• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1133-1137
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• 2005

In this paper, a renovated approach in the fabrication of red organic light-emitting diodes (OLEDs) is described. The hard-to-control doping process required for dopant-based red OLEDs can be avoided due to the novel red fluorophores that are not concentration quenching in solid state. Doping is in general a must for phosphorescence OLEDs because of the triplet-triplet annihilation, a common problem for phosphorophore dopants. However, we have recently found that extraordinary red iridium complex showing relatively short emission lifetime render the non-doped phosphorescence red OLED possible.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.576-581
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• 2005

We fabricated red organic light emitting diodes(OLEDs) utilizing tis(8-hydroxyquinoline) aluminum $(Alq_3)$ doped with $5\%$ of (4-(dicyanomethylene)-2-i-propyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran) (DCJTI) and investigated the driving and modulation characteristics for applying to the electro-optical conversion device. To improve the driving characteristics of red OLEDs, 3 V of offset voltage, which is equal to the turn on voltage, Is applied to the device. Offset voltage enhanced the optical EL output and reduced the rise time of EL waveforms of red OLEDs, and hence the cutoff frequency is increased with increasing applied voltage. The optical pulse of 100 MHz has been obtained from red OLEDs. Therefore, we confirmed that the red OLEDs can be applied to the fields of optical communication as an electro-optical conversion device.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.612-615
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• 2004

We present an extremely high efficient red organic light-emitting diodes (OLEDs) using a fluorescent dye 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped into an emitting region which consists of multiple pairs of a doped and an undoped layer. An emitting region of OLEDs composes of a tris-(8-hydroxyquinolinato) aluminum (Alq3) codoped with rubrene of 5% wt. or a mixture of Alq3 and rubrene (1:1). The luminance yield of the codoped device and the mixed device are 6.5 cd/A and 9.2 cd/A at 10 mA/$cm^2$, respectively. We have considerably improved the luminance yields of red OLEDs as much as ${\sim}$90% at 10 mA/$cm^2$ compared with that of the device doped with only DCJTB. We attribute it to both the emitting assist dopant (rubrene) and the dotted-line doping structure in an emitting region of OLED.

• 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.19 no.5
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• pp.437-441
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• 2006

The red emitting OLEDs using $Alq_3$:Rubrene-GDI4234 phosphors have been fabricated and characterized . In the device fabrication, 2- TNATA [4,4',4' - tris (2- naphthylphenyl - phenylamino ) - tripheny lamine] as the hole injection material and NPB [N,N'-bis (1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] as the hole transport material were deposited on the ITO(indium tin oxide)/glass substrate by vacuum evaporation. And then, red color emissive layer was deposited using $Alq_3$ as the host material and Rubrene(5,6,11,12-tetraphenylnaphthacene)-GDI4234 as the dopants. finally, small molecule OLEDs with structure of ITO/2-TNATA/NPB/$Alq_3$:Rubrene-GDI4234/$Alq_3$/LiF/Al were obtained by in-situ deposition of $Alq_3$, LiF and Al as the electron transport material, electron injection material and cathode, respectively. Red OLEDs fabricated in our experiments showed the color coordinate of CIE(0.65, 0.35) and the maximum power efficiency of 2.1 lm/W at 7 V with the peak emission wavelength of 632 nm.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2787-2790
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• 2011

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.310-310
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• 2009

In the two structure of ITO/N,N'-diphenyl-N,N' bis (3-methylphenyl)-1,1'-biphenyl-4,4'-diamine(TPD)/R-H : R-D/Al device, ITO/Amorphous Fluoropolymers/TPD/R-H : R-D/LiF/Al device. we studied the effect of organic materials defending on the electrical characteristics of red OLEDs. The thickness of TPD and R-H : R-D was manufactured 40 nm, 60 nm, respectively under a base pressure of $5\times10^{-6}$Torr using a thermal evaporation. The AF used for an hole-injection is the thickness of 0.5 [nm] and the LiF used for an electron-injection is the thickness of 0.5 [nm]. Compared to the two from the devices made with the hole injection and without hole injection We found that the luminous efficiency and the external quantum efficiency are improved a fact of one- hundred, two, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.196-199
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• 2009

We report the multiple quantum well (MQW) structure for highly efficient red phosphorescent OLEDs. Various triplet quantum well devices from a single well to five quantum wells are realized using a wide band-gap hole and electron transporting layers, narrow band-gap host and dopant material, and charge control layers (CCL). The maximum external quantum efficiency of 14.8 % with a two quantum well device structure is obtained, which is the highest value among the red phosphorescent OLEDs using same dopant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.12a
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• pp.114-118
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• 2006

We investigated the transient electroluminescence (EL) and modulation characteristics of red organic light-emitting diodes (OLEDs), which consist with 4-(dicyanomethylene)-2-i -propyl-6-(1,1,7,7-tetramethyljulolidyl-9-cnyl)-4H-pyran (DCJTI) and rubrene doped into tris(8-hydroxyquinoline)aluminum ($Alq_3$). The transient EL waveforms showed two components, the overshooting peak and constant component, indicating that the excess amount of accumulated charges simultaneously recombine at the onset moment. This overshooting effect reduced the rise time of transient EL and enhanced the optical output of OLEDs when the pulse voltage applied to the device. We demonstrated that the red OLEDs could be use for the high-speed switching application by driving at more than 100 MHz and transmitting the video signals utilized as the electro-optical conversion device

• Journal of Information Display
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• v.10 no.2
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• pp.87-91
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• 2009

Highly efficient red phosphorescent OLEDs (PHOLEDs) with a simple, organic, triple-layer structure was developed using the narrow-bandgap fluorescent host material bis(10-hydroxybenzo[h] quinolinato)beryllium complex (Bebq2) and the deep-red dopant tris(1-phenylisoquinoline)iridium (Ir(piq)3). The maximum current and power efficiency values of 12.71 cd/A and 16.02 lm/W, respectively, with an extremely low doping technology of 1%, are demonstrated herein. The results reveal a practical, cost-saving host dopant system for the fabrication of highly efficient PHOLEDs involving the simple structure presented herein, with a reduction of expensive Ir dopants.