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Improved luminescence properties of a novel red dodec-fluoride phosphor Ba <sub/>3</sub> Sc <sub/>2</sub> F <sub/>12</sub> :Mn <sup>4+</sup> with extraordinary thermal stability for WLED application
摘要： Mn4+-activated red phosphors have recently attracted tremendous attention for their fascinating performance in white light emitting diodes (WLEDs) application to achieve warm white light, while the thermal stability of fluoride is still considered as a drawback. Herein, we report a novel red phosphor composed of Ba3Sc2F12:Mn4+ (BSF:Mn), in which, the emitting centers of Mn4+ ions are locating in the sites of Sc3+ ions. The photoluminescence of BSF:Mn varies with the concentration of K2MnF6, reaction temperature, and the concentrations of NH3·H2O in reaction system. Partly substituting Ba2+ with Ca2+ decreases the luminescent intensity of BSF:Mn. By employing the as-prepared phosphor BSF:Mn as a red component, a high-performance WLED with a correlated color temperature (CCT) at 4796 K and a color rendering index (CRI) of 85.2 was obtained. The phosphor BSF:Mn keeps undecomposed up to 800 oC, therefore, this work exhibits a strategy to explore a novel Mn4+-doped fluoride with particularly thermal stability.
关键词： luminescent properties,thermal stability,Ba3Sc2F12:Mn4+,Mn4+-activated red phosphors,WLEDs
更新于2025-09-19 17:13:59
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Stable and efficient hybrid Ag-In-S/ZnS@SiO2-carbon quantum dots nanocomposites for white light-emitting diodes
摘要： As a promising energy-saving technique, the eco-friendly and low-cost solid-state white light-emitting diodes (WLEDs) based on quantum dots (QDs) have been widely studied. Herein, a WLED device prepared by core–shell structure nanocomposites based on Ag-In-S/ZnS@SiO2 quantum dots (AIS@SiO2) and carbon quantum dots (CDs) was successfully constructed. CDs were combined onto the surface of AIS@SiO2 QDs to synthesize Ag-In-S/ZnS@SiO2-Carbon quantum dots (AIS-CDs) nanocomposites with a white-light emission, which successfully overcome the quenching effect of CDs induced by conventional aggregation. The as-prepared AIS-CDs nanocomposites presented high stability and a photoluminescence quantum yield (PLQY) of 35%. Moreover, the corresponding AIS-CDs nanocomposites-based WLEDs demonstrated the color coordinate of (0.32, 0.33), which is comparable to the pure white light (0.33,0.33); Furthermore, the luminous efficiency of the as-prepared WLEDs showed 15.1 lm W-1. These results reported herein may open up a new avenue for the development of high-performance, low-cost, and environmentally-friendly WLEDs.
关键词： WLEDs,Ag-In-S/ZnS QDs,Nanocomposites,CDs
更新于2025-09-19 17:13:59
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Cs <sub/>4</sub> PbBr <sub/>6</sub> /CsPbBr <sub/>3</sub> perovskite composites for WLEDs: pure white, high luminous efficiency and tunable color temperature
摘要： Cs4PbBr6/CsPbBr3 perovskite composites are fabricated by room-temperature one-pot mixing synthesis, which is short in time, free from inert gases and delivers a high product yield. Temperature-dependent photoluminescence shows that a larger exciton binding energy of 291.1 meV exhibits better thermal stability compared with that of pure Cs4PbBr6 and CsPbBr3 materials. The CIE chromaticity coordinates (0.1380, 0.7236) of green LEDs designed with Cs4PbBr6/CsPbBr3 perovskite composites show almost no variation under driving current changing from 5 to 30 mA. Furthermore, the ground Cs4PbBr6/CsPbBr3 perovskite composites mixed with red emitting K2SiF6:Mn4+ phosphor are dropped and casted on a blue-emitting InGaN chip. The white light emitting diodes (WLEDs) are presented, which have good luminous e?ciency of 65.33 lm W(cid:1)1 at 20 mA, a correlated color temperature of 5190 K, and the white gamut with chromaticity coordinate of (0.3392, 0.3336). According to the state of art, these excellent characteristics observed are much superior to the reported results of conventional perovskite-based WLEDs, which demonstrate the immense potential and great prospect of Cs4PbBr6/CsPbBr3 perovskite composites to replace conventional phosphors in lighting devices.
关键词： WLEDs,luminous efficiency,tunable color temperature,Cs4PbBr6/CsPbBr3 perovskite composites
更新于2025-09-16 10:30:52
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White Light-Emitting Diodes With Ultrahigh Color Rendering Index by Red/Green Phosphor Layer Configuration Structure
摘要： Currently, white light-emitting diodes (WLEDs) have been widely applied in lighting, display, and medical fields. However, there still exists the problem of low color rendering index (CRI, Ra). In this work, phosphor-converted WLEDs (pc-WLEDs) with ultrahigh Ra were fabricated using Y3Al3Ga2O12:Ce3+ green phosphor and CaAlSiN3:Eu2+ red phosphor configuration structure. The broad emission spectrum of the green phosphor compensates for the gap of the cyan-emitting region that realizes full-spectrum white-light emission. The weight ratio of green/red phosphors was controlled to optimize the optical performances of pc-WLEDs. At the ratio of 0.15/0.012, the fabricated pc-WLED exhibits a natural white light with an ultrahigh Ra of 95.2 and an incredibly small International Commission on Illumination (CIE) chromaticity coordinates deviation (Duv = ?0.0034) at 350 mA. The corresponding correlated color temperature (CCT) and luminous efficiency (LE) are 4526 K and 62.34 lm/W, respectively. Furthermore, two separated phosphor configuration structures were constructed for pc-WLEDs. The R up/G down structure achieves the highest LE of 64.93 lm/W, and the corresponding CCT and Ra are 5714 K and 95.8, respectively, chiefly due to the compensation for reabsorption effect caused by the large difference in the luminous efficacy of radiation (LER) between dichromatic phosphors. The results demonstrate that by adjusting the phosphor configuration structure, the pc-WLEDs with high color rendering can be obtained, which have great applications in high-quality lighting.
关键词： white light-emitting diodes (WLEDs),High color rendering,separated phosphor layer,phosphor configuration
更新于2025-09-12 10:27:22
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Ethylene glycol-assisted ultrafast synthesis and luminescent properties of novel multifunctional EuSr2F7 and TbSr2F7 nanostructures for WLEDs, displays and anti-counterfeiting
摘要： In this paper, novel EuSr2F7 and TbSr2F7 nanostructures were successfully prepared via an ultrafast wet-chemical route at room temperature. The elemental compositions, morphology, luminescent behaviors, thermal stability, decay curves and quantum yield of the as-prepared samples were investigated. The fabricated white light-emitting diodes (WLEDs) devices exhibited excellent CRI and CCT values. The security inks and soft polydimethylsiloxane films were prepared for potential anti-counterfeiting and flexible display applications. Eventually, under low accelerating voltage and filament current, the as-prepared samples showed strong cathodoluminescence emission intensity. The above results suggest that the novel EuSr2F7 and TbSr2F7 nanostructures with outstanding luminescent performances could be promising for field-emission displays (FEDs), WLEDs, flexible display films, and anti-counterfeiting applications.
关键词： nanostructures,FEDs,anti-counterfeiting,WLEDs,flexible display films
更新于2025-09-12 10:27:22
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Solution Combustion Synthesis of ZrO 2 :Tb 3+ Nanophosphors Viable for WLEDs
摘要： Tb3+ doped Zirconium oxide (ZrO2) nanopowders were synthesized by solution combustion method using oxalyl di-hydrazide (ODH). The effect of dopant concentration on the crystal structure and photoluminescence properties of the nano phosphors were investigated. Band gap of the samples were obtained from Wood and Tauc plot. Scanning electron microscopy analysis reveals the formation of porous powders with large amount of voids. Room temperature photoluminescence shows visible luminescence of the phosphors under near UV excitation. The colour index of phosphors were calculated using CIE co-ordinates. These phosphors show bright green emission centered at 550 nm. The emission intensity increased with Tb3+ concentration up-to 5 mol% and decreased thereon. All these samples were emitting green colour having colour coordinates at (0.25,0.65). The colour purity of the samples reveals that these phosphors are promising candidates as green emitting phosphors in the tricolor GaN based white light emitting diodes.
关键词： Phosphors,Zirconia,Terbium,WLEDs,Photoluminescence
更新于2025-09-12 10:27:22
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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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Photoluminescence Tuning in Novel Bi3+/Mn4+ Co-doped La2ATiO6:(A = Mg, Zn) Double Perovskite Structure: Phase Transition and Energy Transfer
摘要： Red-emitting phosphors are indispensable componans to achieve warm white light of phosphor-converted white light emitting diodes (pc-WLEDs). However, the luminous efficiency and stability for red phosphors are still a big challenge. In this work, we develop red-emitting double perovskite phosphors La2ATiO6:Bi3+, Mn4+ (A = Mg, Zn) (LAT: Bi3+, Mn4+) and disscuss the relationship between double perovskite phosphors structure and luminescence performance in detail. By designing Mg2+/Zn2+ cation substitution, It is noteworthy that the internal quantum efficiency (IQE) is remarkeblely enhanced beyond 20%. According to Rietveld refinement results for La2Mg(1-w)ZnwTiO6:Bi3+, Mn4+ (0 ≤ w ≤ 1) (LM(1-w)ZwT:Bi3+, Mn4+) solid solution, the proposed machanism of the spectral adjustment is ascribed to the appearance of phase transition, which results in a lower local structure symmetry of [LaO12] polyhedron and variation of crystal field environment for Mn4+. Notably, it is the first time to reveal the influence of local structure variation on luminescence tuning in double perovskite structure phosphors, which could offer a guidance to develop new phosphors system. In addition, we firstly succeed in realizing Bi3+/Mn4+ co-doped energy transfer in double perovskite structure phosphors. Due to the Bi3+→Mn4+energy transfer in LAT, red emission of Mn4+ ions could be dramatically enhanced. The energy transfer efficiency of LAT: Bi3+, Mn4+ eventually reaches exceed 90%. The IQE and thermal stability are all enhanced around 30% than non-codoped samples, respectively. These results indicate that Bi3+→Mn4+energy transfer strategy could play a pivotal role in developing highly efficient red-emitting phosphor. The performance of the fabricated pc-WLEDs devices indicates that LAT:Bi3+, Mn4+ could be a promising red phosphor for near ultraviolet (n-UV) based on warm pc-WLEDs.
关键词： pc-WLEDs,Bi3+/Mn4+ co-doped,double perovskite phosphors,energy transfer,Red-emitting phosphors
更新于2025-09-10 09:29:36