- 标题
- 摘要
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- 实验方案
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Al2O3-Ce:GdYAG composite ceramic phosphors for high-power white light-emitting-diode applications
摘要： In order to meet the increasing demand of high-power light-emitting-diode (LED) lighting, state-of-the-art white light-emitting diode technology needs phosphors with high thermal conductivity and high luminous efficacy as color converters. In this work, translucent Al2O3-Ce:GdYAG composite phosphors were prepared by solid-state reactive sintering. The microstructure shows that the Al2O3 particles are uniformly dispersed in the Ce:GdYAG matrix. These particles can not only improve the thermal conductivity of the ceramics, but also promote the extraction efficacy. The luminous characteristics of the Ce:GdYAG and Al2O3-Ce:GdYAG ceramics were analyzed after being packaged with blue LED. When the molar ratio of Al2O3/Ce:GdYAG is 0.8, a high luminous efficacy value of 112.6 lm/W is achieved by the Al2O3-Ce:GdYAG composite ceramic phosphor with the thickness of 0.4 mm, as well as the highest CRI valve of 71.4. The appropriate photoelectric properties of this kind of ceramic phosphor make it a promising candidate for high-power LED device.
关键词： luminous efficacy,white-LED,color coordinates,composite ceramic phosphors,Al2O3-Ce:GdYAG
更新于2025-09-19 17:15:36
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Optimization of a spectrally tunable daylight simulator using four quantum dot light‐emitting diodes for visual appraisal of color
摘要： An optimization model for luminous efficacy of a spectrally tunable light-emitting diode (LED) daylight simulator under constraint of metamerism index was developed. It was first reported that the optimal spectrally tunable LED daylight simulator of AA grade for D50, D55, D65, and D75 standard illuminants could consist of two quantum dot-integrated LEDs (QDLEDs) with the ultraviolet chip and two other QDLEDs with the blue chip. The optimized spectral parameters of each QDLED, as well as photometric and colorimetric performances of D50, D55, D65, and D75 daylight simulators, were obtained by maximizing luminous efficacy under the metamerism index for both a visible and ultraviolet range less than 0.25. The limit luminous efficacies of four daylight simulators using four QDLEDs under the ideal case will reach 181 lm/W to 205 lm/luminous efficacies with a radiant efficiency of both the ultraviolet and blue chips of 60%, as well as a quantum efficiency of a quantum dots layer of 90%, will reach 100 lm/W to 112 lm/W.
关键词： daylight simulator,metamerism index,optimization,luminous efficacy,quantum dot LED
更新于2025-09-19 17:13:59
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A poly(urethane)-encapsulated benzo[2,3- <i>d</i> :6,7- <i>d</i> a?2]diimidazole organic down-converter for green hybrid LEDs
摘要： The development of organic down-converting materials continues to attract attention in hybrid LED technology by obviating the need for non-sustainable rare-earth elements. In this work, a benzodiimidazole-based system (TPA-BDI) has been employed as a down-converting layer in a hybrid organic–inorganic LED device. A commercially available poly(urethane)-based resin is used as the encapsulating material, providing a dilute layer of TPA-BDI that is deposited on top of the GaN-based LED. Crucially, the solution-state emissive performance is generally maintained when encapsulated at low concentrations within this resin. A maximum luminous efficacy of 87 lm W?1 was demonstrated using a 1.0 mg ml?1 concentration of TPA-BDI in the resin. The suitability of using organic down-converters to produce green light from hybrid devices was demonstrated by the excellent repeatability of the device characteristics across a series of encapsulated LEDs.
关键词： poly(urethane)-based resin,hybrid LED technology,luminous efficacy,benzodiimidazole-based system,GaN-based LED,organic down-converting materials
更新于2025-09-19 17:13:59
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[IEEE 2019 3rd International Conference on Trends in Electronics and Informatics (ICOEI) - Tirunelveli, India (2019.4.23-2019.4.25)] 2019 3rd International Conference on Trends in Electronics and Informatics (ICOEI) - Performance analysis of LEDs in MIMO-OFDM based VLC indoor communication
摘要： The combination of Visible Light Communication (VLC) and Multiple-Input Multiple-Output (MIMO) is used for high-data-rate indoor wireless communications. Because the traditional RF communication systems are not capable of satisfying the growing wireless communication systems. The dual function of light-emitting diodes (LEDs), such as illumination and communication to evaluate while implementing MIMO-VLC system. The LED-based VLC system has several advantages such as security, cost-effectiveness and lack of interference. In this work, the VLC system is used in an indoor environment. The LED lamps are placed at the ceiling to provide ambient light which offers rich spatial resources for VLC. Here, various LEDs such as phosphor-converted led, organic led, micro led, RGB led and white led are used and the performance of LEDs are analyzed. The type of receiver used in the MIMO VLC system is Avalanche Photodiode Detector (APD). The performance of LED is analyzed by luminous flux, luminous efficacy, switching time, data rate and brightness.
关键词： luminous efficacy,Visible light communication,multiple-input multiple-output,data rate,light-emitting diodes
更新于2025-09-12 10:27:22
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Design of highly efficient phosphor-converted white light-emitting diodes with color rendering indices (R1 ? R15) ≥ 95 for artificial lighting
摘要： Phosphor-converted white light-emitting diodes (pc-WLEDs) are excellent energy-efficient light sources for artificial lighting applications. One goal of artificial lighting is to make objects/images look natural – as they look under the sunlight. The ability of a light source to accurately render the natural color of an object is gauged by the parameter – color rendering index (CRI). A conventional pc-WLED has an average CRI ~ 80, which is very low for accurate color reproduction. To utilize the pc-WLEDs for artificial lighting applications, all the CRI points (R1 – R15) should be above 95. However, there is a trade-off between CRI and luminous efficacy (LER), and it is challenging to increase both CRI and LER. Herein we propose a novel LED package (PKG) design to achieve CRI points ≥95 and efficiency ~100 lm/W by introducing two blue LEDs and a UV LED in combination with green and red phosphors. The silicone encapsulant, the current through the LEDs, and the green/red phosphor ratio were optimized for achieving high CRI and LER. Our re-designed LED PKG will find applications in stadium lighting as well as for ultra-high-definition television production where high CRI points are required for the artificial light source.
关键词： artificial lighting,phosphor-converted white light-emitting diodes,color rendering index,luminous efficacy,LED package design
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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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