Multi‐site regulation of Gd garnet for lattice stabilization and efficient/thermally stable broadband Cr ³⁺ luminescence

Abstract The growing demand for near‐infrared phosphor‐converted light‐emitting diodes (NIR pc‐LEDs) has posed significant challenges to the development of NIR‐emitting phosphors with high quantum efficiency and thermal stability. A series of (Gd 3‐ x Ca x )(Hf x Sc y Al 3 Cr 0.05 )O 12 ( x + y = 1.95, x = 0.45–1.95, y = 0.0–1.5) garnet phosphors, designed by modifying both the Gd and Al sites of Gd 3 Al 5 O 12 , were fabricated by solid‐state reaction and investigated for their structure and NIR luminescence. Ca 2+ and Hf 4+ /Sc 3+ /Cr 3+ would replace the Gd 3+ in [GdO 8 ] dodecahedron and the Al in [AlO 6 ] octahedron, respectively. The phosphors are effectively excitable by 452 nm blue light to emit NIR light, and a higher Ca 2+ /Hf 4+ content ( x value) would red‐shift (from ∼732 to 750 nm) and broaden (full width at half maximum from ∼82.7 to 87.6 nm) the emission through weakening the crystal field of Cr 3+ . The x = 0.95 optimal phosphor was determined to have external/internal quantum efficiencies (%) of 26.5/54.9 and a thermal stability of 81.6%@423 K. The NIR pc‐LED device based on the x = 0.95 phosphor achieved an output power of 34.71 mW and a photoelectric conversion efficiency of 12.01% at a driving current of 100 mA and showed the potential for non‐destructive testing, night vision, and medical imaging.