Intense Yellow Emission Research Articles

Effect of doping charge compensator Li+ on structure and luminescent properties of ZnWO4: Eu3+, Dy3+ phosphor

The white-light emitting phosphors ZnWO4:Eu3+,Dy3+ with Li+ as charge compensator were prepared by a hydrothermal method followed with calcination process. And the effects of Li+ doping amount on the structure and luminescent properties of samples were investigated. The results indicate that the introduction of Li+ has little effect on the crystal structure of samples. The particles of the phosphor are approximately spherical in shape, and the size is about 70–100 nm. The main excitation peak of samples is at 297 nm, ascribed to the W6+-O2− charge transfer state (CTS) transition. The emission spectra are composed of blue-green emission band of WO42−, yellow and blue emission peaks of Dy3+, and red emission peaks of Eu3+. With the increase of Li+ doping amount, the emission intensity of Dy3+ firstly increases and then decreases, but the emission intensity of WO42− decreases gradually, and that of Eu3+ remains almost unchanged. When the doping amount of Li+ is 2.5%, the yellow emission intensity of Dy3+ (576 nm) reaches the highest, which is 1.26 times of the uncompensated sample. The emitting color of phosphors can be tuned from the blue-white light through white light to the yellowish-white zone by the increase of Li+ doping amount.

Sharply-precipitated spherical assembly of ZnO nanosheets for low temperature H2S gas sensing performances

We report the room-temperature preparation of ZnO nanostructures and their gas sensing properties. Nanosheet-constructed ZnO spheres were chemically precipitated in a surfactant-free alkaline solution in just a few minutes. X-ray diffraction and Raman spectra confirm the wurtzite structure of ZnO. Electron microscopy observations reveal the nanosheets having {101¯0} facets are grown in the [0001] direction. The nanosheets are formed as a result of the lateral oriented attachment of paralleled nanorods through edge sharing. The electronic band gap of ZnO is determined to be 3.37 eV from the band edge optical absorption. An intense yellow emission at 595 nm appears in the photoluminescence spectra, implying that the solution-grown ZnO is rich in oxygen. The ZnO architectures display linear sensitivity, good selectivity and repeatability for the sensing of 5–100 ppm H2S at 70 °C. The superior H2S sensing properties of the ZnO nanostructures are ascribed to their ultrathin building blocks of nanosheets.

An in-depth study of the Judd-Ofelt analysis, spectroscopic properties and energy transfer of Dy3+ in alumino-lithium-telluroborate glasses

Abstract Dy3+-doped glasses with compositions of (69-x)B2O3 + 10TeO2 + 10Al2O3 + 10Li2O + xDy2O3 (x = 0.1; 0.5; 1.0 and 2.0 mol%) were prepared by a melt–quenching technique. An in-depth Judd-Ofelt analysis has been carried out to estimate the influence of the hypersensitive transitions (HST) of Dy3+on the validity of the obtained intensity parameters Ωλ (λ = 2, 4, 6). The thermalization effect of the three-levels system of 6H13/2 (level 0), 4F9/2 (level 1) and 4I15/2 (level 2) was taken into account to evaluate its radiative transition probabilities, life times and energy levels. The obtained results were compared with the experimental data to estimate the validity of the Judd-Ofelt analysis. The Inokuti-Hirayama model was used to analyze the luminescence decay curves. The dipole-dipole interaction was shown to be the dominant mechanism in energy transfer process through cross-relaxation between Dy3+ ions. The possibility to produce the light with chromaticity coordinates in the white-light region by mixing intense blue (484 nm, 4F9/2 → 6H15/2) and yellow (575 nm, 4F9/2 → 6H13/2) emissions of the single Dy3+doped alumino-lithium-telluroborate glass was observed and estimated.

Structural, photoelectrical and photoluminescence properties of Ta-doped SnO2 monocrystal films grown on MgF2 (110) substrates

Epitaxial Ta-doped SnO2 films with Ta concentrations from 0 to 8 at.% have been deposited on MgF2 (110) substrates by the metal-organic chemical vapor deposition (MOCVD) method. The effects of Ta doping on the structural, photoelectrical and photoluminescence (PL) properties of the obtained films were studied in detail. The results showed that the single crystal rutile SnO2 films were obtained and the heteroepitaxial relationship was SnO2 (110) || MgF2 (110) with SnO2 [001] || MgF2 [001]. The highest Hall mobility of 74.2 cm2 V−1 s−1 was achieved for the 5 at.% Ta-doped SnO2 film and the minimum resistivity as low as 2.5 × 10−4 Ω cm was obtained at 6 at.% of Ta-doping. In the visible region, all the obtained films had average transmittances exceeding 87%. As the Ta concentration increased from 0 to 8 at.%, the optical band gap of the films rose from 3.89 to 4.32 eV. The room temperature PL spectra of Ta-doped SnO2 films showed intense green emission, weak violet and yellow emissions. The corresponding PL mechanisms were discussed.

Intense Yellow Emission from Gd0.5-yTb1.5REyW3O12 (RE = Eu, Sm) Phosphors Tuned through Full Range Doping

Intense Yellow Emission from Gd0.5-yTb1.5REyW3O12 (RE = Eu, Sm) Phosphors Tuned through Full Range Doping

Synthesis and Photoluminescence Properties of Yellow γ-Ca2SiO4-δNδ:Ce3+,Ga3+ Phosphors

γ-Ca2SiO4:Ce3+ phosphors were successfully synthesized through the synergistic stabilization effect of Ga3+ and N3−. Ga3+ ions effectively promote β → γ phase transformation, compared to the effect of the conventionally used Al3+ ions. When Ga2O3 was used in the raw materials as the source of Ga3+, the optimum amount of Ga3+ ions was 1%, which decreased to 0.75% when GaN was used for providing the Ga3+ ions in the produced phosphors. The phenomenon of “dusting” occurred, ascribed to the fact that the phosphor was in the form of a fine soft powder, owing to the volume increase and the angular unit cell change during phase transformation. The produced γ-Ca2SiO4-δNδ:Ce3+,Ga3+ phosphors exhibited an intense wide yellow emission band, with a peak at 565 nm, upon 450 nm excitation, which is attributed to the 4f05d1→4f1 transitions in the Ce3+ ions, and a good thermal quenching, with the photoluminescence intensity of γ-(Ca0.995Ce0.005)2Si0.9925Ga0.0075O4-δNδ at 150°C being ∼76% of the intensity measured at room temperature.

High temperature synthesis of yellow-emitting Y2BaAl4SiO12:Ce3+ phosphors for WLED applications

Yellow-emitting Y2BaAl4SiO12:Ce3+ (YBAS:Ce3+) phosphors were synthesized by a sol-gel method followed by annealing at high temperature. The phase purity of the YBAS:Ce3+ phosphors was confirmed by X-ray diffraction analysis. The emission characteristics of YBAS:Ce3+ phosphors were investigated by measuring their photoluminescence excitation and emission spectra. These phosphors can be efficiently excited with blue light that induced an intense yellow emission peak centered at 530 nm. White light-emitting diodes (WLEDs) were fabricated using the synthesized YBAS:6Ce3+ phosphors. The CIE chromaticity coordinates of YBAS:6Ce3+ and the fabricated WLEDs were located at the yellow (0.391, 0.563) and cool white-light (0.265, 0.326) regions, respectively.

Synthesis, structure, photo- and electroluminescent properties of bis(2-phenylpyridinato-N,c2′)[2-(2′-tosylaminophenyl)benzoxazolato-N,N′]iridium(III)

A new highly luminescent iridium complex, bis(2-phenylpyridine-N,C2′)[2-(2′-tosylaminophenyl)benzoxazole-N,N′]iridium(III) [Ir(ppy)2(TAPBO)] (TAPBO- 2-(2′-tosylaminophenyl)benzoxazole) has been synthesized and its molecular structure determined using single crystal X-ray diffraction analysis. The Ir(III) complex displayed intense yellow photophosphorescence emission that manifested its potential for organic electroluminescence. Photo- and electroluminescent properties of the OLEDs fabricated on the basis of [Ir(ppy)2(TAPBO)] with doping concentration of Ir(ppy)2(TAPBO) varied from 3 to 20 wt% have been investigated. The OLED with 9 wt% Ir(ppy)2(TAPBO) exhibited maximum luminance of 9000 cd m−2 at 180 mA/cm−2 and had sufficiently low turn-on voltage of ca. 6 V.

Excellent luminescence films of excitation-independent carbon quantum dots toward non-rare-earth phosphor-based white light-emitting diodes

Currently, fluorescent carbon quantum dots have been extensively studied for their promising application in solid-state lighting. However, most of the reported carbon quantum dots exhibit short-wavelength blue-green emissions and the obtained carbon solid powders usually show weak luminescence due to aggregation-induced emissive quenching. In this work, carbon quantum dots with excitation wavelength independent yellow emission were synthesized by a facile and green hydrothermal route using water as solvent and o-phenylenediamine as carbon source. Structural and spectroscopic characterizations evidenced that N-related defect state was responsible for yellow luminescence. Importantly, the carbon quantum dots embedded solid films were successfully prepared, which exhibited strong blue light absorption and retained intense yellow emission. As a proof-of-concept experiment, carbon polymer monolith was demonstrated to be an alternative to traditional Ce: Y3Al5O12 phosphors as color converter for constructing white light-emitting diode device with improved color rendering index and correlated color temperature.

Tailoring tail-free nematogen of ethynylated-schiff base and its evaluation as solution-processable OLED emitting material

A new rigid core dye comprised ESB-NO2 of chromophore moieties of acetylide (C≡C), Schiff base (C˭N) and nitro (NO2) was successfully synthesized to demonstrate tail-free nematogen as emitting material for organic light-emitting diode (OLED). The relationship between liquid crystal molecular structure, phase transition temperature and electroluminescence behaviour were evaluated. The mesomorphic properties of ESB-NO2 were identified via polarized optic microscopy (POM) which displayed nematic phase of Schlieren textures and their corresponding transition enthalpies were respectively recorded at 25.15 kJ mol−1. The photoluminescence behaviours of ESB-NO2 have been verified at λem,max = 538 nm where this emission are for its π→π * transition, intramolecular charge transfer (ICT) absorptions and fluoresce characters. Having ESB-NO2 as liquid crystalline material, OLED was constructed featuring single-layer indium tin oxide (ITO) coated substrate/ESB-NO2/Au via solution-casting method. The result revealed the single layer ESB-NO2 film displayed satisfactory electroluminescence with intense yellow emission under different direct current (DC) voltages supply. These findings indicate the practicability of designing tail-free nematogenic compounds as promising solution-processed OLED materials.

Microwave-assisted one-step synthesis of white light-emitting carbon dot suspensions

In this contribution, we demonstrate that an aqueous solution with adjustable fluorescent color, including white light emission, can be achieved by a rapid one-step microwave synthesis method resulting in a mixture of blue-emitting carbon dots (CDs) and the yellow-emitting 2,3-diaminophenazine (DAP). Aqueous mixtures of o-phenylene-diamine (oPD) and citric acid (CA) are used as precursors. The resulting product structures are analyzed by FT-IR and NMR spectroscopy and the size of the resulting CDs is determined by atomic force microscopy to be 1.1 ± 0.3 nm. The synthesized solution exhibits two fluorescence emission peaks at 430 and 560 nm, which were found to originate from the CDs and DAP, respectively. The intensity ratio of both fluorescence peaks depends on pH, which is driven by the protonation state of DAP. In consequence, the fluorescence emission color of the CD solution can be tuned precisely and reproducibly from blue to white to yellow by careful control of the pH. Finally, at a pH level of 5.4, at which there is equal blue and yellow emission intensity, a white light emitting solution can be successfully produced in a very fast and simple synthesis procedure.

Tetranuclear cluster-based Pb(II)-MOF: Synthesis, crystal structure and luminescence sensing for CS2

A new Pb(II) coordination polymer, namely [Pb2(bptc)(DMA)]n (1, H4bptc = biphenyl-3,3′,5,5′-tetracarboxylic acid, DMA = N, N′- dimethylacetamide), has been synthesized by the combination of H4bptc with Pb(NO3)2 under solvothermal conditions. Single crystal X-ray diffraction analysis revealed that compound 1 features a 3D framework based on tetranuclear [Pb4(COO)6] subunits, and topological analysis revealed that compound represents a binodal (4, 8)-connected scu-type topological network with the point symbol of {416,612}{44,62}2. Luminescence studies indicated that 1 and 1’ (1′ represents the desolvated samples) showed intense yellow emissions. Significantly, 1′ exhibited sensitive luminescence sensing for CS2 solvent molecules at a low concentration.

Photoluminescence and cathodoluminescence of Mn doped zinc silicate nanophosphors for green and yellow field emissions displays

Mn2+-doped Zn2SiO4 (ZSM2+) was synthesized by a facile sol–gel technique. The obtained samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL) and cathodoluminescence (CL) techniques. Under UV excitation, spectra showed that the α-ZSM2+ phosphor exhibited a strong green emission around 525 nm and reached the highest luminescence intensity with the Mn doping concentration of 5 at.%. However, for the β-ZSM2+ phase, an interesting yellow emission band centered at ~ 575 nm of Mn2+ at the Zn2+ tetrahedral sites was observed. In addition, an unusual red shift with increasing Mn2+ content was also found and attributed to an exchange interaction between Mn2+. Both PL and CL spectra exhibit an intense green and yellow emission centered at ~ 525 and ~ 573 nm, respectively, due to the 4T1 (4G)-6A1 (6S) transition of Mn2+. Furthermore, these results indicated that the Mn2+-doped zinc silicate phosphors may have potential applications in green and yellow emissions displays like field emission displays (FEDs).

Thermochemiluminescent semiconducting polymer dots as sensitive nanoprobes for reagentless immunoassay.

Thermochemiluminescence (TCL) is a potentially simple and sensitive detection principle, as the light emission is simply elicited by thermally-triggered decomposition of a molecule to produce a singlet excited-state product. Here we report about TCL semiconductive polymer dots (TCL-Pdots) obtained by doping fluorescent cyano-polyphenylene vinylene (CN-PPV) Pdots with an acridine 1,2-dioxetane derivative. The TCL-Pdots showed remarkable stability over time and minimum leaching of the thermo-responsive species. Furthermore, detectability of TCL-Pdots was improved by taking advantage of both the high number of 1,2-dioxetanes entrapped in each nanoparticle (about 20 molecules per Pdot) and the 5-fold enhancement of TCL emission due to energy transfer from 1,2-dioxetane to the polymer matrix, which itself acted as an energy acceptor. Indeed, upon heating the TCL-Pdots to 110 °C, 1,2-dioxetane decomposes generating an acridanone product in its electronically excited state. The latter transfers its energy to the surrounding CN-PPV chains via the Förster mechanism (φFRET about 80%), resulting in intense yellow light emission (550 nm wavelength). We next conjugated streptavidin onto the surface of these TCL-Pdots and demonstrated their suitability for use in biological studies. In particular, we used TCL-Pdots as labels in a model non-competitive immunoassay for IgG detection, which showed a LOD of 13 nM IgG and a dynamic range extending up to 230 nM. By combining the biocompatibility, brightness and tunability of Pdot fluorescence emission with the thermally-triggered reagentless light generation from TCL 1,2-dioxetanes, a broad panel of ultrabright TCL nanosystems could be designed for a variety of bioscience applications, even in multiplexed formats.

Facile green approach for the synthesis of ZnO Superstructures: Their structural and photometric properties

Herein, we report the synthesis of ZnO superstructures (SS) by ultrasound route using Aloe vera (A.V) gel as bio-fuel. Various reaction parameters namely effect of fuel, pH, sonication time and power have been studied in detail. The structural properties were characterized by means of Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) etc., and further, photometric measurements were done by Commission International De I’Eclairage (CIE), Correlated colour temperature (CCT). The PXRD results confirmed the hexagonal phase of the ZnO. The FTIR spectrum shows strong absorption peak at 445 cm-1, along with two broad peaks. The broad peaks at 3748 cm-1 and 1218 cm-1 were due to the stretching of hydroxyl group of H2O molecules. The energy band gap estimated from DRS spectra was found to be in the range of 3.02-3.09 eV. The PL emission spectrum was recorded in the range of 450 – 700 nm upon the excitation at wavelength of 397 nm. From CIE it was observed that the product shows intense yellow emission and CCT was found to be 3171K. All the above results were fruitful in making use of the ZnO SS as a yellow component in light emitting diodes.

Experimental and theoretical approach on the optical properties of zinc borotellurite glass doped with dysprosium oxide

A series of glass samples with chemical formula {[(TeO2)0.7(B2O3)0.3]0.7(ZnO)0.3}1−x(Dy2O3)x where x=0.01, 0.02, 0.03, 0.04 and 0.05M fraction were synthesized through conventional melt-quenching method. The most common way to fabricate a glass material is by fusion of two or more component oxides followed by their quenching. This technique is known as melt-quenching technique. Kaur et al. (2016) [1] highlighted that the melt-quenching method able to enhance the mechanical properties like hardness and flexural strength of the material. The nature of the glass systems is proven to be amorphous based on the XRD pattern. The FTIR spectra of the glass systems confirm the existence of five bands which are assigned for the BO4, BO3, TeO4 and TeO3 vibrational groups. The density of the glass systems is increased with the addition of Dy2O3 while the molar volume is found to be inversely proportional to the density of the proposed glass. The optical properties of the glasses are determined through the absorption spectra obtained from the UV-VIS spectrophotometer. From the absorption spectra, the indirect and direct optical band gaps and the Urbach energy are found to be inversely proportional to each other. As the molar fraction of the Dy2O3 increased, the optical band gaps are observed to increase as opposed to the Urbach energy. For this glass system, the values of refractive index, electronic polarizability, oxide ion polarizability and the optical basicity are found to decrease as the addition of the dysprosium oxide is increased. From the emission spectra, two intense blue and yellow emission bands are observed, which correspond to the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+ ions respectively. The CIE chromaticity coordinates of the zinc borotellurite glass systems are found to be located in the white light region.

UV excitation band induced novel Na3Gd(VO4)2:RE3+ (RE3+ = Eu3+ or Dy3+ or Sm3+) double vanadate phosphors for solid-state lightning applications

The Na3Gd(VO4)2 (NGVO):RE3+ (RE3+ = Eu3+ or Dy3+ or Sm3+) single doped phosphor materials were synthesized by a citrate-based sol-gel method. The phase formation of NGVO host lattice at different calcination temperatures was analyzed by X-ray diffraction results, which confirmed a monoclinic phase with a space group of P21/c (14). The field-emission scanning electron microscope image of the NGVO sample revealed an agglomerated morphology which was further analyzed by its corresponding energy dispersive X-ray spectrum. Under ultraviolet excitations, the photoluminescence (PL) properties of NGVO:Eu3+, NGVO:Dy3+ and NGVO:Sm3+ phosphors exhibited intense red, yellow and reddish-orange emissions at 618, 575 and 646 nm owing to their characteristic 5D0 → 7F2, 4F9/2 → 6H13/2 and 4G5/2 → 6H9/2 electronic transitions, respectively. The optimum doping concentrations of Eu3+, Dy3+ and Sm3+ ions in the NGVO host lattice were determined to be 0.09, 0.02 and 0.01 mol, respectively. Dexter's theory demonstrates that the quadrupole interactions are responsible for the concentration quenching mechanism in the NGVO:Dy3+ and NGVO:Sm3+ phosphors. Furthermore, Commission International de I'Eclairage chromaticity diagram was obtained and temperature-dependent PL emission spectra were measured for the optimal NGVO:Eu3+, NGVO:Dy3+ and NGVO:Sm3+ phosphors.

Synthesis and luminescence in sol–gel auto-combustion-synthesized $$\hbox {CaSnO}_{3}{:}\hbox {Eu}^{3+}$$ CaSnO 3 : Eu 3 + phosphor

Undoped and Eu-doped \(\hbox {CaSnO}_{3}\) nanopowders were prepared by a facile sol–gel auto-combustion method calcined at \(800{^{\circ }}\hbox {C}\) for 1 h. The samples are found to be well-crystallized pure orthorhombic \(\hbox {CaSnO}_{3}\) structure. Photoluminescence (PL) measurements indicated that the undoped sample exhibits a broad blue emission at about 420–440 nm, which can be recognized from an intrinsic centre or centres in \(\hbox {CaSnO}_{3}\). Eu-doped \(\hbox {CaSnO}_{3}\) showed broad blue emission centred about 434 nm, a weak peak at 465 nm and a sharp intense yellow emission line at 592 nm. The emission situated at 592 nm was assigned to the f–f transition of \(^{5}\hbox {D}_{0}\rightarrow ^{7}\hbox {F}_{1}\) in \(\hbox {Eu}^{3+}\) ions. The afterglow emission and PL decay results in Eu-doped \(\hbox {CaSnO}_{3}\) phosphor, which revealed that there are at least two different traps in this phosphor. From the obtained results, \(\hbox {Eu}^{3+}\)-doped \(\hbox {CaSnO}_{3}\) phosphor could be proposed as a potential white luminescent optical material.

Development of sodium-zinc phosphate glasses doped with Dy3+, Eu3+ and Dy3+/Eu3+ for yellow laser medium, reddish-orange and white phosphor applications

A spectroscopy analysis of Eu2O3 (2.0mol%) or Dy2O3 (2.0mol%) singly-doped and Dy2O3 (2.0mol%)/Eu2O3 (2.0mol%) codoped sodium-zinc phosphate glasses is performed through their Raman, absorbance and photoluminescence spectra, and decay times. The phonon energy (1124cm−1) and electron–phonon coupling strength (0.028) of the glass host were determined using phonon side band spectroscopy. Laser parameter values (stimulated emission cross section, effective bandwidth, gain bandwidth and optical gain), obtained for the 4F9/2 → 6H13/2 yellow emission of the Dy3+ singly-doped glass, are higher than those reported for others 2mol% Dy2O3-doped oxide glasses, so that the magnitudes of such parameters could be suitable for a low threshold and a high gain of yellow laser emission. Additionally a value of the quantum efficiency close to the unity (0.96) was found for the dysprosium 4F9/2 level luminescence. The intense yellow emission relative to the 4F9/2 → 6H15/2 blue one leads to the Dy3+ singly-doped glass to emit neutral white light of 4647K upon 349nm excitation. The Eu3+ singly-doped glass can emit reddish-orange light of 2166K and red color purity of 97.7% upon 394nm excitation, whose (0.642, 0.351) CIE1931chromaticity coordinates are close to those (0.67, 0.33) of the red phosphor proposed by the National Television Standard Committee. The Dy3+/Eu3+codoped glass emission color can be tuned from warm white light of 3628K upon 349nm excitation to reddish-orange light of 1891 K after 364nm excitation. The warm white light emission is generated mainly by the transitions 4F9/2 → 6H13/2, 6H15/2 of Dy3+ and 5D0 → 7F2 of Eu3+, where Eu3+ is sensitized by Dy3+ through non-radiative energy transfer with an efficiency of 0.22. An electric dipole-dipole interaction into Dy3+ - Eu3+ clusters might be the dominant mechanism in the Dy3+ to Eu3+ energy transfer. Excitations at 349, 364 and 394nm can be obtained with AlGaN, GaN and InGaN based LEDs, respectively, and therefore Dy3+ and/or Eu3+ doped sodium-zinc phosphate glasses pumped by UV LEDs could be appropriate for solid state lighting technology as neutral/warm white and reddish-orange light sources.

A remote phosphor film of silicate-poly(styrene-co-glycidyl methacrylate) composites for NUV chip-based white LED

Herein we adopt a simple route to prepare silicate phosphor-containing transparent composite film which is able to emit white light on the base of a blue emitting co-polymer matrix poly(styrene-co-glycidyl methacrylate) under excitation of 365 nm. SEM micrographs indicate that the surface treated silicate phosphor particles modified by silane coupling agent and embedded in co-polymer matrix separate from each other with a certain spacing and without agglomeration. More importantly, mutual enhancement in characteristic emission peak of two ingredients is observed. By varying the weigh percentage of silicate phosphor, yellow-to-white photoluminescent color-tuning could be readily accomplished depending on the variation of the intensity ratios between the characteristic yellow emission of silicate phosphor and the blue luminescence of the polymer matrix. And white emission [CIE: (0.354,0.322)] could be obtained from the simultaneous blue and yellow emission (intensity ratios value is 0.93). Simple NUV-based WLEDs were fabricated using prepared silicate phosphor doped composite material, showing Tc of 5917 K, CRI of 84.6. When a larger size composite film was simply assembled with COB, large area white lighting device with a certain color reduction came into being. All the results indicate that the of silicate phosphor-containing transparent composite film has practical significance for the packaging of remote phosphor converted white LEDs.