scholarly journals Spectral optimization of the color temperature tunable white light-emitting diode (LED) cluster consisting of direct-emission blue and red LEDs and a diphosphor conversion LED

2012 ◽  
Vol 20 (S5) ◽  
pp. A684 ◽  
Author(s):  
Ping Zhong ◽  
Guoxing He ◽  
Minhao Zhang
Keyword(s):  
White Light ◽  
Light Emitting Diode ◽  
Color Temperature ◽  
Light Emitting ◽  
Direct Emission ◽  
Spectral Optimization ◽  
Red Leds

scholarly journals Near Unity PLQY and High Stability of Barium Thiocyanate Based All-Inorganic Perovskites and Their Applications in White Light-Emitting Diodes

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 209
Author(s):  
Gopi Chandra Adhikari ◽  
Saroj Thapa ◽  
Yang Yue ◽  
Hongyang Zhu ◽  
Peifen Zhu
Keyword(s):  
White Light ◽  
Large Scale ◽  
Light Emitting Diode ◽  
Photophysical Properties ◽  
Environmental Stability ◽  
Color Temperature ◽  
Ambient Atmosphere ◽  
Light Emitting ◽  
Halide Perovskite ◽  
Lead Halide

All-inorganic lead halide perovskite (CsPbX3) nanocrystals (NCs) have emerged as a highly promising new generation of light emitters due to their extraordinary photophysical properties. However, the performance of these semiconducting NCs is undermined due to the inherent toxicity of lead and long-term environmental stability. Here, we report the addition of B-site cation and X-site anion (pseudo-halide) concurrently using Ba(SCN)2 (≤50%) in CsPbX3 NCs to reduce the lead and improve the photophysical properties and stability. The as-grown particles demonstrated an analogous structure with an almost identical lattice constant and a fluctuation of particle size without altering the morphology of particles. Photoluminescence quantum yield is enhanced up to near unity (~98%) by taking advantage of concomitant doping at the B- and X-site of the structure. Benefitted from the defect reductions and stronger bonding interaction between Pb2+ and SCN− ions, Ba(SCN)2-based NCs exhibit improved stability towards air and moisture compared to the host NCs. The doped NCs retain higher PLQY (as high as seven times) compared to the host NCs) when stored in an ambient atmosphere for more than 176 days. A novel 3D-printed multiplex color conversion layer was used to fabricate a white light-emitting diode (LED). The obtained white light shows a correlated color temperature of 6764 K, a color rendering index of 87, and luminous efficacy of radiation of 333 lm/W. In summary, this work proposes a facile route to treat sensitive lead halide perovskite NCs and to fabricate LEDs by using a low-cost large-scale 3-D printing method, which would serve as a foundation for fabricating high-quality optoelectronic devices for near future lighting technologies.

scholarly journals Chromaticity Study of Curcumin Dye Extracted from Curcuma longa L. Using for UV Light down Conversion for White Light Emitting Diode

2019 ◽  
Vol 290 ◽  
pp. 183-189
Author(s):  
Mahmood Al Shafouri ◽  
Naser Mahmoud Ahmed ◽  
Zainuriah Hassan ◽  
Munirah Abdullah Almessiere
Keyword(s):  
White Light ◽  
Uv Light ◽  
Light Emitting Diode ◽  
Curcuma Longa ◽  
Color Temperature ◽  
Light Emitting ◽  
Chromaticity Coordinates ◽  
Major Factors ◽  
Color Rendering ◽  
Down Conversion

In thus study, Turmeric phosphor dye was extracted from Curcuma Longa L. via a simple technique using silica gel. The phosphor was used for light down-conversion of UV light for the manufacture white light emitting diode (WLED). The UV-LED was analyzed over 395nm wavelengths. The characteristics of the white light chromaticity were controlled by tuning the current and phosphor concentration. An optimum color rendering index (CRI) value of 63.4 was obtained. The chromaticity coordinates (CIE) and correlated color temperature (CCT) were measured for various currents and phosphor concentrations. The white phosphor exhibited CIE value of 0.355,0.338 and CCT of 4567 K. The concentration of phosphor and amount of applied current were confirmed to be major factors that control the intensity of white light emitted from the sample, where CIE and CRI of the emitted light steadily increased with the concentration of phosphor and current. Thus, phosphor concentration has a critical effect on conversion efficiency. Key words: Turmeric, phosphor, WLED, curcumin

scholarly journals High Efficiency and Color Rendering Quantum Dots White Light Emitting Diodes Optimized by Luminescent Microspheres Incorporating

Nanophotonics ◽  
2016 ◽  
Vol 5 (4) ◽  
pp. 565-572 ◽  
Author(s):  
Wei Chen ◽  
Kai Wang ◽  
Junjie Hao ◽  
Dan Wu ◽  
Jing Qin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
White Light ◽  
High Efficiency ◽  
Lattice Structure ◽  
Light Emitting Diode ◽  
Luminescent Properties ◽  
Color Temperature ◽  
High Quantum Efficiency ◽  
Light Emitting ◽  
Color Rendering

AbstractIn this research, we have developed an approach by incorporating quantum dots (QDs) with red emission into mesoporous silica microspheres through a non-chemical process and obtained luminescent microspheres (LMS). Owing to the lattice structure of LMS, QDs were effectively protected from intrinsic aggregation in matrix and surface deterioration by encapsulant, oxygen and moisture. The LMS composite has therefore maintained large extent luminescent properties of QDs, espe-cially for the high quantum efficiency. Moreover, the fabricated white light emitting diode (WLED) utilizing LMS and YAG:Ce yellow phosphor has demonstrated excellent light performance with color coordinates around (x = 0.33, y = 0.33), correlated color temperature between 5100 and 5500 K and color rendering index of Ra = 90, R9 = 95. The luminous efficiency of the WLED has reached up to a new record of 142.5 lm/W at 20 mA. LMS provide a promising way to practically apply QDs in lightings and displays with high efficiency as well as high stability.

Phosphor-Conversion White Light Emitting Diode Using InGaN Near-Ultraviolet Chip

2007 ◽  
Vol 124-126 ◽  
pp. 499-502 ◽  
Author(s):  
Kyoung Jae Choi ◽  
Joung Kyu Park ◽  
Kyung Nam Kim ◽  
Chang Hae Kim ◽  
Ho Kun Kim
Keyword(s):  
White Light ◽  
Uv Light ◽  
Light Emitting Diode ◽  
Forward Bias ◽  
Color Temperature ◽  
Operating Voltage ◽  
Current Increase ◽  
Light Emitting ◽  
Near Ultraviolet ◽  
Yellow Region

We have synthesized a Eu2+-activated Sr3MgSi2O8 blue phosphor and (Sr,Ba)2SiO4 yellow phosphor. We fabricated a phosphor-conversion white light emitting diode(LED) using an InGaN chip that emits 400 nm near-ultraviolet(n-UV) light and phosphors that emit in the blue and yellow region. When the white LED was operated at a forward-bias current of 20 mA at room temperature(RT), the color temperature(Tcp), average color rendering(Ra), operating voltage(Vf) and luminous efficacy(ηL) were estimated to be 5800K, 72.08, 3.4V, and 7.61 lm/W, respectively. The commission International de I’Eclarirage(CIE) chromaticity coordinates obtained from the measured spectra remained almost constant during the forward-baias current increase from 0.5 mA to 60 mA.

scholarly journals Chromaticity Properties of Curcuminoids Dye Nanofibers Prepared by Electrospinning for White Light Down-Conversion

2020 ◽  
Vol 301 ◽  
pp. 77-84
Author(s):  
M. Al Shafouri ◽  
Naser Mahmoud Ahmed ◽  
Zainuriah Hassan ◽  
Munirah Abdullah Almessiere
Keyword(s):  
Methyl Methacrylate ◽  
White Light ◽  
Light Emitting Diode ◽  
Curcuma Longa ◽  
Average Diameter ◽  
Color Temperature ◽  
Light Emitting ◽  
Poly Methyl Methacrylate ◽  
Color Rendering ◽  
Down Conversion

In this study, the chromaticity properties of curcuminoids nanofibers were studied. Recent studies revealed that the nature of emitted light from curcuminoids and the poor stability which limits their illumination applications can be further improved using nanofibers and nanoparticles of curcuminoids. Motivated by this idea, we prepared some Poly(methyl methacrylate) (PMMA) integrated curcuminoids nanofibers via electrospinning. Poly(methyl methacrylate) (PMMA) were used in three types of concentration (5,10 and15wt%) which were mixed with (curcuma longa L.) powder to produce curcuminoids solution by using the centrifuge to separate the curcuminoids solution from the impurities. Different amounts of polymer solution mixed with curcuminoids (1 to 5ml) were spun by electrospinning to study its properties. The effect of annealing on samples was studied. The chromatic study of the samples and the effect of the amount and concentration of the solution were studied by pumping the samples in three different light emitting diode (LED) wavelengths (365, 390 and 445nm). The white light chromaticity coordinates (CIE), correlated color temperature (CCT) and color rendering index (CRI) were measured. The optimum CIE, CRI and CCT values of (X= 0.3051; Y= 0.3370), 64 and 6809K, respectively were obtained. By using field emission scanning electron microscope (FESEM) device, the curcuminoids nanofibers diameter was measured, where the values obtained ranged between 191 to 234nm. After the annealing process, curcuminoids nanoparticles average diameter 13-19 nm were obtained.

scholarly journals Composition and structure design of three-layered composite phosphors for high color rendering chip-on-board light-emitting diode devices

2021 ◽  
Author(s):  
Xin Liu ◽  
Xinglu Qian ◽  
Peng Zheng ◽  
Xiaopu Chen ◽  
Yagang Feng ◽  
...  
Keyword(s):  
White Light ◽  
Light Emitting Diode ◽  
Layered Composite ◽  
Structure Design ◽  
Color Temperature ◽  
Vacuum Sintering ◽  
Luminous Efficacy ◽  
Light Emitting ◽  
Composition And Structure ◽  
Color Rendering

AbstractA three-layered phosphor structure was designed and prepared by the spin coating of BaSi2N2O2:Eu (cyan-emitting) and (Sr,Ca)AlSiN3:Eu (red-emitting) phosphor films on the yellow-emitting Y3Al5O12:Ce (YAG:Ce) phosphor ceramic synthesized by the solid-state reaction under vacuum sintering. In order to achieve high color rendering lighting, the influence of the composition and structure of the three-layered phosphors on the optical, thermal, and electrical properties of the chip-on-board (COB) packaged white-light-emitting diodes (WLEDs) was studied systematically. The WLED with the structure of “red+cyan+yellow” (R+C+Y) three-layered phosphor generated neutral white light and had a luminous efficacy of 75 lm/W, the fidelity index (Rf) of 93, the gamut index (Rg) of 97, and the correlated color temperature (CCT) of 3852 K. Under the excitation of laser diode (LD), the layer-structured phosphor yielded the white light with a luminous efficacy of 120 lm/W, color rendering index (CRI) of 90, and CCT of 5988 K. The result indicates that the three-layered phosphor structure is a promising candidate to achieve high color rendering and high luminous efficacy lighting.

scholarly journals Study of the Effect of Injection Currents on White Light Emission of Ce-Doped YAG Phosphor Powder Prepared by Microwave Combustion

2020 ◽  
Vol 301 ◽  
pp. 60-68 ◽  
Author(s):  
Husnen R. Abd ◽  
Zainuriah Hassan ◽  
Naser Mahmoud Ahmed ◽  
A.F. Omar ◽  
Khai Shenn Lau ◽  
...  
Keyword(s):  
White Light ◽  
Yttrium Aluminum Garnet ◽  
Light Emission ◽  
Light Emitting Diode ◽  
Spherical Particles ◽  
Color Temperature ◽  
Phosphor Powder ◽  
Light Emitting ◽  
Microwave Combustion ◽  
Whole Process

The behaviors of yttrium aluminum garnet (YAG) phosphor powder doped by cerium (YAG:Ce3+) was studied. Here, the YAG:Ce3+ nanopowders have been synthesized using microwave combustion (MW) according to the formula, Y(3-0.04) Al5O12: 0.04Ce3+ to produce white light emitting diode (WLEDs) by conversion from blue indium gallium nitride light emitting diode (InGaN LED, 445 nm) chips; the whole process took only 20 min. Pure YAG phase was obtained after annealing at 1050 °C for 5 h with nonaggregated and spherical particles. Thermogravimetry and derivative thermogravimetry (TG/DTG), X-ray powder diffraction (XRPD), transmission electron microscope (TEM), photoluminescence (PL), electroluminescence (EL) emissions and standard CIE 1931 chromaticity diagrams have been used to characterize the samples. The highest WLEDs emission was achieved for the annealed YAG:Ce3+, together with proper color rendering index (CRI), and tunable correlated color temperature (CCT). Finally, we conclude that the decreasing EL intensity at increased injection current is caused by the thermal ionization from the 5d1 level to the conduction band.

White Light Emission from Pr, Dy Doped ZnSiCa Glass

2020 ◽  
Vol 12 (2) ◽  
pp. 154-160
Author(s):  
Pingsheng Yu ◽  
Wei Guo ◽  
Yilu Cheng ◽  
Liangbi Su ◽  
Jun Xu
Keyword(s):  
White Light ◽  
Light Emission ◽  
Light Emitting Diode ◽  
Visible Region ◽  
Color Temperature ◽  
Potential Candidate ◽  
Rare Earth Ion ◽  
Light Emitting ◽  
Light Region ◽  
Chromaticity Coordinates

Background:: Luminescence glass is a potential candidate for developing white light emitting diode (W-LED) due to its good rare earth ion solubility, efficient luminescence, easy fabrication and good mold ability. Pr3+ ion has various visible emission bands from blue to red spectral region, and has attracted considerable attention for potential application to LEDs, ultraviolet laser, and scintillator. The Dy3+ ions can exhibit emission in blue and greenish-yellow (4F9/2→6H15/2, 13/2 transitions of Dy3+) spectral regions under excitation at near UV (ultraviolet). It is possible to obtain white luminescence if Pr3+ ions and Dy3+ ions can be excited simultaneous, due to their multiple luminescence in the visible region. Methods: The Pr, Dy doped ZnSiCa glass samples were prepared by the conventional melting quenching procedure. The XRD, absorption spectra, emission spectra, and ICP-OES measurements were performed to investigate the properties of the materials. Results: The Pr and Dy co-doped ZnSiCa glasses under 443 nm excitation show emission band peaking at about 483 nm, 575 nm and 670 nm / 676 nm. The glass samples exhibit chromaticity coordinates in the white light region in the CIE 1931 diagram, with a Correlated Color Temperature (CCT) at about 7000 K. Conclusion: Pr, Dy codoped ZnSiCa glass samples show chromaticity coordinates in the white light region in the CIE 1931 diagram, with a CCT at about 7000 K. It is suggested that the Pr, Dy codoped ZnSiCa glasses might be considered as promising candidates for white light emitting sources.

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