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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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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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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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Facile synthesis, morphology and tunable photoluminescence properties of BaMgF <sub/>4</sub> :Ce <sup>3+</sup> /Tb <sup>3+</sup> /Eu <sup>3+</sup> phosphors
摘要： A series of BaMgF4:Ce3+/Tb3+/Eu3+ phosphors were successfully prepared via a facile hydrothermal process. X-ray diffraction (XRD), energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), n-UV–UV-vis photoluminescence (PL) and fluorescence decays were employed to investigate the structure, composition, morphology, luminescence properties and energy transfer processes. The as-prepared BaMgF4 phosphors exhibit a rod-like morphology and the size of the product can be effectively regulated by changing the amount of NH4F in the original solution. Under n-UV–UV light excitation, the Ce3+, Tb3+ and Eu3+ singly-doped BaMgF4 phosphors all show good characteristic luminescence; the Ce3+–Tb3+ and Tb3+–Eu3+ co-doped BaMgF4 phosphors both show tunable emission colors from blue (green) to green (orange-red) because of the energy transfer of Ce3+ → Tb3+ and Tb3+ → Eu3+, respectively. Moreover, the efficient energy transfer from Ce3+ (Tb3+) to Tb3+ (Eu3+) ions in the co-doped samples was confirmed by investigating the excitation/emission spectra and decay lifetimes. The results indicate that the phosphors may be potentially used as single-component multi-color phosphors for white light-emitting diodes.
关键词： energy transfer,BaMgF4,white light-emitting diodes,phosphors,hydrothermal process
更新于2025-09-04 15:30:14
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Synthesis and luminescence properties of Eu3+-doped a novel double perovskite Sr2YTaO6 phosphor
摘要： A novel Sr2Y1?xTaO6:xEu3+ (x = 0.04–0.20) red-emitting phosphor was synthesized by using the conventional solid-state reaction method. The crystal structure, photoluminescence properties, thermal stability and decay lifetimes were investigated in detail. Upon near UV light excitation, this sample exhibited a strong red emission peak centered at 612?nm due to 5D0 → 7F2, which indicated that Eu3+ occupies low symmetry sites within the Sr2YTaO6 host lattice. The optimized doping concentration of Eu3+ ion is about 12?mol%. The excellent thermal stability of Sr2YTaO6:Eu3+ phosphor was tested according to the temperature dependent emission spectra. In addition, the Sr2Y1?xEuxTaO6 phosphors exhibited good color coordinate (0.6076, 0.3879) and high color purity about 84.55%. All results indicated that the Sr2Y1?xTaO6:xEu3+ phosphors can serve as an efficient red phosphor in the white light emitting diodes.
关键词： Sr2YTaO6:Eu3+,phosphor,luminescence,thermal stability,white light emitting diodes
更新于2025-09-04 15:30:14