Double‐Site Occupation Triggered Broadband and Tunable NIR‐I and NIR‐II Luminescence in AlNbO4:Cr3+ Phosphors

Abstract Near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) are desired for optoelectronic and biomedical applications, while the development of target broadband NIR phosphors still remains a significant challenge. Herein, a kind of Cr3+‐doped AlNbO4 phosphors with a broad NIR emission ranging from 650 to 1400 nm under 450 nm excitation are reported. A giant red‐shift emission peak from 866 to 1020 nm together with broadened full width at half‐maximum of 320 nm is achieved simply by varying the doped Cr3+ concentrations. Structural and spectroscopy analysis demonstrate that a concentration‐dependent site‐occupation of Cr3+ emitters in different Al3+ sites is responsible for the tunable NIR luminescence. The as‐fabricated NIR pc‐LED based on optimized AlNbO4:Cr3+ phosphor exhibits great potential in night‐vision applications. This work provides a novel design principle on the Cr3+‐doped AlNbO4 phosphor with tunable broadband luminescence from NIR‐I to NIR‐II, and these materials can be employed in NIR spectroscopy applications.