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Design of highly efficient phosphor-converted white light-emitting diodes with color rendering indices (R1 ? R15) ≥ 95 for artificial lighting
摘要： Phosphor-converted white light-emitting diodes (pc-WLEDs) are excellent energy-efficient light sources for artificial lighting applications. One goal of artificial lighting is to make objects/images look natural – as they look under the sunlight. The ability of a light source to accurately render the natural color of an object is gauged by the parameter – color rendering index (CRI). A conventional pc-WLED has an average CRI ~ 80, which is very low for accurate color reproduction. To utilize the pc-WLEDs for artificial lighting applications, all the CRI points (R1 – R15) should be above 95. However, there is a trade-off between CRI and luminous efficacy (LER), and it is challenging to increase both CRI and LER. Herein we propose a novel LED package (PKG) design to achieve CRI points ≥95 and efficiency ~100 lm/W by introducing two blue LEDs and a UV LED in combination with green and red phosphors. The silicone encapsulant, the current through the LEDs, and the green/red phosphor ratio were optimized for achieving high CRI and LER. Our re-designed LED PKG will find applications in stadium lighting as well as for ultra-high-definition television production where high CRI points are required for the artificial light source.
关键词： artificial lighting,phosphor-converted white light-emitting diodes,color rendering index,luminous efficacy,LED package design
更新于2025-09-12 10:27:22
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Enhancement of efficiency and CCT uniformity for red phosphor thin films, red LEDs and laminated white LEDs based on near-ultraviolet LEDs using MgO nanoparticles
摘要： Red phosphor thin films (PTFs) with different MgO nanoparticle concentrations for near-ultraviolet (NUV) LEDs were prepared based on their strong scattering effect; red LEDs and laminated white LEDs were packaged further. SEM and XRD showed that CaAlSiN3:Eu2+ (CASN) and MgO nanoparticles were uniformly distributed in silicone resin and their crystal structure remained unchanged. The phosphor conversion efficiency (PCE) had a maximum value of 83.15% when the MgO nanoparticle concentration was 15 wt%. An increase of concentration can improve the spatial distribution uniformity of photonics for 410 nm, 627 nm and 660 nm. Fluorescence lifetime showed that the value is positively correlated with concentration change. The packaged red LED luminous flux reaches a maximum of 20.337 lm at a concentration of 15 wt%. The laminated white LED showed that the MgO nanoparticle concentration can be used to adjust the correlated color temperature (CCT) from 4322 K to 1987 K. Under similar CCT, the red phosphor concentration is only 1.83 wt%, the dosage is reduced by 56.12%, and the corresponding luminous efficiency of radiation (LER) and luminous efficiency (LE) are 296.03 lm W-1 and 73.72 lm W-1 respectively. The increase was 11.42%, the decrease was 10.14%, the color rendering index (CRI) increased from 90.6 to 91.8, and CCT uniformity increased from 82.04% to 89.27% with an increase of 8.81%. Research shows that MgO nanoparticles have potential application value in the preparation of high-quality white LEDs.
关键词： MgO nanoparticles,phosphor conversion efficiency,NUV LEDs,luminous flux,CCT uniformity,red phosphor thin films
更新于2025-09-11 14:15:04
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Blue Luminescent Phosphor Sr <sub/>3</sub> Y <sub/>1?X</sub> (BO <sub/>3</sub> ) <sub/>3</sub> : <sub/>X</sub> Bi <sup>3+</sup> for WLED Applications
摘要： The polycrystalline powder sample of Bi3+-activated strontium yttrium borate phosphor Sr3Y1?x(BO3)3:xBi3+ (x = 3, 4, 5 mole%) is prepared by solution combustion technique. Formation of phosphor in the desired crystalline phase is con?rmed by powder X-ray di?raction characterization and FTIR, SEM images of the synthesized phosphor show the irregular grains with average particle size 2.5 μm. Luminescence properties of the synthesized phosphor are investigated at room temperature. The excitation spectrum consists of a single broad absorption band from 200 to 370 nm with the prominent excitation peak at 336 nm [1S0 to 3P1 of Bi3+ ions] and weak excitation peak at 254 nm [1S0 to 1P1 of Bi3+ ions]. Strongest emission peak of 492 nm wavelength that is of blue light is observed at 336 nm UV light excitation. Sr3Y1?x(BO3)3:xBi3+ phosphor emits blue light. As Bi3+ is sensitive to the surrounding crystal ?eld environment it shows weak excitation peak at 254 nm, which gives emission at 413 nm. Hence, Sr3Y1?x(BO3)3:xBi3+ is new UV excited blue emitting phosphor useful for UV/blue chip WLEDs.
关键词： white light,photoluminescence,XRD,borate phosphor
更新于2025-09-11 14:15:04
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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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Insight into a Novel Garnet-based Yellowish-green Phosphor: Structure, Luminescence Properties and Application for Warm White Light-emitting Diodes
摘要： White light-emitting diodes (WLEDs) have been considered as the next generation lighting technology due to its advantages such as high efficiency and environmental friendliness. However, current mainstream WLEDs, which is based on blue chip and Y3Al5O12:Ce3+ yellow phosphor, suffer from the problem of low color rendering index (CRI). To solve this problem, a yellowish-green phosphor Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ (CYAS:Ce3+) based on garnet structure has been designed in this study. The crystal structure, band structure, luminescence properties have been investigated in detail. The CYAS:Ce3+ exhibits efficient and thermal-stable yellowish-green emission. The 5d centroid shift and crystal splitting of Ce3+ ion in CYAS has been analyzed together with the structure. Moreover, good warm white light with low correlated color temperature (3210 K),high color render index (85.1) and luminous efficacy (88.5 lm/W) has been obtained by combing the CYAS:Ce3+, red phosphor CaAlSiN3:Eu2+ with blue LED chip.
关键词： Garnet,WLED,Luminescence,Phosphor
更新于2025-09-11 14:15:04
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Tunable upconversion luminescence and optical temperature sensing based on non-thermal coupled levels of Lu3NbO7:Yb3+/Ho3+ phosphors
摘要： The color-tunable upconversion (UC) emission and optical temperature sensing based on non-thermal coupled levels (NTCL) were observed from the Yb3t/Ho3t codoped Lu3NbO7 phosphors synthesized by the solid-state method. The phosphors are capable of generating color tunable UC luminescence from green (yellow) to yellow (green) with the increase of the Yb3t concentration. The tunable emission is due to the different energy back transfer processes from Ho3t to Yb3t. The temperature sensing performances are investigated in the temperature range of 293–573 K based on NTCL by using fluorescence intensity ratio technology. The maximum absolute sensitivities are 0.37%K?1, 0.94%K?1, 0.27%K?1 at 298 K, which are based on three pairs NTCL of (5F4/5S2→5I8)/(5F5→5I8), (5F5→5I8)/(5F4/5S2→5I7) and (5F4/5S2→5I8)/(5F4/5S2→5I7) of Ho3t, respectively. The above results suggest that the as-prepared Lu3NbO7:Yb3t/Ho3t phosphors have great potential for the application prospects of upconverter, color tunable device and optical temperature sensor.
关键词： Phosphor,Optical temperature sensing,Lu3NbO7,Upconversion luminescence
更新于2025-09-11 14:15:04
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[IEEE 2019 16th International Multi-Conference on Systems, Signals & Devices (SSD) - Istanbul, Turkey (2019.3.21-2019.3.24)] 2019 16th International Multi-Conference on Systems, Signals & Devices (SSD) - Performance Evaluation of White LED-based OFDM-VLC Systems with Blue Filters: Experimental Study
摘要： This paper experimentally evaluates the performance of visible light communications (VLC) systems employing phosphor-coated white light emitting diodes (LEDs). Phosphor-coated white LEDs though widely used commercially, are known to limit the system’s maximum data rate. Such a limitation is conventionally treated by two methods: either adding a blue filter at the receiver or using orthogonal frequency multiplexing (OFDM) digital modulation technique. Adding a blue filter at the receiver is controversial in current literature and claimed to decrease the signal-to-noise-ratio (SNR) or to be inefficient if OFDM is employed. Hence, in this work, we experimentally evaluate the above OFDM based VLC system with and without a blue filter. Results are compared to prove that adding a blue filter at the receiver boosts SNR and bit-error-rate (BER) values. This, in turn, helps maximize the data rates supported by such systems. The addition of a blue filter is tested with different modulation techniques. Results in this work remove the controversy around employing a blue filter in OFDM based VLC systems with phosphor-coated white LEDs. Improved BERs and SNRs at high data rates are observed. Specifically, this experimental work demonstrates a BER enhancement of ～40% and ～15% for data rates up to 12 Mbps when a blue filter is added.
关键词： phosphor LEDs,OFDM,experimental study,VLC,blue filters
更新于2025-09-11 14:15:04
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P‐6.7: Investigation of Full‐Color Solutions for Micro‐LED Display
摘要： Micro-LED is considered as the next generation display technology and has got the attention of many research groups and companies in the world. It is a kind of display consists of microscopic LEDs integrated on driving circuit. And it has many advantages such as high brightness, low power consumption, quick response, wide viewing angle, self-emitting, long lifetime, good contrast, and due to its micro size, it has extremely high resolution which is really suitable for micro-display like VR and AR. However, there are still some problems need to be solved before it widely used in display market. In today's trend of pursuing colorization high resolution and high contrast ratio in display field, achieving high quality and high efficiency full- color display is one of the most important challenge for Micro- LED applications. In this paper, several feasible techniques of full-color Micro-LEDs are investigated.
关键词： quantum dot,micro-display,phosphor,Micro-LED,RGB,full-color display
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE 9th International Nanoelectronics Conferences (INEC) - Kuching, Malaysia (2019.7.3-2019.7.5)] 2019 IEEE 9th International Nanoelectronics Conferences (INEC) - Dependence of operating conditions on lifetime of Phosphor Quantum dots-based white LEDs
摘要： Lifetime of packaged Phosphor- Quantum dot (QDs) based white LEDs is studied. Various stress parameters such as blue light luminance, temperature and moisture are considered and their effect on the performance of the Phosphor- QD based LED is investigated. The lumen degradation rate and degradation trend for LEDs is observed to be different under varying stress conditions. Lumen recovery process is also observed under light stress test.
关键词： down conversion,Light emitting diodes,Quantum dot,lifetime,Phosphor
更新于2025-09-11 14:15:04
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Facile synthesis of the desired red phosphor Li <sub/>2</sub> Ca <sub/>2</sub> Mg <sub/>2</sub> Si <sub/>2</sub> N <sub/>6</sub> :Eu <sup>2+</sup> for high CRI white LEDs and plant growth LED device
摘要： The red emission with suitable peak wavelength and narrow band is acutely required for high color rendering index (CRI) white LEDs without at the cost of the luminous efficacy. Herein, the Li2Ca2Mg2Si2N6:Eu2+ red phosphor was prepared with facile solid-state method using Ca3N2, Mg3N2, Si3N4, Li3N, and Eu2O3 as the safety raw materials under atmospheric pressure for the first time, which shows red emission peaking at 638 nm with full width at half maximum (FWHM) of 62 nm under blue light irradiation and becomes the desired red phosphor to realize the balance between luminous efficacy and high CRI in white LEDs. The morphology, structure, luminescence properties, thermal quenching behavior, and chromaticity stability of the Li2Ca2Mg2Si2N6:Eu2+ phosphor are investigated in detail. Concentration quenching occurs when the Eu2+ content exceeds 1.0 mol%, whereas high temperature photoluminescent measurements show a 32% drop from the room temperature efficiency at 423 K. In view of the excellent luminescence performances of Li2Ca2Mg2Si2N6:Eu2+ phosphor, a white LEDs with CRI of 91 as a proof-of-concept experiment was fabricated by coating the title phosphor with Y3Al5O12:Ce3+ on a blue LED chip. In addition, the potential application of the title phosphor in plant growth LED device was also demonstrated. All the results indicate that Li2Ca2Mg2Si2N6:Eu2+ is a promising red-emitting phosphor for blue-LED-based high CRI white LEDs and plant growth lighting sources.
关键词： Li2Ca2Mg2Si2N6:Eu2+,high CRI white LEDs,plant growth LED device,phosphor
更新于2025-09-11 14:15:04