Manipulating Spectral Location in a Cr 3+ ‐Activated Broadband Garnet Phosphor Toward Highly Efficient NIR Pc‐LEDs

ABSTRACT Near‐infrared phosphor‐converted light‐emitting diodes (NIR pc‐LEDs) are highly attractive due to compact, low‐cost, and portable characteristics. Despite the discovery of several efficient and thermostable NIR garnet phosphors, the output power and photoelectric conversion efficiency of the fabricated NIR pc‐LEDs remain severely limited, hindering their practical deployment. Herein, we address this challenge by a single‐site substitution design of Ge 4+ for Si 4+ in a garnet host Y 2 MgAl 4 SiO 12 (YMASi). The newly developed Y 2 MgAl 4 GeO 12 (YMAGe):Cr 3+ phosphor demonstrates a substantially red‐shifted broadband NIR emission (90 nm shift, peaking at 809 nm) with an ultra‐broad full‐width at half maximum (FWHM) of 152 nm, along with good thermal stability (82%@423 K). Remarkably, this substitution simultaneously enhances the internal and external quantum efficiencies by factors of 1.8 and 2.1, respectively. Combining atomic‐resolution imaging with spectroscopic analysis, we unravel the origin of the spectral redshift and the underlying mechanism for the luminescent enhancement. Benefiting from these outstanding properties, driven by 100 mA, a prototype NIR light source fabricated with YMAGe:Cr 3+ achieves a high output power of 51.6 mW and photoelectric conversion efficiency of 22.7%, thereby demonstrating strong potential for multifunctional applications including night vision, biological imaging, non‐destructive testing, and plant growth lighting.