Process Development of Electrodeposition of High-purity Si Films using Ionic Liquid based on Molecular-level Analyses of the Reaction Pathway

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15301
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26030:Composite materials and interfaces-related
• Research Institution: Waseda University
• Principal Investigator: Kunimoto Masahiro 早稲田大学, 理工学術院, 講師(任期付) (60619237)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 電析プロセス / 量子化学計算 / 表面増強ラマン散乱分光法 / 太陽電池級Si / イオン液体

Outline of Final Research Achievements

This study aimed to develop an efficient electrochemical deposition process to fabricate Si thin film with high purity and with highly smooth surface, on the basis of mechanistic understandings from theoretical and spectroscopic analyses. Here ionic liquid of TMHATFSI was used as electrolyte. Theoretical calculation results and surface enhanced Raman measurement spectra revealed that SiCl4 as a precursor of electrodeposited Si hardly form chemical bonds with Si substrates immediately after the electron acceptance, but it shows first the formation of dimer or even polymer of Si as intermediates. More detailed investigation for electronic structure of those species suggested that it is due to dispersed orbitals of Si and strong electronegativity of Cl. On this basis, the waveform of applied potential on the working electrode substrate was optimized to obtain electrodeposited Si thin film with the highest purity and the smoothest surface ever reported.

Free Research Field

界面化学，電気化学

Academic Significance and Societal Importance of the Research Achievements

本研究が確立を企図した反応プロセスは、高純度のSi層を形成するための電解工程であり、形成されるSi層は将来的に太陽光発電デバイス用Si媒体のための原料素材としての利用が期待される。大面積一括形成性に優れる電析法を利用してこのような材料媒体が形成可能となることによって、今後世界規模で増々需要が高まると予想されるSi太陽電池の安定供給が実現され、再生可能エネルギーを根幹とする次世代電力系統の構築・運用に大きく貢献できる。また本研究では独自の計測システムに基づく表面増強ラマン散乱分光計測と理論計算解析を併用した反応解析を特徴としており、学術的価値の高い電子状態レベルからの反応機構解明も期待された。