JP4121603B2 - SOLAR CELL, ITS MANUFACTURING METHOD, AND ITS CONNECTING METHOD - Google Patents

SOLAR CELL, ITS MANUFACTURING METHOD, AND ITS CONNECTING METHOD Download PDF

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JP4121603B2
JP4121603B2 JP06802398A JP6802398A JP4121603B2 JP 4121603 B2 JP4121603 B2 JP 4121603B2 JP 06802398 A JP06802398 A JP 06802398A JP 6802398 A JP6802398 A JP 6802398A JP 4121603 B2 JP4121603 B2 JP 4121603B2
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solar cell
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JPH11266029A (en
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諭 岡本
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Sharp Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

【０００１】
【発明の属する技術分野】
本発明は、結晶系シリコン半導体層を用いた太陽電池に関し、特に、太陽電池の変換効率の改善に関するものである。
【０００２】
【従来の技術】
第１導電型の半導体層としてｐ型の結晶シリコン基板を用い、第２導電型の半導体層としてｎ型不純物の拡散層を用い、光入射面にｐｎ接合を有する従来の高効率太陽電池の構造を図５に示す。
【０００３】
入射する太陽光を素子内部に有効に取り込むために、光入射面には反射防止膜５が形成されている。また、太陽電池の内部に取り込まれた太陽光がｎ型半導体層２、基板１で吸収されて発生するキャリアの損失を低減するために、ｎ型半導体層２の表面にパッシベーション膜４と、基板１と裏面電極７の間に基板よりも高濃度にｐ型のドーパントを含むｐ+型半導体層６が設けられている。
【０００４】
さらに、光入射面側のｎ型半導体層に接続さた入射面電極３は、ｎ型半導体層２から光発生電流を導出するための複数のグリッド電極部３２と、グリッド電極３２から電流を収集して太陽電池の外部に導出するための主電極部３１とから構成されている。さらに、この入射面電極３は、比抵抗値の小さい銀（Ａｇ）等の金属が用いられている。
【０００５】
一般に、太陽電池は、飽和電流が大きくなるほど開放電圧が小さくなり、光電変換特性が低下する。そこで、光電変換効率が高い太陽電池を得るために、発明者らは、受光面ｐｎ接合近傍での飽和電流を低減する方法について検討してきた。その結果、特開平７−３２６７８６号公報に開示されるように、入射面電極３に接続されたｎ型半導体層２の光入射面に占める割合を小さくすることによって、飽和電流を低減し、変換効率を改善できることを見出した。
【０００６】
【発明が解決しようとする課題】
さらに、詳しい検討の結果、ｐｎ接合の光が入射しない影領域において、飽和電流が大きいという問題があることが判った。すなわち、図５に示した従来の太陽電池においては、Ａｇ等の金属を主成分とする入射面電極３を形成しているが、この電極直下は影領域になっている。太陽電池の動作状態においては、ｐｎ接合を形成するｐ型とｎ型の半導体層の間には電位差が存在する。そして、影領域においてもｐｎ接合にこの電位差が印可されるため、光発生電流に対して逆方向の飽和電流が発生するという問題があった。
【０００７】
本発明は、このような問題点に鑑み、影領域における逆方向の飽和電流の発生を抑制し、変換効率の高い太陽電池を供給することを目的としている。
【０００８】
【課題を解決するための手段】
請求項１に記載の本発明は、第１導電型の半導体層の光入射面に、ｐｎ接合を形成する第２導電型の半導体層と、入射面電極等の太陽光を遮光する構成物が形成された太陽電池において、前記構成物により遮光された影領域の第１導電型の半導体層の光入射面の一部に、第２導電型の半導体層がなく絶縁体層が設けられており、絶縁体層の光入射面側と反対側の表面が第１導電型の半導体層と接している太陽電池を提供するものである。
【０００９】
すなわち、絶縁体層には、ｐｎ接合が存在しないため、第１導電型と第２導電型の半導体層間の電位差に起因する飽和電流を発生することが無く、変換効率を改善することができる。従来の太陽電池において、入射面電極の主電極部３１は、グリッド電極部３２から光発生電流を収集して太陽電池素子の外部に導出することを目的として形成される。すなわち、主電極部３１の直下にはｐｎ接合を形成する必要がないことから、本発明の太陽電池は、主電極部３１の直下を絶縁体層とすることにより、飽和電流の発生を招くこと無く、変換効率を改善することができる。
【００１０】
また、請求項２に記載の本発明は、前記影領域に形成する前述の絶縁体層が、第１導電型の半導体層の表面再結合を低減する性質を有するパッシベーション膜か、もしくは、パッシベーション膜とその他の絶縁材料との積層体である太陽電池を提供するものである。
【００１１】
すなわち、影領域において第１導電型の半導体層の表面は、パッシベーション膜で覆うことにより再結合による飽和電流が低減されて、より変換効率の高い太陽電池を得ることができる。
【００１２】
また、請求項３に記載の本発明は、入射面電極が、所定の方向に伸びる主電極部と、主電極部に接して主電極部と異なる方向に伸びるグリッド電極部とを有し、絶縁体層は主電極部の直下に位置して主電極部に沿って伸びており、絶縁体層の光入射面側の表面が主電極部と接している太陽電池である。また、請求項４に記載の本発明は、絶縁体層が第２導電型の半導体層に埋め込まれている太陽電池である。また、請求項５に記載の本発明は、第１導電型の半導体層の光入射面に第２導電型の半導体層を設ける第１の工程と、前記影領域の第２導電型の半導体層を除去する第２の工程と、前記影領域に絶縁体層を形成する第３の工程とを実施する太陽電池の製造方法を提供するものである。すなわち、この製造方法により、前述の太陽電池を製造することが可能となる。
【００１３】
また、請求項６に記載の本発明は、第２導電型の半導体層の上部にパッシベーション膜を形成する第５の工程と、入射面電極と第２導電型の半導体層とが接続される予定の領域のパッシベーション膜をエッチング除去した後に、入射面電極を形成する第４の工程とを有する請求項５に記載の太陽電池の製造方法において、前記第３の工程にて影領域に形成する絶縁体層としてパッシベーション膜のエッチング液のバリアとなる材料を用いる請求項５に記載の太陽電池の製造方法を提供するものである。
【００１４】
半導体層の表面再結合を抑制する効果を有して絶縁性の高い酸化シリコン膜等の絶縁体層を光入射面全面に形成した後に、リフトオフ法によりＡｇ等の蒸着金属を材料として入射面電極を形成する太陽電池を製造する場合に、この製造方法は有効である。すなわち、フォトレジストを入射面電極と第２導電型の半導体層とが接続される予定の領域を開口して形成した後に、エッチング液にて開口部のパッシベーション膜を除去する際に、フォトレジストにピンホール等が存在するとその部分のパッシベーション膜が開口されることになる。
【００１５】
特に、このピンホールによるパッシベーション膜の開口部が、第２導電型の半導体層が形成されない影領域に存在すると、その上にに形成される入射面電極と第１導電型の半導体層とが導通してリーク電流を生じ、太陽電池素子の変換効率を低下させることとなる。このピンホールの発生によるリーク電流の発生を防止する方法は、第２導電型の半導体層が形成されない影領域のパッシベーション膜の上部に、エッチング液のバリアとなる絶縁材料を形成することによって解決される。
【００１６】
従って、本発明の製造方法を用いることによって、半導体層の表面再結合を抑制する効果を有して絶縁性の高い酸化シリコン膜等の絶縁体層を光入射面全面に形成した後に、リフトオフ法によりＡｇ等の蒸着金属を材料として入射面電極を形成する作製する太陽電池の、影領域における特性劣化を低減して、変換効率を高めることができる。
【００１７】
また、請求項７に記載の本発明は、第１導電型の半導体層に接続された第１の電極と第２導電型の半導体層に接続された第２の電極とを有する太陽電池を複数接続する方法であって、太陽電池の光入射面上での接続を、ｐｎ接合を設けない領域で行う太陽電池の接続方法を提供するものである。
【００１８】
太陽電池素子の光入射面を遮光する物体は、入射面電極以外にも存在する。すなわち、表面を半田でめっきした銅等の配線材料や、隣接する太陽電池素子の光入射面に直接裏面電極を形成するような接続形態をとる太陽電池素子等がある。
【００１９】
従って、本発明の接続方法を用いることによって、影領域には光発生電流とは逆方向の電流を発生することがなく、変換効率が高い太陽電池を得ることができる。
【００２０】
【発明の実施の形態】
以下、本発明の各実施の形態を図面に従って説明する。なお、従来例と同一部分には同一符号を付す。
【００２１】
（実施の形態１）図１は、本発明の実施の形態１による太陽電池素子の概観図を示す。結晶シリコンからなるｐ型基板１の光入射面には、ｐｎ接合を形成するｎ型半導体層２が設けられて、入射面電極３のグリッド電極部３２がｎ型半導体層２に接続されている。また、複数のグリッド電極部３２に接続されて太陽光を遮光する入射面電極３の主電極部３１が形成されている。主電極３１が形成されてｎ型半導体層２が形成されないｐ型基板１の領域には、絶縁体層８が形成されている。さらに、ｎ型半導体層２はパッシベーション膜４および反射防止膜５に覆われている。ｐ型基板１の光入射面とは反対側の裏面には、ｐ型基板１よりもｐ型ドーパントの濃度が高いｐ+型半導体層６が形成され、ｐ+型半導体層６の裏面には裏面電極７が形成されている。
【００２２】
本実施の形態１の太陽電池の作製方法を図１および図２（ａ）〜（ｄ）を用いて説明する。図２（ａ）において、比抵抗値２Ωｃｍのｐ型ＣＺ基板１をＳＣ１、ＳＣ２の洗浄液によって洗浄し、熱拡散法により光入射面にリンをドーピングしてｎ型半導体層２を形成した。その後、熱酸化法により、ｎ型半導体層２の上部に酸化シリコン膜であるパッシベーション膜４を形成した。
【００２３】
図２（ｂ）において、後に遮光物が設けられる予定の光入射面の影領域２１を除く領域のパッシベーション膜４の上部に、フッ酸と硝酸の混合エッチング溶液（混酸）に対するレジスト層９を形成した。次に、混酸にて影領域２１のパッシベーション膜４とｎ型半導体層２を除去した。
【００２４】
図２（ｃ）において、レジスト層９を除去した後、常圧ＣＶＤ法により酸化チタン膜を堆積して、影領域２１の絶縁体層８を形成した。
【００２５】
図２（ｄ）において、アルミニウムペーストの印刷焼成によって裏面にｐ+型半導体層６を形成した後、塩酸によってアルミペーストの酸化物層と金属層とを除去した。更に、ｐ+型半導体層６の上部にＡｌの裏面電極７を形成した。
【００２６】
さらに、光入射面全面にフォトレジストを形成した後、入射面電極３が形成される予定の領域のフォトレジストを開口した。次に、フッ酸の水溶液を主成分とするエッチング液にて、フォトレジストの開口部のパッシベーション膜を開口した。さらに、Ｔｉ／Ｐｄ／Ａｇからなる金属材料を蒸着し、フォトレジストの上部の金属材料をリフトオフにより除去することによって入射面電極３を形成した。
【００２７】
最後に、常圧ＣＶＤ法により酸化チタン膜を堆積して、反射防止膜５を形成して、図１に示した本発明の太陽電池を完成した。
【００２８】
また、従来の太陽電池は、図１において光入射面の全面にｎ型半導体層を設けた構造で、その製造方法は、影領域２１のｎ型半導体層２のエッチング除去を行わなわずに、光入射面全面にｎ型半導体層２を形成した点を除いて、本発明の太陽電池と同じ構造とした。
【００２９】
表１のＡとＢに、本発明の図１に示した太陽電池の電流−電圧特性（Ａ）を、図５に示した従来の太陽電池の特性（Ｂ）と比較して示す。本発明の太陽電池は開放電圧および曲線因子が改善されて高い変換効率が得られた。すなわち、太陽電池の光入射面の遮光物により太陽光が入射しない影領域で、ｐｎ接合が設けられずに絶縁層を形成した太陽電池は、陰領域においてもｐｎ接合が形成された太陽電池よりも高い変換効率を示すことが確認された。
【００３０】
【表１】

Figure 0004121603
【００３１】
（実施の形態２）
本発明の実施の形態２による太陽電池は、図１に示した太陽電池の構造とほぼ同様であるが、影領域２１のｐ型基板１の表面に形成される絶縁体層８が、酸化シリコン膜であるパッシベーション膜で形成されている点が異なっている。
【００３２】
実施の形態２による太陽電池の作製方法は、実施の形態１で述べた太陽電池の製造方法において、パッシベーション膜の形成工程である熱酸化法による酸化シリコン膜の形成工程が、影領域２１のｎ型半導体層２を除去する工程の後になることが異なっており、他の工程は、実施の形態１と同様である。
【００３３】
尚、この作製方法においては、影領域２１の上部の絶縁体層８が酸化シリコン膜であるため、影領域２１の上部にピンホールが形成されないように、注意深くフォトレジストを形成することが重要である。
【００３４】
表１のＣに、本発明の太陽電池の電流−電圧特性を示す。前述の実施の形態１の太陽電池に比べて、更に開放電圧が向上して、素子の変換効率が改善された。すなわち、パッシベーション膜を影領域の絶縁体層として適用することにより、素子の変換効率を改善されることが確認された。
【００３５】
（実施の形態３）
本発明の実施の形態３による太陽電池は、図１に示した太陽電池の構造と同様であるが、影領域２１のｐ型基板１の表面に形成される絶縁体層８が、パッシベーション効果をもつ酸化シリコン膜と、フッ酸の水溶液を主成分とする酸化シリコン膜のエッチング液のバリアとなる酸化チタン膜の積層体で形成されている点が異なっている。
【００３６】
実施の形態３による太陽電池の作製方法は、実施の形態１で述べた太陽電池の製造方法において、パッシベーション膜の形成工程である熱酸化法による酸化シリコン膜の形成工程が、影領域２１のｎ型半導体層２を除去する工程の後になることが異なるだけで、他の工程は、実施の形態１と同様である。特に、影領域２１の上部の絶縁体層８が酸化シリコン膜および酸化チタン膜を順次積層した構造であるために、フォトレジストに多少のピンホールが存在しても、酸化チタン膜がエッチング液のバリアとなって絶縁膜層８を開口することが無い。従って、本発明の太陽電池は安定して高い変換効率が得られた。
【００３７】
（実施の形態４）
本発明の太陽電池素子の光入射面側のｐｎ接合を形成せずに絶縁体層８を設けた影領域において、複数の太陽電池素子を接続して太陽電池モジュールを作製した。モジュールは、３６枚の太陽電池を、図３に示したように、表面を半田でめっきした銅等の配線材料１０で入射面電極３と裏面電極７を接続する方法と、図４に示したように、隣接する太陽電池素子の光入射面電極３に直接裏面電極７を接続する方法とで、それぞれ作製した。一方、図５に示した従来の太陽電池でも同様のモジュールを作製した。その結果、いずれの接続形態においても、本発明の太陽電池を用いたモジュールの方が高い変換効率を示した。
【００３８】
以上、本発明の太陽電池は、第１導電型の半導体層としてｐ型結晶シリコン基板を用い、第２導電型の半導体層として熱拡散によりリンをドーパントとするｎ型半導体層を用いて説明したが、第１導電型をｎ型に、第２導電型をｐ型としても、一般的に知られた太陽電池素子の作製方法によって、本発明の効果を得ることができる。さらに、第１導電型の半導体層が結晶質の薄膜シリコンや化合物系半導体層であったり、第２導電型の半導体層が堆積法により形成されたものであっても、本発明の効果を得ることができる。
【００３９】
【発明の効果】
本発明の請求項１、３および４によれば、第１導電型の半導体層の光入射面に、ｐｎ接合を形成する第２導電型の半導体層と、入射面電極等の太陽光を遮光する構成物が形成された太陽電池において、第１導電型の半導体層の光入射面上の直接太陽光が入射しない影領域で、第２導電型の半導体層が設けられずに絶縁体層を設けることにより、影領域での光発生電流とは逆方向の電流を発することが無く、変換効率を改善することができる。
【００４０】
さらに、請求項２によれば、前記影領域に形成する前述の絶縁体層が、第１導電型の半導体層の表面再結合を低減する性質を有するパッシベーション膜か、もしくは、パッシベーション膜とその他の絶縁材料との積層体とすることにより、影領域において第１導電型の半導体層の表面は、再結合による飽和電流が低減されて、より変換効率の高い太陽電池を得ることができる。
【００４１】
さらに、請求項５によれば、第１導電型の半導体層の上部に第２導電型の半導体層を設ける第１の工程と、前記影領域の第２導電型の半導体層を除去する第２の工程と、前記影領域に絶縁体層を形成する第３の工程とを実施する製造方法により、前述の太陽電池を製造することが可能となる。
【００４２】
さらに、請求項６によれば、第２導電型の半導体層の上部にパッシベーション膜を形成する第５の工程と、入射面電極と第２導電型の半導体層とが接続される予定の領域のパッシベーション膜をエッチング除去した後に、入射面電極を形成する第４の工程とを有する請求項５に記載の太陽電池の製造方法において、前記第３の工程にて影領域に形成する絶縁体層としてパッシベーション膜のエッチング液のバリアとなる材料を用いる製造方法によって、リーク電流の発生を防ぎ、影領域における特性劣化を低減して、安定して変換効率が高い太陽電池を得ることができる。
【００４３】
また、請求項７によれば、第１導電型の半導体層に接続された第１の電極と第２導電型の半導体層に接続された第２の電極とを有する太陽電池を複数接続してモジュール等を形成する際に、光入射面上での接続を、ｐｎ接合を設けない領域で太陽電池の接続を行うことによって、影領域には光発生電流とは逆方向の電流を発生することがなく、変換効率が高い太陽電池を得ることができる。
【図面の簡単な説明】
【図１】本発明の太陽電池の概念図である。
【図２】本発明の太陽電池の作製プロセスを示す概念図である。
【図３】本発明の太陽電池を複数接続した形態を示す斜視図である。
【図４】本発明の太陽電池を複数接続した別の形態を示す斜視図である。
【図５】従来の太陽電池の概観図である。
【符号の説明】
１ ｐ型結晶シリコン基板
２ ｎ型半導体層
３ 入射面電極
４ パッシベーション膜
５ 反射防止膜
６ ｐ＋型半導体層
７ 裏面電極
８ 絶縁体層
９ レジスト層
１０ 配線材料
２１ 遮光物が設けられる予定の光入射面の影領域
３１ 入射面電極３の主電極部
３２ 入射面電極３のグリッド電極部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solar cell using a crystalline silicon semiconductor layer, and more particularly to improvement of conversion efficiency of a solar cell.
[0002]
[Prior art]
Structure of a conventional high-efficiency solar cell using a p-type crystalline silicon substrate as the first conductivity type semiconductor layer, using an n-type impurity diffusion layer as the second conductivity type semiconductor layer, and having a pn junction on the light incident surface Is shown in FIG.
[0003]
In order to effectively take incident sunlight into the device, an antireflection film 5 is formed on the light incident surface. Further, in order to reduce the loss of carriers generated when the sunlight taken into the solar cell is absorbed by the n-type semiconductor layer 2 and the substrate 1, a passivation film 4 and a substrate are formed on the surface of the n-type semiconductor layer 2. A p + -type semiconductor layer 6 containing a p-type dopant at a higher concentration than the substrate is provided between 1 and the back electrode 7.
[0004]
Further, the incident surface electrode 3 connected to the n-type semiconductor layer on the light incident surface side collects current from the grid electrodes 32 and a plurality of grid electrode portions 32 for deriving a photo-generated current from the n-type semiconductor layer 2. The main electrode portion 31 is led out to the outside of the solar cell. Further, the incident surface electrode 3 is made of a metal such as silver (Ag) having a small specific resistance value.
[0005]
In general, as the saturation current increases, the open voltage of the solar cell decreases and the photoelectric conversion characteristics deteriorate. Therefore, in order to obtain a solar cell with high photoelectric conversion efficiency, the inventors have studied a method for reducing the saturation current in the vicinity of the light-receiving surface pn junction. As a result, as disclosed in Japanese Patent Application Laid-Open No. 7-326786, the saturation current is reduced and the conversion is reduced by reducing the ratio of the n-type semiconductor layer 2 connected to the incident surface electrode 3 to the light incident surface. We found that efficiency can be improved.
[0006]
[Problems to be solved by the invention]
Further, as a result of detailed studies, it has been found that there is a problem that the saturation current is large in the shadow region where the light of the pn junction is not incident. That is, in the conventional solar cell shown in FIG. 5, the incident surface electrode 3 whose main component is a metal such as Ag is formed, but a shadow region is directly under this electrode. In the operating state of the solar cell, a potential difference exists between the p-type and n-type semiconductor layers forming the pn junction. Further, since this potential difference is applied to the pn junction even in the shadow region, there is a problem in that a saturation current in a direction opposite to the photogenerated current is generated.
[0007]
In view of such a problem, an object of the present invention is to suppress the generation of a reverse saturation current in a shadow region and to provide a solar cell with high conversion efficiency.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a second conductive type semiconductor layer that forms a pn junction on the light incident surface of the first conductive type semiconductor layer, and a component that blocks sunlight such as an incident surface electrode. In the formed solar cell, a part of the light incident surface of the first conductivity type semiconductor layer in the shadow region shielded from light by the component is provided with an insulator layer without the second conductivity type semiconductor layer. it is intended to provide a solar cell surface opposite to the light incidence surface side of the insulator layer that has contact with the first conductivity type semiconductor layer.
[0009]
That is, since there is no pn junction in the insulator layer , a saturation current due to a potential difference between the first conductive type and the second conductive type semiconductor layer is not generated, and the conversion efficiency can be improved. In the conventional solar cell, the main electrode portion 31 of the incident surface electrode is formed for the purpose of collecting the photogenerated current from the grid electrode portion 32 and leading it out of the solar cell element. That is, since it is not necessary to form a pn junction immediately below the main electrode portion 31 , the solar cell of the present invention causes the generation of a saturation current by using an insulator layer immediately below the main electrode portion 31. And conversion efficiency can be improved.
[0010]
According to a second aspect of the present invention, the insulator layer formed in the shadow region is a passivation film having a property of reducing surface recombination of the first conductivity type semiconductor layer, or a passivation film. The solar cell which is a laminated body of and other insulating materials is provided.
[0011]
That is, the surface of the first conductivity type semiconductor layer in the shadow region is covered with a passivation film, so that saturation current due to recombination is reduced, and a solar cell with higher conversion efficiency can be obtained.
[0012]
According to a third aspect of the present invention, the incident surface electrode has a main electrode portion extending in a predetermined direction and a grid electrode portion in contact with the main electrode portion and extending in a direction different from the main electrode portion, and is insulated. The body layer is a solar cell that is located immediately below the main electrode portion and extends along the main electrode portion, and the surface on the light incident surface side of the insulator layer is in contact with the main electrode portion. The present invention according to claim 4 is a solar cell in which an insulator layer is embedded in a semiconductor layer of the second conductivity type. According to a fifth aspect of the present invention, there is provided the first step of providing a second conductive type semiconductor layer on the light incident surface of the first conductive type semiconductor layer, and the second conductive type semiconductor layer in the shadow region. The manufacturing method of the solar cell which implements the 2nd process which removes, and the 3rd process which forms an insulator layer in the said shadow area | region is provided. In other words, the above-described solar cell can be manufactured by this manufacturing method.
[0013]
According to a sixth aspect of the present invention, the fifth step of forming a passivation film on the second conductive type semiconductor layer is connected to the incident surface electrode and the second conductive type semiconductor layer. A method for manufacturing a solar cell according to claim 5 , further comprising: a fourth step of forming an incident surface electrode after removing the passivation film in the region of the insulating film, and forming the insulation in the shadow region in the third step. The method for manufacturing a solar cell according to claim 5 , wherein a material serving as a barrier for an etching solution for a passivation film is used as the body layer.
[0014]
After an insulator layer such as a highly insulating silicon oxide film having the effect of suppressing the surface recombination of the semiconductor layer is formed on the entire surface of the light incident surface, the incident surface electrode is made of a deposited metal such as Ag by a lift-off method. This manufacturing method is effective when manufacturing a solar cell that forms a film. That is, after the photoresist is formed by opening the region where the incident surface electrode and the second conductivity type semiconductor layer are to be connected, the photoresist is removed when the passivation film in the opening is removed with an etching solution. If a pinhole or the like is present, the passivation film in that portion is opened.
[0015]
In particular, if the opening of the passivation film by the pinhole exists in a shadow region where the second conductive type semiconductor layer is not formed, the incident surface electrode formed thereon and the first conductive type semiconductor layer are electrically connected. As a result, a leakage current is generated and the conversion efficiency of the solar cell element is lowered. This method of preventing the occurrence of leak current due to the occurrence of pinholes can be solved by forming an insulating material serving as an etchant barrier over the passivation film in the shadow region where the second conductivity type semiconductor layer is not formed. The
[0016]
Therefore, by using the manufacturing method of the present invention, a lift-off method is performed after an insulator layer such as a highly insulating silicon oxide film having an effect of suppressing surface recombination of the semiconductor layer is formed on the entire light incident surface. Thus, it is possible to reduce the deterioration of characteristics in the shadow region of the solar cell to be formed using the deposited metal such as Ag as the material and form the incident surface electrode, and to increase the conversion efficiency.
[0017]
According to a seventh aspect of the present invention, a plurality of solar cells having a first electrode connected to the first conductive type semiconductor layer and a second electrode connected to the second conductive type semiconductor layer are provided. It is a method of connection, and provides a solar cell connection method in which the connection on the light incident surface of the solar cell is performed in a region where no pn junction is provided.
[0018]
An object that blocks the light incident surface of the solar cell element is present in addition to the incident surface electrode. That is, there are a wiring material such as copper whose surface is plated with solder, a solar cell element having a connection form in which a back electrode is directly formed on a light incident surface of an adjacent solar cell element.
[0019]
Therefore, by using the connection method of the present invention, a solar cell with high conversion efficiency can be obtained without generating a current in the opposite direction to the photogenerated current in the shadow region.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same part as a prior art example.
[0021]
(Embodiment 1) FIG. 1 shows an overview of a solar cell element according to Embodiment 1 of the present invention. An n-type semiconductor layer 2 forming a pn junction is provided on the light incident surface of the p-type substrate 1 made of crystalline silicon, and the grid electrode portion 32 of the incident surface electrode 3 is connected to the n-type semiconductor layer 2. . Further, the main electrode portion 31 of the incident surface electrode 3 that is connected to the plurality of grid electrode portions 32 and shields sunlight is formed. An insulator layer 8 is formed in a region of the p-type substrate 1 where the main electrode 31 is formed and the n-type semiconductor layer 2 is not formed. Further, the n-type semiconductor layer 2 is covered with a passivation film 4 and an antireflection film 5. A p + -type semiconductor layer 6 having a higher p-type dopant concentration than the p-type substrate 1 is formed on the back surface opposite to the light incident surface of the p-type substrate 1. A back electrode 7 is formed.
[0022]
A method for manufacturing the solar cell according to the first embodiment will be described with reference to FIGS. 1 and 2A to 2D. In FIG. 2A, the p-type CZ substrate 1 having a specific resistance value of 2 Ωcm was cleaned with SC1 and SC2 cleaning liquids, and phosphorus was doped on the light incident surface by a thermal diffusion method to form an n-type semiconductor layer 2. Thereafter, a passivation film 4 that is a silicon oxide film was formed on the n-type semiconductor layer 2 by thermal oxidation.
[0023]
In FIG. 2B, a resist layer 9 for a mixed etching solution of hydrofluoric acid and nitric acid (mixed acid) is formed on the passivation film 4 in a region excluding the shadow region 21 on the light incident surface where a light shielding object is to be provided later. did. Next, the passivation film 4 and the n-type semiconductor layer 2 in the shadow region 21 were removed with a mixed acid.
[0024]
In FIG. 2C, after removing the resist layer 9, a titanium oxide film was deposited by an atmospheric pressure CVD method to form the insulator layer 8 in the shadow region 21.
[0025]
In FIG. 2D, after the p + -type semiconductor layer 6 was formed on the back surface by printing and baking the aluminum paste, the oxide layer and the metal layer of the aluminum paste were removed with hydrochloric acid. Further, an Al back electrode 7 was formed on the p + type semiconductor layer 6.
[0026]
Further, after forming a photoresist on the entire surface of the light incident surface, the photoresist in the region where the incident surface electrode 3 is to be formed was opened. Next, the passivation film in the opening of the photoresist was opened with an etching solution mainly containing an aqueous solution of hydrofluoric acid. Furthermore, a metal material made of Ti / Pd / Ag was vapor-deposited, and the metal material on the top of the photoresist was removed by lift-off to form the incident surface electrode 3.
[0027]
Finally, a titanium oxide film was deposited by an atmospheric pressure CVD method to form an antireflection film 5, thereby completing the solar cell of the present invention shown in FIG.
[0028]
In addition, the conventional solar cell has a structure in which an n-type semiconductor layer is provided on the entire surface of the light incident surface in FIG. 1, and the manufacturing method thereof does not perform etching removal of the n-type semiconductor layer 2 in the shadow region 21. The structure is the same as that of the solar cell of the present invention except that the n-type semiconductor layer 2 is formed on the entire light incident surface.
[0029]
Tables A and B show the current-voltage characteristics (A) of the solar cell shown in FIG. 1 of the present invention in comparison with the characteristics (B) of the conventional solar cell shown in FIG. In the solar cell of the present invention, the open circuit voltage and the fill factor were improved, and high conversion efficiency was obtained. That is, a solar cell in which an insulating layer is formed without a pn junction in a shadow region where sunlight does not enter due to a light shielding surface on the light incident surface of the solar cell is more than a solar cell in which a pn junction is formed in a shadow region. It was also confirmed that the high conversion efficiency was exhibited.
[0030]
[Table 1]
Figure 0004121603
[0031]
(Embodiment 2)
The solar cell according to Embodiment 2 of the present invention has substantially the same structure as that of the solar cell shown in FIG. 1, except that the insulator layer 8 formed on the surface of the p-type substrate 1 in the shadow region 21 is made of silicon oxide. The difference is that the film is formed of a passivation film.
[0032]
The method for manufacturing a solar cell according to the second embodiment is the same as the method for manufacturing a solar cell described in the first embodiment, in which the formation process of the silicon oxide film by the thermal oxidation method, which is the formation process of the passivation film, The difference is that after the step of removing type semiconductor layer 2, the other steps are the same as in the first embodiment.
[0033]
In this manufacturing method, since the insulator layer 8 above the shadow region 21 is a silicon oxide film, it is important to carefully form a photoresist so that no pinhole is formed above the shadow region 21. is there.
[0034]
C in Table 1 shows the current-voltage characteristics of the solar cell of the present invention. Compared with the solar cell of Embodiment 1 described above, the open circuit voltage was further improved, and the conversion efficiency of the device was improved. That is, it was confirmed that the conversion efficiency of the element can be improved by applying the passivation film as the insulator layer in the shadow region.
[0035]
(Embodiment 3)
The solar cell according to Embodiment 3 of the present invention has the same structure as that of the solar cell shown in FIG. 1, but the insulator layer 8 formed on the surface of the p-type substrate 1 in the shadow region 21 has a passivation effect. The silicon oxide film is different from the silicon oxide film that is formed by a laminated body of a titanium oxide film that serves as a barrier for an etching solution of a silicon oxide film containing a hydrofluoric acid aqueous solution as a main component.
[0036]
The method for manufacturing a solar cell according to Embodiment 3 is the same as the method for manufacturing a solar cell described in Embodiment 1, except that the formation process of the silicon oxide film by the thermal oxidation method, which is a passivation film formation process, The other steps are the same as those in the first embodiment except that the steps after the step of removing the mold semiconductor layer 2 are different. In particular, since the insulator layer 8 above the shadow region 21 has a structure in which a silicon oxide film and a titanium oxide film are sequentially laminated, the titanium oxide film can be used as an etching solution even if some pinholes exist in the photoresist. The insulating film layer 8 is not opened as a barrier. Therefore, the solar cell of the present invention stably obtained high conversion efficiency.
[0037]
(Embodiment 4)
A solar cell module was manufactured by connecting a plurality of solar cell elements in a shadow region where the insulator layer 8 was provided without forming a pn junction on the light incident surface side of the solar cell element of the present invention. As shown in FIG. 3, the module is composed of 36 solar cells, as shown in FIG. 3, and a method of connecting the incident surface electrode 3 and the back electrode 7 with a wiring material 10 such as copper whose surface is plated with solder. Thus, each was manufactured with the method of connecting the back surface electrode 7 directly to the light-incidence surface electrode 3 of an adjacent solar cell element. On the other hand, the same module was produced also in the conventional solar cell shown in FIG. As a result, in any connection form, the module using the solar cell of the present invention showed higher conversion efficiency.
[0038]
As described above, the solar cell of the present invention has been described using the p-type crystalline silicon substrate as the first conductive type semiconductor layer and the n-type semiconductor layer using phosphorus as a dopant by thermal diffusion as the second conductive type semiconductor layer. However, even if the first conductivity type is n-type and the second conductivity type is p-type, the effects of the present invention can be obtained by a generally known method for manufacturing a solar cell element. Furthermore, even if the first conductive type semiconductor layer is a crystalline thin film silicon or a compound semiconductor layer, or the second conductive type semiconductor layer is formed by a deposition method, the effects of the present invention can be obtained. be able to.
[0039]
【The invention's effect】
According to the first , third and fourth aspects of the present invention, the second conductive type semiconductor layer forming a pn junction on the light incident surface of the first conductive type semiconductor layer and the sunlight of the incident surface electrode and the like are shielded from light. In the solar cell in which the structure to be formed is formed, the insulator layer is formed in the shadow region where the direct sunlight is not incident on the light incident surface of the first conductivity type semiconductor layer without the second conductivity type semiconductor layer being provided. By providing, it is possible to improve the conversion efficiency without generating a current in the opposite direction to the light generation current in the shadow region.
[0040]
Furthermore, according to claim 2, the insulator layer formed in the shadow region is a passivation film having a property of reducing the surface recombination of the first conductivity type semiconductor layer, or the passivation film and the other film. By using a stacked body with an insulating material, the surface of the first conductivity type semiconductor layer in the shadow region is reduced in saturation current due to recombination, and a solar cell with higher conversion efficiency can be obtained.
[0041]
Further, according to claim 5 , a first step of providing a second conductivity type semiconductor layer on the first conductivity type semiconductor layer, and a second step of removing the second conductivity type semiconductor layer in the shadow region. The above-described solar cell can be manufactured by the manufacturing method in which the step and the third step of forming the insulator layer in the shadow region are performed.
[0042]
Furthermore, according to claim 6 , a fifth step of forming a passivation film on the second conductivity type semiconductor layer, and a region where the incident surface electrode and the second conductivity type semiconductor layer are to be connected are provided. The method for manufacturing a solar cell according to claim 5 , further comprising: a fourth step of forming an incident surface electrode after removing the passivation film by etching as an insulator layer formed in the shadow region in the third step. By a manufacturing method using a material that serves as a barrier for the etchant of the passivation film, it is possible to prevent the occurrence of leakage current, reduce characteristic deterioration in the shadow region, and stably obtain a solar cell with high conversion efficiency.
[0043]
According to claim 7 , a plurality of solar cells having a first electrode connected to the first conductivity type semiconductor layer and a second electrode connected to the second conductivity type semiconductor layer are connected. When a module or the like is formed, a current in the opposite direction to the light generation current is generated in the shadow region by connecting the solar cell in the region where the pn junction is not provided for connection on the light incident surface. Thus, a solar cell with high conversion efficiency can be obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a solar cell of the present invention.
FIG. 2 is a conceptual diagram showing a manufacturing process of the solar cell of the present invention.
FIG. 3 is a perspective view showing a configuration in which a plurality of solar cells of the present invention are connected.
FIG. 4 is a perspective view showing another embodiment in which a plurality of solar cells of the present invention are connected.
FIG. 5 is an overview of a conventional solar cell.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 p-type crystalline silicon substrate 2 n-type semiconductor layer 3 Incident surface electrode 4 Passivation film 5 Antireflection film 6 P + type semiconductor layer 7 Back surface electrode 8 Insulator layer 9 Resist layer 10 Wiring material 21 Light incident on which a light-shielding material is to be provided Surface shadow region 31 Main electrode portion 32 of incident surface electrode 3 Grid electrode portion of incident surface electrode 3

Claims (7)

第１導電型の半導体層の光入射面に、ｐｎ接合を形成する第２導電型の半導体層と、入射面電極等の太陽光を遮光する構成物が形成された太陽電池において、前記構成物により遮光された影領域の第１導電型の半導体層の光入射面の一部に、第２導電型の半導体層がなく絶縁体層が設けられており、前記絶縁体層の光入射面側と反対側の表面が第１導電型の半導体層と接していることを特徴とする太陽電池。A solar cell in which a light-conducting surface of a first-conductivity-type semiconductor layer is provided with a second-conductivity-type semiconductor layer that forms a pn junction and a composition that shields sunlight, such as an incident-surface electrode. A part of the light incident surface of the first conductivity type semiconductor layer in the shadow region shielded by the light is provided with an insulator layer without the second conductivity type semiconductor layer , and the light incident surface side of the insulator layer solar cell characterized by Rukoto the opposite surface is not in contact with the first conductivity type semiconductor layer and the. 前記絶縁体層が、半導体層の表面再結合を低減する性質を有するパッシベーション膜か、もしくは、パッシベーション膜と他の絶縁材料との積層体であることを特徴とする請求項１に記載の太陽電池。Before Kize' edge layer is a passivation film or has a property to reduce surface recombination of the semiconductor layer, or, according to claim 1, which is a laminate of a passivation film and another insulating material Solar cell. 前記入射面電極は、所定の方向に伸びる主電極部と、前記主電極部に接して前記主電極部と異なる方向に伸びるグリッド電極部とを有し、The incident surface electrode has a main electrode portion extending in a predetermined direction and a grid electrode portion in contact with the main electrode portion and extending in a direction different from the main electrode portion,
前記絶縁体層は前記主電極部の直下に位置して前記主電極部に沿って伸びており、The insulator layer is located directly below the main electrode portion and extends along the main electrode portion;
前記絶縁体層の光入射面側の表面が前記主電極部と接していることを特徴とする請求項１または２に記載の太陽電池。The solar cell according to claim 1, wherein a surface of the insulator layer on a light incident surface side is in contact with the main electrode portion. 前記絶縁体層が前記第２導電型の半導体層に埋め込まれていることを特徴とする、請求項１から３のいずれかに記載の太陽電池。The solar cell according to claim 1, wherein the insulator layer is embedded in the semiconductor layer of the second conductivity type. 第１導電型の半導体層の光入射面に第２導電型の半導体層を設ける第１の工程と、前記影領域の第２導電型の半導体層を除去する第２の工程と、前記影領域に絶縁体層を形成する第３の工程と、入射面電極を形成する第４の工程とを実施することを特徴とする請求項１から４のいずれかに記載の太陽電池の製造方法。A first step of providing a second conductivity type semiconductor layer on a light incident surface of the first conductivity type semiconductor layer; a second step of removing the second conductivity type semiconductor layer of the shadow region; and the shadow region. The method for manufacturing a solar cell according to any one of claims 1 to 4, wherein a third step of forming an insulator layer on the substrate and a fourth step of forming an incident surface electrode are performed. 第２導電型の半導体層の上部にパッシベーション膜を形成する第５の工程と、入射面電極と第２導電型の半導体層とが接続される予定の領域のパッシベーション膜をエッチング除去した後に、入射面電極を形成する第４の工程とを有する請求項５に記載の太陽電池の製造方法において、前記第３の工程にて影領域に形成する絶縁体層としてパッシベーション膜のエッチング液のバリアとなる材料を用いることを特徴とする請求項５に記載の太陽電池の製造方法。After the fifth step of forming a passivation film on the second conductive type semiconductor layer and etching removal of the passivation film in the region where the incident surface electrode and the second conductive type semiconductor layer are to be connected, 6. The method of manufacturing a solar cell according to claim 5 , further comprising a fourth step of forming a surface electrode, which serves as a barrier for an etching solution for a passivation film as an insulator layer formed in the shadow region in the third step. The method of manufacturing a solar cell according to claim 5 , wherein a material is used. 第１導電型の半導体層に接続された第１の電極と第２導電型の半導体層に接続された第２の電極とを有する太陽電池を複数接続する方法であって、前記太陽電池の光入射面上での接続を、ｐｎ接合を設けない領域で行うことを特徴とする請求項１から４のいずれかに記載の太陽電池の接続方法。A method of connecting a plurality of solar cells having a first electrode connected to a first conductivity type semiconductor layer and a second electrode connected to a second conductivity type semiconductor layer, the light of the solar cell connections on the entrance surface, a method of connecting solar cell according to any one of claims 1 to 4, characterized in that in the region not provided with the pn junction.
JP06802398A 1998-03-18 1998-03-18 SOLAR CELL, ITS MANUFACTURING METHOD, AND ITS CONNECTING METHOD Expired - Fee Related JP4121603B2 (en)

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