Solid State Phenomena Vols. 124-126

Abstract: Cu(In,Ga)3Se5 films were deposited on soda-lime glass substrate by three-stage co-evaporation process. In the film, the band gap increased as the Cu content decreased and also as the Ga content increased. The grain size became smaller as the Ga content increased. In the Cu1.29(In1-xGax)3Se5 system, the maximum hole concentration was 1x1015 /cm3 when the Ga content was 0.5 and its band gap was 1.45 eV. Comparing the conventional CIGS solar cell with Cu0.8(In0.7Ga0.3)Se2 film, the series resistance is too large, indicating that further p-type doping in the Cu(In,Ga)3Se5 film is necessary to improve cell efficiency for the top cell application in CIGS tandem solar cells.

Abstract: We fabricated a CdS nano structures/CdS window layer/ ITO coated glass using electrodeposition and nano imprinting technology (NIT). The CdS nano-structures were electrodeposited using Na2S2O3 and CdSO4 electrolytes as the CdS sources and nano-imprint templates. The x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS) results show the electrodeposited CdS window layer and the secondary electron microscopy (SEM) analysis showed the well aligned CdS nano-structure shape.

Abstract: The effect of lithium salts such as LiPF6, LiBF4, LiCF3SO3 and LiN(CF3SO2)2 (LiTFSI) in tetra(ethylene glycol) dimethyl ether (TEGDME) electrolyte on the ionic conductivity, interfacial resistance and discharge properties of Li/pyrite cell at room temperature was studied. The electrolytes had good ionic conductivity at room temperature in the range 0.61 to 1.86 × 10-3 S/
. The discharge capacities of Li/pyrite cells with 1M LiPF6 and LiBF4 in TEGDME were lower compared to those of the other two non-HF containing salts. The best cycle performance was exhibited by LiTFSI in TEGDME electrolyte, with a discharge capacity of 438 mAhg-1 after 20 cycles, which is ~49% of FeS2 theoretical capacity (894 mAhg-1). The good performance of LiTFSI-TEGDME electrolyte resulted mainly from its low interfacial resistance in Li/FeS2 cells, which showed a decreasing trend with cycling.

Abstract: CuIn1-xAxlSe2(CIAS) films were obtained by selenization process of metallic precursors. The metallic precursors were deposited sequentially by using sputtering system. As the ratio of Al/(Al+In) in the precursors increased, the chalcopyrite (112) peak shifted to high value and the band-gap of CIAS layer increased to 1.38 eV. However, the bi-layer morphology with well crystallized large grain on the surface and small grain thin bottom layer was observed. Although the sequences of precursors were changed in order to get uniform layer, no distinguishable difference was not observed.

Abstract: The currently used cathode material for secondary batteries such as LiCoO2 exhibited limit to further improve the functionality of the batteries, since the screen printing method cannot reduce the thickness of the battery further with the solid state reacted powder which has the size of several micrometer. In this study, we have synthesized Li(NiCoMn)O2 thin film to replace LiCoO2 thick film by employing Li-diffusion reaction on the surface of the textured Ni-Co-Mn alloy. The cube-textured Ni-Mn alloy was prepared by cold-isostatic pressing of mixed Ni-Mn powder, sintering, repeated rolling process, and annealing heat treatment for texture development. After thin layer of metallic Li was deposited on the surface of Ni-Co-Mn template using thermal evaporation method in the glove box or pulsed laser deposition, the Li/Ni-Co-Mn composite tape were heat treated at 800~900°C for 1~2hrs in oxidizing atmosphere to induce Li diffusion into the Ni-Co-Mn template and Li(NiCoMn)O2 phase formation. The Li(NiCoMn)O2 phase evolution was confirmed by XRD and microstructural characteristics such as grain size and surface morphology were analyzed by scanning electron microscopy and atomic force microscopy. Also the charge and discharge test was conducted to confirm the electrical characteristics of Li(NiCoMn)O2/Ni-Co-Mn thin film for the cathode application.

Abstract: To make a dense CIGS absorber layer, spray deposited CIGS films were annealed in the two-zone RTP furnace in Se atmosphere. More Se supply by increasing Se evaporation temperature or by increasing the flow rate of carrier gas resulted in the larger CIGS grains. However, a thick MoSe2 layer was formed between CIGS and Mo, as the Se supply increased, results in partial detachment of CIGS/MoSe2/Mo layers from the glass substrate. From the result, it was found that the short heat- treatment with high Se vapor pressure is better than the long heat-treatment with low Se vapor pressure. The large CIGS grains without peeling off, can be obtained from the following conditions; Se evaporation temperature of 450oC, substrate temperature of 550oC, annealing time of 5 min, and flow rate of carrier gas of 30 sccm.

Abstract: An Electrochemical etching was used to form the porous silicon (PS) layer on the surface of the crystalline silicon wafer. The PS layer, in this study, will act as an antireflection coating to reduce the reflection of the incident light into the solar cell. The etching solution (electrolyte) was prepared by mixing HF (50%) and ethanol which was introduced for efficient bubble elimination on the silicon surface during etching process. The anodization of the silicon surface was performed under a constant current (galvanostat mode of the power supply), and process parameters, such as current density and etching time, were carefully tuned to minimize the surface reflectance of the heavily-doped wafer with sheet resistance between 20-30
/
.

Abstract: Zr57V36Fe7 alloy is widely used as non-evaporable getter(NEG) material because of its high sorption properties for various gases and relatively low activation temperature. Structurally, it is composed of two phases i.e. AB2 type cubic Laves and hexagonal α-Zr solid solution. The activation and sorption behavior of Zr57V36Fe7 alloy getter was explained in terms of its component phases. It was found that the activation of the alloy is stimulated by the presence of cubic-Zr(V, Fe)2 phase. It is believed that once activated α-Zr solid solution enhance, the sorption of hydrogen.

Abstract: Natural graphite anodes were treated by different methods to improve their cyclability. We tried following methods; heat-treatment at 550oC for graphite powder, addition of carbon black for electrode and VC (vinylene carbonate) in electrolyte. All methods decreased capacity fade rate during constant cycling. The addition of carbon black decreased capacity fade significantly but increased irreversible capacity much at first cycle. Heat-treatment and VC were also effective for cycling and irreversible capacity loss.