• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.4
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• pp.542-550
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• 2014

We investigated biomass, diatom species and fucoxanthin contents as cell growth, fatty acid and amino acid contents as nutritional composition of diatoms attached on plate to confirm effects of light emitting diodes (LEDs) due to block off natural light. In the single LED irradiation, biomass showed significantly higher to $30.0{\pm}6.48mg/m^2$ in white LED than that of others (P<0.05). The dominate diatom species was Navicula cancellata. Their lipid contents showed significantly higher to $112.9{\pm}19.23ug/mg$ dry matter (DM) in control than that of others LEDs. But eicosapetaenoic acid (EPA) contents showed significantly higher to $3.3{\pm}0.62ug/mg$ DM than others, but not significantly differed with natural control light treatment (P<0.05). And total protein contents are higher in control and blue LED light than that of others, but essential amino acid contents showed significantly higher to $3.2{\pm}4.8%$ in control (P<0.05). In mixing light with natural and LED light, biomass showed $2.6{\pm}0.22mg/m^2$ in blue LED (P<0.05). Fatty acids contents were not significantly differed with all treatments. Amino acid contents showed to $11.0{\pm}0.33ug/mg$ DM in white LED (P<0.05), but not significantly differed with others LED lights (P>0.05). Therefore, we could suggest that irradiation of blue LED in natural light very benefit to diatom culture for larvae of sea cucumber and abalone and do on.

• Current Optics and Photonics
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• v.3 no.6
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• pp.485-495
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• 2019

Photobiomodulation (PBM) using organic light emitting diodes (OLEDs) surface light sources have recently been claimed to be the next generation of PBM light sources. However, the differences between light emitting diodes (LEDs) and OLED mechanisms in vitro and in vivo have not been well studied. In vivo mouse models were used to investigate the effects of OLED irradiation on cellular function and cutaneous wound healing compared to LED irradiation. Mice in the LED- and OLED-irradiated groups were subjected to irradiation with 6 J/㎠ LED and OLED (630 nm), respectively, for 14 days after wounding, and some mice were sacrificed for the experiments on days 3, 7, 10, and 14. To evaluate wound healing, we performed hematoxylin-eosin and Masson's trichrome staining and quantified collagen density by computerized image analysis. The results showed that the size of the wound, collagen density, neo-epidermis thickness, number of new blood vessels, and number of fibroblasts and neutrophils was significantly influenced by LED and OLED irradiation. The tissue levels of interleukin (IL)-β, IL-6 and tumor necrosis factor (TNF)-α were investigated by immunohistochemical staining. LED and OLED irradiation resulted in a significant increase in the tissue IL-β and IL-6 levels at the early stage of wound healing (P < 0.01), and a decrease in the tissue TNF-α level at all stages of wound healing (P < 0.05), compared to the no-treatment group. The expression levels of the genes encoding vascular endothelial growth factor and transforming growth factor-beta 1 were significantly increased in LED and OLED-irradiated wound tissue at the early stage of wound healing (P < 0.01) compared to the no-treatment group. Thus, OLED as well as LED irradiation accelerated wound healing by modulating the synthesis of anti-inflammatory cytokines and the expression levels of genes encoding growth factors, promoting collagen regeneration and reducing scarring. In conclusion, this suggests the possibility of OLED as a new light source to overcome the limitations of existing PBMs.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.749-753
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• 2004

In this study, we attempt to synthesize the $Sr_{3}SiO_{5}:Eu$ yellow phosphor by sol-gel technique. Based on the blue emitting diodes as primary light source, white light emitting diodes have been manufactured using the $Sr_{3}SiO_{5}:Eu$ yellow phosphor as the luminescent material. Luminescent efficiency of yellow phosphor as well as that of blue LED is very important factor to enhance the luminescent efficiency of white LED. In order to improve the luminescent efficiency, we have synthesized the $Sr_{3}SiO_{5}:Eu$ phosphor by sol-gel technique. To research optimum condition of gelation reaction, the ratio of $H_{2}O$ to TEOS was fixed as 60:1. When the drying temperature was at $100^{\circ}C$, emission intensity was better than at $70^{\circ}C$. The critical $Eu^{2+}$ concentration was estimated to be about 0.05 mol and sintering temperature at $1300^{\circ}C$ was indicated best emission intensity.

• Current Optics and Photonics
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• v.4 no.4
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• pp.380-390
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• 2020

In this study, the traditional electron-blocking layer (EBL) in (In,Ga)N/GaN light-emitting diodes is replaced by a circular EBL that is the same size as the n-pad. The three-dimensional (3D) nonlinear Poisson, drift-diffusion, and continuity equations are adopted to simulate current transport in the LED and its characteristics. The results indicate that the local carrier-density distribution obtained for the circular EBL design is more uniform than that for the traditional EBL design. This improves the uniformity of local radiative recombination and local internal quantum efficiency (IQE) at high injection levels, which leads to a higher lumped IQE and lower efficiency droop. With the circular EBL, the lumped IQE is higher in the outer active region and lower in the active region under the n-pad. Since most emissions from the active region under the n-pad are absorbed by the n-pad, obviously, an LED with a circular EBL will have a higher external quantum efficiency (EQE). The results also show that this LED works at lower applied voltages.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.59-60
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• 2008

GaN-based light-emitting diodes (LEDs) with ZnO nanorod arrays on a planar indium tin oxide (ITO) transparent electrode were demonstrated. ZnO nanorods were grown into aqueous solution at low temperature of $90^{\circ}C$. Under 20 mA current injection, the light output efficiency of the LED with ZnO nanorod arrays on ITO was remarkably increased by about 40 % of magnitude compared to the conventional LED with only planar ITO. The enhancement of light output by the ZnO nanorod arrays is due to the formation of side walls and a rough surface resulting in multiple photon scattering at the LED surface.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.41-47
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• 2012

The purpose of this study was to determine optimum condition for the cultivation of Chlorella sp. FC-21 using red light emitting diodes (LED). Specific growth rate and cell concentration were measured for the reactors at the illuminations of different light intensity of red LED. Under the illumination of red LED, specific growth rate increased as light intensity increased but cell concentrations decreased. To determine beneficial effect of aeration to cell cultivation, micro-air bubbles were aerated at 0.7 vvm in the reactor at the illumination of red LED. Two and ten times greater specific growth rate and cell concentration were obtained when aeration was applied. In case of blowing of carbon dioxide, pH of culture medium decreased below to pH 3, which resulted in decreases of cell concentration. From this study, we found that red LED with aeration were the most appropriate light source for the cultivation of Chlorella sp. FC-21.

• Korean Journal of Materials Research
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• v.23 no.3
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• pp.177-182
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• 2013

Nanosphere lithography is an inexpensive, simple, high-throughput nanofabrication process. NSL can be done in different ways, such as drop coating, spin coating or by means of tilted evaporation. Nitride-based light-emitting diodes (LEDs) are applied in different places, such as liquid crystal displays and traffic signals. The characteristics of gallium nitride (GaN)-based LEDs can be enhanced by fabricating nanopatterns on the top surface of the LEDs. In this work, we created differently sized (420, 320 and 140 nm) nanopatterns on the upper surfaces of GaN-based LEDs using a modified nanosphere lithography technique. This technique is quite different from conventional NSL. The characterization of the patterned GaN-based LEDs revealed a dependence on the size of the holes in the pattern created on the LED surface. The depths of the patterns were 80 nm as confirmed by AFM. Both the photoluminescence and electroluminescence intensities of the patterned LEDs were found to increase with an increase in the size of holes in the pattern. The light output power of the 420-nm hole-patterned LED was 1.16 times higher than that of a conventional LED. Moreover, the current-voltage characteristics were improved with the fabrication of differently sized patterns over the LED surface using the proposed nanosphere lithography method.

• Research in Plant Disease
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• v.22 no.2
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• pp.100-106
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• 2016

We have studied the mycelia growth of four soil-borne fungal pathogens under light qualities and two lighting types (continuous and intermittent) provided by light-emitting diodes (LEDs). As a result, each mycelia growth on Phytophthora cactorum KACC40166, Athelia rolfsii KACC40170, and Helicobasidium mompa KACC40836 strain showed the similar growth rates within 10% or less difference among treatments compared to dark control, regardless of lighting types. However, the mycelia growth on Rosellinia necatrix KACC40168 strain was significantly suppressed by blue, blue+green and blue+red LED as well as fluorescent lamp compared to a dark control, in common with lighting types. The melanin pigment on R. necatrix KACC40168 strain showed relatively to induce more strongly under green LED and fluorescent lamp, whereas no induction under red LED and a control, regardless of lighting types. Thus, the hypha width on R. necatrix KACC40168 was significantly thinned by blue and blue+green LED compared to a control, in common with lighting types.

• ETRI Journal
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• v.35 no.4
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• pp.566-570
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• 2013

In this paper, we demonstrate the capabilities of 380-nm ultraviolet (UV) light-emitting diodes (LEDs) using metal organic chemical vapor deposition. The epi-structure of these LEDs consists of InGaN/AlGaN multiple quantum wells on a patterned sapphire substrate, and the devices are fabricated using a conventional LED process. The LEDs are packaged with a type of surface mount device with Al-metal. A UV LED can emit light at 383.3 nm, and its maximum output power is 118.4 mW at 350 mA.

• Journal of the Optical Society of Korea
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• v.19 no.3
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• pp.311-316
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• 2015

We investigate the temperature dependence of the phosphor conversion efficiency (PCE) of the phosphor material used in a white light-emitting diode (LED) consisting of a blue LED chip and yellow phosphor. The temperature dependence of the wall-plug efficiency (WPE) of the blue LED chip and the PCE of phosphor are separately determined by analyzing the measured spectrum of the white LED sample. As the ambient temperature increases from 20 to $80^{\circ}C$, WPE and PCE decrease by about 4.5% and 6%, respectively, which means that the contribution of the phosphor to the thermal characteristics of white LEDs can be more important than that of the blue LED chip. When PCE is decomposed into the Stokes-shift efficiency and the phosphor quantum efficiency (QE), it is found that the Stokes-shift efficiency is only weakly dependent on temperature, while the QE decreases rapidly with temperature. From 20 to $80^{\circ}C$ the phosphor QE decreases by about 7% while the Stokes-shift efficiency changes by less than 1%.