Component In WLEDs Research Articles

Preparation and photoluminescence performance of BaMoO4:Sm3+ orange–red phosphor

In the present paper, orange–red BaMoO4:Sm3+ phosphor was synthesized by high-temperature solid-phase method. The morphology, elemental composition, crystal structure, photoluminescence performance, and charge compensation mechanism of BaMoO4:Sm3+ were investigated. Results indicated that the BaMoO4:Sm3+ phosphor particles were spherical-like in shape with approximate particle size of 2 μm and contained Ba, Mo, O, and Sm elements. The Rietveld-refinement of X-ray diffraction profile of BaMoO4:Sm3+ was consistent with a tetragonal lattice. Under 404 nm excitation of light, BaMoO4:Sm3+ phosphor showed the strongest emission peak at 649 nm and emitted an orange–red light. When the orange–red phosphor was packaged with a 395 nm UV chip and tested, the color coordinates were (0.3109, 0.3626) under a current of 60 mA, the color rendering index Ra = 81.5, and the color temperature was 6385 K. These results indicated that BaMoO4:Sm3+ red phosphor is suitable as a red light component in WLEDs and has potential practical applications.

Ternary type BaY2ZnO5: Eu3+ deep-red phosphor for possible latent fingerprint, security ink and WLED applications

Pc-WLEDs are considered to play a spectacular role in future generation light sources in view of their outstanding energy efficiency. In this regard, Eu 3+ activated BaY 2 ZnO 5 phosphor was prepared and investigated by XRD, PL and SEM analyses. Rietveld refinement analysis was carried out to confirm the structure of the synthesized phosphor. The prepared phosphor shows an intense red emission around 627 nm under excitation by near UV light. The 5 D 0 - 7 F 2 transition intensity of the prepared phosphor is three times higher compared to the commercial (Y,Gd)BO 3 :Eu 3+ red phosphor. The CIE colour coordinates of BaY 2 ZnO 5 :Eu 3+ (9mol%) phosphor corresponds to be (0.6169, 0.3742) and it has a high 97.9 % colour purity. The obtained results reveal the utility of BaY 2 ZnO 5 :Eu 3+ phosphor as an efficient red component in WLEDs, anti-counterfeiting and fingerprint detection applications. • Eu 3+ activated BaY 2 ZnO 5 deep-red emitting phosphor was synthesized at low temperature for possible applications in Latent fingerprint, Security ink & WLEDs. • The prepared phosphor absorbs near-UV and the intense emission lies in the deep-red region. • The BaY 2 ZnO 5 :Eu 3+ red phosphor shows three fold higher intensity ( 5 D 0 - 7 F 2 ) and high colour purity compared to the commercial (Y,Gd)BO 3 :Eu 3+ red phosphor.

Effect of Li+, La3+ co-doping on the photoluminescence enhancement of Sr3AlO4F:Sm3+ orange-red-emitting phosphor for white light-emitting diodes

A series of Sr3AlO4F:Sm3+, La3+, Li+ orange-red-emitting phosphors were synthesized via a solid-state reaction with charge compensator Li+ co-doping for luminescence enhancement. The X-ray diffraction results demonstrated that all samples were consistent with standard Sr3AlO4F structure belonging to tetragonal phase with I4/mcm space group. The effects of La3+ co-doping and Li+ co-doping on the structure and luminescence properties of Sr3AlO4F:Sm3+ were investigated. The emission spectrum of Sm3+-doped phosphors was composed of several emission peaks at 565 nm (4G5/2→6H5/2), 602 nm (4G5/2→6H7/2) and 650 nm (4G5/2→6H9/2), respectively. After co-doping La3+, the luminescence intensity of Sr3AlO4F:Sm3+, La3+ sample was elevated to 1.46 times of that of Sr3AlO4F:Sm3+ phosphor, which is in consequence of the environmental effect of crystal field around luminescence center. Furthermore, depend on charge compensation effect, the luminescence intensity of Sr3AlO4F:Sm3+, La3+, Li+ phosphor was further enhanced by 1.48 times higher than that of Sr3AlO4F:Sm3+, La3+ phosphor. A w-LEDs device was packaged via coating the as-prepared phosphor on n-UV chip of 395 nm with commercial phosphors. These results indicated that there is a potential application for Sr3AlO4F:Sm3+, La3+, Li+ phosphor as orange-red component in w-LEDs.

Structural and optical behavior of nano-scaled luminous green-emitting Ca9Y(PO4)7:Tb3+ phosphor for competent lighting devices

Nano-sized Ca9Y(1-x)(PO4)7:xTb3+ phosphor series was synthesized via solution-combustion method for the first time. Rietveld study revealed the incorporation of Tb3+ ions into monoclinic host lattice of R3c(161) space symmetry. The diffuse reflectance spectral investigations depicted the lowering of band-gap (Eg) value from 4.44 to 4.27 eV for Ca9Y(PO4)7 and Ca9Y0.30Tb0.70(PO4)7, respectively. Under near-Ultraviolet excitation, PL spectra yielded luminous green emission at 544 nm (5D4 → 7F5). For Ca9Y0.30Tb0.70(PO4)7 system, quantum efficiency and CIE chromaticity coordinates were determined to be 96% and (0.252, 0.564), respectively. The results as-obtained predict the potential implications of Ca9Y0.30Tb0.70(PO4)7 nanophosphor as primary green component in WLEDs.

Reddish-orange emission from sol-gel derived Sm3+-doped Sr2La8(SiO4)6O2 phosphors

In this study, Sr2La8-x(SiO4)6O2:xSm3+ (where x=(0.01 ≤ x ≤ 0.11)) phosphors were prepared successfully via the sol-gel route. Their structural properties were evaluated through fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) measurements. The XRD patterns confirmed the purity of the prepared compound that had an average crystallite size of ∼38.8 nm. From the FTIR spectra, various stretching and bending vibrations of the SiO4 units were identified. The band observed at 540 cm−1 was attributed to the normal vibration mode of La-O. The optical properties of the prepared phosphor were assessed through diffuse reflection spectroscopy and photoluminescence measurements. The diffuse reflectance spectrum exhibited seven peaks from the Sm3+ ions corresponding to f-f transitions from the ground state, 6H5/2, to the excited states, 6G7/2, 4D7/2, 4D3/2, 6P7/2, 4L15/2, 6P3/2, and (4I11/2,4I13/2). Out of all these transitions, the peak at 407 nm is the most prominent, this peak come from the 6H5/2→6P3/2 transition, which offers the maximum absorption. The phosphor’s excitation spectrum revealed a charge-transfer (CT) band that extended from 220 to 270 nm and was centered around 240 nm. The excitation spectra also exhibited several transitions of the Sm3+ ion, among these, the transition corresponding to 403 nm was chosen as the pumping wavelength owing to its prominence. The most intense emission peak was observed at 599 nm, this corresponds to the 4G5/2→6H7/2 transition. This emission’s CIE chromaticity coordinates placed it in the reddish-orange region, suggesting that the titled phosphor is suited for orange-red LEDs and the red component in WLEDs.

The usage of dual-layer remote phosphor configurations in enhancing color quality and luminous flux of WLEDs

Among conformal phosphor structure, in-cup phosphor structure, and remote phosphor structure, while in term of attaining the highest luminous flux, remote phosphor structure is the most ideal one, it seems to be that this structure results in the lowest-quality of color. Therefore, it is necessary in conducting experiments to surmount this disadvantage and make a possibility in enhancing the color quality of WLEDs with remote phosphor structure. In this research, with the ability of advancing the color rendering index (CRI) and color quality (CQS) for WLEDs, a dual-layer remote phosphor structure was considered as a suggestion. The experiments in this study used three kinds of WLEDs with the similar structures but different color temperatures varying at 5600 K, 7000 K, and 8500 K. The objectives of this paper is proposing a solution to obtain the highest color quality by placing a yellow-green emitting SrBaSiO4:Eu2+ phosphor layer or a red-emitting SrwFxByOz:Eu2+,Sm2+ phosphor layer on the YAG:Ce3+ phosphor layer and then choosing the most appropriate value of SrwFxByOz:Eu2+,Sm2+ concentration. The experimental results which are satisfied expectations of researchers indicated that SrwFxByOz:Eu2+,Sm2+ has enforced its role in managing to raise the CRI and CQS. Particularly, the greater concentration of SrwFxByOz:Eu2+,Sm2+ leads to the higher the CRI and CQS, since the red light component in WLEDs increased. Besides, the quality of luminous flux is in a tight connection with the SrBaSiO4:Eu2+ phosphor layer. Whereas, according to the Mie scattering theory and the Lambert-Beer law, if the concentration of SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ becomes redundant, the luminous flux and color quality will take a deep dive. Briefly, the results from this article has largely contributed to fabricating high-quality WLEDs.

Improving luminous flux and color homogeneity of dual-layer phosphor sctructure

In order to clarify the main purpose of the study, we put a green phosphor layer SrBaSiO4:Eu2+ on the yellow phosphorus layer YAG:Ce3+ through using only one WLEDs structure in different color temperatures like 5600 K, 6600 K, 7700K. Then, we find the suitable SrBaSiO4:Eu2+ concentration in order that the luminous flux could get the highest value. The results show that SrBaSiO4:Eu2+ brings great benefits to increase not only optical gain but also color uniformity. Specifically, the greater the SrBaSiO4:Eu2+ concentration, the greater the output of WLEDs because of the development of green light component in WLEDs. However, only if the SrBaSiO4:Eu2+ concentration exceeds the level, a slight decrease in color rendering index (CRI) can occur, which based on Monte Carlo simulation. In addition, the results of this paper have contributed significantly to the creation of higher-powered WLEDs.

Enhancement of color quality scale and luminous flux of white LEDs with remote phosphor geometries

In comparison with the conformal phosphor or in-cup phosphor structure, remote phosphor structure has a superior luminous flux whereas its color quality is inferior to the others’. Due to this drawback, it is essential to conduct experiments to find the solution for the improvement of the color quality of WLEDs using remote phosphor structure. In this study, a dual-layer remote phosphor structure that is capable of enhancing the color rendering index (CRI) and color quality (CQS) for WLEDs was proposed. Three kinds of WLEDs with similar structures but different color temperatures varying at 5600 K, 7000 K, and 8500 K are used in this article. The mission of this paper is to place a yellow-green emitting SrBaSiO4:Eu2+ phosphor layer or a red-emitting SrwFxByOz:Eu2+, Sm2+ phosphor layer on the YAG:Ce3+ phosphor layer and then select the most appropriate value of SrwFxByOz:Eu2+, Sm2+ concentration to get the greatest color quality. Experimental results were exactly as expected since SrwFxByOz:Eu2+, Sm2+ really succeeded in increasing CRI and CQS. Specifically, the larger the SrwFxByOz:Eu2+, Sm2+ concentration, the higher the CRI and CQS, resulting from the increase of the red light component in WLEDs. Meanwhile, the quality degree of luminous flux depends tightly on the SrBaSiO4:Eu2+ phosphor layer. However, if the SrwFxByOz:Eu2+, Sm2+ and SrBaSiO4:Eu2+ concentration exceeds, the luminous flux and color quality will have a tendency to drop off, according to the theory of Mie scattering and the Lambert-Beer law. The result of this paper is a valuable reference in the production of high-quality WLEDs.

Improvement of Color Quality and Luminous Flux of WLEDs with Dual-Layer Remote Phosphor Configurations

In comparison with the conformal phosphor or in-cup phosphor structure, remote phosphor structure has a superior luminous flux whereas its color quality is inferior to the others’. Due to this drawback, it is essential to conduct experiments to find the solution for the improvement of the color quality of WLEDs using remote phosphor structure. In this study, a dual-layer remote phosphor structure that is capable of enhancing the Color Rendering Index (CRI) and Color Quality Scale (CQS) for WLEDs was proposed. Three kinds of WLEDs with the similar structures but different color temperatures varying at 5600 K, 7000 K, and 8500 K are used in this article. The mission of this paper is to place a yellow-green emitting SrBaSiO4:Eu2+ phosphor layer or a red-emitting SrwFxByOz:Eu2+,Sm2+ phosphor layer on the YAG:Ce3+ phosphor layer and then select the most appropriate value of SrwFxByOz:Eu2+,Sm2+ concentration to get the greatest color quality. Experimental results were exactly as expected since SrwFxByOz:Eu2+,Sm2+ really succeeded in increasing CRI and CQS. Specifically, the larger the SrwFxByOz:Eu2+,Sm2+ concentration, the higher the CRI and CQS, resulting from the increase of the red light component in WLEDs. Meanwhile, the quality degree of luminous flux depends tightly on the SrBaSiO4:Eu2+ phosphor layer. However, if the SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ concentration exceeds, the luminous flux and color quality will have a tendency to drop off thanks to the theory of Mie scattering and the Lambert-Beer law. The result of this paper is a valuable reference in the production of high-quality WLEDs.

GdAlO3:Eu3+:Bi3+ nanophosphor: Synthesis and enhancement of red emission for WLEDs

GdAlO3, GdAlO3:Eu3+ and GdAlO3:Eu3+:Bi3+ nanophosphors were synthesised by solution combustion technique. Pure orthorhombic phase was obtained from powder X-ray diffraction (PXRD) studies. Scanning electron microscopy (SEM) micrographs showed the porous, agglomerated and irregular shaped particles. The particle size obtained by transmission electron microscopy (TEM) measurement was in good agreement with the values obtained by Debye Scherrer’s and W–H plots. The selected area electron diffraction (SAED) pattern show single crystalline nature of the sample. Photoluminescence (PL) measurements were carried out for GdAlO3:Eu3+ and GdAlO3:Eu3+:Bi3+ phosphors excited at a wavelength of 274nm. The characteristic emission peaks of Eu3+ ions were recorded at 590, 614, 655 and 695nm corresponding to 5D0→7FJ (J=1, 2, 3, 4) transitions respectively. However, with addition of Bi3+ ions in GdAlO3:Eu3+, PL intensity drastically enhanced. Orange red color was tuned to deep red color with the addition of Bi3+ ions in GdAlO3:Eu3+ phosphor. Therefore, the phosphor was highly useful as red component in WLEDs. A single well resoled glow peak at 225°C was recorded in GdAlO3 and GdAlO3:Eu3+. Further, with addition of Bi3+ ions, an additional peak at 300°C was recorded. TL glow curves of different UV-exposed GdAlO3:Eu3+:Bi3+ show two TL peaks at 207 and 300°C respectively. The 207°C peak show simple glow peak structure and its intensity increases linearly up to 25min and after that it decrease.

Plant latex mediated green synthesis of ZnAl2O4:Dy3+ (1–9mol%) nanophosphor for white light generation

Abstract ZnAl2O4:Dy3+ (1–9 mol%) nanophosphors were synthesized by a simple, cost effective and environmental friendly route using Euphorbia tirucalli plant latex. The structural properties and morphological features of the phosphors were well studied by PXRD, FTIR, SEM and TEM measurements. The luminescent properties of ZnAl2O4:Dy3+ (1–9 mol%) nanophosphors were investigated from the excitation and emission spectra. The phosphor performance was evaluated by color co-ordinates. The values were well located in the near white region as a result it was highly useful for the fabrication of green component in WLEDs. The average particle size was found to be ∼9–18 nm and same was confirmed by TEM and Scherrer’s method. The highest photoluminescence (PL) and thermoluminescence (TL) intensity was obtained to be ∼7 mol% Dy3+ concentration. A single TL glow peak was recorded at 172 °C at a warming rate of 2.5 °Cs−1. The intensity at 172 °C peak increases linearly up to 1 kGy and after that it diminishes. PL intensity was studied with different plant latex concentration (2–8 ml) and highest PL intensity was recorded for ∼ 8 ml. The optimized phosphor showed good reusability, low fading and wide range of linearity with γ-dose hence the phosphor was quite useful in radiation dosimetry.