• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.70-76
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• 2016

Commercialization of surface lighting using Light Emitting Diodes (LED) has embraced the advance to Organic Light Emitting Diode (OLED) technology. This is necessary to achieve light-efficiency-improvement and longer component life. The range of application of LED lighting for both interior and outdoor lights has been gradually expanding. Automobiles and home appliances are now included. In the case of LED surface lighting in a domestic refrigerator, achieving high efficiency requires optimization of the number of LEDs in a pack. Optimization is also required in the design stage of development with regard to the conversion of the light source type from point light sources to the surface light type. This paper addresses these design problems. It presents a study of brightness variations for design solutions that differ from the existing technology in both the number of LED packages and use of Light Gathering Power (LGP) information. The intention is to facilitate production of high brightness LED surface lighting for domestic refrigerators.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.812-815
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• 2003

In this study, the MgO thin-film passivation layer was adopted to protect passive matrix organic light emitting diode(PMOLED) with the cathode separator from moisture and oxygen. Using the substrate rotate and tilt technique during the deposition, the organic and cathode layers were perfectly covered with MgO. And then, we analyzed the difference of the current-voltage and luminescence characteristics between passivated OLED of the MgO and non-passivated OLED. It was found that the number of dark spot generated from the degradated pixel was decreased owing to the Mgo thin-film passivation layer using the tilt ＆ rotate technique. And the half-life time passivated OLED was improved two times more. Thus, the MgO could be vaccum-deposited under the low temperature and had a merit that the organic layer was not much affected. We can consider that MgO thin film passivation method can be adopted to protect the OLED from moisture and oxygen and can offer the enhancement of lifetime.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1549-1552
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• 2006

We report a new series of blue dopants composed of both electron donating and electron accepting moieties in one molecule, based on nalidixic acid. The EL device derived from the dopant exhibits pure blue light emission (0.15, 0.14) The current efficiency is estimated to be 3.88 cd/A at 100 $cd/m^2$, which shows remarkable enhancement, compared to that of the host itself (2.5 cd/A at 100 $cd/m^2$) under the same conditions. These results demonstrate that the incorporation of a proper guest into the host in a guest-host doped system improves not only the purity of the fluorescent blue emission but also elevates its quantum efficiency, thus improving the OLED performance.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.2
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• pp.25-31
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• 2009

The image processing methods are widely used in many industrial fields to detect defections in inspection devices. In this study an image processing method was conducted for the detection of abnormal pixels in a OLED(Organic Light Emitting Diode) type panel which is used for small size displays. The display quality of an OLED device is dependent on the pixel formation quality. So, among the so many pixels, to find out the faulty pixels is very important task in manufacturing processing or inspection division. We used a line scanning type BW(Black & White) camera which has very high resolution characteristics to acquire an image of display pixel patterns. And the various faulty cases in pixel abnormal patterns are considered to detect abnormal pixels. From the results of the research, the normal BW pixel image could be restored to its original color pixel.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.11a
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• pp.107-110
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• 2003

The aim of this study is to map the intellectual structure of the field of Organic Light Emitting Diode(OLED). Co-word analysis was employed to reveal patterns and trends in the OLED field by measuring the association strengths of terms representative of relevant publications or other texts produced in OLED field. Data were collected from INSPEC. Important keywords were extracted from author keywords. These author keywords were further standardized. In order to trace the dynamic changes of the OLED field, present the technology mapping. The results show that the OLED field has some established research theme and it also changes rapidly to embrace new themes.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.391.1-391.1
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• 2014

광물질로 인광물질을 사용한 유기발광다이오드(Organic Light Emitting Diode, OLED)는 재결합에 의해 형성된 여기자를 발광에 모두 이용할 수 있기 때문에 내부 양자효율이 100%로 알려져 있다. 하지만 유기층에서 발생된 빛이 소비자에게 전달되기까지의 경로에서 발생되는 wave guiding effect로 인해, 발생된 빛의 20%만이 전달된다. 특히 bottom emission type의 OLED에서 glass와 air사이의 굴절률이 달라 발생되는 전반사에 의해 손실되는 빛의 양은 35%에 달한다. 따라서 본 연구에서는 glass와 air사이의 전반사를 줄이고 광추출을 위해 습식 방법으로 hemisphere type의 ZnS를 제작하였다. 제작된 ZnS는 직경 200nm까지 성장하였으며, 이렇게 제작된 ZnS nano lens가 적용된 OLED device에서 휘도가 20% 이상 향상되는 것을 확인하였다.

• Transactions on Electrical and Electronic Materials
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• v.11 no.2
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• pp.85-88
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• 2010

Deep blue organic light emitting diodes (OLEDs) were fabricated using 5 wt.% doped BCzVBi with various blue host materials such as NPB, DPVBi, MADN and TPBi. A blue OLED device, using DPVBi as host material, was constructed via NPB ($500\;{\AA}$) / DPVBi:BCzVBi ($200\;{\AA}$) / Bphen ($300\;{\AA}$) / LiF ($20\;{\AA}$) / Al ($1,000\;{\AA}$) and it shows a maximum luminescence of $4,838\;cd/m^2$, a current density of $32.7\;mA/cm^2$, a luminous efficiency of 3.3 cd/A and CIExy coordinates of (0.19, 0.15) at 4.5 V whereas the luminous efficiencies and CIExy coordinates of other blue OLEDs using NPB, MADN and TPBi as host materials have 1.1, 2.6 and 2.0 cd/A and (0.15, 0.11), (0.15, 0.10) and (0.15, 0.10), respectively. Energy transfer mechanisms between BCzVBi and its host materials were discussed with an energy band structure of host materials.

• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1569-1574
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• 2005

To develop new hole-blocking materials for phosphorescent organic light-emitting diodes (PhOLEDs), 5,6-dihydro-2,9-diisopropyl-4,7-diphenyl[1,10]phenanthroline (1) and 5,6-dihydro-2,9-diisopropyl-4-(4-methoxyphenyl)-7-phenyl[1,10]phenanthroline (2) were synthesized. While the absorption spectrum of 1 is very similar to that of 2, the photoluminescence spectrum of 1 has the feature of the narrower and blue-shifted blueviolet emission at the peak of 356 nm compared to that of 2. The HOMO and LUMO energy levels of 1 and 2 were estimated from the measurement of cyclic voltammetry, and 1 has the appropriate levels for a holeblocking layer (HBL). The use of 1 as a HBL in a green PhOLED led to good efficiency of 23.6 cd/A at 4.4 mA/$cm^2$.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.5
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• pp.594-600
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• 2014

A threshold voltage compensation pixel circuit was developed for active-matrix organic light emitting diodes (AMOLEDs) using amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO-TFTs). Oxide TFTs are n-channel TFTs; therefore, we developed a circuit for the n-channel TFT characteristics. The proposed pixel circuit was verified and proved by circuit analysis and circuit simulations. The proposed circuit was able to compensate for the threshold voltage variations of the drive TFT in AMOLEDs. The error rate of the OLED current for a threshold voltage change of 3 V was as low as 1.5%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.9
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• pp.802-807
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• 2007

We have developed red phosphorescent top emission organic light-emitting diodes with transparent metal cathodes deposited by using thermal evaporation technique. Phosphorescent guest molecule, BtpIr(acac), was doped in host CBP for the red phosphorescent emission, Ca/Ag, Ba/Ag, and Mg/Ag double layers were used as cathode materials of top emission devices, which were composed of glass/Ni/2TNATA(15 nm)/${\alpha}$-NPD(35 nm)/CBP:BtpIr(acac)(40 nm, 10%)/BCP(5 nm)/$Alq_3$(5 nm)/cathodes. The optical transparencies of these metal cathodes strongly depend on underlying Ca, Ba, and Mg layers. These layers also strongly affect the electrical conduction and emission properties of the red phosphorescent top emission devices.