• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.81-82
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• 2006

Doping is a well-known method for improving electroluminescent (EL) efficiency of organic light emitting diodes. In our study, doping with 2 materials simultaneously, we could achieve improved EL efficiency. The emission layer was tris-(8-hydroxyquinoline)aluminum, and the 2 dopants were N,N'-dimethyl-quinacridone (DMQA) and 10-(2-Benzothiazolyl)-2, 3, 6, 7-tetrahydro-1,1,7,7,-tetramethyl 1-1H, 5H, 11H-[1] benzopyrano [6,7,8-ij]quinolizin-11-one (C-545T). The EL intensity of co-doped device was nearly flat, it shows that co-doping technique could be a effective way to improve the EL efficiency. EL efficiency of Single-doped device based on DMQA and C-S45T were ~6.47Cd/A and ~7.45Cd/A, respectively. Co-doped device showed higher EL efficiency of ~8.30Cd/A.

• Journal of the Korean Applied Science and Technology
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• v.16 no.4
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• pp.323-327
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• 1999

A water-soluble conducting polymer (CPP400 Paste) containing a derivative of polythiophene with several dopant was investigated as an anode material for organic electroluminescent devices. The device of ITO/CPP 400 Paste/TPD/$Alq_3$/Li:Al was fabricated, where CPP 400 Paste films were prepared by spin coating and TPD and $Alq_3$, films were prepared by vacuum evaporation. It was found that the turn-on voltage, current density, and luminance of the devices were dependent upon the thickness of CPP 400 Paste film in the Electroluminescent and current-voltage characteristics of the devices. This phenomena were explained by the energy level diagram of the device with the energy levels of the CPP400 Paste obtained by cyclic voltammetric method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.40-46
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• 2019

To study the frequency response characteristics of alternating-current-driven organic light-emitting diodes (OLEDs), we fabricated blue-fluorescent OLEDs and analyzed their electroluminescent characteristics according to the alternating current voltage and frequency. The luminance-frequency characteristics of alternating-current-driven OLED was similar to that of a low-pass filter, and the luminance of high-voltage OLED decreased at higher frequency than low-voltage OLED. The luminance characteristics of the OLED according to the frequency is due to the capacitive reactance in the OLED, generated during the alternating current driving. The frequency response characteristics of the OLED according to the voltage is due to the decrease in internal resistance of the organic layer. In addition, the negative voltage component of the alternating current did not affect the frequency response of the OLED. Therefore, the electroluminescent characteristics of OLED with an alternating current power of 60 Hz are not influenced by the frequency.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.1
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• pp.1-6
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• 2000

In this paper, organic dispersion type back light EL(Electroluminescent) devices were manufactured using Ethyl hydroxy ethyl cellulose as organic binder, ZnS:Cu as phosphor powder and $BaTiO_3$ as dielectrics by screen printing method, which are focused on as a new light source. The properties of the fabricated organic dispersion type back light EL devices were showed $1.98[mA/\m^2]$ of current density, 0.075[W] of power consumption, 7.1[nF] of capacitance at $25[^{\circ}C]$, 100[V], 400[Hz], respectively. Also brightness of the fabricated device was revealed $20~110[cd/\m^2]$ at 50~150[V] and the change of color was shoed bluish green of x=0.1711, y=0.3676 which are color coordinate by CIE.

• Polymer(Korea)
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• v.24 no.1
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• pp.90-96
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• 2000

Organic electroluminescent (EL) device was fabricated with Alq$_3$ as an emitting material and PDPMA ultra thin film prepared by Langmuir-Boldgett technique as a polymer hole transport layer. A stable condensed PDPMA monolayer was obtained using arachidic acid as a surface active material. The thickness and absorbance of PDPMA LB film increased line-arly with the layer numbers. The organic multilayered device consisted of ITO/PDPMA LB film (19 layers)/Alq$_3$/Al emitted green light with brightness of 2500 cd/m$^2$ at a DC 14 V Especially, the drive voltage of EL device having PDPMA LB film of 15 layers exhibited the value as low as 4 V. The effects of thickness control and molecular orientation in the PDPMA LB film on EL performance were discussed.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.205-206
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• 2000

The capacitance-temperature (C-T) measurement technique is proposed in the present work to investigate the thermal stability of organic and polymeric thin films for organic electroluminescent display (OELD). The single layer devices with the individual materials were subjected to the C-T measurement, prior to the examination of the complete OELD. The single layer devices with the small molecules destroyed below $180\;^{\circ}C$ depending on the kinds of materials. However, the device with the hole-transporting polyimide did not show any relaxation up to $200\;^{\circ}C$. The small molecule based OELDs failed to emit light after annealing, whereas that with the hole-transporting polyimide worked well in spite of large reduction in intensity.

• Journal of the Korean Applied Science and Technology
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• v.15 no.3
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• pp.85-90
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• 1998

In this study, organic electroluminescent devices(OELD) with a structure of a glass $substrate/ITO/TPD/Tb(ACAC)_3(Phen-Cl)/Alq_3/Al$ was fabricated by vacuum evaporation method, where Tb complex was known to have green light emitting property. Electroluminescent(EL) and I-V characteristics of this structure were investigated. This triple-layer structure shows the green EL spectrum at the wavelwngth of 546nm, which is almost the same as the PL spectrum of $Pb(ACAC)_3(Phen_Cl)$. It was found in current-voltage(I-V) characteristics of the devices that the operating voltage was about 12V.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.914-916
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• 2003

Novel red organic electroluminescent (EL) dye, RED was developed for an application to the emission layer of EL device. Well known red material DCJTB was also used for comparison. Two kinds of devices were fablicated; one is ITO/ CuPc / TPD / 0.5% RED-1 in Alq3/ Alq3/ Li20/ Al and the other is ITO/ CuPc /TPD / 0.5% DCJTB in Alq3/Alq3/ Li20 / Al. External quantum efficiency of the EL device with RED was two times higher than that of the device with DCJTB. The maximum EL peak was detected at 635nm in the RED EL device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.253-257
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• 1998

Organic-based electroluminescent devices have attracted lots of interests because of their possible application as large-area flat pan디 display. In this study, current-voltage (I-V) characteristics of MEH-PPV thin films was investigated using various metal as a top electrode, where MEH-PPV thin films were prepared on 170 substrate by spin coating method and various metal such as Al, Ag, In, MgIn was deposited on MEH-PPV thin films as a top electrode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.609-612
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• 1999

Organic electroluminescent(EL) devices have received a great deal of attention due to their potential application as full-color displays. They are attractive because of their capability of multicolor emission, ease of fabrication, and operation at a low driving voltage. In this study, single and multiple quantum-well structures consisting of Eu(TTA)$_3$(bpy) complex well layer sandwiched between triphenyldiamine derivative (TPD) layers were fabricated and their photoluminescent electroluminescent characteristics were also investigated. Sharp emission at 616 nm has been observed from the Eu complex in multilayer, single and multiple quantum-well structures. Details on the explanation of electrical properties of these structures will be discussed.