• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05a
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• pp.27-31
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• 2001

We fabricated organic electroluminescent(EL) devices with mixed emitting layer of poly(N-vinylcarbazole)(PVK), 2,5-bis(5'-tert-butyl-2-benzoxazoly)thiophene(BBOT), N,N'-diphenyl-N,N'-(3-methyphenyl)-1,1'-biphenyl-4, 4'-diarnine(TPD) and poly(3-hexylthiophene)(P3HT). To improve the external quantum efficiency of EL devices, we added the functional layer to the devices such as LiF insulating layer, carrier confinement layer(BBOT) and hole injection layer(CuPc). In the ITO/emitting layer/Al device, the maximum quantum efficiency at 15V was $1.88{\times}10^{-5}%$. And then, it is increased by a factor of 27 to $5.2{\times}10^{-3}%$ in ITO/CuPc/emitting layer/BBOT/LiF/Al device at 15V.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.2
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• pp.185-191
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• 1992

In this paper, it is attempted to distinguish the charged particles and to judge the polarity by the use of Thermally Stimulated Current(TSC) and Temperature Gradient Thermally Stimulated Surface Potential Measurement(TG-TSSP)with experimental insulation material XLPE-EVA for power cables which is made by blending cross-linked polyethylene(XLPE) and ethylene-vinylacetate copolymer(EVA). In addition, it is performed to investigate the effect of EVA blending. From the experimental results, it is known that for the case of XLPE-EVA blended experimental material, the generation of space charged electric field is not obtained in the high temperature region due to the obatruction of the injection of trapping carrier by the electron and the positive hole.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.265-268
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• 1997

Electroluminescent(EL) devices are constructed using multilayer organic thin film. A cell structure of glass substrate/Indium-Tinoxide/TPD as a hole transporting layer/Alq3+Rhodamine 101 perchrolate(Red3) as an emitting layer/Alq3 as an electrron transporting layer/Al as an electrode was employed. Optimal thickness of emitting layer in EL cell was performed from the viewpoint of the electronics properties of emitting layers. The general vapor-deposition method was used to control the thickness of omitting layer in EL devices and electro-optical characteristics were measured. It is clarified that controlling thickness of emitting layer in vapor-deposition film had an effect on the change of carrier injection and EL spectrum. The intensity of red omission with luminance of 81cd/$m^2$ was achived at 11V driving voltage. The surface morphology of emitting layer in EL devices was investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.374-377
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• 2001

We have synthesized poly(3-hexylthiophene)(P3HT), which is the most famous conducting polymer and studied the optical properties of P3HT. And then fabricated the device using P3HT as an emitting layer. For the improve of hole injection from ITO electrode to P3HT emitting layer, we use transparent polyaniline(PANI) electrode. In the voltage-current-luminance characteristics of ITO/PANI/P3HT/LiF/Al device which use the PANI film synthesised during 5 cycle, the device turn on at the 2V and the luminance of $218nW/cm^{2}$ obtained at 12V. External quantum efficiency of ITO/PANI/P3HT/LiF/Al increased at 8V than that of ITO/P3HT/LiF/Al device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.374-377
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• 2001

We have synthesized poly(3-hexylthiophene)(P3HT), which is the most famous conducting polymer and studied the optical properties of P3HT. And then fabricated the device using P3HT as an emitting layer. For the improve of hole injection from ITO electrode to P3HT emitting layer, we use transparent polyaniline(PANI) electrode. In the voltage-current-luminance characteristics of ITO/PANI/P3HT/LiF/Al device which use the PANI film synthesised during 5 cycle, the device turn on at the 2V and the luminance of 218 nW/$\textrm{cm}^2$ obtained at 12V. External quantum efficiency of ITO/PANI/P3HT/LiF/Al increased at 8V than that of ITO/P3HT/LiF/Al device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.376-382
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• 2000

We successfully fabricated OLED(Organic Light Emitting Diodes) with Al cathodes electrode deposited by the DC magnetron sputtering. The effects of a controlled Al cathode layer of an Indium Tin Oxide (ITO)/blended single polymer layer (PVK Bu:PBD:dye)/Al light emitting diodes are described. The PVK (Poly(N-vinylcarbazole)) and Bu-PBD (2-(4-biphenyl-phenyl)-1,3,4-oxadiazole) are used hole transport polymer and electron transport molecule respectively. We found that both current injection and electroluminescence output are significantly different with a variable DC sputtering power. The difference is believed to be due to the influence near the blended polymer layer/cathode interface that results from the DC power and H$\sub$2//O in a chamber. And DC sputtering deposition is an effective way to fabricate Al electrodes with pronounced orientational characteristics without damage occurring to metal-organic interface during the sputtering deposition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.197-200
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• 2005

We have studied conduction mechanism that is interpreted in terms of space charge limited current (SCLC) region and tunneling region. The OLEDs are based on the molecular compounds, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) as a hole transport, tris (8-hydroxyquinolinoline) aluminum(III) $(Alq_3)$ as an electron injection and transport and emitting layer. We manufactured reference structure that has in $ITO/TPD/Alq_3/Al$. Buffer layer effects were compared to reference structure. And we have analyzed out electrical conduction mechanism in $ITO/Alq_3/Al$ device with various temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.1
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• pp.18-23
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• 2010

We demonstrated that the solution processed organic light-emitting diodes (OLEDs) have the high efficiency with pre-treated indium-tin-oxide (ITO). ITO surface was pre-treated with four methods and compared each other. The pre-treatment of ITO surface improves the chemical and physical characteristics of ITO such as the surface roughness, adhesion property, and the hole injection ability. These properties were analyzed by the contact angle, atomic force microscope (AFM) image, and the current flow character in device. As a results, the device with ITO pre-treated by $O_2$ plasma shows the current efficiency of 5.93 cd/A, which is 1.5 times the device without pre-treatment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.158-161
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• 2004

We have studied a lifetime in organic light-emitting diodes depending on buffer layer. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. And the cathode for electron injection was LiAl. Phthalocyanine Copper(CuPc), Poly(3,4-ethylenedioxythiophene):poly (PEDOT:PSS), or poly (9-vinylcarbazole)(PVK) material was used as a buffer layer. A thermal evaporation was performed to make a thickness of 40nm of TPD layer at a rate of $0.5{\sim}1\;{\AA}/s$ at a base pressure of $5{\times}10^{-6}\;torr$. A material of tris(8-hydroxyquinolinate) Aluminum($Alq_3$) was used as an electron transport and emissive layer. A thermal evaporation of $Alq_3$ was done at a deposition rate of $0.7{\sim}0.8[{\AA}/s]$ at a base pressure of $5{\times}10^{-6}\;torr$. By varying the buffer material, hole injection at the interface could be controlled because of the change in work function. Devices with CuPc and PEDOT:PSS buffer layer are superior to the other PVK buffer layer.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.1 s.38
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• pp.51-55
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• 2006

The green emitting high performance OLEDs using the $Alq_3$-C545T fluorescent system have been fabricated and characterized. In the device fabrication, 2-TNATA [4,4',4'-tris(2-naphthylphenyl-phenylamino)-triphenylamine] as a hole injection material and NPB [N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] as a hole transport material were deposited on the ITO(indium thin oxide)/glass substrate by vacuum evaporation. And then, green color emission layer was deposited using $Alq_3$ as a host material and C-545T[10-(2-benzothiazolyl)-1,1,7,7- tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]/benzopyrano[6,7,8-ij]-quinolizin-11-one] as a dopant. Finally, small molecule OLEDs with structure of ITO/2-TNATA/NPB/$Alq_3$:C545T/$Alq_3$/LiF/Al were obtained by in-situ deposition of $Alq_3$, LiF and Al as the electron transport material, electron injection material and cathode, respectively. Green OLEDs fabricated in our experiments showed the color coordinate of CIE(0.29, 0.65) and the maximum power efficiency of 7.3 lm/W at 12 V with the peak emission wavelength of 521 nm.