Conductivity control of semiconducting silicides by composition ratios and formation of homojunction solar cells on glass substrates

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H03767
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 21:Electrical and electronic engineering and related fields
• Research Institution: University of Tsukuba
• Principal Investigator: Suemasu Takashi 筑波大学, 数理物質系, 教授 (40282339)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 太陽電池 / 光吸収 / pn接合 / エネルギー変換効率 / 欠陥 / 空孔

Outline of Final Research Achievements

Barium disilicide (BaSi2) is one of the emerging materials for solar cell applications. It has a large absorption coefficient and a suitable band gap of 1.3 eV. In the past, p-BaSi2/n-Si heterojunction solar cells have been achieved. However, photons absorbed in the n-Si side contribute mostly to photocurrents. In this work, we achieved the first demonstration of BaSi2-pn homojunction solar cells and n-ZnO/p-BaSi2 heterojunction solar cells, wherein photogenerated carriers in the BaSi2 layers contribute mostly to the photocurrent.
We have also investigated defects in BaSi2 films. According to first-principles calculations, Si vacancies are most likely to form. We found by experiment that these defects are inactivated by atomic hydrogen doping, and the mechanism of inactivations is clarified based on first-principles studies. We further developed the BaSi2 thin-film growth technique by sputtering, and demonstrated the first operation of n-BaSi2/p-Si solar cells.

Free Research Field

電子工学、結晶成長工学

Academic Significance and Societal Importance of the Research Achievements

半導体バリウムシリサイド(BaSi2)は資源が豊富な元素で構成され、光吸収係数および禁制帯幅の視点で、太陽電池に適した新しい材料である。本研究において、BaSi2ホモ接合太陽電池の動作に成功したことは、既存の結晶Si太陽電池とのタンデム化により、資源が豊富な元素のみで構成されるSiベースの半導体においても、エネルギー変換効率30%超を狙える可能性が拓けるため、意義深いといえる。また、大面積薄膜の堆積に適したスパッタ法を用いて太陽電池動作を実証したことも重要な成果である。学術的には、BaSi2中の空孔型欠陥を水素で不活性化できること、また、その機構を明らかにした点に意義がある。