• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.745-753
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• 2013

Performance of organic light-emitting diodes incorporating microlens array was simulated using a Light Tools software. Use of microlens array can help the light to escape out of the device. We simulated a reference device that is consisted of reflection layer, emissive layer, and flat transparent substrate. And in this reference device, outcoupled efficiency of 22% was obtained. Several shapes of microlens were applied such as hemisphere, trapezoid, cone, and rectangular parallelepiped. The results showed the improvement of outcoupled efficiency of the device with microlens compared to that of the reference one. And from the analyses of the simulated data, the obtained appropriate shape of microlens is hemisphere, and the improvement of the device with hemispherical lens is 57% higher than that of the reference one.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.627-627
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• 2013

Recently, most studies concerning inorganic CdSe/ZnS quantum dot (QD)-polymer hybrid LEDs have been concentrated on the structure with multiple layers [1,2]. The QD LEDs used almost CdSe materials for color reproduction such as blue, green and red from the light source until current. However, since Cd is one of six substances banned by the Restriction on Hazardous Substances (RoHS) directive and classified into a hazardous substance for utilization and commercialization as well as for use in life, it was reported that the use of CdSe is not suitable to fabricate a photoelectronic device. In this work, we demonstrate a novel, simple and facile technique for the synthesis of ZnO-graphene quasi-core.shell quantum dots utilizing graphene nanodot in order to overcome Cd material including RoHS materials. Also, We investigate the optical and structural properties of the quantum dots using a number of techniques. In result, At the applied bias 10 V, the device produced bluish-white color of the maximum brightness 1118 cd/$m^2$ with CIE coordinates (0.31, 0.26) at the bias 10 V.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.29-29
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• 2012

Rhodamine chromophore/fluorophore have been attracted to many researchers due to its excellent photophysical properties. In this study, we have designed and synthesized a strong emissive fluorescent dye chemosensor for toxic elements. A rhodamine-based sensor was prepared by incorporation the rhodamine fluorophore and several functional host groups with high affinity to hazardous metal and anion. This sensor shows a high selectivity and an excellent sensitivity and is a dual-responsive colorimetric and fluorescent metal/anion-specific sensor. In addition, the 1:1 binding mode was proposed based on Job's plot method. Finally, computational calculation was simulated and calculated to approach for HOMO/LUMO of this dye chemosensor.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.167-168
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• 2008

Organic light emitting diodes (OLEDs) show a lot of advantages for display purposes. Because OLEDs provide white light emission with a high efficiency and stability, it is desirable to apply OLEDs as an illumination light source and back light in LCD displays. We synthesized new emissive materials, namely $Zn(HPB)_2$ and Zn(HPB)q, which have a low molecular compound and thermal stability. We studied white OLEDs using $Zn(HPB)_2$ and $Zn(PQ)_2$. The fundamental structures of the white OLEDs were ITO / NPB (40 nm) / $Zn(HPB)_2$ (40 nm) / $Zn(PQ)_2$ (20 nm) / LiAl (120 nm). As a result, we obtained a maximum luminance of $4200cd/m^2$ at a current density of $440mA/cm^2$. The CIE (Commission International de l'Eclairage) coordinates are (0.319, 0.338) at an applied voltage of 10 V.

• Journal of the Korean Applied Science and Technology
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• v.16 no.2
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• pp.127-133
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• 1999

New electroluminescent materials base on anthracene chromophore, [9.10-bis(${\alpha}$-naph -thylethenyl) anthracene (${\alpha}$-BNA)] were newly synthesized. The anthracene derivatives with bulky substituent possessed high melting point and they gave stable amorphous films through vacuum - sublimation methods. Three types of electroluminescent devices were fabricated with double layer and triple layer structure : ITO/TPD/emission layer/MgAg, ITO/emission layer/ OXD-7 and ITO/ TPD/ emission layer/OXD-7/MgAg, respectively. In three types of devices with the emissive layer of ${\alpha}$-BNA, efficient orange electroluminescence was observed. In the triple layer device whit a emitting layer of 20 nm thickness , maximum luminance was about 10000 cd/ $m^2$ at an applied voltage of 10v and maximum external quantum efficiency was 1.0%.

• Journal of Applied Reliability
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• v.9 no.2
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• pp.131-148
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• 2009

An organic light emitting diode (OLED), also light emitting polymer (LEP) and organic electro luminescence (OEL), is any light emitting diode (LED) whose emissive electroluminescent layer is composed of a film of organic compounds. The layer usually contains a polymer substance that allows suitable organic compounds to be deposited. They are deposited in rows and columns onto a flat carrier by a simple "printing" process. The resulting matrix of pixels can emit light of different colors. Such systems can be used in television screens, computer displays, small, portable system screens such as cell phones and PDAs, advertising, information and indication. OLEDs can also be used in light sources for general space illumination, and large-area light-emitting elements. In this paper, we develop the general guide line of the accelerated life test for assuring B10 life of AMOLED(Active Matrix Organic Light Emitting Diode) and PMOLED(Passive Matrix Organic Light Emitting Diode) which are widely used for display monitor less than 115 mm.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1470-1473
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• 2007

We have demonstrated the optimization of white organic light-emitting diodes with two separated emissive layers using a blue fluorescent and a red phosphorescent dopant. The maximum luminous efficiency of the devices showed 7.93, 9.70, 11.8, and 14.3 cd/A. The $CIE_{xy}$ coordinates also showed (x = 0.33, y = 0.36), (x = 0.33, y = 0.35), (x =0.31, y = 0.35), and (x = 0.29, y = 0.36) at 6V, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1399-1402
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• 2007

We have demonstrated efficient white WOLEDs by using three emissive materials for primary colors (red, green, and blue). The characteristics of WOLEDs showed the maximum luminance of $37600\;cd/m^2$ at 13V, the maximum luminous efficiency of 20.6 cd/A, and the $CIE_{xy}$ coordinates of (x = 0.33, y = 0.33) at 10V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.292-293
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• 2006

We have Investigated dielectric properties depending on bias voltage in organic lightemitting diodes using 8-hydroxyquinoline aluminum($Alq_3$) as an electron transport and emissive material. We analyzed the dielectric properties of organic light emitting diodes using impedance characteristics measurement by the auto-balancing bridge technique and equivalent cirrcuit of ITO/$Alq_3$/Al. Impedance characteristics was measured complex impedance Z and phase ${\theta}$ in the frequency range of 40 [Hz] to $10^8$ [Hz]. We obtained complex electrical conductivity, dielectric constant, and loss tangent ($tan{\delta}$) of the device at room temperature. From these analyses, we are able to interpret a conduction mechanism and dielectric properties contributed by an interfacial and orientational polarization.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.190-197
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• 2006

2파장 백색 발광층의 구성에서 청색 재료로 GDI602 또는 GDI602: GDI691(2%)을, 황색 재료로 Alq3:Rubrene(10%)를 사용하여 새로운 백색 유기발광다이오드를 제작하고 이들의 특성을 분석하였다. 제작된 소자들은 12V의 구동전압에서 GDI602/A1q3:Rubrene(10%) 발광층을 갖는 경우 약 $950\;Cd/m^2$의 휘도와 0.8 lm/W의 효율을, GDI602:GDI691(2%)/Alq3:Rubrene 발광층을 갖는 경우 약 $1800\;Cd/m^2$의 휘도와 1.2 lm/W의 효율을 나타내었다. 또한 발광 스펙트럼의 특성으로는 인가전압에 따라 중심파장의 위치는 일정하나 2파장 사이의 상대적 세기가 변화되었으며, 인가전압이 증가할 경우 CIE 색좌표가 청색 방향으로 다소 이동되었다. GDI602/ Alq3:Rubrene(10%) 발광층을 갖는 소자의 경우 9V에서 x=0.33, y=0.32로, GDI602:GDI691(2%)/Alq3:Rubrene 발광층을 갖는 소자의 경우 6V에서 x=0.32, y=0.33으로 순수 백색광에 가까운 특성이 얻어졌다.