High purity silicon materials prepared through wet-chemical and electrochemical approaches

Takayuki Homma, Nobufumi Matsuo, Xiao Yang, Kouji Yasuda, Yasuhiro Fukunaka, Toshiyuki Nohira

Research output: Contribution to journalReview article

12 Citations (Scopus)

Abstract

A new approach to produce high purity solar grade silicon (SOG-Si) using wet-chemical and electrochemical processes was proposed. First, diatomaceous earth was used as a source of silica and wet-chemical purification by acid leaching and solvent extraction processes were applied for eliminating heavy metal and light element such as boron, respectively. In particular, the solvent extraction using channel flow reactor demonstrated extremely high efficiency for eliminating boron to 7N (99.99999%) level purity. Secondly, the high-purity silica was reduced to silicon by the direct electrolysis method using molten CaCl2 as an electrolyte and Si plate as cathode. We proposed the continuous electrolysis system by feeding silica granules to the Si cathode set at the bottom of the cell. It was confirmed that the reduction proceeded steadily to form crystalline Si with a sufficient reduction rate. We also attempted electrodeposition of Si films and have developed a process using KF-KCl + K2SiF6 molten salt, from which uniform layer of Si with a thickness larger than 100 μm could be formed.

Original languageEnglish
Pages (from-to)512-518
Number of pages7
JournalElectrochimica Acta
Volume179
DOIs
Publication statusPublished - 2015 Oct 10

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Electrochemistry

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