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Enhanced emission from thermally stable Eu3+ doped CaB2Si2O8 red phosphors via alkali metal modification for W-LEDs application
摘要： M+/Eu3+ (M = Li, Na, K) co-doped CaB2Si2O8 phosphors have been synthesized by a solid-state reaction approach. XRD measurements confirm that the phase purity of the CaB2Si2O8 host is maintained after the introduction of alkali metal ions and Eu3+ ions. The emission intensity of Eu3+ ions is enhanced by a factor of 1.75 and 1.55 with the incorporation of Li+ and Na+ ions, respectively, originating from the charge compensation and improved asymmetry in the crystal field, while the addition of K+ ions to the composition results in a decreased luminescence intensity due to the structural-defect-related quenching. Temperature dependent measurement reveals that the prepared phosphor exhibits excellent thermal stability with 81% at 423 K of the integrated emission intensity at 298 K. A white light-emitting diode (W-LED) device is fabricated based on the synthesized Eu3+ doped CaB2Si2O8 red phosphor modified by Li ions. All these results indicate that the synthesized phosphor is a promising red-emitting material for W-LEDs application.
关键词： Red phosphor,Eu3+ ions,W-LEDs,Alkali metal ions
更新于2025-09-16 10:30:52
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Optical Properties of Red-Emitting Rb2Bi(PO4)(MoO4):Eu3+ Powders and Ceramics with High Quantum Efficiency for White LEDs
摘要： There are several key requirements that a very good LED phosphor should meet, i.e., strong absorption, high quantum e?ciency, high colour purity, and high luminescence quenching temperature. The reported Rb2Bi(PO4)(MoO4):Eu3+ phosphors have all these properties. The Rb2Bi(PO4)(MoO4):Eu3+ phosphors emit bright red light if excited with near-UV radiation. The calculated colour coordinates show good stability in the 77–500 K temperature range. Moreover, sample doped with 50% Eu3+ possesses quantum e?ciency close to unity. Besides the powder samples, ceramic disks of Rb2Eu(PO4)(MoO4) specimen were also prepared, and the red light sources from these disks in combination with near-UV emitting LED were fabricated. The obtained results indicated that ceramic disks e?ciently absorb the emission of 375 and 400 nm LED and could be applied as a red component in phosphor-converted white LEDs.
关键词： thermal quenching,luminescent ceramics,red phosphor,colour coordinates,quantum e?ciency,luminous e?cacy
更新于2025-09-16 10:30:52
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White Light-Emitting Diodes With Ultrahigh Color Rendering Index by Red/Green Phosphor Layer Configuration Structure
摘要： Currently, white light-emitting diodes (WLEDs) have been widely applied in lighting, display, and medical fields. However, there still exists the problem of low color rendering index (CRI, Ra). In this work, phosphor-converted WLEDs (pc-WLEDs) with ultrahigh Ra were fabricated using Y3Al3Ga2O12:Ce3+ green phosphor and CaAlSiN3:Eu2+ red phosphor configuration structure. The broad emission spectrum of the green phosphor compensates for the gap of the cyan-emitting region that realizes full-spectrum white-light emission. The weight ratio of green/red phosphors was controlled to optimize the optical performances of pc-WLEDs. At the ratio of 0.15/0.012, the fabricated pc-WLED exhibits a natural white light with an ultrahigh Ra of 95.2 and an incredibly small International Commission on Illumination (CIE) chromaticity coordinates deviation (Duv = ?0.0034) at 350 mA. The corresponding correlated color temperature (CCT) and luminous efficiency (LE) are 4526 K and 62.34 lm/W, respectively. Furthermore, two separated phosphor configuration structures were constructed for pc-WLEDs. The R up/G down structure achieves the highest LE of 64.93 lm/W, and the corresponding CCT and Ra are 5714 K and 95.8, respectively, chiefly due to the compensation for reabsorption effect caused by the large difference in the luminous efficacy of radiation (LER) between dichromatic phosphors. The results demonstrate that by adjusting the phosphor configuration structure, the pc-WLEDs with high color rendering can be obtained, which have great applications in high-quality lighting.
关键词： white light-emitting diodes (WLEDs),High color rendering,separated phosphor layer,phosphor configuration
更新于2025-09-12 10:27:22
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Closing the Cyan-Gap toward Full Spectrum LED Lighting with NaMgBO3:Ce3+
摘要： The photoluminescence spectrum generated by an ordinary phosphor-converted white light-emitting diode (pc-wLED) that combines a blue LED chip with a yellow phosphor or a near-UV LED with red, green and blue phosphors contains a notable cavity in the cyan region of the visible spectrum (480-520 nm) that reduces the color quality produced by these lights. Here, we report a new bright blue-cyan-emitting phosphor, NaMgBO3:Ce3+, that bridges the gap. Rietveld refinements verify the rare-earth substitution while ab initio calculations prove Ce3+ occupies the Na+ sites. NaMgBO3:Ce3+ is excited by a broad range of near-UV light sources and produces a blue-cyan emission with a high (internal) quantum efficiency, minimal thermal degradation, and zero-chromaticity drift at elevated temperatures. Fabricating a near-UV (λex = 370 nm) pumped pc-wLED using NaMgBO3:Ce3+ along with commercially available phosphors demonstrates a well-distributed warm white light with a high color-rendering index (Ra) of 91 and a low correlated color temperature (CCT) of 3645 K. Closing the cyan cavity with NaMgBO3:Ce3+ is ideal for generating a pleasant, full-spectrum, warm white light.
关键词： full-spectrum LED lighting,NaMgBO3:Ce3+,blue-cyan-emitting phosphor,color-rendering index,phosphor-converted white light-emitting diode
更新于2025-09-12 10:27:22
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White-light/tunable emissions in single-phased BaLa2Si3O10:Eu3+, Bi3+ phosphor for the simultaneous applications in white light-emitting diodes and luminous cement
摘要： In this work, we report the single-phased BaLa2Si3O10:Eu3+, Bi3+ phosphor with white-light/tunable emissions under UV excitations. We find the emissions of Bi3+-doped BaLa2Si3O10 samples are dependent on the excitation spectral wavelength, where exciting by the wavelength from 240 to 410 nm range can lead to the tunable Bi3+ emissions owing to the intensity change of three emission bands (i.e., 367 nm, 423 nm, and 516 nm). After co-doping the Eu3+ ions into Bi3+-doped BaLa2Si3O10, the energy transfer from Bi3+ to Eu3+ ions dominated by a dipole–quadrupole (d–q) interaction mechanism is proved. Typically, by exciting with 365 nm and varying the Eu3+ content, the tunable emissions from blue, white to red are observable in the BaLa2Si3O10:Eu3+, Bi3+. By coating the white BaLa2Si3O10:Eu3+, Bi3+ sample with a commercial 365-nm UV LED chip or mixing it with the cement, we not only achieve the white-light LEDs device with the desirable color rendering index (CRI) of 95, excellent luminescent efficiency of 80 lm/W, and good excellent color temperature (CT) of 4215 K at the CIE chromaticity of (0.338, 0.357), but also achieve the luminous cement.
关键词： white light-emitting diodes,single-phased phosphor,white-light/tunable emissions,luminous cement,BaLa2Si3O10:Eu3+,Bi3+
更新于2025-09-12 10:27:22
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A New Co-Substitution Strategy as a Model to Study a Rare-Earth-Free Spinel-Type Phosphor with Red Emissions and Its Application in Light-Emitting Diodes
摘要： The substitution of metal sites in Mg2TiO4 substrate leads to charge imbalance that will be closely related to a variety of changes including lattice structure, cell distortion, and photophysical properties. Herein, the co-substitution strategy of [Ga3+?Ga3+] for [Mg2+?Ti4+] and Sn4+ for Ti4+ achieves for the first time the novel Mg3Ga2SnO8 (MGS):xMn4+ (x = 0?3%) phosphors with efficient red emissions. In terms of X-ray powder diffraction (XRD) and Rietveld refinement analysis, MGS:Mn4+ possesses a structure isotypic of Mg2TiO4 in the cubic space group Fd3?m (227). There are two types of octahedra for Mn4+ ions in this structure, where Ga3+ ions completely occupy a group of octahedral sites and Mg2+/Sn4+ has been randomly distributed over another group of octahedral sites. A strong excitation band in the broad spectral range (220?550 nm) has been identified, thus facilitating the commercial uses for blue LED chips excitation. An intense red emission band at 680 nm has been observed due to the characteristic 2Eg?4A2g transition of Mn4+ ions. A concentration quenching effect occurs when the Mn4+ content exceeds 1.5%, and the quenching mechanism is demonstrated to be dipole?quadrupole interactions. Temperature-dependent luminescence measurements support its good thermal stability, and the corresponding activation energy Ea is determined to be 0.2552 eV. The possible luminous mechanism of the Mn4+ ion is explained by the Tanabe?Sugano energy level diagram. The crystal field strength and the Racah parameters together with the nephelauxetic ratio are also determined for Mn4+ in the MGS lattice. High color rendition warm white-light-emitting diodes (WLEDs) based on the optimal phosphor MGS:1.5%Mn4+,1.5%Li+ possess a color rendering index and color temperature of 85.6 and 3658 K, respectively. Its feasibility for application in solid-state white lighting has been verified.
关键词： Co-substitution strategy,Light-emitting diodes,Red emissions,Spinel-type phosphor,Rare-earth-free
更新于2025-09-12 10:27:22
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Green and red phosphor for LED backlight in wide color gamut LCD
摘要： Wide color gamut (WCG) backlight for liquid crystal display (LCD) utilizing white light-emitting diodes (LED) has attracted considerable attention for their high efficiency and color reduction. In this review, recent developments in crystal structure, luminescence and applications of phosphors for wide color gamut LED backlight are introduced. As novel red phosphors, Mn4+ activate fluoride and aluminate phosphors are advanced in quantum efficiency, thermal quenching and color saturation for their characteristic spectrum with broad excitation band and linear emission. The crystal structure and fluorescence properties of Mn4+ doped fluosilicate, fluorogermanate, fluotitanate, as well as Sr4Al14O25, CaAl12O19 and BaMgAl10O17 phosphors are discussed in detail. A serial of narrow-band red-emitting Eu2+, Eu3+ and Pr3+-doped nitride silicates and molybdate phosphors are also introduced. Rare-earth-doped oxynitride and silicate green-emitting phosphors have attracted more and more attention because of the wide excitation, narrow emission, high quenching temperature, high quantum efficiency, such as β-sialon:Eu2+, Ba3Si6O12N2:Eu2+, MSi2O2N2:Eu2+ (M=Ca, Sr, Ba), γ-AlON: Mn2+ and Ca3Sc2Si3O12:Ce3+. All above phosphors demonstrate their adaptability in wide color gamut LCD display. Especially for Mn4+ doped fluosilicate red phosphor and β-sialon: Eu2+ green phosphor. To achieve an ultra-high color gamut in white LED backlight and against the OLED, innovative narrow-band emission red and green phosphor materials with independent intellectual property rights are continuously pursed.
关键词： Rare earths,Liquid crystal display,Backlight,Wide color gamut,White LED,Phosphor
更新于2025-09-12 10:27:22
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Polyol derived Bi3+ and Er3+ co-doped lanthanum oxide nanophosphors for display & LED applications
摘要： Color tunable luminescence was observed from Bi3+ and Er3+ co-doped La2O3 nanophosphor. The nanophosphors were prepared using cost effective and low temperature polyol route. The crystal structure, morphology, photoluminescence (PL) and were investigated in detail. Hue of Color changed which is observed by PL emissions on heating, La2O3:Bi3+, Er3+ phosphor powders from 700 to 900 (cid:1)C. The observed emission peaks in PL from phosphor powder materials were assigned to either the broad emission originating from the transition in Bi3+ or the visible emission peaks originating transition from the Er3+ ions. All emission peaks of PL are plotted using CIE coordinates.
关键词： Luminescence,Phosphor,CIE,Bismuth co-doped,Binary oxide,Tunable
更新于2025-09-12 10:27:22
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Eu3+-doped NaYGeO4: A novel red-emitting phosphors for ultraviolet or blue chips excited white LEDs
摘要： A novel red-emitting phosphor NaYGeO4: Eu3+ has been prepared by a high temperature solid state method. All the Eu3+ ions are completely dissolved in the NaYGeO4 host without changing its crystal structure. Under 315 nm host excitation or 464 nm 7F0→5D2 excitation, the phosphor NaYGeO4: Eu3+ presents red emission with the strongest peak at 613 nm. The concentration quenching and luminescence mechanism are also investigated. The optimal NaYGeO4: 0.05Eu3+ phosphor displays high internal quantum efficiency, excellent thermal stability with the activation energy (?E) of 0.2716 eV. The color emission can be tuned by changing the Eu3+ concentration. The phosphor presents a great potential application for ultraviolet or blue excited white LED.
关键词： Optical materials and properties,Thermal stability,Luminescence,Red phosphor
更新于2025-09-12 10:27:22
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A laser current control algorithm to avoid color distortion in laser projection displays
摘要： Laser display technology has gradually become an important solution for large screen display. As a mature lighting technology in recent decades, phosphor has been widely used in the field of lighting and display. As a solid-state light source, it has the advantages of low power consumption, environmental protection, rich color, and dynamic modulation. The luminescent efficiency of phosphors varies with temperature, which results in the nonlinearity of phosphor emission when the light source is dynamically modulated and the color temperature drift of the display image. In this paper, a control model of color temperature of laser TV display changing with laser current and temperature is established. The color temperature of laser TV is corrected by using current compensation control algorithm. The problem of color temperature drift caused by the change of phosphor conversion efficiency with temperature is solved. The color temperature deviation is 1118 K in the luminance range of the light source before compensation. By compensating and controlling the laser current, the ratio of blue light and phosphor is constant when the luminance changes, thus ensuring the color temperature constant when the luminance of the laser light source changes. The color temperature deviation is 50 K in the luminance range. By analyzing the different luminance of the display image, the stability of the color temperature is improved.
关键词： laser phosphor,color distortion,dynamic compensation
更新于2025-09-12 10:27:22