• 한국분말재료학회지
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• 제25권1호
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• pp.1-6
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• 2018

Uniform $TiO_2$ blocking layers (BLs) are fabricated using ultrasonic spray pyrolysis deposition (USPD) method. To improve the photovoltaic performance of dye-sensitized solar cells (DSSCs), the BL thickness is controlled by using USPD times of 0, 20, 60, and 100 min, creating $TiO_2$ BLs of 0, 40, 70, and 100 nm, respectively, in average thickness on fluorine-doped tin oxide (FTO) glass. Compared to the other samples, the DSSC containing the uniform $TiO_2$ BL of 70 nm in thickness shows a superior power conversion efficiency of $7.58{\pm}0.20%$ because of the suppression of electron recombination by the effect of the optimized thickness. The performance improvement is mainly attributed to the increased open-circuit voltage ($0.77{\pm}0.02V$) achieved by the increased Fermi energy levels of the working electrodes and the improved short-circuit current density ($15.67{\pm}0.43mA/cm^2$) by efficient electron transfer pathways. Therefore, optimized $TiO_2$ BLs fabricated by USPD may allow performance improvements in DSSCs.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3629-3633
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• 2011

The effect of a dense $TiO_2$ blocking layer prepared using the sol-gel method on the performance of dye-sensitized solar cells was studied. The blocking layer formed directly on the working electrode, separated it from the electrolyte, and prevented the back transfer of electrons from the electrode to the electrolyte. The dyesensitized solar cells were prepared with a working electrode of fluorine-doped tin oxide glass coated with a blocking layer of dense $TiO_2$, a dye-attached mesoporous $TiO_2$ film, and a nano-gel electrolyte, and a counter electrode of Pt-deposited FTO glass. The gel processing conditions and heat treatment temperature for blocking layer formation affected the morphology and performance of the cells, and their optimal values were determined. The introduction of the blocking layer increased the conversion efficiency of the cell by 7.37% for the cell without a blocking layer to 8.55% for the cell with a dense $TiO_2$ blocking layer, under standard illumination conditions. The short-circuit current density ($J_{sc}$) and open-circuit voltage ($V_{oc}$) also were increased by the addition of a dense $TiO_2$ blocking layer.

• Corrosion Science and Technology
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• 제11권2호
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• pp.65-69
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• 2012

One dimensional(1D) $Na_2Ti_6O_{13}$ nanorods with 70 nm in diameter was synthesized by a molten salt method. Using the synthesized nanorods, about 750 nm thick $Na_2Ti_6O_{13}$ film was coated on Fluorine-doped tin oxide(FTO) glasss substrate by the Layer-by-layer self-assembly(LBL-SA) method in which a repetitive self-assembling of ions containing an opposite electric charge in an aqueous solution was utilized. Using the Kubelka-Munk function, the band gap energy of the 1D-$Na_2Ti_6O_{13}$ nanorods was nalyzed to be 3.5 eV. On the other hand, the band gap energy of the $Na_2Ti_6O_{13}$ film coated on FTO was found to be a reduced value of 2.9 eV, resulting from the nano-scale and high porosity of the film processed by LBL-SA method, which was favorable for the photo absorption capability. A significant improvement of photocurrent and onset voltage was observed with the $Na_2Ti_6O_{13}$ film incorporated into the conventional $Fe_2O_3$ photoelectrode: the photocurrent increased from 0.25 to 0.82 mA/$cm^2$, the onset voltage decreased from 0.95 to 0.78 V.

• 한국세라믹학회지
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• 제52권2호
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• pp.103-107
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• 2015

The effective glass frit composition used to absorb laser energy and to seal commercial dye-sensitized solar cell panel substrates has been previously developed using $V_2O_5-TeO_2$-based glass with 10 wt% ${\beta}$-eucryptite as a CTE controlling filler. The optimum sealing conditions are provided using a 3 mm beam, a laser power of 40 watt, a scan speed of 300 mm/s, and 200 irradiation cycles. In this study, the feasibility of the developed glass frit is investigated in terms of the sealing strength and chemical durability against the commercial iodide/triiodide electrolyte solution and fluorine-doped tin oxide (FTO) electrode in order to increase the solar cell lifetime. The sealing strength of the laser-sealed $V_2O_5-TeO_2$-based glass frit is $20.5{\pm}1.7MPa$, which is higher than those of thermally sealed glass frit and other reported glass frit. Furthermore, the developed glass frit is chemically stable against electrolyte solutions. The glass frit constituents are not leached out from the glass after soaking in the electrolyte solution for up to three months. During the laser sealing, the glass frit does not react with the FTO electrode; thus, the resistivity of the FTO electrode beneath the laser-sealed area remains the same.

• 전기학회논문지
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• 제62권2호
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• pp.208-212
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• 2013

Dye-sensitized solar cells (DSCs) have taken much attention due to their low cost and easy fabrication method compare to silicon solar cells. But research on cost effective DSC is prerequisite for commercialization. Fluorine doped tin oxide (FTO) which have been commonly used for electrode substrate as electron collector occupied most percentage of manufacturing cost. Therefore we studied FTO-less DSC using sputtered Ti deposited glass as photoelectrode instead of FTO to reduce manufacturing cost. Ti films sputtered on the glass for different time, 5 to 20 minutes with decreasing sheet resistance as deposition time increases. A light source illuminated to counter electrode in order to overcome opaque Ti films. The efficiency of DSC (Ti20) made Ti sputtered glass for 20 min as photoelectrode was 5.87%. There are no significant difference with conventional cell despite lower manufacturing cost.

• 한국표면공학회지
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• 제40권4호
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• pp.190-196
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• 2007

Dye sensitized solar cells(DSSC) are the most promising future energy resource due to their high energy efficiency, low production cost, and simple manufacturing process. But one problem in DSSC is short life time compared to silicon solar cells. This problem occurred from photocatalytic degradation of dye material by nanometer sized $TiO_2$ particles. To prevent dye degradation as well as to increase its life time, the transparent coating film is needed for UV blocking. In this study, we synthesized nanometer sized $TiO_2$ particles in sols by increasing its internal pressure up to 200 bar in autoclave at $120^{\circ}C$ for 10 hrs. The synthesized $TiO_2$ sols were all formed with brookite phase and their particle size was several nm to 30 nm. Synthesized $TiO_2$ sols were coated on the backside of fluorine doped tin oxide(FTO) glass by ink jet printing method. With increasing coating thickness by repeated ink jet coating, the absorbance of UV region (under 400 nm) also increases reasonably. Decomposition test of titania powders dispersed in 0.1 mM amaranth solution covered with $TiO_2$ coating glass shows more stable dye properties under UV irradiation, compared to that with as-received FTO glass.

• 공업화학
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• 제22권1호
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• pp.98-103
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• 2011

DSSC의 광전 효율 증대와 Pt 상대전극의 접착성 향상을 위하여 FTO (Fluorine-doped Tin Oxide) 유리면에 Ni underlayer를 전기 도금 후 Pt 층을 전기 도금하였다. Ni underlayer는 $10mA/cm^2$에서 2 min 동안 도금한 경우 Ni 층과 FTO 면사이의 접착성이 가장 우수하게 나타났으며, Ni underlayer를 $10mA/cm^2$에서 2 min, Pt 층을 $5mA/cm^2$에서 1 min 동안 전기 도금한 상대전극의 XRD 분석 결과 Ni 및 Pt의 금속 회절 peak들을 관찰 할 수 있었다. 이렇게 제조한 상대전극을 사용하여 DSSC의 impedance 측정 결과 75 ohm의 가장 낮은 저항을 나타냈으며, 광전 효율은 5.6%로서 가장 높은 값을 나타내었다.

• 한국세라믹학회지
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• 제53권4호
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• pp.393-399
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• 2016

We have successfully fabricated 3D (3-dimensional) nanostructures of $TiO_2$ coated with a $g-C_3N_4$ layer via hydrothermal and sintering methods to enhance photoelectrochemical (PEC) performance. Due to the coupling of $TiO_2$ and $g-C_3N_4$, the nanostructures exhibited good performance as the higher conduction band of $g-C_3N_4$, which can be combined with $TiO_2$. To fabricate 3D nanostructures of $g-C_3N_4/TiO_2$, $TiO_2$ was first grown as a double layer structure on FTO (Fluorine-doped tin oxide) substrate at $150^{\circ}C$ for 3 h. After this, the $g-C_3N_4$ layer was coated on the $TiO_2$ film at $520^{\circ}C$ for 4 h. As-prepared samples were varied according to loading of melamine powder, with values of loading of 0.25 g, 0.5 g, 0.75 g, and 1 g. From SEM and TEM analysis, it was possible to clearly observe the 3D sample morphologies. From the PEC measurement, 0.5 g of $g-C_3N_4/TiO_2$ film was found to exhibit the highest current density of $0.12mA/cm^2$, along with a long-term stability of 5 h. Compared to the pristine $TiO_2$, and to the 0.25 g, 0.75 g, and 1 g $g-C_3N_4/TiO_2$ films, the 0.5 g of $g-C_3N_4/TiO_2$ sample was coated with a thin $g-C_3N_4$ layer that caused separation of the electrons and the holes; this led to a decreasing recombination. This unique structure can be used in photoelectrochemical applications.

• 한국재료학회지
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• 제27권11호
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• pp.631-635
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• 2017

We report facile solution processing of mesoporous hematite (${\alpha}-Fe_2O_3$) thin films for high efficiency solar-driven water splitting. $Fe_2O_3$ thin films were prepared on fluorine doped tin oxide(FTO) conducting substrates by spin coating of a precursor solution followed by annealing at $550^{\circ}C$ for 30 min. in air ambient. Specifically, the precursor solution was prepared by dissolving non-toxic $FeCl_3$ as an Fe source in highly versatile dimethyl sulfoxide(DMSO) as a solvent. The as-deposited and annealed thin films were characterized for their morphological, structural and optical properties using field-emission scanning electron microscopy(FE-SEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and UV-Vis absorption spectroscopy. The photoelectrochemical performance of the precursor (${\alpha}-FeOOH$) and annealed (${\alpha}-Fe_2O_3$) films were characterized and it was found that the ${\alpha}-Fe_2O_3$ film exhibited an increased photocurrent density of ${\sim}0.78mA/cm^2$ at 1.23 V vs. RHE, which is about 3.4 times higher than that of the ${\alpha}-FeOOH$ films ($0.23mA/cm^2$ at 1.23 V vs. RHE). The improved performance can be attributed to the improved crystallinity and porosity of ${\alpha}-Fe_2O_3$ thin films after annealing treatment at higher temperatures. Detailed electrical characterization was further carried out to elucidate the enhanced PEC performance of ${\alpha}-Fe_2O_3$ thin films.

• KEPCO Journal on Electric Power and Energy
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• 제2권1호
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• pp.97-101
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• 2016

산화아연은 다양한 나노 구조와 특유의 특성으로 인하여 여러 분야에서 많은 관심을 받고있는 물질이다. 산화아연을 합성하는 다양한 방법 중에서, 수열합성법은 간단하고 친환경적인 장점을 가지고 있다. 나노 구조를 가지는 산화아연 박막은 수열합성법을 통하여 FTO 전극 위에 제작되었다. 성장된 산화아연은 X-ray diffraction (XRD)와 Field-emission scanning electron microscopy (FESEM)을 통하여 분석되었다. XRD 분석에서 산화아연 박막이 자연상태의 hexagonal wurtzite 상으로 구성되어 있음을 확인하였으며 SEM 사진에서는 나노 로드 형태를 구성하고 있는 것을 확인할 수 있었다. 본 연구에서는 UV 영역의 흡수 스펙트럼을 분석하여 산화아연이 보이는 365 nm 파장에서의 흡수를 확인하였다. 또한 photoluminescence 방출을 분석한 결과, 424 nm의 band edge emission과 500 nm에서 산화아연의 oxygen vacancies에 의한 방출을 확인하였다. 또한 라만 스펙트럼 분석을 통하여 본 연구진이 제작한 산화아연이 높은 결정성을 가지고 있는 것을 확인할 수 있었다. 이러한 연구를 통하여 다양한 특성을 가진 산화아연의 광촉매적 적용을 기대할 수 있다.