• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.381-388
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• 2015

Organic Light Emitting Diodes (OLEDs) have been receiving great attention in academic and industrial fields, and it is being actively applied to mobile display, as well as large area TV and next-generation flexible display due to their excellent advantages. In addition, the scope of research on OLED materials and device fabrication technology is getting expanded. This review discusses the principle and basic composition of OLED and also classifies OLED materials with different chemical structures according to their usages. Systematic classification of OLEDs by technical concept and material characteristics can help developing new emitting materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.9
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• pp.802-807
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• 2007

We have developed red phosphorescent top emission organic light-emitting diodes with transparent metal cathodes deposited by using thermal evaporation technique. Phosphorescent guest molecule, BtpIr(acac), was doped in host CBP for the red phosphorescent emission, Ca/Ag, Ba/Ag, and Mg/Ag double layers were used as cathode materials of top emission devices, which were composed of glass/Ni/2TNATA(15 nm)/${\alpha}$-NPD(35 nm)/CBP:BtpIr(acac)(40 nm, 10%)/BCP(5 nm)/$Alq_3$(5 nm)/cathodes. The optical transparencies of these metal cathodes strongly depend on underlying Ca, Ba, and Mg layers. These layers also strongly affect the electrical conduction and emission properties of the red phosphorescent top emission devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.67-68
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• 2008

A simple bi-layer structure of organic light emitting diode (OLED) was used to study the characteristics of anode preparation. Indium tin oxide (ITO) anode surface treatment of OLEDs was performed to get the optimum condition for the ITO anode. The ITO surface was treated by $O_2$ or $O_2$ / Ar mixed gas plasma with different processing time. The electrical characteristics of OLED were improved by plasma treatment. The operating voltage of OLED with $O_2$ or $O_2$/Ar mixed gas plasma treated anodes decreases from 8.2 to 3.4 V and 3.2V, respectively. The $O_2$ /Ar mixed gas plasma treatment results in better electrical property.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.435-438
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• 2008

We demonstrated the efficient blue organic light-emitting diodes (OLEDs) by employing diarylamino-fluorene derived blue fluorescent molecules as dopants. Among those, a device exhibited blue emission with the luminous efficiency of 11.2 cd/A at $20\;mA/cm^2$, the external quantum efficiency of 9.7% at $20\;mA/cm^2$, and the $CIE_{x,y}$ coordinates of (x=0.163, y=0.259) at 8V.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.147.2-147.2
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• 2014

Organic Light Emitting Diode (OLED)에 사용되는 유기재료 N,N.-diphenyl-N,N.-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine(NPB)의 상전이 특성을 여러 진공도에서 평가하였다. 압력, 온도제어가 가능한 진공시스템을 사용하여 여러 진공도에서 NPB의 상전이 온도를 측정하였고, 본 연구에 사용된 진공시스템의 신뢰성을 검증하기 위해 상압에서 측정한 NPB의 melting temperature를 Differential Scanning Calorimetry(DSC) data와 비교하였다. 또한 각 압력($10^{-7}{\sim}760Torr$)에서 측정한 상전이 온도를 바탕으로 최종 결과물인 NPB의 Phase diagram을 얻어냄으로써 일정 압력, 일정 온도에서의 NPB의 상거동을 예측할 수 있었다. 이러한 결과는 기존의 DSC열분석으로는 확인하기 어려웠던 진공에서의 유기재료의 상전이를 관측하였다는데 큰 의미가 있다. 향후, 이러한 방법을 활용한 진공에서의 유기재료의 상전이 특성 관측은 유기재료를 이용한 진공 증착공정방법의 최적화와, 다양한 유기재료의 열안정성 특성 파악에 도움이 될 것으로 기대가 된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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• pp.173-177
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• 2008

We have developed the transparent passivation layer for top emission organic light emitting diodes using CsCl thin film by the thermal evaporation method. The CsCl film was deposited on the Ca/Ag semitransparent cathode. The optical transmittance of Ca/ Ag/CsCl triple layer is higher than that of Ca/Ag double layer in the visible range. The device with a structure of glass/Ni/2-TNATA/a-NPD/Alq3:C545T/BCP/Alq3/Ca/Ag/CsCl results in higher efficiency than the device without CsCl passivation layer. The device without CsCl thin film shows a current efficiency of 7 cd/A, whereas the device passivated with CsCl layer shows an efficiency of 10 cd/A. This increase of efficiency isresulted from the increased optical extraction by the CsCl passivation layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.168-168
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• 2010

DCM derivatives were newly synthesized. The OLEDs with a DCM-A as an emitting layer was fabricated and analyzed their opto-electrical properties. The structures of OLEDs were I) ITO/DCM-A/Al, II) ITO/-NPD/DCM-A/LiF/Al, and III) ITO/-NPD/DCM-A/Alq3/LiF/Al. The EL peak of the DCM-A shows the red emission in the range of 700 nm. The structure I) shows that 1050 nW/cm2 at 510 mA/cm2. The structure II) shows that takes the most excellent luminance about 39,000 nW/cm2 at 290 mA/cm2. The EL structure ill shows luminance about 13,000 nW/cm2 at 6 mA/cm2.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.39-44
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• 2022

The light extraction technology for improving the light efficiency of OLEDs is the core technology for extracting the light inside the OLEDs to the outside. This study demonstrates a simple method to generate random nanostructures (RNSs) containing high refractive index nanoparticles to improve light extraction and viewing angle characteristics. A simple dry low-temperature process makes the nanostructured scattering layer on the polymer resin widely used in the industry. The scattering layer has the shape of randomly distributed nanorods. To control optical properties, we focused on changing the shape and density of RNSs and adjusting the concentration of high refractive index nanoparticles. As a result, the film of the present invention exhibits a perpendicular transmittance of 85% at a wavelength of 550 nm. This film was used as a scattering layer to reduce substrate mode loss and improve EL efficiency in OLEDs.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.181-181
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• 2013

Recently, nanostructure and the molecular orientation of organic thin films have been largely paid attention due to its importance in organic electronics such as organic thin film transistors (OTFTs), organic light emitting diodes (OLEDs), and organic photovoltaics (OPVs). Among various methods, the diffraction and scattering techniques based on synchrotron x-rays have shown powerful results in organic thin film systems. In this work, we introduce the in-situ annealing system installed at PLS-II (Pohang Light Source II) for organic thin films by simultaneously conducting various x-ray scattering measurements of x-ray reflectivity, conventional x-ray scattering, grazing incidence wide angle x-ray scattering (GI-WAXS) and so on. Using the in-situ measurement, we could obtain real time variation of nanostructure as well as molecular orientation during thermal annealing in metal-phthalocyanine thin films. The variation of surface and interface also could be simultaneously investigated by the x-ray reflectivity measurement.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1306-1309
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• 2005

Highly efficient and bright organic light-emitting diodes (OLEDs) have been realized using the thin alkali compound films (TACFs) at the interface between an emitting layer and an electron transporting layer with conventional organic layers. By comparing the performance of the device as a function of position with the TACFs, we propose the optimal position of the TACFs in the tris-(8-hydroxyquinoline) aluminum (Alq3). A device with the ACFs showed high luminance of over 12 500 cd/m2, luminance efficiency of more than 12 cd/A, and power efficiency of more 4.5 lm/W, respectively.