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Improvement of Optical and Thermal Properties for Quantum Dots WLEDs by Controlling Layer Location
摘要： The inorganic halide perovskite quantum dots (QDs) have been considered as a promising substitute for white light-emitting diodes (WLEDs). In this article, the green CsPbBr3 QDs and red K2SiF6:Mn4+ (KSF) phosphor were used to fabricate the conversion layers. Because the layers location is fundamental to the absorption priority of blue light, the location of KSF and QDs were controlled and the QDs-up type and QDs-down type WLEDs were made. The optical power, luminous efficiency, CCE and luminous intensity in the middle of QDs-up type are 13.83 mW, 13.54 lm/W, 11.94% and 2.65 cd, meaning 24.26%, 25.72%, 2.63% and 23.83% higher than those of QDs-down type, respectively. In addition, the QDs-up type has a lower correlated color temperature (CCT) shift of 734 K and a decreased highest temperature of 56.8℃ (51.5% and 14.9% lower). These key property differences indicate that the QDs-up type is more suitable for the application in display and backlight. In order to explore the reasons for these differences, the emission spectra, CCE, reflection rate, absorption rate and temperature curves of QDs or KSF films were also analyzed, which provided a better understanding of designing package structures.
关键词： layer location,thermal properties,quantum dots WLEDs,optical properties
更新于2025-11-19 16:46:39
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Room temperature synthesis of stable single silica-coated CsPbBr3 quantum dots combining tunable red emission of Ag–In–Zn–S for High-CRI white light-emitting diodes
摘要： White light emitting diodes (WLEDs) based on all-inorganic halide (CsPbX3, X ? Cl, Br and I) perovskite quantum dots (QDs) have attracted broad attention due to their high brightness. However, their poor stability and anion-exchange reaction when utilized together are still the main challenges that impede their applications. Herein, a one-step in situ method under room temperature in air is proposed to synthesize CsPbBr3 QDs coated with SiO2 (CsPbBr3@SiO2), where the whole process takes only 20 s. The as-prepared CsPbBr3@SiO2 QDs samples present an enhanced stability in the thermal and polar-solvent environment, maintaining its high photoluminescence quantum yield (PLQY~75%). Thereby WLEDs are constructed by combining CsPbBr3@SiO2 with red Ag–In–Zn–S QDs on InGaN blue chip, achieving a high color rendering index (CRI) of 91, a correlated color temperature (CCT) of 3689 K and a power efficiency of 40.6 lm W?1.
关键词： WLEDs,Ag–In–Zn–S QDs,Stability,CsPbBr3 QDs
更新于2025-11-14 15:32:45
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Single-Molecule Based Electroluminescent Device as Future White Light Source
摘要： During last two decades spectacular development of light emitting diodes (LEDs) has been achieved owing to their widespread application possibilities. However, traditional LEDs suffer from unavoidable energy loss due to the down conversion of photons, toxicity due to the involvement of rare-earth materials in their production, higher manufacturing cost, and reduced thermal stability that prevent them from all-inclusive applications. To address the existing challenges associated with current commercially available white LEDs, herein, we report on a broadband emission originating from an intrinsic lanthanide-free single-molecule based LED. Self-assembly of a butterfly-shaped strontium-based compound {[Sr(H2btc)2(MeOH)(H2O)2]·2H2O} (1) was achieved through the reaction of Sr(NO3)2 with a benzene-1,2,3-tricarboxylic acid hydrate (1,2,3-H3btc) under hydrothermal conditions. White LED based on this single molecule exhibited a remarkable broadband luminescent spectrum with Commission Internationale de l’Eclairage (CIE) coordinates at (0.33, 0.32) under 30 mA current injection. Such a broad luminescent spectrum can be attributed to the simultaneous existence of several emission lines originating from the intramolecular interactions within the structure. To further examine the nature of the observed transitions, density functional theory (DFT) calculations were carried out to explore the geometric and electronic properties of the complex. Our study thus paves the way toward a key step for developing a basic understanding and the development of high performance broadband light emitting devices with environment-friendly characteristics based on organic?inorganic supramolecular materials.
关键词： Electroluminescence,Photoluminescence,Single Molecule,WLEDs,Strontium
更新于2025-09-23 15:23:52
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Synthesis of Silica-Coated Csa??PbBra?? and Csa??Pb(Br0.4I0.6)a?? Quantum Dots With Long Lifetime and Enhancement in Quantum Efficiency for WLEDs Applications: Lightings With High CRI and Displays With Wide Color Gamut
摘要： To focus on developing white light-emitting diodes (WLEDs) for lightings with high color rendering index (CRI), low correlated color temperature (CCT), and the displays with wide color gamut, inorganic perovskite quantum dots (QDs) such as CsPbX3 (X = Cl, Br, I) were the promising candidate owing to the excellent optoelectronic properties such as high quantum efficiency, narrow emission wavelengths, and tunable emission spectrum. Nevertheless, the CsPbBr3QDs in the form of powders or films had a poor air stability and severe decline of quantum efficiency. Therefore, in this article, a new idea was proposed that 0-D green–red perovskite QDs powders such as Cs4PbBr6 and Cs4Pb(Br0.4I0.6)6 with improved quantum efficiency and long lifetime were first developed by silica-coated method and crystal phase transition in low-temperature synthesis. The quantum efficiency in green Cs4PbBr6 powders could be significantly enhanced from 31.41% to 45.87% and red Cs4Pb(Br0.4I0.6)6 powders was 22.79%. Moreover, the as-prepared perovskite QD powders and commercial YAG phosphors combined with blue chips were applied to high-quality WLEDs for lightings and displays. More importantly, the as-fabricated wide Commission Internationale de l’Eclairage (CIE) color gamut WLEDs for displays possessed 115% National Television System Committee (NTSC) coverage rate and luminous efficiency of 51 lm/W under 20-mA driving current. On the other hand, the constructed WLEDs for high-power lightings would generate a warm white light with a luminous efficiency of 38 lm/W, extremely high CRI of 92.8, and low CCT of 3828 K under 350 mA. Hence, the proposed green–red perovskite QD powders had outstanding potential applications in WLEDs.
关键词： white light-emitting diodes (WLEDs),0-D perovskite quantum dots (QDs),backlights of displays,solid-state lightings
更新于2025-09-23 15:21:01
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Highly efficient Mn doped CsPb(Cl/Br)3 quantum dots for white light-emitting diodes
摘要： White light-emitting diodes (WLEDs) based on all-inorganic perovskite CsPbX3 (X = Cl, Br, I) quantum dots (QDs) have attracted great attention, which rely on mixing several colors of perovskites. However, this inevitably leads to a non-uniform light distribution and serious light loss. Here, a novel strategy was demonstrated to obtain white emission by combining the orange and blue emission from CsPb/Mn(Cl/Br)3 QDs. Notably, highly efficient white emission with photoluminescence quantum yield (PLQY) of 94% was achieved by an anion exchange surface engineering (AESE) strategy. After the AESE treatment, the surface traps can be eliminated, resulting in improved exciton and Mn2+ emission. A prototype WLED device is fabricated, which exhibits excellent optical stability, demonstrating great potential for the perovskite QDs in the field of optoelectronics.
关键词： quantum dots,perovskite,WLEDs,Mn doping,energy transfer
更新于2025-09-23 15:19:57
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Single-phased chromaticity-tunable phosphor of Sr <sub/>4</sub> Al <sub/>14</sub> O <sub/>25</sub> : Eu <sup>2+/3+</sup> co-doped with Tb <sup>3+</sup> for white-light-emitting diodes
摘要： The single-phased phosphors doped with Eu2+ and Eu3+ have shown the potential for the application of white-light-emitting diodes (wLEDs). In this manuscript, we introduced a simple method of co-doping terbium ions into the Sr4Al14O25: Eu2+/3+ phosphor to achieve the tunable chromaticity and the good color rendering performance. The phosphor was synthesized through the conventional solid-state reaction in a non-reducing atmosphere. The phase purity was examined by XRD analysis, and the luminescent properties were discussed systematically depending on the room- and low-temperature photoluminescence spectra. The emission spectrum of the sample Sr4Al14O25: 0.01Eu2+/3+, 0.06Tb3+ covered the whole visible spectral region with a white light emission (0.2799, 0.3059), indicating that the present phosphor could be suitable for the wLEDs application.
关键词： self-reduction,wLEDs,phosphor,photoluminescence
更新于2025-09-23 15:19:57
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Highly Efficient Orange Emissive Graphene Quantum Dots Prepared by Acid-Free Method for White LEDs
摘要： Graphene quantum dots (GQDs) have wide prospective applications for optoelectronic fields owing to their unique characteristics, such as tunable bandgaps, high chemical and optical stability, as well as good biocompatibility. In this work, we offered a convenient proposal to obtain uniform blue-green emissive GQDs and modified efficient orange-emitting graphene quantum dots (D-GQDs) derived from fullerene (C60) under acid-free condition. The as-prepared D-GQDs demonstrate remarkable conversion efficiency which quantum yield is up to 52.4% with the emission peak of 617 nm. Also, GQDs and D-GQDs were blended with poly(vinyl alcohol) (PVA) to prepare transparent photo-luminescent films, which show excellent flexibility and preferable white emission property meeting the requirements of commercial white LEDs.
关键词： Graphene quantum dots,Quantum yield,Acid-free condition,WLEDs
更新于2025-09-23 15:19:57
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Morphology control and luminescence properties of red-emitting BaSiF6:Eu3+ hexagonal nanorod phosphors for WLEDs
摘要： To promote the development of solid-state lighting industry, exploring excellent inorganic phosphors has been always a scientific and applied hot issue. Herein, a series of efficient red BaSiF6:Eu3+ hexagonal nanorod phosphors with varied size and morphology were successfully prepared through a hydrothermal route. The reaction time, dosage of surfactant and solvent play an important role in the formation of the nanorod structures. The corresponding formation mechanism was discussed and revealed. The effects of surfactant, reaction time and solvent on photoluminescence properties of the as-prepared BaSiF6:Eu3+ nanorod phosphors were investigated in detail. Under excitation at 394 nm, all samples emit bright red light due to the typical Eu3+ 4f-4f transitions. Comparing the luminescence intensity of samples with different size of nanorods, it is found that the length of the nanorod is about 10–20 μm, the luminescence intensity of the sample is 3–5 times of the initial intensity of the nanorod sample that the length is around 30–40 μm. Moreover, when adding ethylene glycol as a solvent, the luminescence intensity of samples with different morphology increases with the increase of the reaction time. Importantly, as the temperature rising to 150 °C, the integrated intensity of the as-prepared sample still could obtain more than 95% of the intensity at room temperature, indicating the phosphors show excellent thermal stability. Thus, the as-prepared BaSiF6:Eu3+ nanorod phosphor is a potential red-emitting phosphor for white light-emitting diodes (WLEDs).
关键词： BaSiF6:Eu3+,luminescence properties,hydrothermal synthesis,thermal stability,WLEDs,hexagonal nanorod phosphors
更新于2025-09-23 15:19:57
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Structural micro-modulation on Bi3+ doped Ba2Ga2GeO7 phosphor with considerable tunability of the defect-oriented optical properties
摘要： We report a new Ba2Ga2GeO7:Bi3+ phosphor with broad emission almost covers the entire visible area generated from different bismuth emission centers in crystalline structure. The two peaks positions are invariably located at 497 and 611 nm which were independently excited by 365 and 387 nm excitation sources. As the emission tightly relies on the excitation source in an extremely wide range (260 to 470 nm), the emission color can be easily manipulated from cyan to red. The WLEDs devices with Ra = 90.40 and 91.98 were fabricated by employing Ba2Ga2GeO7:0.012Bi3+ as a red component phosphor. Through analyzing, we found P2 (Ga/Ge) sites tend to form vacancies in the sintering process. When bismuth concentration is set fixed, the luminescent intensity is quite dependent on the quantity of Ga or Ge vacancies which are beneficial to form Bi3+ emission centers and provide a fresh idea for structural micro-modulation. Our results also provide new insights for understanding the roles of the vacancy played in phosphors.
关键词： luminescence,bismuth,color-tunable,WLEDs,phosphor,vacancy
更新于2025-09-19 17:15:36
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Synthesis and photoluminescence studies of novel double-perovskite phosphors, Ba2GdTaO6:Eu3+ for WLEDs
摘要： A series of novel double-perovskite type red emitting phosphors, Ba2Gd1-xTaO6:xEu3+ were synthesized via solid-state reaction route. Powder X-ray diffraction results confirmed the cubic perovskite phase and scanning electron microscope was used to evaluate the morphology of the phosphors, respectively. Detailed studies on UV-Vis absorption showed that Eu3+ doped Ba2GdTaO6 phosphors have obvious absorption in the ultraviolet region. The excitation of UV (CTB), near UV (394 nm) and blue light (467 nm) match the output wavelength of ultraviolet and blue LED chips, and red-light emission is observed, which is mainly due to the magnetic dipole (5D0→7F1) and electric dipole transition of (5D0→7F2) of Eu3+. The results show that the energy transfer from Gd3+ to Eu3+ enhances the luminescence. Concentration quenching was observed when Eu3+ doped at more than 10 mol%. Thermal quenching was measured and the activation energy was 0.230 eV. The prepared phosphors have potential applications in WLEDs.
关键词： WLEDs,Optical materials,Photoluminescence,Phosphors
更新于2025-09-19 17:13:59