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Efficient White LEDs Using Liquid-state Magic-sized CdSe Quantum Dots
摘要： Magic clusters have attracted significant interest to explore the dynamics of quantum dot (QD) nucleation and growth. At the same time, CdSe magic-sized QDs reveal broadband emission in the visible wavelength region, which advantageously offer simple integration of a single-type of nanomaterial and high color rendering ability for white light-emitting diodes (LEDs). Here, we optimized the quantum yield of magic-sized CdSe QDs up to 22% via controlling the synthesis parameters without any shelling or post-treatment process and integrated them in liquid-state on blue LED to prevent the efficiency drop due to host-material effect. The fabricated white LEDs showed color-rendering index and luminous efficiency up to 89 and 11.7 lm/W, respectively.
关键词： Magic clusters,Quantum dots,Luminous efficiency,CdSe,White light-emitting diodes
更新于2025-11-20 15:33:11
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Microstructure Influence of SACX0307-TiO2 Composite Solder Joints on Thermal Properties of Power LED Assemblies
摘要： The effect of the microstructure of solder joints on the thermal properties of power LEDs is investigated. Solder joints were prepared with different solder pastes, namely 99Sn0.3Ag0.7Cu (as reference solder) and reinforced 99Sn0.3Ag0.7Cu–TiO2 (composite solder). TiO2 ceramic was used at 1 wt.% and with two different primary particle sizes, which were 20 nm (nano) and 200 nm (submicron). The thermal resistance, the electric thermal resistance, and the luminous efficiency of the power LED assemblies were measured. Furthermore, the microstructure of the different solder joints was analyzed on the basis of cross-sections using scanning electron and optical microscopy. It was found that the addition of submicron TiO2 decreased the thermal and electric thermal resistances of the light sources by 20% and 16%, respectively, and it slightly increased the luminous efficiency. Microstructural evaluations showed that the TiO2 particles were incorporated at the Sn grain boundaries and at the interface of the intermetallic layer and the solder bulk. This caused considerable refinement of the Sn grain structure. The precipitated TiO2 particles at the bottom of the solder joint changed the thermodynamics of Cu6Sn5 formation and enhanced the spalling of intermetallic grain to solder bulk, which resulted in a general decrease in the thickness of the intermetallic layer. These phenomena improved the heat paths in the composite solder joints, and resulted in better thermal and electrical properties of power LED assemblies. However, the TiO2 nanoparticles could also cause considerable local IMC (Intermetallic Compounds) growth, which could inhibit thermal and electrical improvements.
关键词： power LED,SAC composite alloy,TiO2 ceramic,luminous efficiency,thermal resistance,microstructure characterization
更新于2025-09-23 15:19:57
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Enhancement of the luminous efficiency of a ceramic phosphor plate by post-annealing for high-power LED applications
摘要： Currently, phosphor-converted white light-emitting diodes offer low energy consumption, good environmental stability, and a long lifetime. Hence, they are widely utilized in high-power light-emitting diode (LED) applications such as those in the automotive headlamp industries. However, obtaining high luminous efficiency of such diodes is challenging because of their internal structural properties such as micropores. Herein, we developed phosphor-in-glass (PiG) plates by mixing a blue LED chip and yellow phosphor to create high-power white LEDs (w-LEDs). In addition, the influence of post-annealing on the prepared PiG plates at different temperatures (350°C-550 °C) was investigated. Post-annealing, a treatment that facilitates the mobility of the ceramic matrix encapsulating the phosphor powder, decreases an LED's porosity, thereby enhancing its overall luminous efficiency. Results show that PiG plates post-annealed at 450 °C exhibit superior optical performance and effective color properties than PiG plates that were non-annealed or post-annealed at 350 °C, 400 °C, 500 °C, and 550 °C. Therefore, post-annealed PiG plates are more suitable potential materials for application in the high-power LED industry.
关键词： Automotive headlamp,PiG plates,Post-annealing,High-power LED,Luminous efficiency
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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Ultraefficient Green LEDs Using Quantum Dots in Liquid Matrix
摘要： Green spectral range, which has the highest human eye sensitivity, is one of the most fundamental colors in lighting and display. Quantum dots (QDs) offer exceptional optical properties including high quantum yield (QY), strong absorption, and narrow emission linewidths for efficient green-emitting diodes. In this article, we demonstrated QD-based light-emitting diodes (QD-LEDs) that operate at a luminous efficiency (LE) level of 95 lumens per electrical watt, the luminous efficacy of optical radiation of 409 lumens per optical watt, and external quantum efficiency (EQE) of 23.3% in the green spectral region. For that, we synthesized 1-octanethiol-capped CdSe/ZnS QDs with an absolute QY of 91% and integrated them in a liquid matrix that allows conservation of the QD efficiency in device architecture. Our simulations were in agreement with the performance of the fabricated QD-LEDs, and they showed that the QD-LEDs can be further improved to reach LE levels over 250 lm/W.
关键词： light-emitting diodes (LEDs),luminous efficiency (LE),liquid-state integration,quantum dots (QDs),External quantum efficiency (EQE)
更新于2025-09-12 10:27:22
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Realizing white LEDs with high luminous efficiency and high color rendering index by using double green phosphors
摘要： The luminous efficiency of radiation (LER) and color rendering index (CRIs) are two key technological parameters of white light-emitting diodes (WLEDs), But there is always a trade-off between them, especially between LER and R9 (the 9th CRI of red colour). Therefore, it is necessary to solve this problem by selecting suitable phosphors, mixing and coating it on the LED chip. In this work, two green phosphors and one red phosphor with less resorption of the two phosphors were selected by measuring the excitation spectra of seven red phosphors and emission spectra of two green phosphors.Then, different mass ratios of the phosphors were mixed with the AB glue and coated on the blue LED chips. After optimizing the ratio by measuring the luminescence spectra of the LED chips coated with different mass ratios of phosphors,high-quality white LEDs with LER=142.74 lm/w,Ra=97,R9=98.53, and the correlated color temperature of 3666 K were obtained. These LEDs have both high LER and high CRIs, further reducing the trade-off between luminous efficiency and color rendering index, which makes it can widely used for high quality solid state lighting.
关键词： Color rendering index,Light-emitting diode,Luminous efficiency of radiation,Phosphor
更新于2025-09-11 14:15:04
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Influence of the Silver Nanocrystal Shape on the Luminous Efficiency of Blue-Emitting Polymer Light-Emitting Diodes
摘要： Truncated silver nanodecahedrons (TAgNDs) and truncated silver nanoplates (TAgNPs) fabricated via chemical reduction and photochemical methods were added to poly[3,4-ethylenedioxythiophene]:poly[styrenesulfonate] (PEDOT:PSS) as a dopant to promote the luminous efficiency of blue-emitting polymer light-emitting diodes (PLEDs). The differences in shape between TAgNDs and TAgNPs result in better dispersion of TAgNDs in PEDOT:PSS. Therefore, at an optimal doping concentration (the distributed density in the light-emitting region is 6.88 μg cm?2 for TAgNDs and 5.16 μg cm?2 for TAgNPs), the average current efficacy and maximum electroluminescence intensity enhancement factor for TAgNDs-doped PLED were 4.18 cd A?1 and 420% respectively, which are much higher than those for TAgNPs-doped PLED (1.83 cd A?1 and 200%) at a luminescence wavelength of 440 nm.
关键词： truncated silver nanoplates,blue-emitting polymer light-emitting diodes,luminous efficiency,truncated silver nanodecahedrons
更新于2025-09-11 14:15:04