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Broad-band emission and color tuning of Eu3+-doped LiCa2SrMgV3O12 phosphors for warm white light-emitting diodes
摘要： In this study, series of Eu3+-doped LiCa2SrMgV3O12 (LCSMV) phosphors with broad-band emission and color tunable feature were prepared via solid phase reaction. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results presented a pure cubic phase product with micron-sized and homogeneous distribution of element. Their spectroscopic properties were investigated systematically by photoluminescence excitation (PLE) and emission (PL) spectra, temperature-dependent PL spectra and luminescence decay curves. The LCSMV phosphors displayed a strong absorption to ultraviolet light and a broad cyan emission. Moreover, in Eu3+-doped LCSMV phosphors, Eu3+ ion characteristic emissions at 589, 610, 651 and 705 nm, attributing to the 5D0→7F1, 7F2, 7F3 and 7F4 transitions, were observed. Along with Eu3+ ion concentrations increasing, the emission colors could be readily tuned from cyan to orange and the decay lifetimes of (VO4)3- became shorter. Meanwhile, electric dipole-dipole interaction was responsible to energy migration from (VO4)3- groups to Eu3+ ions. Further, the quantum efficiency (QE) values were estimated to be 32.5% for LCSMV host and 39.3% for LCSMV: 0.01Eu3+ sample. Finally, a LED lamp was prepared by integrating the blend of the LCSMV: 0.01Eu3+ phosphors and commercial blue-emitting BaMgAl10O17:Eu2+ phosphors with NUV chip (365 nm) and exhibited warm white light (CCT = 3655 K, Ra = 90), which may be applied in lighting and display field.
关键词： Self-activated luminescence,Color tunable,Light-emitting diode,Vanadate phosphor,Color rendering index,Broad-band emission
更新于2025-11-20 15:33:11
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S, N-codoped Oil-soluble Fluorescent Carbon Dots for High Color-rendering WLED
摘要： Carbon dots (CDs) have attracted widespread attention in light-emitting-diode (LED) applications owing to their environmental friendliness, easy processing and unique optical properties. For the practical use of CDs in LEDs, the controllable synthesis of high performance oil-soluble carbon dots are still in urgent demand. In this study, S, N-codoped oil-soluble carbon dots (S, N-OCDs) with average size of 3.38 nm were prepared by solvothermal reaction of acetone, dimethyl trithiocarbonate (DMTTC) and nitric acid. Characterization results reveal that both the conjugated aromatic π systems from aldol condensation and highly active free radicals from DMTTC essentially dominate the development of this yellow-green emitting S, N-OCDs which possess high carbonization, quantum yield (21.08 %) and oil-solubility. Furthermore, a white light-emitting-diode (WLED) was fabricated through mixing the obtained S, N-OCDs and epoxy and drop-casting the mixure on the surface of gallium nitride (GaN) based blue chips. The as-prepared WLED showed excellent color rendering properties (CCT of 5389 K, CIE coordinates of (0.33,0.30), CRI of 88.38).
关键词： oil-soluble carbon dots,color rendering index,WLED,heteroatom doping
更新于2025-11-19 16:46:39
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Color Rendition of Artificial Light Sources: Past and Future
摘要： During last decade it is visible new impulse in case of color quality evaluation of artificial light sources. New ideas are based on criticism of CIE color rendering index Ra that appears insufficient especially for solid state light sources, nevertheless proposed metrics aren’t broadly accepted. In this article is presented short overview of color rendering indices history with discussion about possible improvement of CIE color rendering index by gamut mapping.
关键词： color,TM 30-15,colorimetry,light source,color rendering index
更新于2025-09-23 15:21:21
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - The Uncertainty of Measurement of Spectroradiometric System with Double Monochromator
摘要： This article has task to inform a reader about uncertainties of measurement of spectroradiometric systems with double monochromator. Uncertainty of measurement is very important for all photometric measurements and calculations. Spectroradiometric system’s uncertainty is dependent on wavelength and is difficult to estimate uncertainty of measurement for photometric parameters calculated from measured spectrum. In the first part of this article there is theory necessary for understanding uncertainty analyses and description of construction of spectroradiometric system with double monochromator. In the second part there is practical uncertainty analysis of double monochromator in light laboratory and its results.
关键词： spectral irradiance,correlated color temperature,double monochromator,color rendering index,Uncertainty of measurement
更新于2025-09-23 15:21:21
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Tuning phosphors for better white light
摘要： Light-emitting diodes (LEDs) that produce white light are about to take over the lighting world. The U.S. market share of these super-long-lasting, cool-to-the-touch lights, which use less than a quarter of the energy of conventional incandescent bulbs, sits around 10%. Industry watchers predict that number will exceed 80% by 2030, reducing power consumption in the U.S. by 40%. Chemists are taking a leading role in this technology, which underpins general lighting and electronic displays, by customizing the emission spectrum, stability, and other properties of inorganic phosphors in the LEDs that help produce finely tuned white light.
关键词： energy efficiency,inorganic phosphors,color rendering index,LEDs,white light
更新于2025-09-23 15:21:21
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Full-visible-spectrum lighting enabled by an excellent cyan-emitting garnet phosphor
摘要： The development of phosphor materials with outstanding photoluminescence properties is critical for next-generation high-quality solid-state white lighting. As there is a blue-green cavity existed in the emission spectra of the traditional phosphor-converted white-light-emitting diodes (w-LEDs), cyan-emitting phosphor serves an important function in compensating the spectral gap to realize the “full-visible-spectrum lighting”. Herein, we reported the discovery of an efficient cyan-emitting Ce3+-doped Ca2YHf2Al3O12 (CYHAO) garnet phosphor with good thermal stability. The as-prepared CYHAO:Ce3+ phosphor exhibited a broad excitation band in the range of 360 to 460 nm with a maximum at 408 nm, making this phosphor compatible with an efficient 400 nm NUV-emitting LED chip. Under the 408 nm excitation, the optimal sample of CYHAO:0.03Ce3+ exhibited bright broadband cyan emission (λem = 493 nm; bandwidth = 100 nm) together with extra-high internal quantum efficiency (IQE) of 89.5% and external quantum efficiency (EQE) of 69.1%. Notably, the as-prepared CYHAO:0.03Ce3+ phosphor showed good thermal stability (64.2% of emission intensity retained at 423K) and excellent color stability when working in the temperature range of 303-463 K. Importantly, the constructed w-LED device exhibited bright well-distributed warm white light with high color rendering index (CRI; Ra = 93.5 and R12 = 90.4) and low correlated color temperature (3700 K) under 60 mA driven current, indicating that the title cyan phosphor can be utilized as the compensation of the blue-green cavity to apply in full-visible-spectrum lighting. Furthermore, these findings provide new insights into exploring high-performance cyan phosphors for NUV-pumped high-CRI warm w-LEDs.
关键词： White LEDs,Color rendering index,Cyan emissions,Phosphors,Full-visible-spectrum lighting
更新于2025-09-23 15:21:01
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High color rendering index white light-emitting diode based on enviromental friendly carbon and AIZS nanoparticles
摘要： Solid-state white light-emitting diodes (WLEDs) based on carbon dots (CDs) have attracted broad attention due to their high brightness and enviromental friendly. However, the poor performance including low efficiency and weak emission of red-emitting CDs further hindered its application on WLED devices. Herein, we constructed one outstanding WLEDs device by combining carbon dots (blue emission, green emission) and Ag-In-Zn-S (AIZS) nanoparticles with red emission. Moreover, by adjusting the volume ratio of the three materials, the WLED showed maximum color rendering index (CRI) of 97 and maintained CRI value above 90 during the correlated color temperature (CCT) tuned from 3387 to 8018 K. Meanwhile, the as-fabricated WLED devices showed excellent color rendering stability during the working voltages from 3.0V to 3.5V. This work may provide one new avenue for development of low-cost, environmental friendly and high-performance CDs phosphor-based WLEDs.
关键词： AIZS nanoparticles,color rendering index,white light-emitting diode,carbon dots,environmental friendly
更新于2025-09-23 15:21:01
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Numerical Prediction and Experimental Validation of Multiple Phosphor White LED Spectrum
摘要： White LEDs with single phosphor usually have poor color rendering capability. The emission spectra of the blue LED and the yellow phosphor are narrow as compared with the reference light sources. The red light output is particular low. The color of the objects illuminated by such light source appear not accurate nor natural. Though the luminous efficiency is high, such poor color rendering light sources are not suitable for most general lighting applications. To improve the color rendering properties, multiple phosphors with different emission spectra should be used. For instance, a certain amount of red or orange phosphors may be used to mix with yellow phosphor to broaden the overall spectrum. In this paper, a numerical model is proposed to predict the emission spectra of LEDs with multiple phosphors. The model has considered the excitation and emission spectra of the phosphors, the mixing ratio and re-absorption between the phosphors. To validate the model, white light LEDs with multiple phosphors are fabricated. The spectra are measured and compared with the modeling results. It is found that the proposed model can estimate the emission spectra of LEDs with multiple phosphors with a high degree of accuracy.
关键词： Color Rendering,Spectrum Prediction,Phosphor Characterizations,White Light LED,Multiple Phosphors
更新于2025-09-19 17:13:59
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Recorded color rendering index in single Ce,(Pr,Mn):YAG transparent ceramics for high-power white LEDs/LDs
摘要： Transparent ceramic (TC) is an incredibly promising color converter for high-power white LEDs/LDs. However, the preparation process of multiple structured TC with high color rendering index (CRI) is complicated and of technical challenge, and the inability of a single structured TC to achieve a high CRI significantly limits its real application. In this study, high quality single structured Ce,(Pr,Mn):YAG TCs with the 'wide peak' and 'narrow peak' red light emission were designed and fabricated by the solid-state reaction and vacuum sintering method. Compared with the emission spectra of the Ce:YAG TC, synchronous doping Pr3+ and Mn2+ ions into Ce:YAG TCs resulted in an inhomogeneous broaden of the full width at half maximum (FWHM) from 91.7 nm to 102.2 nm. Impressively, the CRI of the single Ce,(Pr,Mn):YAG TC based high-power white LEDs was as high as 84.8, and the correlated-color temperature (CCT) of the white LEDs/LDs were 5450 K and 3550 K, respectively. Furthermore, when the addition amounts of Pr3+ and Mn2+ were 0.2 at.% and 0.8 at.%, respectively, the prepared Ce,(Pr,Mn):YAG TC displayed a high quantum efficiency (IQE=48.14%) and an excellent color stability (only 5% fluctuation). Therefore, this work not only shows how to overcome the spectrum deficiencies of single structured TCs that restrains the intrinsic CRI improvement, but also provides a reference for the pursuit of a high luminescent property. It significantly reinforces the understanding of CRI problems of TC based high-power lighting, which is crucial for the real application of white LEDs/LDs.
关键词： color rendering index,Ce,(Pr,Mn):YAG,synchronous doping,high-power white LEDs/LDs,Transparent ceramic
更新于2025-09-19 17:13:59
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Tunable LED Lighting with Five Channels of RGCWW for High Circadian and Visual Performances
摘要： In this study, red, green, cyan, warm white and cool white (RGCWW) LEDs are individually controlled to simulate dynamic daylight. The spectral power distributions (SPDs) are measured for both the daylight and the mixed white light. The correlated color temperature (CCT), circadian action factor (CAF) curves in the daytime of the mixed white LED almost overlap to those of daylight with a small error of about 1%. The CIE chromaticity coordinates of the mixed white light are distributed along the Planckian locus with a little deviation below 0.003. Also, its color rendering index (CRI) is above 90. The RGCWW five-chip LEDs of high circadian and visual performances will benefit to synchronize circadian rhythm in closed environment during long time without daylight, combined with better mood and alertness. The simulation errors and development trend of the mixed lighting are discussed.
关键词： mixed white light,circadian rhythm,circadian action factor,color rendering index,light emitting diode
更新于2025-09-16 10:30:52