• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2441-2445
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• 2009

The effects of Si -doped MgO have been investigated in order to improve the material properties of the MgO protective layer in plasma display panels. A small amount of Si is added to the MgO pellet while the MgO layer is being deposited by using an electron-beam evaporation method. Both the surface characteristics of the protecting layer and the electro-optical properties of 4 in. test panels are investigated, such as XRD patterns, SEM images, firing and sustain voltages, secondary electron emission coefficient($\gamma$), luminance, luminous efficacy and lifetime. The firing and sustain voltage are minimized when Si concentration is 0.038%, where the luminance and luminous efficacy increase up to 17% and 26% compared with that of the pure MgO film, separately, and lifetime also shows good characteristics.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1803-1804
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• 2006

In this paper, device performances of organic lightemitting diodes (OLEDs) will be presented for AMOLED and general illumination applications. Various types of advanced devices were developed to enhance the power efficacy and luminous efficiency. Here we also demonstrated longer lifetime AM-OLED structures, which lifetime is about 100 hours until $L/L_0$ reaches 0.99.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.272-276
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• 2004

Great strides in organic light emitting device (OLED) technology have resulted in a number of commercial products. To continue this growth into large area displays, for example televisions, an understanding of the mechanisms that drive the OLED device efficiency and lifetime performance is critical. In this work, we consider maximizing the efficiency lifetime product based on phosphorescent OLED ($PHOLED^{TM}$) technology. We report green PHOLEDs with luminous efficiency of 82 cd/A, 5.7 V and 10,000 hours lifetime at 1,000 cd/$m^2$,red PHOLEDs with CIE of (0.67,0.33), 11 cd/A and 35,000 hours lifetime at 500 cd/$m^2$ and recent progress in blue demonstrating efficiencies of 18 cd/A at 200 cd/$m^2$.

• Journal of Information Display
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• v.11 no.4
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• pp.154-159
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• 2010

Single-sustainer driving is an AC PDP driving scheme to reduce the circuitry by maintaining the sustain electrode at ground level. To date, however, the research on the discharge characteristics in such driving scheme is insufficient. In this study, the panel performance and discharge characteristics of the single-sustainer driving scheme were observed while varying the address electrode condition. In single-sustainer driving, the address electrode is strongly involved in the sustain discharge when the former is maintained at ground level, and the dependence of the luminous efficacy on the sustain voltage is different from that in the conventional driving scheme. The dependence of the luminous efficacy on the sustain voltage appeared similar, however, to that in the conventional driving scheme when the address electrode was floated in single-sustainer driving. In the investigation of the temporal evolution of the sustain discharge using an IICCD camera, it was found that the sustain discharge in single-sustainer driving with a floating address electrode is similar to that in the conventional driving scheme, and the strong plasma formation region was located in the vicinity of the MgO surface, which seems to be related to the lifetime of a PDP with single-sustainer driving. In the investigation of the operation characteristics, the PDP that was operated with a floated address electrode showed a narrower dynamic operation margin, but a longer lifetime was expected.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.257-262
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• 2007

Organic light-emitting diodes (OLEDs) with the high efficieney and long lifetime are of growing interest in next-generation displays. Among the factors influencing OLEDs properties, one of unstable factor is $Alq_3$ cationic species caused by the excess holes resided in $Alq_3$ layer. Therefore, we suppressed the accumulation of excess holes by using the mixed-hole transporting layer (MHTL) of NPB and CBP in multilayer green OLEDs. The devices with MHTL showed improved characteristics in the luminous efficiency and lifetime. More characteristics and the carrier transport mechanism will be discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.569-575
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• 2011

Since the high heat generation of LED chips can cause a reduction in lifetime, degradation of luminous efficiency, and variation of color temperature, studies have been carried out on the optimization of LED packaging and heat sinks. Recently, LED packages have been applied to high-power lights such as car headlamps or street lights, and it is known that cooling using only free convection is not at all efficient. Thus, in this study, a heat pipe with forced convection was examined for the optimization of the cooling performance in high-power LED lights. In addition, optimal on-off control of a fan was adopted to increase the fan lifetime, since the lifetime of the fan is generally shorter than that of the LEDs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.638-644
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• 2010

We have carry out numerical simulation of the electric-optical characteristics of organic light emitting diodes with gradient-doped emitting layer which were reported to be effective in improving luminous efficiency and lifetime. In this paper, the basic structure is comprised of ITO/NPB/$Alq_3$:C545T[%]/$Alq_3$/LiF/Al, six devices by separating the emitting layer of $Alq_3$:C545T[%] were studied. As the result, the uniformly-doped devices exhibited superior luminous efficiency-current density characteristics over conventional undoped device. In the case of gradient-doped devices, electric-optical characteristics were improved similar to uniformed-doped devices, unusually the distribution of traped-charge density in the OLED devices was shown as the staircase.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1138-1142
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• 2005

We achieved a highly efficient green OLED with an efficiency of 30cd/A by using a new electron transport material and optimizing the device structure. The luminous efficiency was 16.8lm/W at $3000cd/m^2$ and the lifetime was over 60,000hr at an initial luminance of $1000cd/m^2$. Furthermore, we obtained a threecomponent RGB white OLED by using the highly efficient green material. This RGB white OLED shows more excellent color reproducibility for full color displays with color filters, compared to a twocomponent white OLED.

• Transactions on Electrical and Electronic Materials
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• v.6 no.5
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• pp.221-224
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• 2005

To overcome of poor electron injection in organic light-emitting diodes (OLEDs) with Al cathode, a thin layer of inorganic insulating materials, like as LiF, is inserted between an Al cathode and an organic electron transport layer. Though the device, mentioned above, improves both turn on voltage and luminescent properties, it has some problems like as thickness restriction, less than 2 nm, and difficulty of deposition control. On the other hand, Li organic complex, Liq, is less thickness restrictive and easy to deposit and it also enhances the performance of devices. This paper reports the improved electron injection on OLEDs with another I A group metal complex, Potassium quinolate (Kq), as an electron injection material. OLEDs with organic complexes showed improved turn-on voltage and luminous efficiency which are remarkably improved compared to OLEDs with Al cathode. Especially, OLEDs with Kq have longer life time than OLEDs with Liq.

• Journal of the Korean Applied Science and Technology
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• v.32 no.1
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• pp.1-6
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• 2015

We investigated green phosphorescent organic light-emitting diodes with stepwise doping to improve efficiency roll-off and operational lifetime by efficient distribution of triplet excitons. The host material which was 4,4,N,N'-dicarbazolebiphenyl (CBP) of bipolar characteristic that can control the carrier in emitting layer (EML). When the EML devided into four parts with different doping concentration, each devices shows various efficiency roll-off and lifetime enhancement. The distribution of the carrier and excitons in the EML can be confirmed by using stepwise doping structure. The properties of device C exhibited luminous efficiency of 51.10 cd/A, external quantum efficiency of 14.88%, respectively. Lifetime has increased 73.70% compared to the reference device.