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S, N-codoped Oil-soluble Fluorescent Carbon Dots for High Color-rendering WLED
摘要： Carbon dots (CDs) have attracted widespread attention in light-emitting-diode (LED) applications owing to their environmental friendliness, easy processing and unique optical properties. For the practical use of CDs in LEDs, the controllable synthesis of high performance oil-soluble carbon dots are still in urgent demand. In this study, S, N-codoped oil-soluble carbon dots (S, N-OCDs) with average size of 3.38 nm were prepared by solvothermal reaction of acetone, dimethyl trithiocarbonate (DMTTC) and nitric acid. Characterization results reveal that both the conjugated aromatic π systems from aldol condensation and highly active free radicals from DMTTC essentially dominate the development of this yellow-green emitting S, N-OCDs which possess high carbonization, quantum yield (21.08 %) and oil-solubility. Furthermore, a white light-emitting-diode (WLED) was fabricated through mixing the obtained S, N-OCDs and epoxy and drop-casting the mixure on the surface of gallium nitride (GaN) based blue chips. The as-prepared WLED showed excellent color rendering properties (CCT of 5389 K, CIE coordinates of (0.33,0.30), CRI of 88.38).
关键词： oil-soluble carbon dots,color rendering index,WLED,heteroatom doping
更新于2025-11-19 16:46:39
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Preparation and characterization of bismuth oxychloride/reduced graphene oxide for photocatalytic degradation of rhodamine B under white-light light-emitting-diode and sunlight irradiation
摘要： Facile and template-free two-step synthesis of bismuth oxychloride/graphene oxide (BiOCl/GO) and bismuth oxychloride/reduced graphene oxide (BiOCl/rGO) photocatalysts for degradation of rhodamine B (RhB) under low-power white light–emitting diode (wLED) irradiation (1.6 W/cm2) and sunlight is demonstrated. These photocatalysts were characterized by transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray di?raction, and micro-Raman, Fourier-transform infrared, X-ray photoelectron, and UV–Vis di?use re?ectance spectroscopy. Under wLED irradiation, the prepared BiOCl/rGO photocatalysts exhibited excellent photodegradation activity toward RhB through chromophore cleavage mechanism and toward phenol in the presence of RhB with notable dye-sensitized e?ect. Through scavenging experiments, superoxide radicals were notably involved in RhB degradation. With the highest charge separation e?ciency and lowest recombination rate, the photocatalytic activity of BiOCl/rGO reached a maximum rate constant of 0.1899 min?1, 2.0 and 3.0 times higher than those of BiOCl/GO and BiOCl, respectively. In the stability study, only a slight loss (4.5%) in photodegradation was observed after BiOCl/rGO was used in ?ve cycles of photodegradation runs. Compared with commonly used photocatalyst such as TiO2 (P25), BiOCl/rGO demonstrated superior photocatalytic activity and stability under wLED irradiation for various dyestu?s (rhodamine 6 G, methylene blue, and fast green FCF) in di?erent environmental water samples (lake, pond, and sea water).
关键词： wLED-induced photodegradation,Rhodamine B,Reduced graphene oxide,Phenol,Sunlight irradiation,Bismuth oxychloride
更新于2025-09-19 17:15:36
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Spectroscopic investigation of red Eu3+ doped ceria nanophosphors and promising color rendition for warm white LEDs
摘要： Europium-ion doped CeO2 phosphors with different Eu3+ concentrations were synthesized via sol-gel combustion synthesis. X-ray diffraction patterns revealed the formation of pure cubic structure of CeO2 even after the incorporation of 35 mol% Eu3+. The excitation spectra of CeO2:Eu3+ displayed a broad band (330- 370 nm) and several sharp peaks (393- 532 nm) owing to the charge transfer (CT) from O2- to Ce4+ ions and f-f transitions of Eu3+ ions respectively. The evaluation of CT band was explained on the basis of environmental factors. The phosphors were illuminated with blue light and showed the characteristic red luminescence corresponding to the 5D0→ 7FJ transitions of Eu3+ as confirmed from XPS. The emission was observed to increase with the increase in the Eu3+ concentration upto 35 mol% without any quenching. Judd-Ofelt parameters were evaluated using the emission spectroscopy to explain the variation in ligand environment and enhancement of red color purity to 80%. The thermal stability of present phosphors was measured by estimating activation energy and TG-DSC analysis. Robust blue-excitation and sharp red-emission with high color-purity and promising thermal stability in fabricated WLEDs indicated the suitability of CeO2:Eu3+ phosphors for white light emitting diodes with quantum yield efficiency up to 84.6%.
关键词： color purity,sol-gel assisted combustion,photoluminescence,WLED,charge transfer
更新于2025-09-19 17:13:59
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AIP Conference Proceedings [AIP Publishing DAE SOLID STATE PHYSICS SYMPOSIUM 2018 - Hisar, Haryana, India (18–22 December 2018)] DAE SOLID STATE PHYSICS SYMPOSIUM 2018 - Mixed fuel approach for the fabrication of TiO2:Dy3+(1-11?mol%) nanophosphors: Applications towards wLED and latent finger print detection
摘要： The pure and Dy3+(1-11 mol%) ions doped TiO2 nanophosphors (NPs) were prepared by solution combustion method using grouping of fuels; glycine and ammonium acetate. PXRD studies establishes that the pure and doped samples show rutile and anatase phases respectively. The Raman spectra illustrates that the absorption peaks noticed at ～ 142, 446 and 609 cm-1 were due to the active vibrational optical phonon modes pertaining to B1g, Eg and A1g respectively of the pure tetragonal rutile phase, whereas the peaks at ～ 395, 513 and 639 cm-1 were attributed due the active modes B1g, A1g and Eg respectively of anatase phase of TiO2. The active mode observed at ～ 142 cm-1 was a characteristic mode whereas the mode at ～ 229 cm-1 was attained due to second order effect [SOE] of pure rutile phase of TiO2. The Raman studies validate the PXRD studies. The CIE and CCT outcomes show that NPs can be used for wLED and household applications. The optimized product TiO2:Dy3+(9 mol% ) was utilized for the visualization of latent finger prints (LFPs). The results reveal that, all the levels (I to III) of ridge feature were clearly visualized under normal light indicating that the powder was a reliable and promising labeling agent for LFPs.
关键词： TiO2:Dy3+,latent finger print detection,wLED,solution combustion method,nanophosphors
更新于2025-09-19 17:13:59
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Yellow/Orange-Emitting ABZn2Ga2O7:Bi3+ (A = Ca, Sr; B = Ba, Sr) Phosphors: Optical Temperature Sensing and WLED Applications
摘要： Recently, there is growing interest in developing Bi3+-activated luminescence materials for optoelectronic applications. Herein, new yellow/orange-emitting ABZn2Ga2O7:Bi3+ (ABZGO, A = Ca, Sr; B = Ba, Sr) phosphors with tunable optical properties are synthesized by alkaline earth cation substitution. When Sr2+ substitutes Ca2+ and Ba2+, the excitation wavelength has a red shift from 325 to 363 nm, matching well with the n-UV chips based WLEDs. CaBaZn2Ga2O7:0.01Bi3+ (CBZGO:0.01Bi3+) exhibits two evident emission peaks at 570 and 393 nm originating from the respective occupation of Ca and Ba sites by Bi3+ ions. The optical tuning of CBZGO:Bi3+ phosphor is achieved by changing Bi3+ doping content and excitation wavelength based on the selected site occupation. Differently, both SrBaZn2Ga2O7:0.01Bi3+ (SBZGO:0.01Bi3+) and Sr2Zn2Ga2O7:0.01Bi3+ (SZGO:0.01Bi3+) phosphors exhibit a single broad emission band, peaking at 600 and 577 nm, respectively. Two different Bi3+ sites are also verified respectively in SBZGO and SZGO hosts by the Gaussian fitting of the asymmetric PL spectra and lifetime analysis. The different luminescence behaviors of ABZGO:0.01Bi3+ phosphors should be ascribed to the synergistic effect of centroid shift, crystal-field splitting and Stokes shift. Moreover, the temperature-dependent PL spectra reveal that cation substitutions of Sr2+ for Ca2+ and Ba2+ can efficiently improve the thermal stability of ABZGO:0.01Bi3+ phosphors. In view of different thermal responses to various temperature for two emission peaks of CBZGO:0.01Bi3+ phosphor, an optical thermometer is designed and has a good relative sensitivity (Sr = 1.453% K-1) at 298 K. Finally, a WLED with CRI = 97.9 and CCT = 3932 K is obtained by combining SZGO:0.01Bi3+ and BAM:Eu2+ phosphors with a 370 nm n-UV chip, demonstrating that SZGO:0.01Bi3+ is an excellent yellow-orange-emitting phosphor for n-UV WLED devices. This work stimulates the exploration of optical tuning by cation substitution to obtain remarkable luminescence materials for optical temperature sensing and WLED applications.
关键词： optical temperature sensing,WLED applications,optical tuning,Bi3+-activated,thermal stability,luminescence materials
更新于2025-09-19 17:13:59
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Ca(Mg <sub/>0.8</sub> Al <sub/>0.2</sub> )(Si <sub/>1.8</sub> Al <sub/>0.2</sub> )O <sub/>6</sub> :Ce <sup>3+</sup> ,Tb <sup>3+</sup> Phosphors: Structure Control, Density-Functional Theory Calculation, and Luminescence Property for pc-wLED Application
摘要： A modified structure Ca(Mg0.8Al0.2)(Si1.8Al0.2)O6 (denoted as CMASO) from the evolution of CaMgSi2O6 (denoted as CMSO) codoped with Ce3+ and Tb3+ ions was designed successfully by solid reaction method for application in phosphor-converted white-light-emitting diode (pc-wLED). The Rietveld refinement of these two structures verified the changes derived from the replacement of some of the Mg2+ and Si4+ ions by Al3+ ions. The band gaps were calculated by density-functional theory (DFT) calculation method to verify the change of Al3+ ions replacing further, and the diffuse reflectance spectra (DRS) proved the veracity of the calculation result. The phosphors CMASO:Ce3+ showed blue emission excited by a wider excitation wavelength from 280 nm to 370 nm. The change of structure lead to the absorbable range broaden and the emission peak shifted to longer wavelength, compared with CMSO:Ce3+, although the amount of emitting center was the same. The reason for these phenomena was discussed in detail. The codoped phosphors CMASO:Ce3+,Tb3+ exhibited different emission colors from blue to green as the concentration of Tb3+ ions increased. Combined with commercial red phosphor CaAlSiN3:Eu2+ and ultraviolet LED (UV-LED) chips, the selected appropriate samples achieved white emission. The correlated color temperature (CCT) was 6137 K and the color rendering index (Ra) was 80.5, indicating that they could act as potential phosphors for possible applications in pc-wLED.
关键词： Ce3+,pc-wLED,DFT,luminescence property,Tb3+,Ca(Mg0.8Al0.2)(Si1.8Al0.2)O6,phosphor-converted white-light-emitting diode,density-functional theory
更新于2025-09-19 17:13:59
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Nanocrystalline structure control and tunable luminescent mechanism of Eu-doped CsPbBr3 quantum dots glass for WLED
摘要： As CsPbX3(Cl, Br, I) perovskite quantum dot glass has been widely reported, the discovery of next-generation perovskite luminescent materials has been challenged by doping rare earth activators with energy-level transition. In this work, we report a novel Eu-doped quantum dots glass material with tunable luminescence properties. The structure characteristic and tunable luminescent mechanism were investigated by combining X-ray diffraction, X-ray photoelectric spectroscopy, excitation and emission spectra. It is found that Eu ions replaced the lattice of Pb in CsPbBr3 quantum dots and formed CsEuBr3 quantum dots, which result in a blue emission. Meanwhile, a green emission comes from CsPbBr3 quantum dots, and a red emission originally comes from Eu3+ in glass matrix can also be observed by controlling the heat treatment temperature. A light-emitting diode is designed based on the prepared Eu doped quantum dots glass without doping any phosphors, and a warm-light with CCT at 4075k is obtained. The present work provides a new luminescence tunable design principle of europium doped quantum dots glass materials and could bring inspiration to the future exploration of rare earth ion-doped quantum dot glass material in the future.
关键词： WLED,CsEuBr3,tunable luminescence,Eu-doped,CsPbBr3,perovskite quantum dot glass
更新于2025-09-19 17:13:59
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Fabrication and analysis of PiG-based LEDs with WO3-doped TeO2-based glass
摘要： Phosphor-converted white light-emitting diodes (pc-WLEDs) were fabricated using low-melting-temperature TeO2-based glass powders, which are a potential packaging material. The novel glass component, TeO2-B2O3-ZnO-Na2O doped with WO3, showed a high transmittance of above 80% and had a refractive index (1.83) that matched that of the phosphors well. Warm pc-WLEDs were fabricated using a 460-nm blue chip combined with YAG:Ce3+ yellow phosphors, Li2MgTiO4:Mn4+, Hf4+ red phosphors, and TeO2-based glass powders or silicone. The differences between phosphor-in-glass (PiG) and phosphor-in-silicone (PiS) pc-WLEDs are reported in detail. Based on a long-term heating test, color deviations, correlated color temperatures (CCTs), and the color rendering index (CRI), the PiG-based pc-WLEDs showed excellent stability and less deviation in terms of the CIE coordinates as compared to the PiS-based pc-WLEDs. The luminescence efficiency, CCT, and CRI of the optimized PiG-based pc-WLED were 41.32 lm/W, 4570 K, and 83.31, respectively, making this pc-WLED a good candidate for pc-WLED applications.
关键词： Phosphor-in-glass,pc-WLED
更新于2025-09-16 10:30:52
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Insight into a Novel Garnet-based Yellowish-green Phosphor: Structure, Luminescence Properties and Application for Warm White Light-emitting Diodes
摘要： White light-emitting diodes (WLEDs) have been considered as the next generation lighting technology due to its advantages such as high efficiency and environmental friendliness. However, current mainstream WLEDs, which is based on blue chip and Y3Al5O12:Ce3+ yellow phosphor, suffer from the problem of low color rendering index (CRI). To solve this problem, a yellowish-green phosphor Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ (CYAS:Ce3+) based on garnet structure has been designed in this study. The crystal structure, band structure, luminescence properties have been investigated in detail. The CYAS:Ce3+ exhibits efficient and thermal-stable yellowish-green emission. The 5d centroid shift and crystal splitting of Ce3+ ion in CYAS has been analyzed together with the structure. Moreover, good warm white light with low correlated color temperature (3210 K),high color render index (85.1) and luminous efficacy (88.5 lm/W) has been obtained by combing the CYAS:Ce3+, red phosphor CaAlSiN3:Eu2+ with blue LED chip.
关键词： Garnet,WLED,Luminescence,Phosphor
更新于2025-09-11 14:15:04
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[IEEE 2019 54th International Universities Power Engineering Conference (UPEC) - Bucharest, Romania (2019.9.3-2019.9.6)] 2019 54th International Universities Power Engineering Conference (UPEC) - Harmonic Behaviour of RGB WLED
摘要： For the last few years, there has been a decrease in electricity consumption for lighting purposes. The reason for this decrease is the widespread use of energy saving lighting elements that have high efficacy factor. LEDs are one of these lighting elements and have a very important role on energy saving lighting. On the other hand, power quality problems have started to be experienced more frequently and seriously, so it has become an important issue nowadays. Light emitting diodes are a closely related in both subjects. In this study, the harmonic behavior of RGB WLEDs, which has gained importance recently and has become increasingly widespread, has been investigated. RGB WLEDs, which are quite different from monochrome LEDs in terms of package contents and driver circuit, are expected to behave differently in terms of harmonics. In order to observe that, an appropriate test setup has been established and the power quality measurements of an RBG WLED sample have been performed for different operating cases. In the conclusion of the study, the enlightening results about the harmonic behavior of RGB WLEDs were obtained.
关键词： RGB WLED,Light emitting diodes,Distortion measurement,Relative spectral power,Power conversion harmonics
更新于2025-09-11 14:15:04