• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.781-785
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• 2009

We have fabricated simple triple-layer blue-emitting phosphorescent organic light emitting diodes (OLEDs) using different thicknesses (25 and 55 nm) of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) electron transport layers. 1,1-bis[4-bis (4-methylphenyl)- aminophenyllcyclohexane (TAPC), bis[(4,6-di-fluorophenyl)-pyridinate-$N,C^{2'}$]picolinate (FIrpic) and N,N' -dicarbazolyl-3,5-benzene (mCP) were used as hole transport, blue guest and host materials, respectively. The driving voltage, electroluminescence (EL) efficiency and emission characteristics of devices were investigated. The maximum EL efficiency was 20 cd/A in the device with 55 nm BCP layer, which efficiency was about 33% higher than the device with 25 nm BCP layer. The higher efficiency in the 55 nm BCP device resulted from the enhanced electron-hole balance. In the EL spectrum of blue phosphorescent OLED with BCP layer, the relative intensity between 470 and 500 nm peaks was related to the location of emission zone.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.863-868
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• 2009

New spiro[fluorene-7,9′-benzofluorene]-based blue host material, 5-phenyl-spiro[fluorene-7,9′-benzofluorene] (BH-1P), was successfully prepared by reacting 5-bromo-spiro[fluorene-7,9′-benzofluorene] (1) with phenyl boronic acid through the Suzuki reaction. 5-(N,N-Diphenyl)amino-spiro[fluorene-7,9′-benzofluorene] (BH-1DPA) and diphenyl-[4-(2-[1,1;4,1]terphenyl-4-yl-vinyl)-phenyl]amine (BD-1) were used as dopant materials. 2,5-Bis-(2',2"- bipyridin-6-yl)-1,1-diphenyl-3,4-diphenylsilacyclopentadiene (ET4) and Alq3 were used as electron transfer materials. Their UV absorption, photoluminescence and thermal properties were examined. The blue OLEDs with the configuration of ITO/DNTPD/$\alpha$-NPD/BH-1P:5% dopant/$Alq_3$ or ET4/LiF-Al prepared from the BH-1P host and BH-1DPA and BD-1 dopants showed a blue EL spectrum at 452 nm at 10 V and a luminance of 923.9 cd/$m^2$ with an efficiency of 1.27 lm/W at a current density of 72.57 mA/$cm^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.305-306
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• 2009

In this study, we have invastigated the recombination zone in the blue phosphorescent organic light-emitting devices with various partially doped structures. The basic device structure of the blue PHOLED was anode / hole injection layer (HIL) / hole transport layer (HTL) / emittingvastigated the recombination zone in the blue layer (EML) / hole blocking layer (HBL) / electron transport layer (ETL) / electron injection layer (EIL) / cathode. After the preparation of the blue PHOLED, the current density (J) - voltage (V) - luminance (L) and current efficiency characteristics were measured.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.493-496
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• 2009

We report the EL property of blue and blue-violet emitting materials with anthracene moiety as well as a new core structure containing indenopyrazine. Non-doped device using one of indenopyrazine core derivatives was found to exhibit excellent blue-violet color purity of (0.173, 0.063), and narrow emission band of 42nm FWHM. One of anthracene core derivatives with bulky side group also exhibits excellent color coordinates (0.156, 0.088) and an external quantum efficiency of 7.18%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.9
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• pp.581-586
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• 2015

We studied optical and electrical properties of two-wavelength white tandem organic light-emitting diodes using red and blue materials. White fluorescent OLEDs were fabricated using Alq3 : Rubrene (3 vol.% 5 nm) / SH-1 : BD-2 (3 vol.% 25 nm) as emitting layer (EML). White single fluorescent OLED showed maximum current efficiency of 9.7 cd/A, and tandem fluorescent OLED showed 18.2 cd/A. Commission Internationale de l'Eclairage (CIE) coordinates of single and tandem fluorescent OLEDs was (0.385, 0.435), (0.442, 0.473) at $1,000cd/m^2$, respectively. White hybrid OLEDs were fabricated using SH-1 : BD-2 (3 vol.% 10 nm) / CBP : $Ir(mphmq)_2(acac)$ (2 vol.% 20 nm) as EML. White single hybrid OLED showed maximum current efficiency of 7.8 cd/A, and tandem hybrid OLED showed 26.4 cd/A. Maximum current efficiency of tandem hybrid OLED was more twice as high as single OLED. CIE coordinates of single hybrid OLED was (0.315, 0.333), and tandem hybrid OLED was (0.448, 0.363) at $1,000cd/m^2$. CIE coordinates in white tandem OLEDs compared to those for single OLEDs observed red shift. This work reveals that stacked white OLED showed current efficiency improvement and red shifted emission than single OLED.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1046-1049
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• 2006

We proposed a simplified fabrication structure and method which can provide separate Red (R), Green (G), Blue (B), and White (W) OLED pixels with 2 metal-mask changes in emitting layer fabrication inspired from the structure of multi-layer white OLED and carrier blocking mechanism. A red emission layer for the R and W pixel with 1st mask, and then a blue emission layer with hole blocking layer for the B and W pixel with 2nd mask, and finally a common green emission layer were deposited sequentially. We expect that this concept would be very useful to the actual fabrication of multi-color OLED display although additional optimization is needed.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.787-790
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• 2009

High contrast red, green and blue organic light-emitting diodes were fabricated using inorganic metal multi layer composed of thin Al, KCl and thick Al and then were compared to optical and electrical characteristics with the attached polarizer and conventional OLEDs. Ambient light reflection of OLED using inorganic metal layer, polarizer and conventional metal layer were 29.2, 31.1 and 82.5% respectively. Optical characteristics of OLEDs using inorganic metal layer were max luminescence of 13040 cd/m2 and luminous efficiency of 2.12 cd/A at 8V whereas OLEDs using polarizer has 8456 cd/m2 and 1.43 cd/A at 8V each. OLEDs including inorganic metal multi layers show significant technical advantages in achieving high performance of OLED display with improved contrast ratio of 251:1, specifically in Red OLED.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.456-461
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• 2012

We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with red/blue, blue/red and red/blue/red emitting layer (EML) structures were fabricated using a host-dopant system. In case of white PHOLEDs with red/blue structure, the best efficiency was obtained at a structure of red (15 nm)/blue (15 nm). But the emission color was blue-shifted white. In case of white PHOLEDs with blue/red structure, the better color purity and efficiency were observed at a blue (29 nm)/red (1 nm) structure. For additional improvement of color purity in white PHOLEDs with blue (29 nm)/red (1 nm) EMLs, we fabricated white PHOLEDs with red (1 nm)/blue (28 nm)/red (1 nm) structure. The current efficiency, external quantum efficiency, and CIE (x, y) coordinate were 27.2 cd/A, 15.1%, and (0.382, 0.369) at 1,000 $cd/m^2$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.837-840
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• 2014

Novel materials of $Zn(HPB)_2$ and Ir-complexes were respectively synthesized as blue or red emitting material. White Organic Light Emitting Diodes (OLED) were fabricated by using $Zn(HPB)_2$ for a blue emitting layer, Ir-complexes for a red emitting layer and $Alq_3$ for a green emitting layer. White OLED was fabricated by using double emitting layers of $Zn(HPB)_2$ and $Alq_3:Ir$-complexes, and hole blocking layer of BCP. We also varied the thickness of BCP. When the thickness of BCP layer was 5 nm, white emission was achieved. We obtained a maximum luminance of $3,500cd/m^2$. The CIE coordinates was (0.375, 0.331). From this study, we could propose that the hybrid structure is efficient in lighting application of white OLED by improvement of color purity.

• Journal of the Korean Applied Science and Technology
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• v.34 no.1
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• pp.101-107
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• 2017

Anthracene has been a motive molecule for the blue-emitting materials in OLED. Since the blue emission needs big band gap between HOMO and LUMO, the blue-emitting materials are rare. In this paper, some anthracene derivatives containing simple aryl groups are synthesized and characterized. Regardless of the substituents the absorption and the emission bands are similar to each other and similar to the derivatives with the bulky silyl groups. The thermal and the CIE tests imply that among the tested 9-(2-naphthyl)-10-phenylanthracene is most promising for the diode. The material for the emission layer has to be investigated, which is simple to be prepared as well as good in the electrical and the thermal properties.