• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.91-94
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• 2022

Top emission organic light-emitting diode is commonly used because of high efficiency and good color purity than bottom - emission organic light-emitting device. Unlike BEOLED, TEOLED contain semi-transparent metal cathode. Because of semi-transparent cathode, micro cavity effect occurs in TEOLED. We optimized this effect by changing the thickness of hole injection layer. Device consists of is indium-tin-oxide / N,N'-Di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine (x nm) / tris-(8-hydroxyquinoline) aluminum (50nm) / LiF(0.5nm) / Mg:Ag (1:9), and we changed NPB thickness which is used as HTL in our device in order to study how micro cavity effects are changed by optical path. As the results, NPB thickness at 35nm showed the current efficiency of 8.55Cd/A.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.37-40
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• 2000

This paper has been studied on characteristics of organic light-emitting device with various cathode materials. These catode materials were Al：Li(5%), Al, Cu, CsF/Al. And in these devices, HTL(hole transfer layer) was TPD and EML(emitting layer) was Alq$\sub$3/. We studied the I-V characteristics for each device. And then, the turn-on voltage of device for Al-Li(5%), Al, Cu, CsF/Al cathode were 7, 9, 13, 3V respectively. So, the CsF/Al cathode is superior to other cathode materials for I-V characteristics.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1587-1590
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• 2006

Through the engineering of recombination region and energy transfer in organic light emitting device, blue and red light emitting device with good color stability has been successfully obtained. A Color control layer (CCL), which emits green light through the energy transfer from the emission layers, has been introduced into the blue and red light emitting device for RGB white OLED. The RGB white OLED showed the current efficiency of 13 cd/A and the CIE coordinates of (0.33, 0.38) at $1000\;cd/m^2$. The device exhibited very stable spectrum with respect to operating current density and the CIE coordinates varied from (0.34, 0.38) to (0.31, 0.37) for $100-22000\;cd/m^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.10
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• pp.850-853
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• 2009

We have optimized the device structure by using the dielectric layer such as anti-reflection thin film to improve the emitting efficiency of white organic light emitting device (WOLED). Basically, dielectric layer with anti-reflection characteristics can enhance the emitting efficiency of WOLED by compensating the refractive index of organic layer, ITO, and Glass. Here, WOLED was designed and optimized by Macleod simulator. The refractive index of 1.74 was calculated for Dielectric layer and was selected as $TiO_2$. The optimal thicknesses of $TiO_2$ and ITO were 119.3 and 166.6 nm, respectively, at the wavelength of 600 nm. The transmittance of ITO was measured with the thickness variation of dielectric layer and ITO in Organic layer/ITO/Dielectric layer structure. The transmittance of ITO was 95.17% and thicknesses of $TiO_2$ and ITO were 119.3 and 166.6 nm, respectively. This result, calculated and measured values were coincided.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.834-836
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• 2009

We investigated the device performance for organic light-emitting characteristics based on the electron-injecting interfacial characteristics of Ba deposited on tris(8-quinolinolato)aluminum (III) ($Alq_3$) with a change of a Ba coverage. The device performance of organic light-emitting diodes with Ba coverage of 1 nm significantly improved by the lowering of the electron-injecting barrier height that was induced by electronic charge transfer. However, the device with Ba coverage above 1 nm showed poor device performance. The spectroscopic results indicated that the $Alq_3$ molecules started to decompose by the reaction between Ba and the phenoxide moiety of the molecule.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.350-354
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• 2018

Lifetime study of blue phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes was carried out to understand the dominant degradation process during electrical operation of the devices. Doping concentration dependence of the phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes was studied, which demonstrated long lifetime at low doping concentration in the phosphorescent devices and at high doping concentration in the thermally activated delayed fluorescent devices. Detailed mechanism study of the two devices described that triplet-triplet annihilation is the main degradation process of phosphorescent organic light-emitting diodes, whereas triplet-polaron annihilation is the key degradation factor of the thermally activated delayed fluorescent devices.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.466-466
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• 2013

Quantum-dot materials have introduced novel applications in organic light-emitting diodes and solar cells. The size controllability and structure modifications have continuously been upgrading the applicability to optoelectronic and flat-panel displays. In particular, quantum-dot organic light-emitting diodes (QLEDs) are a device driven through the electrical field applied to the electrical diodes. The QLEDs are affected by the constituent materials and the corresponding device structures. Conventionally, the electrical properties are characterized only in terms of dc-based current-voltage characteristics. The dynamic change in light-emitting diodes should be characterized in emitted and non-emitted states. Therefore, the frequency-dependent impedance can offer different information on the electrical performance in QLED. The current work reports an auxiliary information on the electrical and optical features originating from quantum-dot organic light-emitting diodes. The empirical characterizations are discussed towards an experimental tool in optimizing the light-emitting diodes.

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.84-87
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• 2011

We fabricated phosphorescent organic light-emitting devices with a 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) host layer. Two kinds of devices, one of ITO/TAPC/TAPC:FIrpic/TAZ/LiF/Al (device A) and one of ITO/TAPC:FIrpic/TAPC/TAZ/LiF/Al (device B), were prepared to investigate electrical and optical properties. Iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,$C^{2'}$]picolinate (FIrpic) and 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ) were used as a blue phosphorescent guest material and an electron transport layer, respectively. The TAPC layer in device B strongly contributes to whitish emission, higher driving voltage, and lower current efficiency characteristics compared with device A. The mechanisms of these electrical and optical characteristics of the devices were investigated.

• Transactions on Electrical and Electronic Materials
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• v.6 no.1
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• pp.25-28
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• 2005

We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate)(PEDOT:PSS) in a device structure of $ITO/PEDOT:PSS/TPD/Alq_{3}/cathode$. Polymer PEDOT:PSS buffer layer was made by spin casting method. Current-voltage, luminance-voltage characteristics and efficiency of device were measured at room temperature with a variation of cathode materials; Al, LiF/Al, LiAl, and Ca/Al. The device with LiF/Al cathode shows an improvement of external quantum efficiency approximately by a factor of ten compared to that of Al cathode only device. Our observation shows that cathode is important in improving the efficiency of the organic light-emitting diodes.