• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.255-259
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• 2024

In this study, an aqueous-based redox flow battery (RFB) was constructed using tungstosilic acid (TSA), which is a kind of polyoxometalate, as the negative electrode active material and iron chloride (FeCl3) as the positive electrode active material in a sulfuric acid (H₂SO₄) supporting electrolyte. As a result of the cell's performance, it exhibited capacity fading and low energy efficiency. To address these issues, malic acid (MA), an organic additive, was introduced to the positive electrode active material and then tested for electrochemical properties and single cell performance. The malic acid in the iron chloride aqueous solution is working as a chelate agent, and two carboxyl groups are effectively coordinated with iron ions. It was found that MA reduced the electrolyte resistance of the positive electrode active material, leading to chemical stabilization and an increase in capacity and energy efficiency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.10
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• pp.609-614
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• 2017

The proposed stretchable transparent electrodes based on silver nanowires (AgNWs) were prepared on a polyurethane (PU) substrate. In order toavoid the surface roughness caused by the silver nanowires, a titanium oxide ($TiO_2$) buffer layer was addedby coating and heating the organometallic sol-gel solution. The fabricated stretchable electrodes showedan electrical sheet resistance of $24{\Omega}sq^{-1}$, 78% transmittance at 550 nm, and an average surface roughness below 5 nm. Furthermore, the AgNW-based electrode maintained its initial electrical resistance under 130% strain testing conditions, without the assistance of additional conductive polymer layers. In this paper, the critical role of the $TiO_2$ buffer layer between the AgNW network and the PU substrate has been discussed.

• Transactions on Electrical and Electronic Materials
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• v.6 no.4
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• pp.154-158
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• 2005

Organic molecules have many properties that make them attractive for electronic applications. We have been examining the progress of memory cell by using molecular-scale switch to give an example of the application using both nano scale components and Si-technology. In this study, molecular electronic devices were fabricated with amino style derivatives as redox-active component. This molecule is amphiphilic to allow monolayer formation by the Langmuir-Blodgett (LB) method and then this LB monolayer is inserted between two metal electrodes. According to the current-voltage (I-V) characteristics, it was found that the devices show remarkable hysteresis behavior and can be used as memory devices at ambient conditions, when aluminum oxide layer was existed on bottom electrode. The diode-like characteristics were measured only, when Pt layer was existed as bottom electrode. It was also found that this metal layer interacts with organic molecules and acts as a protecting layer, when thin Ti layer was inserted between the organic molecular layer and Al top electrode. These electrical properties of the devices may be applicable to active components for the memory and/or logic gates in the future.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1183-1189
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• 2012

Organic light-emitting diodes (OLEDs) using microcavity effect have attracted great attention because they can reduce the width of emission spectra from organic materials, and enhance brightness from the same material. We demonstrate the simulation results of the radiation properties from top-emitting organic light-emitting diodes (TE-OLEDs) with microcavity structures based on the general electromagnetic theory. Organic materials such as N,N'-di (naphthalene-1-yl)-N,N'-diphenylbenzidine (NPB) as a hole transport layer and tris (8-hydroxyquinoline) ($Alq_3$) as emitting and electron transporting layer are used to form the OLEDs. The organic materials were sandwiched between anode such as Ni or Au and cathode such as Al, Ag, or Al:Ag. The devices were characterized with electroluminescence phenomenon. We confirmed that the simulation results are consistent with experimental results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.57-58
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• 2008

We have studied an organic layer and semitransparent Al electrode thickness dependent optical properties and microcavity effects for top-emission organic light-emitting diodes. Manufactured top-emission device structure is Al(100nm)/TPD(xnm)/Alq(ynm)/LiF(0.5nm)/Al(25nm). While a thickness of total organic layer was varied from 85nm to 165n, a ratio of those two layers was kept to be about 2:3. Semitransparent Al cathode was varied from 20nm to 30nm for the device with an organic layer total thickness of 140nm. As the thickness of total organic layer increases, the emission spectra show a shift of peak wavelength from 490nm to 580nm, and the full width at half maxima from 90nm to 35nm. The emission spectra show a blue shift as the view angle increases. Emission spectra depending on a transmittance of semitransparent cathode show a shift of peak wavelength from 515nm to 593nm. At this time, the full width at half maximum was about to be a constant of 50nm. With this kind of microcavity effect, we were able to control the emission spectra from the top-emission organic light-emitting diodes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.588-593
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• 2023

The advantage of OTFT technology is that large-area circuits can be manufactured on flexible substrates using a low-cost solution process such as inkjet printing. Compared to silicon-based inorganic semiconductor processes, the process temperature is lower and the process time is shorter, so it can be widely applied to fields that do not require high electron mobility. Materials that have utility as electrode materials include carbon that can be solution-processed, transparent carbon thin films, and metallic nanoparticles, etc. are being studied. Recently, a technology has been developed to facilitate charge injection by coating the surface of the Al electrode with solution-processable titanium oxide (TiOx), which can greatly improve the performance of OTFT. In order to commercialize OTFT technology, an appropriate method is to use a complementary circuit with excellent reliability and stability. For this, insulators and channel semiconductors using organic materials must have stability in the air. In this study, carbon-doped Mo (MoC) thin films were fabricated with different graphite target power densities via unbalanced magnetron sputtering (UBM). The influence of graphite target power density on the structural, surface area, physical, and electrical properties of MoC films was investigated. MoC thin films deposited by the unbalanced magnetron sputtering method exhibited a smooth and uniform surface. However, as the graphite target power density increased, the rms surface roughness of the MoC film increased, and the hardness and elastic modulus of the MoC thin film increased. Additionally, as the graphite target power density increased, the resistivity value of the MoC film increased. In the performance of an organic thin film transistor using a MoC gate electrode, the carrier mobility, threshold voltage, and drain current on/off ratio (I_on/I_off) showed 0.15 cm²/V·s, -5.6 V, and 7.5×10⁴, respectively.

• Current Applied Physics
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• v.18 no.12
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• pp.1592-1599
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• 2018

The present study deals with the effect of dual cathode buffer layer (CBL) on the performance of bilayer of 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC) and fullerene (C70)-based organic solar cell (OSC) with low donor concentration. OSC devices with CBLs have been fabricated using thermal vapor deposition technique. We report the use of lithium fluoride (LiF) and molybdenum trioxide ($MoO_3$) as CBLs. The insertion of LiF between C70 and aluminium (Al) electrode enhances the power conversion efficiency (PCE) of device from 1.89% to 2.47% but quenching of photogenerated excitons is observed at interface of C70 and LiF layers. Incorporation of $MoO_3$ between LiF and Al electrode further enhances PCE of device to 3.51%. This has also improved the material quality and device properties, by preventing the formation of gap states and diminishing exciton quenching.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.1
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• pp.23-26
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• 2017

Mo doped carbon (C:Mo) thin films were fabricated with various Mo target power densities by unbalanced magnetron sputtering (UBM). The effects of target power density on the surface, structural, and electrical properties of C:Mo films were investigated. UBM sputtered C:Mo thin films exhibited smooth and uniform surfaces. However, the rms surface roughness of C:Mo films were increased with the increase of target power density. Also, the resistivity value of C:Mo film as electrical properties was decreased with the increase of target power density. From the performance of organic thin filml transistor using conductive C:Mo gate electrode, the carrier mobility, threshold voltage, and on/off ratio of drain current (Ion/Ioff) showed $0.16cm^2/V{\cdot}s$, -6.0 V, and $7.7{\times}10^4$, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.889-892
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• 2009

We have developed a practical printing technology for the gate electrode of organic thin film transistors(OTFTs) by combining screen-printing with wet-etching process using nano-silver ink as a conducting material. The screen-printed and wet-etched Ag electrode exhibited a minimum line width of ~5 um, the thickness of ~65 nm, and a resistivity of ${\sim}10^{-6}{\Omega}{\cdot}cm$, producing good geometrical and electrical characteristics for gate electrode. The OTFTs with the screen-printed and wet-etched Ag electrode produced the saturation mobility of $0.13cm^2$/Vs and current on/off ratio of $1.79{\times}10^6$, being comparable to those of OTFT with the thermally evaporated Al gate electrode.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.230-230
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• 2012

Graphene have showed promising performance as electrodes of organic devices such as organic transistors, light-emitting diodes, and photovoltaic solar cells. In particular, among various organic materials of graphene-based organic devices, pentacene has been regarded as one of the promising organic material because of its high mobility, chemical stability. In the bottom-contact device configuration generally used as graphene based pentacene devices, the morphology of the organic semiconductors at the interface between a channel and electrode is crucial to efficient charge transport from the electrode to the channel. For the high quality morphology, understanding of initial stages of pentacene growth is essential. In this study, we investigate self-assembly of pentacene molecules on graphene formed on a 6H-SiC (0001) substrate by scanning tunneling microscopy. At sub-monolayer coverage, adsorption of pentacene molecules on epitaxial graphene is affected by $6{\times}6$ pattern originates from the underlying buffer layer. And the orientation of pentacene in the ordered structure is aligned with the zigzag direction of the edge structure of single layer graphene. As coverage increased, intermolecular interactions become stronger than molecule-substrate interaction. As a result, herringbone structures the consequence of higher intermolecular interaction are observed.