• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.218-223
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• 2010

The zinc oxide thin film, which can be applied as the gas sensor of a semiconductor type, was grown on the silicon substrate by CFR(continuous flow reaction) method in this study. The growth property and the electrical property of the zinc oxide thin films synthesized by CFR method were also investigated. Zinc acetate solutions of 0.005~0.02 M were used as the precursor for the preparation of zinc oxide thin films. The size of ZnO particles consisted on the zinc oxide thin film increased not only with increasing concentration of precursor, but also the thickness of thin film increased. The growth rate of zinc oxide thin film by CFR method was proportionably depend on the concentration of precursor and the uniform ZnO thin film was prepared when zinc acetate of 0.01 M is used as the precursor. The charged currents on the zinc oxide thin films were obtained as its electrical property by I-V meter, and increased agree with increasing the thickness of zinc oxide thin film. Thus, it was concluded that the charged current on the zinc oxide thin film can be controlled with changing concentration of precursor solution in CFR method. The charged currents on the zinc oxide thin films also decreased when ZnO thin film is exposed under hydrogen sulfide of 500 ppmv at $300^{\circ}C$ for 5 min. From these results, it could be confirmed that the zinc oxide thin film prepared by CFR method can be used for the detection of sulfur compounds.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.98.2-98.2
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• 2012

Thin film solar cells are growing up in the market due to their high efficiency and low cost. Especially CdTe and $CuInGaSe_2$ based solar cells are leading the other cells, but due to the limited percentage of the elements present in our earth's crust like Tellurium, Indium and Gallium, the price of the solar cells will increase rapidly. Copper Zinc Tin Sulfide (CZTS) and Copper Zinc Tin Selenide (CZTSe) semiconductor (having a kesterite crystal structure) are getting attention for its solar cell application as the absorber layer. CZTS and CZTSe have almost the same crystal structure with more environmentally friendly elements. Various authors have reported growth and characterization of CZTSe films and solar cells with efficiencies about 3.2% to 8.9%. In this study, a novel method to prepare CZTSe has been proposed based on selenization of stacked Copper Selenide ($Cu_2Se$), Tin Selenide ($SnSe_2$) and Zinc Selenide (Zinc Selenide) in six possible stacking combinations. Depositions were carried out through RF magnetron sputtering. Selenization of all the samples was performed in Close Space Sublimation (CSS) in vacuum at different temperatures for three minutes. Characterization of each sample has been performed in Field Emission SEM, XRD, Raman spectroscopy, EDS and Auger. In this study, the properties and results of $Cu_2ZnSnSe_4$ thin films grown by selenization will be presented.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2523-2528
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• 2012

Green phosphors $(Zn_{1-a-b}M_aM^{\prime}_b)_xGa_yS_{x+3y/2}:Eu^{2+}$ (M, M' = alkali earth ions) with x = 2 and y = 2-5 were prepared, starting from ZnO, MgO, $SrCO_3$, $Ga_2O_3$, $Eu_2O_3$, and S with a flux $NH_4F$ using a conventional solidstate reaction. A phosphor with the composition of $(Zn_{0.6}Sr_{0.3}Mg_{0.1})_2Ga_2S_5:Eu^{2+}$ produced the strongest luminescence at a 460-nm excitation. The observed XRD patterns indicated that the optimized phosphor consisted of two components: zinc thiogallate and zinc sulfide. The characteristic green luminescence of the $ZnS:Eu^{2+}$ component on excitation at 460 nm was attributed to the donor-acceptor ($D_{ZnGa_2S_4}-A_{ZnS}$) recombination in the hybrid boundary. The optimized green phosphor converted 17.9% of the absorbed blue light into luminescence. For the fabrication of light-emitting diode (LED), the optimized phosphor was coated with MgO using magnesium nitrate to overcome their weakness against moisture. The MgO-coated green phosphor was fabricated with a blue GaN LED, and the chromaticity index of the phosphor-cast LED (pc-LED) was investigated as a function of the wt % of the optimized phosphor. White LEDs were fabricated by pasting the optimized green (G) and the red (R) phosphors, and the commercial yellow (Y) phosphor on the blue chips. The three-band pc-WLED resulted in improved color rendering index (CRI) and corrected color temperature (CCT), compared with those of the two-band pc-WLED.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1009-1012
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• 2003

A novel powder processing technique for the preparation of copper activated zinc sulfide (ZnS:Cu,Al) phosphor by combustion process has been proposed. Exothermic reaction between dissolved copper nitrate and carbohydrazide give small-sized particles in presence of alkali metal halides at lower temperature than the traditional method of preparation. This new route takes less than five minutes and requires much less energy. The optical and luminescence characteristics of ZnS:Cu,Al phosphor thus prepared were found to be enhanced significantly. Carbohydrazide acted as fuel at $500^{\circ}C$ with rapid heating and then the phosphors obtained were heated at $900^{\circ}C$ in an inert atmosphere for 3hrs to get better luminescent properties.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.356-361
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• 2015

$Cd_{0.5}Zn_{0.5}S/ZnO$ composite photocatalysts were synthesized using the precipitation method and characterized by XRD, UV-vis DRS, PL and FE-SEM. Photocatalytic activities of the materials were evaluated by measuring the degradation of rhodamine B under visible light irradiation. Contrary to ZnO, $Cd_{0.5}Zn_{0.5}S/ZnO$ materials absorb visible light as well as UV and their absorption intensities in visible region increased with increasing the $Cd_{0.5}Zn_{0.5}S$ amount. The increment in the $Cd_{0.5}Zn_{0.5}S$ content in $Cd_{0.5}Zn_{0.5}S/ZnO$ also leads to reducing the particle size and consequently increasing the specific surface area. $Cd_{0.5}Zn_{0.5}S/ZnO$ materials with the larger $Cd_{0.5}Zn_{0.5}S$ content showed the higher activity in the photocatalytic degradation of rhodamine B under visible light irradiation. Therefore, the heterojunction effect between $Cd_{0.5}Zn_{0.5}S$ and ZnO as well as the adsorption capacity seems to give important contributions to the photocatalytic activity of the $Cd_{0.5}Zn_{0.5}S/ZnO$.

• Current Photovoltaic Research
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• v.1 no.2
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• pp.109-114
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• 2013

$Cu_2ZnSnS_4$ (CZTS) nanoparticles were synthesized by a solvothermal method using copper (II) acetate, zinc acetate, tin chloride, and sulfur in diethylenetriamine solvent. Binary sulfide particles such as CuS, ZnS, SnS, and $SnS_2$ were obtained at $180^{\circ}C$; single-phase CZTS nanoparticles were obtained at $280^{\circ}C$. CZTS nanoparticles with spherical shape and grain size of 40 to 60 nm were obtained at $280^{\circ}C$. In the middle of 180 and $280^{\circ}C$, CZTS and ZnS phases were found. The time variation of reaction at $280^{\circ}C$ revealed that an amorphous state formed first instead of binary phases and then the amorphous phase was converted to crystalline CZTS state; it is different reaction path way from conventional solid-state reaction path of which binary phases react to form CZTS. CZTS films deposited and annealed from single-phase nanoparticles showed porous microstructure and poor adhesion. This indicates that a combination of CZTS and other flux phase is necessary to have a dense film for device fabrication.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.656-662
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• 2021

For the high efficiencies of quantum dot-sensitized solar cells (QDSCs), it is important to control the severe electron recombination at the interface of photoanode/electrolyte. In this work, we optimize the surface passivation process of ZnS/SiO₂ double overlayers for the enhanced photovoltaic performances of QDSCs. The overlayers of zinc sulfide (ZnS) and SiO₂ are coated on the surface of QD-sensitized photoanode by successive ionic layer adsorption and reaction (SILAR) method, and sol-gel reaction, respectively. In particular, for the sol-gel reaction of SiO₂, the influences of temperature of precursor solution are investigated. By application of SiO₂ overlayers on the ZnS-coated photoanode, the conversion efficiency of QDSCs is increased from 5.04% to 7.35%. The impedance analysis reveals that the electron recombination at the interface of photoanode/electrolyte is obviously reduced by the SiO₂ overlayers.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.249.2-249.2
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• 2015

Connecting two or more sub-cells is a simple and effective way of improving power conversion efficiency (PCE) of solar cells, and the theoretical efficiency of this tandem cell is known to reach 85~88% of the sum of the sub-cell's efficiencies. There are two ways of connecting sub-cells in the tandem structure, i.e. parallel and series connection. The parallel connection can increase the short circuit current (Jsc) and the series connection can increase the open circuit voltage (Voc). Although various tandem structures have been studied, the full use of incident light and optimization of cell efficiency is still limited. In this work, we designed series tandem solar cells consisting of lead sulfide (PbS) quantum dots/zinc oxide-based QDSC and zinc phthalocyanine (ZnPc)/C60-based small molecule OSCs. It is expected that the loss of the incident light is minimized because the absorption range of the PbS quantum dots and ZnPc is significantly different, and the Voc increases according to the Kirchhoff's law.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3723-3729
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• 2010

We investigated the high-excitation voltage cathodoluminescence (CL) performance of blue light-emitting (ZnS:Ag,Al,Cl) and green light-emitting (ZnS:Cu,Al) phosphors coated with metal oxides ($SiO_2$, $Al_2O_3$, and MgO). Hydrolysis of the metal oxide precursors tetraethoxysilane, aluminum isopropoxide, and magnesium nitrate, with subsequent heat annealing at $400^{\circ}C$, produced $SiO_2$ nanoparticles, an $Al_2O_3$ thin film, and MgO scale-type film, respectively, on the surface of the phosphors. Effects of the phosphor surface coatings on CL intensities and aging behavior of the phosphors were assessed using an accelerating voltage of 12 kV. The MgO thick film coverage exhibited less reduction in initial CL intensity and was most effective in improving aging degradation. Phosphors treated with a low concentration of magnesium nitrate maintained their initial CL intensities without aging degradation for 2000 s. In contrast, the $SiO_2$ and the $Al_2O_3$ coverages were ineffective in improving aging degradation.

• Journal of Powder Materials
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• v.12 no.4 s.51
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• pp.279-283
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• 2005

In this study, the ZnS composite powders for host material in phosphor was synthesized in situ by mechanical alloying. As the mechanical alloying time increases, particle size of ZnS decreases. ZnS powders of $1.85\;\mu{m}$ in a mean size was fabricated by mechanical alloying for 10h. The crystal structures of ZnS powders were investigated by X-ray diffraction and the photo-luminescence properties was evaluated with the optical spectra analyzer. The steady state condition of mechanically alloyed ZnS was obtained as a mean particle size of $2\;\mu{m}$ in 5h milling. The sphalerite and wurtize structures coexist in the ZnS mechanically alloyed for 5h. The ZnS powder mechanically alloyed for 10h grows to the sphalerite structure. And the strong emission peaks of ZnS are observed at 480 nm wave length at the powders of mechanically alloyed for 10h, but the sphalerite and wurtize structures in ZnS coexist and emission peaks are not appeared at the powders of mechanically alloyed for 10h.