• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.638-644
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• 2010

We have carry out numerical simulation of the electric-optical characteristics of organic light emitting diodes with gradient-doped emitting layer which were reported to be effective in improving luminous efficiency and lifetime. In this paper, the basic structure is comprised of ITO/NPB/$Alq_3$:C545T[%]/$Alq_3$/LiF/Al, six devices by separating the emitting layer of $Alq_3$:C545T[%] were studied. As the result, the uniformly-doped devices exhibited superior luminous efficiency-current density characteristics over conventional undoped device. In the case of gradient-doped devices, electric-optical characteristics were improved similar to uniformed-doped devices, unusually the distribution of traped-charge density in the OLED devices was shown as the staircase.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.8
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• pp.706-712
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• 2013

In this paper, channel modeling of VLC(Visible Light Communication) was investigated under indirect lightning circumstance which was the way that all phontons started from LED(Light Emitting Diode) were reached on the floor with NLOS paths. I supposed width(6m), depth(4m), height(2.2m) cube room circumstance for VLC communication channel and supposed that 4 LEDs were located at 2m height, which emitted photons at the direction of wall and ceiling. Channel characteristics, which were power attenuation and delayed receiving of light signal, were abstracted from receivers(PDs) which were located at 0.5m above from floor. The availability of channel was verified via BPSK based communication simulation.

• The Journal of the Convergence on Culture Technology
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• v.10 no.6
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• pp.849-853
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• 2024

This study was conducted from May 11 to June 20, 2024 to compare the growth of dwarf tomato according to light sources (White LED, Red + Blue LED) to select a light source suitable for urban agriculture. White LED (WH) and Red + Blue LED (RB) have differences in wavelength and total light intensity. Not only growth factors but also the number of fruits set and sugar content were significantly higher in WH than in RB. These results are thought to have been affected by the intensities of blue and red wavelengths, but they were determined to be influenced by the sum of all wavelength intensities (= total light intensity). Therefore, it is thought to be better to use WH with various wavelengths and high total light intensity for cultivation of tomato at home.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04a
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• pp.121-124
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• 2000

Achieving red light-emitting diodes with high quantum and luminous efficiency is required to fabricate the full-color organic electroluminescence display. In this work, we report that devices with 2.3,7,8,12,13,17,18-Octaethyl-21H,23H-porphine palladium (II) (PdOEP), doped into tris(8-Hydroxyquinolinato)-aluminum (III) (Alq3) show a narrow deep red emission (670nm). In addition, PdOEP has been used as host material in which red dyes such as 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) doped in order to fabricate efficient red-emitting diodes.

• Journal of Information Display
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• v.11 no.2
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• pp.52-56
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• 2010

High-efficiency organic light-emitting diodes (OLEDs) based on multilayer transparent electrodes (MTEs) are reported. The dielectric/metal/dielectric (DMD) multilayer electrode based on a thin silver layer achieved high sheet conductance as small as $6{\Omega}/sp$ and a tuning capability in the optical and electrical properties by engineering the inner and outer dielectric layers. In the conventional normal bottom-emitting structure, a DMD-based OLED can be fabricated with 90% higher forward luminous efficiency and 30% higher external quantum efficiency (EQE) compared to ITO-based devices. Special attention was paid to the optimization method of such MTE structure considering both the injection and optical structures.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.188-191
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• 2009

A high efficiency deep blue phosphorescent organic light-emitting diode (PHOLED) was developed using a new wide triplet bandgap host material (PPO1) with a phenylcarbazole and a phosphine oxide unit. The wide triplet bandgap host material was synthesized by a phosphornation reaction of 2-bromo-Nphenylcarbazole with chlorodiphenylphosphine. A deep blue emitting phosphorescent dopant, tris((3,5-difluoro-4-cyanophenyl)pyridine)iridium (FCNIr), was doped into the PPO1 host and a high quantum efficiency of 17.1 % and a current efficiency of 19.5 cd/A with a color coordinate of (0.14,0.15) were achieved in the blue PHOLED. The quantum efficiency of the deep blue PHOLED was better than any other quantum efficiency value reported up to now.

• Journal of Digital Contents Society
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• v.8 no.4
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• pp.425-430
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• 2007

Depends on the running dry of the radio resources for the next generation of wireless communication system the estimated possibilities of the visible light which used for the devices such as signal light, the electric display board, guide board and so on applied for the next generation wireless network is the topic to be explored in this paper. Since radiation efficiency utilization for the wireless network has its capacity to become a trend direction we will study also on its application as well as the technique standardization.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.6
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• pp.35-40
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• 2008

High performance light emitting diodes(LEDs) have been developed using GaN-based materials grown on sapphire substrates in recent years. Although these LEDs are already commercially available, we have to consider electrostatic discharge(ESD) damage related to both basic materials of diode and miniaturization of LEDs. ESD damage is one of the important parameters influencing reliability of the light emitting devices. We investigated mass production of GaN-based LEDs suffered from ESD during production process and present the solutions in order to improve the ESD problem. Most of EDS problems were controlled by using instruments properly and improvement of the process circumstances as well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.332-333
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• 2009

In this paper, we have deposited silicon nitride films by plasma-enhanced chemical vapor deposition (PECVD). For films deposited under optimized conditions, the mechanism of plasma-enhanced vapor deposition of silicon nitride is studied by varying process parameters such as rf power, gas ratio, and chamber pressure. It was demonstrated that organic light-emitting diode(OLEDs) were fabricated with the inorganic passivation layer processing. We have been studied the inorganic film encapsulation effect for organic light-emitting diodes (OLED). To evaluate the passivation layer, we have carried out the fabrication of OLEDs and investigate with luminescence and MOCON.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1169-1174
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• 2013

The objective of this work was to increase the efficiency of ultraviolet-light emitting diodes at 375 nm for sterilization. Since $TiO_2$ had antibacterial properties, which were attributed to the appearance of hydroxyl radicals and superoxide radical anions on the surface species under ultra violet radiation at about 387 nm, photo-reactive layers such as Ag-doped $TiO_2$ were coated on aluminum substrates by electrostatic spraying. Crystallinity and surface morphology of the coating layer were examined by X-ray diffraction ${\theta}-2{\theta}$ scan and field emission-scanning electron microscope, respectively. In an antibacterial test, we observed above 99% reduction of Escherichia coli populations on 3 or 5 mol% Ag-doped $TiO_2$ layers after irradiation for 2 hrs at 375 nm, while very low inactivation on bare aluminum substrates occurred after irradiation as the same condition.