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Carbon Dots exhibiting Concentration-Dependent Full-Visible-Spectrum Emission for Light-Emitting Diode Applications
摘要： Carbon dots (CDs) that exhibit emission over the whole visible spectrum are desired for using in light-emitting diodes. Here, CDs displaying tunable fluorescence over the whole visible region are synthesized. Different concentrations of CDs are uniformly dispersed in epoxy resin and coated on 405-nm LED chips to obtain monochrome blue, cyan, green, yellow, red, and deep red LEDs that yield a color gamut covering 99.4% of the National Television Standards Committee (NTSC) standard. These monochrome LEDs display similar stability decay curves. Furthermore, warm and neutral white LEDs are produced by coating cyan- and red-emitting CD layers on 405-nm LED chips, achieving color rendering indexes (CRI) of 96.4 and 96.6, respectively. Two fluorescent conversion layers derived from one material at different concentrations simplifies the preparation of high-CRI white LEDs. The uniform weak changes of the cyan and red PL peaks during operation ensures the high stability of these CD-based white LEDs. This research provides a new avenue to develop low-cost, easy-to-prepare CDs with tunable emission colors as alternative phosphors for LED-based high-performance displays and lighting.
关键词： full-visible-spectrum emission,monochrome light-emitting diodes,concentration-dependent spectrum-tunable carbon dots,high color rendering index,white-light-emitting diodes
更新于2025-09-12 10:27:22
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Closing the Cyan-Gap toward Full Spectrum LED Lighting with NaMgBO3:Ce3+
摘要： The photoluminescence spectrum generated by an ordinary phosphor-converted white light-emitting diode (pc-wLED) that combines a blue LED chip with a yellow phosphor or a near-UV LED with red, green and blue phosphors contains a notable cavity in the cyan region of the visible spectrum (480-520 nm) that reduces the color quality produced by these lights. Here, we report a new bright blue-cyan-emitting phosphor, NaMgBO3:Ce3+, that bridges the gap. Rietveld refinements verify the rare-earth substitution while ab initio calculations prove Ce3+ occupies the Na+ sites. NaMgBO3:Ce3+ is excited by a broad range of near-UV light sources and produces a blue-cyan emission with a high (internal) quantum efficiency, minimal thermal degradation, and zero-chromaticity drift at elevated temperatures. Fabricating a near-UV (λex = 370 nm) pumped pc-wLED using NaMgBO3:Ce3+ along with commercially available phosphors demonstrates a well-distributed warm white light with a high color-rendering index (Ra) of 91 and a low correlated color temperature (CCT) of 3645 K. Closing the cyan cavity with NaMgBO3:Ce3+ is ideal for generating a pleasant, full-spectrum, warm white light.
关键词： full-spectrum LED lighting,NaMgBO3:Ce3+,blue-cyan-emitting phosphor,color-rendering index,phosphor-converted white light-emitting diode
更新于2025-09-12 10:27:22
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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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Zn-Alloyed All-Inorganic Halide Perovskite-Based White Light-Emitting Diodes with Superior Color Quality
摘要： Recently, lead halide perovskite nanocrystals (NCs) have gained tremendous attention in optoelectronic devices due to their excellent optical properties. However, the toxicity of lead limits their practical applications. Here, the synthesis of Zn2+-alloyed CsZnxPb1-xX3 (up to 15%) NCs is reported to achieve lead-reduced white light-emitting diodes (WLEDs). The incorporation of Zn2+ into CsPbX3 host NCs results in a lattice contraction, without altering the structure and morphology, which has a direct effect on the optical properties. The blue-shifts in the photoluminescence emission and increase in bandgap is observed while retaining high photoluminescence quantum yield. Then by engineering the different compositions of halides for 15% Zn2+-alloyed CsZnxPb1-xX3 NCs, tunable emission (411–636 nm) is obtained. Notably, the WLEDs are experimentally demonstrated employing the lead-reduced NCs (blue, green, yellow, and red). By varying the ratios of the amount of NCs, white lights with a tunable correlated-color temperature (2218–8335 K), an exemplary color-rendering index (up to 93) and high luminous efficacy of radiation (268–318 lm·W?1) are obtained. Best of our knowledge, these are superior to other reported WLEDs based on CsPbX3 NCs doped with transition metal ions. This work places the halide perovskite NCs one-step closer in designing the environmentally benign and energy-efficient WLEDs.
关键词： White Light-emitting Diodes,Zn-Alloyed,Color Quality,All-inorganic Halide perovskite
更新于2025-09-12 10:27:22
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Novel Bromide Quaternary Ammonium Ligand for Synthesizing High Fluorescence Efficiency CsPbBn Perovskite Quantum Dots and Their Fabrication of White Light-Emitting Diodes with Wide Color Gamut
摘要： We proposed a novel bromine quaternary ammonium ligand to synthesize high quantum yield (QY) CsPbBr3 quantum dots (QDs). The QY of CsPbBr3 QDs synthesized by this ligand reached 95% and the full width at half maximum (FWHM) was as narrow as 17nm. The peak wavelength of the prepared CsPbBr3 QDs was 530nm. And these QDs emitted high purity green light under ultraviolet light. The color coordinate of white LED (WLED) prepared with the CsPbBr3 QDs was (0.29, 0.31), which was very close to pure white light. The color gamut of the WLED covered 130% of the national television system committee (NTSC) color standard and 96% of the ITU-R Recommendation BT.2020 (Rec.2020) color standard.
关键词： CsPbBr3 Perovskite Quantum Dots,Bromide Quaternary Ammonium Ligand,Wide Color Gamut,White Light-Emitting Diodes
更新于2025-09-12 10:27:22
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Mussel‐Inspired Polymer Grafting on CsPbBr <sub/>3</sub> Perovskite Quantum Dots Enhancing the Environmental Stability
摘要： Mussel-inspired chemistry, motivated by the adhesive proteins secreted by mussels for attachment to wet surfaces, is an emerging technique for manipulating the surface properties of a variety of materials. Here, a facile mussel-inspired poly(N-vinyl pyrrolidone) (PVP) polymer encapsulation with trivial influence on inherent optical properties of perovskite quantum dots (QDs) is demonstrated to efficiently combat the low intrinsic thermal, chemical, and photostability of CsPbBr3 QDs. The suitability of photopolymer-processed PVP-CsPbBr3 QDs flexible films as color components in white light–emitting devices is substantiated.
关键词： perovskite quantum dots,stability,white light-emitting diodes,photoluminescence,polymer grafting
更新于2025-09-12 10:27:22
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Luminescent properties of CaSc2O4:Ce3+ green phosphor for white LED and its optical simulation
摘要： Green-emissive Ce3t-doped CaSc2O4 phosphors were synthesized by solid-state method. The water washing process of the as-prepared samples was several times conducted because of severe hydration of unreacted CaO and CaF2 flux residual. The washed CaSc2O4:Ce3t phosphors showed a single phase with a crystallite size of 1–3 μm, and its photoluminescence intensity was 10% improved compared with the as-prepared. It shows the broad 450 nm excitation peak and the green emission peak at 520 nm with a half width of 105 nm. Its temperature dependence showed the similar thermal stability with a commercial silicate phosphor. The optical simulation and the real fabrication of white LEDs with a combination of our green phosphor and one of possible orange-red phosphors demonstrated that the white LED with Sr3SiO5:Eu2t orange phosphor gives the best luminous efficacy and the appropriate color rendering index of 70 under the daylight color temperature of 6400 K.
关键词： CaSc2O4:Ce3t,White-light-emitting diode,Optical simulation,Photoluminescence,Green emission
更新于2025-09-12 10:27:22
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UV Resin Enhanced Stability of Metal Halide Perovskite Nanocrystals for White Light-Emitting Diodes
摘要： The long-term stability issue of metal halide perovskite nanocrystals (NCs) is one of the challenges for the applications in optoelectronic devices. Herein, we demonstrate the enhanced air, moisture, and light stability of these NCs by encapsulation into UV Resin (UVR). As prepared perovskite NCs-UVR composites exhibit well maintained optical properties. In addition, the composites show excellent stability with almost identical luminescent behavior for more than 60 days upon continuous exposure in air, moisture, light irradiation, which is superior to the other previous reports. Moreover, we have used these green- and red-emitting composite sheets to fabricate white light-emitting diodes (LEDs) by stacking them on top of the blue LED. We observed a bright neutral white light with a correlated color temperature of 5623 K, a color-rendering index of 85, and a high luminous efficacy of radiation (~349 lm/W). Our findings show the great potential of employing this technique for diverse photonic applications.
关键词： halide perovskites,UV resin,air and moisture stability,white light-emitting diodes,polymerization
更新于2025-09-12 10:27:22
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Performance Evaluation of Single-Junction Indoor Photovoltaic Devices for Different Absorber Bandgaps Under Spectrally Varying White Light-Emitting Diodes
摘要： In this article, we present a detailed theoretical study to predict performance characteristics of single-junction indoor photovoltaic (PV) devices operated under white light emitting diodes (LEDs) having different spectral characteristics. Efficiency limits of both ideal and practical PV converters have been evaluated considering illumination by commercially available white LEDs. The obtained results have been generalized for white LED sources having a wide range of correlated color temperatures (CCTs) and fraction of blue in their corresponding spectrum. Depending on bandgap of the absorber material, both positive and negative correlations are observed between photon conversion efficiency of PV devices and CCT values of the white LED sources. For material bandgaps of ～1.5 eV or lower, higher photon conversion efficiencies are obtained for warm glow white LEDs. On the contrary, white LEDs characterized to emit cool light are found to be more conducive for PV devices having absorber layer bandgaps of ～2 eV or higher. The observed characteristics have been explained in terms of linewidth of the main emission peak and relative intensity of blue emission peak of the irradiating white LED spectrum. Based on the analysis of photon yield, three distinct bandgap ranges of the PV absorber material have also been identified, each of which represents different dependence of PV device performances on the white LED spectral characteristics. These results in effect provide the necessary guidelines for designing homojunction, heterojunction, or tandem PV devices suitable for operation under different practical white LED sources.
关键词： red-green-blue (RGB) white light emitting diodes (LEDs),energy conversion efficiency,photon yield,Correlated color temperature,indoor photovoltaic (PV)
更新于2025-09-12 10:27:22
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Synthesis and electroluminescence of novel white fluorescence quantum dots based on a Zn–Ga–S host
摘要： White-light-emitting Ag, Mn: Zn–Ga–S/ZnS quantum dots (QDs) with a gratifying photoluminescence (PL) quantum yield (QY) of up to 90% were prepared, and shown to be ultra-stable, maintaining a high PL intensity at 300 8C or for 32 h of UV illumination. These QDs were employed in a white QD-LED displaying a color rendering index (CRI) of 72 and maximum current efficiency of 0.22 cd A(cid:2)1.
关键词： QD-LED,Quantum dots,Current efficiency,Quantum yield,White-light-emitting,Photoluminescence,Color rendering index,Ultra-stable
更新于2025-09-12 10:27:22