Yellow-emitting Phosphor Research Articles

Spectrum regulation of LuAG:Ce phosphor ceramic with Gd doping for high-brightness and high-power yellow-emitting LEDs applications

To realize the high-brightness of yellow light-emitting diodes (LEDs), the yellow-emitting phosphor ceramics with high luminous efficiency (LE) are urgently explored. Based on the idea of spectrum regulation, the Lu3-x-yGdyAl5O12:xCe3+ (LuGdAG:Ce) phosphor ceramics were prepared via vacuum solid-state sintering. The effect of Gd3+ and Ce3+ content on the structure, luminescence and thermal properties of LuAG:Ce ceramics were investigated. The distortion ratio (D) of CeO8 and bandgap were effectively modified via Gd3+ doping, resulting in massive red-shifting of Ce3+ emission (513→561 nm). The LEDs lighting encapsulated by LuGdAG:Ce ceramics changes from green to yellow. Importantly, the yellow LEDs with a LE up to 139.0 lm/W@180 W and a warm correlated color temperature (CCT) of 3620 K were achieved based ceramic Ce07Gd9. The LuGdAG:Ce phosphor ceramic has the best of luminescence performance in phosphor-converted yellow LEDs lighting so far, which is considered to be the highly promising color converter.

Zero-thermal-quenching broadband yellow-emitting Bi3+-activated phosphors based on metal to metal charge transfer

Bi3+-activated phosphors have been proven to have potential applications foreground in white light-emitting diodes (WLED), plant growth lamps and temperature sensing. Therefore, it is urgent to exploit high-efficiency Bi3+-activated phosphors. Herein, a novel broadband yellow-emitting phosphor Ba2GdGaO5:Bi3+ with high internal quantum efficiency (IQE = 77%) was obtained based on metal to metal charge transfer (MMCT) between Bi3+ ground state and Gd3+ excited states. The photoluminescence excitation (PLE) spectrum and photoluminescence (PL) spectrum range from 225 nm to 400 nm and 400 nm to 700 nm, respectively, which can avoid the reabsorption phenomenon efficiently. Besides, Ba2GdGaO5:Bi3+ has superior thermal stability and it shows zero-thermal-quenching at 150 °C. The K+ doping hardly changes the thermal stability and can improve the PL intensity to 133.1% when the K+ concentration is 2%. Finally, a phosphor-convert WLED (pc-WLED) was simply synthesized by Ba2GdGaO5:Bi3+ and BaMgAl10O17:Eu2+ (BAM:Eu2+) phosphors. The doping of Eu3+ can significantly enhance the color rendering index (CRI, from 88.1 to 91.5) and reduce the correlated color temperature (CCT, from 4911 K to 4014 K). The above experimental results demonstrated that the phosphor has great application prospect in WLED.

CaO:Tb<sup>3+ </sup> green-emitting phosphor for white light-emitted diode-phosphor applications: the improvement of light output intensity

The use of CaO:Tb3+ with light green emission on for improvement of both luminescent output and chromatic fidelity of the white light emitted from a light-emitting diode (LED). The CaO:Tb3+ is combined with the yellow-emitting phosphor of YAG:Ce3+ to provide sufficient colored spectral proportion for the white light generation, enhancing the color performance. The phosphor combination is utilized for the three most applied LED structures: conformal, in-cup, and remote phosphor structures. The changes in optical properties of these three LEDs are monitored with adjustments in the proportion of CaO:Tb3+. The higher proportion of the green phosphor results in higher scattering efficiency in all structures, offering better color coordination and stronger luminous flux. The color quality scale is somehow reduced when CaO:Tb3+ concentration is more than a certain level. Therefore, depending on the phosphor configuration of the white light-emitting diode (WLED), the concentration of CaO:Tb3+ should be modified to achieve a good color rendition with improved color consistency and luminous properties.

A promising yellow-emitting langbeinite-type phosphor NaBaY2(PO4)3:Eu2+ for WLEDs.

The development of novel phosphors with excellent luminescence properties for white light-emitting diodes (WLEDs) is always a formidable task. Compared with the traditional laborious and aimless "trial and error" experiments, a mineral-inspired prototype strategy can provide an efficient and accurate method. Herein, for the first time, a novel yellow-emitting phosphor NaBaY2(PO4)3:Eu2+ was discovered using the mineral-inspired prototype strategy and cation substitution method. The phosphor was prepared via the high-temperature solid-state reaction method, and its crystal structure, luminescence properties and potential application for WLEDs were systematically investigated. The NaBaY2(PO4)3 phase was derived from the K2Mg2(SO4)3-type mineral structure and a photoluminescence study revealed that the phosphor can emit bright yellow light with a maximum at 545 nm upon excitation at 351 nm. A WLED lamp was fabricated by the use of a blend of commercial blue-emitting BaMgAl10O17:Eu2+, yellow-emitting NaBaY2(PO4)3:Eu2+ and red-emitting (Ca, Sr)AlSiN3:Eu2+ phosphors with a 380 nm LED chip. The CIE, CCT, Ra and efficiency of the as-fabricated LEDs were measured to be equal to (0.366, 0.365), 4327 K, 91.2 and 40.8 lm W-1, respectively. These results suggest that NaBaY2(PO4)3:Eu2+ could be a promising candidate for n-UV WLEDs.

High efficiency and stable La3Si6N11:Ce phosphor-in-glass film for high power laser lighting

As an inorganic color conversion material, phosphor-in-glass film (PiF) has received extensive attention in the sphere of laser-driven white lighting due to its excellent integrated performance. The yellow-emitting phosphor La3Si6N11:Ce has excellent thermal stability and wide emission band, which makes it more competitive than Y3Al5O12:Ce in laser-driven white lighting. Herein, we embedded La3Si6N11:Ce phosphor powder in a silicate glass matrix (SiO2–B2O3–CaO–Na2O) and sintered it on a sapphire substrate. In the silica-rich glass system, the network structure of silica-oxygen tetrahedral glass is more rigid and the thermal erosion of the phosphor by the silica-based glass is less, which makes the phosphor maintain better performance after low-temperature co-sintering. The quantum efficiency in the optimized LSN phosphor-in-glass film (LSN PiF) is up to 81 %, and the thermal conductivity is 10.2 Wm−1K−1, showing good thermal stability. Impressively, the LSN PiF produces a bright near-white light (0.3323,0.346) at a blue laser of 5.6 W, with corresponding luminous efficiency up to 195 lm/W. Moreover, LSN PiF can maintain about 80 % of the initial luminous intensity after continuous lighting for 24 h at the incident power of 3.5 W. These outstanding properties can advance the development of LSN phosphors in high power laser lighting applications.

Stable and Highly Luminescent Silver Nanoclusters in the 13X Zeolite Enabled by Mg2+ Doping and Their Luminescence Tuning by Heating Temperature.

Zeolite-confined silver nanoclusters (Ag-zeolite) have aroused vast interest due to their remarkable luminescence. The countercations within a zeolite play critical roles in determining the luminescent properties of the resulting Ag-zeolite. We observed, in this work, that introducing Mg2+ enabled the Ag-13X zeolite a stable and bright yellow emission with a high PLQY of 94.6%, the first report on the luminescence enhancement of the Ag-13X zeolite by Mg2+, to the best of our knowledge. The formation of specific internal electric fields inside 13X and the structural contraction of the zeolite framework due to the high charge density and the small ionic radius of Mg2+ are believed to be responsible for the enhanced stable and bright yellow emission. The stabilization effect of Mg2+ is removed by increasing the heating temperature above 700 °C, which leads to the variation of silver nanoclusters as a result of the framework collapse of the zeolite. The Ag-zeolite synthesized by us, featured with a broad emission band, a high PLQY of 94.6%, and good thermal stability, can be considered a suitable candidate to replace the traditional commercial yellow-emitting phosphor YAG:Ce3+ for light-based applications. This work contributes to a valuable reference for the rational design of silver nanoclusters confined in zeolites with promising new functionalities and stimulates potential applications as novel phosphors for near-ultraviolet light-emitting diodes (NUV-LEDs).

Efficient broadband yellow-emitting Mg2.5Lu1.5Al1.5Si2.5O12:Ce3+ garnet phosphors for blue-light-pumped white light-emitting diodes

The discovery of yellow-emitting phosphors with higher luminescence intensity and wider bandwidth than the commercial Y3Al5O12:Ce3+ (YAG:Ce3+) phosphor upon blue light excitation remains one of the significant challenges for establishing human-centered warm white light-emitting diode towards high-performance illumination. Herein, we innovatively synthesized a novel Ce3+-activated broadband yellow-emitting garnet phosphor of Mg2.5Lu1.5Al1.5Si2.5O12:Ce3+ (MLASO:Ce3+) via conventional high-temperature solid-state reaction method. The as-prepared MLASO:10%Ce3+ garnet sample possesses a cubic structure with Ia3‾d space group and lattice parameters of a = b = c = 11.85098 Å and V = 1664.421(0.044) Å3. Luminescence spectroscopy tests indicates that the optimal MLASO:10%Ce3+ yellow-emitting phosphor features 1.2 times higher relative integral luminescence intensity and an impressive full width at half maximum (FWHM) of up to 145 nm with respect to the most extensively available commercial YAG:Ce3+ phosphor (FWHM = 122 nm) under the identical blue light irradiation, which can provide more red-components for improving color rendering index. Additionally, the CIE color coordinates and a satisfactory internal quantum efficiency are determined to be (0.4751,0.5028) and 74%, respectively. More importantly, the representative optimal sample can preserve 77% luminescence emission intensity at a 423 K high temperature thermal treatment environment compared to the ambient temperature. As a result, this study sheds light on newly discovered broadband yellow-emitting MLASO:10%Ce3+ garnet phosphor containing more of the red chromatic spectrum can sever as one of the promising color-conversion-materials in high-performance white LEDs with high color rendering index for healthy solid-state lighting.

Anti-counterfeiting and multifunctional applications of near white emitting La1.99MgTiO6:0.01Dy perovskite nano phosphors

A 1 wt% dysprosium doped double perovskite nano phosphor La2MgTiO6 is synthesised by a low-temperature combustion method. When excited with UV radiation (351 nm), the sample shows major characteristic emission peaks at 480 nm (4F9/2 →6H15/2) and 574 nm (4F9/2 →6H13/2) whereas, when excited by IR radiation (980 nm), an up-conversion emission peak at 654 nm (4F9/2 →6H11/2) is observed. The photoluminescence spectra of La1.99Dy0.01MgTiO6 show dominant blue emission, which obliges potential white LED applications with chroma coordinates (0.32, 0.33). On the other side, the samples annealed above 1223 K build suitable reading light that shows dominant yellow emission with a quantum efficiency of 69.25 %; which simplifies why samples with high-temperature heat treatment are pertinent yellow-emitting phosphor. Using the Tauc plot, an improvement of ΔEg= 14 meV is seen owing to annealing at 1223 K. The XRD, Raman, SEM, and TEM results signify the increase in crystallinity and crystallite size with annealing. Noticeably, the red emission upon up-conversion highlights the medical imaging purpose. The effective combination of up-down conversion emission can be successfully exploited for anti-counterfeiting applications; underlining the multifunctional application of a single perovskite nano phosphor for smart materials.

Double-perovskite structure-driven thermal-stabilized Dy3+-activated yellow-emitting phosphors

A series of novel dysprosium(III) (Dy3+)-doped yellow-emitting double-perovskite A2BB’O6 (A = calcium(II) (Ca2+), B = lanthanum(III) (La3+), gadolinium(III) (Gd3+), and indium(III) (In3+); B′ = antimony(V) (Sb5+), tantalum(V) (Ta5+), and niobium(V) (Nb5+)) phosphors were synthesized. The ion substitution in B and B′ sites in the double-perovskite structure significantly affected its crystal structures and photoluminescence properties such as excitation spectrum, emission spectrum, thermal stability, color purity, luminescence dynamic, and quantum yield. Interestingly, the beneficial thermal stability of all the obtained samples (> 62% at 423 K with respect to the initial value at 303 K) implied their potential for solid-state lighting application. Among them, the Ca2LaTaO6:Dy3+ exhibited the best heat resistance (> 83% at 423 K) while the Ca2GdNbO6:Dy3+ had the highest internal quantum yield up to 35.17%. Furthermore, the possible mechanisms for the changes in luminescent properties relying on their chemical compositions were studied accordingly. Eventually, some fabricated light-emitting diode devices based on the obtained samples were tested for their application in warm solid-state lighting.

Efficient blue-light-excitable copper(I) coordination network phosphors for high-performance white LEDs

The blue-light-excitable phosphors play a crucial role in the high-performance white LEDs. Here, we report on two new Cu(I) coordination network materials as yellow-emitting phosphors prepared by suitably expanded π-conjugated triazole ligands. Upon blue-light irradiation, these complexes exhibit efficient solid-state emission and enhanced photostability. Through incorporating the yellow phosphor and a commercial blue-green powder (BaSi2N2O2:Eu2+) with a blue LED chip, the phosphor-converted LED devices display remarkable white emission properties. The experimental results demonstrate that the Cu(I) coordination network materials function as promising blue-light excitable phosphors with great application potential for full-spectrum white LEDs.

Highly efficient and self-activating Zn3V2O8 phosphor for the fabrication of cool-white light emitting devices

Achieving an ideal white light with eco-friendly phosphor material with a high quantum efficiency (QE) together with an appreciable correlated color temperature (CCT) and color rendering index (CRI) is considered as a global challenge. To address the issue, we have fabricated a self-activated Zn3V2O8 phosphor-based white light emitting device (WLED) as single emitting compound with desired CCT and color purity values of ∼5074 K and 10.47 × 10−2 respectively, using a moderately low temperature assisted solid-state reaction process carefully ruled out the presence of rare-earth ions. The prepared Zn3V2O8 phosphor exhibited a highly visible yellow (575 nm) photoluminescence (PL) induced by the 3T2 (t152e) →1A1 and 3T1(t152e) →1A1 (t16) transitions of vanadate [VO4]3-, which unveil a significant QE of 67%. The temperature-dependent PL spectra showed a high thermal stability and CIE color coordinates (0.45, 0.47), falling in the exact yellow region. The combination of Zn3V2O8 phosphor and deep blue (405 nm, 40 mW) emission from LED resulted in white light emission with CIE color coordinates and CRI of (0.33, 0.36) and 93, respectively. This work shows that the newly exposed broadband yellow-emitting Zn3V2O8 phosphors as a potential candidate for phosphor-converted WLEDs with high color quality via a non-rare-earth activation approach.

Dy3+-doped NaSrLaTeO6: a novel yellow-emitting double perovskite phosphors with high thermal stability for WLEDs

Dy3+-doped NaSrLaTeO6: a novel yellow-emitting double perovskite phosphors with high thermal stability for WLEDs

High color rendering and high-luminance laser lighting using all inorganic nitride phosphor films.

Despite the huge advances that have been made in the development of ultra-high luminance laser lighting, achieving high color rendering properties in such systems at the same time remains a challenge. Recent studies show that in most cases, the luminous efficacy (LE) of laser lighting is compromised to improve the color rendering index (CRI). In this study, a possible solution to this problem has been proposed by preparing phosphor-in-glass (PiG) films comprised of the yellow-emitting phosphor (LSN:Ce3+) and the red-emitting phosphor (CASN:Eu2+). The composite material synthesized in this study exhibited outstanding optical and thermal properties. A uniform white light with a high CRI of 80.0 and a high LE of 185.9 lm W-1 was achieved by optimizing the yellow/red ratio and the emission peak position of the blue laser. Furthermore, it was found that this design enabled the phosphor to restrict the light emission area effectively, thus attaining a high luminous exitance of 1302 lm mm-2. With their superior optical performance, the PiG films can be regarded as promising color converter candidates for future high-quality laser-based white light sources.

CsPbI3/N-GQDs dual layer phosphor-converted white-LEDs with ultrahigh luminous efficiency and color rendering index

Phosphor-converted LEDs or pc-LEDs, as a solid-state lighting source, are attractive for next-generation display technologies because of their energy savings, and green environmentally friendly nature. Recently, white LEDs are being produced commercially by coating blue LED (440–470 nm) chips with various yellow-emitting phosphors. However, the LEDs produced by this technique often exhibit high correlated color temperature (CCT) and low color rendering index (CRI) values, due to sufficient red spectral components not being present, and thus aren’t suitable for commercial grade white illumination. To circumvent this drawback, our work reports for the first time the use of blue and green-emitting nitrogen-functionalized graphene quantum dots (GQDs) coupled with red-emitting CsPbI3 NCs for phosphor-based LED applications. We deployed near-UV to visible excitable red-emitting perovskite CsPbI3 nanocrystals which contribute toward the red spectral component, thus greatly improving the CRI of the LEDs. CsPbI3 nanocrystals are optically excited by nitrogen-functionalized GQD with blue and green emissions in a remote double-layer phosphor stack technique. This double phosphor layer stacking greatly improves both the CRI and luminous efficiency of radiation (LER), which usually has a trade-off in previously reported phosphor stacks. A CCT of ∼5182 K providing daylight white tonality, with superior CRI (∼90%) and ultrahigh LER (∼250 lumens/watt) are reported, which are significantly higher than the established benchmarks.

New Dy3+-activated KCa2Nb3O10 yellow-emitting phosphors for w-LEDs application: Preparation and optical properties

A novel single-phase KCa 2 Nb 3 O 10 :Dy 3+ yellow-emitting phosphor can be efficiently excited under 388 nm irradiation. • KCa 2 Nb 3 O 10 :Dy 3+ phosphors have been firstly synthesized using the molten-salt method. • The KCa 2 Nb 3 O 10 :Dy 3+ product shows excellent thermal stability with high temperature quenching temperature. • The KCa 2 Nb 3 O 10 :Dy 3+ product shows rich UV excitation band and yellow light emission. • The CIE color coordinates of prepared KCa 2 Nb 3 O 10 :Dy 3+ phosphors change slightly. A series of Dy 3+ doped KCa 2 Nb 3 O 10 niobate phosphors that generated yellow emission was prepared using the molten-salt method. The crystal structure, X-ray diffraction (XRD), optimal concentration, photoluminescence excitation/emission (PLE/PL), and luminescent stability of the prepared phosphors were exhaustively studied. The KCa 2 Nb 3 O 10 lattice has a perovskite-like structure, which possesses the Cmcm (No.63) space group. The KCa 2 Nb 3 O 10 :Dy 3+ phosphors can be efficiently excited by n -ultraviolet ( n -UV) excitation of 388 nm. Besides, KCa 2 Nb 3 O 10 :Dy 3+ phosphors can emit three dominant peaks centered at 486, 577, and 662 nm, which are ascribed to the 6 H J /2 ( J = 15/2, 13/2, and 11/2) transitions, respectively. The optimum doping concentrations of Dy 3+ ions in the KCa 2 Nb 3 O 10 host are determined to be 0.02 mol. The thermal-quenching temperature ( T 0.5 ) for the KCa 2 Nb 3 O 10 :0.20Dy 3+ sample is estimated to be above 500 K, and the calculated activation energy ( E a ) is 0.29 eV. Furthermore, the Commission International de I'Eclairage (CIE) color coordinates of prepared KCa 2 Nb 3 O 10 :Dy 3+ phosphors change slightly. KCa 2 Nb 3 O 10 :Dy 3+ phosphors possess good color purity, color stability, and low correlated color temperature (CCT). All results indicate that the KCa 2 Nb 3 O 10 :Dy 3+ phosphors are suitable for white light-emitting diodes (w-LEDs) applications.

Synthesis and characterization of thermostable Dy3+-doped La5NbMo2O16 yellow-emitting phosphors for w-LEDs

Synthesis and characterization of thermostable Dy3+-doped La5NbMo2O16 yellow-emitting phosphors for w-LEDs

Synthesis and luminescence properties of Dy3+-doped Mg2InSbO6 yellow-emitting phosphors with abnormal thermal quenching performance for w-LEDs

Synthesis and luminescence properties of Dy3+-doped Mg2InSbO6 yellow-emitting phosphors with abnormal thermal quenching performance for w-LEDs

Room Temperature Synthesis of Various Color Emission Rare-Earth Doped Strontium Tungstate Phosphors Applicable to Fingerprint Identification

Crystalline SrWO4 was synthesized at room temperature using a co-precipitation method. To use the SrWO4 as a phosphor, green and red phosphors were synthesized by doping with Tb3+ and Eu3+ rare earth ions. The synthesized samples had a tetragonal structure, and the main peak (112) phase was clearly observed. When the sample was excited using the absorption peak observed in the ultraviolet region, SrWO4:Tb3+ showed an emission spectrum of 544 nm, and SrWO4:Eu3+ showed an emission spectrum of 614 nm. When Tb3+ and Eu3+ ions were co-doped to realize various colors, a yellow-emitting phosphor was realized as the doping concentration of Eu3+ ions increased. When the synthesized phosphor was scattered on a glass substrate with fingerprints, as used in the field of fingerprint recognition, the fingerprint was revealed by green, red, and yellow emissions in response to a UV lamp.

Synthesis and characterization of a new double perovskite phosphor: NaCaTiTaO6:Dy3+ with high thermal stability for w-LEDs application

A new yellow-emitting phosphor, NaCaTiTaO6:Dy3+, was synthesized via solid-phase synthesis at 1300 ℃. X-ray diffraction (XRD) analysis and Rietveld refinement showed that the prepared phosphors exhibited a stable double perovskite structure. The particle size of the phosphor was around 3.8 μm. The maximum emission peak at 574 nm is attributed to the 4F9/2→6H13/2 energy level transition under irradiation at 389 nm. The optimum Dy3+ doping concentration is 0.10 M equivalent, and concentration quenching is due to the nearest neighbor ion interaction. The luminescence intensity of the phosphor was reduced by only 15% at 420 K, exhibiting high thermal stability. Quantum yield (QY) was measured to be 26.31%. Finally, the Commission International de I’Eclairage (CIE) color coordinate of the phosphor for white light emitting diode (w-LED) was (0.314, 0.323), with a color rendering index (Ra) of 92 and a correlated color temperature (CCT) of 5578 K. Above all, the Dy3+-doped double perovskite NaCaTiTaO6:Dy3+ phosphor is expected to be used in w-LEDs.

Sol-gel auto-combustion synthesis and luminescence properties of GdCaAl3O7: RE3+ (RE=Eu, Tb, Eu@Tb) phosphors for near-ultraviolet light-triggered indoor illumination

The color-tunable GdCaAl3O7: RE3+ (RE = Eu, Tb, Eu@Tb) phosphors were synthesized via an ultrafast sol-gel auto-combustion synthesis method. The X-ray diffraction patterns confirmed the forming of GdCaAl3O7 tetragonal phase, and the scanning electron microscopy images indicated that the obtained products presented honeycomb-like structure due to the gas releasing during the auto-combustion process. The luminescent properties, concentration quenching mechanism, energy transfer mechanism, luminescent dynamics, thermal stability and product practicability of GdCaAl3O7: RE3+ (RE = Tb, Eu, Eu@Tb) phosphors were investigated systematically. All the GdCaAl3O7: RE3+ products presented the characteristic emission of doped RE3+. Using GdCaAl3O7: 50% Tb3+@3.0% Eu3+ as yellow-emitting phosphors in combination with commercial BAM: Eu2+ blue-emitting phosphors and a NUV chip can successfully package a warm white LED device with high color rendering index (CRI, 86.3) and low correlated color temperature (CCT, 3348 K) that was very suitable for near-ultraviolet light-triggered indoor illumination.