Songyi Park

Melamine resin microcapsules containing fragrant oil: synthesis and characterization

Melamine resin microcapsules with long self-life containing fragrant Migrin oil were prepared by in situ polymerization from Migrin oil as core material, melamine and formaline as wall materials, sodium lauryl sulphate as emulsifier and poly(vinyl alcohol) as protective colloid. Melamine resin microcapsules were characterized on structure, a mean particle size and size distribution, morphologies, thermal properties and release behavior.

Study on characteristics of CdS quantum dot-sensitized solar cells prepared by successive ionic layer adsorption and reaction with different adsorption times

Cadmium sulfide (CdS) quantum dots (QDs) were adsorbed on a titanium dioxide (TiO2) nanoporous film by successive ionic layer adsorption and reaction (SILAR) method with different adsorption times to study the influences of different SILAR adsorption times on CdS quantum dot-sensitized solar cells (QDSCs). The optical properties of CdS sensitized TiO2 films were studied by scanning electron microscopy and UV-Vis absorbance spectroscopy. The particle size of the CdS QDs was approximated using the effective mass approximation theory from the absorbance spectra. The photovoltaic characteristics of the CdS QDSCs were analyzed by I–V characteristics and electrochemical impedance spectroscopy under air mass 1.5 illumination. As a result, the particle size of the CdS QDs became larger and light harvesting was enhanced with increasing SILAR adsorption time. The maximum photovoltaic conversion efficiency of the CdS QDSCs (1.86%) was obtained at the SILAR adsorption time of 30 min with the highest short circuit current density and lowest charge transfer resistance.

The effects of electrolyte additives on the cell performances of CdS/CdSe quantum dot sensitized solar cells

The electrolyte for QDSSCs is normally a polysulfide, S2−/Sx2−, redox couple. This couple plays an important role for the regeneration of quantum dots. This study examined the effects of the electrolyte for CdS/CdSe QDSSCs. Electrolytes consisting of 1M Na2S, 2M S in a methanol and water-mixed solution at a 7: 3 ratio with or without additives such as KCl, NaOH, KOH and NaCl were used for QDSSC. The electrolyte with NaOH showed the highest conversion efficiency, 3.18%. The reasons for the improved photovoltaic characteristics were analyzed using a range of techniques.

Fabrication of mesoporous TiO2 double layer using dicarboxylic acid in dye-sensitized solar cell

Several techniques have been used to prepare titanium dioxide (TiO2) paste from commercially available powders for applications in dye-sensitized solar cells (DSCs). In this study, submicron-sized TiO2 agglomerates with mesopores (2–50 nm) were prepared using a dicarboxylic acid, adipic acid. This type of acid creates new hydroxyl groups that increase the surface area and level of dye adsorption. The adipic acid-added mesoporous TiO2 exhibited light scattering effect at a comparable wavelength with a lower back-scattering efficiency. The effects of the TiO2 paste components, such as the morphology, characteristics and structure, were examined and comparative studies were performed using acetic acid added-TiO2 nanoparticles.

Analysis on the Light-Scattering Effect in Dye-Sensitized Solar Cell according to the TiO2 Structural Differences

A light-scattering layer is widely used in highly efficient dye-sensitized solar cells (DSCs) because it improves the light-harvesting ability of a DSC by reflecting the light passing through the transparent TiO2 layer. Among many parameters affecting this light-scattering effect, the thickness of the TiO2 photoelectrode is also a significant parameter. However, most studies regarding the influence of the TiO2 photoelectrode thickness on the light-scattering effect have only focused on the thickness of the transparent TiO2 layer and have ignored the light-scattering layer thickness itself. Therefore, in this study, we analyzed the light scattering effect according to the thickness of the light-scattering layer and the resulting photovoltaic performance of the DSC. Finally, it was confirmed that the light-scattering effect is enhanced to some degree with the increase of the light-scattering layer thickness, while it is weakened when the light-scattering layer thickness is further increased.

A Study on FTO-less Dye Sensitized Solar Cell with Ti Deposited Glass

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.

Growth of ZnO Nanorod with High-quality Assisted by an External Electric Field

In this study, the ZnO nanorod is grown on the seed layered glass substrate by applying an external electric field to fabricate the ZnO nanorod with the high quality and to increase the yield of the ZnO nanorod. It is possible to grow the definite and clear hexagonal ZnO nanorod as the cathode of the high voltage is connected to the side of the seed layered glass substrate and the anode is connected to the opposite side because more ions are located around the ZnO seed layer and are accumulated easily due to the external electric field. As a result, it is succeeded to fabricate the definite hexagonal ZnO nanorod having better structural characteristics by applying the external electric field during the growth process. Therefore, it is demonstrated that the external electric field is effective to fabricate the high quality ZnO nanorod without changing any composition of the ZnO nanorod.