Highly efficient and stable Cr3+-activated oxyfluoride near-infrared emitting phosphor for night vision and plant growth

Near-infrared (NIR) light sources have many potential applications in biological, night vision, food safety, and plant growth. In this study, we report a highly efficient and thermally stable NIR phosphor LiAl4(1-x)O6F:xCr3+ (in brief LAOF:Cr3+). Under 565 nm excitation, the optimal LAOF:1.1%Cr3+ phosphor shows two sharp line spectra (named Cr1) centered at 703 nm and 713 nm, and a broadband emission (named Cr2) centered at 770 nm, which is ascribed to the [AlO6] and [Al(O, F)6] octahedra in the LAOF structure. Its unique narrowband and broadband emission correspond well with the absorption band of far-red phytochrome pigments (PFR), suggesting the potential application in plant growth. The FWHM extends from 25 to 53 nm as rising the Cr3+ ions concentration, and the Cr2 emission becomes more and more conspicuous. The LAOF:1.1%Cr3+ phosphor exhibits a high internal quantum efficiency (IQE) and external quantum efficiency (EQE) of ∼83.0% and 36.4%, respectively. Moreover, the LAOF:1.1%Cr3+ phosphor has good thermal stability (84.3%@373 K). NIR pc-LED device manufactured with a 450 nm blue LED chip and LAOF:1.1%Cr3+ phosphor exhibits good NIR output power (31.07 mW@100 mA) and photoelectric efficiency (13.3%@10 mA). The findings suggest the LAOF:Cr3+ phosphor holds potential in NIR pc-LED applications.