Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs), a widely used NIR light source, are typically prepared by sealing the NIR phosphor powder and an LED chip with epoxy resin. One issue that NIR pc-LEDs frequently encounter is the aging and deterioration of epoxy resin over time, which leads to self-absorption and a sharp decline in emission efficiency. Here, we report the synthesis of a chemically stable NIR luminescent material composed of Cr3+-doped Ba2NaNb5O15 nanocrystals measuring 10–15 nm, with Cr3+ ions located in the octahedral centers of the nanocrystals. Under 460 nm light excitation, the transparent glass-ceramic exhibited a broadband NIR emission in the range of 600–1400 nm, which originated from the electronic transition of Cr3+ from the excited state of 4T2 to the ground state of 4A2. The emission peak was located at ∼810 nm, the FWHM was ∼230 nm, and the internal quantum efficiency reached ∼0.81%. We constructed a stable NIR pc-LED device using optimized transparent NIR-emitting glass-ceramics and a commercially available blue LED chip, demonstrating its promising application in night-vision lighting. Our study provides a basis for the preparation of transparent glass-ceramic-based NIR pc-LED devices as an improved alternative for solid-state illumination.
Near-infrared (NIR) spectroscopy has the advantages of instant responsiveness, non-destructiveness and high signal-to-noise ratio, and has broad application prospects in night vision security monitoring, indoor agriculture, biomedical imaging and photodynamic therapy, etc. NIR phosphor-converted light-emitting diodes (NIR pc-LEDs) as a NIR light source, have the advantages of compact size, broadband emission, high efficiency, readily available LED chips as excitation light sources, tunable emission spectrum, and excellent prospects for industrial manufacture. However, the service life of traditional organic packaging materials is greatly reduced over time due to heat accumulation and accelerated aging, especially when operated under high-power irradiation. To overcome this drawback, we successfully prepared Ba 2 NaNb 5 O 15 :Cr 3+ ,Yb 3+ nanocrystals embedded in stable and transparent glass-ceramics by a two-stage process that involves an melt-quenching followed by a re-crystallization heat-treatment. Under 460 nm excitation, the glass-ceramics exhibited a 700–1200 nm broadband NIR emission that originated from the Cr 3+ -activating centers and a sharp line emission near ∼980 nm that originated from the Yb 3+ -activating centers, with a PLQY was ∼43.7 %. A NIR pc-LED light source device with a direct contact structure between transparent glass-ceramic and a blue chip was prepared, and the application potential of the NIR light source in night-vision imaging was verified.
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