• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.725-729
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• 2015

Organic light emitting diodes (OLEDs) are regarded as the next generation display and solid-state lighting due to their superb achievements from extensive research efforts on improving the efficiency and stability of OLEDs in addition to developing new materials. Herein, efficient green phosphorescent OLEDs were obtained by using hexaazatrinaphthylene (HAT) derivatives as a hole injection layer. External quantum and current efficiencies of OLEDs were enhanced from 8.8% and 30.8 cd/A to 13.6% and 47.7 cd/A, respectively by inserting a thin layer of HAT derivatives between the ITO and hole transporting layer. The enhancement of OLEDs was found to be originated from the inserted HAT derivatives, which resulted in the optimized hole-electron balance inside the emission layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.269-271
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• 2004

In this report, high-performance organic light-emitting diodes (OLEDs) with polytetrafluoroethylene (Teflon) buffer layer are demonstrated. Compared with conventional buffer layer, copper phthalocaynine (CuPc), Teflon film shows lower absorption in the wavelength from 200nm to 800nm The OLEDs with Teflon and CuPc buffer layer were fabricated under same conditions, and the device performances were compared. The results indicate that when the thickness of Teflon is 1.5nm, the performance of OLEDs is greatly enhanced with an efficiency of 9.0cd/A at the current density of 100mA/$cm^2$, while the device with an optimized 30-nm-thick CuPc buffer layer only shows an efficiency of6.4cd/A at the same current density.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.609-612
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• 2008

Characteristics of indium-zinc-oxide (IZO)-Ag-IZO multilayer grown on a PET substrate were investigated for flexible organic emitting diodes. By inserting very thin Ag layer between amorphous IZO, IZO-Ag-IZO (IAI) multilayer anode exhibited remarkably reduced sheet resistance and high transmittance due to the surface plasmon resonance effect and Ag layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.620-622
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• 2004

In this study, a mono-chelated compound as novel blue light emitting material, $BPh_2$(pbi) (pbi = 2-(2-Pyridyl)benzimidazole) was synthesized Organic light emitting Diodes (OLEDs), which has a ITO/NPB(40 nm)/Boron(30 nm)/$Alq_3$(1 nm)/Liq(3 nm)/Al(150 nm) structure, has been fabricated. The maximum brightness of the device is up to about 900 cd/$m^2$ and 0.54 cd/A at 11.5 V. The EL peaks and CIE coordinates of our OLEDs is 457 nm and (0.26, 0.29), respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1813-1818
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• 2006

We demonstrate a new approach to form gradient hole injection layer (HIL) in organic light-emitting diodes (OLEDs). Single spincoating of hole-injecting conducting polymer compositions with a perfluorinated ionomer results in gradient workfunction through the layer by self-organization, which lead to remarkably efficient single layer polymer light-emitting diodes (PLEDs) (${\sim}21$ cd/A). The device lifetime was significantly improved (${\sim50$ times) compared with the conventional hole injection layer, poly(3,4-ethylenedioxy-thiophene)/polystyrene sulfonate. This solution processed HIL also produced dramatically enhanced luminous efficiency (${\sim}34$ cd/A) in vacuum- deposited green fluorescent OLEDs while the vacuum deposited HIL gave the luminous efficiency of ${\sim}23$ cd/A in the same device structure.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.127-128
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• 2000

Organic light-emitting diodes(OLEDs) are constructed using multilayer organic thin films. The hole-transport layer is PVK and the emitting material is rubrene and $Alq_3$. The emitting layer is doped with rubrene partially. As the partially-doped layer migrate from the interface PVK/emitting layer, the emission peak of rubrene decrease and diminish. By comparing with the previous reports, we propose the zero-field hole injection barrier at ITO/PVK interface and hole-trapping effect of rubrene in host materials as predominant factor to determine the emission zone.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1088-1091
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• 2001

Temperature-dependent current-voltage characteristics of Organic Light-Emitting Diodes(OLEDs) were studied. The OLEDs were based on the molecular compounds, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1, 1'-diphenyl-4, 4'-diamine (TPD) as a hole transport and trim(8-hydroxyquinoline) alulninum(Alq$_3$) as an electron transport and emissive material. The current-voltage characteristics were measured in the temperature range of 10[K] and 300[K]. A conduction mechanism in OLEDs was interpreted in terms of tunneling and trap-filled limited current.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.370-373
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• 2001

Temperature-dependent current-voltage characteristics of Organic Light-Emitting Diodes(OLEDs) were studied. The OLEDs were based on the molecular compounds, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) as a hole transport and tris(8-hydroxyquinoline) aluminum($Alq_3$) as an electron transport and emissive material. The current-voltage characteristics were measured in the temperature range of 10[K] and 300[K]. A conduction mechanism in OLEDs was interpreted in terms of tunneling and trap-filled limited current.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.370-373
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• 2001

Temperature-dependent current-voltage characteristics of Organic Light-Emitting Diodes (OLEDs) were studied. The OLEDs were based on the molecular compounds, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) as a hole transport and trois(8-hydroxyquinoline) aluminum(Alq$_3$) as an electron transport and emissive material. The current-voltage characteristics were measured in the temperature range of 10[K] and 300[K]. A conduction mechanism in OLEDs was interpreted in terms of tunneling and trap-filled limited current.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.118-120
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• 2009

We reported that the evidence of oxygen doping to copper-phthalocyanine (CuPc) by $O_2$-plasma treatment to Au electrode of inverted top emitting organic light emitting diodes (ITOLEDs). The operation voltage of OLEDs at 150 mA/$cm^2$ decreased from 16.1 to 10.3 V as oxygen atoms indiffued to CuPc layer using $O_2$-plasma. Synchrotron radiation photoelectron spectroscopy results showed that a new bond of Cu-O appeared and the energy difference between the highest occupied molecular orbital and $E_F$ is lowered by 0.20 eV after plasma treatment. Thus the hole injection barrier was lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs.