Designing a Double-Perovskite Ca₂MgTeO₆:Fe³⁺ Near-Infrared Phosphor for Multifunctional Applications

Near-infrared (NIR) phosphors are key components for NIR phosphor-converted light-emitting diodes (pc-LEDs), which serve as compact light sources for a range of smart spectroscopic applications. However, developing an efficient, low-cost, and broadband NIR phosphor with a long-wavelength emission peak beyond 900 nm remains a considerable challenge. Guided by design principles summarized here, we selected the double-perovskite Ca₂MgTeO₆ as a host for Fe³⁺ doping. Systematic analysis of the crystal and electronic structures reveals the crystal's strong potential for generating efficient NIR luminescence. Experimental results confirm that the optimally doped sample exhibits NIR emission centered at 944 nm and achieves a remarkably high photoluminescence quantum yield (PLQY) of 87.8% under 310 nm excitation. Finally, the developed material was successfully applied in nondestructive testing, night vision, and information encryption, realizing multifunctional applications.