The hydrothermally synthesis of K ₃ AlF ₆ :Cr ³⁺ NIR phosphor and its performance optimization based on phase control

Abstract

Abstract Phosphor‐convert (pc) near‐infrared (NIR) LED is the next‐generation smart NIR light sources. Thus, NIR phosphors are quickly developed. The K 3 Al 1−x F 6 :xCr 3+ (KAF:Cr 3+ ) NIR phosphor shows broadband emission from 650 to 900 nm under 430 nm and can be used to fabricate NIR LEDs. In this work, KAF:Cr 3+ phosphors were prepared by a hydrothermal method for the first time. Morphologies and NIR properties are tuned by controlling the hydrothermal processes. Different from the cubic KAF:Cr 3+ synthesized by a coprecipitation method, KAF:Cr 3+ synthesized by the hydrothermal method shows the tetragonal phase. The optimized KAF:3%Cr 3+ shows an internal quantum efficiency of about 31.4%. A NIR pc‐LED device was fabricated by integrating the KAF:3%Cr 3+ phosphor with a blue LED chip (~450 nm). The output power of NIR light is about 5.5 mW driven at 150 mA.