2016-Sustainable Industrial Processing Summit
SIPS 2016 Volume 9: Molten Salts and Ionic Liquids, Energy Production
| Editors: | Kongoli F, Gaune-Escard M, Turna T, Mauntz M, Dodds H.L. |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2016 |
| Pages: | 390 pages |
| ISBN: | 978-1-987820-24-9 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Electrochemical Behaviour and Electrodeposition of Silicon onto Graphite from Halide and Halide-Oxide Melts
Dmytro Shakhnin1; Liliia Molotovska1; Viktor Malyshev2; Alla Sushchenko1; Marcelle Gaune-Escard3;1V.I. VERNADSKY INSTITUTE OF GENERAL AND INORGANIC CHEMISTRY OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE, Kyiv, Ukraine; 2IGIC NASU, Kyiv, Ukraine; 3AIX-MARSEILLE UNIVERSITé/POLYTECH, CNRS/IUSTI UMR7343, Marseille, France;
Type of Paper: Regular
Id Paper: 202
Topic: 13
Abstract:
The aim of the present study is electrodeposition of high-purity silicon onto graphite substrate as adherent coating and investigation of deposit morphology depending on the conditions of electrodeposition. Methods: cyclic voltammetry, potentio- and galvanostatic electrolysis, X-ray phase analysis, optical and scanning electron microscopy. For continuous silicon coating obtaining, K2SiF6 concentration was maintained within 8-14 mol% range at a constant potential. Electrodeposition was carried out at potential -0,75±0,05 V versus Pt or Ag reference electrode. Current strength varied within 10-100 mA/cm2 range. During the deposition, uniform continuous silica deposits were obtained. Silicon coatings containing grains of wedge shape up to 1 mm thick were obtained with the duration of electrolysis 5-6 hours. Electrodeposited silicon was easily separatable from the graphite base. The cross-section of deposits indicates nodular or dendritic growth up to a few millimeters on the surface of the main adherent layer of silicon. The grain size was about 250 nm. Larger grains (up to 750 nm in diameter) were formed with the electrolysis duration more than 5-6 hours. X-ray phase analysis shows only the polycrystalline silicon presence in the deposit. In addition, the electronic microprobe studies and analysis of X-rays scattering energy have revealed no impurities. However, levels of Li, Cr, Ni, Fe, Cu, Ag, Mn, Pb, and Al impurities up to 0.02% were detected by emission spectral analysis. The most common impurities are Cu, Fe, Ni, and Ag, but the overall level of their concentrations cannot impact significantly the performance of solar cells. Deposits purity degree was in general over 99.99%. Four-probe measurement method showed differences in specific resistivity at different places of electrodeposited silicon. At room temperature, experimental resistance values for silicon electrodeposited from this system was always greater than 1 ohm•cm.<br />Keywords: silicon, coating, electrodeposition, fluoride melt.
Keywords:
Silicon for the Chemical and Solar Industry;References:
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