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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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Novel ultra-stable and highly luminescent white light-emitting diodes from perovskite quantum dots—Polymer nanofibers through biaxial electrospinning
摘要： Cesium lead halide perovskite quantum dots (QDs) have drawn extensive attention due to their excellent optical properties. However, their use is limited by poor stability. To enhance their stability, we electrospun perovskite-embedded fibers from composite CsPbX3 (X = Cl, Br, and I) perovskite QDs, blending with three polymers, poly(styrene-butadiene-styrene) (SBS), poly(methyl methacrylate) (PMMA), or polystyrene (PS), for the light-emitting diode (LED) applications. We found that the stretchable CsPbBr3@SBS fibers revealed the highest photoluminescence quantum yield, the CsPbBr3@PMMA fibers demonstrated a high thermal stability, and the CsPbBr3@PS fibers exhibited the best water-resistant stability. The photoluminescence intensity maintained 83% of its initial intensity for more than 3 months in water. Furthermore, the LED devices are manufactured from the blue chips and packaged with the core/shell red and green perovskite-based fibers by using biaxial electrospinning exhibited stable and highly efficient white luminescence. The luminance and efficiency are higher than 400% of the values of multilayered structures.
关键词： biaxial electrospinning,luminescence,stability,white light-emitting diodes,polymer nanofibers,perovskite quantum dots
更新于2025-09-11 14:15:04
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White LEDs With High Optical Consistency Packaged Using 3D Ceramic Substrate
摘要： Packaging efficiency and optical performances are important indexes for white light-emitting diodes (WLEDs) packaging. In this letter, wafer-level WLEDs packaging were presented by printing phosphor on three-dimensional (3D) ceramic substrate to improve packaging efficiency and optical consistency. The 3D ceramic substrate was prepared by repeatedly electroplating copper cups on the planar direct plated copper (DPC) ceramic substrate. The phosphor concentration was adjusted to realize natural white light. The fabrication errors of the 3D ceramic substrate and the optical performances of WLED modules were analyzed to evaluate the optical consistency of the WLED modules packaged by using 3D ceramic substrate. Consequently, the fabrication errors of 3D ceramic substrate are less than 1%. When the phosphor concentration was set at 12.5 wt%, the packaged LEDs achieve a natural white light with luminous efficiency (LE) of 94.55 lm/W, correlated color temperature (CCT) of 5915 K, and chromaticity coordinate of (0.3166, 0.3345). The WLED modules exhibit small standard deviations in LE (1%), color rendering index (1%), correlated color temperature (98 K), and high reliability. The results indicate that the WLEDs packaged using 3D ceramic substrate have excellent optical consistency.
关键词： direct plated copper (DPC) ceramic substrate,optical performance,White light-emitting diodes (WLEDs),LED packaging,reliability
更新于2025-09-11 14:15:04
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Designing High‐Performance LED Phosphors by Controlling the Phase Stability via a Heterovalent Substitution Strategy
摘要： Phosphor-converted white light-emitting diodes (LEDs) are currently playing key roles in the lighting and display industries and trigger urgent demands for the discovery of “good” phosphors with high quantum efficiency, improved thermal stability, and controllable excitation/emission properties. Herein, a general and efficient heterovalent substitution strategy is demonstrated in K2HfSi3O9:Eu2+ achieved by Ln3+ (Ln = Gd, Tb, Dy, Tm, Yb, and Lu) doping to optimize luminescence properties, and as an example, the Lu3+ substitution leads to improvement of emission intensity and thermal stability, as well as tunable emission color from blue to cyan. The structural stability and Eu2+ occupation via Lu3+ doping have been revealed by the structural elaboration and density functional theory calculations, respectively. It is shown that heterovalent substitution allows predictive control of site preference of luminescent centers and therefore provides a new method to optimize the solid-state phosphors for LEDs.
关键词： phosphors,photoluminescence,white light-emitting diodes
更新于2025-09-11 14:15:04
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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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Sonochemical Synthesis of Carbon Dots/Lanthanoid MOFs Hybrids for White Light-Emitting Diodes with High Color Rendering
摘要： Although lanthanoid metal-organic frameworks (Ln-MOFs) have been widely developed for white light-emitting diodes (WLEDs), the color rendering index (CRI) values are still lower than 80. To overcome this limitation, a series of carbon dots/Ln-MOFs hybrids namely CDs-2@Ln-MOF, CDs-3@Ln-MOF and CDs-4@Ln-MOF containing blue emitting CDs and yellow emitting bimetallic [(Eu1.22Tb0.78(1,4-phda)3(H2O)](H2O)2 were prepared via sonication at room temperature to restrict the self-quenching of CDs in composite materials. The as-synthesized composite materials were investigated by FT-IR, PXRD, TEM, SEM and photoluminescence. The luminescent color of the materials can be adjusted by varying the amount of CDs and excitation wavelengths. The resulting CDs-3@Ln-MOF achieved excellent CRI up to 93 with the ideal CIE coordinate (0.334, 0.334) and appropriate correlated color temperature, CCT (5443 K). In addition, the tunable multi-colored luminescence based on single and bimetallic EuxTb2-x(1,4-phda)3(H2O)](H2O)2; x = 0, 0.73, 1.22, 1.57, 1.94 and 2 were applied as the luminescent security inks for anti-counterfeiting application through encoding/decoding and rewritable data.
关键词： anti-counterfeiting,luminescence material,white light-emitting diodes,metal-organic frameworks,carbon dots
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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One-step hydrothermal synthesis of carbon dots-polymer composites with solid-state photoluminescence
摘要： Carbon dots (CDs) and CDs-polymer composites were one-step synthesized in a hydrothermal process using hexamethylenetetramine and polycarbonate as precursors. Their optical properties and the application as solid-state phosphors towards white light-emitting diodes (LEDs) were thoroughly investigated. CDs solutions exhibit strong yellow emission under blue illumination and possess excitation-independent luminescent behavior. Owing to precursor polymerization, CDs-polymer composites were synthesized in one step. The dried CDs-polymer composite powders exhibit excellent optical stability and no luminescence quenching was observed. Under light blue illumination, the powders show broad yellow luminescence with the peak wavelength centered at 550 nm and PL quantum yield of 14.86%. For their practical applications, stable white light emission was demonstrated by coating a 455nm blue LED with the powders. Our research offers a valuable reference for growing CDs-polymer composites in a facile, low-cost and low-temperature hydrothermal process and developing white LEDs with light blue LEDs and metal-free phosphors.
关键词： white light-emitting diodes (LEDs),phosphors,solid-state photoluminescence,hydrothermal method,carbon materials,luminescence
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