Identifying Near-Infrared Persistent Luminescence in Cr3+-Doped Magnesium Gallogermanates Featuring Afterglow Emission at Extremely Low Temperature

Room-temperature persistent phosphors emitting in a wide spectral range are extensively explored owing to their commercial interest in applications such as night-vision signs and medical imaging. However, phosphors featuring long-lasting near-infrared emission at extremely low temperature are barely reported so far. Herein, a design of trivalent chromium-activated magnesium gallogermanates (Mg1+xGa2-2xGexO4:Cr3+) is demonstrated that exhibit strong near-infrared afterglow emission at low temperature, e.g., -80 degrees C. Notably, this new persistent phosphor can be efficiently activated even at these low temperatures. A combination of experimental characterizations together with simulations has identified its novel low-temperature persistent luminescence and good capacity of stabilizing a large number of very shallow traps. The finding of this low-temperature near-infrared afterglow property opens up a new frontier for exploring persistent phosphors and provides an opportunity for novel applications at extreme conditions, such as cryopreservation of biological samples.