnets show inferior PersL property, which turns out to be the bottleneck of their versatile applications. The rational design and facile preparation of high‐performance NIR PersL materials are crucial for the emerging applications. In this work, a series of Gd 3 Mg x Ge x Ga 5‐2x O 12 :Cr 3+ ( x = 0, 0.25, 0.5, 0.75, 1) is investigated by microwave‐assisted solid‐state (MASS) approach. Furthermore, by employing chemical composition co‐substitution, PersL performance is further improved and the optimum working temperature is adjusted to the lower temperature at 10 °C. Trap level distribution of Gd 3 Mg 0.5 Ge 0.5 Ga 4 O 12 :Cr 3+ phosphor is revealed based on the temperature and fading‐time dependent PersL and thermoluminescence property. Further study demonstrates the reduction of the bandgap and the trap distribution forwards at shallow‐lying trap energy levels. The synergistic effect, from both energy‐band manipulation and trap‐level optimization, facilitates NIR PersL in Cr 3+ ‐doped gadolinium gallium garnets. These findings confirm the applicability of MASS‐based bandgap and defect level engineering for improving the PersL properties in non/inferior‐PersL materials. This burgeoning MASS method may facilitate a wide range of PersL materials for various emerging applications.