成果報告書詳細
管理番号20090000000290
タイトル*平成20年度中間年報 新エネルギー技術研究開発 太陽光発電システム未来技術研究開発 未来型超薄型多結晶シリコン太陽電池の研究開発
公開日2009/8/21
報告書年度2008 - 2008
委託先名三菱電機株式会社
プロジェクト番号P07015
部署名新エネルギー技術開発部 太陽電池グループ
和文要約以下本編抜粋:1. 研究開発の内容及び成果等 平成20年度末に、基板厚さ100μm、面積15cm角相当の多結晶シリコンセルにおいて変換効率18%を実現するために、共同研究機関の東京工業大学と連携して以下の研究開発を行う。 1)多結晶シリコンの超薄型放電スライシング技術の開発 基板厚さ100μm、カーフロス150μm以下を目指して、放電加工を用いたシリコン基板スライス技術を開発する。 2)超薄型多結晶シリコンセル製造技術の開発 超薄型セルの製造技術開発として、低反射テクスチャー構造、裏面ポイントコンタクト構造、およびパッシベーション技術の研究開発を行う。 3) デンドライト多結晶シリコン基板の評価 平成20年度に東北大から提供された基板を用いて、標準的なプロセスによるセル試作を行い、一般的な多結晶シリコン基板との比較検討を行う。必要に応じて、ライフタイム測定、不純物分析等を実施し、セル試作結果と併せて、デンドライト多結晶シリコン基板に対する評価を行う。
英文要約Next Generation PV Systems Title: Next generation ultra-thin multi-crystalline silicon solar cells (Electrical discharge slicing & Cell process) (FY2006-FY2009) FY2008 Annual Report 2. Development of ultra-thin multi-crystalline silicon solar cells for higher efficiency For a process compatible with conventional process, laser process for texturing and a low bowing paste for rear electrodes was utilized for fabricating 100-um-thick multi-crystalline solar cells of about 15 cm square size. A low light-reflection surface was achieved by honeycomb structured texture fabricated by wet etching of silicon through laser openings of SiN mask with a mixture of nitric acid and hydrofluoric acid. As the result, a conversion efficiency of 17.4% (measured by AIST) was achieved for a 100-um-thick solar cell with highly compatible process with conventional process.  For further improvement, point contact structure combined with the honeycomb structured texture was successfully developed. By applying the structure to a ultra-thin wafer, a conversion efficiency of 18.0% (evaluation by Mitsubishi Electric) for 100-um-thick multi-crystalline silicon solar cell in nearly an industrial-size of 15 x 15 cm was achieved. For thicker multi-crystalline silicon solar cell, conversion efficiency of 18.9% (evaluation by Mitsubishi Electric) in nearly an industrial-size of 15 x 15 cm was achieved. This established a new world record conversion efficiency for about 15 cm square size multi-crystalline solar cell. For speeding up the laser patterning process, holographic optical element (HOE), a kind of grating designed for diffracting incident light into a desired pattern, was optimized for the design of solar cells. As the result, number of simultaneous pattering points has improved. This contributes a large reduction of laser processing time from last year. 3. Characterization of multi-crystalline silicon wafer made by dendritic growth Solar cells were fabricated through standard process with multi-crystalline silicon wafers grown by dendritic growth and conventional growth for comparing the electric characteristics dependence on the positions of ingots. As the result, solar cells utilizing dendritic growth showed high open circuit voltage of above 630 mV in a wide range of an ingot. This indicated good crystalline-quality for the ingot grown by dendritic growth. For the first trial utilizing dendritic growth toward higher efficiency, honeycomb structured texture and conventional aluminum electrode for the rear was utilized. As the result, 17.8% was achieved for a 280-um-thick solar cell in 10 cm square size. Higher efficiency would be possible if rear surface were passivated because the aluminum electrode on the rear underutilizes the nature of the wafers.
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