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.