Ultra-broadband NIR-emitting Cr3+-activated calcium-ferrite type phosphor for dual night vision and information security.

Near-infrared (NIR) light sources are essential for a wide range of applications, thereby stimulating extensive interest in the development of broadband phosphors with effective NIR coverage. Here, we report a novel Cr3+-activated calcium-ferrite type NaScSnO4 phosphor. Benefiting from the intrinsically weak crystal field around Cr3+ and the structural disorder associated with the random distribution of Sc and Sn, the material exhibits an ultrabroad emission band spanning 700-1200 nm and centered at around 900 nm, with a full width at half maximum of 214 nm. Thermal stability studies indicate that the integrated emission decreases with temperature, reaching about 58.6% at 410 K compared with 300 K. Moreover, the broad visible light absorption of the phosphor enables effective excitation by a 465 nm chip, allowing the fabrication of a phosphor converted near-infrared light emitting diode whose applicability in night vision imaging and encryption was further demonstrated. Taken together, our investigation identifies NaScSnO4:Cr3+ as one of the potential broadband NIR phosphors for optoelectronic applications.