• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.318-318
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• 2010

We present the effect of interlayers of polymer tandem solar cells on their photovoltaic performance. P-type and n-type interlayers are essential for the series-connection of the subcells and enable to form the tandem cell architecture by the solution processing. In this study, we use PEDOT:PSS, nanocrystalline $TiO_2$, and blends of semiconducting polymers and fullerene derivatives as a hole transporting layer, electron transporting layer, and photoactive layers, respectively. We show that photovoltaic performances of polymer tandem solar cells depending on various PEDOT:PSS layers with the different electric conductivity and the various $TiO_2$ layer thickness.

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.334-340
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• 2002

$TiO_2$-coated fly ash was synthesized by dropping method of coating agent in order to get $TiO_2$ coating layer with high photocatalytic activity on the surface of coal fly ash. The properties of the $TiO_2$ coating layer such as morphology, crystal structure, crystal size and photocatalytic activity were compared with those of the $TiO_2$-coated fly ash prepared by the traditional method of precipitation. $TiCl_4$ aqueous solution was used as a titanium stock solution and $NH_4HCO_3$ was used as a precipitant. The $TiO_2$ coating layer obtained by dropping method of coating agent was more uniform than that coated by precipitation. However, the crystal of $TiO_2$ coated by dropping method of coating agent was easy to grow by heat treatment because of the small primary particle size and bulky morphology, and its photocatalytic activity was consequently lower than that of the $TiO_2$ coated by precipitation. The $TiO_2$ coating layer obtained by both methods had a crystal structure of anatase, and the temperature of phase transformation into rutile was 90$0^{\circ}C$. The minimum crystal size of $TiO_2$ for the highest photocatalytic activity was found to be about 10nm.

• Transactions on Electrical and Electronic Materials
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• v.10 no.5
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• pp.177-181
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• 2009

Employing statistical design of experiments, we have performed studies on the characterization of electrodes using $TiO_2$ and process variables in the fabrication process of nanocrystalline dye sensitized solar cell. Systematic experiment to identify the effects of process variables on cell's efficiency has based on broad-band absorption of light by tailor made organometallic dye molecules dispersed on a high surface of $TiO_2$. Employing statistical design of experiment on $TiO_2$ photoelectrode forming process, structural characterization of electrodes and process variable have been investigated. Through the statistical analysis we have found that the particle size of $TiO_2$ and the amount of PEG/PEO are significantly affecting on the cell efficiency. In addition, a significant amount of interaction exists between the particle size and the amount of PEG/PEO.

• Bulletin of the Korean Chemical Society
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• v.31 no.1
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• pp.116-119
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• 2010

Adsorption structures of the self-assembled thin films of $\alpha$-cyano-4-hydroxycinnamic acid (CHCA) anchoring on $TiO_2$ surfaces have been studied by using temperature-dependent diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy. From the presence of the strong $\nu(COO^-)$ band at ~1390 $cm^{-1}$ along with the disappearance of the OH bands in the carboxylic acid group in the DRIFT spectra at room temperature, CHCA appeared to adsorb onto $TiO_2$ surfaces as a carboxylate form. The absence of the out-of-plane benzene ring modes of CHCA in the DRIFT spectra suggests a rather vertical orientation of CHCA on $TiO_2$. Above ~220$ ^{\circ}C$, CHCA seemed to start to thermally degrade on $TiO_2$ surfaces referring from the disappearance of most vibrational modes in the DRIFT spectra, whereas the $\nu$(C ≡ N) bands were found to remain relatively conspicuous as the temperature increased even up to ~460$^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1188-1194
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• 2013

Transparent $TiO_2$ thin films have been prepared by sol-gel spin coating method. The sols used for deposition of thin films were prepared with different ethanol content. The effect of ethanol (solvent) concentration and annealing temperature on the performance of $TiO_2$ thin film solar cells has been studied. The results indicate that the as deposited films are amorphous in nature. $TiO_2$ thin films annealed at temperatures above $350^{\circ}C$ exhibited crystalline nature with anatase phase. The results also indicated that the crystallinity of the films improved with increase of annealing temperature. The high resolution transmission electron microscope images showed lattice fringes corresponding to the anatase phase of $TiO_2$. The band gap of the deposited films has been found to decrease with increase in annealing temperature and increase with increase in ethanol concentration. The dependents of photovoltaic efficiency of the dye-sensitized $TiO_2$ thin film solar cells (DSSCs) with the amount of ethanol used to prepare thin films was determined from photocurrent-voltage curves.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.2
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• pp.153-158
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• 2012

We use UV(ultraviolet)-$O_3$ treatment to increase the surface area and porosity of $TiO_2$ films in dye-sensitized solar cells (DSSCs). After the UV-$O_3$ treatment, surface area and porosity of the $TiO_2$ films were increased, the increased porosity lead to amount of dye loading and solar conversion efficiency was improved. Field emission scanning electron microscopy images clearly showed that the nanocrystalline porosity of films were increased by UV-$O_3$ treatment. The Brunauer, Emmett, and Teller surface area of the $TiO_2$ films were increased from $0.71cm^2/g$ to $1.31cm^2/g$ by using UV-$O_3$ treatment for 20 min. Also, UV-$O_3$ treatment of $TiO_2$ films significantly enhanced their solar conversion efficiency. The efficiency of the films without treatment was 4.9%, and was increased to 5.6% by UV-$O_3$ treatment for 20 min. Therefore the process enhanced the solar conversion efficiency of DSSCs, and can be used to develop high sensitivity DSSCs.

• Journal of Hydrogen and New Energy
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• v.16 no.2
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• pp.130-135
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• 2005

Cadmium selenide is one of the group IIb-VI compounds, which is the promising semiconductor material due to its wide range of technological applications in optoelectronic devices such as photoelectrochemical cells, solid state solar cells, thin film photoconductors etc. CdSe has optical band gap of 1.7-1.8eV and proper conduction band edge for water splitting. CdSe films are coated with small thickness(20-50nm) nanocrystalline $TiO_2$ film by electrodeposition or chemical bath deposition methods and PEC properties of CdSe and CdSe/$TiO_2$ sandwich structure are studied. The photoactivity of CdSe and CdSe/$TiO_2$ films deposited on titanium substrate is studied in aqueous electrolyte of 1M NaOH solution. Photocurrent and photovoltage obtained were of the order of 2-4 mA/$cm^2$ and 0.5V, respectively, under the intensity of illumination of 100 mW/$cm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.12
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• pp.878-881
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• 2013

In this study, we have fabricated the dye sensitized solar cell (DSSC) composed by a transparent conductive oxide (TCO), a nanocrystalline semiconductor film usually $TiO_2$, a sensitizer adsorbed on the surface of the semiconductor, an electrolyte containing a redox mediator and a counter electrode. The $TiO_2$ nanopowder was prepared by sol-gel methode. The HCl (hydrochloric acid) and TBAOH (Tetrabutyl amonium hydroxide) was added for improving the catalyst and distributed properties of $TiO_2$ nanopowder. Ammonium hydroixde was added in order to control the morphology and size of $TiO_2$ nano crystal. A $TiO_2$ paste for working electrode was prepared with the addition of HPC (hydroxypropyl cellulos) used as a binder of which volume was controled as 1.3, 1.5, 1.7, and 2.0%. The measured I-V curves of assembled DSSC showed that the cell with 1.7% HPC binder had the best efficiency of 6.79%.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.535-539
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• 2002

In this study photoadsorption propreties of Ag ion in AgNO$_3$ solution by TiO$_2$nanopowder synthesized by homogeneous precipitation process at low temperature were investigated. It was found that the photocatalytic redliction in AgNO$_3$solution was occurred by TiO$_2$nanopowder even under th sun light irradiation, although the reduction of Ag ions was slow with th small adsorption of 9.32 ppm. Notably the Ag adsorption was promoted in th dark condition probably owing to the chestnut bur shape of TiO$_2$ nanopowder itself. In the application of UV the Ag ions were completely adsorbed within 120 min, showing more significant photocatalytic reaction. The measured adsorption reaction rate and adsorption equilibrium rate constants were 0.0004 g/min and 1494.20(120 $m^2$/g), respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.213-213
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• 2010

In this thesis, we studied to increased to solar conversion efficiency of DSSC (dye-sensitized solar cell) using nanocrystalline $TiO_2$ semiconductor. We are preparation of $TiO_2$ photoelectrode, assembly the DSSC and put a focus in analyses electrochemical properties of DSSC and using Silica powder in $TiO_2$ photoelectrode for increase light scattering effect and improved conversion efficiency. It attempt to investigate the morphology of the photoelectrode and photovoltaic effects using field emission scanning electron microscopy (FE-SEM) and photovoltaic properties under illumination with AM 1.5 simulated sunlight. We got 146 % enhanced power conversion efficiency when the optimal content of quartz glass powder was 5 wt.% than that another content.