• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.147-147
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• 2015

The multilayer structure of the organic light emitting diode has merits of improving interfacial characteristics and helping carriers inject into emission layer and transport easier. There are many reports to control hole injection from anode electrode by using transition metal oxide as an anode buffer layer, such as V2O5, MoO3, NiO, and Fe3O4. In this study, we apply thin films of LiF which is usually inserted as a thin buffer layer between electron transport layer(ETL) and cathode, as an anode buffer layer to reduce the hole injection barrier height from ITO. The thickness of LiF as an anode buffer layer is tested from 0 nm to 1.0 nm. As shown in the figure 1 and 2, the luminous efficiency versus current density is improved by LiF anode buffer layer, and the threshold voltage is reduced when LiF buffer layer is increased up to 0.6 nm then the device does not work when LiF thickness is close to 1.0 nm As a result, we can confirm that the thin layer of LiF, about 0.6 nm, as an anode buffer reduces the hole injection barrier height from ITO, and this results the improved luminous efficiency. This study shows that LiF can be used as an anode buffer layer for improved hole injection as well as cathode buffer layer.

• Journal of Korean Vacuum Science & Technology
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• v.6 no.3
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• pp.126-132
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• 2002

The origin of image-sticking in metal-insulator-metal type thin-film diode liquid crystal displays(TFD-LCDs) is the asymmetric current-voltage(I-V) characteristic of TFD element. We developed that TFD-LCDs have reduced-image-sticking. Tantalum pentoxide(Ta$_2$O$\sub$5/) is a candidate for use in metal-insulator-metal(MIM) capacitors in switching devices for active-matrix liquid crystal displays(AM-LCDs). High quality Ta$_2$O$\sub$5/ thin films have been obtained from anodizing method. We fabricated a TFD element using Ta$_2$O$\sub$5/ films which had perfect current-voltage symmetry characteristics. We applied novel process technologies which were postannealed whole TFD element instead of conventional annealing to the fabrication. One-Time Post-Annealing(OPTA) heat treatment process was introduced to reduce the asymmetry and shift of the I-V characteristics, respectively. OPTA means that the whole layers of lower metal, insulator, and upper metal are annealed at one time. Futhermore, in this paper, we discussed the effects of top-electrode metals and annealing conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1066-1074
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• 2004

With a diode corona charger, which is a component of ELPI(Electrical Low Pressure Impactor), aerosol particles are charged to make electrical detection possible before they are collected by the impactor. We designed and evaluated two cylindrical corona chargers, each of which had a central corona needle electrode. For the performance evaluation of each corona charger the polydisperse dioctyl sebacate(DOS) particles, with diameters of 0.1∼0.8 $\mu$m and NaCl particles, smaller than 0.1$\mu$m, were used. The particles were then led through an electrostatic classifier (TSI model 3081) to classify monodisperse aerosol with minimal size deviation. After evaluating the wall loss of the particles in the corona charger, we measured the product of penetration and number of charges, Pㆍn, to evaluate the corona charger efficiency at high positive voltages of 4, 5, 6 kV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.58-59
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• 2006

Top emission OLED 소자에 사용되는 ITO(Indium-Tin-Oxide)의 저항을 개선하여 보다 낮은 저항을 가지는 전극을 제작하기 위해 AZO(ZnO-Ag-ZnO)를 제작하였다. AZO박막은 기존의 ITO 박막이 수십 $\Omega$을 나타내던 것과 비교하여 $8{\Omega}$으로 매우 낮은 저항을 나타내었다. 투과율은 84%로 기존의 ITO 박막과 유사한 성능을 나타내었다.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.4
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• pp.35-38
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• 2003

Polymer light emitting diode (PLED) with an ITO/MEH-PPV/Al structure were prepared by spin coating method on the ITO (indium tin oxide)/glass substrates, using poly(2-methoxy-5-(2-ethylhexoxy)-1,4-phenylenevinylene (MEH-PPV) as the light emitting material. The dependence of heat treatment on the electrical and optical properties for the prepared PLED samples were investigated. The luminance decreased greatly from 630 cd/$\m^2$ to 280 cd/$\m^2$ at 10V input voltage as the heating temperature increased from $65^{\circ}C$ to $170^{\circ}C$. In addition, the luminance efficiency was found to be about 2 lm/W for the sample heat treated at $65^{\circ}C$. These results may be related to the interface roughness and/or the formation of an insulation layer, which is caused by the reaction between electrode and MEH-PPV organic luminescent film layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.148-148
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• 2015

Over the past several years, Colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been developed for the future of optoelectronic applications. An inverted-type quantum-dot light-emitting-diode (QDLED), employing low work function organic material polyethylenimine ethoxylated(PEIE) (<10 nm)[1] modified ZnO nanoparticles (NPs) as electron injection and transport layer, was fabricated by all solution processing method, instead of electrode in the device. The PEIE surface modifier incorporated on the top of the ZnO NPs film, facilitates the enhancement of both electorn injection into the CdSe-ZnS QD emissive layer by lowering the workfunction of ZnO from 3.58eV to 2.87eV and charge balance on the QD emitter. In this inverted QDLEDs, blend of poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo) and poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] are used as hole transporting layer (HTL) to improve hole transporting property. At the operating voltage of 7.5 V, the QDLED device emitted spectrally orange color lights with high luminance up to 11110 cd/m2, and showed current efficiency of 2.27 cd/A.[2]

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.377-380
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• 2012

Laser direct patterning of indium tin oxide(ITO) is one of new methods of direct etching process to replace the conventional photolithography. A diode pumped Q-switched Nd:$YVO_4$ (${\lambda}$= 1,064 nm) laser was used to produce ITO electrode on various transparent oxide semiconductor films such as zinc oxide(ZnO). The laser direct etched ITO patterns on ZnO were compared with those on glass substrate and were considered in terms of the overlapping rate of laser beam. In case of the laser etching on double-layer, it was possible to obtain the higher overlapping rate of laser beam.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.235-241
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• 2005

Incorporation of solid electrodes frequently involves plasma-based processing. The effect of plasma can influence the physical characteristics, depending on the magnitude in plasma. The undesired feature of plasma-induced damage should be prevented in characterizing the ultra-thin materials, such as ultra-thin films and organic monolayers. The current work at first proves the applicability of a liquid phase electrode in the electrical/dielectric properties through comparative work using Al and Hg on ultrathin $Al_2O_3$ films deposited through atomic layer deposition at low temperature: Two types of metals such as Aluminum (Al) and mercury (Hg) were used as electrodes in $Al_2O_3$ thin films in order to investigate the effect of electrode preparation on the current-voltage characteristics and impedance features as a function of thickness in $Al_2O_3$ film thickness. The success of Hg in $Al_2O_3$ thin films is applied to the AC and DC characterization of the organic monolayers obtained using the Langmuir-Blodgett method. From the DC current-voltage characteristics, the diode-like response is found to originate from the bulk response of the organic materials, evidenced by the fact and the capacitance is inversely related to the absolute thickness of organic layers.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.100-106
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• 2009

A novel 8 V DC power source with an external series-parallel connection of 50 Dye-sensitized Solar Cells (DSCs) has been proposed. One DSC has the optimized length to width ratio of $5.2{\times}2.6\;cm$ and an active area $8\;cm^2$ ($4.62{\times}1.73\;cm$) which attained a conversion efficiency of 4.02%. From the electrochemical impedance spectroscopic analysis, it was found that the resistance elements related to the Pt electrode and electrolyte interface behave like that of diode and the series resistance corresponds to the sum of the other resistance elements. Surface morphology and sheet resistance of Pt counter electrode did not degrade the performance of the cell. This novel 8V-0.33A DC power source shows stable performance with an energy conversion efficiency of 4.24% under 1 sun illumination (AM 1.5, Pin of $100\;mW/cm^2$).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.563-567
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• 2006

Indium tin oxide (ITO) used as an electrode in organic light emitting diodes (OLEDs) and organic thin film transistors (OTFTs) was modified by a self-assembled monolayer (SAM). For device fabrication, surface of the ITO was modified by immersion in a solution including various phosphonic acid at room temperature in order to increase work function of an electrode. The work function of ITO with SAM was measured by Kelvin probe. Work function increase of 0.88 eV was observed in ITO with various SAM. Therefore, ohmic contact is achieved in an interface between ITO and organic semiconductors (pentacene). We analyzed the origin of work function increase of ITO with SAM by X-ray photoelectron spectroscopy. We confirmed that increase of oxygen bonding energy attributed to increase the work function of ITO. These results suggested that ITO with the SAM gives a high possibility for high performance of OLEDS and OTFTs.