Spectral Regulation and Efficiency Optimization in Cr3+‐Doped Gadolinium Aluminum Gallium Garnet Near‐Infrared Ceramic Phosphors via Crystal‐Field Engineering

The near‐infrared (NIR) phosphor‐converted light‐emitting diode (pc‐LED) is a new NIR light source with both compact structure and high efficiency, and its performances is greatly depended on the NIR phosphors. Herein, this work presents a Cr3+‐doped gadolinium aluminum gallium garnet (GAGG:Cr3+) NIR ceramic phosphor with a broadband emission in the range of 650–850 nm, and optical performances that can be regulated via crystal‐field engineering. By optimizing the Al/Ga ratio, an external quantum efficiency as high as 65% is observed. The thermal stability is enhanced with the increase of Al content, which is attributed to the broadening of bandgap and the weakening of electron–phonon coupling effect. The NIR light output powers of the fabricated device based on the GAGG:Cr3+ ceramic are up to 88.9 mW @ 10 mA and 1247.7 mW @ 200 mA, while the electro‐optical conversion efficiencies were 28.5% @ 10 mA and 17.7% @ 200 mA, respectively. In addition, the NIR pc‐LED exhibited a strong penetrability such that the veins in a palm could be clearly identified, allowing for its potential use in biosecurity applications.