Yixin Sun,Mengmeng Shang,Yining Wang,Yiying Zhu,Xiaole Xing,Peipei Dang,Jun Lin
Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are the ideal light source for next-generation NIR spectroscopy, and developing novel NIR phosphors with high performance is crucial to achieve a wide range of NIR pc-LED applications. In this work, NIR luminescent material Y2Mg2Al2Si2O12 (YMAS):2%Cr3+ with good quantum efficiency (79%) and excellent thermal stability (88%@100 °C) is prepared. Under 430 nm light excitation, YMAS:2%Cr3+ emits 620–1100 nm NIR light with a full-width at half maximum (FWHM) of 153 nm. Fluorescence decay curves, photoluminescence (PL) spectra, 7 K PL spectra, the Rietveld refinement, 27Al solid-state nuclear magnetic resonance (ss-NMR) spectra and time-resolved emission spectroscopy (TRS) confirm that Cr3+ has two different luminescence centers in the YMAS lattice. Benefiting from the site elimination strategy, the double luminescence centers are proven to be derived from Cr3+ ions occupying the two sites [Al1O6] and [Al2O4]. The NIR packaging device prepared using YMAS:2%Cr3+ has outstanding NIR output power and photovoltaic conversion efficiency as high as 45.7 mW@100 mA and 16.7%@100 mA, respectively. Owing to the excellent performance of the YMAS:2%Cr3+ sample, it presents excellent practical performance in plant growth, bioimaging, non-destructive testing and night vision.
Hai Guo,Zhigang Zheng,Liming Teng,Rongfei Wei,Fangfang Hu
In this paper, a series of Bi 3+ and Eu 3+ single-doped as well as Bi 3+ ,Eu 3+ co-doped Ba 9 Y 2 Si 6 O 24 samples were synthesized through a simple high-temperature solid-state reaction method. Their crystal structures, morphologies, luminescent properties, temperature-dependent emission spectra , decay curves and quantum efficiencies were investigated in detail. Upon ultraviolet light excitation, Bi 3+ single-doped samples exhibited blue and green emissions peaking at 408 and 501 nm, corresponding to the 3 P 1 – 1 S 0 transition of Bi 3+ ions. The spectral analysis indicated that there were two different luminescent centers of Bi 3+ ions due to different occupancies in Ba 9 Y 2 Si 6 O 24 host lattice. And the highest quantum efficiency can reach 64.5% in Ba 9 Y 2 Si 6 O 24 :0.024Bi 3+ phosphor. The remarkable spectral overlap between the emission spectra of Bi 3+ ions and the excitation spectra of Eu 3+ ions indicated the exist of energy transfer from Bi 3+ to Eu 3+ . The efficient energy transfer from Bi 3+ to Eu 3+ has been investigated in detail and resulted in that tunable and white-light emission can be obtained by modulating Eu 3+ doping concentration. White emission can be realized with the CIE coordinates of (0.357, 0.345) and quantum efficiency of 57.6% for Ba 9 Y 2 Si 6 O 24 :0.024Bi 3+ ,0.02Eu 3+ . The above results demonstrate that Ba 9 Y 2 Si 6 O 24 :Bi 3+ ,Eu 3+ may be a potential candidate for ultraviolet (UV) driven white light-emitting diodes (w-LEDs).
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