Extending Near-Infrared Emission Beyond 900 nm in Cr³⁺-Activated Niobate Double Perovskites

Near-infrared (NIR) luminescent materials activated by Cr3+ ion attracted significant attention for their tunable broadband emission, making them highly promising for applications in nondestructive testing and biomedicine fields. Nevertheless, the lack of NIR phosphors emitting above 900 nm that can be used in multiple scenarios has hindered their practical application. Inspired by the crystal field engineering, we successfully realized NIR luminescence tunable from 775 to 980 nm in niobate double perovskites A2BNbO6:Cr3+ (A = Ca, Sr, Ba; B = Ga, Sc, In). Specifically, due to unique structural distortion, Ca2.08In0.88Nb1.04O6:Cr3+ (CIN:Cr3+) exhibits a broadband NIR emission centered at 935 nm, characterized by a full width at half-maximum of 226 nm. Ultimately, by applying a layer of a CIN:Cr3+ phosphor onto the surface of a light-emitting diode (LED) chip, a type of LED device was constructed, showcasing its promising use in the realms of biological imaging and health monitoring.