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Tunable photoluminescence from YTaO4: Bi3+ for ultraviolet converted pc-WLED with high chromatic stability
摘要： To avoid the color drift of WLED at high temperature, it is significant to develop color stable luminescent materials. Herein we report on a phosphor YTaO4:Bi3+ with a stable blue emission upon ultraviolet excitations even as the temperature changes between 300 and 480 K. Upon excitations into host absorptions a tunable blue emission can be led from 400 nm to 450 nm due to the enhanced energy transfer efficiency from host to bismuth ions as the concentration of bismuth increases. As excitation scheme is modulated between 355 and 370 nm the white emission can be achieved in the compound of YTaO4 single doped with Bi3+, which has rarely been reported previously. For proof of concept the prototype WLEDs have been demonstrated with the phosphor YTaO4:Bi3+ and the 365 nm InGaN chips under different driving currents. Our findings make it possible for single phase white emitting phosphors activated by a single ion of Bi3+ for WLEDs, and also can inspire to develop WLED devices with high chromatic stability.
关键词： YTaO4:Bi3+,ultraviolet excitation,chromatic stability,white light emitting diodes,phosphor
更新于2025-09-23 15:19:57
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Green and Orange Emissive Carbon Dots with High Quantum Yields Dispersed in Matrices for Phosphor-Based White LEDs
摘要： Carbon dots (CDs) have aroused more interest in the LED phosphor. High quantum yields and suppressing solid-state luminescence quenching are the key factors for CDs to prepare high-quality phosphors. In this work, orange and green emissive CDs (O-CDs and G-CDs) with very high absolute quantum yields (abs. QYs: 85.19% at natural pH and 96.12% at pH 9.0 for G-CDs; 34.89% in aqueous solution and 77.54% in ethanol for O-CDs) were achieved. Then, sodium silicate and PVA were selected as matrices to suppress their aggregation-induced quenching effect. Phosphor powder was prepared by microwave-assisted pyrolysis of sodium silicate and films by self-assembling of PVA in the presence of the CDs. The phosphor powder simultaneously containing G-CDs and O-CDs (G-O-CDs-phosphor) presents bright yellow fluorescence but owns a relatively low abs. QY. However, O-CDs/PVA and G-CDs/PVA phosphor films possess very high abs. QYs of 51.51% and 72.81%, respectively. LEDs constructed by coating G-O-CDs-phosphor on a blue chip exhibited a cool white color and a color rendering index (CRI) of 78. Interestingly, high-quality warm white LEDs owning a superior CRI of 93 were achieved by the O-CDs/PVA and G-CDs/PVA films. By comparison, PVA is more suitable to maintain the high performance of G-CDs and O-CDs for high-quality phosphors.
关键词： White LEDs,Phosphor,Carbon dots,High quantum yield,Rhodamine B
更新于2025-09-23 15:19:57
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(Ba,Sr)LaZnTaO6:Mn4+ far red emission phosphors for plant growth LEDs: structure and photoluminescence properties
摘要： It is necessary to develop novel high-efficient red or far-red-emitting in order to facilitate the phosphor-converted light-emitting diodes (pc-LEDs) for plant growth. This work reports a series of novel far-red emitting (Ba,Sr)LaZnTaO6:xMn4+ phosphors with double perovskite structure synthesized by traditional high-temperature solid-state reaction (SSR) process. The crystal structure and morphology of (Ba,Sr)LaZnTaO6 are investigated by high-resolution TEM, SEM, and XRD Rietveld refinement. The photoluminescece properties are systematically explored and analyzed by diffuse reflection (DR) spectra, photoluminescence emission (PL) and excitation (PLE) spectra, decay curves and temperature-dependent spectra. Mn4+ ions occupy Ta5+ sites located at [TaO6] octahedral emitting red light with peak at 698 nm in BaLaZnTaO6:Mn4+ and 695 nm in SrLaZnTaO6:Mn4+ under n-UV and blue light excitation. The critical quenching concentration of Mn4+ was determined to be 0.008. The concentration quenching mechanism could be a dipole-dipole interaction between Mn4+ ions. In addtion, the PL intensity of (Ba,Sr)LaZnTaO6:xMn4+ phosphors decrease with increasing temperature. The SrLaZnTaO6:xMn4+ sample has better thermal stability than BaLaZnTaO6:xMn4+. Interestingly, (Ba,Sr)LaZnTaO6:0.008Mn4+ exhibits outstanding internal quantum efficiency (IQE ≥ 80 %). Fianally, the fabricated of LEDs are combined with SrLaZnTaO6:0.008Mn4+ phosphors combined with 460 nm InGaN chips, which emit blue and red light. Based on above properties, the rare-earth-free (Ba,Sr)LaZnTaO6:xMn4+ phosphors have great potentials to be serviced as far-red emitting phosphors in high-power plant growth LEDS.
关键词： double perovskite structure,phosphor-converted light-emitting diodes,internal quantum efficiency,far-red emitting,plant growth,Mn4+,thermal stability,photoluminescence,solid-state reaction
更新于2025-09-23 15:19:57
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The influence of phosphor particles on the water transport in optical silicones for LEDs
摘要： The reliability of LEDs decreases in moist environments. One potential gateway of moisture ingress, reducing the product lifetime is the lens. In white LEDs, phosphor particles are embedded into the optical silicone of the lens to convert the blue light emitted by the diode down in frequency and achieve a light output that appears white. In this study, the influence of these phosphor particles on the moisture sorption, permeation and diffusion in optical silicones is investigated by comparing two silicone resins that are commonly used in LEDs, both with and without the addition of phosphor particles. The results of two methods are compared: the wet-cup method and a gravimetric approach of dynamic vapour sorption (DVS). Diffusion coefficients between 20 and 75 C are reported as well as sorption isotherms, activation energy and sorption enthalpy. It is concluded that the addition of phosphor particles only has a very small impact on the moisture transport properties of the silicones.
关键词： Diffusion,Dynamic vapour sorption (DVS),Moisture transport,Phosphor particles,Silicone,LED
更新于2025-09-23 15:19:57
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trans-N-(Heterocyclic Carbene) Platinum(II) Acetylide Chromophores as Phosphors for OLED Applications
摘要： A family of complexes of the type trans-(NHC)2Pt(C≡C-Ar)2 (NHC = N-heterocyclic carbene and Ar = substituted phenyl or 4-pyridyl) exhibits blue or blue-green phosphorescence. The photoluminescence is 10 – 50 fold more efficient when the materials are in dispersed in a solid poly(methyl methacrylate) glass compared to in THF solution. The phosphorescence quantum efficiencies in PMMA glass range from 0.20 – 0.65, varying with the structure of the aryl acetylide ligands. Organic light emitting diodes (OLEDs) were fabricated by thermal evaporation, using bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO) as the host and 15% of the trans-(NHC)2Pt(C≡C-Ar)2 complexes as the dopant/emitters. Most of the OLEDs display good performance, with EL spectra that closely match the PL in the PMMA glass. The best performing materials have peak EQE ranging from 9.6 – 14.1%, with deep blue spectral profiles (minimum CIE (0.16,0.13). Several of the complexes have deep HOMO levels and they display poor EL performance attributed to inefficient host to emitter hole transfer.
关键词： OLED,blue emission,platinum acetylide,platinum N-heterocyclic carbene,phosphor
更新于2025-09-23 15:19:57
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Strong Narrow Red Emission in a Perturbed Fergusonite System: Y3Mg2Nb3O14:Eu3+ for White LED Applications
摘要： A series of intense red-emission phosphors, Y3Mg2Nb3O14:Eu3+, with higher color purity were prepared via the conventional high-temperature ceramic route. The influence of Mg2+ ion incorporation in the highly symmetrical YNbO4 lattice on the luminescence properties was studied using powder x-ray diffraction, scanning electron microscopy with energy dispersive spectrometry, UV–visible absorption spectroscopy, and photoluminescence measurements. The developed phosphors crystallize into a monoclinic fergusonite-type structure with a C2/c space group even with the addition of Mg into the system. These phosphors display intense, sharp, red emission with a maximum at 613 nm under near-UV excitation. The photoluminescence studies suggest that Mg addition perturbs the A site network forming cation pairs of Eu3+-Y3+, Eu3+-Mg2+, and Eu3+-Eu3+ connected with O2? ions. The preferential occupation of cations in the A site network by the incorporation of Mg2+ ions in the YNbO4 host lattice induces Eu3+-Eu3+ separation and results in intense, sharp, red emission due to increased radiative probabilities. Moreover, the color purity of the Y3?xMg2Nb3O14:xEu3+ phosphor could achieve 92.4% that is attributed to the narrow full width at half maximum (FWHM ≈ 4 nm) of the red emission peaking at 613 nm. More importantly, the luminescence intensity of the developed phosphor is 9.4 times greater than that of the Philip’s red phosphor under near-UV excitation. Because of the intriguing red luminescence, phosphors exhibit Commission Internationale de l’Elcairage color coordinates (0.63, 0.35) close to the National Television System Committee standards, low correlated color temperature values for warm white lighting, and greater color purity (92.4%) for improving the color rendering index, which makes them a potential candidate for use in the fabrication of white light-emitting diodes.
关键词： perturbation,luminescence,fergusonite,Red phosphor
更新于2025-09-23 15:19:57
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Spectroscopic investigation of La7Ta3W4O30:Sm3+ orange-red phosphor for white LEDs
摘要： The novel orange-red light emitting La7Ta3W4O30:xSm3+ (x = 0.005–0.20) phosphors were synthesized via the solid-state reaction method. The crystal structure, photoluminescence (PL) properties, optimum concentration, color purity, decay life, and thermal stability of the samples were systematically studied. Under the excitation of 404 nm, La7Ta3W4O30:Sm3+ emits intense orange-red light at 597 nm. The PL spectra of La7Ta3W4O30:Sm3+ phosphors are ascribed to the 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm3+ ions. The concentration quenching occurs at the doping level of 1 mol%. The quenching temperature is higher than 500 K. Finally, a white LED (w-LED) with the Commission Internationale de L’Eclairage (CIE) chromaticity coordinates of (0.312, 0.296) and good color rendering index (Ra) of 86 was fabricated. As a consequence, all the results suggest that the orange-red phosphors La7Ta3W4O30:Sm3+ have potential applications in w-LEDs structures.
关键词： Phosphor,Luminescence,Tungstate,La7Ta3W4O30:Sm3+
更新于2025-09-23 15:19:57
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A novel Mn4+ doped red phosphor composed of MgAl2O4 and CaAl12O19 phases for Light-Emitting Diodes
摘要： The red emitters based on CaAl12O19:Mn4+ have been attracting extensive attentions due to their advantages of rare-earth-free and chemical stability. However, their relatively low luminescent efficiencies will seriously hinder their application for light-emitting diodes (LEDs). In this regard, one of promising red phosphors of CaAl12O19:Mn4+ was synthesized with enhanced luminous efficiency by introducing the coexistence phase of MgAl2O4. Importantly, an approximately 5 times enhancement of integrated intensity on emission spectrum was observed in the coexistence phase comparing of these single one. Their crystalline structures, morphologies, photoluminescence as well as the mechanism of improved luminescence were systematically investigated. Exciting them by using near-ultraviolet or blue LEDs, an efficient red emission was achieved with a maximum peak at ~ 658 nm. In order to evaluate the potential application, a warm white LED and a plant-growth LED are fabricated by using the prepared phosphors in combination with YAG:Ce3+ and InGaN-based blue chips.
关键词： MgAl2O4,LEDs,CaAl12O19,red phosphor,Mn4+
更新于2025-09-23 15:19:57
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Luminescent properties of Zn2+-doped CaAl12O19:Mn4+ deep-red phosphor for indoor plant cultivation
摘要： A series of CaAl12O19: 0.5%Mn4+ phosphors doped with different concentrations of Zn2+ were prepared via solid state reaction process. The micrographs and phases of powders were analyzed by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), respectively. The Photoluminescence excitation spectra(PLE) and emission spectra(PL) of CaAl12O19: 0.5%Mn4+ with varying Zn2+ concentrations were investigated, the result indicated that prepared samples after Zn2+-doping exhibited deep red emission (658 nm) under the excitation of ultraviolet (UV), near ultraviolet (NUV). PL spectra indicated that Zn2+-doping could remarkably enhance the luminescent intensity of CaAl12O19:0.5%Mn4+. When the doping concentration of Zn2+ was 4%, the emission intensity of Ca0.96Zn0.04Al12O19:0.5%Mn4+ was improved up to 2.2 times that of pure CaAl12O19:0.5%Mn4+. In addition, the emission band of phosphor is highly compatible with the absorption band of phytochrome PR(660 nm). Besides, the internal quantum efficiency (IQE) was up to 67.1%. All the obtained results indicated that CaAl12O19:Zn2+, 0.5%Mn4+ has potential application value in indoor plant cultivation.
关键词： Phosphor,Deep-red emission,CaAl12O19:Zn2+,Plant cultivation,Luminescence,Mn4+
更新于2025-09-19 17:15:36
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High-purity green emission in Yb3+/Ho3+ Co-doped BaIn6Y2O13 up-conversion phosphor
摘要： Yb3+-Ho3+ pairs doped BaIn6Y2O13 (BIY) phosphors were successfully prepared through sol-gel process, and the crystal structure and optical properties were investigated in detail. As-prepared samples exhibited strong green and weak red emission peaked at 549 nm and 652 nm originated from Ho3+ transitions of 5S2, 5F4 → 5I8 and 5F5 → 5I8 with 980 nm excitation, respectively. The dopant contents, pumping power and pulse width of excitation laser dependent up-conversion luminescence (UCL) spectra of samples were modulated to acquire the intense and high-purity green emissions. Moreover, possible dynamic UCL process from non-steady-state to steady-state between Yb3+ and Ho3+ was schematically proposed in detail. These results indicate that BaIn6Y2O13: Yb3+/Ho3+ phosphors with strong and pure green UC emissions are potential candidates in display and lighting technology.
关键词： Up-conversion,Phosphor,Green emission,Non-steady-state
更新于2025-09-19 17:15:36