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 Cr3+-doped Mg3Ga2GeO8 NIR phosphors. Here, we present an approach involving cation engineering, which entails the codoping of Al3+ and Sc3+ ions to substitute Ga3+ sites, coupled with flux-assisted synthesis approaches. The as-prepared Mg3Al0.05Sc0.3Ga1.65GeO8: 0.06Cr3+ 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.