Phosphors For Lighting Research Articles

Improved ternary composite ceramic phosphors for warm-white laser lighting

Improved ternary composite ceramic phosphors for warm-white laser lighting

Absolutely Structural Disorder Boosting Bandwidth toward Full-Spectrum White Light from Single Occupancy of Activator.

Achieving single-phase full-spectrum white light (SFWL) phosphors is a central goal in theoptical field because they simplify white-LEDs assembly and avoid long-term color instability. Despite many approaches are developed, current SFWL phosphors still suffer from chromaticity drift due to inconsistent thermal quenching of multiple emitting centers. Herein, an absolutely structural disorder strategy is established to develop a single-emitting center-based SFWL phosphor. Precisely controlling the flux added induces a structural translation from the absolutely ordered Y0.75Ta0.25O1.75:Bi3+ to the absolutely disordered Y0.785Ta0.215O1.715:Bi3+, as directly identified by STEM-HAADF analyses. Structural disorder enables Y0.785Ta0.215O1.715:Bi3+ to produce SFWL with the FWHM of 6194cm-1 (175nm) by employing a single activator site, a 1352cm-1 increase compared to the cyan-emitting Y0.75Ta0.25O1.75:Bi3+ despite Bi3+ occupies two lattice positions. This single-emitting center-based SFWL, coupled with minimal thermal expansion of the unit cell and inapparent spectral overlap of excitation and emission bands, ensure zero-chromaticity shift with elevated temperature. A prototype white-LEDs using Y0.785Ta0.215O1.715:Bi3+ as a single luminescent layer generates warm white light without perceptible CIE coordinates shift under various currents or after extremely long-term continuous operation. This work highlights the potential of structural disorder in designing SFWL phosphors with exceptional color stability.

High thermally stable and efficient rare-earth celsian by phase transformation of Ba2+-Exchanged SOD zeolite

The white LEDs with high performance and excellent luminous quality is of high importance for developing the current lighting industry, and high thermally stable blue phosphors play a critical role in the preparation of white LEDs. Herein, we reported a facile way to obtain highly efficient blue Eu2+-doped celsian phosphor with excellent thermal stability by a phase transformation of Ba2+-exchanged SOD Zeolite strategy. The structure of phosphors changed from nepheline to celsian with the doping of Ba2+, and the maximum emission intensity blue-shifts from 550 nm to 450 nm under the excitation of 370 nm. The PLQY is determined to be 56 %, 96 % and 82 % for the phosphor with Ba2+ doping concentration being 0, 1.49 and 1.86, respectively, and the luminescence intensity at 423 K is can be 80 %, 102 % and 93 % of its intensity at room temperature. Finally, the package of the LED device based on our yellow and blue phosphors together with the commercial red CaAlSiN3:Eu2+ phosphor is constructed to show warm white light with the CCT of 3705 K and a high CRI of 97.7. This study provides a facile way for obtaining satisfactory phosphors for high-quality lighting.

Effect of Dopant Concentration on Luminescence Properties of Na3Ca2(SO4)3F: RE (RE = Eu3+, Dy3+) Phosphor for Solid-State Lighting.

A fluoride material phosphor doped with rare earth ions Eu3+ and Dy3+ was studied for its photoluminescence (PL) properties. The material was synthesized using a combustion method and characterized using X-ray diffraction (XRD) and PL techniques. The Na3Ca2(SO4)3F: Eu3+ phosphor exhibits two distinct peaks at 593 nm (orange) and 615 nm (red) at an excitation wavelength of 395 nm. The PL excitation spectrum of the Na3Ca2(SO4)3F: Dy3+ phosphor showed series of peaks, corresponding to the 4f → 4f transitions of Dy3+ ions. Under 350-nm excitation, the PL emission spectrum revealed two prominent bands one at 483 nm (blue region) due to the 4F₉/₂ → 6H₁₅/₂ transition, and another at 573 nm (yellow region) resulting from the 4F₉/₂ → 6H₁₃/₂ transition. These blue and yellow emissions suggest potential applications in solid-state lighting, particularly for mercury-free excitation sources. Rare earth-doped Eu3+/Dy3+ materials exhibit highly efficient PL properties, making them suitable candidates for white light-emitting diodes (LEDs) or other solid-state lighting phosphors.

Optical properties of Eu3+/Dy3+ doped BaY2(MoO4)4 white light phosphor

Optical properties of Eu3+/Dy3+ doped BaY2(MoO4)4 white light phosphor

Suppressed concentration quenching and tunable photoluminescence in Eu2+-activated Rb3Y(PO4)2 phosphors for full-spectrum lighting

Highly efficient inorganic phosphors are desirable for lighting-emitting diode light sources, and increasing the doping concentration of activators is a common approach for enhancing the photoluminescence quantum yield (PLQY). However, the constraint of concentration quenching poses a great challenge for improving the PLQY. Herein, we propose a fundamental design principle by separating activators and prolonging their distance in Eu2+-activated Rb3Y(PO4)2 phosphors to inhibit concentration quenching, in which different quenching rates are controlled by the Eu distribution at various crystallographic sites. The blue-violet-emitting Rb3Y(PO4)2:xEu (x = 0.1%–15%) phosphors, with the occupation of Rb1, Rb2 and Y sites by Eu2+, exhibit rapid luminescence quenching with optimum external PLQY of 10% due to multi-channel energy migration. Interestingly, as the Eu concentration increases above 20%, Eu2+ prefer to occupy the Rb1 and Y sites with separated polyhedra and large interionic distances, resulting in green emission with suppressed concentration quenching, achieving an improved external PLQY of 41%. Our study provides a unique design perspective for elevating the efficiency of Eu2+-activated phosphors toward high-performance inorganic luminescent materials for full-spectrum lighting.

Designing a high-efficiency broadband cyan phosphor for low-blue full-spectrum LED lighting

Efficient cyan-emitting phosphor plays an important role in the development of solid-state lighting, which is indispensable to filling the cyan gap for full-spectrum warm-white light-emitting diodes (WLEDs) with high color rendering index (CRI). Herein, a novel highly efficient broadband cyan phosphor Ce3+-doped Ca3HfAl2Si2O12 (CHASO: Ce3+) garnet compound was developed by the substitution of Lu3+-Al3+ with Ca2+-Hf4+/Si4+ in Lu3Al5O12. The crystal structure and photoluminescence (PL) properties of CHASO: Ce3+ were investigated in detail. Notably, CHASO: Ce3+ phosphor can be effectively excited by violet light (390 – 430 nm) and exhibited bright cyan emissions around 490 nm with high PL internal quantum yields of 89.2 %. Moreover, the integrated PL intensity of the phosphor at 423 K was 66.3 % of that at room temperature. Finally, by incorporating CHASO: 11 %Ce3+ with commercial blue/yellow/red phosphor onto a violet LED chip (400 nm), the prototype full-spectrum WLEDs device exhibits warm white light with high color rendering index (CRI, Ra and R9 > 90) and low correlated color temperature 3301 K. These results suggest the highly efficient phosphor CHASO: Ce3+ is promising for low-blue full-spectrum healthy lighting.

Photoluminescence properties of Eu3+ doped La(OH)3 phosphors: Fuel dependent combustion synthesis

In this study, we synthesized La(OH)3:Eu3+ phosphor using the combustion method with diverse fuels—urea, glycine, and dextrose. Through XRD patterns and Rietveld refinement, we confirmed a hexagonal crystal structure with a P63/m space group for all samples. Our analysis also delved into morphological properties and elemental composition, revealing intriguing differences in particle shapes despite similar sizes, depending on the fuel utilized. Interestingly, the PL excitation and emission characteristics remained consistent among the samples, displaying distinct bands. Spectroscopic investigation of Eu3+ activated La(OH)3 exhibits the strong red emission which indicated effective energy transfer among rare earth and host. Notably, when excited at 284/290 nm and 395 nm, the phosphor emitted multicolour bands spanning blue to red regions. However, some challenges and shortcomings were observed related to lanthanum hydroxide such as thermal stability, because at higher temperatures samples decompose easily which can limit their high-temperature applications. Additionally, some more issues are with this material i.e. complexity in synthesis, insolubility in water and ageing and exposure to atmospheric CO2 which can change its composition. Despite these challenges, our research focuses on optimizing and improving all these parameters. Addressing these shortcomings of lanthanum hydroxide can be beneficial for the advancement of applications. This impressive emission spectrum underscores the potential of this synthesized phosphor for lighting and display devices. The consistent photoluminescence features across different fuel variations suggest robustness and versatility, indicating promising avenues for future exploration in lighting technology research.

Structural, morphological, optical and down-conversion studies of NaLaMgTeO6:Dy3+ single phase phosphor for white light emitting applications and solar spectral converter for photovoltaic applications

Researches on rare earth activated phosphors in solid state lighting and enhancement in efficiency of solar cells pave attention to develop efficient phosphor materials. In the present work, Dy3+ doped NaLaMgTeO6 phosphors are synthesized using solid state reaction method. The structural studies using XRD analysis confirmed the successful formation of the compound. SEM analysis reveals that the particles are closely packed, which in turn exhibit intense luminescence intensity due to low scattering and high packing density. Elemental configuration were analyzed using EDS analysis. FTIR analysis revealed the vibrational bands of the host matrix. Optical energy bandgap was calculated using DRS spectra. The luminescence characteristics of the samples were investigated using excitation and emission spectra. Upon most intense 351 and 388 nm excitation, sharp yellow emission peak at 572 nm dominates blue emission at 478 nm, further reveals that Dy3+ ions occupy low symmetry site in the host lattice. The optimum concentration of Dy3+ in the present host is x = 0.04 mol and concentration quenching is due to dipole-quadrupole interaction of adjacent Dy3+ ions. The thermal quenching phenomenon is studied using temperature dependent photoluminescence analysis. The CIE chromaticity coordinates and CCT values conclude NaLaMgTeO6:Dy3+ phosphors are good candidate for cool near-white light emitting materials for outdoor illumination. The study on solar spectral response and down-conversion property of the synthesized phosphor demonstrate its applicability as solar spectral converters in solar cell applications.

Cool white light emitting Dy3+ activated KNaCa2(PO4)2 phosphor for outdoor lighting and optical thermometric applications

Dy3+ incorporated KNaCa2(PO4)2 phosphor (KNCP) with doping concentrations ranging from 0.005 to 0.7 mol were synthesised via high-temperature solid state reaction route. The morphological characteristics were examined using FESEM images and found agglomerated structure in micrometers with an average particle size of 4.037 µm. Photoluminescence emission spectra under 350 nm excitation reveal nearly equal intense blue and yellow emission bands owing to 4F9/2→6H15/2 and 4F9/2→6H13/2 Dy3+ transitions, respectively. The concentration-dependent emission properties were examined and the optimum concentration was found to be 0.03 mol. The synthesized phosphor exhibits a quantum yield of 69.06 % at the optimal Dy³⁺ doping concentration. The time-correlated emission characteristics were analysed from the TRES plot. Furthermore, the emission bands at 479 nm (4F9/2→6H15/2) and 572 nm (4F9/2→6H13/2) under 350 nm excitation follow bi-exponential decay having an average lifetime in the range of 0.90–0.37 ms. The prepared phosphors exhibit an intense cool white light regardless of doping concentration and delay time. Optical thermometric properties of KNCP Dy phosphor were investigated by fluorescence intensity ratio (FIR) technique and exhibit relative thermal sensitivity of 2.57 and 0.7 %K−1 in the temperature range of 90 −230 K and 250–500 K respectively. The excellent quantum yield, sub-millisecond lifetime, cool colour temperature, and higher temperature sensitivities make them ideal for outdoor lighting and optical thermometric applications.

Highly thermostable and color tunable Dy3+/Sm3+ co-doped germanate phosphors for solid-state lighting

Currently, developing thermostable and color tunable phosphor via energy transfer strategy is a significant research topic in solid-state lighting field. Herein, the sensitizer Dy3+ and activator Sm3+ are solidly dissolved into the Ba2Y2Ge4O13 (BYGO) matrix to prepare color-tunable germanate phosphors BYGO:Dy3+,Sm3+. Under 365 nm excitation, the energy transfer-induced tunable emission of Dy3+/Sm3+ co-doped phosphors are investigated. The energy transfer mechanism is ascribed to the quadrupole-quadrupole interaction. The thermal quenching investigation manifests that the BYGO:Dy3+,Sm3+ phosphor has excellent thermostability (the emission intensity at 423 K reduces only 6.9 %) and resistance to chromaticity shifting (the chromaticity shifting parameter at 473 K is as low as 3.94 × 10−3). Meanwhile, the ∼365 nm InGaN chip-excited w-LED device is fabricated with commercial phosphor BaSi2O2N2:Eu2+ and the title material, showing satisfactory electroluminescence performance. This work reveals that the title phosphor is a suitable candidate for solid-state lighting.

Unusual Tm3+ sensitization-induced white-emitting and thermostable improvement in Ba2Y2Ge4O13:Dy3+ phosphor for solid-state lighting and optical thermometry

Currently, the development of single-phase white emitters is an interesting research topic. Researchers have paid much attention to tune white-emitting of Dy3+-activated phosphors via Tm3+ sensitization strategy. However, the role of Tm3+ sensitization on luminescence thermostability was usually underestimated. Herein, color-tunable germanate phosphors Ba2Y2Ge4O13 (BYGO):Tm3+,Dy3+ were prepared. The white light emission is achieved due to the effective energy transfer from Tm3+ to Dy3+. A BYGO:Tm3+,Dy3+-based w-LED exhibits warm white-emitting. Moreover, the back-energy transfer of Dy3+→Tm3+ contributes to the improvement of luminescence thermal stability. Meanwhile, the difference of temperature-dependent Tm3+ and Dy3+ emissions realizes satisfactory temperature sensing properties. This work provides a deep understanding for the role of Tm3+ sensitization strategy on color tuning and thermostable improvement, promoting multifunctional utilizations of Dy3+-activated phosphors.

Bi3+ activated Li6Y(BO3)3 phosphors for full-spectrum lighting

The blue-violet emitting phosphors is a critical aspect of achieving a high-quality full-spectrum white light-emitting diodes (WLEDs). Here, the photoluminescence characteristics of blue-violet emitting phosphors Li6Y(BO3)3:Bi3+ and its application performances were systematically studied. The emission of the phosphors exhibits a high dependence on the excitation wavelength. Upon excitation at 372 nm, the phosphors emit blue light peaking at 407 nm. The excitation of 340 nm results in the occurrence of two peaks at 407 and 506 nm in emission spectra. A full-spectrum WLED prepared by coating a 365 nm n-UV LED and the mixture comprising the phosphors and three commercial phosphors. The WLED exhibits high color rendering index (Ra = 95) and low correlated color temperature (3555 K). Consequently, Li6Y(BO3)3:Bi3+ is a potential phosphor that can be used for full spectrum WLEDs.

Exploring inorganic phosphors: basics, types, fabrications and their luminescence properties for LED/WLED/displays

Abstract The utilization of phosphors in lighting and display applications has garnered significant attention due to their unique luminescent properties and versatile crystal structures. This review article comprehensively examines recent advances in the synthesis, characterization, and applications of nitride and sulfide phosphors. This article addresses various phosphor crystal structures, including perovskite, garnet, nitride sulfide, fabrications strategies, and their impact on the optical and electronic properties. Furthermore, the review highlights the role of doping and activator ions in tailoring the emission characteristics of nitride and sulfide phosphors, enabling precise control over color rendering and efficiency. Additionally, the article also discusses emerging trends in phosphor technology, such as the development of novel synthesis methods and the integration of phosphors into next-generation lighting and display devices. The basic properties of phosphor materials like CRI, CIE chromaticity coordinates, quantum efficiencies are well discussed. Overall, this article provides valuable insights into the current state of research and future directions in the field of phosphors offering potential avenues for further advancements in lighting and display technologies.

Robust and orange-yellow-emitting Sr-rich polytypoid α-SiAlON (Sr3Si24Al6N40:Eu2+) phosphor for white LEDs

ABSTRACT Nitrides and oxynitrides isostructural to α-Si3N4 (M-α-SiAlON, M = Sr, Ca, Li) possess superb thermally stable photoluminescence (PL) properties, making them reliable phosphors for high-power solid-state lighting. However, the synthesis of phase-pure Sr-α-SiAlON still remains a great challenge and has only been reported for Sr below 1.35 at.% as the large size of Sr2+ ions tends to destabilize the α-SiAlON structure. Here, we succeeded to synthesize the single-phase powders of a unique ‘Sr-rich’ polytypoid α-SiAlON (Sr3Si24Al6N40:Eu2+) phosphor with three distinctive Sr/Eu luminescence sites using a solid-state remixing-reannealing process. The Sr content of this polytypoid structure exceeds those of a few previously reported structures by over 200%. The phase purity, composition, structure, and PL properties of this phosphor were investigated. A single phase can be obtained by firing the stoichiometric mixtures of all-nitride precursors at 2050°C under a 0.92 MPa N2 atmosphere. The Sr3Si24Al6N40:Eu2+ shows an intense orange-yellow emission, with the emission maximum of 590 nm and internal/external quantum efficiency of 66%/52% under 400 nm excitation. It also has a quite small thermal quenching, maintaining 93% emission intensity at 150°C. In comparison to Ca-α-SiAlON:Eu2+, this Sr counterpart shows superior quantum efficiency and thermal stability, enabling it to be an interesting orange-yellow down-conversion luminescent material for white LEDs. The experimental confirmation of the existence of such ‘Sr-rich’ SiAlON systems, in a single-phase powder form, paves the way for the design and synthesis of novel ‘Sr-rich’ SiAlON-based phosphor powders with unparalleled properties.

Low-temperature synthesis and luminescence properties of blue-emitting β-SiAlON:Eu2+ phosphor using melamine as a self-propagating raw material

Sialons are widely recognized for their rigid lattice structure, high visible light transmittance, and excellent thermal stability, making them suitable matrix materials for activators. In this paper, we successfully prepared β-sialon phosphors, β-Si6-zAlzOzN8-z:Eu2+ (β-SiAlON:Eu2+), using an organic precursor method at a low synthesis temperature for the first time. X-ray diffraction analysis and Rietveld refinement confirm the β-SiAlON:Eu2+ phosphor possesses a hexagonal structure with a P63 space group. Under 320 nm excitation, β-SiAlON:Eu2+ phosphor exhibits a blue emission band centered at 415 nm due to the 5d → 4 f electron transition of Eu2+, which differs significantly from other β-SiAlON:Eu2+ phosphors with green emission. It is interesting that excessive Eu2+ activators make β-SiAlON:Eu2+ phosphor possess a green emission band centered at 510 nm. Therefore, the light-emitting color of β-SiAlON:Eu2+ phosphor shifts from the blue to the green with the increase of Eu2+ concentration. Furthermore, the activation energy of β-SiAlON:0.02Eu2+ sample is calculated to be about 0.2527 eV, which confirms β-SiAlON:Eu2+ phosphor has good thermal stability. The article presents a low-temperature and cost-effective synthesis method for preparing sialons, as well as a novel blue β-SiAlON phosphor for solid-state lighting.

An efficient violet-excited and cyan-green/near-infrared dual emitting phosphor for full-spectrum lighting

Achieving full-spectrum lighting is highly desired but still challenging for high quality phosphor-converted white light-emitting diodes (pc-wLEDs), which is stunted by efficient cyan and near-infrared (NIR) components. At present, the development of cyan phosphors has attracted most of the attention, and NIR light is often ignored in full-spectrum lighting. In particular, there are a few reports of simultaneous emission of cyan and NIR light in a single matrix. Herein, an efficient broadband cyan-green/NIR dual emitting phosphor Ca2LuAl3Si2O12: Ce3+, Cr3+ (CLASO: Ce3+, Cr3+) with cubic garnet structure was developed by Ca2+-Si4+ double substitution of Lu3+-Al3+ in Lu3Al5O12, in which CLASO: Ce3+ phosphor can be efficiently excited by violet light (λem = 395–430 nm) and show a broad cyan-green emission band centered about 500 nm, with high photoluminescence quantum yields (PLQYs = 95 %) and good thermal stability (89.7 %@423 K). Cr3+ ions co-doping plays a role of two birds with one stone: convert the harmful blue light into NIR light, promote the absorption efficiency of violet light, and cut down the variety of phosphors for full-spectrum pc-LED devices in wLED devices. By combining the as-prepared CLASO: Ce3+, Cr3+ phosphor and commercial yellow/red phosphors on a violet LED chip, the prototypical wLED can emit full-spectrum warm white light (Ra = 93) and a low correlated color temperature of 3121K, which demonstrate CLASO: Ce3+, Cr3+ phosphor can speed up the industrialization of healthy lighting.

Structural and photoluminescence properties of SrNb2O6: RE3+ (RE = Sm, Tb) phosphors for solid state lighting

The phosphors for pc-LEDs have high thermal stability requirements due to the high operating temperature of LEDs. In addition, there are many phosphors based on SrNb2O6, but no one has studied Sm3+ or Tb3+ as the luminescent center of SrNb2O6 host. Therefore, two new phosphors based on SrNb2O6 host are proposed in this work. One is an orange phosphor with negative thermal quenching phenomenon using Sm3+ as the luminescent center, and the other is a green phosphor with Tb3+ as the luminescent center. In this work, a series of SrNb2O6:Sm3+ and SrNb2O6:Tb3+ phosphors were prepared by the solid-state reaction method. The structure, morphology, chemical composition, absorption properties and luminescence properties of Sm3+ and Tb3+ doped SrNb2O6 samples were studied. Under 405 nm excitation, the SrNb2O6:Sm3+ samples exhibit the 4f-4f transition of Sm3+ with the strongest emission intensity at 607 nm, the emission intensity of SrNb2O6:0.03Sm3+ phosphor at 150 °C remains at 100.56% of its room temperature value and the chromaticity coordinates are located in the orange region, with a color purity of 88.19%. Under 307 nm excitation, the SrNb2O6:Tb3+ samples exhibit the 4f-4f transition of Tb3+ with the strongest emission intensity at 544 nm, the emission intensity of SrNb2O6:0.09Tb3+ phosphor at 150 °C remains at 7.68% of its room temperature value and the chromaticity coordinates are located in the green region with a color purity of 74.29%. Additionally, Na+ is introduced as a charge compensator in the Sm3+ or Tb3+ doped phosphors, which enhances their luminescence intensity. These results indicate that the two phosphors synthesized in this work have the prospect of application in the field of solid-state lighting.

Performance improvement of reflective phosphor film via adjusting the thickness realizing bright and efficient laser lighting.

Phosphor-in-glass-film (PiG-F) has been extensively investigated, showing great potential for use in laser lighting technique. Thickness is apparently a key parameter for PiG-F, affecting the heat dissipation, absorption, and reabsorption, thus determining the luminous efficacy and luminescence saturation threshold (LST). Conventional studies suggest that thinner films often have lower thermal load than that of the thicker ones. Unexpectedly, we found that the Lu3Al5O12:Ce (LuAG:Ce)-based PiG-F with a moderate thickness (78 μm) yielded the optimal LST of 31.9 W (14.2 W·mm-2, rather than 28.0 W (12.3 W·mm-2) for the thinnest one (56 μm). This unexpected result was further verified by thermal simulations. With the high saturation threshold together with a high luminous efficacy (∼296 lm·W-1), an ultrahigh luminous flux of 7178 lm with a luminous exitance of 2930 lm·mm-2 was thus attained. We believe the new, to the best of our knowledge, findings in this study will substantially impact the design principles of phosphors for laser lighting.

Synthesis, structural and optical properties of a novel double perovskite Gd[formula omitted]MgTiO[formula omitted]: Dy[formula omitted] phosphors for LED applications

Dy3+ doped Gd2MgTiO6 (GMT) phosphors were were fabricated using the high temperature solid state method in this study. Fluorescence, UV-visible spectrometer, X-ray photoelectron spectrometer, and Transient fluorescence spectrometer. The results show that the structures of the series of phosphors belong to the monoclinic crystal system, and Dy3+ was successfully incorporated into the GMT host without affecting its structure. The samples emitted extremely strong blue and yellow light, which are the transitions derived from 4H9/2 to 6H15/2 (482 nm) and 6H13/2 (575 nm) levels, respectively. The sample shows obvious effects of concentration, GMT: 0.11Dy3+ phosphor has the best photoluminescence (PL) intensity 7.148×105, lifetime is 0.16 ms, and an internal quantum efficiency (IQE) is 2.1%. The Dy3+ doped sample has a larger energy band gap of 4.11 eV. The prepared samples exhibit color coordinates in proximity to that of standard white light, which indicates that the phosphor GMT: Dy3+ can be applied to white light phosphors and light-emitting diode (LED) devices.