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Heavy Atom Effect of Selenium for Metal-Free Phosphorescent Light-Emitting Diodes
摘要： Room-temperature phosphorescence from metal-free purely organic molecules has recently gained much interest. We devised metal-free organic phosphors by incorporating selenium (Se) to promote spin?orbit coupling by its nonmetal heavy atom effect. The Se-based organic phosphors showed bright phosphorescent emission in organic light-emitting diodes (OLEDs) and photo-excited phosphorescence in an amorphous film state. Large orbital angular momentum change (ΔL) during the electron transition process and heavy atom effect of Se render a PL quantum yield of 0.33 ± 0.01 and a high external quantum efficiency (EQE) of 10.7 ± 0.14% in phosphorescent LEDs. This work demonstrates the rational molecular design of metal-free organic phosphorescent emitters with Se as an alternative novel class of materials to the conventional organometallic phosphors for OLEDs.
关键词： organic light-emitting diodes,spin?orbit coupling,selenium,metal-free organic phosphors,phosphorescent LEDs,room-temperature phosphorescence
更新于2025-09-23 15:19:57
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Novel highly luminescent double-perovskite Ca2GdSbO6:Eu3+ red phosphors with high color purity for white LEDs: Synthesis, crystal structure, and photoluminescence properties
摘要： High-efficiency red-emitting phosphors are required to fabricate high-performance white light-emitting diodes (LEDs). Herein, the novel highly efficient Eu3+-activated Ca2GdSbO6 double-perovskite red phosphors with good thermal stability toward warm-white LEDs were reported. A series of Ca2Gd(1-x)EuxSbO6 red phosphors with different Eu3+ doping concentrations (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were synthesized by using high-temperature solid-state reaction method. Under the excitation of 396 nm near-ultraviolet light, these Ca2Gd(1-x)EuxSbO6 phosphors showed intense red emissions peaking at 612 nm due to the 5D0→7F2 transition of Eu3+ ions. The strongest luminescence intensity reached when Eu3+ doping concentration was x = 0.5, and the critical distance between Eu3+ activators was calculated to be 7.97 ?. The concentration quenching mechanism was due to the dipole-dipole interaction of Eu3+ ions. The CIE color coordinates of the optimal Ca2Gd0.5Eu0.5SbO6 phosphors were determined to be (0.6629, 0.3367), and the corresponding color purity reached about 94.9%. Importantly, the Ca2Gd0.5Eu0.5SbO6 phosphors revealed outstanding internal quantum efficiency of 73% and good thermal stability. The emission intensity of Ca2Gd0.5Eu0.5SbO6 phosphors at 423 K still remained about 73% of its initial value at 303 K. Finally, a prototype white LED device was fabricated by coating the phosphor blend of commercial blue-emitting BaMgAl10O17:Eu2+ and our as-prepared red-emitting Ca2Gd0.5Eu0.5SbO6 on a 395 nm LED chip. Under 20 mA driven current, the device showed bright warm-white light with CIE color coordinates of (0.3888, 0.3943), correlated color temperature of 3911 K, and color rendering index of 88.4. The results demonstrated that the developed novel red-emitting Ca2Gd0.5Eu0.5SbO6 phosphors could be used as potential color converters in white LEDs.
关键词： White LEDs,Photoluminescence,Ca2GdSbO6,Double-perovskite,Eu3+ ions,Red-emitting phosphors
更新于2025-09-23 15:19:57
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Novel red emitting LnTaO4: Eu3+ (Ln = La, Y) phosphors for warm white LEDs
摘要： LnTaO4: Eu3t (Ln ? La, Y) phosphors were synthesized by high-temperature solid-state reaction. Powder X-ray diffraction analysis confirmed the pure phase formation. Diffuse reflection spectra, excitation and emission spectra, the CIE chromaticity coordinates as well as the temperature-dependent emission spectra were investigated those phosphors. Upon near UV and blue excitation LnTaO4: Eu3t (Ln ? La, Y) show intense red emission of Eu3t. The optimum concentration of Eu3t in LaTa1-xEuxO4 phosphor was x ? 0.20, and concentration quenching mechanism was the electric dipole-dipole interaction. Furthermore, the critical transfer distance was obtained and the CIE chromaticity coordinates of LaTaO4: Eu3t samples were close to the National Television System Committee standard values. The temperature-dependent luminescence indicated LaTaO4: Eu3t exhibited moderate thermal stability. Those results suggested that LnTaO4: Eu3t (Ln ? La, Y) as red emitting phosphors could be potential candidates for white LEDs.
关键词： Luminescent properties,Red emitting phosphors,White LED,Thermal stability
更新于2025-09-23 15:19:57
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Luminescence properties of novel red-emitting phosphors Ba3B6Si2O16: Eu3+ for near-UV excited LED
摘要： A novel Eu3+ doped Ba3B6Si2O16 red-emitting phosphor was synthesized by a high temperature solid state reaction and its luminescence properties were investigated. All the phosphors are pure phase of triclinic Ba3B6Si2O16 in structure. Under 393 nm excitation, Ba3B6Si2O16: Eu3+ phosphor exhibits intense red emissions due to the characteristic f–f transitions of Eu3+ with the strongest emission peaks at 613 nm. The optimum doping concentration of Eu3+ is 0.09 and the corresponding critical distance is estimated to be 23.9 ?. The emission intensity decreases with increase of Eu3+ ion concentration(x>0.09) due to dipole-dipole interactions among Eu3+. Ba3B6Si2O16: Eu3+ phosphor exhibits high color purity (92%), good thermal stability (the activation energy of 0.2121 eV) and high quantum efficiency (36.5 %) with CIE chromaticity coordinates of (0.6460, 0.3534). These results indicate that Ba3B6Si2O16: Eu3+ phosphor can be anticipated as a red emitting phosphor for near-UV pumped white LEDs.
关键词： luminescence property,Eu3+ ions,phosphors
更新于2025-09-23 15:19:57
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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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Design of a Broadband NIR Phosphor for Security-Monitoring LEDs: Tunable Photoluminescence Properties and Enhanced Thermal Stability
摘要： Near-infrared (NIR) phosphors with capability for blue light to 850 nm broadband NIR emission conversion are highly desirable for security-monitoring LEDs. Targeted phosphor LaSc2.93-yGayB4O12(LSGB): 0.07Cr3+ (y = 0.6) is designed from the initial model of LaSc2.93B4O12(LSB): 0.07Cr3+ by chemical composition modification. The correlations among crystal-field environment, structural evolution, and luminescence properties of LSGB: 0.07Cr3+ (0 ≤ y ≤ 1.5) are elucidated by the Dq/B values, decay curves, and polyhedron distortion. The substitution of Sc3+ by Ga3+ in LSGB: Cr3+ (0 ≤ y ≤ 1.5) leads to decreasing structural polyhedron distortion and strengthened crystal field, consequently resulting in the blue-shift of broadband emission and enhanced thermal stability of LSGB: 0.07Cr3+ (y = 0.6) compared to that of LSB: 0.07Cr3+. The above results demonstrate that the superiority of blue-shift and enhanced thermal stability of LSGB: 0.07Cr3+ (y = 0.6) make it more suitable for the blue-pumped security-monitoring LEDs.
关键词： luminescence properties,crystal-field environment,security-monitoring LEDs,thermal stability,structural evolution,LaSc2.93-yGayB4O12(LSGB): 0.07Cr3+,Near-infrared (NIR) phosphors
更新于2025-09-23 15:19:57
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Morphology control and luminescence properties of red-emitting BaSiF6:Eu3+ hexagonal nanorod phosphors for WLEDs
摘要： To promote the development of solid-state lighting industry, exploring excellent inorganic phosphors has been always a scientific and applied hot issue. Herein, a series of efficient red BaSiF6:Eu3+ hexagonal nanorod phosphors with varied size and morphology were successfully prepared through a hydrothermal route. The reaction time, dosage of surfactant and solvent play an important role in the formation of the nanorod structures. The corresponding formation mechanism was discussed and revealed. The effects of surfactant, reaction time and solvent on photoluminescence properties of the as-prepared BaSiF6:Eu3+ nanorod phosphors were investigated in detail. Under excitation at 394 nm, all samples emit bright red light due to the typical Eu3+ 4f-4f transitions. Comparing the luminescence intensity of samples with different size of nanorods, it is found that the length of the nanorod is about 10–20 μm, the luminescence intensity of the sample is 3–5 times of the initial intensity of the nanorod sample that the length is around 30–40 μm. Moreover, when adding ethylene glycol as a solvent, the luminescence intensity of samples with different morphology increases with the increase of the reaction time. Importantly, as the temperature rising to 150 °C, the integrated intensity of the as-prepared sample still could obtain more than 95% of the intensity at room temperature, indicating the phosphors show excellent thermal stability. Thus, the as-prepared BaSiF6:Eu3+ nanorod phosphor is a potential red-emitting phosphor for white light-emitting diodes (WLEDs).
关键词： BaSiF6:Eu3+,luminescence properties,hydrothermal synthesis,thermal stability,WLEDs,hexagonal nanorod phosphors
更新于2025-09-23 15:19:57
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Synthesis and photoluminescence properties of a new blue-light-excitable red phosphor Ca2LaTaO6:Eu3+ for white LEDs
摘要： In this paper, a series of Eu3+-activated double-perovskite Ca2LaTaO6 (abbreviated as CLT:xEu3+; x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) red-emitting phosphors have been successfully synthesized via the conventional high-temperature solid-state reaction method. These samples were characterized by X-ray diffraction, Rietveld refinement, field-emission scanning electron microscope, elemental mapping, energy-dispersive spectrum, room-temperature photoluminescence, decay lifetimes, quantum efficiency, CIE color coordinates, and temperature-dependent emission spectra. Interestingly, under blue excitation into the 7F0→5D2 transition of Eu3+ at 466 nm, the CLT:xEu3+ phosphors could emit bright red light corresponding to the 5D0→7FJ (J = 1, 2, 3, 4) transitions. Their luminescence properties have been investigated as a function of the Eu3+ ions concentration. It was found that the CLT:0.4Eu3+ sample exhibited the strongest emission intensity, and the concentration quenching effect was caused by the dipole-dipole interaction among Eu3+ activators. Impressively, the emission intensity of the as-prepared CLT:0.4Eu3+ phosphors was about 4.3 times higher than the commercial Y2O3:Eu3+ red phosphors. Moreover, the CLT:0.4Eu3+ sample had excellent CIE color coordinates of (0.665, 0.334) and supereminent color purity of 95.3%. Notably, the study on temperature-dependent emission spectra of the CLT:0.4Eu3+ sample revealed its good thermal stability and color stability at high temperatures. These excellent photoluminescence properties of CLT:0.4Eu3+ phosphors indicated their promising application potential in white light-emitting diodes as blue-light-excitable red phosphors.
关键词： Ca2LaTaO6,White LEDs,Red-emitting phosphors,Eu3+ ions,Double-perovskite,Photoluminescence
更新于2025-09-23 15:19:57
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Realizing bright blue-red color-tunable emissions from Gd2GeO5:Bi3+,Eu3+ phosphors through energy transfer toward light-emitting diodes
摘要： Novel Bi3t, Eu3t co-doped Gd2GeO5 (GGO) phosphors were prepared by a high-temperature solid-state reaction method. X-ray diffraction, photoluminescence (PL), CIE chromaticity coordinates, internal quantum efficiency (IQE), and temperature-dependent PL spectra were applied to analyze the as-obtained phosphors. The emission spectra of the GGO:Bi3t, Eu3t phosphors showed both a broad blue band of Bi3t ions emission centered at 453 nm and the characteristic sharp red emission lines of Eu3t ions, corresponding to the 3P1→1S0 allowed transition of the Bi3t ions and the 5D0→7FJ (J ? 0, 1, 2, 3, 4) transitions of the Eu3t ions, respectively. Notably, the as-prepared GGO:Bi3t, Eu3t phosphors exhibited color-tunable emissions from blue (Bi3t) to red (Eu3t) with increasing the Eu3t doping concentration via a high-efficiency energy transfer process. Moreover, the mechanism of energy transfer from Bi3t to Eu3t ions was determined to be the dipole-quadrupole interaction. Impressively, the optimal GGO:0.05Bi3t, 0.12Eu3t phosphors had an outstanding IQE as great as 88% and good thermal stability. All these meaningful results demonstrated that blue-red color-tunable GGO:Bi3t, Eu3t phosphors have potential applications in white light-emitting diodes (LEDs) and plant growth LEDs.
关键词： Gd2GeO5,Energy transfer,Phosphors,Eu3t,Bi3t,Color-tunable emissions
更新于2025-09-23 15:19:57
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Duala??shelled RbLi(Li3SiO4)2:Eu2+@Al2O3@ODTMS phosphor as a stable green emitter for higha??power LED Backlights
摘要： The stability of luminescent materials is a key factor for the practical application in white light-emitting diodes (LEDs). Poor chemical stability of narrow-band green-emitting RbLi(Li3SiO4)2:Eu2+ (RLSO:Eu2+) phosphor hinders its further commercialization even if it possesses excellent stability against thermal quenching. Herein, we propose an efficient protection scheme by combining the surface coating of amorphous Al2O3 and hydrophobic modification by octadecyltrimethoxysilane (ODTMS) to construct the moisture-resistant dual-shelled RLSO:Eu2+@Al2O3@ODTMS composite. The growth mechanisms of both Al2O3 inorganic layer and silane organic layer on the phosphor surface are investigated, which can remarkably improve the water-stability of this narrow-band green emitter. The evaluation result of the white LED by employing this composite as green component demonstrates that RLSO:Eu2+@Al2O3@ODTMS is a promising candidate for the high-performance display backlights, and this dual-shelled strategy provides an alternative method to improve the moisture-resistant property of humidity-sensitive phosphors.
关键词： ALD,dual-shelled,hydrophobic,LED backlights,phosphors
更新于2025-09-23 15:19:57