• Journal of Acupuncture Research
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• v.32 no.3
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• pp.211-220
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• 2015

Objectives : We report two cases of pressure ulcer patients to show the efficacy of treatment with acupuncture and Light Enitting Diode(LED) light therapy. Methods : We treated two pressure ulcer patients with acupuncture, LED light therapy, herbal medication and with a simple dressing. LED light with up to $4J/cm^2$ of energy irradiated the pressure ulcer site once a day for fifteen minutes. All patients received acupuncture treatment and simple dressing for wound care. We measured phase change of the pressure ulcer in terms of ulcer size, The National Pressure Ulcer Advisory Panel(NPUAP) stage and with the The Pressure Ulcer Scale for Healing(PUSH) tool(3.0). Results & Conclusions : In each of the two cases, pressure ulcer size and total score of the PUSH tool decreased and NPUAP stage was improved from II to I. This shows that acupuncture treatment and LED light therapy may have a considerable effect in healing on the pressure ulcer.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.137-140
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• 2005

Organic light emitting transistors (OLET) which are vertically combined with the organic static induction transistor (OSIT) and organic light emitting diode (OLED) are fabricated and the device characteristics are investigated. High luminance modulations by relatively low gate voltages are obtained. In order to realize the flexible electronic circuits and displays, we have fabricated OSIT on plastic substrates. The OSIT fabricated on plastic substrate show almost same characteristics comparing with those of nonflexible OSIT on glass substrate. The OLET described here is a suitable element for flexible sheet displays.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1377-1378
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• 1998

Blue light emitting electroluminescence(EL) diodes were fabricated utilizing Coronene and some organic materials. Coronene showed photoluminescence(PL) peak at 450nm in solution with high quantum efficiency. Multi layer system was applied to fabricate EL diode utilizing Coronene. The device showed didode-like applied voltage-current relationship. And blue light emitting was observed. The decay time of device was in a scale of some seconds. The trun-on voltage of device was about 9 V.

• Transactions on Electrical and Electronic Materials
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• v.8 no.3
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• pp.131-134
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• 2007

An $ITO/Alq_3/Al$ structure was used to study complex impedance of $Alq_3$ based organic light-emitting diodes. Equivalent circuit was analyzed in a device structure of $ITO/Alq_3/Al$ with a thickness layer of $Alq_3$ of 100 nm. The obtained impedance was able to be fitted using equivalent circuit model of parallel combination of resistance $R_p$ and capacitance $C_p$ with a small series resistance of $R_s$.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1448-1449
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• 2008

Inkjet printing is commonly used in depositing the solution of functional materials on the specific locations of a substrate, and also it can provide easy and fast patterning of polymer films over a large area. Inkjet printing is applicable to fabricating an organic light emitting diode (OLED), since conducting materials used as emissive electroluminescent layers can be manufactured into inks for ink jetting. By using the inkjet technology, we have succeeded in patterning a poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) layer and a poly[2-Methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) layer on the Indume tin oxide (ITO) patterned substrates, and fabricating organic light emitting diodes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.100-101
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• 2008

We have developed low voltage driving white organic light emitting diode with new electron transport layer. The with light emission was realized with a yellow dopant, rubrene and blue-emitting DPVBi layer. The new electron transport layer results in very high current density at low voltage, causing a reduction of driving voltage. The device with new electron transport layer shows a brightness of 1000 cd/m2 at 4.3 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.492-493
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• 2007

We have investigated Electrical Properties of Organic Light-Emitting Diode depending on Varied Temperature using 8-hydroxyquinoline aluminum($Alq_3$) as an electron transport and emissive material. We analyzed the electrical properties of organic light emitting diodes by impedance characteristics of ITO/$Alq_3$/Al. Impedance characteristics was measured complex impedance Z and phase e in the frequency range of 40 Hz to $10^7\;Hz$. From these analyses, we are able to interpret electrical Properties of OLED depending on temperature.

• 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 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%.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.260-264
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• 2007

We have studied stability in organic light-emitting diode depending on buffer layer and cathode. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. An electron injection energy barrier into organic material is different depending on a work function of cathodes. Theoretically, the energy barriers for the electron injection are 1.2 eV, -0.1 eV, and 0.0 eV for Al, LiAl, and LiF/Al at 300 K, respectively. We considered the cases that holes are injected to organic light-emitting diode. The hole injection energy barrier is about 0.7 eV between ITO and TPD without buffer layer. For hole-injection buffer layers of CuPc and PEDOT:PSS, the hole injection energy barriers are 0.4 eV and 0.5 eV, respectively. When the buffer layer of CuPc and PEDOT:PSS is existed, we observed the effects of hole injection energy barrier, and a reduction of operating-voltage. However, in case of PVK buffer layer, the hole injection energy barrier becomes high(1.0 eV). Even though the operating voltage becomes high, the efficiency is improved. A device structure for optimal lifetime condition is ITO/PEDOT:PSS/TPD/$Alq_3$/LiAl at an initial luminance of $300cd/m^2$.