Defect engineering modulates efficiently near-infrared emission from Nd3+/Ce3+ -doped LiYF4 single crystals

Rare-earth (Ln(3+))-doped luminescent crystals show great promise emitting in the second near-infrared (NIR-II) bio-window, but their applications are currently limited by the low absorption efficiency of Ln(3+) due to the parity-forbidden 4f -> 4f electron leaps. Here, we develop a synthetic scheme for novel NIR-II luminescent materials based on Ce3+/Nd3+ co-doped LiYF4 crystals, which can be efficiently excited by a low-cost blue light-emitting diode chip. Strong NIR-II luminescence at 1047 nm of Nd3+ ion was achieved under excitation at 465 nm with help of the sensitization of Ce3+. Defect engineering was designed to further enhance the NIR luminescence intensity and thermal stability by introducing inactive Na+, Mg2+, Lu3+, Gd3+ ions. Especially, Gd3+ ion doping increased the NIR luminescence intensity at 1047 nm by a factor of 2, and the thermal activation energy was increased from 0.232 eV to 0.294 eV. The prepared Nd3+/Ce3+/Gd3+ doped NIR crystals were integrated with a commercial blue LED (@465 nm) to fabricate NIR single crystal LEDs, the LEDs showcased their potential in applications such as efficient NIR night vision surveillance and non-invasive vascular imaging.