Effects of solvents on the synthesis of CuInSe2 nanoparticles for thin film solar cells.

Chalcopyrite CuInSe2 (CIS) nanoparticles were synthesized in oleic acid, 1-octadecene, oleyl amine and tetraethylene glycol at temperature above 200 degrees C. Depending on the solvent used and reaction temperature, the obtained nanoparticles had different shapes, sizes, chemical compositions, and crystal and thermal properties. CIS powders synthesized in oleic acid, 1-octadecene and oleyl amine above 200 degrees C exhibited chalcopyrite structure. On the other hand, powders prepared in tetraethylene glycol contained a mixture of CIS and CuSe compounds. The CIS powder obtained in oleyl amine had a high thermal stability over 500 degrees C. CIS thin films prepared from nanoparticles were heat-treated in order to observe changes in their property. After 10 min heat-treatment at 500 degrees C, their crystal structure and chemical composition were slightly changed, and their band gap energies were ca. 1.01 eV except in the case of powders prepared in tetraethylene glycol.

A new deposition method for the preparation of Pt-Pd nanocatalysts on a nafion coated carbon black via the reduction of metallic precursors in a drying process.

A simple method for the synthesis of Pt-Pd nanocatalysts was developed for a proton-exchange membrane fuel cell (PEMFC), which was loaded on a nafion coated carbon black via the sequential reduction of palladium(II) bis(acetylacetonato) and platinum(II) bis(acetylacetonato) in a drying process. Metallic precursors were sublimed and reduced on a nafion coated carbon black which was spray coated on a gas diffusion layer (GDL) in a glass reactor of N2 atmosphere at 180 degrees C for various times. The morphology and distribution of the Pt and Pd nanoparticles were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and we found that the loading weight, number density and particle size of Pt-Pd nanoparticles increased with increasing exposure time at 180 degrees C.

Effect of the nanosized TiO2 particles in Pd/C catalysts as cathode materials in direct methanol fuel cells.

Pd-TiO2/C catalysts were prepared by impregnating titanium dioxide (TiO2) on carbon-supported Pd (Pd/C) for use as the catalyst for the oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFCs). Transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were carried to confirm the distribution, morphology and structure of Pd and TiO2 on the carbon support. In fuel cell test, we confirmed that the addition of TiO2 nanoparticles make the improved catalytic activity of oxygen reduction. The electrochemical characterization of the Pd-TiO2/C catalyst for the ORR was carried out by cyclic voltammetry (CV) in the voltage window of 0.04 V to 1.2 V with scan rate of 25 mV/s. With the increase in the crystallite size of TiO2, the peak potential for OH(ads) desorption on the surface of Pd particle shifted to higher potential. This implies that TiO2 might affect the adsorption and desorption of oxygen molecules on Pd catalyst. The performance of Pd-TiO2/C as a cathode material was found to be similar to or better performance than that of Pt/C.

Performance of PtPd electrocatalysts in direct methanol fuel cell.

PtPd nanoparticles on carbon black were prepared to investigate the role of Pd in the anode and cathode of a direct methanol fuel cell (DMFC). The PtPd catalysts in the anode showed a significantly lower performance than the PtRu catalyst. However, the cell performances of these catalysts in the cathode were comparable to that of the Pt catalyst. From cyclic voltammetry, it was observed that the Pd with the Pt catalyst lowered the peak potential and increased the coulombic charge for oxide reduction on the surface of the catalyst. Also, the Pd catalyst without Pt showed relatively high activity for oxygen reduction reaction.

Synthesis and characterization of Pt-Pd catalysts for methanol oxidation and oxygen reduction.

Pt-Pd nanoparticles supported on carbon black were prepared and characterized as electrocatalysts for methanol oxidation and oxygen reduction in an acidic solution. The Pt and Pd nanoparticles were impregnated spontaneously on the carbon black through a simple reducing process. X-ray diffraction, transmission electron microscopy, and electrochemical measurement were carried out to characterize the crystal structure, particle size, and catalytic activities of the Pt-Pd catalysts. The results showed that the Pt-Pd catalysts had higher catalytic activities for methanol oxidation reaction than pure Pt catalysts. The catalytic activity of the Pt-Pd catalysts for oxygen reduction reactions in the presence of methanol was higher than that of pure Pt and Pd. These results indicate that the Pt-Pd catalysts are suitable as electrocatalysts of both the anode and the cathode in direct methanol fuel cells.

Influence of Deposition Conditions on Properties of All Sputtered CdS/CdTe Thin-Film Solar Cells.

The effects of deposition conditions, such as substrate temperature and CdCl2 post treatments, on the structural and optical properties of CdTe films were investigated. In addition, CdS/CdTe thin-film solar cells were fabricated by an all-sputtering process, and their photovoltaic characteristics were studied. The CdTe films had a polycrystalline, cubic structure with a preferred orientation of the [1 1 1] direction parallel to the substrate surface, regardless of the substrate temperature. As the substrate temperature increased, the crystallinity of CdTe films improved. The grain size of the CdTe films increased after CdCl2 post treatment. In addition, the optical band gap increased with the substrate temperature. The conversion efficiency of the CdS/CdTe solar cell improved at higher substrate temperatures. The maximum efficiency, 9.23%, was obtained at a substrate temperature of 400 degrees C, with an open-circuit voltage (V(oc)) of 0.78 V, a short-circuit current density (J(sc)) of 20.4 mA/cm2, and a fill factor of 0.58.

Synthesis of CZTS Nanoparticles for Low-Cost Solar Cells.

In this work, uniformly sized Cu2ZnSnS4 (CZTS) nanoparticles with easy control of chemical composition were synthesized and printable ink containing CZTS nanoparticles was prepared for low-cost-solar cell applications. In addition, we studied the effects of synthesis conditions, such as reaction temperature and time, on properties of the CZTS nanoparticles. For CZTS nanoparticles synthesis process, the reactants were mixed as the 2:1:1:4 molar ratios. The reaction temperature and time was varied from 220 degrees C to 320 degrees C and from 3 hours to 5 hours, respectively. The crystal structure and morphology of CZTS nanoparticles prepared under the various conditions were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS) was used for compositional analysis of the CZTS nanoparticles.

Synthesis and characterization of CIS nanoparticle ink for low-cost thin film solar cells.

CuSe and CuInSe2 nanoparticles were synthesized through the aqueous solution process using NaBH4 solution as a solvent and subsequent heat-treatment. Not only the synthesized nanoparticles, CuSe and CuInSe2, but also spray-coated thin films prepared by using CuSe and CuInSe2 were characterized by XRD, SEM-EDS, TGA and UV-Vis spectroscopy. CuSe nanoparticles with a plate-like shape, which were confirmed by XRD and SEM, were directly prepared by a reaction of a mixture of CuCl2 and Se in the aqueous solution of NaBH4 at room temperature. Cu-In-Se compounds were obtained through the reaction of CuCl2, InCl3, and Se in the aqueous solution of NaBH4, were consisted of the mixture of CuSe(x) and In hydroxides, and were transformed into CuInSe2 with a chalcopyrite structure by a heat-treatment at 300 degrees C.