JP3721620B2 - Parallel integrated solar cell - Google Patents

Description

【００３６】
このように、ボトムｉ層９ｉの膜厚が厚いほど、変換効率が高くなっている。これは短絡電流が増加していることから、ボトムｉ層９ｉが厚いほど透過光が減少し、より長波長光の感度が高くなる為と考えられる。
【００３７】
さらに、実施例１および２の太陽電池の各層厚を変化させ、ＡＭ１．５，１００ｍＷ／ｃｍ² 、２５℃での電気特性を測定し、表２にその測定結果を掲げた。なお、実施例１および２の単位素子７は３直列であるが、評価に当たっては便宜上、一つの単位素子７を挟む接続用電極１９と取り出し電極３５の間にプローブを当てて測定した。従って、本表の開放端電圧を３倍すると、実施例１および２の太陽電池特性となる。また、ミドルｉ層とはｉ層１１ｉ、ボトムｉ層とはｉ層９ｉのことであり、ボトムおよびミドルｐ⁺ ，ｐ，ｎ層の各膜厚は、表１のものと同一とした。
【００３８】
【表２】

【００３９】
このように、ボトムｉ層９ｉおよびボトムｎ層９ｎの最も厚いもので、それぞれ１５．１％と１６．０％の変換効率が得られ、従来の非晶質シリコンによるタンデム型に比べて、大幅な変換効率の向上が見られた。これは、図２，図３で示したように、各光起電力単位層における吸収係数と分光感度特性によって、広い波長領域の光が効率的に発電に寄与している為である。また光劣化も殆ど無く、極めて信頼性の高いものが得られていることが確認できた。これは表中にもあるように、第１の光起電力単位層３のｉ層（トップｉ層１５ｉ）の膜厚が最大でも０．２μｍであり、トップｐ層１５ｐとトップｎ層１５ｎによって形成されるトップｉ層１５ｉ内の電界強度が強く、キャリアの収集効率が高くなっている為と考えられる。
また、両者を比較すると実施例２の方が変換効率が高くなっているが、これは表から明らかなように、短絡電流の差によるものである。これは、光活性層となっているボトムｉ層９ｉ、ボトムｎ層９ｎおよびミドルｉ層１１ｉが、その膜中に取り込まれている酸素によるサーマルドナー効果によって若干ｎ型にシフトしており、ｎ側入射の場合には、発電に寄与する光活性領域の電界強度がｐ側入射に比べて弱くなり、キャリアの収集効率に差が生じているためと推察される。
【００４０】
また、第２の光起電力単位層５の形成態様が前の２例と異なるものとして、図６、７の構造も考えられる。これらのものは図示するように、２つのｐ−ｉ−ｎ接合またはｐ−ｎ接合を、基板１の面方向に直列接続して第２の光起電力単位層５が構成されたものである。以下、各例について説明する。なお、図６、７においては、第２の光起電力単位層５を構成する２つのｐ−ｉ−ｎまたはｐ−ｎ接合に上下関係がないため、以下の説明では、先のボトム、ミドルを第１のボトム、第２のボトムと表している。
先ず図６に示したものは、２つの光起電力単位層３，５が、非晶質シリコン系の光活性層を有する第１の光起電力単位層３と、結晶シリコン系の光活性層を有する第２の光起電力単位層５であり、さらに第２の光起電力単位層５は２つのｐ−ｉ−ｎ接合５ａ，５ｂが基板の面方向に並設して直列に接続された構造であって、第１の光起電力単位層３が光の入射側の最上部に設けられ、基板１上でその面方向に配列設置された複数の第２の光起電力単位層５…上のそれぞれに第１の光起電力単位層３…が設けられて、第１および第２の光起電力単位層３，５よりなる複数の単位素子７…が構成され、第１および第２の光起電力単位層３，５の一導電型側となる第１電極１７，１７同士を接続した接続用電極１９が、隣設される単位素子７の第１および第２の光起電力単位層３，５の逆導電型側となる第２電極２１に接続されることで、複数の単位素子７…が基板１上で電気的に直列接続された、並列型集積化太陽電池２３である。
【００４１】
以下さらに説明するが、基本的な製造方法は前記実施例１と同様の方法が用いられるので、ここでの重複説明は省略して構造のみを詳細に説明する。
ガラス基板１上に、ｐ型非晶質シリコンにエキシマレーザーを照射することによって結晶化した、多結晶シリコンよりなるｐ⁺ 層３６ｐ⁺ 、プラズマＣＶＤ法によるｉ型多結晶シリコンよりなるｉ層３６ｉ、プラズマＣＶＤ法によるｎ型微結晶シリコンよりなるｎ層３６ｎ、が順次積層される。そして、素子分離溝２７および分割溝３７によって分割することにより、第１のボトムｐ⁺ 層９ｐ⁺ 、第１のボトムｉ層９ｉ、第１のボトムｎ層９ｎよりなる一方のｐ−ｉ−ｎ接合５ｂと、第２のボトムｐ⁺ 層１１ｐ⁺ 、第２のボトムｉ層１１ｉ、第２のボトムｎ層１１ｎよりなる他方のｐ−ｉ−ｎ接合５ａに分割され、これらより第２の光起電力単位層５が構成される。ここで、ｐ⁺ 層３６ｐ⁺ の形成前に、基板１上には予め高融点金属よりなる金属電極３８が設けられ、これが他方のｐ−ｉ−ｎ接合５ａの第２のボトムｐ⁺ 層１１ｐ⁺ の接続取り出し用電極となっている。
一方のｐ−ｉ−ｎ接合５ｂの第１のボトムｎ層９ｎと、金属電極３８との間には、直列接続用電極３９が設けられ、これによって２つのｐ−ｉ−ｎ接合５ａ，５ｂが直列に接続されて、第２の光起電力単位層５が構成されている。ここで、一方のｐ−ｉ−ｎ接合５ｂの第１のボトムｐ⁺ 層９ｐ⁺ が、第２の光起電力単位層５の第１電極１７となる。この第２の光起電力単位層５は、言わば基板１上に形成された集積化薄膜多結晶シリコン太陽電池と見なせ、その具体的製造方法については後述するが、素子分離溝２７および分割溝３７をレーザー溶断によって形成する際の熱作用により、単位素子７およびｐ−ｉ−ｎ接合５ａ，５ｂの端面には、接続用電極１９および直列接続用電極３９によるｐ−ｎ間ショートを防止する為のＳｉＯ₂ のガードリング層３３が形成されている。また直列接続用電極３９は、一方のｐ−ｉ−ｎ接合５ｂの感度波長領域に吸収のないＳｎＯ₂ 等の透明導電材料や、金属による櫛形電極が用いられる。
さらに、第１および第２のボトムｉ層９ｉ，１１ｉを、光活性層となりうる範囲でｐ型不純物をドーピングしたｐ層とすることもできる。この場合には、ｐ−ｎ接合となる。
【００４２】
一方のｐ−ｉ−ｎ接合５ｂ上にのみ絶縁層１３が設けられ、この上に中間電極層２５を介して第１の光起電力単位層３が形成され、第２の光起電力単位層５と並列に接続される。すなわち、中間電極層２５における他方のｐ−ｉ−ｎ接合５ａの第２のボトムｎ層１１ｎの部分と、トップｎ層１５ｎの部分とが、第２および第１の光起電力単位層５，３の第２電極２１にそれぞれ相当しており、図から明らかなように、中間電極層２５がこれら２つの第２電極２１，２１の機能を併せ持っている。なお中間電極層２５にも、ｐ−ｉ−ｎ接合５ａ，５ｂの感度波長領域に吸収のないＳｎＯ₂ 等の透明導電材料や、金属による櫛形電極が用いられる。
第１の光起電力単位層３は、前記実施例と同様、ｎ型非晶質シリコンよりなるトップｎ層１５ｎ、ｉ型非晶質シリコンよりなるトップｉ層１５ｉ、ｐ型非晶質シリコンカーバイドよりなるトップｐ層１５ｐが順次積層された積層体によって構成され、各層はプラズマＣＶＤ法によって形成することができる。トップｐ層１５ｐの上には、ＩＴＯの全面電極と金属の櫛型電極との積層構造よりなる第１電極１７が形成されている。
【００４３】
そして図示するように、一方のｐ−ｉ−ｎ接合５ｂと他方のｐ−ｉ−ｎ接合５ａが基板１上にその面方向に直列接続された第２の光起電力単位層５と、第１の光起電力単位層３とが重畳された構造の単位素子７…が、基板１の面方向に複数個配列設置され、第１および第２の光起電力単位層３，５の第１電極１７，１７同士を接続した接続用電極１９が、隣設される単位素子７の第１および第２の光起電力単位層３，５の第２電極２１，２１、すなわち、中間電極層２５に接続され、さらに両端部に取り出し電極３５，３５が形成されて、並列型集積化太陽電池２３となっている。
【００４４】
次に、図７に示すものは、第２の光起電力単位層５のｐ−ｎ接合方向が、図６の例とは逆のタイプのものである。図示するように、２つの光起電力単位層３，５が、非晶質シリコン系の光活性層を有する第１の光起電力単位層３と、結晶シリコン系の光活性層を有する第２の光起電力単位層５であり、さらに第２の光起電力単位層５は２つのｐ−ｎ接合５ａ，５ｂが基板の面方向に並設して直列に接続された構造であって、第１の光起電力単位層３が光の入射側の最上部に設けられ、基板１上でその面方向に配列設置された複数の第２の光起電力単位層５…上のそれぞれに第１の光起電力単位層３…が設けられて、第１および第２の光起電力単位層３，５よりなる複数の単位素子７…が構成され、第１および第２の光起電力単位層３，５の一導電型側となる第１電極１７，１７同士を接続した接続用電極１９が、隣設される単位素子７の第１および第２の光起電力単位層３，５の逆導電型側となる第２電極２１，２１のそれぞれに接続されることで、複数の単位素子７…が基板１上で電気的に直列接続された、並列型集積化太陽電池２３である。
【００４５】
以下さらに説明するが、基本的な製造方法は前記実施例１と同様の方法が用いられるので、ここでの重複説明は省略して構造のみを詳細に説明する。
ガラス基板１上に、ｐ型非晶質シリコンにエキシマレーザーを照射することによって結晶化した多結晶シリコンよりなるｐ⁺ 層３６ｐ⁺ 、プラズマＣＶＤ法によるｎ型多結晶シリコンよりなるｎ層３６ｎ、プラズマＣＶＤ法によるｐ型微結晶シリコンよりなるｐ層３６ｐ、が順次積層される。そして、素子分離溝２７および分割溝３７によって分割することにより、第１のボトムｐ⁺ 層９ｐ⁺ 、第１のボトムｎ層９ｎ、第１のボトムｐ層９ｐよりなる一方のｐ−ｎ接合５ｂと、第２のボトムｐ⁺ 層１１ｐ⁺ 、第２のボトムｎ層１１ｎ、第２のボトムｐ層１１ｐよりなる他方のｐ−ｎ接合５ａに分割され、これらより第２の光起電力単位層５が構成される。
ここで、ｐ⁺ 層３６ｐ⁺ の形成前に、基板１上には予め高融点金属よりなる金属電極３８が設けられ、これが他方のｐ−ｎ接合５ａの第２のボトムｐ⁺ 層１１ｐ⁺ の接続取り出し用電極となっている。
一方のｐ−ｎ接合５ｂの第１のボトムｐ層９ｐと金属電極３８との間には、直列接続用電極３９が設けられ、これによって２つのｐ−ｎ接合５ａ，５ｂが直列に接続され、また他方のｐ−ｎ接合５ａの第２のボトムｐ層１１ｐ上には第２電極２１が設けられ、第２の光起電力単位層５が構成されている。ここで、一方のｐ−ｎ接合５ｂの第１のボトムｐ⁺ 層９ｐ⁺ が、第２の光起電力単位層５の第１電極１７となっている。
この第２の光起電力単位層５も、言わば基板１上に形成された集積化薄膜多結晶シリコン太陽電池と見なせ、素子分離溝２７および分割溝３７をレーザー溶断によって形成する際の熱作用により、単位素子７およびｐ−ｎ接合５ａ，５ｂの端面に、接続用電極１９および直列接続用電極３９によるｐ−ｎ間ショートを防止する為のＳｉＯ₂ のガードリング層３３が形成されている。また第２電極２１および直列接続用電極３９は、第２の光起電力単位層５の感度波長領域に吸収のないＳｎＯ₂ 等の透明導電材料や、金属による櫛形電極が用いられる。
【００４６】
２つのｐ−ｎ接合５ａ，５ｂ上には絶縁層１３が設けられ、第１電極１７を介して第１の光起電力単位層３が形成され、接続用電極１９によって第２の光起電力単位層５と並列に接続されている。ここで、第１電極１７は、第２の光起電力単位層５の感度波長領域に吸収のないＳｎＯ₂ 等の透明導電材料や、金属による櫛形電極が用いられる。そして第１の光起電力単位層３は、ｎ型非晶質シリコンよりなるトップｎ層１５ｎ、ｉ型非晶質シリコンよりなるトップｉ層１５ｉ、ｐ型非晶質シリコンカーバイドよりなるトップｐ層１５ｐが順次積層された積層体によって構成され、各層はプラズマＣＶＤ法によって形成することができる。トップｐ層１５ｐの上には、ＩＴＯの全面電極と金属の櫛型電極との積層構造よりなる第２電極２１が形成されている。
【００４７】
そして図示するように、一方のｐ−ｎ接合５ｂと他方のｐ−ｎ接合５ａが、基板１上にその面方向に直列接続された第２の光起電力単位層５と、第１の光起電力単位層３とが重畳された構造の複数の単位素子７…が、基板１の面方向に配列設置され、第１および第２の光起電力単位層３，５の第１電極１７，１７同士を接続した接続用電極１９が、隣設される単位素子７の第１および第２の光起電力単位層３，５の第２電極２１，２１に接続され、さらに両端部に取り出し電極３５，３５が形成されて、並列型集積化太陽電池２３となっている。
【００４８】
この図６、７に示した構造は、第２の光起電力単位層５を構成する２つのｐ−ｉ−ｎ接合やｐ−ｎ接合が、基板１の面方向に直列に接続されたものである。従って、第１および第２のボトムｉ層９ｉ，１１ｉ、および同ｎ層９ｎ，１１ｎの膜厚を、その光透過特性の制約の下で決定する必要がなく、第２の光起電力層５として最大の変換効率が得られる膜厚に、自由に設定することができる。
【００４９】
また図６、７に示す構造における第２の光起電力単位層５は、前述のように言わば基板１上に形成された集積化薄膜多結晶シリコン太陽電池と見なせるが、以下にその製造方法について、図８を参照しつつ説明する。
図８は、集積化薄膜多結晶シリコン太陽電池の製造工程を、順を追って模式的に表した部分断面図である。以下、ｐ−ｉ−ｎ接合の場合を例にとり、順に説明する。
先ずガラス基板１上に、接続取り出し用の金属電極３８をパターンニング形成し、その上にｐ型非晶質シリコンにエキシマレーザーを照射することによって結晶化した多結晶シリコンよりなるｐ⁺ 層３６ｐ⁺ を形成し、レーザー溶断によって分割して第１および第２のｐ⁺ 層９ｐ´，１１ｐ´を形成する（工程Ａ）。この金属電極３８はクロムやモリブデン、あるいはタングステン等の高融点金属が望ましく、ｐ⁺ 層領域の一部に形成してもよいし、ｐ⁺ 層全域をカバーしうる櫛型のものでもよい。
次に、この第１および第２のｐ⁺ 層９ｐ´，１１ｐ´の上に跨がって、プラズマＣＶＤ法によるｉ型多結晶シリコンよりなるｉ層３６ｉ、プラズマＣＶＤ法によるｎ型微結晶シリコンよりなるｎ層３６ｎ、第２電極２１となるＩＴＯやＳｎＯ₂ 等の透明導電材料の全面電極３６ｅが順次積層される（工程Ｂ）。
続いて、酸素雰囲気下で、集光したエキシマレーザービームやＹＡＧレーザービームを照射することで、積層体のうちの金属電極３８以外を部分的に溶断して分割溝３７を形成し、２つのｐ−ｉ−ｎ接合５ａ，５ｂを形成する。なおこの時のレーザー溶断による熱作用と雰囲気下の過剰な酸素の存在によって、ｐ−ｉ−ｎ接合５ａ，５ｂの端面には、ｐ−ｎショートの防止層として機能するＳｉＯ₂ のガードリング層３３が形成される（工程Ｃ）。
そして、金属電極３８の分割溝３７への露出部と、隣設するｐ−ｉ−ｎ接合５ｂの第２電極２１との間に直列接続用電極３９を形成して、直列接続が完成する（工程Ｄ）。この直列接続用電極３９は第２電極２１と接触しておれば事足りるが、より電流の収集効率を高くする為に、第２電極２１上の全面にわたって櫛型に形成した金属電極や、ＩＴＯやＳｎＯ₂ 等の透明導電材料による全面電極でもよい。
以上のように、本発明に適用しうる集積化薄膜多結晶シリコン太陽電池の製造工程は、そのパターンニングにレーザーを用いるというだけのものではなく、パターンニングとｐ−ｉ−ｎまたはｐ−ｎ接合端面のカードリングの形成を、分割溝３７のレーザー溶断時に同時に行うという特徴的なものである。
【００５０】
以上の実施例では、第１および第２の光起電力単位層３，５にシリコン系の半導体材料を用いた例を示したが、例えば、シリコンゲルマニウムやその他の化合物半導体材料等、光学的禁制帯幅の異なる複数の材料の組み合わせであってもよいし、絶縁層１３としては、例示したＳｉＯ₂ 以外にもＹ₂ Ｏ₃ やＳｉ₃ Ｎ₄ 等でもよく、また透明導電材料としても、例示したＳｎＯ₂ 以外にＩＴＯやＺｎＯであってもよく、特に本実施例に限定されるものではない。
加えて、第１の光起電力単位層に非晶質シリコンを用いる場合には、光入射側をｐ層にすることで、より高い出力特性が得られる。これは、通常の成膜条件下で得られるｉ型非晶質シリコンが、若干ｎ型にシフトしていることに起因する。すなわち、膜質の変動によっては、ｎ層がｉ層に対するオーミック接触層として機能する場合があるので、非晶質シリコンが短波長光の吸収特性が優れていることから、より浅い部分に接合特性に優れるｐ／ｉ界面が存在する方が望ましいからである。
【００５１】
また図１、図４〜図７において、ガラス基板１の背面、すなわち光入射側と反対の面１Ｂに、アルミニウムや銀等の反射率の高い金属薄膜を形成してもよい。これにより、裏面反射による光の閉じ込め効果を得ることができ、一層の変換効率向上を図ることができる。
【００５２】
さらに、光入射側の最上部にパシベーション層を形成することが、信頼性確保の点では望ましい。
【００５３】
【発明の効果】
以上のように本発明は、光学的禁制帯幅の異なる複数の光起電力単位層を、光の入射側に位置する光起電力単位層の光学的禁制帯幅が最も広くなるよう基板上に電気的に並列に接続して一つの単位素子として重畳形成し、かつそれぞれの光起電力単位層の出力電圧をほぼ等しく、さらに該単位素子を基板面方向においてそれぞれ電気的に直列接続している。従って、各層毎に直列に接続され、端部で並列に接続された従来のタンデム構造と異なり、取り出せる電流が上下層からの出力電流の和となるので、従来のように電流制限を受けることがなく、電流利得と電圧利得の両方に優れたものとなる。しかも上述のように、一つの単位素子を構成する複数の光起電力単位層の出力電圧がほぼ等しく、この単位素子が基板上に直列に接続される構造であることから、上下層の直列接続数の比を従来のように出力電圧の比に基づいて設定する必要が無い為、設計の自由度が大きくなる。
さらに、複数の光起電力単位層を、非晶質系の光活性層を有する第１の光起電力単位層と、結晶系の光活性層を有する第２の光起電力単位層によって構成し、しかも第１の光起電力単位層を光の入射側に設けているので、広い波長範囲に対して高い感度を有することができ、変換効率の大幅な向上が実現する。特に、一つの接合を持つ非晶質シリコンの第１の光起電力単位層と、２つの接合が直列に接続された多結晶シリコンの第２の光起電力単位層とを、第１の光起電力単位層が光の入射側となるように重畳すれば、２つの光起電力単位層の出力電圧がほぼ同じとなる。従って、ロスの無い高い変換効率を得ることができるとともに、前述のように基板上に直列接続するとき、２つの光起電力単位層の直列数を設計する必要も無くなって設計自由度が向上する。
【００５４】
また、単位素子や光起電力単位層の単位でショートやオープンによる欠陥が発生した場合、欠陥を有する単位素子の両側の接続用電極間を導電ペースト等で短絡させることにより、集積化太陽電池として所望の出力電流が得られるよう、簡便にリペアを行うことができる。このリペアは、図４〜図７の構造では、例えば第１の光起電力単位層の光入射側の電極と接続用電極との間に導電ペースト等を少量塗布したり、欠陥を有する単位素子をレーザーショットによって溶融ショートさせると言った、極めて簡便な方法で行うことができる。この時には、出力電圧は欠陥の存在する単位素子の分だけ低下するが、スペック上満足するレベルであれば使用できるので、製造歩留りの向上に大きく寄与し、ひいては太陽電池のコストダウン効果となって現れる。これは、本発明の太陽電池構造が、図４〜図７に示したように、その製造工程内でパシベーション層を形成する前に、各単位素子の両側に位置する２つの接続用電極に測定用プローブを当てることで、個々の単位素子の電気特性を個別に測定できる構造となっているからである。これが前述の従来例１であると、第１および第２の光起電力素子のどの部分で欠陥が発生しているかを容易に判別することができない為、特に一か所でもオープン欠陥があると、その太陽電池は不良となってしまう。従って本発明の太陽電池は、従来例に対して優れたコストメリットを有していると言える。
さらに前述のように、本発明の太陽電池はパターン形成やガードリング層の形成にレーザーを用いることができるので、レーザー装置を製造工程とリペア工程で兼用できることから、高歩留りでかつ設備コストの低い製造ラインを構築することができる。
【００５５】
基板側に位置する光起電力単位層が２つ以上のｐ−ｉ−ｎまたはｐ−ｎ接合を有する場合に、これらを重畳形成すると、製造工程が簡略化されて低コスト化が実現できる。また、単位素子の直列方向における長さ当たりの出力電圧が大きくなることから、コンパクトで高電圧の太陽電池素子が得られる。
一方、これら接合を基板の面方向に並設して直列に接続すると、出力が最も大きくなるよう、それぞれの膜厚を単独に設定することができるので、より高い出力が得られやすい。加えて、少々膜厚がばらついても出力電流はそれほど変動しないことから、出力ばらつきの少ない太陽電池を得ることができる。
【００５６】
そして、第１の光起電力単位層に非晶質シリコンを用いても、光劣化が殆ど無い極めて信頼性の高いものになるとともに、従来では到底得ることのできなかったレベルの高い変換効率が達成できた。これより、本発明は、非晶質シリコン太陽電池の実用化に対して、大きなブレークスルーとなるものであると言える。
【図面の簡単な説明】
【図１】本発明の並列型集積化太陽電池の積層構造を表す要部断面説明図
【図２】各種シリコン材料の吸収係数の波長依存性を表す説明図
【図３】本発明の具体例における各光活性層の分光感度特性を表す説明図
【図４】本発明の実施例１の断面説明図
【図５】本発明の実施例２の断面説明図
【図６】本発明の他の実施例の断面説明図
【図７】本発明の他の実施例の断面説明図
【図８】集積化薄膜多結晶シリコン太陽電池の形成工程例を表す説明図
【図９】従来の並列型集積化太陽電池の断面説明図
【図１０】従来の並列型太陽電池の断面説明図
【符号の説明】
１ ガラス基板
３ 第１の光起電力単位層
５ 第２の光起電力単位層
７ 単位素子
９ｐ⁺ ボトムｐ⁺ 層，第１のボトムｐ⁺ 層
９ｐ ボトムｐ層
９ｐ´第１のｐ⁺ 層
９ｉ ボトムｉ層，第１のボトムｉ層
９ｉ´第１のｉ層
９ｎ ボトムｎ層，第１のボトムｎ層
９ｎ´第１のｎ層
１１ｐ ミドルｐ層，第２のボトムｐ層
１１ｐ´第２のｐ⁺ 層
１１ｉ ミドルｉ層，第２のボトムｉ層
１１ｉ´第２のｉ層
１１ｎ ミドルｎ層，第２のボトムｎ層
１１ｎ´第２のｉ層
１３ 絶縁層
１５ｐ トップｐ層
１５ｉ トップｉ層
１５ｎ トップｎ層
１７ 第１電極
１９ 接続用電極
２１ 第２電極
２３ 並列型集積化太陽電池
２５ 中間電極層
２７ 素子分離溝
２９ 第１の接続用段部
３１ 第２の接続用段部
３３ ガードリング層
３５ 取り出し電極
３６ｐ ｐ層
３６ｉ ｉ層
３６ｎ ｎ層
３７ 分割溝
３８ 金属電極
３９ 直列接続用電極
４０ 第１単位発電膜
４２ 第１の光起電力素子
４４ 第２単位発電膜
４６ 第２の光起電力素子
４８，５０ 非晶質太陽電池素子
５２ 基板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure capable of increasing both current gain and voltage gain in an integrated solar cell formed on a substrate.
[0002]
[Prior art]
Amorphous silicon solar cells have been attracting attention as low-cost solar cells, but due to their low energy conversion efficiency and photodegradation phenomenon, there is a delay in the practical use of crystalline silicon. Among them, the photodegradation phenomenon is regarded as important, and it is known that the photodegradation phenomenon decreases as the film thickness of the photoactive layer contributing to power generation decreases. However, the energy conversion efficiency tends to decrease as the photoactive layer becomes thinner, and since both have a trade-off relationship, two amorphous silicon solar cell elements are superposed to form an upper element on the light incident side. A so-called tandem structure has been proposed in which the photoactive layer is thinned to absorb short-wavelength light, and long-wavelength light that passes through the light-active layer is absorbed by the lower element having a thick film thickness.
[0003]
This tandem structure has been confirmed to have an effect of improving light deterioration because the amount of short-wavelength light incident on the thicker lower element is reduced and the upper element is thin. However, this tandem structure is a structure in which two solar cell elements are overlapped, and since the upper and lower elements are connected in series, there is a problem that the output current as a whole is restricted to the lower side.
[0004]
In order to solve this problem, various structures have been proposed in which two types of solar cell elements are superimposed on each other and are connected in parallel.
[0005]
First, as disclosed in Japanese Patent Application Laid-Open No. 61-75567 (hereinafter referred to as Conventional Example 1), as shown in FIG. 9, a first photovoltaic power generation in which a plurality of first unit power generation films 40 are connected in series. The element 42 and a second photovoltaic element 46 in which a plurality of second unit power generation films 44 are connected in series are connected in parallel at both ends, and the first and second photovoltaic elements 42, 46 are connected to each other. The series numbers of the respective unit power generation films 40 and 44 are set so that the output voltages are substantially equal.
[0006]
Next, a device described in JP-A-2-378 (hereinafter referred to as Conventional Example 2) has at least two amorphous silicon solar cell elements having a pin junction as shown in FIG. 48 and 50 are overlapped, and the output ends of the respective solar cell elements are connected in parallel.
[0007]
Further, the one described in Japanese Patent Laid-Open No. Hei 4-22176 (hereinafter referred to as Conventional Example 3) has a thickness of each photoactive layer formed in an overlapping manner in order to optimize the output and the light degradation rate in Conventional Example 2. The range is limited. Specifically, the lowermost photoactive layer 48i is 3000 mm or more, the photoactive layer 50i different from the lowermost part is 1500 mm or less, and the film thickness ratio between them is 2 to 2.5: 1.
[0008]
[Problems to be solved by the invention]
However, each of the conventional examples 1 to 3 has the following problems. First, in the conventional example 1, the final output voltages of the two photovoltaic elements 42 and 46 are matched by increasing or decreasing the number of series connection stages of the first and second unit power generation films 40 and 44 constituting the photovoltaic elements 42 and 46. . Therefore, since the ratio of the number of series connections of the first and second unit power generation films 40 and 44 must always be set based on the ratio of the output voltage of the unit power generation films 40 and 44, the degree of design freedom is increased. Lower. This is an appropriate integer based on the ratio of the series connection numbers of the first and second unit power generation films 40 and 44 constituting the photovoltaic elements 42 and 46 based on the ratio of output voltages of the unit power generation films 40 and 44. This is because the ratio must be set.
[0009]
Next, with respect to Conventional Example 2, amorphous silicon solar cell elements 48 and 50 having a pin structure are stacked on a substrate 52, and each amorphous silicon solar cell element 48, The optical forbidden bandwidths of 50 are equal. Accordingly, since the spectral sensitivity characteristics of the superimposed amorphous silicon solar cell elements 48 and 50 are also the same, only light up to the limit wavelength determined by the optical forbidden band contributes to power generation. However, although the power generation output is improved as compared with the conventional tandem structure, the wavelength range of the light that can be used for power generation does not change, so a sufficient improvement in the power generation output cannot be expected.
[0010]
Further, with respect to Conventional Example 3, the film thickness of the photoactive layer (i layers 48i, 50i) of Conventional Example 2 is optimized, and the basic configuration such as structure and optical forbidden bandwidth is the same as that of Conventional Example 2. Are the same. Therefore, like the conventional example 2, although the power generation output is certainly improved as compared with the conventional tandem structure, the wavelength range of the light that can be used for power generation does not change, and therefore a sufficient improvement in the power generation output cannot be expected. .
[0011]
[Means for Solving the Problems]
The present invention has been devised in order to solve various problems in the above-described conventional example. In the parallel integrated solar cell of the present invention, a plurality of photovoltaic unit layers having different optical forbidden bandwidths are superimposed while being electrically connected in parallel, and the uppermost photovoltaic unit layer is viewed from the light incident side. By widening the optical forbidden bandwidth of the power unit layer, the wavelength range of sunlight that contributes to power generation is expanded, and the output voltage of each photovoltaic unit layer is made equal. The photovoltaic unit layers adjacent to each other in the lateral direction, that is, the substrate surface direction, are electrically connected in series.
Accordingly, the number of series connections in the substrate surface direction of the uppermost photovoltaic unit layer is equal to the number of series connection of the photovoltaic unit layers other than the uppermost photovoltaic unit layer. Further, the number of pin or pn junctions of the photovoltaic unit layers other than the uppermost portion is set to two or more, or the position of the Fermi level in one pin or pn junction. By adjusting the output voltage, the output voltages of the photovoltaic unit layers are matched substantially the same.
[0012]
  Specifically, the present invention specifically includes a plurality of photovoltaic unit layers having at least one pin or pn junction and having different optical forbidden bandwidths.The photovoltaic unit layer located on the light incident side has the widest optical forbidden band width, and is formed on the substrate so that the output voltages of the photovoltaic unit layers are substantially equal. The stacked photovoltaic unit layers are electrically connected in parallel to form one unit element,Furthermore, the unit element is in the direction of the substrate surface.MultipleEach can be realized by a structure electrically connected in series.
[0013]
  The plurality of photovoltaic unit layers are a first photovoltaic unit layer having an amorphous photoactive layer and a second photovoltaic unit layer having a crystalline photoactive layer, A configuration in which the first photovoltaic unit layer is provided at the uppermost part on the light incident side may be employed.The substrate is a glass substrate, and the plurality of photovoltaic unit layers includes a first photovoltaic unit layer having an amorphous silicon-based photoactive layer and a crystalline silicon-based photoactive layer. 2 is a photovoltaic unit layer, wherein a second photovoltaic unit layer is formed on the glass substrate, and a first photovoltaic unit layer serving as a light incident side is formed on the second photovoltaic unit layer. It can also be taken.
[0014]
  Further, the plurality of photovoltaic unit layers are a first photovoltaic unit layer having an amorphous silicon-based photoactive layer and a second photovoltaic unit layer having a crystalline silicon-based photoactive layer. And the second photovoltaic unit layer has a tandem structure in which two pn or pn junctions are superimposed and connected in series, and the first photovoltaic unit layer is on the light incident side. A first photovoltaic unit layer is provided on each of the plurality of second photovoltaic unit layers provided on the uppermost portion and arranged in the plane direction on the substrate. A unit in which a plurality of unit elements each including a photovoltaic unit layer are configured, and a connection electrode connecting the first electrodes on the one conductivity type side of the first and second photovoltaic unit layers is provided next to each other. A plurality of unit elements are connected to the second electrode on the opposite conductivity type side of the first and second photovoltaic unit layers of the element. There may be electrically connected in series configuration.
  The second 1 The light incident side of the photovoltaic unit layer may be a p layer, the substrate may be a glass substrate, and a metal thin film having a high reflectivity may be formed on a surface opposite to the light incident side of the glass substrate. preferable.
[0015]
Here, when each photoactive layer is a silicon system, the uppermost part can be composed of an amorphous system and the other parts can be composed of a crystal system, by a simple manufacturing method. Accordingly, the optical forbidden band width can be easily made different, and the uppermost photovoltaic unit layer is formed by one pin or pn junction, and the photovoltaic unit layers other than the uppermost portion are By comprising at least one, preferably two p-i-n or p-n junctions, the output voltage can be easily matched. This is because the open-circuit voltage at AM 1.5 / 100 mW is about 0.9 to 1.0 V in a pin junction using amorphous silicon, whereas a pin or pn junction using crystal silicon is used. This is because the open-circuit voltage due to the transmitted light from the photovoltaic unit layer of amorphous silicon is about 0.45 to 0.5V.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, as an embodiment of the present invention, a structure will be described based on the drawings. FIG. 1 shows a stacked structure of a parallel type integrated solar cell of the present invention. The figure shows a cross-sectional structure of a main part of one unit element 7 composed of two photovoltaic unit layers 3 and 5 formed on a glass substrate 1, and an amorphous silicon-based photoactive layer (15i). The first photovoltaic unit layer 3 and the second photovoltaic unit layer 5 having a crystalline silicon-based photoactive layer (11i, 9n). It is a tandem structure in which one pin junction 5a and one pin junction 5b are connected in series, and the first photovoltaic unit layer 3 is provided at the uppermost part on the light incident side. It is a thing.
More specifically, the bottom p of polycrystalline silicon is formed from the glass substrate 1 side.⁺Layer 9p⁺A bottom n layer 9n of polycrystalline silicon, a bottom p layer 9p of microcrystalline silicon, a middle n layer 11n of microcrystalline silicon, a middle i layer 11i of polycrystalline silicon, and a middle p layer 11p of microcrystalline silicon are formed in an overlapping manner. A second photovoltaic unit layer 5 having a tandem structure is formed, and further, SiO 2 as an insulating layer 13 is further formed thereon.₂A first photovoltaic unit layer 3 in which an amorphous silicon top n layer 15n, an amorphous silicon top i layer 15i, and an amorphous silicon carbide top p layer 15p are stacked is formed over the layers. A unit element 7 is constituted by the first photovoltaic unit layer 3 and the second photovoltaic unit layer 5.
[0017]
Next, the manufacturing method of the laminated structure of this example is demonstrated. First, an amorphous silicon film doped with a high concentration of p-type impurities is formed on the glass substrate 1 by a method such as a plasma CVD method. Next, by irradiating an excimer laser to crystallize this p-type amorphous silicon film, the bottom p⁺Layer 9p⁺Get. On this, an n-type polycrystalline silicon layer serving as a photoactive layer is formed by slightly doping an n-type impurity while applying a chemical annealing action by a plasma CVD method or the like to obtain a bottom n layer 9n. Subsequently, a microcrystalline silicon layer doped with a p-type impurity is formed by a plasma CVD method or the like to obtain a bottom p layer 9p. Since the bottom p layer 9p is on the light incident side with respect to the photoactive layer (bottom n layer 9n), the condition is set such that recombination at the p / n interface can be reduced.
[0018]
Subsequently, a microcrystalline silicon layer doped with an n-type impurity is formed on the bottom p layer 9p by a plasma CVD method or the like to obtain a middle n layer 11n. Subsequently, an i-type polycrystalline silicon layer serving as a photoactive layer is formed by applying a chemical annealing action by plasma CVD or the like to obtain a middle i layer 11i. Then, a microcrystalline silicon layer doped with a p-type impurity is formed on the middle i layer 11i by a plasma CVD method or the like to obtain a middle p layer 11p. Since the middle p layer 11p is on the light incident side with respect to the photoactive layer (middle i layer 11i), the condition is set such that recombination at the p / i interface can be reduced. In this state, the first p⁺, N, p layer 9p⁺˜9p and one pn junction 5a made of middle n, i, and p layers 11n to 11p are connected in series, and the second photovoltaic unit layer 5 It becomes. Where bottom p⁺Layer 9p⁺Is doped at a high concentration and has a low resistivity, and functions as the first electrode of the pn junction 5b.
[0019]
Next, when the first photovoltaic unit layer 3 is formed in the same order as the polarity of the second photovoltaic unit layer 5, plasma CVD is performed on the second photovoltaic unit layer 5. SiO or sputtering method₂The insulating layer 13 is formed, and then the top n layer 15n is formed on the insulating layer 13. The top n layer 15n is obtained by forming an amorphous silicon layer doped with an n-type impurity by a plasma CVD method or the like. Similarly, an i-type amorphous silicon layer to be a photoactive layer and an amorphous silicon carbide layer doped with a p-type impurity are sequentially formed by plasma CVD or the like, and the top i layer 15i and the top p layer 15p are formed. Get. One pin junction composed of the top n, i, p layers 15 n to 15 p formed on the second photovoltaic unit layer 5 becomes the first photovoltaic unit layer 3.
[0020]
And bottom p⁺Layer 9p⁺And the top n layer 15n and the middle p layer 11p and the top p layer 15p are connected to each other, the two photovoltaic unit layers 3 and 5 are connected in parallel. Here, the bottom p is formed from the substrate 1 side without providing the insulating layer 13.⁺Layer 9p⁺Top n layer 15n, top i layer on second photovoltaic unit layer 5 laminated in the order of bottom i layer 9i → bottom n layer 9n → middle p layer 11p → middle i layer 11i → middle n layer 11n Even if the first photovoltaic unit layer 3 in which the 15i and the top p layer 15p are sequentially laminated is superposed, the two photovoltaic unit layers can be connected in parallel.
[0021]
In such a structure, the optical forbidden band width of the amorphous silicon constituting the first photovoltaic unit layer 3 is about 1.8 eV, and the polycrystalline silicon constituting the second photovoltaic unit layer 5 is used. Is about 1.1 eV, and the photovoltaic power is generated in the second photovoltaic unit layer 5 by the incident light transmitted through the first photovoltaic unit layer 3.
That is, the limit wavelength that can be absorbed by the first photovoltaic unit layer 3 is 1240 (nm) ÷ 1.8≈689 nm, and the second photovoltaic unit layer 5 is about 1127 nm. Light in the wavelength region from 689 to 1127 nm is absorbed by the second photovoltaic unit layer 5. On the other hand, the open-circuit voltage generated at one pin junction by light irradiation is determined by the difference in Fermi level between the p layer and the n layer, so that sufficient electric field strength is obtained in the first photovoltaic unit layer 3. In the film quality condition, AM1.5,100mW / cm²It becomes 0.9-1.0V under the illumination conditions. In addition, the second photovoltaic unit layer 5 is constituted by the transmitted light from the first photovoltaic unit layer 3 under the same irradiation condition, that is, incident light in the wavelength region of 689 to 1127 nm. The open circuit voltages generated at the n junction 5a and the pn junction 5b are 0.45 to 0.5 V, respectively.
[0022]
Since the second photovoltaic unit layer 5 has one pin junction 5a and one pn junction 5b connected in series, the open circuit voltage generated is about 0.9 to 1.. 0 V, which is almost equal to the open circuit voltage of the first photovoltaic unit layer 3. Since the two photovoltaic unit layers 3 and 5 are connected in parallel, the output current is the sum of the output currents from both photovoltaic unit layers 3 and 5.
[0023]
FIG. 2 shows the light absorption characteristics of amorphous silicon (A), polycrystalline silicon (B) by laser annealing, polycrystalline silicon (C) by plasma CVD, and single crystal silicon (D). Energy is represented by taking an absorption coefficient on the vertical axis. FIG. 3 shows the spectral sensitivity characteristics in the superimposed state of the respective photoactive layers constituting the first photovoltaic unit layer 3 and the second photovoltaic unit layer 5, with the horizontal axis representing wavelength and the vertical axis The relative sensitivity is shown. In the figure, A represents the spectral sensitivity characteristics of the top i layer 15i, B represents the middle i layer 11i, and C represents the spectral sensitivity characteristic of the bottom i layer 9i. As is clear from these two figures, it can be seen that the laminated structure of FIG. 1 has characteristics covering the wavelength range of amorphous silicon and crystalline silicon.
[0024]
【Example】
Examples of the present invention will be described below.
Example 1
FIG. 4 shows a cross-sectional structure diagram of Embodiment 1 of the present invention. In the illustrated example, two photovoltaic unit layers 3 and 5 have a first photovoltaic unit layer 3 having an amorphous silicon-based photoactive layer and a second photovoltaic unit layer 3 having a crystalline silicon-based photoactive layer. It is a photovoltaic unit layer 5, and the second photovoltaic unit layer 5 has a tandem structure in which two pin junctions 5 a and 5 b are connected in series, and includes a first photovoltaic unit. The unit layer 3 is provided on the uppermost part on the light incident side, and the first photovoltaic unit is provided on each of the plurality of second photovoltaic unit layers 5... Arranged on the substrate 1 in the surface direction. A plurality of unit elements 7 comprising the first and second photovoltaic unit layers 3 and 5 are formed, and one of the first and second photovoltaic unit layers 3 and 5 is provided. The first and second photovoltaic unit layers of the unit element 7 in which the connection electrode 19 connecting the first electrodes 17 and 17 on the conductive type side is adjacent to each other is provided. , A plurality of unit elements 7 by being connected to the second electrode 21 serving as the opposite conductivity type side 5 is electrically connected in series, a parallel type integrated solar cell 23.
[0025]
More specific description will be given below.
First, monosilane gas (SiH) is formed on the glass substrate 1._Four) And diborane gas (B₂H₆) Is used as a raw material, and amorphous silicon doped with boron at a high concentration is formed by plasma CVD, and this is crystallized by irradiating it with an excimer laser to form a bottom p made of p-type polycrystalline silicon.⁺Layer 9p⁺Formed. Then this bottom p⁺Layer 9p⁺A bottom i layer 9i made of i-type polycrystalline silicon is formed by a plasma CVD method using monosilane gas as a raw material, and then monosilane gas and phosphine gas (PH) are formed on the bottom i layer 9i._Three) As a raw material, a bottom n layer 9n made of n-type microcrystalline silicon was formed by plasma CVD.
[0026]
Subsequently, a middle p layer 11p made of microcrystalline silicon using monosilane gas and diborane gas as raw materials, a middle i layer 11i made of polycrystalline silicon using monosilane gas as a raw material, and monosilane gas on the bottom n layer 9n by plasma CVD. A middle n layer 11n made of microcrystalline silicon is sequentially laminated using phosphine gas as a raw material, and the bottom p⁺Layer 9p⁺A second photovoltaic unit layer 5 in which six layers of up to middle n layer 11n were laminated was obtained. Where bottom p⁺Layer 9p⁺However, it functions as the first electrode 17 of the second photovoltaic unit layer 5. Also, the bottom i layer 9i can be a p-layer doped with impurities in a range that can become a photoactive layer. In this case, 5b is a pn junction.
[0027]
Next, over almost the entire surface of the second photovoltaic unit layer 5 on the middle n layer 11n, SnO is formed by CVD.₂An intermediate electrode layer 25 was formed. Subsequently, the top n layer 15n made of amorphous silicon using monosilane gas and phosphine gas as raw materials, the top i layer 15i made of amorphous silicon using monosilane gas as raw materials, monosilane gas, diborane gas, and methane gas (CH_Four) As a raw material, a top p layer 15p made of amorphous silicon carbide was sequentially laminated. A pin junction of three layers from the top n layer 15n to the top p layer 15p becomes the first photovoltaic unit layer 3. Here, the intermediate electrode layer 25 becomes the second electrode 21 common to the first and second photovoltaic unit layers 3 and 5.
[0028]
Then bottom p⁺Layer 9p⁺Forming element isolation trenches 27 by fusing 10 layers up to top p layer 15p → Forming first connection step 29 by fusing 9 layers from bottom i layer 9i to top p layer 15p → Top n layer 15n A series of processes of forming the second connection step 31 by fusing three layers up to the top p layer 15p was performed by irradiating an excimer laser in an oxygen atmosphere. In this state, the bottom p⁺Layer 9p⁺A plurality of unit elements 7 made up of 10 layers up to the top p layer 15p are arranged in the plane direction of the substrate 1. Further, by utilizing the oxidizing action at the time of fusing, SiO as the end face guard ring layer 33 is obtained.₂Forming a layer. In this way, when only the other layers were melted while leaving a specific layer, the laser output was adjusted based on thermal analysis. However, chemical etching using a difference in etching rate depending on the presence or absence of doping may be used.
Next, on the upper surface of the top p layer 15 p, that is, on the first photovoltaic unit layer 3, the first electrode 17 having a laminated structure of the entire ITO electrode and the metal comb electrode was formed. Finally, the connection electrode 19 connecting the first electrodes 17 and 17 of the first and second photovoltaic unit layers 3 and 5 is connected to the first and second light beams of the adjacent unit elements 7. Connected to the second electrode 21 of the electromotive force unit layers 3 and 5 and formed the take-out electrodes 35 and 35 at both ends to obtain a parallel integrated solar cell 23 of Example 1.
[0029]
(Example 2)
FIG. 5 shows a cross-sectional structure diagram of Embodiment 2 of the present invention. As in the first embodiment, the two photovoltaic unit layers include a first photovoltaic unit layer 3 having an amorphous silicon-based photoactive layer and a second photovoltaic unit layer having a crystalline silicon-based photoactive layer. Unlike the first embodiment, the second photovoltaic unit layer 5 is a photovoltaic unit layer 5, and one pin junction 5 a and one pn junction 5 b are connected in series. A plurality of second photovoltaic units having the first photovoltaic unit layer 3 provided on the uppermost portion on the light incident side and arranged in the plane direction on the substrate 1. A first photovoltaic unit layer 3 is provided on each of the layers 5... To form a plurality of unit elements 7 composed of the first and second photovoltaic unit layers 3, 5. And a connecting electrode 19 that connects the first electrodes 17 and 17 on the one conductivity type side of the second photovoltaic unit layers 3 and 5 are adjacent to each other. The plurality of unit elements 7 are electrically connected in series by being connected to each of the second electrodes 21, 21 on the opposite conductivity type side of the first and second photovoltaic unit layers 3, 5 of the potential element 7. The connected integrated solar cells 23 are connected.
[0030]
As will be further described below, the basic manufacturing method is almost the same as that of the first embodiment, and therefore, a duplicate description thereof will be omitted, and only the structure will be described in detail.
Bottom p made of polycrystalline silicon crystallized by irradiating an excimer laser on p-type amorphous silicon on glass substrate 1⁺Layer 9p⁺, Bottom n layer 9n as a photoactive layer made of n-type polycrystalline silicon, bottom p layer 9p made of p-type microcrystalline silicon, middle n layer 11n made of n-type microcrystalline silicon, middle made of i-type polycrystalline silicon An i layer 11i and a middle p layer 11p made of p-type microcrystalline silicon are sequentially stacked.⁺Layer 9p⁺The second photovoltaic unit layer 5 is composed of a laminate of six layers up to the middle p layer 11p. Where bottom p⁺Layer 9p⁺Becomes the first electrode 17 of the second photovoltaic unit layer 5.
[0031]
And on the middle p layer 11p, there is SnO which is not absorbed in the sensitivity wavelength region of the second photovoltaic unit layer 5.₂The second electrode 21 is provided.
[0032]
On the second electrode 21 of the second photovoltaic unit layer 5, SiO 2₂SnO serving as the first electrode 17 of the insulating layer 13 and the first photovoltaic unit layer 3₂Further, a top n layer 15n made of n-type amorphous silicon and a top i layer 15i made of i-type amorphous silicon are formed on the first electrode 17 of the first photovoltaic unit layer 3. The top p layer 15p made of p-type amorphous silicon carbide is sequentially laminated, and the first photovoltaic unit layer 3 is constituted by a laminate of three layers from the top n layer 15n to the top p layer 15p. The On the top p layer 15p, a second electrode 21 having a laminated structure of an ITO full-surface electrode and a metal comb electrode is formed.
[0033]
Thus, the bottom p⁺Layer 9p⁺The unit element 7 is composed of a laminate of up to the top p layer 15p. A plurality of unit elements 7 are arranged in the plane direction of the substrate 1 and a connection electrode 19 is formed by connecting the first electrodes 17 and 17 of the first and second photovoltaic unit layers 3 and 5 to each other. Is connected to the second electrodes 21 and 21 of the first and second photovoltaic unit layers 3 and 5 of the adjacent unit element 7, and the take-out electrodes 35 and 35 are formed at both ends. This is the parallel integrated solar cell 23 of Example 2. Here, in order to prevent a short circuit between the photovoltaic unit layers 3 and 5, as in the first embodiment, the side surface is made of SiO.₂A guard ring layer 33 such as is provided.
[0034]
In the above two embodiments, the photoactive layers of the first and second photovoltaic unit layers 3 and 5 are amorphous silicon and polycrystalline silicon, respectively. First, the characteristics of the solar cell 23 of the present invention are greatly increased. The electric characteristics of the single cell of the influencing second photovoltaic unit layer 5 were evaluated by changing the film thickness conditions in the stacked structure of FIG. 4 having two pin junctions, and the results are shown in Table 1. It was raised in. In the table, the middle layer refers to the stacked portion from the middle p layer 11p to the middle n layer 11n, and the bottom layer refers to the bottom p.⁺Layer 9p⁺-Represents each laminated portion up to the bottom n layer 9n. Measurement conditions are AM1.5, 100mW / cm²25 ° C.
[0035]
[Table 1]

[0036]
Thus, the conversion efficiency increases as the film thickness of the bottom i layer 9i increases. This is presumably because the transmitted light decreases as the bottom i layer 9i is thicker and the sensitivity of the longer wavelength light becomes higher because the short-circuit current increases.
[0037]
Furthermore, each layer thickness of the solar cell of Examples 1 and 2 was changed, and AM1.5, 100 mW / cm²The electrical characteristics at 25 ° C. were measured, and the measurement results are shown in Table 2. The unit elements 7 of Examples 1 and 2 are in series, but for the sake of convenience, the measurement was performed by placing a probe between the connection electrode 19 and the extraction electrode 35 sandwiching one unit element 7. Therefore, when the open-circuit voltage in this table is tripled, the solar cell characteristics of Examples 1 and 2 are obtained. The middle i layer is the i layer 11i, the bottom i layer is the i layer 9i, and the bottom and middle p⁺, P, n layers have the same thickness as that in Table 1.
[0038]
[Table 2]

[0039]
In this way, the bottom i layer 9i and the bottom n layer 9n are the thickest ones, and conversion efficiencies of 15.1% and 16.0% are obtained, respectively, which is significantly higher than the conventional tandem type using amorphous silicon. A significant improvement in conversion efficiency was observed. This is because, as shown in FIGS. 2 and 3, light in a wide wavelength region efficiently contributes to power generation due to the absorption coefficient and spectral sensitivity characteristics in each photovoltaic unit layer. Further, it was confirmed that there was almost no light deterioration and a highly reliable product was obtained. As shown in the table, the film thickness of the i layer (top i layer 15i) of the first photovoltaic unit layer 3 is 0.2 μm at the maximum, and the top p layer 15p and the top n layer 15n This is presumably because the electric field strength in the formed top i layer 15i is strong and the carrier collection efficiency is high.
Further, when the two are compared, the conversion efficiency is higher in Example 2, which is due to the difference in the short-circuit current, as is apparent from the table. This is because the bottom i layer 9i, the bottom n layer 9n, and the middle i layer 11i, which are photoactive layers, are slightly shifted to the n-type due to the thermal donor effect due to oxygen incorporated in the film. In the case of side incidence, it is presumed that the electric field intensity of the photoactive region contributing to power generation is weaker than that of p side incidence, and there is a difference in carrier collection efficiency.
[0040]
Moreover, the structure of FIG. 6, 7 is also considered that the formation aspect of the 2nd photovoltaic unit layer 5 differs from the previous 2 examples. As shown in the figure, the second photovoltaic unit layer 5 is configured by connecting two pin junctions or pn junctions in series in the plane direction of the substrate 1. . Each example will be described below. 6 and 7, since there is no vertical relationship between the two pin or pn junctions constituting the second photovoltaic unit layer 5, in the following description, the above bottom and middle Are represented as a first bottom and a second bottom.
First, what is shown in FIG. 6 is that two photovoltaic unit layers 3 and 5 include a first photovoltaic unit layer 3 having an amorphous silicon-based photoactive layer, and a crystalline silicon-based photoactive layer. And the second photovoltaic unit layer 5 is connected in series with two pin junctions 5a and 5b arranged in parallel in the plane direction of the substrate. The first photovoltaic unit layer 3 is provided on the uppermost portion on the light incident side, and a plurality of second photovoltaic unit layers 5 arranged in the plane direction on the substrate 1. .. Are provided with first photovoltaic unit layers 3... To form a plurality of unit elements 7 including first and second photovoltaic unit layers 3, 5. The connection electrode 19 connecting the first electrodes 17, 17 on the one conductivity type side of the two photovoltaic unit layers 3, 5 is the first of the adjacent unit elements 7. The plurality of unit elements 7 are electrically connected in series on the substrate 1 by being connected to the second electrode 21 on the opposite conductivity type side of the second photovoltaic unit layers 3 and 5. This is a type integrated solar cell 23.
[0041]
As will be further described below, since the basic manufacturing method is the same as that of the first embodiment, the description thereof will be omitted, and only the structure will be described in detail.
P made of polycrystalline silicon crystallized on a glass substrate 1 by irradiating p-type amorphous silicon with an excimer laser.⁺Layer 36p⁺Then, an i layer 36i made of i-type polycrystalline silicon by plasma CVD and an n layer 36n made of n-type microcrystalline silicon by plasma CVD are sequentially stacked. Then, the first bottom p is divided by the element isolation groove 27 and the division groove 37.⁺Layer 9p⁺, One p-i-n junction 5b composed of the first bottom i layer 9i and the first bottom n layer 9n, and the second bottom p⁺Layer 11p⁺The second bottom i layer 11i and the second bottom n layer 11n are divided into the other pin junction 5a, and the second photovoltaic unit layer 5 is constituted by these. Where p⁺Layer 36p⁺Before the formation of, a metal electrode 38 made of a refractory metal is provided on the substrate 1 in advance, and this is the second bottom p of the other pin junction 5a.⁺Layer 11p⁺This is an electrode for connecting and extracting.
A series connection electrode 39 is provided between the first bottom n layer 9n of one pin junction 5b and the metal electrode 38, whereby two pin junctions 5a, 5b are provided. Are connected in series to form the second photovoltaic unit layer 5. Here, the first bottom p of one of the p-i-n junctions 5b⁺Layer 9p⁺Becomes the first electrode 17 of the second photovoltaic unit layer 5. The second photovoltaic unit layer 5 can be regarded as an integrated thin-film polycrystalline silicon solar cell formed on the substrate 1, and a specific manufacturing method thereof will be described later. Due to the thermal action when forming 37 by laser fusing, the end faces of the unit element 7 and the pin junctions 5a and 5b are prevented from being short-circuited between pn by the connection electrode 19 and the series connection electrode 39. SiO for₂The guard ring layer 33 is formed. The series connection electrode 39 is SnO which has no absorption in the sensitivity wavelength region of the one pin junction 5b.₂For example, a transparent conductive material such as metal or a comb electrode made of metal is used.
Furthermore, the first and second bottom i layers 9i and 11i may be p layers doped with p-type impurities in a range that can become a photoactive layer. In this case, a pn junction is formed.
[0042]
The insulating layer 13 is provided only on one of the pin junctions 5b, and the first photovoltaic unit layer 3 is formed on the insulating layer 13 via the intermediate electrode layer 25. The second photovoltaic unit layer 5 is connected in parallel. That is, the second bottom n layer 11n portion and the top n layer 15n portion of the other pin junction 5a in the intermediate electrode layer 25 form the second and first photovoltaic unit layers 5, The intermediate electrode layer 25 has the functions of these two second electrodes 21 and 21 as is apparent from the drawing. The intermediate electrode layer 25 also has SnO which has no absorption in the sensitivity wavelength region of the p-i-n junctions 5a and 5b.₂For example, a transparent conductive material such as metal or a comb electrode made of metal is used.
The first photovoltaic unit layer 3 includes a top n layer 15n made of n-type amorphous silicon, a top i layer 15i made of i-type amorphous silicon, and a p-type amorphous silicon carbide, as in the previous embodiment. Each of the layers can be formed by a plasma CVD method. On the top p layer 15p, a first electrode 17 having a laminated structure of an ITO whole surface electrode and a metal comb electrode is formed.
[0043]
As shown in the figure, a second photovoltaic unit layer 5 in which one pin junction 5b and the other pin junction 5a are connected in series on the substrate 1 in the plane direction, A plurality of unit elements 7 having a structure in which one photovoltaic unit layer 3 is superimposed are arranged in the plane direction of the substrate 1, and the first and second photovoltaic unit layers 3, 5 are first arranged. The connecting electrode 19 connecting the electrodes 17 and 17 is the second electrode 21, 21 of the first and second photovoltaic unit layers 3, 5 of the adjacent unit element 7, that is, the intermediate electrode layer 25. Are connected to each other, and take-out electrodes 35 and 35 are formed at both ends to form a parallel integrated solar cell 23.
[0044]
Next, what is shown in FIG. 7 is a type in which the pn junction direction of the second photovoltaic unit layer 5 is opposite to the example of FIG. As shown in the figure, the two photovoltaic unit layers 3 and 5 include a first photovoltaic unit layer 3 having an amorphous silicon-based photoactive layer and a second photovoltaic unit-based photoactive layer. The second photovoltaic unit layer 5 has a structure in which two pn junctions 5a and 5b are arranged in parallel in the plane direction of the substrate and connected in series. The first photovoltaic unit layer 3 is provided on the uppermost part on the light incident side, and the first photovoltaic unit layer 3 is arranged on each of the plurality of second photovoltaic unit layers 5 arranged in the plane direction on the substrate 1. Are provided with a plurality of unit elements 7 including first and second photovoltaic unit layers 3 and 5, and first and second photovoltaic units are formed. The connection electrodes 19 connecting the first electrodes 17, 17 on the one conductivity type side of the layers 3, 5 are connected to the first and second of the adjacent unit elements 7. A parallel type in which a plurality of unit elements 7 are electrically connected in series on the substrate 1 by being connected to each of the second electrodes 21, 21 on the opposite conductivity type side of the electromotive force unit layers 3, 5. This is an integrated solar cell 23.
[0045]
As will be further described below, since the basic manufacturing method is the same as that of the first embodiment, the description thereof will be omitted, and only the structure will be described in detail.
P made of polycrystalline silicon crystallized by irradiating an excimer laser on p-type amorphous silicon on a glass substrate 1⁺Layer 36p⁺Then, an n layer 36n made of n-type polycrystalline silicon by plasma CVD and a p layer 36p made of p-type microcrystalline silicon by plasma CVD are sequentially stacked. Then, the first bottom p is divided by the element isolation groove 27 and the division groove 37.⁺Layer 9p⁺, One pn junction 5b composed of the first bottom n-layer 9n and the first bottom p-layer 9p, and the second bottom p⁺Layer 11p⁺The second bottom n layer 11n and the second bottom p layer 11p are divided into the other pn junction 5a, from which the second photovoltaic unit layer 5 is constructed.
Where p⁺Layer 36p⁺Before the formation of, a metal electrode 38 made of a refractory metal is provided on the substrate 1 in advance, and this is the second bottom p of the other pn junction 5a.⁺Layer 11p⁺This is an electrode for connecting and extracting.
A series connection electrode 39 is provided between the first bottom p layer 9p of one pn junction 5b and the metal electrode 38, whereby the two pn junctions 5a and 5b are connected in series. The second electrode 21 is provided on the second bottom p layer 11p of the other pn junction 5a to constitute the second photovoltaic unit layer 5. Here, the first bottom p of one pn junction 5b⁺Layer 9p⁺Is the first electrode 17 of the second photovoltaic unit layer 5.
The second photovoltaic unit layer 5 can also be regarded as an integrated thin film polycrystalline silicon solar cell formed on the substrate 1, and the thermal action when forming the element isolation groove 27 and the division groove 37 by laser fusing. Thus, SiO for preventing a pn short-circuit by the connection electrode 19 and the series connection electrode 39 on the end faces of the unit element 7 and the pn junctions 5a and 5b is obtained.₂The guard ring layer 33 is formed. Further, the second electrode 21 and the series connection electrode 39 are SnO having no absorption in the sensitivity wavelength region of the second photovoltaic unit layer 5.₂For example, a transparent conductive material such as metal or a comb electrode made of metal is used.
[0046]
The insulating layer 13 is provided on the two pn junctions 5 a and 5 b, the first photovoltaic unit layer 3 is formed via the first electrode 17, and the second photovoltaic power is generated by the connection electrode 19. The unit layer 5 is connected in parallel. Here, the first electrode 17 is SnO having no absorption in the sensitivity wavelength region of the second photovoltaic unit layer 5.₂For example, a transparent conductive material such as metal or a comb electrode made of metal is used. The first photovoltaic unit layer 3 includes a top n layer 15n made of n-type amorphous silicon, a top i layer 15i made of i-type amorphous silicon, and a top p layer made of p-type amorphous silicon carbide. 15p is comprised by the laminated body laminated | stacked one by one, and each layer can be formed by plasma CVD method. On the top p layer 15p, a second electrode 21 having a laminated structure of an ITO whole surface electrode and a metal comb electrode is formed.
[0047]
As shown in the figure, the second photovoltaic unit layer 5 in which one pn junction 5b and the other pn junction 5a are connected in series in the surface direction on the substrate 1, and the first light A plurality of unit elements 7 having a structure in which the electromotive force unit layer 3 is superimposed are arranged in the surface direction of the substrate 1, and the first electrodes 17 of the first and second photovoltaic unit layers 3, 5 are arranged. The connection electrode 19 connecting 17 is connected to the second electrodes 21 and 21 of the first and second photovoltaic unit layers 3 and 5 of the adjacent unit element 7 and is further taken out at both ends. 35 and 35 are formed to form a parallel integrated solar cell 23.
[0048]
The structure shown in FIGS. 6 and 7 is obtained by connecting two pin junctions and pn junctions constituting the second photovoltaic unit layer 5 in series in the plane direction of the substrate 1. It is. Therefore, it is not necessary to determine the film thickness of the first and second bottom i layers 9i, 11i and the n layers 9n, 11n under the restriction of the light transmission characteristics, and the second photovoltaic layer 5 The film thickness can be freely set to obtain the maximum conversion efficiency.
[0049]
The second photovoltaic unit layer 5 in the structure shown in FIGS. 6 and 7 can be regarded as an integrated thin film polycrystalline silicon solar cell formed on the substrate 1 as described above. This will be described with reference to FIG.
FIG. 8 is a partial cross-sectional view schematically showing the manufacturing process of the integrated thin film polycrystalline silicon solar cell in order. Hereinafter, the case of a p-i-n junction will be described as an example.
First, a metal electrode 38 for connection extraction is patterned on the glass substrate 1, and p made of polycrystalline silicon crystallized by irradiating an excimer laser on p-type amorphous silicon thereon.⁺Layer 36p⁺And split by laser fusing to produce first and second p⁺Layers 9p ′ and 11p ′ are formed (step A). The metal electrode 38 is preferably a refractory metal such as chromium, molybdenum, or tungsten.⁺It may be formed in a part of the layer region or p⁺It may be a comb type that can cover the entire layer.
Next, the first and second p⁺Over the layers 9p ′ and 11p ′, an i layer 36i made of i-type polycrystalline silicon by the plasma CVD method, an n layer 36n made of n-type microcrystalline silicon by the plasma CVD method, and the second electrode 21 are formed. ITO and SnO₂The whole surface electrode 36e of the transparent conductive material such as is sequentially laminated (step B).
Subsequently, by irradiating a condensed excimer laser beam or YAG laser beam in an oxygen atmosphere, parts of the laminate other than the metal electrode 38 are partially melted to form the divided grooves 37, and two p -In junctions 5a and 5b are formed. At this time, due to the thermal action due to laser fusing and the presence of excess oxygen in the atmosphere, SiO functions as a pn short prevention layer on the end faces of the pin junctions 5a and 5b.₂The guard ring layer 33 is formed (step C).
Then, a series connection electrode 39 is formed between the exposed portion of the metal electrode 38 to the dividing groove 37 and the second electrode 21 of the adjacent pin junction 5b, thereby completing the series connection ( Step D). It is sufficient that the series connection electrode 39 is in contact with the second electrode 21. However, in order to increase current collection efficiency, a metal electrode formed in a comb shape over the entire surface of the second electrode 21, ITO, SnO₂The whole surface electrode by transparent conductive materials, such as, may be sufficient.
As described above, the manufacturing process of the integrated thin-film polycrystalline silicon solar cell that can be applied to the present invention is not limited to the use of a laser for patterning, but patterning and pin or pn. The card ring is formed on the joining end face at the same time when the dividing groove 37 is melted by laser.
[0050]
In the above embodiment, an example in which a silicon-based semiconductor material is used for the first and second photovoltaic unit layers 3 and 5 is shown. However, for example, optical germanium such as silicon germanium or other compound semiconductor materials is optically forbidden. A combination of a plurality of materials having different band widths may be used, and the insulating layer 13 may be exemplified by SiO₂Besides Y₂O_ThreeAnd Si_ThreeN_FourEtc., and as the transparent conductive material, the exemplified SnO₂In addition, ITO or ZnO may be used, and is not particularly limited to the present embodiment.
In addition, when amorphous silicon is used for the first photovoltaic unit layer, a higher output characteristic can be obtained by using a p-layer on the light incident side. This is because i-type amorphous silicon obtained under normal film-forming conditions is slightly shifted to n-type. In other words, depending on the film quality variation, the n layer may function as an ohmic contact layer with respect to the i layer. Therefore, amorphous silicon has excellent absorption characteristics for short-wavelength light. This is because it is desirable that an excellent p / i interface exists.
[0051]
1 and 4 to 7, a metal thin film having a high reflectance such as aluminum or silver may be formed on the back surface of the glass substrate 1, that is, the surface 1 </ b> B opposite to the light incident side. Thereby, the light confinement effect by back surface reflection can be acquired, and the conversion efficiency can be improved further.
[0052]
Furthermore, it is desirable in terms of ensuring reliability to form a passivation layer on the uppermost part on the light incident side.
[0053]
【The invention's effect】
  As described above, the present invention provides a plurality of photovoltaic unit layers having different optical forbidden band widths on a substrate so that the optical forbidden band width of the photovoltaic unit layers positioned on the light incident side is the widest. Electrically connected in parallelAs one unit elementSuperposed and the output voltage of each photovoltaic unit layer is approximately equal, andThe unit elementAre electrically connected in series in the substrate surface direction. Therefore,For each layerConnected in seriesConnected in parallel at the endsUnlike the conventional tandem structure, the current that can be extracted is the sum of the output currents from the upper and lower layers, so that there is no current limitation as in the conventional case, and both current gain and voltage gain are excellent. In addition, as described above, since the output voltages of the plurality of photovoltaic unit layers constituting one unit element are substantially equal and the unit elements are connected in series on the substrate, the upper and lower layers are connected in series. Since it is not necessary to set the ratio of numbers based on the ratio of output voltages as in the prior art, the degree of design freedom increases.
  Further, the plurality of photovoltaic unit layers are constituted by a first photovoltaic unit layer having an amorphous photoactive layer and a second photovoltaic unit layer having a crystalline photoactive layer. And since the 1st photovoltaic unit layer is provided in the incident side of light, it can have a high sensitivity with respect to a wide wavelength range, and implement | achieves a significant improvement in conversion efficiency. In particular, a first photovoltaic unit layer of amorphous silicon having one junction and a second photovoltaic unit layer of polycrystalline silicon in which two junctions are connected in series are connected to the first light. If the electromotive force unit layers are superimposed so as to be on the light incident side, the output voltages of the two photovoltaic unit layers are substantially the same. Therefore, high conversion efficiency without loss can be obtained, and when connecting in series on the substrate as described above, it is not necessary to design the number of series of two photovoltaic unit layers, and the degree of design freedom is improved. .
[0054]
In addition, when a defect due to short or open occurs in the unit of the unit element or photovoltaic unit layer, the connection electrodes on both sides of the unit element having the defect are short-circuited with a conductive paste or the like, thereby providing an integrated solar cell. Repair can be easily performed so that a desired output current can be obtained. 4 to 7, for example, a small amount of conductive paste or the like is applied between the light incident side electrode of the first photovoltaic unit layer and the connection electrode. Can be performed by a very simple method, such as melting short-circuiting with a laser shot. At this time, the output voltage decreases by the amount of the unit element in which there is a defect, but it can be used if it is at a level satisfying the specifications, so it greatly contributes to the improvement of the manufacturing yield, and consequently the cost reduction effect of the solar cell. appear. This is because the solar cell structure of the present invention is measured on two connection electrodes located on both sides of each unit element before forming a passivation layer in the manufacturing process, as shown in FIGS. This is because the electric characteristics of the individual unit elements can be individually measured by applying the probe for use. If this is the above-mentioned conventional example 1, it is difficult to determine in which part of the first and second photovoltaic elements the defect has occurred, and therefore there is an open defect even at one place. The solar cell becomes defective. Therefore, it can be said that the solar cell of this invention has the cost advantage outstanding with respect to the prior art example.
Further, as described above, since the solar cell of the present invention can use a laser for pattern formation and guard ring layer formation, the laser device can be used in both the manufacturing process and the repair process, resulting in high yield and low equipment cost. A production line can be constructed.
[0055]
When the photovoltaic unit layer located on the substrate side has two or more p-i-n or p-n junctions, if these are formed in a superimposed manner, the manufacturing process can be simplified and the cost can be reduced. Further, since the output voltage per unit element length in the series direction is increased, a compact and high-voltage solar cell element can be obtained.
On the other hand, when these junctions are arranged side by side in the plane direction of the substrate and connected in series, the respective film thicknesses can be set independently so that the output is maximized, so that a higher output is easily obtained. In addition, since the output current does not fluctuate so much even if the film thickness varies slightly, a solar cell with little output variation can be obtained.
[0056]
And even if amorphous silicon is used for the first photovoltaic unit layer, it has extremely high reliability with almost no photodegradation, and has a high conversion efficiency that could not be obtained in the past. I was able to achieve it. Thus, it can be said that the present invention is a great breakthrough for the practical application of amorphous silicon solar cells.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional explanatory view of a main part showing a stacked structure of a parallel integrated solar cell of the present invention.
FIG. 2 is an explanatory diagram showing the wavelength dependence of absorption coefficients of various silicon materials.
FIG. 3 is an explanatory diagram showing spectral sensitivity characteristics of each photoactive layer in a specific example of the present invention.
FIG. 4 is a cross-sectional explanatory diagram of Embodiment 1 of the present invention.
FIG. 5 is a cross-sectional explanatory diagram of Embodiment 2 of the present invention.
FIG. 6 is a cross-sectional explanatory view of another embodiment of the present invention.
FIG. 7 is a cross-sectional explanatory view of another embodiment of the present invention.
FIG. 8 is an explanatory diagram showing an example of a process for forming an integrated thin film polycrystalline silicon solar cell.
FIG. 9 is a cross-sectional explanatory view of a conventional parallel integrated solar cell.
FIG. 10 is a cross-sectional explanatory diagram of a conventional parallel solar cell.
[Explanation of symbols]
1 Glass substrate
3 First photovoltaic unit layer
5 Second photovoltaic unit layer
7 Unit element
9p⁺Bottom p⁺Layer, first bottom p⁺layer
9p Bottom p layer
9p 'first p⁺layer
9i bottom i layer, first bottom i layer
9i 'first i layer
9n bottom n layer, first bottom n layer
9n ′ first n layer
11p middle p layer, second bottom p layer
11p 'second p⁺layer
11i Middle i layer, second bottom i layer
11i ′ second i layer
11n Middle n layer, second bottom n layer
11n ′ second i layer
13 Insulating layer
15p top p layer
15i Top i layer
15n Top n layer
17 First electrode
19 Connection electrode
21 Second electrode
23 Parallel integrated solar cells
25 Intermediate electrode layer
27 Element isolation groove
29 First connection step
31 Second connecting step
33 Guard ring layer
35 Extraction electrode
36pp layer
36i i layer
36n n layers
37 Dividing groove
38 metal electrodes
39 Electrode for series connection
40 First unit power generation membrane
42 First photovoltaic element
44 Second unit power generation membrane
46 Second photovoltaic element
48, 50 Amorphous solar cell element
52 substrates

Claims (6)

A plurality of photovoltaic unit layers having at least one pin or pn junction and having different optical forbidden band widths have an optical forbidden band width of the photovoltaic unit layers positioned on the light incident side. It is laminated on the substrate so that the output voltage of each of the photovoltaic unit layers is almost equal, and the laminated photovoltaic unit layers are electrically connected in parallel, and A parallel integrated solar cell in which two unit elements are formed, and a plurality of the unit elements are arranged in parallel in the substrate surface direction and are electrically connected in series. The plurality of photovoltaic unit layers are a first photovoltaic unit layer having an amorphous photoactive layer and a second photovoltaic unit layer having a crystalline photoactive layer, The parallel integrated solar cell according to claim 1, wherein the photovoltaic unit layer is provided on the light incident side. The substrate is a glass substrate, and the plurality of photovoltaic unit layers includes a first photovoltaic unit layer having an amorphous silicon-based photoactive layer, and a second photovoltaic unit-based photoactive layer. 2. A photovoltaic unit layer, wherein the second photovoltaic unit layer is formed on the glass substrate, and the first photovoltaic unit layer on the light incident side is formed thereon. The parallel integrated solar cell described. The plurality of photovoltaic unit layers are a first photovoltaic unit layer having an amorphous silicon-based photoactive layer and a second photovoltaic unit layer having a crystalline silicon-based photoactive layer, Further, the second photovoltaic unit layer has a tandem structure in which two pn or pn junctions are connected in series, and the first photovoltaic unit layer is the uppermost part on the light incident side. And a first photovoltaic unit layer is provided on each of the plurality of second photovoltaic unit layers arranged in the plane direction on the substrate, and the first and second photovoltaic units are provided. A plurality of unit elements composed of power unit layers are configured, and a connection electrode connecting the first electrodes on the one conductivity type side of the first and second photovoltaic unit layers is connected to the adjacent unit element. The plurality of unit elements are electrically connected by being connected to the second electrode on the opposite conductivity type side of the first and second photovoltaic unit layers. Connected in series, according to claim 2 or 3 parallel integrated solar cell according to. The parallel integrated solar cell according to claim 3 or 4, wherein the light incident side of the first photovoltaic unit layer is a p layer. 6. The parallel integrated solar cell according to claim 3, wherein the substrate is a glass substrate, and a metal thin film having a high reflectance is formed on a surface opposite to the light incident side of the glass substrate.

Images