Achieving Broadband NIR Emission in Fe³⁺‐Activated ALaBB′O₆ (A = Ba, Sr, Ca; B–B′ = Li–Te, Mg–Sb) Phosphors via Multi‐Site Ionic Co‐Substitutions

Phosphor‐converted near‐infrared (NIR) LEDs are becoming increasingly demanded as miniature, portability, and broad emission spectrum. In this work, a class of Fe³⁺‐activated double perovskite structured is reported ALaBB′O₆ (A = Ba, Sr, Ca; B–B′ = Li–Te, Mg–Sb) phosphors. Through the co‐substitution strategy at the A‐site and B‐B' sites, the emission spectral intensity and position of Fe³⁺ ions can be tuned. Finally, by utilizing Ca²⁺ at the A‐site and Mg–Sb co‐substitution for Li–Te, long‐wave NIR emission centered at 995 nm in CaLaMgSbO₆: 0.6%Fe³⁺ with a full width at half maximum of 147 nm and internal quantum efficiency of 54.05% is achieved. The effects of the double perovskite crystal structure on Fe³⁺ photoluminescence properties are comprehensively analyzed. NIR LEDs are fabricated by encapsulating UV chips with the synthetic CaLaMgSbO₆: 0.6%Fe³⁺ phosphors, and their application value in night vision, nondestructive biological monitoring, and NIR detection is evaluated.