• 한국응용과학기술학회지
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• 제20권4호
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• pp.316-323
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• 2003

Zinc complexes with bis[2-(o-hydroxyphenyl) naphtol [1,2] oxazolato ligands (ZnPBO-4) and its derivatives (ZnPBO-S) were synthesized, and luminescent properties of these materials were investigated. Both the fluorescent emission band and electroluminescent emission band were discussed based on their ligand structure differences. The emission band found that it strongly depends on the molecular structure of introduced ligand. It was tuned from 446 nm to 491 nm by changing the ligand structures. Spreading of the ${\pi}$-conjugation in 2-(o-hydroxyphenyl) group gives rise to a blue shift. The EL properties also showed good consistency with their differences of ligand structure. Bright-blue EL emission with a maximum luminance of 3,100 $cd/m^2$ at 12V, current density, 575 $mA/m^2$ was obtained from the organic light-emitting diodes (OLEDs) using ZnPBO-4 as emitting layer. It was also found that the newly synthesized materials were suitable to be used as emitting materials in organic EL device.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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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.

• Journal of Information Display
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• 제13권3호
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• pp.119-123
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• 2012

In this work, we report on a new monitoring method for an organic light-emitting diode (OLED) panel for lighting by optical sensing of the wave-guided light in the substrate. Using microlens array films, the wave-guided light was extracted into the edge or back side of the panel to be monitored by a photodiode. The luminance of the extracted light was measured as linearly proportional to the front light. Thus, by converting the extracted light into photo voltage, monitoring the luminance change occurring in the OLED is possible. Based on the results and concepts, we have proposed a photodiode-equipped driving circuit which can generate compensated driving current for uniform luminance of OLED panels.

• ETRI Journal
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• 제45권6호
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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.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.237-241
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• 2005

We present a device model for organic light emitting diodes(OLEDs) which includes charge injection, transport, recombination, and space charge effects in the organic materials. The model can describe both injection limited and space charge limited current flow and the transition between them. Calculated device current, light output, and quantum and power efficiency are presented for different cases of material and device parameters and demonstrate the improvements in device performance in bilayer devices. These results are interpreted using the calculated spatial variation of the electric field, charge density and recombination rate density in the device. We find that efficient OLEDs are possible for a proper choice of organic materials and contact parameters.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1143-1146
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• 2005

Novel series of electron-transporting hosts, pentavalent aluminum complexes containing 8 hydroxyquinoline ligands and various phenolato ligands were synthesized, and organic light-emitting diodes (OLEDs) were fabricated using these complexes as host materials of phosphorescent emitting device and the fabricated phosphorescent emitting device showed low driving voltage, high efficiency at high current density and good stability under conventional driving condition.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.362-367
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• 2011

Organic ($Alq_3$) film, which was coated on a donor plate, was transferred to an organic light emitting diode (OLED) substrate with help of heat generated by a dithering laser beam. The laser beam was diffracted in an acousto-optic modulator (AOM), then focused on the laser-to-heat converting layer of the donor plate; the focused spot followed trajectories guided by rotation of a Galvano-mirror. Three different functional waveforms, sine wave, square wave, and saw tooth wave were applied to the AOM as modulation signal to generate the dithering beam. The fluorescence microscope images of the donor plate showed that the patterns of removed $Alq_3$ film were affected considerably by the modulation waveforms and the phase difference between adjacent dithering beams. Further, the printed images of Alq3 film on the OLED substrate were different from the patterns of removed Alq3 film. Atomic force microscope images indicated that not only direct transfer but also deposition by sublimated vapor of Alq3 contributed to the pattern formation. Printed patterns affected considerably the electricity-to-light conversion characteristics of OLEDs. For uniform transfer, not only the phase relation of dithering beam lines but also adequate waveform were important.

• 센서학회지
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• 제30권5호
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• pp.309-313
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• 2021

Organic semiconductors have received tremendous attention for their research because of their tunable electrical and optical properties that can be achieved by changing their molecular structure. However, organic materials are inherently unstable in the presence of oxygen and moisture. Therefore, it is necessary to develop moisture and air stable semiconducting materials that can replace conventional organic semiconductors. In this study, we developed a NiO_x thin film through a solution process. The electrical characteristics of the NiO_x thin film, depending on the thermal annealing temperature and UV-ozone treatment, were determined by applying them to the hole injection layer of an organic light-emitting diode. A high annealing temperature of 500 ℃ and UV-ozone treatment enhanced the conductivity of the NiO_x thin films. The optimized NiO_x exhibited beneficial hole injection properties comparable those of 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN), a conventional organic hole injection layer. As a result, both devices exhibited similar power efficiencies and the comparable electroluminescent spectra. We believe that NiO_x could be a potential solution which can provide robustness to conventional organic semiconductors.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권1호
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• pp.8-12
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• 2005

Indium tin oxide(ITO) surface treated by Oxygen plasma has been in situ analyzed using XPS(X-ray Photoelectron Spectroscopy) and EDS(Energy Dispersive Spectroscopy), to investigate the relations between the properties of the ITO surface and the properties of OLED(Organic Light Emitting Diode). We measured electrical resistivity using Four-Point-Probe and calculated sheet resistance, and ITO surface roughness was measured by AFM(Atomic Force Microscope). We fabricated OLED using substrate that was treated optimum ITO surface. The plasma treatment of the ITO surface lowered the operating voltage of the OLED. We have obtained an improvement of luminance and decrease of turn-on voltage.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1703-1705
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• 2007

Before the ultra-violet glue encapsulation, the research evaporated LiF thin film on device surface to be the extra packaging layer for improving the lifetime of organic light-emitting diode. The formula of UV glue was specially developed. We found 100 nm LiF is the optimum thickness. The best lifetime obtained by using LiF and special UV glue is 2.4 times longer than those by commercial UV glue.