• 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%.

• Animal Bioscience
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• v.36 no.5
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• pp.731-739
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• 2023

Objective: This study was to evaluate the interaction of three different light-emitting diode (LED) light colors (white, green, and blue) and three intensities (5, 10, and 15 lx) on slaughter performance, meat quality and serum antioxidant capacity of broilers raised in three-layer cages. Methods: A total of 648 (8-days-old) male broiler chicks (Cobb-500) were randomly assigned in 3×3 factorially arranged treatments: three light colors (specifically, white, blue, and green) and three light intensities (namely, 5, 10, and 15 lx) for 35 days. Each treatment consisted of 6 replicates of 12 chicks. The test lasted for 35 days. Results: The semi-eviscerated weight percentage (SEWP) in 5 lx white was higher than that in 15 lx (p<0.01). The eviscerated weight percentage (EWP) (p<0.05) and water-loss percentage (WLP) (p<0.01) decreased in 10 lx white light than those in green light. Under blue light, the content of hypoxanthine (Hx) in muscle was lower than that under white and green light (p<0.01). The content of malondialdehyde (MDA) in 15 lx blue light was higher than that in 10 lx green light (p<0.05). Light color had an extremely significant effect on thigh muscle percentage, WLP, Hx, and crude protein content (p<0.01). Light intensity had a significant effect on SEWP (p<0.05), EWP (p<0.05), lightness (L^*) value (p<0.05), WLP (p<0.01), and the contents of superoxide dismutase (p<0.05), MDA (p<0.01), glutathione peroxidase (p<0.01). Conclusion: Using white LED light with 10 lx light intensity can significantly improve the chicken quality of caged Cobb broilers, improve the content of inosine acid in chicken breast and enhance the antioxidant capacity of the body. We suggest that the broiler farm can use 10 lx white LED light source for lighting in 8 to 42 days.

• Journal of the Korean institute of surface engineering
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• v.40 no.2
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• pp.103-106
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• 2007

We have investigated the optical and electrical properties of surface mounted white light emitting diode (LED) chips prepared by using yellow phosphors on the blue LED chip. The yellow phosphor mixed with transparent epoxy was coated on the prepared LED chip. The optimum mixing conditions with epoxy and yellow phosphor is obtained at the mixing ratio of epoxy:yellow phosphor = 97:3 wt%. The maximum luminance and light emitting efficiency are above $80,000cd/m^2$ and 23.2 lm/W, respectively, at the bias voltage of 2.9 V. There was no distinct change in the luminance strength with changing of the yellow phosphor ratios. The current of the white LED chip is about 30 mA at 2.9 V.

• Journal of Satellite, Information and Communications
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• v.8 no.1
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• pp.71-76
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• 2013

In this paper, a transceiver of VLC (Visible Light Communication) using LED white lighting has been implemented. The transmitted waveforms of LED and PD (Photo Diode) of the received signal are analyze to restore VLC data. Audio signal was successfully transmitted to demonstrate possibility and potential of optical wireless communication systems. Various modulation formats are considered to evaluate and compare performance in diverse channel conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.15-21
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• 2004

The optical characteristics; luminous flux, correlated color temperature, and CIE -chromaticity coordinate etc., of HB LED(high brightness light emitting diode) of yellow/green/white SMD(surface mounted device) type were tested with integrating sphere photometer and monochromator, and the results were comparatively evaluated And, for the white LED, color rendering indices were considered to analyze.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.928-931
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• 2003

In order to realize full color display, two approaches were used. The first method is the patterning of red, green, and blue emitters using a selective deposition. Another approach is based on a white-emitting diode, from which the three primary colors could be obtained by micro-patterned color filters. White-light-emitting organic light emitting devices (OLEDs) are attracting much attention recently due to potential applications such as backlights in liquid crystal displays (LCDs) or other illumination purposes. In order for the white OLEDs to be used as backlights in LCDs, the light emission should be bright and have Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.33, 0.33). For obtaining white emission from OLEDs, different colours should be mixed with proper balances even though there are a few different methods for mixing colors. In this study, we will report a white organic electroluminescent device using exciton diffusion length concept.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.459-465
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• 2012

We had synthesized a green dopant material based on the binaphthyl group, 7,7'-(2,2'dimethoxy-1,1'-binaphthyl-3,3'-diyl) bis(4-(thiophen -2-yl) benzo[e][1,2,5] thiadiazole (TBT). We also fabricated the white organic light emitting diode (OLED) with a phosphorescent blue emitter : iridium(III)bis[(4,6-di-fluoropheny)-pyridinato -N,C2]picolinate (FIrpic) doped in N,N'-dicarbazolyl-3,5-benzene (mCP) of hole transport type host material and both TBT and bis(2-phenylquinolinato)- acetylacetonate iridium(III) (Ir(pq)2acac) doped in 1,3,5-tris(N-phenylbenzimidazole -2-yl)benzene (TPBi) of electron transport type host material. As a result, the property of white OLED using TBT, which demonstrated a maximum luminous efficiency and external quantum efficiency of 5.94 cd/A and 3.23 %, respectively. It also showed the pure white emission with Commission Internationale de I'Eclairage (CIE) coordinates of (0.34, 0.36) at 1000 nit.

• Journal of the Optical Society of Korea
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• v.11 no.2
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• pp.67-70
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• 2007

A Wide Color Gamut Backlight system was studied using a three-band white Light-Emitting Diode. A three-band white light-emitting diode (LED) was fabricated using an InGaN-based blue LED chip that emits 445-nm blue peak, and a green phosphor and red phosphor that emit 535-nm green and 621-nm red peak emissions, respectively, when excited by 450-nm blue light. Using for this three-band white LED, wide color gamut backlight unit (BLU) was attained. The luminance of BLU and CIE 1931 chromaticity coordinates was $1,700Cd/m^2$ and (0.337, 0.346). Color filter matching simulations for this configuration show that the three-band white LED backlight can be enhanced by up to 16% over conventional white LED backlight color gamut.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.63-67
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• 2015

White light-emitting diode (WLED) is growing interest in using both illumination and communications. This paper reports visible light communication (VLC) composed of a super bright white light-emitting diode, low cost commercial photo-diode and a Fresnel lens. LED driver is consisted of the power MOSFET and MOSFET driver that switches the LED on and off. The modulation bandwidth of the LED used was determined to be 8 MHz. However, it was possible to communicate up to 1 Mbps under illumination of 500 lx because of the weak signal power and a low spectral sensitivity of the SHF213 as a PIN photodiode. In order to enhance the system bandwidth, the LED light was focused on the PIN photodiode by use of the Fresnel lens. As a result of that, visible light link was operated up to modulation bandwidth of the LED. The signal to noise ratio can be improved by 40 dB using an optical concentration at the receiver.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1587-1590
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• 2006

Through the engineering of recombination region and energy transfer in organic light emitting device, blue and red light emitting device with good color stability has been successfully obtained. A Color control layer (CCL), which emits green light through the energy transfer from the emission layers, has been introduced into the blue and red light emitting device for RGB white OLED. The RGB white OLED showed the current efficiency of 13 cd/A and the CIE coordinates of (0.33, 0.38) at $1000\;cd/m^2$. The device exhibited very stable spectrum with respect to operating current density and the CIE coordinates varied from (0.34, 0.38) to (0.31, 0.37) for $100-22000\;cd/m^2$.