• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.585-587
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• 2004

We report the characterization of white light emitting devices fabricated using conjugated polymer blends. Blue emissive poly[9,9-bis(4'-n-octyloxyphenyl) fluorene-2,7-diyl-co-10-(2'-ethylhexyl)phenothiazine-3,7-diyl] [poly(BOPF-co-PTZ)] and red emissive poly(2-(2'-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene) (MEH-PPV) were employed in the blends. The inefficient energy transfer between these blue and red light emitting polymers (previously deduced from the PL spectra of the blend films) enables the production of white light emission through control of the blend ratio. The PL and EL emission spectra of the blend systems were found to vary with the blend ratio. The EL devices were fabricated in the ITO/PEDOT/blend/LiF/Al configuration and white light emission was obtained for one of the tested blend ratios.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.96-99
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• 2000

We fabricated electroluminescent(EL) devices which have a blended single emitting layer containing poly(N-vinylcarbazole)[PVK] and poly(3-dodecylthiophene)[P3DoDT]. The molar ratio between P3DoDT and PVK changed with 1:0, 2:1 and 1:1. To improve the external quantum efficiency of EL devices, we applied insulating layer, LiF layer, between polymer emitting layer and Al electrode. All of the devices emit orange-red light and its can be explained that the energy transfer occurs from PVK to P3DoDT. In the voltage-current and voltage-light power characteristics of devices applied LiF layer, current and light power drastically increased with increasing applied voltage. In the consequence of the result, the external quantum efficiency of the devices that have a molar ratio 1:1 with LiF layer was 35 times larger than that of the device without LiF layer at 6V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.57-60
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• 2002

In generally, the guest-emitter doped system has been reported to give a bright electroluminescence(EL). The purpose of using doped system is to improve for increasing lifetime and efficiency, and tuning multicolor light. This indicates an enhanced electron-hole recombination rate in emitting layer. The purpose of this study is to obtain the high performance EL devices for flat panel display with red emission. We fabricated EL devices using the guest-host system. where DCM derivatives were taken as a dopant. The devices are fabricated in multilayer system with various concentration of the dopant (red light emitting dye). We measured the I-V characteristics and EL spectra from these devices. and we compared with photoluminescence(PL) quantum yield among the DCM derivatives. The emission mechanism of devices is participated in energy transfer. The energy transfer from these hosts to DCM generates luminescence spectra that vary from yellow red to red, depending on DCM derivatives. Absorption and emission spectra of organic materials composing the devices depend on the emission materials doped with the DCM derivatives. We demonstrated that the high EL efficiency can be achieved by doping host material with DCM derivatives and molecular steric structures

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.3
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• pp.43-48
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• 2001

The stability and efficiency of organic light emitting devices are the most critical problems to be solved. The devices based on tris-8-(hydroxyquinoline) aluminum ($Alq_3$) and N,N-diphenyl-N,N-bis(3-methylphenyl)-1, 1-biphenyl-4,4-diamine (TPD) were used to study the effects of buffer layers on their characteristics. We have investigated the characteristic effects of CuPc (copper phthalocyanine) and pentacene buffer layers on the device characteristics, the (5${\sim}$20 nm thick) CuPc layers and the (10${\sim}$20 nm thick) pentacene layers were deposited. Efficiency was slightly improved and the turn-on voltages of the devices with the buffer layers were observed to have lower values than those of the devices without the buffer layers. It is believed that this result is attributed to the improvement of hole injection capability through the buffer layers into hole transport layer (HTL). We have also studied the atomic force microscopic images of the TPD layers deposited on the buffer layer and the bare ITO.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.625-628
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• 2004

Porous anodic alumina(PAA) which has arrays of nano size holes, was incorporated into organic light emitting devices. Porous anodic alumina on glass scattered the light generated from emitting layer and was decreased the waveguiding modes within the glass. An increase in the device coupling-out factor for the scattering structure is demonstrated.

• ETRI Journal
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• v.45 no.6
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• pp.1056-1064
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• 2023

The optical properties of the materials composing organic light-emitting diodes (OLEDs) are considered when designing the optical structure of OLEDs. Optical design is related to the optical properties, such as the efficiency, emission spectra, and color coordinates of OLED devices because of the microcavity effect in top-emitting OLEDs. In this study, the properties of top-emitting blue OLEDs were optimized by adjusting the thicknesses of the thin metal layer and capping layer (CPL). Deep blue emission was achieved in an OLED structure with a second cavity length, even when the transmittance of the thin metal layer was high. The thin metal film thickness ranges applicable to OLEDs with a second microcavity structure are wide. Instead, the thickness of the thin metal layer determines the optimized thickness of the CPL for high efficiency. A thinner metal layer means that higher efficiency can be obtained in OLED devices with a second microcavity structure. In addition, OLEDs with a thinner metal layer showed less color change as a function of the viewing angle.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.461-464
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• 2008

We have developed low voltage driving red phosphorescent organic light-emitting devices using a new electron transport layer. $Ir(piq)_3$ and CBP were used as a phosphorescent dopant and an emission host, respectively. The device exhibits a luminance of $1000\;cd/m^2$ at a voltage of 2.8 V. This high luminance at low voltage results from a high electron conduction behavior of the new electron transport layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.571-576
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• 2006

We review work performed by our group and collaborators in the area of exciton formation. There are three components: (i) measurement of singlet fractions, (ii) analysis of magnetic resonance measurements, and (iii) models of exciton formation. We find that the fraction of singlet excitons is a controllable quantity, pointing the way to a new generation of all-fluorescent organic light emitting devices.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1015-1018
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• 2008

Tandem organic light-emitting diodes (OLEDs) do not always improve power efficiency over their conventional OLED counterparts. When a tandem OLED utilizes optimized EL units, increased power efficiency can only be achieved if the intermediate connector in the device has excellent charge injection capability.