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"Aspect ratio"

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"Aspect ratio"

Synthesis and Shape Control of Goethite Nano Particles
Hyun-bin Choi, Myoung-pyo Chun, Seung-yeop Chun, Jin-ah Hwang
J Electr Electron Mater 2016;29(9):552-558.   Published online September 1, 2016
Goethite, α-FeOOH have various applications such as absorbent, pigment and source for magnetic materials. Goethite particles were synthesized in a two step process, where Fe(OH)2 were synthesized in nitrogen atmosphere using FeSO4 as a raw material in the first process, and after that acicular goethite particles were obtained in an air oxidation process of Fe(OH)2 in highly alkaline aqueous solution. Their phase and microstructure were investigated with XRD and FE-SEM. It was found that the morphology of goethite and the ratio of length-to-width (aspect ratio) of acicular goethite are dependent on the some factors such as R value (OH-/Fe2+), air flow rate and pH conditions. In particular, R value has the strongest influence on the synthesized goethite morphology. It is considered that the optimal value R is 4.5 because X-ray diffraction peaks of goethite have the highest intensity at that value. Morphology of goethite particles was controlled by air flow rates, showing that their size and aspect ratio are getting smaller and decrease, respectively as air flow rate increases. The largest goethite particle obtained is about 1,500 nm in length and 150 nm in diameter.
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Energy Materials : Multi-Layer Front Electrode Formation to Improve the Conversion Efficiency in Crystalline Silicon Solar Cell
Hee Eun Song, Ji Hwa Hong, Min Gu Kang, Nam Soo Kim
J Electr Electron Mater 2012;25(12):1015-1020.   Published online December 1, 2012
Resistance of the front electrode is the highest proportion of the ingredients of the series resistance in crystalline silicon solar cell. While resistance of the front electrode is decreased with larger area, it induces the optical loss, causing the conversion efficiency drop. Therefore the front electrode with high aspect ratio increasing its height and decreasing is necessary for high-efficiency solar cell in considering shadowing loss and resistance of front electrode. In this paper, we used the screen printing method to form high aspect ratio electrode by multiple printing. Screen printing is the straightforward technology to establish the electrodes in silicon solar cell fabrication. The several printed front electrodes with Ag paste on silicon wafer showed the significantly increased height and slightly widen finger. As a result, the resistance of the front electrode was decreased with multiple printing even if it slightly increased the shadowing loss. We showed the improved electrical characteristics for c-Si solar cell with repeatedly printed front electrode by 0.5%. It lays a foundation for high efficiency solar cell with high aspect ratio electrode using screen printing.
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