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Results for “LED phosphors”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

The effect of Tb{sup +3} on α-Sr{sub 2}P{sub 2}O{sub 7} phosphor for green LED phosphor application

A series of Tb{sup +3} activated α-Sr{sub 2}P{sub 2}O{sub 7} (Strontium Pyrophosphate) phosphors were synthesized by high temperature combustion synthesis method. The structural analysis has been done by x-ray diffraction and FTIR (Fourier Transform Infrared Spectrum). The results obtained in structural characterization indicate that the doping concentration did not affect the crystal phase and structure of the phosphors. X-ray diffraction pattern reveals that the all samples were consistence with the JCPDS card No. 24-1011. The phosphor was excited at 232 nm wavelength, very intense PL green emission peak have been observed at 545 nm. This illustrates, that the phosphors could be efficiently excited because of the charge transfer band of the host as well as the energy transfer process occurred between host (Sr{sub 2}P{sub 2}O{sub 7}) and activator (Tb{sup +3}). By increasing the doping concentration of Tb{sup +3}, the intensity of 545 nm emission peak has been increased predominantly and it suggest that the phosphor prepared has very good application in green LED phosphor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Phosphors for LED lamps

A phosphor, a phosphor blend including the phosphor, a phosphor prepared by a process, and a lighting apparatus including the phosphor blend are disclosed. The phosphor has the formula (Ca.sub.1-p-qCe.sub.pK.sub.q).sub.xSc.sub.y(Si.sub.1-rGa.sub.r).sub.zO.su- b.12+.delta. or derived from a process followed using disclosed amounts of reactants. In the formula, (0<p.ltoreq.0.06); 0.ltoreq.q.ltoreq.0.06; 0.ltoreq.r.ltoreq.0.2; and -0.1.ltoreq..delta..ltoreq.0.4. In one embodiment, 3<x.ltoreq.3.1; 2.ltoreq.y.ltoreq.2.15; and 3.ltoreq.z.ltoreq.3.2. Similarly, in another embodiment, 3.ltoreq.x.ltoreq.3.1; 2<y.ltoreq.2.15; and 2.8.ltoreq.z.ltoreq.3.2.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Influence of processing parameters on long lasting hybrid phosphor for LED applications

Rare earth activated hybrid phosphors have made significant progress in terms of better light output, color properties and potential for long life. All these features coupled with low cost production and reduced maintenance have offered phosphor converted LEDs for diverse optoelectronic applications including signal lighting in advanced aviation. The present paper explores the effect of various processing parameters on luminescent hybrid phosphors fabricated through combustion synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Systems and methods for fluoride ceramic phosphors for LED lighting

The present disclosure relates to a lighting component which may comprise a light emitting diode (LED) or laser diode (LD) for generating at least one of blue light or ultraviolet light. A fluoride phosphor matrix may be included, which may be consolidated into a phosphor ceramic structure including at least one of a transparent fluoride ceramic structure or a translucent fluoride ceramic structure, and positioned adjacent to the LED or LD. The phosphor ceramic structure generates at least one of red or orange light when irradiated by the light emitted from the LED or LD. The phosphor ceramic structure exhibits reduced thermal quenching relative to a fluoride particulate structure irradiated by the LED or LD.

Cherepy, Nerine↗
DOE OSTI2016

A comparison of temperature and humidity effects on phosphor-converted LED packages and the prediction of remaining useful life with state estimation

This paper focuses on the failure mechanisms and color stability of a commercially available high power LED under harsh environmental conditions. 3 groups of the same pc-HB warm white LED were used in the experiment. The first group was subjected to both high temperature and high relative humidity (85°C/85%RH) with a 350mA bias current. The second group was subjected to only temperature stress at 105°C with a 350mA bias current. The last group was subjected to extreme high temperature 175°C and high bias current (500mA). Samples were taken out from the chamber for both photometric and colorimetric analysis at periodic intervals to investigate the change of the optical parameters. The physics of failure due to the material degradation has been correlated with the change in the photometric and colorimetric parameters of the LED packages. At the end of the experiment, 6000 hours of data is projected forward with state estimation methods to compare with projections made with the TM-21 method. Experimental results shows that only optical parts degrades at high temperature conditions. However, at both high temperature and high relative humidity condition, the phosphor layer of the pc-LED can swell and the color stability of LEDs degrades significantly. Also, comparison between TM-21 method and state estimation method shows that state estimation can achieve the same goal with a relatively easy method.

Lall, Pradeep↗
DOE OSTI2013

Color stable phosphors for LED lamps and methods for preparing them

An LED lamp includes a light source configured to emit radiation with a peak intensity at a wavelength between about 250 nm and about 550 nm; and a phosphor composition configured to be radiationally coupled to the light source. The phosphor composition includes particles of a phosphor of formula I, said particles having a coating composition disposed on surfaces thereof; ((Sr.sub.1-zM.sub.z).sub.1-(x+w)A.sub.wCe.sub.x).sub.3(Al.sub.1-ySi.sub.y-)O.sub.4+y+3(x-w)F.sub.1-y-3(x-w) I wherein the coating composition comprises a material selected from aluminum oxide, magnesium oxide, calcium oxide, barium oxide, strontium oxide, zinc oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, strontium hydroxide, zinc hydroxide, aluminum phosphate, magnesium phosphate, calcium phosphate, barium phosphate, strontium phosphate, and combinations thereof; and A is Li, NA, K, or Rb, or a combination thereof; M is Ca, Ba, Mg, Zn, or a combination thereof; and 0<x.ltoreq.1.10, 0.ltoreq.y.ltoreq.0.5, 0.ltoreq.z.ltoreq.0.5, 0.ltoreq.x.ltoreq.x.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

High Efficiency Colloidal Quantum Dot Phosphors

The project showed that non-Cd containing, InP-based nanocrystals (semiconductor materials with dimensions of ~6 nm) have high potential for enabling next-generation, nanocrystal-based, on chip phosphors for solid state lighting. Typical nanocrystals fall short of the requirements for on chip phosphors due to their loss of quantum efficiency under the operating conditions of LEDs, such as, high temperature (up to 150 °C) and high optical flux (up to 200 W/cm2). The InP-based nanocrystals invented during this project maintain high quantum efficiency (>80%) in polymer-based films under these operating conditions for emission wavelengths ranging from ~530 to 620 nm. These nanocrystals also show other desirable attributes, such as, lack of blinking (a common problem with nanocrystals which limits their performance) and no increase in the emission spectral width from room to 150 °C (emitters with narrower spectral widths enable higher efficiency LEDs). Prior to these nanocrystals, no nanocrystal system (regardless of nanocrystal type) showed this collection of properties; in fact, other nanocrystal systems are typically limited to showing only one desirable trait (such as high temperature stability) but being deficient in other properties (such as high flux stability). The project showed that one can reproducibly obtain these properties by generating a novel compositional structure inside of the nanomaterials; in addition, the project formulated an initial theoretical framework linking the compositional structure to the list of high performance optical properties. Over the course of the project, the synthetic methodology for producing the novel composition was evolved to enable the synthesis of these nanomaterials at a cost approximately equal to that required for forming typical conventional nanocrystals. Given the above results, the last major remaining step prior to scale up of the nanomaterials is to limit the oxidation of these materials during the tens of thousands of hours of LED operation. Once the LED phosphor lifetime specifications are met, these nanocrystals will enable white LEDs for solid state lighting to simultaneously have increased efficiency and improved light quality, in addition to enabling the creation of custom light spectrums. These improvements to white LEDs will help accelerate the adoption of SSL, leading to large savings in US and worldwide energy costs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Enhancement of photoluminescence properties and modification of crystal structures of Si{sub 3}N{sub 4} doping Li{sub 2}Sr{sub 0.995}SiO{sub 4}:0.005Eu{sup 2+} phosphors

Highlights: • Si{sub 3}N{sub 4} modified Li{sub 2}Sr{sub 0.995}SiO{sub 4}:0.005Eu{sup 2+} phosphors were prepared. • The luminescence intensity of Li{sub 2}Sr{sub 0.995}SiO{sub 4}:Eu{sup 2+} was enhanced by doping Si{sub 3}N{sub 4}. • The fluorescence decay times and thermal stability were enhanced by doping Si{sub 3}N{sub 4}. - Abstract: Si{sub 3}N{sub 4} modified Li{sub 2}Sr{sub 0.995}SiO{sub 4}:0.005Eu{sup 2+} (Li{sub 2}Sr{sub 0.995}SiO{sub 4−3x/2}N{sub x}:0.005Eu{sup 2+}) phosphors were synthesized with the conventional solid-state reaction in the reduced atmosphere. The crystal structure and vibrational modes were analyzed by X-ray diffraction, Raman scattering spectroscopy and Rietveld crystal structure refinement. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra showed that Li{sub 2}Sr{sub 0.995}SiO{sub 4−3x/2}N{sub x}:0.005Eu{sup 2+} powder exhibited a broad yellow emission band centered at 560 nm under the excitation of 460 nm visible light, due to the 4f{sup 6}5d{sup 1} → 4f{sup 7} transition of Eu{sup 2+}. The partial nitridation of Li{sub 2}Sr{sub 0.995}SiO{sub 4−3x/2}N{sub x}:0.005Eu{sup 2+} (x = 0.01) phosphors led to a large enhancement in the luminescence intensity, as much as 190%. At the same time, the fluorescence decay behavior curves further showed that the photoluminescence efficiencies of Li{sub 2}Sr{sub 0.995}SiO{sub 4−3x/2}N{sub x}:0.005Eu{sup 2+} phosphors were enhanced by addition of Si{sub 3}N{sub 4}. The temperature quenching characteristics confirmed that the oxynitride based Li{sub 2}Sr{sub 0.995}SiO{sub 4−3x/2}N{sub x}:0.005Eu{sup 2+} showed slightly higher stability. It is implied that Li{sub 2}Sr{sub 0.995}SiO{sub 4−3x/2}N{sub x}:0.005Eu{sup 2+} phosphors had a possible potential application on white LEDs to match blue light chips.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A flux-free method for synthesis of Ce{sup 3+}-doped YAG phosphor for white LEDs

Highlights: • A series of CeF{sub 3}-doped YAG phosphors were successfully synthesized. • CeF{sub 3} not only can be used as the Ce{sup 3+} source but also can play the role of a flux. • The QY of YAG:CeF{sub 3} phosphor is 91% but the QY of YAG:Ce{sub 2}O{sub 3} phosphor is just 80%. • YAG:CeF{sub 3} phosphor exhibits excellent thermal stability. • Using CeF{sub 3} as the Ce{sup 3+} source is a promising flux-free method to prepare YAG:Ce{sup 3+}. - Abstract: A series of CeF{sub 3}-doped Y{sub 3}Al{sub 5}O{sub 12} (YAG:CeF{sub 3}) phosphor, CeO{sub 2}-doped Y{sub 3}Al{sub 5}O{sub 12} (YAG:Ce{sub 2}O{sub 3}) phosphor and 5 wt% BaF{sub 2} added YAG:Ce{sub 2}O{sub 3} (YAG:Ce{sub 2}O{sub 3} + BaF{sub 2}) phosphor were successfully synthesized by a solid-state reaction method. The microstructure, morphology, luminescence spectra, luminescence quantum yield (QY) and thermal quenching of the phosphors were investigated. The QY of YAG:CeF{sub 3} phosphor is 91% but the QY of YAG:Ce{sub 2}O{sub 3} phosphor is just 80%. At 150 °C, the luminescence intensity of YAG:CeF{sub 3} phosphor, YAG:Ce{sub 2}O{sub 3} phosphor and YAG:Ce{sub 2}O{sub 3} + BaF{sub 2} phosphor was 85%, 86% and 89% of that measured at 25 °C, respectively. The comprehensive performance of the white LED lamp employing YAG:CeF{sub 3} phosphor is even better than that of the white LED lamp employing YAG:Ce{sub 2}O{sub 3} + BaF{sub 2} phosphor. The experimental results show that it is a promising flux-free method to synthesize Ce{sup 3+}-doped YAG phosphor by employing CeF{sub 3} as the Ce{sup 3+} source.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Li doping effect on the photoluminescence behaviors of KSrPO{sub 4}:Dy{sup 3+} phosphors for WLED light

Highlights: • The luminescence intensity of KSrPO{sub 4}:Dy{sup 3+} can be increased with Li{sup +} ions co-doping. • The mechanisms for the emitting enhancement with Li{sup +} ions co-doping were investigated. • The thermal stability demonstrated that KSrPO{sub 4}:0.01Dy{sup 3+}, 0.06Li{sup +} is suitable for WLEDs. • The chromaticity coordinates of KSrPO{sub 4}:Dy{sup 3+}, Li{sup +} can be tuned with Li{sup +} ions increasing. - Abstract: A novel warm-white phosphor KSrPO{sub 4} co-doped with Dy{sup 3+} and Li{sup +} ions was prepared by solid state reaction. A strategy of Li{sup +} doping was used with the aim of enhancing the luminescence of 475 nm and 570 nm emission bands under NUV excitation. Compared to lithium-free KSrPO{sub 4}:Dy{sup 3+}, the intensities of the 570 nm emission peaks were increased by 4.32 times and 2.84 times excited by 351 nm and 388 nm with 6 mol% Li{sup +} ions co-doping, respectively. The mechanism of the enhancement was discussed, that is due to the improvement of the phosphors’ crystallinity and charge compensation when the Li{sup +} ions were introduced. Furthermore, the thermal stability of KSrPO{sub 4}:0.01Dy{sup 3+}, 0.06Li{sup +} was measured and discussed, demonstrating it can be applied for high-powered LED. And the chromaticity coordinates of KSrPO{sub 4}:0.01Dy{sup 3+}, xLi{sup +} can be tuned efficiently from the cold-white region to warm-white region with Li{sup +} ions increasing, presenting its potential applied value as a new warm-white LED phosphor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

High Efficiency Integrated Package

Solid-state lighting based on LEDs has emerged as a superior alternative to inefficient conventional lighting, particularly incandescent. LED lighting can lead to 80 percent energy savings; can last 50,000 hours – 2-50 times longer than most bulbs; and contains no toxic lead or mercury. However, to enable mass adoption, particularly at the consumer level, the cost of LED luminaires must be reduced by an order of magnitude while achieving superior efficiency, light quality and lifetime. To become viable, energy-efficient replacement solutions must deliver system efficacies of ≥ 100 lumens per watt (LPW) with excellent color rendering (CRI > 85) at a cost that enables payback cycles of two years or less for commercial applications. This development will enable significant site energy savings as it targets commercial and retail lighting applications that are most sensitive to the lifetime operating costs with their extended operating hours per day. If costs are reduced substantially, dramatic energy savings can be realized by replacing incandescent lighting in the residential market as well. In light of these challenges, Cree proposed to develop a multi-chip integrated LED package with an output of > 1000 lumens of warm white light operating at an efficacy of at least 128 LPW with a CRI > 85. This product will serve as the light engine for replacement lamps and luminaires. At the end of the proposed program, this integrated package was to be used in a proof-of-concept lamp prototype to demonstrate the component’s viability in a common form factor. During this project Cree SBTC developed an efficient, compact warm-white LED package with an integrated remote color down-converter. Via a combination of intensive optical, electrical, and thermal optimization, a package design was obtained that met nearly all project goals. This package emitted 1295 lm under instant-on, room-temperature testing conditions, with an efficacy of 128.4 lm/W at a color temperature of ~2873K and 83 CRI. As such, the package’s performance exceeds DOE’s warm-white phosphor LED efficacy target for 2013. At the end of the program, we assembled an A19 sized demonstration bulb housing the integrated package which met Energy Star intensity variation requirements. With further development to reduce overall component cost, we anticipate that an integrated remote converter package such as developed during this program will find application in compact, high-efficacy LED-based lamps, particularly those requiring omnidirectional emission.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Stable Perovskite Core-Shell Nanocrystals as Down-Converting Phosphors for Solid State Lighting

Colloidal perovskite quantum dots (QDs) or nanocrystals (NCs) with structure of CsPbX 3 (X = Cl, Br, I) are promising materials as down-converting phosphors due to their high quantum yield up to >90%, extremely narrow emission band ~15-30 nm, and tunable emission wavelengths of ~410-700 nm via size or composition control. Compared to other QD materials, the optical and electronic properties of perovskite NCs are much more tolerant to defects so highly efficient light-emitting NCs can be easily prepared without carefully removing surface defects. Also, precision size control is not required for obtaining perovskite NCs with narrow emission <30 nm and can greatly enhance the reproducibility and yield rate during mass production. The challenges in using perovskite NCs as LED phosphors are their hygroscopic nature and self-absorption as observed from other QDs. We propose to synthesize core-shell structure perovskite NCs to improve their stability by over-coating a SiO 2 layer, followed by further sol-gel processing into stable micro-sized glass beads. To increase Stokes shift and avoid self-absorption, core/graded-shell/shell structure such as CsSnBr 3 /CsSn 1-x Pb x Br 3 /CsPbBr 3 NCs will be prepared, similar to a concept we demonstrated before in CdSe/Cd 1-x ZnxSe 1-y S y /ZnS structure with significantly separated absorption and emission bands. These NC materials will be integrated into films and used as remote or on-chip downconverters for high efficiency, high CRI and warm white LED. To achieve this goal, PhosphorTech Corporation (PTC) has teamed with Georgia Tech (GT) to develop this unique perovskite system for pcLEDs that offers the promise of high luminous efficacy over a broad temperature and optical flux range.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Thermostability and photostability of Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphors for white LED applications

Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphors were synthesized by solid-state reactions, and their photoluminescence (PL) stability under the impact of heat or light was studied. The thermal degradation in air was observed for the Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphor, furthermore, this drop in emission intensity could be accelerated by simultaneously illuminating the phosphor with a high-power blue LED during the heating process. This enhanced thermal degradation phenomenon in the blue light can be ascribed to the photo-assisted thermal oxidation of Eu{sup 2+} ions. A reversible decrease in emission intensity at room temperature was observed on illuminating the Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphor alone by the blue light, which could be related to trapping centers in the phosphor. The existence of traps is also responsible for the anomalous increase of emission intensity with increasing temperature from 30 to 100 °C. Considering the influences of Ba{sup 2+} doping on temperature-dependent PL properties of the Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphor, the thermal quenching origin may be ascribed to the thermally assisted photoionization process. - Graphical abstract: The photo-induced reversible decrease in emission intensity and the anomalous emission enhancement with increasing temperature are related to trapping centers in the phosphor. - Highlights: • The photo-assisted thermal degradation was observed for the Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphor. • The phosphor showed a reversible intensity decrease under the blue light irradiation. • An anomalous emission enhancement with increasing temperature was found. • Ba{sup 2+} substitution could suppress the thermal quenching of Sr{sub 3}SiO{sub 5}:Eu{sup 2+}. • Mechanisms for photostability and thermostability were discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Synthesis and photoluminescence study of Dy{sup 3+} doped Sr{sub 3}B{sub 2}O{sub 6}: Nanophosphors

In present paper, the combustion method synthesis of Dy{sup 3+} doped Sr{sub 3}B{sub 2}O{sub 6} nanophosphor and their luminescent properties have been reported. The crystalline structure and morphology of nanophosphors was confirmed and verify by the Xray powder diffraction (XRD) and transmission electron microscopy (TEM). The spectral properties of the Sr{sub 3}B{sub 2}O{sub 6}:Dy{sup 3+} nanophosphors have been studied with the photoluminescence (PL) spectroscopy. Under 300nm excitation, the PL emission shows three peaks at 482, 575 and 664 nm, corresponding to the {sup 4}F{sub 9/2}→{sup 6}H{sub 15/2}, {sup 4}F{sub 9/2}→{sup 6}H{sub 13/2} and {sup 4}F{sub 9/2}→{sup 4}H{sub 11/2} transition states. The 1931 CIE diagram gives the coordinates (x, y) as (0.38099, 0.40418) correspond to the shade of yellowish white emission of the Dy{sup 3+} ion which can be used as w-LED phosphors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Metal complexes and methods of making the same

Disclosed herein are embodiments of metal complexes and methods of making the same. The disclosed method embodiments provide a one-step approach to making metal complexes, such as complexes comprising lanthanide metals, rare earth metals, transition metals, main group metals, and/or actinide metals that can be used various applications, such as in separations technology, catalysis (e.g., catalysts for pharmaceutical synthesis and/or catalysts for biomass conversion), nuclear chemistry, LED phosphors, scintillator materials, magnetic materials, and nuclear fuels.

Kiplinger, Jaqueline↗
DOE OSTI2016

LED lamp incorporating remote phosphor with heat dissipation features

An LED lamp or bulb is disclosed that comprises a light source, a heat sink structure and a remote planar phosphor carrier having at least one conversion material. The phosphor carrier can be remote to the light sources and mounted to the heat sink so that heat from the phosphor carrier spreads into the heat sink. The phosphor carrier can comprise a thermally conductive transparent material and a phosphor layer, with an LED based light source mounted to the heat sink such that light from the light source passes through the phosphor carrier. At least some of the LED light is converted by the phosphor carrier, with some lamp embodiments emitting a white light combination of LED and phosphor light. The phosphor arranged according to the present invention can operate at lower temperature to thereby operate at greater phosphor conversion efficiency and with reduced heat related damage to the phosphor.

36 MATERIALS SCIENCE↗