• 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 Society for Precision Engineering
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• v.28 no.2
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• pp.133-139
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• 2011

We have performed optical design of light guide plates (LGPs) for a photobioreactor by using an illumination design tool. An LGP having light emitting diodes (LEDs) as a light source on the four sides was designed by optimizing the distribution of LGP patterns and design of another LGP, on top of which sunlight was focused by a Fresnel lens, was executed. Finally, a hybrid-solar-and-LED-lighting scheme was described. Detailed design process and optical performances of the designed LGPs are presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.234-238
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• 2014

Multichip packaging was achieved the best solution to significantly reduce thermal resistance at the same time, to increase luminance intensity in LEDs packaging application. For the packaging, thermal spreading resistance is an important parameter to get influence the total thermal performance of LEDs. In this study, silicon-based multichip light emitting diodes (LEDs) packaged module has been examined for thermal characteristics in several parameters. Compared to the general conventional single LED packaged chip module, multichip LED packaged module has many advantages of low cost, low density, small size, and low thermal resistance. This analyzed module is comprised of multichip LED array, which consists of 32 LED packaged chips with supplement power of 0.2 W at every single chip. To realize the extent of thermal distribution, the computer-aided design model of 6.4 W Si-based multichip LED module was designed and was performed by the simulation basis of actual fabrication flow. The impact of thermal distribution is analyzed in alternative ways both optimizing numbers of fins and the thickness of that heatsink. In addition, a thermal resistance model was designed and derived from analytical theory. The optimum simulation results satisfies the expectations of the design goal and the measurement of IR camera results. tart after striking space key 2 times.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.145-150
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• 2004

The LED lighting used spot-light illuminate the limited surface. So it is a key-point to condense wide emission angle of high power light emitting diodes (LEDs) to narrow that angle. In this paper, the secondary optics was designed by lens-makers formula for concentration rays of LED into specific region. So, it simulated the optics that designed by lens makers-formula in the optical design program, LightTools. And then, show the p propriety of lens design utilizing simulation result, luminous intensity, emission angle.

• ETRI Journal
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• v.44 no.1
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• pp.125-134
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• 2022

Visible light communication (VLC) systems incorporate ambient lighting and wireless data transmission, and the experienced channel in indoor VLC is a major topic that should be examined for reliable communication. In this study, it is realized that multiple transmitters in classical alignment are the forceful factors for channel characteristics. In the frequency band, fluctuations with sudden drops are observed, where the fluctuation shape is related to the source layout and receiver location. These varying frequency-selective channels need solutions, especially for mobile users, because sustained channel estimation and equalization are necessary as the receiver changes its location. It is proven that using light-emitting diodes (LEDs) with highly directional beams as sources or using a detector with a narrow field of view (FOV) in the receiver may help partially alleviate the problem; the frequency selectivity of the channel reduces in some regions of the room. For flat fading channel characteristics all over the room, LEDs should be aligned in hexagonal cellular structure, and detector FOV should be arranged according to the cell dimension outcomes.

• Journal of agriculture & life science
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• v.50 no.5
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• pp.1-9
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• 2016

Plant growth and development strongly influenced by light quantity and its spectral composition. Young tomato plants were cultivated in growth cabinets under artificial light provided by red and blue light emitting diodes(LEDs) during 12 hours, then plants were exposed to monochromatic ultraviolet, blue, green and red lights as an end-of-day(EOD) treatment during 4 hours to study their effect on plant growth parameters. EOD lighting from various LEDs increased total fresh and dry weights as well as assimilation area compared to those in control. Blue light increased stem height, internode length and stem diameter. Monochromatic UV-A light reduced stem elongation, highly increased stomatal conductance. Compactness and health index of young tomato plants were increased in UV-A and red light treatments.

• Korean Journal of Materials Research
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• v.32 no.11
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• pp.449-457
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• 2022

Halide perovskites are emerging materials for next-generation display applications, thanks to their narrow emission linewidth and band gap tunability, capable of covering the entire range of visible light. Despite their short period of research, perovskite light emitting diodes (PeLEDs) have shown rapid progress in device external quantum efficiency (EQE) in the near-infrared (NIR), red, and green emission wavelengths, and the record EQE has exceeded over 20 %. However there has been limited progress with blue emission compared to the red and green counterparts. In this review, the current status and challenges of blue PeLEDs are introduced, and strategies to produce spectrally stable blue PeLEDs are discussed. The strategies include 1) a mixed halide system in the form of 3-dimensional (3D) perovskites, 2) colloidal perovskite nanocrystals and 3) low dimensional perovskites, known as quasi-2D perovskites. In the mixed halide system, previous reports based on the compositional engineering of 3D perovskites to reduce spectral instability (i.e., halide segregation) will be discussed. Since spectral instability issue originate from the mixed halide composition in perovskites, the two other strategies are based on enlarging the band gap with a single halide composition. Finally, the prospects for each strategy are discussed, for further improvement in spectrally stable blue PeLEDs.

• Journal of Applied Biological Chemistry
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• v.58 no.2
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• pp.101-104
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• 2015

To evaluate four different light-emitting diodes (LEDs) as potential attractants for Tyrophagus putrescentiae adults, attractiveness of blue (470 nm), green (520 nm), yellow (590 nm), and red (625 nm) LEDs were investigated at 20, 40, and 60 lx luminance intensity in LED-equipped Y-maze chamber and compared with the response to black light bulb (BLB), which is used in commercial traps. The BLB, the blue LED, the green LED, the yellow LED, and the red LED did not show the attractive to T. putrescentiae adults. These results suggested that four LEDs tested could not be used for environment-friendly control of T. putrescentiae adults.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.376-383
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• 2013

The design of the LEDs lighting in general household illumination was proposed and compared with the fluorescent lighting in this study. Using the LED as a light source would promote energy saving lighting for household illumination purposes. We used the LightTools and DIALux software to design and simulate different standards of illuminance, different correlated color temperatures and different color rendering indices for household environments. The power consumption and efficiency of traditional illuminated light sources and an LED light source with the same standard of illuminance for lighting the household environment were analyzed and compared with each other. Finally, our results show the advantages of using white-light LEDs for lighting and household illumination.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.3
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• pp.151-155
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• 2014

We have developed quantum dot light emitting diodes (QD-LEDs) using a InP/ZnSe/ZnS multi-shell QD emission layer. The hybrid structure of organic hole transport layer/QD/organic electron transport layer was used for fabricating QD-LEDs. Poly(4-butylphenyl-diphenyl-amine) (poly-TPD) and tris[2,4,6-trimethyl-3-(pyridin-3-yl)phenyl]borane (3TPYMB) molecules were used as hole-transporting and electron-transporting layers, respectively. The emission, current efficiency, and driving characteristics of QD-LEDs with 50, 65 nm thick 3TPYMB layers were investigated. The QD-LED with a 50 nm thick 3TPYMB layer exhibited a maximum current efficiency of 1.3 cd/A.