Enhancement of Near-Infrared Phosphor Luminescence Properties via Construction of Stable and Compact Energy Transfer Paths

The rapid development of near-infrared (NIR) spectroscopy urgently requires the exploration of NIR-emitting phosphors with excellent luminescence properties. Herein, GaTaO4:Cr3+,Yb3+ NIR phosphor with excellent luminescence properties is reported, which exhibits ultra-broadband NIR emission with a full width at half maximum of 300 nm, good thermal stability of 90%@423 K, and most remarkably, high internal quantum efficiency of 95.5% and external quantum efficiency of 44.79%. Such outstanding luminescence properties mainly give the credit to the unique sandwiched structure of GaTaO4:Cr3+,Yb3+, in which layers of Yb3+ ions (activator) are sandwiched between layers of Cr3+ ions (sensitizer), and hence many stable and compact Cr-Yb pairs are formed, so that the energy can be rapidly transferred from Cr3+ to Yb3+, effectively activating the characteristic f-f transition of Yb3+ that is very stable and almost independent of the temperature, and at the same time, the non-radiative transition of Cr3+ ions can be suppressed to a certain degree. The NIR phosphor-converted light-emitting diodes (pc-LEDs) are fabricated by combining GaTaO4:Cr3+,Yb3+ with blue LED chips, and the application potential is fully demonstrated by non-destructive food detection, night vision, and vein display. The results provide novel prospects for the design of NIR-emitting materials with desirable luminescent properties.