Ligand-Passivated Eu:Y 2 O 3 Nanocrystals as a Phosphor for White Light Emitting Diodes (original) (raw)
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Beilstein Journal of Nanotechnology, 2019
Phosphors can serve as color conversion layers to generate white light with varying optical features, including color rendering index (CRI), high correlated color temperature (CCT), and luminous efficacy. However, they are typically produced under harsh synthesis conditions such as high temperature, high pressure, and/or by employing a large amount of solvent. In this work, a facile, water-based, rapid method has been proposed to fabricate lanthanide-doped hydroxide-based phosphors. In this sense, sub-micrometer-sized Y(OH)3:Eu3+ particles (as red phosphor) were synthesized in water at ambient conditions in ≤60 min reaction time. The doping ratio was controlled from 2.5–20 mol %. Additionally, first principle calculations were performed on Y(OH)3:Eu3+ to understand the preferable doping scenario and its optoelectronic properties. As an application, these fabricated red phosphors were integrated into a PDMS/YAG:Ce3+ composite and used to generate white light. The resulting white ligh...
CaLaP3O10 : Dy3+ /Eu3+ phosphor powders were prepared by a facile solegel method. These samples were thermally treated at 900 C for 6 h to get monazite type structure with monoclinic unit cell. The phase, morphology and optical properties of phosphor samples were characterized by X-ray diffraction patterns, Fourier transform infrared spectra, scanning/transmission electron microscope images, and photoluminescence excitation and emission spectra. The Dy3+ /Eu3+ ions co-doped samples showed warm white-light emissions with lower correlated color temperature values at higher Eu3+ ion concentrations. The near-ultraviolet (NUV) excitation and the effective energy transfer form Dy3+ to Eu3+ ions can make these phosphors as potential candidates for NUV excitation based white light-emitting diodes.
Light: Science & Applications, 2016
Single-phased, high-color-rendering index (CRI) white-light phosphors are emerging as potential phosphor-converted white-light-emitting diodes (WLEDs) and as an alternative to blends of tricolor phosphors. However, it is a challenge to create a high CRI white light from a single-doped activator. Here, we present a high CRI (Ra 5 91) white-light phosphor, Sr 5 (PO 4) 3-x (BO 3) x Cl:Eu 21 , composed of Sr 5 (PO 4) 3 Cl as the beginning member and Sr 5 (BO 3) 3 Cl as the end member. This work utilized the solid-solution method, and tunable Eu 21 emission was achieved. Color-tunable Eu 21 emissions in response to structural variation were observed in Sr 5 (PO 4) 3-x (BO 3) x Cl solid solutions. This was further confirmed using X-ray Rietveld refinement, electron paramagnetic resonance spectroscopy, and in the photoluminescence spectra. The color-tunable emissions included the white light that originated from the combination of the blue emission of Sr 5 (PO 4) 3 Cl:Eu 21 and an induced Eu 21 yellow emission at approximately 550 nm in the solid solution. Importantly, the white-light phosphors showed a greater R9 5 90.2 under excitation at 365 nm. This result has rarely been reported in the literature and is greater than that of (R9 5 14.3) commercial Y 3 A l5 O 12 :Ce 31-based WLEDs. These findings demonstrate the great potential of Sr 5 (PO 4) 3-x (BO 3) x Cl:0.04Eu 21 as a white-light phosphor for near-UV phosphor-converted WLEDs. These results also provide a shortcut for developing a high CRI white-light phosphor from a single Eu 21-doped compound.
Investigation of MAl2−xSixO4−xNx:Eu 2+ phosphor for improving luminescence properties of white LEDs
Indonesian Journal of Electrical Engineering and Computer Science, 2022
We implement a solid-state reaction technique to MAl2−xSixO4−xNx (M = Ca, Sr, Ba) as well as its variant doped with Eu at 1300-1400 °C in a nitrogen hydrogen environment. Then, we measure the solubility of (SiN) + in MAl2O4. By replacing (AlO) + with (SiN) + , whose solubility is dependent on M cations, nitrogen may be integrated into MAl2O4. (SiN) + has poor solubility in CaAl2O4 (x ≈ 0.025) and SrAl2O4 lattices (x ≈ 0.045) but a considerable integrated quantity of (SiN) + against BaAl2O4 (x ≈ 0.6). Because of the low solubility of (SiN) + , incorporation of (SiN) + barely affects the luminescence characteristics of MAl2O4 when doped with Eu 2+ (M = Ca, Sr), resulting in discharges in green as well as blue at nearly constant wavelengths measured at 440 as well as 515 nm, respectively. With certain concentrations of (SiN) + as well as Eu 2+ , Eu 2+-doped BaAl2−xSixO4−xNx emits one wide green discharge line under a maximum within the region 500-526 nm. Furthermore, once we add nitrogen, both the excitation as well as discharge lines for Eu 2+ exhibit one substantial redshift. BaAl2−xSixO4−xNx: Eu 2+ is a compelling transmuting phosphor that can be utilized for white light-emitted diodes (WLED) devices because of its efficient stimulation in the range of 390-440 nm radiation.
Journal of Materials Chemistry, 2012
A new color-tunable Eu 2+-doped sodium aluminium silicate, Na 2ÀxÀy Al 2Àx Si x O 4 :yEu 2+ (0 # x # 1), phosphor system was investigated as a novel candidate for phosphor-converted white light-emitting diode (LED) applications and successfully synthesized by wet chemical methods based on the hydrolysis of tetraethyl orthosilicate (TEOS). Different crystal structures and emission spectra were obtained by varying the ratio of Al to Si in the phosphor Na 2Àx Al 2Àx Si x O 4 with x value ranging from 0.25 to 0.55. The Na 2ÀxÀy Al 2Àx Si x O 4 :yEu 2+ phosphor system emitted a maximum intensity at 470-600 nm when using a 395 nm excitation wavelength, and the emission was strongly affected by the crystal structures determined by the x value. Substitution of Eu 2+ affected the center wavelength and emission intensity due to changes in the crystal-field effect, which was strongly dependent on the crystal structure. The LED device exhibited an excellent color-rendering index R a of 93 at a correlated color temperature of 4258 K with CIE color coordinates of (0.3629, 0.3427) under a 20 mA forward-bias current. Based on these results, we are currently evaluating the potential application of Na 2ÀxÀy Al 2Àx Si x O 4 :yEu 2+ as a white-emitting UV-convertible phosphor.
Ca2Al3O6F:Eu2+: a green-emitting oxyfluoride phosphor for white light-emitting diodes
Journal of Materials Chemistry, 2012
A novel green-emitting phosphor Ca 2 Al 3 O 6 F:Eu 2+ was synthesized and its photoluminescence (PL) properties were investigated for application in white light-emitting diodes (w-LEDs). This phosphor shows good absorption ranging from the ultraviolet to the blue region and a broad green emission band centered at 502 nm. The concentration quenching mechanism and fluorescence lifetime of Eu 2+ emission in the Ca 2 Al 3 O 6 F:Eu 2+ phosphors have been investigated. The key parameters for the fabrication of w-LED lamps, such as the temperature-dependent photoluminescence, microstructure and morphology, CIE value and quantum efficiency of Ca 2 Al 3 O 6 F:Eu 2+ phosphors, have also been studied. The above results indicate that Ca 2 Al 3 O 6 F:Eu 2+ is a good candidate as a green component for near UV-excited w-LEDs.
Journal of the American Ceramic Society, 2018
A series of novel red-emitting Ca 8 ZnLa 1-x Eu x (PO 4) 7 phosphors were successfully synthesized using the high-temperature solid-state reaction method. The crystal structure, photoluminescence spectra, thermal stability and quantum efficiency of the phosphors were investigated as a function of Eu 3+ concentration. Detailed analysis of their structural properties revealed that all the phosphors could be assigned as whitlockite-type β-Ca 3 (PO 4) 2 structures. Both the PL emission spectra and decay curves suggest that emission intensity is largely dependent on Eu 3+ concentration, with no quenching as the Eu 3+ concentration approaches 100%. A dominant red emission band centered at 611nm indicates that Eu 3+ occupies a low symmetry sites within the Ca 8 ZnLa (PO 4) 7 host lattice, which was confirm by Judd-Ofelt theory. Ca 8 ZnLa 1-x Eu x (PO 4) 7 phosphors exhibited good color coordinates (0.6516, 0.3480), high color purity (∼96.3%) and high quantum efficiency (∼78%). Temperature-dependent emission spectra showed that the phosphors possessed good thermal stability. A white light-emitting diode (LED) device were fabricated by integrating a mixture of obtained phosphors, commercial green-emitting and blue-emitting phosphors into a near-ultraviolet LED chip. The fabricated white LED device emits glaring white light with high color rendering index (83.9) and proper correlated color temperature (5570 K). These results demonstrate that the Ca 8 ZnLa 1-x Eu x (PO 4) 7 phosphors are a promising candidate for solid state lighting.