• Particle and aerosol research
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• v.9 no.2
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• pp.51-57
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• 2013

A graphene(GR)-$TiO_2$ composite was synthesized from colloidal mixture of graphene oxide(GO) nanosheets and $TiO_2$ nanoparticles by an aerosol assisted self-assembly. The morphology, specific surface area and pore size of asprepared GR-$TiO_2$ composite were characterized by FE-SEM, BET, and BJH respectively. The shape of GR-$TiO_2$ composite was spherical. The average particle size was 0.5-1 ${\mu}m$ in diameter and the pore diameter ranged 20-50 nm. Photovoltaic characteristics of a mixture of the GR-$TiO_2$ and $TiO_2$ nanoparticles were measured by a solar simulator under simulated solar light. The highest photoelectric conversion efficiency of the mixture photoanode was 5.1%, which was higher than that of $TiO_2$ photoanode.

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.595-600
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• 2020

The photovoltaic properties of perovskite solar cells (PSCs) with a carbon electrode fabricated using different annealing processes are investigated. Perovskite formation (50 ℃, 60 min) using a hot-plate and an oven is carried out on cells with a glass/fluorine doped TiO₂/TiO₂/ZrO₂/carbon structure, and the photovoltaic properties of the PSCs are analyzed using a solar simulator. The microstructures of the PSCs are characterized using an optical microscope, a field emission scanning electron microscope, and an electron probe micro-analyzer (EPMA). Photovoltaic analysis shows that the energy conversion efficiency of the samples fabricated using the hot-plate and the oven processes are 2.08% and 6.90%, respectively. Based on the microstructure of the samples and the results of the EPMA, perovskite is formed locally on the carbon electrode surface as the γ-butyrolactone (GBL) solvent evaporates and moves to the top of the carbon electrode due to heat from the bottom of the sample during the hot plate process. When the oven process is used, perovskite forms evenly inside the carbon electrode, as the GBL solvent evaporates extremely slowly because heat is supplied from all directions. The importance of the even formation of perovskite inside the carbon electrode is emphasized, and the feasibility of oven annealing is confirmed for PSCs with carbon electrodes.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.380-383
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• 2015

We prepared the $TiO_2$ layer with 0 ~ 4 wt% of polystyrene (PS) beads having a radius of 250 nm to increase the dye adsorption and energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC). Then, we fabricated DSSCs using $0.45cm^2$ active area. FE-SEM was used to characterize the microstructure consisting of $TiO_2$ layer and PS beads. UV-VIS-NIR was used to determine the optical absorbance of working electrodes (WEs). Solar simulator and potentiostat were used to determine the photovoltaic properties. We observed that pores having a radius of 250 nm were formed with the density of $0.15ea/{\mu}m^2$ in $TiO_2$ layers after conducting the sintering process. The absorbance in visible light regime was found to increase with the increase in the amount of PS beads. The ECE increased from 4.66% to 5.25% when the amount of PS beads was increased from 0 to 4 wt%. This is because the pores of PS beads increased the adsorption of dye. Our results indicate that the ECE of the DSSCs can be enhanced by the addition of an appropriate amount of PS beads into $TiO_2$ layers.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.384-388
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• 2015

We prepared blocking layers by adding 0.0 ~ 0.6 wt% nano diamond blends (DBs) to $TiO_2$ blocking layers to improve the energy conversion efficiencies (ECEs) of dye sensitized solar cells (DSSCs). TEM and micro-Raman spectroscopy were used to characterize the microstructure and phases of DBs, respectively. Optical microscopy and FE-SEM were used to analyze the microstructure of the $TiO_2$ blocking layer with DBs. UV-VIS-NIR spectroscopy was used to determine the absorbance of the working electrodes. A solar simulator and a potentiostat were used to determine the photovoltaic properties and the impedance of the DSSCs with DBs. From the results of the DBs analysis, we determined a 6.97 nm combination of nano diamonds and graphite. We confirmed that ECE increased from 5.64 to 6.48 % when the added DBs increased from 0.0 to 0.2 wt%. This indicates that the effective surface area and electron mobility increased when DBs were added to the $TiO_2$ blocking layer. Our results indicate that the ECE of DSSCs can be enhanced by adding an appropriate amount of DBs to the $TiO_2$ blocking layers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.461-462
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• 2005

In order to improve the efficiency of dye-sensitized solar cell (DSC), $TiO_2$ electrode screen-printed on transparent conducting oxide (TCO) substrate was sintered in variation with different temperature(350 to $550^{\circ}C$). $TiO_2$ electrode on fluorine doped tin oxide (FTO) glass was assembled with Pt counter electrode on FTO glass. I-V properties of DSC were measured under solar simulator. Also, effect of sintering temperature on surface morphology of $TiO_2$ films was investigated to understand correlation between its surface morphology and sintering temperature. Such surface morphology was observed by atomic force microscopy (AFM). From the measurement results, at sintering temperature of $500^{\circ}C$, both efficiency and fill factor of DSC were mutually complementary, enhancing highest fill factor and efficiency. Consequently, it was considered that optimum sintering temperature of $\alpha$-terpinol included $TiO_2$ paste is at $500^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.301-301
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• 2010

In order to enhance the efficiency of the organic solar cells, the effects of plasma surface treatment with using $CF_4$ and $O_2$ gas on the anode ITO were studied. The polymer solar cell devices were fabricated on ITO glasses an active layer of P3HT (poly-3-hexylthiophene) and PCBM ([6,6]-phenyl C61-butyric acid methyl ester) mixture, without anode buffer layer, such as PEDOT:PSS layer. The metallic electrode was formed by thermally evaporated Al. Before the coating of organic layers, ITO surface was exposed to plasma made of $CF_4$ and $O_2$ gas, with/without heat treatment. In order to identify the effect the surface treatment, the current density and voltage characteristics were measured by solar simulator and the chemical composition of plasma treated ITO surface was analyzed by using X-ray photoelectron spectroscopy(XPS). In addition, the work function of the plasma treated ITO surface was measured by using ultraviolet photoelectron spectroscopy(UPS). The effects of plasma surface treatment can be attributed to the removal organic contaminants of the ITO surface, to the improvement of contact between ITO and buffer layer, and to the increase of work function of the ITO.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.197.2-197.2
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• 2015

Low-cost, high efficiency solar cells are tremendous interests for the realization of a renewable and clean energy source. ZnTe based solar cells have a possibility of high efficiency with formation of an intermediated energy band structure by impurity doping. In this work, the ZnTe:O/CdS/ZnO structure was fabricated by pulsed laser deposition (PLD) technique. A pulsed (10 Hz) Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from an ablated a ZnTe target, whose density of laser energy was 4.5 J/cm2. The base pressure of the chamber was kept at a pressure of approximately $4{\times}10-7Torr$. ZnO thin film with thickness of 100 nm was grown on to ITO/glass, and then CdS and ZnTe:O thin film were grown on ZnO thin film. Thickness of CdS and ZnTe:O were 50 nm and 500 nm, respectively. During deposition of ZnTe:O films, O2 gas was introduced from 1 to 20 mTorr. For fabricating ZnTe:O/CdS/ZnO solar cells, Au metal was deposited on the ITO film and ZnTe:O by thermal evaporation method. From the fabricated ZnTe:O/CdS/ZnO solar cell, current-voltage characteristics was measured by using HP 4156-a semiconductor parameter analyzer. Finally, solar cell performance was measured using an Air Mass 1.5 Global (AM 1.5 G) solar simulator with an irradiation intensity of 100 mW cm-2.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.243.1-243.1
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• 2015

To replace the based on silicon solar cells, the third generation solar cells, Dye-sensitized solar cells (DSSCs), is low fabrication than silicon solar cells, environmentally friendly and can be applied to various field. For this reason, the DSSCs have been continuously researched. But DSSCs have one drawback that is the low power conversion efficiency (PCE) than silicon solar cells. To solve the problem, we used the backr-eflector the Al foil that can be easily obtained from the surrounding in order to improve the efficiency of the DSSCs. Easily detachable Al foil back-reflector increases the photocurrent by enhancing the harvesting light because the discarded light is reused. It also leads to enhance the power conversion efficiency (PCE). In addition, we compared with the efficiency of the DSSCs that is applied and does not be applied with back-reflector according to the thickness of the TiO2 photoelectrode. When the back-reflector is applied to DSSCs, the photocurrent is increased. It leads to affect the efficiency. We used to solar simulator and Electrochemical Impedance Spectroscopy (EIS) to confirm the PCE and resistance. The DSSCs were also measured by External Quantum effect (EQE). At the same time, FE-SEM and XRD were used to confirm the thickness of layer and crystal structural of photoelectrode.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.86.2-86.2
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• 2015

Cu2ZnSn(S,Se)4 thin film solar cells have been fabricated using sputtered Cu/Sn/Zn metallic precursors on Mo coated sodalime glass substrate without using a toxic H2Se and H2S atmosphere. Cu/Sn/Zn metallic precursors with various thicknesses were prepared using DC magnetron sputtering process at room temperature. As-deposited metallic precursors were sulfo-selenized inside a graphite box containing S and Se pellets using rapid thermal processing furnace at various sulfur to selenium (S/Se) compositional ratio. Thin film solar cells were fabricated after sulfo-selenization process using a 65 nm CdS buffer, a 40 nm intrinsic ZnO, a 400 nm Al doped ZnO, and Al/Ni top metal contact. Effects of sulfur to selenium (S/Se) compositional ratio on the microstructure, crystallinity, electrical properties, and cell efficiencies have been studied using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscope, I-V measurement system, solar simulator, quantum efficiency measurement system, and time resolved photoluminescence spectrometer. Our fabricated Cu2ZnSn(S,Se)4 thin film solar cell shows the best conversion efficiency of 9.24 % (Voc : 454.6 mV, Jsc : 32.14 mA/cm2, FF : 63.29 %, and active area : 0.433 cm2), which is the highest efficiency among Cu2ZnSn(S,Se)4 thin film solar cells prepared using sputter deposited metallic precursors and without using a toxic H2Se gas. Details about other experimental results will be discussed during the presentation.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1147-1154
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• 1999

We developed three-wavelength solar bank which is a very important part of the solar simulator with the commercial mercury lamps and projected halogen lamps. This was developed to satisfy simultaneously following three points: the ${\pm}10%$ uniformity of irradiance of the target area and irradiance in the each wave region and $1120W/m^2$ maximum irradiance of the solar in the summer. We used spectral radiance to determine the standard of the spectral irradiance and developed the perfect three-wavelength solar bank,considering of directionality, irradiance distance, interval both lamps, lamps combination and lamp numbers based on the measured spectral irradiance. To proof the capability of the three wavelength solar bank, We carefully analyzed color differences and heat transfer. As a result, we found that three wavelength solar bank was much better than commercial infrared lamp bank in terms of the color differences, heat transfer phenomena.