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Highly efficient rare-earth-free deep red emitting phosphor La <sub/>2</sub> Li <sub/>1?y</sub> Sb <sub/>1?x</sub> O <sub/>6</sub> : <i>x</i> Mn <sup>4+</sup> , <i>y</i> Mg <sup>2+</sup> : application in high-power warm w-LEDs
摘要： Phosphor-in-glass (PiG), which serves as both a luminescent convertor and organic encapsulation material in high-power white light-emitting diodes (w-LEDs), has become a prospective research hotspot owing to its high transparency and thermal stability. However, YAG:Ce3+ PiG-based LED devices still suffer from a lack of a red component. Therefore, the development of red phosphors with excellent quantum efficiency and superior thermal stability is urgent. Herein, a highly efficient La2Li1?ySb1?xO6:xMn4+,yMg2+ red phosphor with a broadband emission ranging from 670 to 720 nm was fabricated via a conventional solid-state reaction. By co-doping Mg2+ in La2LiSbO6:Mn4+, the emission intensity was enhanced significantly, which reaches as high as 10 times that of the single-doped La2LiSbO6:Mn4+. It is proposed that the Mg2+ dopant can compensate imbalanced charges for the substitution of Sb5+ by Mn4+ and interrupt adverse energy transfer among the Mn4+ activators. Impressively, a maximum quantum yield of up to 80.3% is achieved and about 80% emission intensity is retained at the temperature of 423 K. Furthermore, the crystal field strength (Dq) and Racah parameters (B and C) together with the nephelauxetic ratio (b1) were calculated based on the obtained spectroscopic data. By embedding the red-emitting La2LiSbO6:Mn4+,Mg2+ phosphor and yellow-emitting YAG:Ce3+ phosphor into TeO2-based glass, an inorganic PiG composite as a color converter to replace organic silicone was acquired. The excellent optical parameters and tunable chromaticity feature of the fabricated w-LEDs were achieved by adjusting the mass ratio of La2LiSbO6:Mn4+,Mg2+ to YAG:Ce3+ in the PiG plate, where the correlated color temperature changed from cool white (6555 K) to warm (4130 K) and the color rendering index increased from 73.7 to 86.6 under an operating current of 300 mA.
关键词： Phosphor-in-glass,quantum yield,red phosphor,Mg2+,thermal stability,w-LEDs,Mn4+
更新于2025-11-20 15:33:11
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Novel Ca2GdTaO6:Mn4+,M (M = Li+, Na+, K+, and Mg2+) red phosphors for plant cultivation light-emitting diodes: Synthesis and luminescence properties
摘要： Recently, Mn4+-activated red phosphors are becoming potential color converters for application in indoor plant cultivation light-emitting diodes, owing to their satisfactory luminescence properties as well as low cost. Herein, novel Mn4+-activated double perovskite-type Ca2GdTaO6 phosphors have been synthesized by a high-temperature solid-state reaction method in air, which exhibited a broad excitation band with two peaks locating at 355 nm and 496 nm in range of 250-600 nm and had an intense red emission peaking at 676 nm due to Mn4+:2Eg→4A2g spin-forbidden transition ranging from 650 to 750 nm under 355 nm excitation. Concentration-dependent luminescence properties were studied. The optimal Mn4+ doping concentration in Ca2GdTaO6 host was 0.004, and the concentration quenching mechanism was determined to be a dipole-dipole interaction among Mn4+ ions. Furthermore, the Ca2GdTaO6:0.004Mn4+ phosphor possessed the internal quantum efficiency up to 33% when excited at 355 nm. Besides, the decay lifetimes of Ca2GdTaO6:Mn4+ presented a reasonable downward trend with increasing Mn4+ concentration. In addition, the effect of charge compensation (co-doping of Li+, Na+, K+, and Mg2+ ions) on the luminescent properties of Ca2GdTaO6:Mn4+ phosphors was also investigated.
关键词： Indoor plant cultivation,Ca2GdTaO6,Mn4+,Double perovskite,Luminescence properties,Red phosphor
更新于2025-11-20 15:33:11
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Alcohol-Guided Growth of Two-Dimensional Narrow-Band Red-Emitting K2TiF6:Mn4+ for White Light-Emitting Diodes
摘要： The use of red phosphors with low light-scattering loss could improve the luminous efficacy and color rendering of white light-emitting diodes (LEDs). Thus, the discovery of such phosphors is highly desired. In this work, high-efficiency two-dimensional red-emitting K2TiF6:Mn4+ (KTFM) were synthesized via an alcohol-assisted coprecipitation route. The synergistic effects of 1-propanol and hydrofluoric acid (HF) on the growth of KTFM microsheets (MSs) were studied through the first-principles calculations, which revealed that 1-propanol promoted the growth of KTFM MSs by preferentially adsorbing on the H-terminated K2TiF6 (001) surface. The photoluminescence quantum efficiency (QE) of Mn4+-activated K2TiF6 MSs was highly related to their size and thickness. The morphology-optimal KTFM MSs presented high internal QE (> 90 %), external QE (> 71%), and thermal quenching temperature (102% at 150 °C relative to that at 25 °C). A prototype phosphor-converted LED with KTFM as the red-emitting component showed an excellent color rendition (Ra = 91, R9 = 79) and high luminous efficacy (LE =156 lm/w).
关键词： light emitting diode,two-dimensional material,Narrow band,K2TiF6:Mn4+,backlight,red emission
更新于2025-11-14 17:04:02
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Highly efficient and thermally stable of a novel red phosphor Sr3NaSbO6:Mn4+ for indoor plant growth
摘要： Far red-emitting Mn4+-activated oxide phosphor based on the substitution of Mn4+ for Sb5+ in the lattice of Sr3NaSbO6 (SNSO) was prepared via solid state reaction process. The crystal structure of the host was carefully discussed and studied. The resultant phosphors were characterized by X-ray powder diffraction, fluorescence spectra, ultraviolet-visible diffuse reflectance spectra, temperature-dependent emission spectra (298–548 K), luminescence decay curves and electroluminescence spectra. Excitation and emission spectra indicated that the sample had a wide excitation band in UV(250–400 nm) and exhibited the strong emission band centered at 695 nm. The band structure for SNSO was calculated based on the density functional theory, and the bandgap value of SNSO host is ～2.92 eV. In addition, the mechanism of quenching concentration and energy-transfer of SNSO:Mn4+ were explored and analyzed in detail through calculation. The UV–Vis diffusion reflectance spectra demonstrated that samples had strong absorption (200–550 nm) in the ultraviolet(UV) and near-ultraviolet (NUV) region. The thermal stability of SNSO:Mn4+ was excellent (I423K/I273K = 39.84%). The internal quantum efficiency is 56.2%. In brief, the prepared phosphors had potential application in indoor plant growth as a LED lamp.
关键词： Sr3NaSbO6:Mn4+,Far red-emitting LED,Photoluminescence,Optical properties,Plant growth
更新于2025-09-23 15:23:52
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Novel emission bands of Na2TiF6:Mn4+ phosphors induced by the cation exchange method
摘要： A series of Na2TiF6:xMn4+ samples were prepared by the cation exchange method. Visible QC behavior and the strongest ZPL peaks were observed for these samples. The characteristic of the visible QC behavior is that PL intensity at 620 nm is 1.61 times as high as PLE intensity at 476 nm. The mechanisms of these phenomena were discussed, and the color purity, crystal-field and nephelauxetic effect, the critical distance and the multipolar interaction for the samples were determined. The result shows that the Mn4+ ions are located at a strong crystal field and the concentration quenching of Mn4+ is from the quadrupole-quadrupole interaction. The slightly increase of nephelauxetic ratio causes the slightly blue shift of emission. The color-purity and chromaticity coordinates of the optimal sample suggests that the strongest ZPL makes its red emission with high color-purity. Thus, Na2TiF6:0.08Mn4+ is a potential red-emitting phosphor for blue light-based WLEDs.
关键词： Fluorides,Photoluminescence,Mn4+,Red emitting phosphor,Visible quantum cutting
更新于2025-09-23 15:23:52
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Simultaneously enhanced far-red luminescence and thermal stability in Ca3Al4ZnO10:Mn4+ phosphor via Mg2+ doping for plant growth lighting
摘要： Non-rare-earth-based Ca3Al4ZnO10:Mn4+,Mg2+ (CAZO:Mn4+,Mg2+) phosphors with admirable luminescence performance and great potential as far-red light source for plant growth light-emitting diodes (LEDs) were reported in this paper. The concentration-dependent optical properties of the as-prepared phosphors were investigated in detail. Under ultraviolet-light excitation at 358 nm, the composition-optimized CAZO:0.4%Mn4+,14%Mg2+ phosphor showed an intense broad far-red emission band in the 625-830 nm wavelength range with a maximum at 714 nm, which was due to the 2Eg→4A2g transition of Mn4+ ions. The luminescence intensity of the CAZO:0.4%Mn4+,14%Mg2+ phosphor was about 1.82 times higher than that of CAZO:0.4%Mn4+ phosphor, and the corresponding mechanism for the luminescence enhancement via Mg2+ doping was studied. Amazingly, the internal quantum efficiency of the CAZO:0.4%Mn4+ phosphor was increased from 31 to 60% after co-doping 14 mol% Mg2+. The CAZO:0.4%Mn4+,14%Mg2+ phosphor also showed enhanced thermal stability compared with the CAZO:0.4%Mn4+ counterpart. It was found that, for CAZO:0.4%Mn4+,14%Mg2+ phosphor, the emission intensity at 423 K (150 oC) was about 51% of that at 303 K (30 oC), while the corresponding activation energy was determined to be 0.245 eV.
关键词： thermal stability,plant growth,phytochrome,far-red emissions,LEDs.,Mn4+ ions
更新于2025-09-23 15:22:29
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Synthesis and photoluminescence properties of high thermal stability Mn4+ in orthorhombic SrLa2Mg2W2O12 red phosphor for warm w-LEDs
摘要： We successfully synthesized SrLa2Mg2W2O12:xMn4+ (x = 0.002, 0.004, 0.006, 0.008, 0.010, 0.012, 0.014) phosphors through a high-temperature solid-state reaction. The phase of sample was shown by X-ray powder diffraction (XRD). The morphology of the sample was observed by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM), which showed the irregular morphology of SrLa2Mg2W2O12 (SLMW) powders. Additionally, the photoluminescence excitation (PLE), emission (PL) and ultraviolet–visible reflection spectra were also presented. As shown in results, the phosphor could be stimulated by the ultraviolet (UV) and near ultraviolet (NUV) light and then exhibited far-red emission (697?nm). The optimum doping concentration of Mn4+ is 1?mol%. The thermal stability of phosphors has been investigated and discussed (I423K/I298K = 64.6%), and the internal quantum efficiency (IQE) of SLMW:0.01Mn4+ phosphors is as high as 51.2%. Finally, a far-red light-emitting diodes (LEDs) was fabricated by combining a 365?nm near-ultraviolet InGaN chip with SLMW:0.01Mn4+ phosphor. The Color Rendering Index (CRI), correlated color temperature (CCT) and luminescent efficiency (LE) values were 29.5, 1159?K and 5.6?lm/W, respectively. All of these indicated that SLMW:Mn4+ as a far-red phosphor can be applied to LEDs lamp and it has enormous potential applications in white light-emitting diodes (w-LEDs).
关键词： SrLa2Mg2W2O12:Mn4+,far-red emission,thermal stability,w-LEDs,phosphor
更新于2025-09-23 15:21:01
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Structure identification and strongly enhanced luminescence of Sr9Y2(WO6)4: Mn4+ phosphors by co-doping Mg2+ ions for plant growth LEDs
摘要： In this paper, we reported a novel far-red emitting phosphor Sr9Y2(WO6)4: Mn4+ and alkaline earth metal Mg2+ ion co-doped phosphor Sr9Y2(WO6)4: Mn4+, Mg2+. Systematical studies on its crystal structure and luminescence properties are carried out. X-ray powder diffraction confirmed that the pure phase Sr9Y2(WO6)4: Mn4+ and Sr9Y2(WO6)4: Mn4+, Mg2+ phosphors show a single phase. Upon 350 nm excitation, the phosphors could emit far-red emission in the range of 600–800 nm, peaking at 680 nm (14,706 cm?1) due to the 2Eg→4A2g transition, with broad spectra overlap with the absorption band of phytochrome PFR. The optimal doping concentration, concentration quenching mechanism, as well as the content and temperature dependent decay times of Sr9Y2(WO6)4: Mn4+ and the related mechanisms are deeply studied. Ultimately, a far-red light emitting diode lamp is fabricated by exciting a far red phosphor Sr9Y2(WO6)4: 0.0025Mn4+, 0.01Mg2+ using a 365 nm n-UV illuminating LED chip. Our studies have shown that Sr9Y2(WO6)4: Mn4+, Mg2+ phosphors have potential application in controlling or adjusting plant growth in plant-lighting.
关键词： Sr9Y2(WO6)4: Mn4+,Plant growth,Phosphors,Far-red emitting,Mg2+
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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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