Tunable NIR Emission of Cr³⁺-Activated Double-Perovskite Tantalates and Improvement of Luminescence Properties via Codoping Yb³⁺

Broadband near-infrared (NIR) luminescent materials exhibit great potential in many fields including nondestructive examination, biological imaging, and night vision. Herein, the tunable NIR emission can be realized based on Sr₂MTaO₆:Cr³⁺ (M = Ga, Sc, In) tantalate phosphors with a double-perovskite structure, with the emission peak varying from 782 to 880 nm via cation modulation. Specifically, after being stimulated by a 460 nm blue light, the Sr₂GaTaO₆/Cr³⁺ phosphor demonstrates a broadband NIR emission with the full width at half-maximum (fwhm) over 180 nm, originating from two octahedral sites of Ga³⁺ and Ta⁵⁺ in Sr₂GaTaO₆ that can be occupied by Cr³⁺ ions. By using the Yb³⁺ codoping strategy, the efficient energy transfer process (Cr³⁺ → Yb³⁺) enables remarkable expansion of the fwhm to 304 nm and significant improvement in thermal stability due to the suppressive thermal quenching behavior of Cr³⁺ ions. Ultimately, by mixing the Sr₂GaTaO₆/Cr³⁺, Yb³⁺ phosphor with an epoxy adhesive and coating on a 460 nm blue LED chip, an NIR pc-LED device was successfully fabricated, and its prospective usage in nondestructive testing and night vision fields was evaluated. This work contributes to the exploration of blue light effectively stimulating broad-band NIR-emitting phosphors.