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High color rendering index white light-emitting diode based on enviromental friendly carbon and AIZS nanoparticles
摘要： Solid-state white light-emitting diodes (WLEDs) based on carbon dots (CDs) have attracted broad attention due to their high brightness and enviromental friendly. However, the poor performance including low efficiency and weak emission of red-emitting CDs further hindered its application on WLED devices. Herein, we constructed one outstanding WLEDs device by combining carbon dots (blue emission, green emission) and Ag-In-Zn-S (AIZS) nanoparticles with red emission. Moreover, by adjusting the volume ratio of the three materials, the WLED showed maximum color rendering index (CRI) of 97 and maintained CRI value above 90 during the correlated color temperature (CCT) tuned from 3387 to 8018 K. Meanwhile, the as-fabricated WLED devices showed excellent color rendering stability during the working voltages from 3.0V to 3.5V. This work may provide one new avenue for development of low-cost, environmental friendly and high-performance CDs phosphor-based WLEDs.
关键词： AIZS nanoparticles,color rendering index,white light-emitting diode,carbon dots,environmental friendly
更新于2025-09-23 15:21:01
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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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Facile Preparation of Stable Solid-State Carbon Quantum Dots with Multi-Peak Emission
摘要： Aggregation-caused quenching (ACQ) effect, known as the main cause to restrain solid-state luminescence of carbon quantum dots (CQDs), hinders further application of CQDs in white light-emitting diodes (WLED). Here, a complex of CQDs and phthalimide crystals (CQDs/PC) was prepared through a one-step solvothermal method. CQDs/PC prevented CQDs from touching directly by embedding the CQDs in phthalimide crystal matrix in situ, which effectively reduced the ACQ effect. Furthermore, CQDs/PC exhibited multi-peak fluorescence spectra that span the green, yellow and orange spectral regions. Finally, a WLED fabricated based on CQDs/PC achieved a color-rendering index of 82 and a correlated color temperature of 5430 K. This work provides a quick and effective strategy to apply CQDs to WLED.
关键词： solid-state luminescence,multi-peak emission,yellow carbon quantum dots,white light-emitting diode
更新于2025-09-19 17:13:59
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Closing the Cyan-Gap toward Full Spectrum LED Lighting with NaMgBO3:Ce3+
摘要： The photoluminescence spectrum generated by an ordinary phosphor-converted white light-emitting diode (pc-wLED) that combines a blue LED chip with a yellow phosphor or a near-UV LED with red, green and blue phosphors contains a notable cavity in the cyan region of the visible spectrum (480-520 nm) that reduces the color quality produced by these lights. Here, we report a new bright blue-cyan-emitting phosphor, NaMgBO3:Ce3+, that bridges the gap. Rietveld refinements verify the rare-earth substitution while ab initio calculations prove Ce3+ occupies the Na+ sites. NaMgBO3:Ce3+ is excited by a broad range of near-UV light sources and produces a blue-cyan emission with a high (internal) quantum efficiency, minimal thermal degradation, and zero-chromaticity drift at elevated temperatures. Fabricating a near-UV (λex = 370 nm) pumped pc-wLED using NaMgBO3:Ce3+ along with commercially available phosphors demonstrates a well-distributed warm white light with a high color-rendering index (Ra) of 91 and a low correlated color temperature (CCT) of 3645 K. Closing the cyan cavity with NaMgBO3:Ce3+ is ideal for generating a pleasant, full-spectrum, warm white light.
关键词： full-spectrum LED lighting,NaMgBO3:Ce3+,blue-cyan-emitting phosphor,color-rendering index,phosphor-converted white light-emitting diode
更新于2025-09-12 10:27:22
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Luminescent properties of CaSc2O4:Ce3+ green phosphor for white LED and its optical simulation
摘要： Green-emissive Ce3t-doped CaSc2O4 phosphors were synthesized by solid-state method. The water washing process of the as-prepared samples was several times conducted because of severe hydration of unreacted CaO and CaF2 flux residual. The washed CaSc2O4:Ce3t phosphors showed a single phase with a crystallite size of 1–3 μm, and its photoluminescence intensity was 10% improved compared with the as-prepared. It shows the broad 450 nm excitation peak and the green emission peak at 520 nm with a half width of 105 nm. Its temperature dependence showed the similar thermal stability with a commercial silicate phosphor. The optical simulation and the real fabrication of white LEDs with a combination of our green phosphor and one of possible orange-red phosphors demonstrated that the white LED with Sr3SiO5:Eu2t orange phosphor gives the best luminous efficacy and the appropriate color rendering index of 70 under the daylight color temperature of 6400 K.
关键词： CaSc2O4:Ce3t,White-light-emitting diode,Optical simulation,Photoluminescence,Green emission
更新于2025-09-12 10:27:22
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Dopant-Free Squaraine-Based Polymeric Hole-Transporting Materials with Comprehensive Passivation Effects for Efficient All-Inorganic Perovskite Solar Cells
摘要： Quantum-dot (QD) white light-emitting diodes (LEDs) are promising for illumination and display applications due to their excellent color quality. Although they have a high quantum yield close to unity, the reabsorption of QD light leads to high conversion loss, significantly reducing the luminous efficacy and stability of QD white LEDs. In this report, SBA-15 mesoporous particles (MPs) with two-dimensional hexagonal pore structures (2D-HPS) are utilized to largely enhance the luminous efficacy and color-conversion efficiency of QD white LEDs in excess of 50%. The reduction in conversion loss also helps QD white LEDs to achieve a lifetime 1.9 times longer than that of LEDs using QD-only composites at harsh aging conditions. Simulation and testing results suggest that the waveguide effect of 2D-HPS helps in reducing the reabsorption loss by constraining the QD light inside the wall of 2D-HPS, decreasing the probability of being captured by QDs inside the hole of 2D-HPS. As such, materials and mechanisms like SBA-15 MPs with 2D-HPS could provide a new path to improve the photon management of QD light, comprehensively enhancing the performances of QD white LEDs.
关键词： stability,two-dimensional hexagonal pore structure,reabsorption,luminous efficacy,SBA-15 mesoporous particle,quantum-dot white light-emitting diode
更新于2025-09-11 14:15:04
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Optical and structural properties of Curcuminoids Extracted from Curcuma longa L. for hybrid white light diode
摘要： In this study, curcuminoids were extracted from turmeric (Curcuma longa L.) by means of three methods, comprising the normal method, use of Soxhlet apparatus and by combining the normal method with the Soxhlet extraction approach. The limitation of stickiness in the use of curcuminoids was resolved by mixing it with silica gel. The curcuminoids used light down-conversion of UV light (390 nm) for the white light-emitting diode (WLED). The characteristics of the white light chromaticity were controlled by changing the current and concentration of the curcuminoids. The chromaticity coordinates (CIE) and correlated color temperature (CCT) were measured for different applied currents (20, 60 and 100 mA) and weights (25, 35 and 50 mg) of curcuminoids. It was observed from the concentration of phosphor that the combination of the normal and Soxhlet apparatus methods is most effective extraction approach. The results showed that increasing the concentration of phosphor signi?cantly and remarkably increased the value of CCT when different values of current were applied. The stress test showed that the prolongation of dye degradation can be improved using air gap and glass slid, with air gap being more effective. An optimum color rendering index (CRI) value of 61.2 is obtained. The white phosphor exhibited CIE values of 0.333, 0.3151 and color temperature (CCT) of 5405 K.
关键词： white light-emitting diode,turmeric,curcuminoids,correlated color temperature,chromaticity coordinates
更新于2025-09-10 09:29:36
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Mn <sup>4+</sup> -Doped Heterodialkaline Fluorogermanate Red Phosphor with High Quantum Yield and Spectral Luminous Efficacy for Warm-White-Light-Emitting Device Application
摘要： Narrow band red-emitting Mn4+-doped fluoride phosphor is an essential red component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as a result of the lowest symmetry. It has higher quantum yield than Na2GeF6:Mn4+ and higher spectral luminous efficacy than Cs2GeF6:Mn4+. Given the good thermal stability and efficient luminescence, a prototype warm-WLED device with a color rendering index of 92.5, a correlated color temperature of 3783 K, and a luminous efficacy of 176.3 lm/W has been fabricated by employing the CsNaGeF6:Mn4+ phosphor as the red component. Our results not only reveal that a high-performance Mn4+ red phosphor is achieved through cationic substitutions but also construct a relationship of performance?structure to guide the design of Mn4+ phosphors in the future.
关键词： quantum yield,spectral luminous efficacy,Mn4+-doped fluoride phosphor,warm-white-light-emitting diode,heterodialkaline fluorogermanate
更新于2025-09-09 09:28:46
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Structural and optical properties of highly thermally active Gd2Zr2O7:Dy3+ phosphors for lighting applications
摘要： Near white light emitting (Gd2?2x Dy2x Zr2O7) (2x = 0.01, 0.02, 0.04, 0.06, 0.08) phosphors have been synthesized by the facile hydrothermal method. To examine the structural and optical properties, the prepared phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence spectroscopy (PL) and UV–Vis diffuse reflectance spectroscopy. The XRD results confirm the defect fluorite structure of the prepared phosphors having cubic crystal system with space group Fm3m and incorporation of Dy3+ ions does not modify host lattice crystal structure. The photoluminescence properties have been well studied in respect of excitation spectra, emission spectra and decay kinetics. The PL emission spectra of the sample under 351 nm UV excitation exhibits two intense peaks around 484 nm and 580 nm which are attributed to the transitions 4F9/2–6H15/2 and 4F9/2–6H13/2, respectively of Dy3+ ion. The emission intensity goes on increasing until Dy3+ doping concentration reaches at 2 mol% and intensity decreases thereafter on higher concentration. The average life times are found to decrease with the increase of Dy3+ concentration. Photometric studies such as CIE color coordinate, CCT and Color purity facilitate that the reported phosphors can generate near white light emission. Temperature dependent PL spectral measurement reveals that the emission intensity as well as the life time gradually increases with temperature. Thus, the affirmative experimental result indicates that the Dy3+ ions doped Gd2Zr2O7 phosphors can be used as active near white lighting emitting phosphor materials.
关键词： white light emitting diode,Gd2Zr2O7:Dy3+,photoluminescence,phosphors,hydrothermal method
更新于2025-09-04 15:30:14