Cationic Engineering-Driven Al 3+ /Sc 3+ Codoping Achieves 60.9% EQE in Cr 3+ -Activated Mg 3 Ga 2 GeO 8 Near-Infrared Phosphors

Near-infrared (NIR) phosphors are crucially important components of phosphor-converted light-emitting diodes (pc-LEDs). However, their widespread application is hindered by their inherently low external quantum efficiency (EQE). To overcome this limitation, we developed Cr 3+ -doped Mg 3 Ga 2 GeO 8 NIR phosphors. Here, we present an approach involving cation engineering, which entails the codoping of Al 3+ and Sc 3+ ions to substitute Ga 3+ sites, coupled with flux-assisted synthesis approaches. The as-prepared Mg 3 Al 0.05 Sc 0.3 Ga 1.65 GeO 8: 0.06Cr 3+ phosphor demonstrates a broad NIR emission spectrum ranging from 630 to 1200 nm, with a full width at half-maximum (fwhm) of 188 nm upon excitation at 410 nm. The optimized sample achieves an internal quantum efficiency (IQE) of 96.6%, and the EQE reaches a breakthrough value of 60.9%, along with high thermal stability (86.5% @373 K). Furthermore, pc-LED device packaged with this phosphor are promising for applications in venous imaging, anticounterfeiting, and information encryption. These findings offer valuable insights into the design of high-efficiency NIR phosphors.