Yellow-emitting Phosphor Research Articles

Embedding red-emitting dyes in robust hydrogen-bonded organic framework for application in warm white light-emitting diodes

Broadband yellow-emitting phosphors are very attractive for warm white light-emitting diodes (WLEDs) used in solid-state lighting, backlight display, and related fields. In this work, we describe a room temperature, solution processable yellow-emitting phosphors for warm WLEDs using the chemically stable nanoscale hydrogen-bonded organic framework (HOF) PFC-1 as the host. By embedding the red-emitting dyes of rhodamine B (RhB), rhodamine 6G (Rh6G), 4-( p -dimethylaminostyryl)-1-methylpyridinium (DSM), and 4-(dicyanomethylene)-2-methyl-6-( p -dimethylaminostyryl)-4H-pyran (DCM) in the green-emitting nano PFC-1, respectively, four types of single-matrix yellow-emitting nanocomposites were obtained. Due to the spectral combination of host PFC-1 and guest dyes, the obtained nanocomposites show broader emission spectra than that of the commercial yellow phosphor. Specifically, RhB@PFC-1 has a promising quantum yield of 17.8%. By coating the nanophosphors on the commercial blue LED chips (450 nm), bright sources of warm-white light were realized. It was found that the RhB@PFC-1 coated LED has an excellent color rendering index (CRI) of 85.6 and a correlated color temperature (CCT) of 4669 K at a drive current of 300 mA, while Rh6G@PFC-1 coated LED shows warm white light with a low CCT of 3100 K and a promising CRI of 75.4 K. This Dye@HOF strategy opens an avenue to developing yellow-emitting phosphors for the use in high color rendering warm WLEDs. • A series of yellow-emitting Dye@PFC-1 nanophosphors were reported. • The Dye@PFC-1 nanocomposites show a broader emission band than that of YAG:Ce 3+ . • Bright sources of warm white light were achieved by coating the nanocomposites on blue LED chips. • The WLED coated with RhB@PFC-1 exhibits a CRI of 85.6 and a CCT of 4669 K at a 300 mA driven current.

Improving the luminescence property of the novel yellow-emitting phosphor SrLa2Sc2O7:Bi3+ with charge compensators (Li+, Na+, K+) and its application in NUV-based white LEDs.

In this work, a novel yellow-emitting phosphor SrLa2Sc2O7(SLSO):Bi3+ was synthesized by a high temperature solid-state method, with a wide coverage from 400 nm to 800 nm under near-ultraviolet (NUV) excitation and the full width at half maximum (FWHM) of up to 180 nm. The phosphor emits bright yellow light, which is observed using optical microscopy. Alkali metal (Li+, Na+, K+) ions were used as charge compensators to enhance the luminescence intensities of SrLa2Sc2O7:Bi3+. Finally, the yellow SrLa2Sc2O7:Bi3+,Li+ and blue Sr5(PO4)3Cl:Eu2+ phosphors were homogeneously mixed with silica gel and coated on a NUV light emitting diode (LED) at 370 nm to obtain white LEDs with a high color rendering index (Ra = 91.3), a low correlated color temperature (CCT = 4879 K) and color coordinates (0.34, 0.30). This work can provide a good candidate for making white LEDs.

Achieving a blue-excitable yellow-emitting Ca-LMOF phosphor via water induced phase transformation.

Luminescent metal–organic frameworks (LMOFs) with diverse structural features and promising fluorescence-based applications have attracted wide attention in the past two decades. In this work, a LMOF with the formula [Ca4(tcbpe-F)2(H2O)3] (1, LMOF-411) has been constructed from calcium (Ca) and 1,1,2,2-tetrakis(4-(4-carboxyphenyl)phenyl)ethene (H4tcbpe-F). Compound 1 features a three-dimensional framework with a 10-nodal net topology. Due to the relatively high hydration energy of Ca2+, compound 1 readily transforms into a new phase formulated as [Ca(H2tcbpe-F)(H2O)2] (1′) upon exposure to water. Combining experimental characterization and theoretical calculations, we elucidated the mechanism of H2O-induced phase transition from 1 to 1′. Notably, the water induced phase transformation can be detected visibly from the change in luminescence, which originates from the fluorescent linker. Compound 1 emits green light (λem = 490 nm) under UV excitation, while compound 1′ emits bright yellow light (λem = 550 nm) under blue excitation (450 nm). Compound 1′ represents the first Ca based LMOF yellow phosphor and its luminescence quantum yield reaches 68%. It can be coated directly onto a commercial blue light-emitting-diode (LED) chip to fabricate a white LED (WLED).

Structure and luminescent properties of Dy3+ activated NaLa9(SiO4)6O2 yellow-emitting phosphors for application in white LEDs

A series of Dy3+-doped sodium lanthanum orthosilicate oxyapatites, NaLa9−xDyx(SiO4)6O2 (NLSO:xDy, x = 0–0.3), were synthesized by the solid-state reaction method at 1100 °C, with the aim of developing yellow emitting phosphors for applications in w-LEDs. Their crystal structure, morphology and particle size distribution, electronic structure, Raman spectra, concentration- and temperature-dependent luminescent properties were investigated for the first time. The crystal structure was refined by the Rietveld method. Undoped NLSO is hexagonal (space group P63/m – C26h) with lattice constants a = b = 9.6917(3) Å and c = 7.1836(4) Å. It is shown that Dy3+ ions substitute for the La3+ ones in two types of sites with C3 and Cs point symmetries. The first-principle calculations for undoped NLSO revealed an indirect bandgap of 5.06 eV. The NLSO:0.2Dy phosphor exhibited intense yellow emission with CIE 1931 chromaticity coordinates of (0.469, 0.495) and a correlated color temperature of 3150 K owing to the hypersensitive electric-dipole transition 4F9/2→6H13/2 (571 nm) dominating in the luminescence spectrum. Excellent thermal stability was found for this apatite phosphor (the activation energy is 0.23 ± 0.02 eV).

Synthesis and optical properties of novel apatite-type NaCa3Bi(PO4)3F:Dy3+ yellow-emitting fluorophosphate phosphors for white LEDs

In this study, novel yellow-emitting fluorophosphate NaCa3Bi(PO4)3F phosphors doped with different concentrations of Dy3+ ions were first obtained via high-temperature solid-state reaction. The crystal structure, phase purity, particle morphology, photoluminescence (PL) properties, thermal stability, and luminescence decay curves of the resulting phosphors were then characterized in detail. Under the excitation of 349 nm, the three dominant peaks of the NaCa3Bi(PO4)3F:Dy3+ are centered at 480 nm (4F9/2-6H15/2), 577 nm (4F9/2-6H13/2), and 662 nm (4F9/2-6H11/2). The optimal doping concentration of Dy3+ ions in the NaCa3Bi(PO4)3F:xDy3+ phosphors is x = 5 mol%. The phosphors show excellent thermal stability with high activation energy (Ea = 0.32 eV). Eventually, the synthesized white light-emitting diode (w-LED) demonstrates the Commission International de L'Eclairage (CIE) chromaticity coordinates of (0.341, 0.334), a good correlated color temperature (CCT) of 5083 K, and a high color rendering index (Ra) of 92. Revealing its potential as yellow-emitting phosphors, the feasibility of the fabricated apatite-type NaCa3Bi(PO4)3F:Dy3+ fluorophosphate phosphors was confirmed for w-LEDs.

Blue-light-excitable broadband yellow-emitting CaGd2HfSc(AlO4)3:Ce3+ garnet phosphors for white light-emitting diode devices with improved color rendering index

The current commercial white light-emitting diodes (LEDs) are generally based on the combination of blue LED chips and Y3Al5O12:Ce3+ yellow phosphors. However, because of the lack of red component, such white LED devices exhibit cool white-light emissions with low color rendering index (Ra < 75, R9 < 0). Therefore, it is urgent to discover new blue-light-excitable yellow-emitting phosphors with enhanced red emissions for fabricating high color-quality white LEDs. In the present work, we demonstrate a novel broadband yellow-emitting CaGd2HfScAl3O12:Ce3+ garnet phosphor for blue-light-excited white LEDs with improved color rendering index. The as-prepared CaGd2HfScAl3O12:Ce3+ garnet phosphor possesses a cubic structure with Ia3¯d space group, and the unit cell parameters of the representative CaGd2HfScAl3O12:2%Ce3+ phosphor are a = b = c = 12.450 Å, α = β = γ = 90°, and V = 1,929.59(4) Å3. Impressively, we find that the CaGd2HfScAl3O12:Ce3+ garnet phosphor shows an intense absorption band in the 300–500 nm wavelength range with a maximum at 452 nm owing to the 4f→5d transition of Ce3+ ions. On 452 nm excitation, the optimal CaGd2HfScAl3O12:2%Ce3+ sample exhibits a broad asymmetric yellow emission band in the wavelength range of 470–750 nm with peak at 564 nm and full width at half maximum of 151 nm. The Commission Internationale de l’Eclairage chromaticity coordinates and internal quantum efficiency of the CaGd2HfScAl3O12:2%Ce3+ sample are (0.4485, 0.5157) and 30.4%, respectively. Finally, a white LED device is fabricated by combing a 450 nm blue LED chip with commercial Y3Al5O12:Ce3+ yellow-emitting phosphor, which generates white light with low color rendering index (CRI; Ra = 74.7, R9 = −12.7) and high correlated color temperature (CCT = 6,554 K) under the 60 mA driving current. In sharp contrast, another white LED device, which is made by coating our as-prepared CaGd2HfScAl3O12:2%Ce3+ yellow-emitting phosphors onto the surface of a 450 nm blue LED chip, produces white-light emission with high CRI value (Ra = 84.5, R9 = 26.3) and relatively low CCT of 5,649 K. This work reveals that the newly discovered broadband yellow-emitting CaGd2HfScAl3O12:Ce3+ phosphors can serve as a potential color converter in high-color-quality phosphor-converted white LEDs.

Synthesis and luminescence properties of yellow-emitting phosphor Tb2.93Al5O12:0.07Ce3+ under blue light excitation

Using α-Al2O3, Tb4O7 and CeO2 as raw materials, Tb2.93Al5O12: 0.07Ce3+ yellow phosphors for white light-emitting diodes (w-LEDs) are prepared by the high-temperature solid-phase method under a reducing atmosphere. Furthermore, X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM) and fluorescence spectroscopy (PL) are employed to characterize the structure, morphology and photoluminescence properties of the name. The results reveal that the pure Tb3Al5O12 is synthesized under a reducing atmosphere (95% N2 + 5% H2) at 1500 °C (4 h). Under the excitation of blue light with a wavelength of 450 nm, the Tb3Al5O12:Ce3+ exhibited a broadband yellow light emission peak at 553 nm. Also, the color coordinates of Tb3Al5O12:7%Ce3+ are found to be 0.4709 and 0.5175. Overall, the as-prepared yellow phosphor is suitable for w-LEDs under blue light excitations.

One-pot synthesis of metal-free, yellow-emitting phosphor with organic single crystal as a matrix

In recent years, there is a rapid growth on the research of metal-free phosphor. A typical example is blend of photoluminescent carbon nanomaterials with a matrix. Normally, the C dots were prepared first, which were then mixed with the matrix. A drawback of this strategy is that multiple steps have to be involved, which is time consuming. In this work, we show that by simply heating a readily-available small organic molecule (phthalic acid) in a high-boiling solvent with reactive group (formamide), ready-to-use and metal-free phosphor can be produced in high yields (over 70%). The phosphor contains single crystals of phthalic anhydride with photoluminescent species adsorbed on the surfaces, which shows yellow emission in solid state with a fluorescence quantum yield (Φ) of 28.53%. The phosphor can be directly used to prepare light-emitting diodes (LEDs), which results in a yellow LED on the UV chip and a white LED on the blue-emitting chip.

Exploration of yellow-emitting phosphors for white LEDs from natural resources.

White light-emitting diodes (LEDs) are widely used in various lighting fields as a part of energy-efficient technology. However, some shortcomings of luminescent materials for white LEDs, such as complexity of synthesis, high cost, and harmful impact on the environment, limit their practical applications to a large extent. In this respect, the present work aims to study the ability of using Berberine (BBR) chloride extracted from Rhizoma coptidis and Phellodendron Chinese herbs as yellow phosphor for white LEDs. For this, white LEDs were successfully fabricated by applying 0.006 g of BBR chloride onto the blue LED chips (450 nm). The produced LEDs exhibited good luminescence properties at a voltage of 2.4 V along with eco-friendly characteristics and low cost. The Commission International de l'Eclairage chromaticity, the correlated color temperature, and the color rendering index were determined to be (${x} = {0.32}$, ${y} = {0.33}$), 5934 K, and 74, respectively. Therefore, BBR chloride is a suitable environmentally friendly and easily accessible yellow phosphor for white LEDs.

Improved thermal stability and luminescence properties of SrSi2O2N2:Eu2+ green phosphor by a heterogeneous precipitation protocol for solid-state lighting applications

The SrSi2O2N2:Eu2+ green-emitting phosphor, as a member of oxynitride phosphors, could greatly enhance the color quality of the white-light conversed by single yellow-emitting phosphor. However, SrSi2O2N2:Eu2+ phosphors prepared by traditional solid-state ways normally consist hard agglomerates with unevenly dispersed particles and therefore suppress the luminescence properties. This research proposes a heterogeneous precipitation protocol where precipitation process is introduced, in order to produce a precursor in the first phase. And in the second phase, a high-temperature solid-state process is adopted for obtaining the final product. The main results show that, for an optimized SrSi2O2N2:Eu2+ phosphor prepared using our protocol, (1) the SrSi2O2N2:Eu2+ particles are faceted and with smooth faces and (2) the phosphor photoluminescence, external quantum efficiency, stability against thermal exposure, and physical stability consistently outperform the current commercially used product. This research essentially provides an economic way for production of solid-state lighting with enhanced color quality.

Encapsulating carbon quantum dot and organic dye in multi-shell nanostructured MOFs for use in white light-emitting diode

Abstract Encapsulating luminescence units into porous metal-organic frameworks to obtain white-light emission has attracted much attention because of their high designability and excellent color-tuning flexibility. In this study, two types of luminescence units with different emission color coverage, namely green-emitting carbon quantum dots (CQDs) and red-emitting rhodamine B (RhB) molecules, were encapsulated into porous ZIF-8 to obtain the yellow-emitting composite phosphor for use in white light-emitting diodes (LEDs). Single-phase single-shell CQDs&RhB@ZIF-82, as well as single-phase multi-shell CQDs@ZIF-82@RhB@ZIF-82, were fabricated and fine-tuned (by varying the amount of accommodated CQDs and RhB) so that the emitted color is near that of the commercial yellow-emitting phosphor. The multi-shell CQDs@ZIF-82@RhB@ZIF-82 has much better luminescence efficiency than that of the single-shell one. This is because the multi-shell structure provides a much larger separation distance of the encapsulated guest units, diminishing the energy-transfer-caused efficiency decrease. It is also shown that a bright source of white light can be realized by coating the CQDs@ZIF-82@RhB@ZIF-82 nanocomposite on a commercial blue (460 nm) LED chip.

Synthesis, luminescent properties and ab initio study of yellow-emitting Sr8MgGa(PO4)7:Eu2+phosphors for white light-emitting diodes

In this study, a series of Sr8MgGa(PO4)7:Eu2+ (SMGP:Eu2+) phosphors are prepared by a solid state reaction. The phase purity, crystal structure, luminescence properties, decay lifetime as well as thermal quenching and CIE chromaticity coordinates are thoroughly investigated. The as-synthesized SMGP:Eu2+ phosphors demonstrate a broad absorption band extending from 250 to 500 nm, which could be excited at near UV or blue chips. The composition-optimized SMGP:1%Eu2+ phosphor exhibit intense yellow emission at 590 nm with a FWHM (Full Width at Half Maximum) of 82 nm under 396 nm excitation. Performed DFT calculations of SMGP host and SMGP:Eu2+ phosphors explained the process of creating valence and conductivity bands, The calculated bandgaps are consistent with determined from reflectance measurements. In addition, we fabricate white light emitting devices (WLEDs) by integrating the yellow-emitting SMGP:Eu2+ phosphor, commercial blue-emitting BaMgAl10O17:Eu2+ (BAM) phosphor and a 380 nm near UV chip, which displayed excellent white light described by CIE chromaticity coordinates at (0.30, 0.31), high CRI (Ra = 91) and CCT (7129 K). The results convincingly indicate that SMGP:1%Eu2+ is an efficient yellow-emitting phosphor for WLEDs applications.

Design of Novel Highly Efficient Yellow-Orange Color-Tunable Luminescence in Rb2Sr1-yCayP2O7:xEu2+ Solid Solutions for White Light-Emitting Diodes.

Traditional white light-emitting diodes (WLEDs) are limited by the energy loss due to reabsorption. Integrating binary complementary color phosphors with near-ultraviolet (n-UV) LED chips can be a good solution, and the core of it is to develop yellow-emitting phosphors. In this work, we have designed Rb2Sr1-yCayP2O7:xEu2+ solid solutions with yellow-orange color-tunable luminescence. The crystal structure, luminescence properties, and potential applications for WLEDs were explored systematically. Under n-UV light excitation, the phosphors efficiently emit broadband yellow-orange emission. The reasons and mechanisms of the variation of the PL/PLE spectra have been investigated. The optimal Rb2SrP2O7:0.5% Eu2+ sample exhibits a high quantum efficiency of 72.96% with a good color purity of 87.1%. Upon combination of the BAM:Eu2+ and Rb2SrP2O7:0.5% Eu2+ phosphors with a 380 nm n-UV chip, a WLED device is fabricated and can emit white light with good performance.

Insight into the crystal structure and photoluminescence properties of an extremely broadband yellow-emitting phosphor Sr8MgCe(PO4)7:Eu2.

The combination of binary complementary color phosphors with near-ultraviolet (NUV) light-emitting diode (LED) chips was put forward to lower the energy loss caused by the reabsorption of the combination of tricolor phosphors with NUV LED chips. Thus investigating broadband yellow-emitting phosphors with enriched red components in the spectral range has gained much attention. Here, an extremely broadband yellow-emitting phosphor Sr8MgCe(PO4)7:Eu2+ with sufficient red component in the spectral region was synthesized. Due to the introduction of Ce into the host, Sr8MgCe(PO4)7 shows an emission band with a peak at 375 nm when excited at 310 nm. Meanwhile, Eu2+ doped Sr8MgCe(PO4)7 exhibits an extremely broad yellow emission band with a full width at half-maximum of 175 nm and a peak located at about 598 nm, due to the 5d-4f transitions of Eu2+ ions substituting five Sr2+ sites. The excitation peak of the host at 310 nm was detected in the excitation spectrum of Sr8MgCe(PO4)7:Eu2+ monitored at 598 nm, indicating the energy transfer from the host to Eu2+, which was also proved by the decay curves. On the other hand, the excitation band at about 400 nm due to the 4f-5d transitions of Eu2+ was also detected in the excitation spectrum of Sr8MgCe(PO4)7:Eu2+, and this matches well with the NUV LED chips. Moreover, the energy transfer between Eu2+ ions at different crystallographic sites was demonstrated by time-resolved photoluminescence (TRPL) spectra. A white LED with a CRI (Ra) of 82.88 and a CCT of 4238 K was prepared through a 400 nm NUV LED chip, Sr8MgCe(PO4)7:Eu2+ and BaMgAl10O17:Eu2+ (BAM:Eu2+). These results pave the way for designing better Eu2+-doped phosphors for NUV WLEDs with binary complementary color phosphors.

The application of double-layer remote phosphor structures in increasing WLEDs color rendering index and lumen output

The remote phosphor structure often has inferior color quality but better luminous flux in than conformal or in-cup configurations. Therefore, numerous researches study remote phosphor structure for methods to enhance it chromatic quality. This study introduces the use of dual-layer remote phosphor structure in WLEDs with identical structure but at different color temperature, 6600K and 7700K, to demonstrate their effect on quality indicators. The concept is placing a green phosphor layer (Ce,Tb)MgAl11O19:Ce:Tb or a red phosphor layer MgSr3Si2O8:Eu2+,Mn2+ on the layer of yellow-emitting phosphor YAG:Ce3+ and find the suitable concentration of the additional phosphor to create the best color quality. The results showed that the increase of CRI and CQS are affected by MgSr3Si2O8:Eu2+,Mn2+, in particular, the higher the concentration of red phosphor gets the better CRI and CQS because the emitted red light in enhanced. The green phosphor layer (Ce,Tb)MgAl11O19:Ce:Tb, on the other hand, is beneficial for the luminous flux. The concentration of MgSr3Si2O8:Eu2+,Mn2+ and (Ce,Tb)MgAl11O19:Ce:Tb, however, need to be adjusted properly to avoid decreasing the luminous flux due to overgrowth. The Mie scattering theory and Beer’s law are the verification tools for these conclusions, which gives them the credibility to be applied in producing better quality WLEDs.

Synthesis and optical properties of novel double perovskite Ca2MgTeO6:Dy3+,Na+ phosphors for white LEDs

Novel yellow-emitting phosphors of Dy3+-doped double perovskite Ca2MgTeO6 were synthesized by using a conventional high-temperature solid-state reaction. The phase purity, particle morphology, size distribution, elemental composition, luminescence properties, and luminescence decay curves of the resulting products were then analyzed in detail. The Ca2MgTeO6:Dy3+,Na+ phosphors show three emission peaks after near-ultraviolet excitation at 350 nm, which correspond to 4F9/2 → 6H11/2, 4F9/2 → 6H13/2, and 4F9/2 → 6H13/2 transitions, respectively. Among them, the strongest peak is observed at 573 nm. The best doping content of Dy3+ in Ca2MgTeO6:xDy3+,xNa+ phosphors is x = 5 mol%. The calculated critical distance of energy transfer between Dy3+ ions is 1.6 nm. Luminescence quenching is confirmed to be due to dipole-dipole interactions among Dy3+ ions. The phosphors show excellent thermal stability with high activation energy (0.27 eV). The Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of the Ca2MgTeO6Dy3+,Na+ phosphors are located in the yellow region. White light-emitting diodes (w-LEDs) were fabricated with a high color rendering index (Ra) of 88 and a good correlated color temperature (CCT) of 5440 K. All observed properties indicate that Ca2MgTeO6:Dy3+,Na+ phosphors have potential applications in display and photonic devices.

KCa2Mg2V3O12: A novel efficient rare-earth-free self-activated yellow-emitting phosphor

The development of efficient near-ultraviolet (near-UV) excitable inorganic phosphors is highly important for application in near-UV-pumped white light-emitting diodes (LEDs). Herein, we reported on a novel efficient rare-earth-free yellow-emitting KCa2Mg2V3O12 vanadate phosphor. These phosphors were prepared by using a conventional high-temperature solid-state reaction method. Photoluminescence study revealed that KCa2Mg2V3O12 phosphor exhibited a broad excitation band in the 250−420 nm wavelength range with a peak at 346 nm, owing to the absorption of [VO4]3− groups. Upon 346 nm excitation, KCa2Mg2V3O12 phosphor showed bright yellow emission in the 400−800 nm range with a maximum at 540 nm and a full width at half maximum of 161 nm. Such self-activated broadband yellow luminescence was attributed to the 3T2→1A1 and 3T1→1A1 transitions of [VO4]3− groups. The Commission Internationale de l´Eclairage (CIE) color coordinates were calculated to be (0.3741, 0.4679), which were located in the yellow region in the CIE chromaticity diagram. Impressively, the internal quantum efficiency of KCa2Mg2V3O12 phosphor was measured to be as great as 41 %. In addition, the temperature-dependent emission spectra were recorded, and the activation energy Ea was determined to be 0.366 eV. The newly developed KCa2Mg2V3O12 phosphor might have application potential as color converter in white LEDs.

High-Brightness Red-Emitting Phosphor La3(Si,Al)6(O,N)11:Ce3+ for Next-Generation Solid-State Light Sources.

A novel high-brightness red-emitting phosphor, La3(Si,Al)6(O,N)11:Ce3+ (LSA), which can potentially be used as a laser-excited light source, is demonstrated. Laser-excited phosphor system has great potential for use as a white-light source, as it is orders of magnitude brighter than white LEDs. Although conventional yellow-green phosphors show excellent luminescent properties even under high-power laser excitation, red-emitting phosphors, which are essential to achieve a high color-rendering index and low color-temperature, show quantum efficiency quenching. This limits the output power in multiphosphor excitation systems. Ce3+ should successfully tolerate high-power excitation due to the shortest emission lifetime seen in rare-earth ions, caused by the 5d1-4f1 spin-allowed transition; however, a red-emitting Ce3+-doped phosphor of practical use has not been realized. LSA is described by the crystal-field modification of a yellow-emitting phosphor, La3Si6N11:Ce3+, with substitution of Al in Si sites. LSA shows 640 nm red emission together with tolerance for high-power excitation and thermal quenching, suggesting its significant potential for industrial applications that require ultrahigh brightness.

Synthesis and luminescence properties of La7Ta3W4O30:Dy3+ yellow-emitting phosphor for solid-state lighting applications

This work was the first to synthesize the yellow-emitting phosphor La7Ta3W4O30:Dy3+ via a high-temperature solid reaction. The structure of La7Ta3W4O30:Dy3+ is trigonal crystalline pertaining to the R-3 (No.148) space group. Under 388-nm excitation, the photoluminescence spectrum of the La7Ta3W4O30:0.10Dy3+ sample exhibited four sharp peaks, which were attributed to 4F9/2–6H15/2 (480 nm), 4F9/2–6H13/2 (573 nm), 4F9/2–6H11/2 (658 nm), and 4F9/2–6H9/2 (753 nm) transitions. The optimal doping content of Dy3+ was 10 mol%, and the critical transfer distance (Rc) of the energy transfer between Dy3+ reached 22 A. The concentration quenching mechanism involved the dipole–dipole interaction. The quenching temperature was higher than 450 K. The fabricated white light-emitting diode (W-LED) possesses a high color rendering index (Ra = 88), good correlated color temperature (5710 K), and chromaticity coordinates (0.328, 0.335) that are close to those of standard white light (0.333, 0.333). Therefore, this prepared phosphor is a potential candidate for W-LED applications.

Highly Efficient Cyan-Green Emission in Self-Activated Rb3RV2O8 (R = Y, Lu) Vanadate Phosphors for Full-Spectrum White Light-Emitting Diodes (LEDs).

Phosphor-converted white-light-emitting diodes (pc-WLEDs) rely on combining a near-ultraviolet (n-UV) or blue chip with trichromatic and yellow-emitting phosphors. It is challenging to discover cyan-green-emitting (480-520 nm) phosphors for compensating the spectral gap and producing full-spectrum white light. In this work, we successfully discovered two unprecedented bright cyan-green emitting Rb3RV2O8 (R = Y, Lu) phosphors that gives emission bands centered at 500 nm upon 362 nm n-UV light excitation. Interestingly, the both self-activated compounds exhibit high internal quantum efficiencies (IQEs) of 71% for Rb3YV2O8 and 85% for Rb3LuV2O8, respectively. Moreover, controllable emission color can be successfully tuned from cyan-green to orange-red across the warm white light region by design strategy of VO43- → Eu3+ energy transfer. The thermal quenching of as-prepared phosphors could be effectively mitigated by this design strategy. Finally, the as-fabricated n-UV (λex = 370 nm) pumped phosphor-converted (pc) W-LED devices utilizing Rb3RV2O8 (R = Y, Lu) along with commercial phosphors demonstrate well-distributed warm white light with high color-rendering index (CRI) of 91.9 and 93.5, and a low correlated color temperature (CCT) of 5095 and 4946 K. It suggests that the both vanadate phosphors have potential applications in full-spectrum pc-WLEDs.