nanostructuring on semiconductor surface for optical management by high-pressure hydrogen plasma

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02049
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 18020:Manufacturing and production engineering-related
• Research Institution: Osaka University
• Principal Investigator: Ohmi Hiromasa 大阪大学, 大学院工学研究科, 准教授 (00335382)
• Co-Investigator(Kenkyū-buntansha): 安武 潔 大阪大学, 工学研究科, 教授 (80166503)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 水素 / プラズマ / Si / 特殊加工 / 表面処理 / 反射率制御

Outline of Final Research Achievements

In this study, in order to reduce the light reflection loss of thin crystalline silicon solar cells, we aimed to develop a process for forming a light anti-reflection nanostructure on the Si surface using inexpensive and non-toxic hydrogen plasma. A study on the mechanism of why an anti-reflective surface can be formed by medium-pressure hydrogen plasma was conducted. It was found that the incidence of positive ions is important for nanocone formation, that nanocone structures are not formed in a pure hydrogen atmosphere, and that an oxynitride film acting as a micromask material is required. Furthermore, the height of the obtained nanocones reached 6 um at the maximum, and their absolute optical reflectance was below 1% over a wide wavelength range from 350 nm to 1040 nm, realizing low reflectance over an extremely broad band.

Free Research Field

材料科学

Academic Significance and Societal Importance of the Research Achievements

近年、爆発的な太陽電池普及の主役は、結晶シリコン（Si）太陽電池がになっているが、バルク型結晶Siの形成には、精製や結晶化、さらにはウエハ化の過程で、多大なエネルギー消費と多くの材料ロスが不可欠となっている。本研究の成果は、光吸収係数が良好とは言えない間接遷移型Siについて、現状の太陽電池の変換効率を維持しつつ、Si使用量の低減に繋がる薄型化に貢献する。その加工過程において必要なガスは廉価・無毒な水素ガスのみであり、従来の地球温暖化ガスを用いた手法や毒性・高価な化学薬品を用いた手法に比べ、環境に優しい加工法を開発した。また、広波長域に対する黒体構造の創成は、黒体輻射制御研究の促進に貢献できる。