White LED Light Research Articles

Development of a novel WO3 self-powered electrochromic window technology with a self-rechargeable battery application (ChromoVolt)

For zero-energy buildings, electrochromic smart windows are one of the most essential components, but the external power demand makes this purpose ambiguous. Here, we report a self-powered electrochromic smart window (ECSW) operated by internal electrochemical voltage (chromoVolt). This WO3-based ECSW provides a unique structured device as the 2 mm width Al strip (counter electrode) is placed at one side, making the total window transparent from the front or back point. The WO3 working electrode was fabricated by the large-scale roll-to-roll (R2R) slot-die wet coating method. This device goes into coloured (blue) or bleached (transparent) states spontaneously simply by connecting and disconnecting WO3 and Al electrodes respectively. Going into a deep blue stable-colored state takes approximately 2 min and shows a maximum 56.5 % transmittance change at 600 nm wavelength. Also, this ECSW can provide output potential through internal chemical reactions in a transparent state and can be charged up through disconnection: a self-rechargeable transparent battery application. Three small cells of an active area of 30 mm × 15 mm each provide an output voltage of around 3 V and can power up a small white LED light for up to 1 h. All these phenomena make this electrochromic smart window perfect for a zero-energy building.

Ce/Mn/Cr: (Re,Y)3Al5O12 Phosphor Ceramics (Re = Gd, Tb and Lu) for White LED Lighting with Significant Spectral Redshift and Improved Color-Rendering Index.

In order to attain phosphor ceramics with a high Color-Rendering Index (CRI), samples with the composition of Y0.997-xRexCe0.003)3(Al0.9748 Mn2+0.024Cr3+0.0012)5O12(Rex = 0, Gd0.333, Gd0.666, Gd0.997, Tb0.333, Tb0.666, Tb0.997 and Lu0.997 were prepared by solid-state reaction and vacuum sintering, and exhibited potential for high-quality, solid-state lighting. Doping with Cr3+ and Mn2+ effectively enhanced the red component of Ce3+ spectra through the intense energy transfer from Ce3+ ions to Mn2+/Cr3+ ions. The crystal field splitting of [GdO8] and [TbO8] was more extensive than that of [YO8], causing a massive redshift in the Ce3+ emission peaks from 542 to 561 and 595 nm, while [LuO8] had an opposite effect and caused a blueshift with a peak position at 512 nm. White LED devices incorporating Ce/Mn/Cr: (Gd0.333Y0.664)3Al5O12 phosphor ceramic exhibited a high CRI of 83.97, highlighting the potential for enhancing the red-light component of white LED lighting.

Highly efficient blue‐emitting phosphor via charge compensation strategy and its application for white LED lighting

AbstractHighly efficient phosphors are indispensable for near‐ultraviolet (n‐UV) pumped white light emitting diodes (WLEDs). In this work, a novel blue emitting Sr6GdSc(BO3)6:0.08Ce3+ phosphor was synthesized, exhibiting a broadband blue emission (full width at half‐maximum (FWMH) = 133 nm) excited by 375 nm. Furthermore, the blue emission of Sr6GdSc(BO3)6:0.08Ce3+ was enhanced by 3.9 times through codoping Na+ ions due to the influence of charge compensation and micromorphology and size of phosphor particles. At the same time, the internal quantum efficiency was improved from 45.4% to 98.6% and the external quantum efficiency up to 75.0%. Finally, the 365 nm excited two WLED devices were constructed by integrating Sr6GdSc(BO3)6:0.08Ce3+, Sr6GdSc(BO3)6:0.08Ce3+,0.08Na+, commercial green and red phosphors with high color rendering index. These results reveal that the phosphors have prospective application in high‐quality warm white lighting.

Selective Passivation of Surface toward Bright Yellow Defective Emission of CdS Quantum Dots.

CdE (E = S, Se) quantum dots (QDs) with a broad and large Stokes shift PL emission have emerged as potential materials for white-light LEDs. However, this surface-related emission of nanocrystals is currently limited by low quantum efficiency. Herein, a convenient noninjected one-pot method at a relatively low temperature to prepare CdS QDs was readily achieved. The CdS-368 QD displays intense broad yellow emission in both solution and the solid state at room temperature. The coligation of organic and inorganic ligands passivates the electron trap states at the QD surface and suppresses nonradiative recombination, which is responsible for the high stability of colloids in organic solvents and the distinct fluorescence quantum yield.

Modulation of perovskite degradation with multiple-barrier for light-heat stable perovskite solar cells

The long-term stability of perovskite solar cells remains one of the most important challenges for the commercialization of this emerging photovoltaic technology. Here, we adopt a non-noble metal/metal oxide/polymer multiple-barrier to suppress the halide consumption and gaseous perovskite decomposition products release with the chemically inert bismuth electrode and Al2O3/parylene thin-film encapsulation, as well as the tightly closed system created by the multiple-barrier to jointly suppress the degradation of perovskite solar cells, allowing the corresponding decomposition reactions to reach benign equilibria. The resulting encapsulated formamidinium cesium-based perovskite solar cells with multiple-barrier maintain 90% of their initial efficiencies after continuous operation at 45 °C for 5200 h and 93% of their initial efficiency after continuous operation at 75 °C for 1000 h under 1 sun equivalent white-light LED illumination.

Comparison of Policosanol Profiles of the Sprouts of Wheat Mutant Lines and the Effect of Differential LED Lights on Selected Lines.

Policosanols (PCs) are long-chain linear aliphatic alcohols that are present in the primary leaves of cereal crops, such as barley and wheat, sugar cane wax, and beeswax. PCs have been used as a nutraceutical for improving hyperlipidemia and hypercholesterolemia. However, the PC content in mutant wheat lines has not been investigated. To select highly functional wheat sprouts with a high content of PCs in wheat mutant lines developed via gamma-irradiated mutation breeding, we cultivated the sprouts of wheat mutant lines in a growth chamber with white LED light (6000 K) and analyzed the PC content in these samples using GC-MS. We studied the PC content in 91 wheat sprout samples: the original variety (Woori-mil × D-7; WS01), commercially available cv. Geumgang (WS87) and cv. Cheongwoo (WS91), and mutant lines (WS02-WS86 and WS88-WS90) developed from WS01 and WS87. Compared to WS01, 18 mutant lines exhibited a high total PC content (506.08-873.24 mg/100 g dry weight). Among them, the top 10 mutant lines were evaluated for their PC production after cultivating under blue (440 nm), green (520 nm), and red (660 nm) LED light irradiation; however, these colored LED lights reduced the total PC production by 35.8-49.7%, suggesting that the cultivation with white LED lights was more efficient in promoting PCs' yield, compared to different LED lights. Therefore, our findings show the potential of radiation-bred wheat varieties as functional foods against hyperlipidemia and obesity and the optimal light conditions for high PC production.

Effects of different visible light spectrums on phototaxis and bottom preference behavior of sea cucumber

In recent years, studies have shown that different light wavelengths have varying effects on aquaculture species. This indicates that exposure to light can significantly influence the health and development of aquatic organisms. This study investigated the effects of different visible light spectra on the behavior and physiological responses of sea cucumbers. Under blue LED and white LED illumination, the sea cucumbers exhibited shelter-seeking behavior. A phototaxis experiment found that the blue LED light elicited the strongest negative phototaxis, followed by the white LED. However, the red LED light elicited no obvious response. In the bottom zone preference experiment, blue LED and white LED illumination affected the bottom preference behaviors of some individuals compared to the control group. By measuring the mean photon flux density (MPFD) values at different illumination distances, the individuals in each group tended to stop moving when they were close to a similar MPFD value. Next, this study examined the physiological effects of red LED and blue LED illumination on sea cucumbers. Interestingly, the blue LED group exhibited higher oxygen consumption rates and thinner connective tissue in the respiratory tree during the early stage of the experiment. In contrast, no significant differences in coelomocyte phagocytosis were observed between the blue LED and red LED groups. Our findings suggested that the behaviors and physiological responses elicited by the blue or white LED light are likely caused by the number of photons in a specific time and area received by photoreceptors on the integument of sea cucumbers. Furthermore, neither long- nor short-wavelength spectra caused significant stress or damage to sea cucumbers in this study. The results obtained from this data will be beneficial for lighting usage in aquaculture environments in the future.

Cyan luminescence from Bi ions-doped borosilicate glass induced by the gradual substitution of MO (M=Ca, Sr, Ba)

At present, amorphous glasses that can give blue light, green light, and yellow light emission upon ultraviolet excitation have achieved good commercial prospect, but lacking of the high-efficiency cyan luminescence is still a challenging problem. To fill the lack of cyan light emission in the current white light LED technology spectrum excited by ultraviolet light, the effect of the substitution of CaO for SrO and BaO, and that of SrO for BaO on the optical properties, structure, DSC, and CIE (Commission International de L'Eclairage) coordinates of Bi ions-doped borosilicate glasses were systematically studied in this work. The emission spectra results reveal that the emission position of Bi ions-doped borosilicated glasses is observed from 482 nm to 492 nm when CaO is gradually replaced by SrO, from 482 nm to 502 nm when CaO is gradually replaced by BaO. In one word, the luminescent peak position of the Bi ions-doped borosilicate glass can be easily tuned by altering the concentration of basicity-earth oxide modifier, and the cyan light emission can be finally achieved.

The Effect of Light Quality and Intensity on <em>in vitro</em> Potato Cultures

Purpose: The study investigates the effect of light quality and intensity factors on in vitro potato meristem cultures and multiplication for optimization of pre-basic seed potato productions of some potato varieties.Research Method: In vitro experiments were conducted to study the response of meristems and nodal cuttings of five potato varieties, i.e., Cara, Hermes, Lady Rosetta, Santana, and Spunta, to four LED light qualities (blue, red, red+blue, or white) for five potato varities. Also, the response of nodal cuttings was examined under three light intensities (50, 75 and 100 μmol m-2 s-1).Findings: Significant differences were obtained between the four tested light qualities. Red LED gave the best meristem survival rates of the Cara, Hermes, Lady Rosetta, and Spunta potato varieties. In the multiplication phase, a significantly (p ≤ 0.05) higher plantlet length was obtained from nodal cuttings under red light quality. Also, white and red light produced vigorous plantlets, expressed as higher significant dry weight (82.2 and 80.4 mg/plantlet, respectively). Increasing light intensity from 50 to 75 and 100 μmol m-2 s-1 resulted in increases in leaf number, stem diameter, root length, leaf area, chlorophyll content, fresh weight, and dry weight.Originality/value: White LED light quality enhanced in vitro initiation of potato meristems. Furthermore, Light intensity of 75 μmol m-2 s-1 gave better performance of potato plantlets in vitro.

UV-converted heterogeneous wettability surface for the realization of printed micro-scale conductive circuits

Achieving high precision in the fabrication of electronic circuits through additive manufacturing requires breaking the resolution limit of traditional printing processes. To address this challenge, we have developed a novel approach that involves preparing a heterogeneous wetting surface using a light-sensitive NBE-acrylate resin. By creating differences in surface energy on the substrate, we can limit the spread of the ink and surpass the limitations of conventional processes, achieving a printing resolution of 5 μm. The NBE-acrylate resin can be cross-linked under white LED light illumination (with λ > 400 nm) to yield a hydrophobic surface, which can be converted to a hydrophilic surface by UV light illumination (λ = 254 nm). The photochemical reaction of the NBE-acrylate resin under different light irradiation was confirmed by Fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM) microforce measurements. In combination with a photomask, patterned heterogeneous wettability surfaces were prepared, which can be utilized for printing precision electronic circuits. Micrometer-scale printed circuits with a low line-to-space (L/S) of 5/50 and 10/10 μm were successfully achieved by optimizing the ink formulation, which is significantly beyond the printing resolution. In the end, fully printed thin film transistor arrays based on semi-conducting carbon nanotubes were achieved, which showed higher charge carrier mobilities of 1.89–4.31 cm2 s−1 V−1 depending on the channel width, demonstrating the application of this precision printed technique.

LED Lights Influenced Phytochemical Contents and Biological Activities in Kale (Brassica oleracea L. var. acephala) Microgreens.

Light-emitting diodes (LEDs) are regarded as an effective artificial light source for producing sprouts, microgreens, and baby leaves. Thus, this study aimed to investigate the influence of different LED lights (white, red, and blue) on the biosynthesis of secondary metabolites (glucosinolates, carotenoids, and phenolics) and the biological effects on kale microgreens. Microgreens irradiated with white LEDs showed higher levels of carotenoids, including lutein, 13-cis-β-carotene, α-carotene, β-carotene, and 9-cis-β-carotene, than those irradiated with red or blue LEDs. These findings were consistent with higher expression levels of carotenoid biosynthetic genes (BoPDS and BoZDS) in white-irradiated kale microgreens. Similarly, microgreens irradiated with white and blue LEDs showed slightly higher levels of glucosinolates, including glucoiberin, progoitrin, sinigrin, and glucobrassicanapin, than those irradiated with red LEDs. These results agree with the high expression levels of BoMYB28-2, BoMYB28-3, and BoMYB29 in white- and blue-irradiated kale microgreens. In contrast, kale microgreens irradiated with blue LEDs contained higher levels of phenolic compounds (gallic acid, catechin, ferulic acid, sinapic acid, and quercetin). According to the total phenolic content (TPC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition assays, the extracts of kale microgreens irradiated with blue LEDs had slightly higher antioxidant activities, and the DPPH inhibition percentage had a positive correlation with TPC in the microgreens. Furthermore, the extracts of kale microgreens irradiated with blue LEDs exhibited stronger antibacterial properties against normal pathogens and multidrug-resistant pathogens than those irradiated with white and red LEDs. These results indicate that white-LED lights are suitable for carotenoid production, whereas blue-LED lights are efficient in increasing the accumulation of phenolics and their biological activities in kale microgreens.

White-light emitting BaAl2O4/CaAl4O7:x% Dy3+ (0 ≤ x ≤ 3) mixed phase nanophosphors synthesized using citrate sol-gel method

Novel mixed phase BaAl2O4/CaAl4O7 (BC) and BC: x% Dy3+ (0 ≤ x ≤ 3) nanophosphors were synthesized by the citrate sol-gel method. The morphology changed as x%Dy3+ varied. The patterns showed that the BC nanophosphors matched well with the monoclinic CaAl4O7 and hexagonal BaAl2O4 structures. Moreover, the structure of BC was not influence by the dopant. The dopant is mainly located in the BaAl2O4 phase. The crystallite sizes were estimated to be in the nanoscale order. The photoluminescence (PL) results showed that the emission was quenched for BC: x% Dy3+ (x > 2.4) be due to the quadrupole-quadrupole interaction. The emission peaks at 325, 482 and (563 and 576) nm were assigned to the bandgap defects of BC, 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. The International commission on illumination (CIE) showed the dopant (Dy3+) had changed the emission color from blue to white. This showed that the BC: x% Dy3+ (1.2 ≤ x ≤ 3) nanophosphors were potential candidates for white-light LEDs.

Luminescence Studies on Dy3+ Doped Calcium Aluminum Borosilicate (CABS) Glasses for White Light Emission and Applications in w-LEDs.

Dy3+ doped calcium aluminum borosilicate (CABS) glasses have been synthesized via quick melt quench technique. CABS: xDy3+ glasses (x = 0.1, 0.5, 1, 1.5 and 2mol%) were subjected to various morphological and photoluminescence studies. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were conducted to study the structural and bonding nature of the undoped glass. The excitation spectra of Dy3+ doped CABS glasses under 574nm emission show many sharp peaks amongst which the transition from 6H15/2 → 6P7/2 (351nm) had the highest intensity. Under 351nm excitation, glasses exhibit sharp peaks in the blue, yellow and red regions corresponding to the transitions 4F9/2 → 6H15/2, 6H13/2, 6H11/2 and 6H9/2 respectively. The dipole-dipole nature of the interaction between the Dy3+ ions is confirmed via Dexter theory and Inokuti-Hirayama (I-H) model. CIE coordinates estimated from the emission profiles of these glasses under 351nm excitation fall in the white region. Considering that these glasses exhibit sharp visible emission under UV excitation, have stable yellow to blue (Y/B) ratios and fast decays with intense energy transfers, we propose to utilise these glasses for white light generation and other white light LED (w-LED) and solid-state lighting (SSL) applications.

Multi-Mode Photoluminescence Regulation in a Zero-Dimensional Organic-Inorganic Hybrid Metal Halide Perovskite─[(CH3)4N]2SnCl6.

Metal ion-doped zero-dimensional halide perovskites provide good platforms to generate broadband emission and explore the fundamental dynamics of emission regulations. Recently, Sb3+-doped zero-dimensional halide perovskites have attracted considerable attention for the high quantum yield of yellow emission; however, the triplet state recombination is activated and the singlet state emission is usually absent. Herein, we fabricate an Sb3+-doped zero-dimensional [(CH3)4N]2SnCl6 perovskite that can induce singlet and triplet emission. Density functional theory calculation shows that there are some overlaps between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals, which may induce a large energy separation between the lowest excited triplet states (T1) and the lowest excited singlet states (S1) [ΔE(S1 - T1)], impeding all the carriers' transfer from the singlet state to the triplet state. As a result, the reserved singlet emission together with the triplet emission can be regulated by excitation wavelength in situ. In addition, different Bi3+ ratios are co-doped into Sb3+@[(CH3)4N]2SnCl6, resulting in a photoluminescence ex situ regulation. Single-phase white light LED and optical anti-counterfeiting are developed further.

Synthesis of silicate clay minerals-based novel Mt/YF3:Eu3+ nanocomposites for regulated luminescent intensity-quantum yield-fluorescence lifetime

Rare earth luminescent materials have broad application prospects in the fields of white light LED lighting, flat panel display, biological imaging and so on. Here, we developed a novel silicate clay minerals-based montmorillonite nanosheet(Mt)/YF3:Eu3+ nanocomposites with strong luminescence performance. Mt carrier plays a three role: (1) reducing the size and improving dispersion of YF3: Eu3+ nanoparticles by surface effect; (2) narrowing down the band gap and increasing Urbach tail energy by interface effect; (3) reducing the shielding of the hole-electron Coulomb interactions while improving the exciton binding energy of YF3:Eu3+, thus improving the radiative recombination by dielectric effect. Therefore, orthogonal phase YF3: Eu3+ nanoparticles (diameter 20∼140 nm) binding to the surface of Mt via chemical bond interactions. The combination of Mt and YF3:Eu3+ not only enhanced luminescent intensity (about 2 times) but also improved the quantum yield (0.14% to 0.4%) and fluorescence lifetime (0.338 ns to 0.405 ns) of YF3:Eu3+ nanoparticles at 595 nm. In addition, the combination of Mt and YF3:Eu3+ give luminescent properties to Mt thereby improving the utilization rate of Mt and YF3: Eu3+ nanoparticles. It was found that the research supplies an insight on the development of new type luminescent materials, and hopefully it could promote them application in many fields.

Thiogallate phosphor for white LEDs with water-resistance and green light-emitting capability

The application of sulfide phosphor in the field of phosphor-converted white light-emitting diodes (pc-WLEDs) and wide-gamut displays has been limited by its poor water resistance. Herein, a water-resistant green emission phosphor, LiGaS2:Eu2+ (LGSE), has been developed using a chalcogenometallate LiGaS2 (LGS) as the luminescent host. First-principles calculation was utilized to identify the electronic structure of LGS and the optimal site for the Eu2+ dopant. Upon stimulation by 450 nm light, the LGSE phosphor exhibits a brilliant green emission with a photoluminescence emission (PL) maximum at 544 nm and a quantum efficiency of 55.3%. The exceptional luminance characteristics of this green-emitting phosphor were revealed by diffuse reflection spectra, steady-state PL spectra, and temperature-dependent PL measurements. The LGSE phosphor retains at least 94% of its initial emission even after 20 days of water immersion. The integration of LGSE with a commercial red-emitting K2SiF6:Mn4+ phosphor on a 450 nm blue LED chip produced a warm white light LED device, in which the color rendering index was Ra = 80.3 and CCT = 5128 K. This development represents a significant advancement in the field of water-resistant sulfide phosphors.

Skin-color-independent robust assessment of capillary refill time.

Capillary Refill Time (CRT) assesses peripheral perfusion in resource-limited settings. However, the repeatability and reproducibility of CRT measurements are limited for individuals with darker skin. This paper presents quantitative CRT measurements demonstrating good performance and repeatability across all Fitzpatrick skin phototypes. The study involved 22 volunteers and utilized controlled compression at 7 kPa, an RGB video camera, and cocircular polarized white LED light. CRT was determined by calculating the time constant of an exponential regression applied to the mean pixel intensity of the green (G) channel. An adaptive algorithm identifies the optimal regression region for noise reduction, and flags inappropriate readings. The results indicate that 80% of the CRT readings fell within a 20% range of the expected CRT value. The repetition standard deviation was 17%. These findings suggest the potential for developing reliable and reproducible quantitative CRT methods for robust measurements in patient triage, monitoring, and telehealth applications.

Intense green light emission in Sr2 ZnGe2 O7 :Mn2+ phosphors by the design of high symmetry melilite structure.

A green phosphor Sr2 ZnGe2 O7 :Mn2+ with a melilite structure was prepared using a high-temperature solid-state reaction. When the 535 nm emission was monitored, the excitation spectrum of the Sr2 ZnGe2 O7 :Mn2+ was found to contain two excitation bands in the ultraviolet (UV) region. When excited by UV light, the sample shows bright green emission at 535 nm, which corresponds to the distinctive transition of Mn2+ (4 T1 →6 A1 ). Moreover, the quantum efficiency of Sr2 ZnGe2 O7 :Mn2+ could reach 67.6%. Finally, a high-performance white-light-emitting diode (WLED) with a low correlated colour temperature of 4632 K and a high colour rendering index (CRI) of 92.3 were packaged by coating commercial blue and red phosphors with an optimized Sr2 ZnGe2 O7 :Mn2+ sample on a 310 nm UV chip. This indicated that Sr2 ZnGe2 O7 :Mn2+ has the potential application as a green component in the WLED lighting field.

Kajian Penggunaan LED pada Pertumbuhan Tanaman Kailan dengan Sistem Hidroponik Dalam Ruangan

The use of LED (Light Emitting Diode) in indoor hydroponic systems can optimize the process of photosynthesis in plants. This can be a replacement of sunlight during plant growth. This study aims to examine the treatment of LED light intensity and duration of irradiation on the vegetative growth of kailan (Brassica oleracea var. alboglabra L) in indoor hydroponic systems. This experimental study consisted of 5 treatments: exposure to white (A1) and blue (A2) LED lights, exposure time of 16 hours (B1) and 20 hours (B2) and sunlight (K0) as a control in a greenhouse. Treatment with LED lights placed in the growth chamber. Treatment consisted of 4 replicates with a total of 20 plants. The results showed that the white LED light intensity and 20 hours of irradiation time were better than other treatments including plant height, stem diameter, leaf width, leaf length, number of leaves, fresh weight, root weight and water efficiency.

White LED Lighting Increases the Root Productivity of Panax ginseng C. A. Meyer in a Hydroponic Cultivation System of a Plant Factory.

To identify effective light spectra for increasing the productivity of Panax ginseng, we conducted experiments in a controlled environment using a hydroponic cultivation system in a plant factory. We investigated the effect of single LEDs (red, blue, and yellow) and mixed LEDs (red + blue and red + blue + white). The relationships between four light spectra (red, blue, yellow, and white) and physiological responses (net photosynthetic rate, stomata conductance, transpiration rate, and intercellular CO2 partial pressure), as well as growth responses (shoot and root biomass), were analyzed using multivariate statistical analysis. Among the four physiological response variables, shoot biomass was not increased by any pathway, and root biomass was increased only by the intercellular CO2 partial pressure. Red and yellow light increased shoot biomass, whereas white light promoted an increase in the net photosynthetic rate and enhanced root biomass. In contrast, blue light was less effective than the other light spectra in increasing both shoot and root biomass. Therefore, red and yellow light are the most effective light spectra for increasing shoot biomass and white light is effective for increasing root biomass in a plant factory that uses artificial LED lighting. Furthermore, the intercellular CO2 partial pressure is an important physiological variable for increasing the root biomass of P. ginseng.