Jianbang Zhou,Pengyun Chen,Junhao Li,Mingming Yang,Wei Jiang,Qiuhong Zhang,Haiyong Ni,Jiansheng Huo
Cr3+-Activated broadband near-infrared (NIR) luminescence materials are attracting much attention as next-generation smart NIR light sources that are widely used in night vision, bioimaging, medical treatment, and many other fields. Herein, a series of Na3GaxAl1−xF6:Cr3+ NIR phosphors with broadband emission and tunable luminescence properties were designed and prepared. The luminescence intensity, peak position and full width at half maximum (FWHM) of the materials can be controlled by adjusting the crystal field strength. Furthermore, Na3Ga0.75Al0.25F6:0.35Cr3+ exhibited high luminous efficiency and the emission intensity remained 81% at 423 K compared with the initial value at 298 K. The structural confinement and the electron–phonon coupling (EPC) effect may account for its good thermal stability. Finally, a pc-NIR-LED device with a photoelectric conversion efficiency of 6.53% at 350 mA was fabricated by combining the as-prepared NIR phosphor and a blue InGaN chip, and its applications in night vision and medical fields were further investigated. This work will promote the development of NIR phosphors with tunable luminescence properties.
Qinghong Meng,Yuning Zhang,Xuejiao Wang,Xiangming Li,Wanjun Yu,Zhijun Xu,Ji-Guang Li
Broadband near-infrared (NIR) emission phosphor with combined high external quantum efficiency (EQE, >30%) and excellent thermal stability requires further inquiry. The crystal/band structure analysis using X-ray diffraction (XRD), diffuse reflectance spectra, and density functional theory (DFT) calculation for the Y 2 CaAl 4− x Ga x ZrO 12 garnets yielded a suitable x = 4.0 host for the exploration of the novel Y 2 CaGa 4− y ZrO 12 : y Cr 3+ (YCAGZO:Cr) NIR phosphors. The comprehensive investigation using Rietveld refinement and photoluminescence spectroscopy produced the optimal YCAGZO:Cr ( x = 4.0, y = 0.04) phosphor with wideband NIR emission (center at ∼764 nm, bandwidth ∼137 nm), high EQE= 32.0% (absorption efficiency ∼43.3%), and outstanding thermal stability ( I 423 K / I 298 K =90.0%, Δ E a =0.36 eV). Further, the satisfactory luminescence (NIR output power of 34.78 mW and photoelectric conversion efficiency of 12.42% at 100 mA) and imaging performance of the fabricated pc-NIR-LED using this optimal garnet phosphor prove that this newly developed phosphor is a promising choice for constructing the pc-NIR-LED devices used in scenarios such as food quality detection, noninvasive medical inspection, and night vision.
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