As energy consumption intensifies, energy saving and environmentally friendly phosphor-converted white light-emitting diodes (pc- w LEDs) have become the current research hotspots. The garnet-based CaY 2 Al 4 SiO 12 (CYAS) phosphors, with their abundant lattice sites and stable physical properties, are ideal candidates as phosphor hosts. Through comprehensive experimental and theoretical analyses, including XRD/Rietveld refinement and density functional theory (DFT) calculations, it was determined that Bi 3+ /Tb 3+ /Sm 3+ ions preferentially occupy the Y 3+ lattice site. The luminescence properties and thermal stability of CYAS: Bi 3+ /Tb 3+ /Sm 3+ have been extensively investigated. The quantum yield (QY) has been enhanced to 48.3 % due to energy transfer (ET), which is not a significant difference compared to existing phosphors, and by superposition of blue (Bi, 3 P 1 → 1 S 0 ), green (Tb, 5 D 4 → 7 F 5 ), and red (Sm, 4 G 5/2 → 6 H 5/2 ) emission, resulting in tunable spectrum and high-quality, full-spectrum white light emission. Finally, the w LED device with high color rendering index (CRI, 87), high luminous efficiency (LE, 74 lm·W −1 ), and low correlated color temperature (CCT, 4747.56 K) were fabricated by a remote ‘encapsulation’ packaging strategy, suggesting that the phosphor can be applied to high quality white light illumination.
X.Z. Zheng,Z.Y. Ye,Y.F. Zhang,L. Yue,Y.F. Lei,W.B. Dai
With the growing concern about energy consumption, white light-emitting diodes( w LEDs), as the fourth generation of lighting sources, are highly scrutinized by researchers. A series of Bi 3+ /Tb 3+ /Sm 3+ (co)doped BaY 2 Si 3 O 10 phosphors were prepared by traditional solid-state method, and the phase purity was analyzed by X-ray diffraction. In this work, Bi 3+ /Tb 3+ /Sm 3+ theoretically occupies the Ba/Y sites, and this conjecture is also proved by spectral analysis. Under near ultraviolet ( n UV) light excitation, Bi 3+ /Tb 3+ /Sm 3+ is respectively used as the blue ( 3 P 1 → 1 S 0 )/green ( 5 D 4 → 7 F j )/red ( 4 G 5/2 → 6 H j ) luminescence center. Due to the energy transfer (ET) efficiency between Bi 3+ /Sm 3+ is not ideal, Tb 3+ is introduced as a bridge to improve the ET efficiency of the whole system to achieve spectral tunability and application in w LEDs. And at different excitation wavelengths, Bi 3+ emits a wide range of blue to cyan light because it occupies two cation sites. We selected a proper excitation wavelength and obtained an emission spectrum covering the whole visible region. The CIE color coordinates (0.3487, 0.3313), the correlated color temperature (CCT, 4773.61 K), quantum efficiency (QE, 47.62 %), and thermal stability ( T 50 = 537 K) of BaY 2 Si 3 O 10 : Bi 3+ /Tb 3+ /Sm 3+ are discussed in depth, Lu 3+ was used instead of Y 3+ to improve the thermal stability of BYS. Its excellent luminescence performance indicates that this phosphor has potential applications in n UV w LEDs.
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