Efficient broadband near-infrared luminescence of Cr3+ doped fluoride K2NaInF6 and its NIR-LED application toward veins imaging

High performance broadband Near-infrared (NIR) phosphors with high efficiency and excellent thermal stability are highly demanded for constructing the next generation of NIR radiation sources. Herein, a broadband NIR emitting fluoride phosphor K2NaInF6:Cr3+ peaking at 774 nm with a Full width at half maximum (FWHM) of 116 nm (1906 cm−1) was demonstrated. A high Internal quantum efficiency (IQE) value of 70.2% can be obtained in the as-synthesized K2NaInF6:Cr3+ phosphor. Additionally, benefiting from the relatively weak electron phonon coupling effect, the phosphor also exhibits excellent anti-thermal quenching behavior with the emission intensity at 150 °C retaining 78.3% of that at room temperature. A high power NIR pc-LED with NIR radiant flux of 492.85 [email protected] mA is obtained by combing the as-synthesized K2NaInF6:Cr3+ phosphor and a blue LED chip. Utilizing this high power NIR pc-LED as NIR radiation source, high-resolution human hand veins imaging is realized with the assistance of a NIR camera, which indicates that K2NaInF6:Cr3+ phosphor has high potential in biological applications.