• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.22-25
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• 2000

ZnS:Cu,Cl 형광체의 여기 및 발광 스펙트럼 측정 결과 주게인 $Cl^-$ 이온과 받게인 $Cu^+$ 이온 사이의 흡수와 발광에 기인하는 peak과 국소화된 발광 중심인 $(CU_2)^{2+}$ 이온의 흡수와 발광에 기인하는 peak이 관측되었다. CuCl의 첨가량이 증가함에 따라 $Cu^+$ 이온의 농도가 증가하게 되어 $(Cu_2)^{2+}$ 이온에 기안하는 발광으로부터 공명 에너지 전달 (Resonant Energy Transfer)의 확률이 높아지기 때문에 513 nm를 중심으로 하는 발광의 세기가 증가하게 된다. 자체 제작한 ZnS:Cu,Cl 형광체를 이용하여 제작한 소자의 휘도 측정결과 400 Hz, 100 V 에서 CuCl 의 첨가량이 0.2 mole% 일 때 휘도가 최대였고, 진동수가 증가함에 따라 휘도가 포화되는 현상이 나타났다. CuCl의 첨가량이 증가함에 따라 513 nm를 중심으로 하는 발광이 강해지고 CIE 좌표값이 녹색영역으로 이동하게 된다. 진동수가 증가하면 인가된 전압의 유지 시간이 짧아지게 되어 발광의 감쇄시간이 긴 513 nm를 중심으로 하는 발광보다 감쇄시간이 짧은 458 nm를 중심으로 하는 발광이 강해지게 되고, CIE 좌표값이 청색영역으로 이동하게 된다.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1639-1646
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• 2014

A series of novel fused-ring spiro compounds, spiro[benzo[ij]tetraphene-7,9'-fluorene] (SBTF) derivatives containing an end-capping aryl substituent at both the C3 and C10-positions hasbeen designed and synthesized via multi-step Suzuki coupling reactions. 3-(1-Naphthyl)-10-phenylSBTF (1N-PSBTF), 3-(2-naphthyl)-10-phenylSBTF (2N-PSBTF) and 3-[4-(1-naphthyl)phenyl]-10-phenylSBTF (NP-PSBTF) showed improved glass transition temperatures ($T_g$) with good thermal stability. Their photophysical, electrochemical, and electroluminescent properties were investigated and were used to construct blue organic light emission diodes (OLEDs). The typical OLED devices showed excellent performance; the NP-PSBTF-based device exhibited highly efficient deep blue-light emission with a maximum efficiency of 5.27 cd/A (EQE, 4.63%) with CIE (x = 0.133, y = 0.144). According to these characteristics, these deep-blue light emitting materials have sufficient potential for fluorescent OLED applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2001.08a
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• pp.209-212
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• 2001

We report the synthesis and characterization of new alkoxy substituted spirobifluorene derivatives. The spiro compounds having alkoxy hydrocarbon chains were readily soluble in common organic solvents, having improved film-forming properties and had a significantly reduced tendency to crystallize, resulting in increasing their service lifetime. The results of DSC showed that it was amorphous. The optical and electroluminescent spectra were characterized. Electroluminescence (EL) properties of three-layer light emitting diodes (LED) of $ITO/TPD/spirobifluorene/Alq_3/LiF/Al$ as the active layer were characterized. Blue emission peaking of the EL spectrum of the three-layer device at 402 nm and a luminance of 3,125 $cd/m^2$ were achieved at a drive voltage 12.8 V. The luminous efficiency was obtained to be 1.7 lm/W. The color coordinate in CIE chromaticity is (0.16, 0.09), which is in a pure blue region. The external quantum efficiency was obtained to be 2.0%. The results indicate that the spirobifluorene compounds having alkoxy hydrocarbon chains are strongly potential blue emitters for LED applications.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1609-1611
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• 2002

Multi-layer organic electroluminescent(EL) devices with Al-CsF composite as a cathode were fabricated. This device privides low driving voltage and high quantum efficiency. CsF is evaporated onto and diffuse into electron transport layer. $Alq_3$. The Fermi level of $Alq_3$ moves towards the LUMO level.

• Journal of Information Display
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• v.8 no.2
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• pp.20-24
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• 2007

Efficient white organic light-emitting diodes are fabricated with the blue and red electroluminescent (EL) units electrically connected in a stacked tandem structure by using a transparent doped organic p/n junction. The blue and red EL units consist of the light-emitting layer of 1,4-bis(2,2-diphenyl vinyl)benzene (DPVBi) and 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j] quinolizin-8-yl)vinyl]-4H-pyran) (DCM2) doped tris(8-hydroxyquinoline) aluminum $(Alq_3)$, respectively. The organic p-n junction consists of ${\alpha}-NPD$ doped with $FeCl_3$ (15 % by weight ratio) and $Alq_3$ doped with Li (10 %). The EL spectra exhibit two peaks at 448 and 606 nm, resulting in white light-emission with the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.36, 0.24). The tandem device shows the quantum efficiency of about 2.2 % at a luminance of 100 $cd/m^2$, higher than individual blue and red EL devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.8
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• pp.679-687
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• 2001

It is known that amorphous BaTiO$_3$ thin films have good insulating properties[1][2]. In this investigation, amorphous BaTiO$_3$ thin films were deposited by rf magnetron sputtering on thick BaTiO$_3$ films of AC powder EL devices which were fabricated by screen-printing. The electrical and optical properties of the EL devices were then investigated. Adding amorphous BaTiO$_3$ thin film, it showed that leakage current density was decreased. Especially, leakage current density was decreased more with he sample of 0.5-hour deposition than the sample of 4-hours deposition. This result led to the improvement of luminous efficiency by 11%. It could be concluded that proper amorphous BaTiO$_3$ thin film deposition improved the surface property of dielectric layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.465-465
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• 2008

Conjugated polymers have attracted much scientific and technological research interest during the past few decades because of their potential use such as polymer light-emitting diodes (PLEDs).1,2 Particularly, lots of phenylene-based polymers such as polyfluorene and its derivatives have been synthesized because of their high photoluminescence quantum efficiencies and thermal stabilities. However, troublesome long wavelength emission in polymer film of polyfluorenes on heating during device formation or operation has been the crucial problem for practical applications. The source of the long wavelength emission was initially believed to be solely due to excimer emission as a result of polymer aggregation. It has also recently been correlated with emissions from ketonic defects in the fluorene units. Many efforts have been made to reduce the tendency to red-shifted emission. Here, we report for the first time the design and synthesis of novel 9,9-spiro bifluornene-based polymers containing heteroatoms such as N, S in its molecular skeleton. Especially, the 9,9-spiro bifluornene-based polymers containing N atom showed stable blue electroluminescence, which did not show spectral change upon thermal annealing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.96-98
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• 1999

유기전계발광소자(OELD)의 성능 향상을 위한 많은 연구가 진행되고 있지만 아직까지 금속전극과 유기발 광층 사이의 접촉저항(Contact Resistance)에 관한 연구는 거의 보고되지 않고 있다. Ohmic 접합에서 접촉 저항은 효율적이고 신뢰성 있는 소자제작에 있어서 간과되어서는 안될 매우 중요한 부분이다. 본 연구에서는 금속전극과 유기발광충 사이의 접촉저항에 관해서 논의하고자 한다. 본 연구에서 제작된 샘플은 금속전극으로 Ag, 유기발광재료로서 Alq$_3$를 사용하였으며, Alq3의 두께를 100 $\AA$에서 500 $\AA$까지 각각 다르게 하여 서로 다른 두께의 유기발광층을 가지는 샘플을 제작하였다. 금속전극의 매트릭스 구조에 의해 형성된 적선의 크기는 3 mm x 2 mm이며, 제작된 샘플의 접촉비저항은 TLM(Transmission Line Measurement) 방법을 이용하여 구하였다. Planar한 TLM model로부터 새로운 vertical model을 유추하였으며, 이를 근거로 접촉저항 및 transfer length 등을 계산하였다. 상온에서 측정된 전체 저항값은 유기발광층의 두께가 증가함 에 따라 증가하는 경향을 나타냈으며, 이 때 계산된 접촉비저항은 1.49$\times$$10^1$ $\Omega$-$\textrm{cm}^2$ 이다. 접촉저항은 전극 사이의 거리의 증가에 따라 증가하지만, 측정시간의 thermal budget의 영향으로 상대적으로 전체저항이 감 소하였으나, 저항감소분의 포화에 따라서, 거리에 비례하여 다시 저항이 증가하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.514-516
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• 2003

We have fabricated an air stable blue emitting organic electroluminescent devices (OLEDs) with a carbazole based emitting molecule, Bis(3-N-ethylcarbazolyl)terephthalidene (BECP). Our device emits strong blue at 472 nm with the luminance efficiency of near 1 lm/W at a voltage and current density of 8 V and 5.7 mA/cm2, respectively, reaching the brightness up to 5000 cd/m2 at 270 mA/cm2. Finally, in order to tune the emission color from blue to green, we have used Bis(3-N-ethylcarbazolyl)cynoterephthalidene (BECCP), a derivative of BECP by adding cyno group in side chain, and compared the electroluminscence (EL) of OLEDS prepared by BECCP to that of BECP based OLEDs.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.327-331
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• 2014

LED(Light Emitting Diode) is a semiconductor device utilizing electroluminescent effect is a phenomenon in which a type of P-N junction diode, the light of short wavelength which a voltage is applied in the forward direction is released. LED is advantageous in reducing the energy as environmentally materials that can greatly reduce the carbon emissions, recent it has attracted attention IT(Information Technology) and GT(Green Technology) industry. In addition, there are advantages long life, high efficiency, and excellent response speed, LED have come into the spotlight as the illumination means to replace the existing fluorescent light and incandescent light bulb. When connecting to MR16 electronic transformer for existing LED driver circuit, due to malfunction of the dimmer and the electronic transformer, flicker occurs and linear dimming is not possible. Therefore, in this paper, we suggest an LED drive circuit there is no flicker with the corresponding dimming MR16 electronic transformer. Further, we explain the principles of the LED current control technique and the principle of the drive circuit of the LED, in order to validate the proposed circuit through prototyping and simulation.