• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.252-256
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• 2009

We have developed low driving voltage white organic light emitting diode with a new electron transport material, triphenylphosphine oxide ($Ph_{3}PO$). The white light emission was realized with a rubrene yellow dopant and blue-emitting DPVBi layer. The new electron transport layer results in a very high current density at low voltage, resulting in a reduction of driving voltage. The device with a new electron transport layer shows a brightness of $1150\;cd/m^2$ at a low driving voltage of 4.3 V.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.8
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• pp.1627-1631
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• 2011

During a routine inspection of a large pump motor at power plant, white powder was found on the surface of the stator end windings. Visual inspection and high voltage insulation diagnosis was performed to determine whether this motor is available. The purpose of this paper is to understand the insulation properties of white powder found on high voltage stator and to know prevention of insulation weakness.

• 전자공학회논문지 IE
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• v.45 no.1
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• pp.1-6
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• 2008

In this paper, the white organic LED with two-wavelength was fabricated using the NPB of blue emitting material and a series of orange color fluorescent dye(Rubrene) by vacuum evaporation processes. The structure of white OLED was ITO/NPB$(200{\AA})$NPB:Rubrene$(300{\AA})$/BCP$(100{\AA})/Alq_3(100{\AA})/Al(1000{\AA})$ and the doping concentration of Rubrene was 0.75 wt%. We obtained the white OLED with CIE color coordinates were x=0.3327 and y=0.3387, and the maximum EL wavelength of the fabricated white organic light-emitting device was 560 nm at applied voltage of 11 V, which was similar to NTSC white color with CIE color coordinates of x=0.3333 and y=0.3333. The turn-on voltage is 1 V, the light-emitting him-on voltage is 4 V. We were able to obtain an excellent maximum external quantum efficiency of 0.457 % at an applied voltage of 18.5 V and current density of $369mA/cm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.6
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• pp.407-416
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• 2014

Five factors are identified, which affect the performance of optical filter: 1) type of optical glass, 2) existence of Fe, 3) photo pic coating type, 4) coating form, and 5) coating thickness. If we consider all the levels of five factors, there are 360 possible candidates. We determined five evaluation criteria, which can be used to evaluate possible candidates. For the performance measures we selected white-state avearge voltage, black-state average voltage, and black-state error rate. And we added economic criterion and quality and maintenance criterion. Through the two-step statistical analysis of white-state avearge voltage, black-state average voltage, and black-state error rates, we selected final four candidates. Based on the five criteria we finally determined optimal optical filter using AHP.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.25-26
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• 2008

In this paper, the white organic light-emitting diode(OLED)was fabricated using the DPVBi of blue emitting material and a rubrene of orange color of fluorescent dye by vacuum evaporation processes. The device structure of OLED was Glass/ITO/2T-NATA(15nm)/NPB(3nm)/DPVBi(3nm)/DPVBi rubrene[2%](10nm)/DPVBi(25nm)/$Alq_3$ or New-ETL(60nm) /LiF(0.5nm)/ Al(100nm). The device with the $Alq_3$, layer shows orange color, and the luminance of 1000cd/$m^2$ at an applied voltage of 10.4V. On the other hand, the New-En layer results in white color, CIE coordinates of (0.327, 0.323), and the lowered driving voltage of 5V for achieving the same luminance value.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1577-1582
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• 2006

Tandem OLED structures formed by connecting two or more low-voltage electroluminescent units (stacks) are effective for achieving high efficiency at low current density as well as long operational lifetime. We have fabricated white emitting tandem structures with two or three low-voltage white-emitting stacks using transparent organic "PN"-type connectors. Three- stack white tandem structures with efficiency greater than 24 cd/A at D65 and operational stability of about 110,000 h. (extrapolated) at $1000\;cd/m^2$ have been demonstrated. With a stacked structure, the power consumption for displays using an RGBW format can be reduced by 25% compared to previously described formulations. We have also fabricated advanced white tandem structures where the color gamut (NTSC x,y ratio) has been improved to greater than 70% using standard color filters. The white OLEDs can also be used to increase the colorrendering index CRI (>80%), an important consideration for solid-state lighting.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.5
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• pp.429-434
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• 2002

In this paper, multiheterostructure white organic light-emitting device was fabricated by vacuum evaporation. The structure of white organic light-emitting device is ITO/CuPc/TPD/DPBi:DPA/$Alq_3/Alq_3$:DCJTB/BCT/$Alq_3$/Ca/Al. Three primary colors are implemented with DPVBi, Alq$_3$and DCJTB. The maximum EL wavelength of the fabricated white organic light-emitting device is 647nm. And the CIE coordinate is (0.33, 0.33) at 13 V. In the fabrication of white organic light-emitting devices with DCJTB, $Alq_3$, DPVBi, the EL spectrum has two peaks at 492nm, 647nm. Two peaks appeared because the blue light is combined with green light. The maximum wavelength of red light is not changed with applied voltage. After voltage applied, for the first time, the electrons met the holes in the red emission layer and emitted red light. And then the electrons moved to the green emission layer, and blue emission layer continuously. Finally, when all of the emission layer activated, the white light is emitted.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1658-1660
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• 2007

We fabricate green device having unique life time characteristics of operating voltage reduction with time, ${\Delta}V_{op}$ <0. A green device needs lower voltage than initial voltage for sustaining constant current as life time goes on. It means there are two possible reasons; one is interface modification between anode and HIL due to oxygen plasma treatment and the other is bulk property modification due to combination of new green host and new green dopant. From these materials and oxygen plasma treatment, we can make white OLED device having the characteristics of low ${\Delta}V_{op}$ increasing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.100-101
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• 2008

We have developed low voltage driving white organic light emitting diode with new electron transport layer. The with light emission was realized with a yellow dopant, rubrene and blue-emitting DPVBi layer. The new electron transport layer results in very high current density at low voltage, causing a reduction of driving voltage. The device with new electron transport layer shows a brightness of 1000 cd/m2 at 4.3 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.343-346
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• 2001

To implementation of white electroluminescnet device in this paper, two methods were tried without synthesis of new white EL phosphor. At first, ZnS:Mn,Cl was mixed with ZnS:Cu from 20 to 50 weight percents. Second, ZnS:Mn,Cl was mixed with blue dye from 0 to 1.2 weight percents. The devices for experiments were measured as following; current-voltage, emission spectrum, brightness-voltage and CIE coordinate system and frequency properties.