• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.197-200
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• 2014

We investigated the influence of blistering on $Al_2O_3$/SiON stacks and $Al_2O_3$/SiNx:H stacks passivation layers. $Al_2O_3$ film provides outstanding Si surface passivation quality. $Al_2O_3$ film as the rear passivation layer of a p-type Si solar cell is usually stacked with a capping layer, such as $SiO_2$, SiNx, and SiON films. These capping layers protect the thin $Al_2O_3$ layer from an Al electrode during the annealing process. We compared $Al_2O_3$/SiON stacks and $Al_2O_3$/SiNx:H stacks through surface morphology and minority carrier lifetime after annealing processes at $450^{\circ}C$ and $850^{\circ}C$. As a result, the $Al_2O_3$/SiON stacks were observed to produce less blister phenomenon than $Al_2O_3$/SiNx:H stacks. This can be explained by the differences in the H species content. In the process of depositing SiNx film, the rich H species in $NH_3$ source are diffused to the $Al_2O_3$ film. On the other hand, less hydrogen diffusion occurs in SiON film as it contains less H species than SiNx film. This blister phenomenon leads to an increase insurface defect density. Consequently, the $Al_2O_3$/SiON stacks had a higher minority carrier lifetime than the $Al_2O_3$/SiNx:H stacks.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.158-161
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• 2004

We have studied a lifetime in organic light-emitting diodes depending on buffer layer. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. And the cathode for electron injection was LiAl. Phthalocyanine Copper(CuPc), Poly(3,4-ethylenedioxythiophene):poly (PEDOT:PSS), or poly (9-vinylcarbazole)(PVK) material was used as a buffer layer. A thermal evaporation was performed to make a thickness of 40nm of TPD layer at a rate of $0.5{\sim}1\;{\AA}/s$ at a base pressure of $5{\times}10^{-6}\;torr$. A material of tris(8-hydroxyquinolinate) Aluminum($Alq_3$) was used as an electron transport and emissive layer. A thermal evaporation of $Alq_3$ was done at a deposition rate of $0.7{\sim}0.8[{\AA}/s]$ at a base pressure of $5{\times}10^{-6}\;torr$. By varying the buffer material, hole injection at the interface could be controlled because of the change in work function. Devices with CuPc and PEDOT:PSS buffer layer are superior to the other PVK buffer layer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.461-465
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• 2016

n-type silicon shows the better tolerance towards metal impurities with a higher minority carrier lifetime compared to p-type silicon substrate. Due to better lifetime stability as compared to p-type during illumination made the photovoltaic community to switch toward n-type wafers for high efficiency silicon solar cells. We fabricated the front electrode of the n-type solar cell with AgAl paste. The electrodes characteristics of the AgAl paste depend on the contact junction depth that is closely related to the firing temperature. Metal contact depth with p+ emitter, with optimized depth is important as it influence the resistance. In this study, we optimize the firing condition for the effective formation of the metal depth by varying the firing condition. The firing was carried out at temperatures below $670^{\circ}C$ with low contact depth and high contact resistance. It was noted that the contact resistance was reduced with the increase of firing temperature. The contact resistance of $5.99m{\Omega}cm^2$ was shown for the optimum firing temperature of $865^{\circ}C$. Over $900^{\circ}C$, contact junction is bonded to the Si through the emitter, resulting the contact resistance to shunt. we obtained photovoltaic parameter such as fill factor of 76.68%, short-circuit current of $40.2mA/cm^2$, open-circuit voltage of 620 mV and convert efficiency of 19.11%.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.12
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• pp.673-678
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• 2000

The dielectric barrier discharge(DBD) is a common method to create a nonthermal plasma in which electrical energy is used to create electrons with a high average kinetic energy. The unique aspect of dielectric barrier discharges is the large array of short lifetime(10ns) silent discharges created over the surface of the dielectric. A silent discharge is generated when the applied voltage exceeds the breakdown voltage of the carrier gas creating a conduction path between the applied electrode and grounded electrode. As charge accumulates on the dielectric, the electric field is reduced below the breakdown field of the carrier gas and the silent discharge self terminates preventing the DBD cell from producing a thermal arc. In fact, the most significant application of dielectric barrier discharges is to generate ozone for contaminated water treatment. Therefore, experiments were perfomed at 1∼2[bar] pressure using a coaxial geometry single dielectric barrier discharge for ozone concentrations and energy densities. The main result show that the concentration and efficiency of ozone are influenced by gas nature, gas quantity, gas pressure, supplied voltage and frequency.

• Korean Journal of Materials Research
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• v.30 no.8
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• pp.421-425
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• 2020

A transparent quantum dot (QD)-based light-emitting diode (LED) with silver nanowire (Ag NW) and indium-tin oxide (ITO) hybrid electrode is demonstrated. The device consists of an Ag NW-ITO hybrid cathode (-), zinc oxide, poly (9-vinylcarbazole) (PVK), CdSe/CdZnS QD, tungsten trioxide, and ITO anode (+). The device shows pure green-color emission peaking at 548 nm, with a narrow spectral half width of 43 nm. Devices with hybrid cathodes show better performances, including higher luminance with higher current density, and lower threshold voltage of 5 V, compared with the reference device with a pure Ag NW cathode. It is worth noting that our transparent device with hybrid cathode exhibits a lifetime 9,300 seconds longer than that of a device with Ag NW cathode. This is the reason that the ITO overlayer can protect against oxidization of Ag NW, and the Ag NW underlayer can reduce the junction resistance and spread the current efficiently. The hybrid cathode for our transparent QD LED can applicable to other quantum structure-based optical devices.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1774-1780
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• 2008

New PVC based polymeric membrane electrodes (PME) and coated glassy carbon electrodes (CGCE) based on synthesized Schiff base complexes of Co(III); [Co(Salen)$(PBu_3)_2$]$ClO_4$, [Co($Me_2$Salen)$(PBu_3)_2$]$ClO_4$, [Co(Salen)$(PBu_3)H_2O$]$ClO_4$; as anion carriers for potentiometric determination of $ClO_4\;^-$were studied. The PME and also CGCE electrodes prepared with [Co(Me2Salen)$(PBu_3)_2$]$ClO_4$ showed excellent response characteristics to perchlorate ions. The electrodes exhibited Nernstian responses to $ClO_4\;^-$ ions over a wide concentration range with low detection limits ($1.0 {\times} 10^{-6}\;mol\;L^{-1}$ for PME and $9.0 {\times} 10^{-7}\;mol\;L^{-1}$ for CGCE). The electrodes possess fast response time, satisfactory reproducibility, appropriate lifetime and, most importantly, good selectivity toward $ClO_4\;^-$ relative to a variety of other common inorganic anions. The potentiometric response of the electrodes is independent of the pH in the pH range 2.5-8.5. The proposed sensors were used in potentiometric determination of perchlorate ions in mineral water and urine samples. The interaction of the ionophore with perchlorate ions was shown by UV/Vis spectroscopy.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.1
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• pp.43-53
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• 2023

Sulfide concentrations critically affect worker safety and the integrities of underground facilities, such as deep geological repositories for spent nuclear fuel. Sulfide is highly sensitive to oxygen, which can oxidize sulfide to sulfate. This can hinder precise measurement of the sulfide concentration. Hence, a literature review was conducted, which revealed that two methods are commonly used: the methylene blue and sulfide ion-selective electrode (ISE) methods. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used for comparison with the two methods. The sulfide ISE method was found to be superior as it yielded results with a higher degree of accuracy and involved fewer procedures for quantification of the sulfide concentration in solution. ICP-OES results can be distorted significantly when sulfide is present in solution owing to the formation of H₂S gas in the ICP-OES nebulizer. Therefore, the ICP-OES must be used with caution when quantifying underground water to prevent any distortion in the measured results. The results also suggest important measures to avoid problems when using ICP-OES for site selection. Furthermore, the sulfide ISE method is useful in determining sulfide concentrations in the field to predict the lifetime of disposal canisters of spent nuclear fuel in deep geological repositories and other industries.

• Journal of the Korean Electrochemical Society
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• v.4 no.3
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• pp.125-131
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• 2001

A long-term variation of electrode polarization in the MCFC has been analyzed successfully using a single cell with a Au, $CO_2/O_2$ reference electrode Four different cells with different components were operated and their electrode polarizations were analyzed. As published in the literatures, the cathode polarization was larger than that of the anode. The more stable operation of a single cell with the Al-coated cell frame up to 6,000hrs indicates that the corrosion at the cell frame, particularly wet seal area, plays an important role to determine the lifetime of a MCFC. At the initial stage of the cell operation, the voltage of the cell using a cathode stabilized by the $LiCoO_2$ coating was relatively low due to the high cathode polarization. As the cell was operated and the stabilized cathode was lithiated sufficiently, the cathode polarization decreased and the cell voltage was recovered. It was observed that the voltage of the cell using the $Li_2CO_3/Na_2CO_3$ electrolyte fluctuated with operation time and the cathode polarization fluctuated along with the cell voltage quite similarly. Although the mechanisms of the voltage fluctuation were not clear yet, the results imply that the voltage fluctuation was related with a reaction in the cathode side. After testing every single cell, the cathode polarization increased with the steep decrease in the cell voltage. Thus, the cathode should be improved in order to develop more durable MCFC.

• Journal of the Korean Chemical Society
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• v.41 no.12
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• pp.653-660
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• 1997

Silicone rubber-matrix membranes doped with tetradecyltrimethylammonium chloride (TDTMACl) are used to enhance electrode performance for chloride measurements in physiological samples. The optimized membrane formulation incorporates 95.4 wt% silicone rubber and 4.6 wt% TDTMACl, and its pH response is negligible in the range of pH 6-10. The TDTMACl-doped silicone rubber membrane exhibits sub-Nernstian response to chloride from 10 to 300 mM (-37.5 mV/decade), but its selectivities for chloride over other anions are remarkably enhanced: KpotCl,NO3=1.3, KpotCl,I=2.0, KpotCl,Sal=0.8, KpotCl,SCN=2.0 and KpotCl,ClO4=0.8. Furthermore, since the silicone rubber-matrix membrane exhibits better adhesion to the solid surface than do PVC membranes, the lifetime of the coated-wire type membrane electrode is greatly improved. The response properties toward chloride and salicylate for solid-state sensor are not significantly changed after at least 35 days of use.

• Journal of Information Display
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• v.10 no.3
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• pp.111-116
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• 2009

In this paper, a plasma-assisted patterning method for the organic layers of organic light-emitting diodes (OLEDs) and its effect on the OLED performances are reported. Oxygen plasma was used to etch the organic layers, using the top electrode consisting of lithium fluoride and aluminum as an etching mask. Although the current flow at low voltages increased for the etched OLEDs, there was no significant degradation of the OLED efficiency and lifetime in comparison with the conventional OLEDs. Therefore, this method can be used to reduce the ohmic voltage drop along the common top electrodes by connecting the top electrode with highly conductive bus lines after the common organic layers on the bus lines are etched by plasma. To further analyze the current increase at low voltages, the plasma patterning effect on the OLED performance was investigated by changing the device sizes, especially in one direction, and by changing the etching depth in the vertical direction of the device. It was found that the current flow increase at low voltages was not proportional to the device sizes, indicating that the current flow increase does not come from the leakage current along the etched sides. In the etching depth experiment, the current flow at low voltages did not increase when the etching process was stopped in the middle of the hole transport layer. This means that the current flow increase at low voltages is closely related to the modification of the hole injection layer, and thus, to the modification of the interface between the hole injection layer and the bottom electrode.