• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.37-41
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• 2018

$Y_3A_{l5}O_{12}:Ce^{3+},Pr^{3+}$ single crystal phosphor was prepared by floating zone method. single crystal was confirmed to have a Ia-3d (230) space group of cubic structure and showed regular morphology. The optical properties, single crystal exhibited a emission band from green, yellow wide wavelength and 610nm, 640nm red wavelength vicinity. The luminance maintenance rate was decreased by phonon with increasing temperature, but high luminance is maintained more than powder phosphor. In addition, $Y_3A_{l5}O_{12}:Ce^{3+},Pr^{3+}$ single crystal phosphor was applied to a high power blue laser diode, we implemented high power white laser lightings. and it was confirmed that thermal properties over time, due to the effective heat transfer of complete crystal structure. We confirmed that excellent radiant heat properties than powder phosphor was applied to a high power white laser diode.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.233-240
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• 2012

White LEDs (light-emitting diodes) are promising new-generation light sources which can replace conventional lamps due to their high reliability, low energy consumption and eco-friendly effects. This paper briefly reviews recent progress of oxy/nitride host phosphor and quantum dot materials with broad excitation band characteristics for phosphor-converted white LEDs. Among oxy/nitride host materials, $M_2Si_5N_8$ : $Eu^{2+}$, $MAlSiN_3$ : $Eu^{2+}$ M-SiON (M = Ca, Sr, Ba), ${\alpha}/{\beta}$-SiAlON : $Eu^{2+}$ are excellent phosphors for white LED using blue-emitting chip. They have very broad excitation bands in the range of 440~460 nm and exhibit emission from green to red. In this paper, In this review we focus on recent developments in the crystal structure, luminescence and applications of the oxy/nitride phosphors for white LEDs. In addition, the application prospects and current trends of research and development of quantum dot phosphors are also discussed.

• Journal of the Korean Chemical Society
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• v.61 no.4
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• pp.163-167
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• 2017

Along with the progress of white LED technology, red phosphors have become increasingly important in industry and academia, and a more specific demand has steadily increased in the market. Red phosphors are used in high efficiency and high rendering LED lightings. However, using red phosphors with $Eu^{2+}$ activators caused color rewarming and reduced emission intensity in white LED chips due to strong reabsorption in the green or yellow wavelength range caused by the 4f-5d transition. $Mn^{4+}$ doped phosphors which have no such drawbacks and which can further improve the color rendering index (CRI) are now of great interest. However, $Mn^{4+}$-doped phosphors have a disadvantage in that the emission wavelength is determined depending on the host due to the $^2E_g{\rightarrow}^4A_2$ transition. In this study, the $SrO-BaO-GeO_2$ solid-solution was selected, and $Sr_{1-x}B_axGe_4O_9:Mn^{4+}{_{0.005}}$ ($0{\leq}x{\leq}1$) phosphors were synthesized and characterized. This led to a versatile color tuning in LED technology.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.757-758
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• 2010

At the time of medical treatment and surgical operation, halogen lamp and plasma lamp were mainly used as luminous source for lighting. These two luminous sources have drawbacks that the life of lamps are not long, various problems are brought about due to excessive heat generation and its volume is very big because of cooling device. Accordingly, in this research a ring light was developed so that a partial shadowless shooting for the patient's affected area at the medical treatment room and surgical operation room using high luminance LED for which attention is being paid as new lighting parts for medical purpose. LED which was applied to the development used high luminance three color LED for full color for which various color materialization and the adjustment of radiation intensity are possible and we can get white light in order to emphasize the delicate expression for generic tone of shooting object, strong highlight, simple shadow and three dimensional effect at the time of close-up shadowless shooting of the affected area.

• Journal of IKEEE
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• v.13 no.4
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• pp.70-74
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• 2009

In this paper, We propose the visible light communication(VLC) link based on white light emitting diode (LED) and Photo detector(PD). The proposed architecture is demonstrated experimentally and its performance is verified through the experimental results of quality-factor(Q-factor) and eye pattern of 10Mb/s PRBS signal. The ambient light effect from a typical type fluorescent lamp source was also analyzed. when the distance between the LED and the PD is about 1m, error free wireless transmission of the LED was achieved up to 10Mb/s data rate. Under the condition with ambient light, low BER, data transmission of the VLC link is achieved up to 5Mb/s data rate at 1m. Also, when the PD is placed away from the center, low BER data transmission of the VLC link is achieved up to 1Mb/s at 10cm and 10Mb/s at 5cm.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.35-38
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• 2015

LEDs are considered to be an alternative for enhancement of energy efficiency, applied for numerous areas such as display, automotive headlight not only lights. Yellow phosphor is generally utilized with blue LEDs to generate WLED, $Y_3Al_{5}O_{12}:Ce^{3+}$ is typically used as the yellow phosphor. The phosphor, mixed with epoxy resin, has been used by being spread and hardened on the blue LED chip. This paste-based packaging gives rise to problems of degradation of phosphor by heat and decrease of luminous efficiency. Although phosphor plate is used instead of the epoxy-phosphor mixture to solve these problems, loss of luminous efficacy by total internal reflection inside the plate also should be solved. In this study, we coated the side of the plate with silver as one of the solution.

• Korean Journal of Optics and Photonics
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• v.32 no.5
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• pp.220-229
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• 2021

The optical characteristics of high-power direct-lit white light-emitting diode (LED) lighting were investigated, where a quantum dot (QD) film was adopted to enhance the color-rendering index (CRI). The transmittance of the diffuser plate and the concentration of the QD film were varied in this study. The color coordinates and the correlated color temperature (CCT) did not show any appreciable change, while the CRI values increased slightly as the transmittance of the diffuser plate decreased. The investigated optical properties were nearly independent of the viewing angle, and the luminance distribution was close to Lambertian. The CCT decreased from approximately 6000 K to approximately 4000 K as the concentration of the QD film increased from 0 to 7.5 wt%, which was due to the enhanced red component in the emission spectrum. The CRI increased to approximately 95 for some optical configurations of the lighting. These results demonstrate that glare-free, color-changeable, high-rendering LED lighting can be realized by using a combination of a diffuser plate of appropriate transmittance and a red QD film.

• Journal of Life Science
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• v.29 no.3
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• pp.311-317
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• 2019

To investigate the effects of light on growth in fish, olive flounder (Paralichthys olivaceus) were reared under four kinds of monochromatic light-emitting diodes (LEDs) at violet (400 nm), blue (465 nm), green (508 nm), and red (635 nm) wavelengths, along with a white fluorescent lamp as control. The rearing experiments were carried out with 15 fish per tank under different wavelength illumination at the same intensity. After rearing the fish under a 12 hr:12 hr light:dark photoperiod for 60 days, percentage increases in weight gain of $269.92{\pm}13.02$, $363.21{\pm}3.74$, $433.22{\pm}4.83$, $290.17{\pm}11.83$, and $340.74{\pm}26.58%$ and increases in specific growth rates (SGR) of $2.18{\pm}0.06$, $2.56{\pm}0.07$, $2.79{\pm}0.01$, $2.27{\pm}0.05$, and $2.47{\pm}0.10$ were observed in fish grown under the illumination of red, blue, green, and violet LEDs and the white fluorescent light, respectively. The results show faster growth in fish reared under green LEDs, but slower growth in those reared under red light. Differences in most blood parameters were minor, aside from an increased level of glutamic oxaloacetic transaminase in the fish grown under red LED illumination. Histological analysis of the retina showed few changes in the ratio of photoreceptor layer thickness to total retina thickness in fish reared under the green LEDs compared to those in other illumination groups. These results indicate that green LED light can foster increased growth in olive flounder with no distinct harmful effects on their light-sensitive photoreceptor layers.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.9
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• pp.630-636
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• 2012

The purpose of this study was to determine optimum wavelength, light intensity, aeration rate, and temperature for the cultivation of Dunaliella salina illuminated by various types of light emitting diode. Growth rates of Dunaliella salina were faster at higher temperature than the growth rate at lower temperature. Among the culturing temperatures, $22^{\circ}C$ was the optimum temperature for the growth of Dunaliella salina. White LED was the most efficient light source and lower light intensity (3,000 Lux) resulted in better biomass production (1.30 g/L). The value of aeration varied between 0 and 2.4 vvm at the illumination of 3,000 Lux of white light emitting diode. Highest specific growth rate of $1.12day^{-1}$ was obtained at no-aeration and lower specific growth rates were obtained for other aeration tests, which indicated that aeration could be harmful for the cultivation of Dunaliella salina.

• Journal of Bio-Environment Control
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• v.31 no.3
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• pp.204-211
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• 2022

To produce a high quality crop, light is an essential environmental factor in greenhouse cultivation. In the winter season, solar radiation is weak than other season. Therefore, using supplemental light during a low radiation period can increase the crop growth and yield. This study was conducted to select the economical supplemental light source for greenhouse cultivation in pepper during the low radiation period. The green pepper (Capsicum annuum 'Super Cheongyang') was transplanted on 5 September 2019. Supplemental lighting treatment was conducted from 1 January 2020 to 31 March 2020. RB LED (red and blue LED, red:blue = 7:3), W LED (white LED, R:G:B = 5:3:2), and HPS (high-pressure sodium lamp) were used as the supplemental light source. Non-treatment was used as the control. The plant height, SPAD, and number of nodes of pepper plants have no significant differences by supplemental light sources. However, the number of ramifications plants was the greatest in RB LED light source. Moreover, supplemental lighting increased photosynthesis of the pepper plant, and especially, the RB LED had the highest photosynthesis rate during supplemental lighting period. Also, the yield of pepper increased in the supplemental lighting treatment than in the control, and the RB LED had the greatest yield than other light sources. The electricity consumption was the highest in W LED and the lowest in HPS light. Through the economic analysis, the RB LED had high economic efficiency. In conclusion, these results suggest that using RB LED for supplemental light source during low radiation in pepper greenhouse increase the yield and economic feasibility.