Long-Wavelength Near-Infrared MgIn₂O₄:Ni²⁺ Phosphor with 47.93% IQE and 34.66% EQE for Night Vision Lighting, Nonvisual Detection, and Biological Imaging

Presently, there are very limited options for a broad-band long-wavelength near-infrared phosphor-converted light-emitting diode (LWNIR pc-LED) with wavelengths above ∼1500 nm, and most LWNIR phosphors have a low luminescence quantum efficiency. Here, Ni2+-doped MgIn2O4 antispinel phosphors were prepared by a high-temperature solid-state reaction method. Under 365 nm excitation, they exhibited broad-band LWNIR emission in the range of 1200–2100 nm, with an emission peak of ∼1490 nm and a full width at half-maximum of ∼313 nm, indicating a weak crystal field environment with high electron polarization around the center of the [MgO6] octahedron. The IQE and EQE of MgIn2O4:Ni2+ phosphors were ∼47.93% and ∼34.66%, respectively. The optimized phosphor was encapsulated with an LED chip to obtain a LWNIR pc-LED device for night vision lighting, nonvisual detection, and biological imaging. Our results confirmed that LWNIR lighting based imaging technology showed clear safety advantages over traditional high-energy ray imaging.