The hydrothermally synthesis of K3AIF6:Cr3+ NIR phosphor and its performance optimization based on phase control

Phosphor-convert (pc) near-infrared (NIR) LED is the next-generation smart MR light sources. Thus, MR phosphors are quickly developed. The K3Al1-xF6:xCr(3+) (KAF:Cr3+) NIR phosphor shows broadband emission from 650 to 900 nm under 430 nm and can be used to fabricate MR LEDs. In this work, KAF:Cr3+ phosphors were prepared by a hydrothermal method for the first time. Morphologies and MR properties are tuned by controlling the hydrothermal processes. Different from the cubic KAF:Cr3+ synthesized by a coprecipitation method, KAF:Cr3+ synthesized by the hydrothermal method shows the tetragonal phase. The optimized KAF:3%Cr3+ shows an internal quantum efficiency of about 31.4%. A NIR pc-LED device was fabricated by integrating the KAF:3%Cr3+ phosphor with a blue LED chip (similar to 450 nm). The output power of NIR light is about 5.5 mW driven at 150 mA.