• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.439-442
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• 2008

A mixed host structure of TCTA and TPBI was used in orange emitting layer and host composition was critical to device performances of PHWOLEDs. PHWOLEDs with TPBI host in orange emitting layer showed high quantum efficiency of 10.3 % at $1000\;cd/m^2$ with little change of CIE coordinates of (0.32, 0.34) from $100\;cd/m^2$ to $10,000\;cd/m^2$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1143-1146
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• 2005

Novel series of electron-transporting hosts, pentavalent aluminum complexes containing 8 hydroxyquinoline ligands and various phenolato ligands were synthesized, and organic light-emitting diodes (OLEDs) were fabricated using these complexes as host materials of phosphorescent emitting device and the fabricated phosphorescent emitting device showed low driving voltage, high efficiency at high current density and good stability under conventional driving condition.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.127-128
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• 2000

Organic light-emitting diodes(OLEDs) are constructed using multilayer organic thin films. The hole-transport layer is PVK and the emitting material is rubrene and $Alq_3$. The emitting layer is doped with rubrene partially. As the partially-doped layer migrate from the interface PVK/emitting layer, the emission peak of rubrene decrease and diminish. By comparing with the previous reports, we propose the zero-field hole injection barrier at ITO/PVK interface and hole-trapping effect of rubrene in host materials as predominant factor to determine the emission zone.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.415-417
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• 2009

Color stable and efficient two wavelength white organic light emitting diodes (OLEDs) were fabricated using a iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,$C^2$'] picolinate (FIrpic) as a blue phosphorescent emitter and a bis(1-phenylisoquinolinato-$C^2$,N)iridium (acetylacetonate) ((piq)$_2$Ir(acac)) as a red phosphorescent emitter. The emitting layers consist of two blue emitting layers and one red emitting layer which is between the two blue layers. The device reaches the peak efficiencies of 7.84 % and 10.3 cd/A at 0.6 mA/$cm^2$. Furthermore, there was little change of EL spectra according to current density change in the device.

• Transactions on Electrical and Electronic Materials
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• v.15 no.5
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• pp.249-252
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• 2014

The aim of this work is to investigate the effect of $Ca_xSr_{2-x}$ and activator on the structural and luminescent properties of green-emitting $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ nano phosphor. Using urea as fuel and ammonium nitrate as oxidizer, $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ has been successfully synthesized, using a combustion method. The particles were found to be small, spherical and of round surface. SEM imagery showed that the phosphors particles are of nanosize. The $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ emission spectrum for 360 nm excitation showed a single band, with a peak at 490 nm, which is a green emission. The highest luminous intensity was at $1,000^{\circ}C$, which was obtained when the $Eu^{2+}$ content (y) was 0.05. The results support the application of $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor as a fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). Characteristics of the synthesized $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and photoluminescence (PL) detection.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.940-943
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• 2003

We report the fabrication and the characterization of white organic light-emitting devices consisting of a red-emitting layer of a new DCM derivative doped into 4,4'bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (${\alpha}-NPD$) and a blue-emitting layer of 1,4-bis(2,2-diphenyl vinyl)benzene (DPVBi). The device structure is ITO/PEDOT:PSS/${\alpha}-NPD$ (50 nm)/${\alpha}-NPD$:DCM (5 nm, 0.2 %)/DPVBi (x)/Alq3 (40 nm)/LiF (0.5 nm)/Al. The electroluminescence (EL) spectra consist of two broad peaks around 470 nm and 580 nm with the spectral emission depending on the thickness of DPVBi. The device with the DPVBi thickness of about 20 nm show a white light-emission with the Commission Internationale d'Eclairage(CIE) chromaticity coordinates of (0.33, 0.36). The external quantum efficiency is 2.6% and luminous efficiency is 2.0 lm/W at a luminance of 100 $cd/m^{2}$. The maximum luminance is about 30,270 $cd/m^{2}$ at 13.9 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.53-56
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• 2002

The effect of $\alpha$-septithiophene (${\alpha}-7T$) layers on the organic light emitting diode(OLED) was studied. The ${\alpha}-7T$ was used for a buffer layer in OLED. Hole injection was investigated and improved emission efficiency. The OLEDs structure can be described as indium tin oxide(ITO)/ buffer layer / hole transporting layer / emitting layer / electron transporting layer / LiF / Al. The hole transporting layer were composed of N,N-diphenyl-N,N-di(3-methylphenyl)-1,1-biphenyl-4,4-diamine(TPD), and N,N-di(naphthalene-1-ly)-N,N-diphenyl-benzidine( ${\alpha}$-NPD). The emitting layer, and electron transporting layer consist of tris(8-hydroxyquinolinato) aluminum($Alq_3$). All organic layer were deposited at a background pressure of less than $10^{-6}$ torr using ultra high vacuum (UHV) system. The ${\alpha}-7T$ layer can substitute the hole blocking layer, and improve hole injection properties.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.443-446
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• 2007

The novel blue light emitting material, 9,10-bis(3',5'-diphenylphenyl)anthracene (BDA) was synthesized by Suzuki coupling reaction and characterized by the measurements of 1H NMR, 13C NMR and FT-IR. The new anthracene derivative, which contains anthracene as a main core unit and 3',5'-diphenylphenyl group derivative as wings, has high fluorescence yield, good thermal stability, and high glass transition temperature at 188 oC. With the newly non-doped blue emitting material in the multilayer device structure, it was possible to achieve the current efficiency of 3.0 cd/A. The EL spectrum of the ITO/CuPc/α-NPD/BDA/Alq3/LiF/Al device showed a maximum wavelength (λmax) at 440 nm. The emitting color of device showed the blue emission (x,y) = (0.18,0.19) at 10 mA/cm2 in CIE (Commission Internationale de l'Eclairage) chromaticity coordinates.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.962-964
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• 1999

We studied emitting properties of devices fabricated using the spin-coating and Langmuir-Blodgett[LB] technique. The LB technique has the advantage of precise control of the thickness better than spin-coating method. Poly(3-hexylthiophene)[P3HT] LB films used as the emitting layer in light-emitting devices. LB monolayers were deposited 27 layers onto the indium-tin-oxide[ITO] as Y-type films by the vertical dipping method. The thickness is about 80nm. Absorption spectrum of LB films presented that P3HT is regiorandom conformation. Also, current-voltage-luminance characteristics and electroluminescence spectra of light-emitting devices fabricated by LB method is studied. In current-voltage-luminescence characteristics, turn-on voltage of P3HT LB film LEDs is higher than that of spin-coating LEDs. But electroluminescence spectrum is similar to the spin-coating LEDs. The orange-red light was clearly visible in a darkened room.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.316-323
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• 2003

Zinc complexes with bis[2-(o-hydroxyphenyl) naphtol [1,2] oxazolato ligands (ZnPBO-4) and its derivatives (ZnPBO-S) were synthesized, and luminescent properties of these materials were investigated. Both the fluorescent emission band and electroluminescent emission band were discussed based on their ligand structure differences. The emission band found that it strongly depends on the molecular structure of introduced ligand. It was tuned from 446 nm to 491 nm by changing the ligand structures. Spreading of the ${\pi}$-conjugation in 2-(o-hydroxyphenyl) group gives rise to a blue shift. The EL properties also showed good consistency with their differences of ligand structure. Bright-blue EL emission with a maximum luminance of 3,100 $cd/m^2$ at 12V, current density, 575 $mA/m^2$ was obtained from the organic light-emitting diodes (OLEDs) using ZnPBO-4 as emitting layer. It was also found that the newly synthesized materials were suitable to be used as emitting materials in organic EL device.