• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.225-228
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• 2009

We have demonstrated several effective intermediate connectors in tandem organic light-emitting devices (OLEDs) using doped or nondoped organic p-n heterojunction. The influence of n-type or p-type organic layer in intermediate connectors on device performance has been investigated based on the understanding of interfacial electronic structures.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.3
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• pp.53-57
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• 2001

The organic light-emitting devices (OLEDs) based on fluorescence have low efficiency due to the requirement of spin-symmetry conservation. By using the phosphorescent material, internal quantum efficiency can reach 100%, compared with 25% in the case of the fluorescent material. Thus, phosphorescent OLEDs have recently been extensively studied and shown higher internal quantum efficiency than the conventional OLEDs. In this study, we investigated the characteristics of the phosphorescent OLEDs with the green emitting phosphor, $Ir(ppy)_3$ (tris(2-phenylpyridine)iridium). The device with a structure of ITO/TPD$Ir(ppy)_3$ doped in BCP/BCP/$Alq_3$/Li:Al/Al was fabricated, and its electrical and optical characteristics were studied. By changing the doping concentration of $Ir(ppy)_3$, we fabricated several devices and investigated their characteristics.

• Journal of the Korean Applied Science and Technology
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• v.19 no.2
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• pp.97-102
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• 2002

Recently, the phosphorescent organic light-emitting devices (OLEDs) have been extensively studied for their high internal quantum efficiency. In this study, we synthesised several phosphorescent metal complexes, and certified their composition using NMR. We also investigated the characteristics of the phosphorescent OLEDs with the green emitting phosphor, $Ir(ppy)_{3}$. The devices with a structure of indium-tin-oxide(ITO)/N,N'-diphenyl-N,N'-(3-methylphenyI}-1,1'-biphenyl-4,4'-diamine (TPD)/metal complex doped in host materials/2,9-dimethyl-4,7-diphenyl-l,10-phenanthroline(BCP)/tris (8-hydroxyquinolinato) Aluminum($Alq_{3}$)/Li:Al/Al was fabricated, and its electrical and optical characteristics were studied. By changing the doping concentration of tris(2-phenylpyridine)iridium ($Ir(ppy)_{3}$), we fabricated several devices and investigated their characteristics.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.623-624
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• 2004

The coating and estimation of gas and moisture barriers on polymer and glass substrates are receiving very much attention in passivation of organic light emitting devices (OLEDs). In this study, the encapsulation and lifetime measurement techniques of OLEDs were presented. The degradation mechanisms of bare and encapsulated OLEDs were investigated by the visual lifetime measurement (VLM) system with the parameters such as a pixel luminance(L), a luminance rms roughness(dL), a brightness area ratio(R), an edge degradation depth(D), etc.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1024-1027
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• 2006

The electrical and the optical properties of organic light-emitting devices (OLEDs), with and without various kinds of multiple heterostructures were investigated. The efficiency in green OLEDs were significantly enhanced by the structure of the multiple heterostructures acting as a hole transport layer (HTL) rather than by the number of periods. These results indicate that highly efficient green OLEDs utilizing multiple heterostructures acting as a HTL can be fabricated.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.701-705
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• 2002

In order to realize full color display, two approaches were used. The first method is the patterning of red, green, and blue emitters using a selective deposition. Another approach is based on a white-emitting diode, from which the three primary colors could be obtained by micro-patterned color filters. White-light-emitting organic light emitting devices (OLEDs) are attracting much attention recently due to potential applications such as backlights in liquid crystal displays (LCDs) or other illumination purposes. In order for the white OLEDs to be used as backlights in LCDs, the light emission should be bright and have Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.33, 0.33). For obtaining white emission from OLEDs, different colors should be mixed with proper balances even though there are a few different methods for mixing colors. In this study, we will report a white organic electroluminescent device based on an incomplete energy transfer. In which the blue and green emission come from the same layer via incomplete energy transfer.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.1
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• pp.11-15
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• 2016

The organic light emitting diodes (OLEDs) have been studied as large flexible displays, light source and hard wares of internet of things. However, OLEDs show some drawbacks in terms of external environments due to the low work function of the metals and the reactive organic materials. In particular, the operation functions of the OLEDs tend to deteriorate rapidly by exposing the oxygen and moisture. So as to prevent it, domestic and overseas studies underway in various method such as ALD, PVD, CVD. But it has complex process and high cost. Therefore In order to protect devices from the external environments, it is important to develop the passivation thin films of low-cost and simple process which can prevent the devices from the penetration of the oxygen and moistures. In this study, to improve the reliability, passivation thin films were coated onto the green OLEDs by spin coating method and investigated the changes of the optical properties of the prepared devices at various doping concentrations of sodium alginate (SA). The passivation solutions were synthesized by using polyvinyl alcohol (PVA) host material with a dopant of SA which were added with the amounts of 10, 20 and 40 wt% into the PVA. As a result, the best barrier properties of the OLEDs were obtained for the samples with 40 wt% SA. Finally, the passivation films can be optimized by using the mixture solution of PVA and SA materials.

• Journal of the Korean Applied Science and Technology
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• v.18 no.3
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• pp.186-190
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• 2001

By fabricating the organic light-emitting devices (OLEDs) based on phosphorescent material, the internal quantum efficiency can reach 100%, compared to 25% in the case of the fluorescent material. Thus, the phosphorescent OLEDs have recently been extensively studied and showed higher internal quantum efficiencies then the conventional OLEDs. In this study, we investigated the characteristics of the phosphorescent OLEDs, with the green emitting phosphor, $Ir(ppy)_{3}$, (tris(2-phenylpyridine)iridium). The devices with a structure of $ITO/TPD/Ir(ppy)_{3}$ doped in the host material $/BCP/Alq_{3}/Li:Al/Al$ were fabricated, and its electrical and optical characteristics were studied. By changing the doping concentration of $Ir(ppy)_{3}$, we fabricated several devices and investigated the device characteristics. OLEDs doped into BCP by 10% showed the best characteristics. For 10% doped OLEDs, the maximum luminance of was over 10000 $cd/m^{2}$, and the maximum power efficiency was 7.14 lm/W.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.348-351
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• 2004

We describe a new approach for building organic light-emitting diodes (OLEDs), which is based on physical lamination (i.e. soft contact lamination (ScL)) of thin metal electrodes supported by an elastomeric layer (polydimethylsiloxane) against an electroluminescent organic. We find that the devices fabricated have much better performance than those constructed with conventional vacuum deposition process. In addition, the ScL is intrinsically compatible with the technique of soft lithograph so that it is easy to build patterned OLEDs with feature sizes into the nanometer regime.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1429-1431
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• 2005

Organic molecular-beam deposition of Mg:Ag thin films with a low Mg concentration on tris (8-hydroxyquinolino) aluminum $(Alq_3)$ layers at room temperature was performed to investigate the feasibility of using Mg:Ag thin films as cathode electrodes in organic light-emitting devices (OLEDs). The effective barrier height of the $Mg:Ag/Alq_3$ heterointerface, determined from current-voltage measurements, was as low as 0.23 eV. These results help improve understanding the electrical properties of the $Mg:Ag/Alq_3$ heterointerfaces in OLEDs.