JP2004111742A - Solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell that is improved in power generation efficiency than the conventional solar cell by making external light, such as the sunlight etc., efficiently incident to a photoelectric conversion layer by considering the incident angle of the light and, at the same time, by preventing the liberation of the light rays reflected on or in the conversion layer to the outside as much as possible. <P>SOLUTION: A light incident-side first transparent body 8 having a refractive index which is larger than that of air and smaller than that of a solar cell element-side second transparent body 3 is provided on the light incident side of a group 4 of cylindrical light condensing curved surfaces. In this way, the incident angle of the incident light 7 to the group 4 can be made smaller. Consequently, the luminous flux of the incident light 7 condensed to a group 6 of linear slit-like light transmissive-holes can be narrowed down and the quantity of the light introduced between a light reflecting layer 5 and the photoelectric conversion layer 2 can be increased. <P>COPYRIGHT: (C)2004,JPO

Description

【０１２０】
表１は、実施例１の太陽電池について、直線スリット状光透過孔群６の形成位置、すなわち、太陽電池素子側第２透明体３の厚さｄを変えた場合において、光の入射角Ｑとともに発電効率がどのように変化するかを調べた結果である。比較例１については、光入射側第１透明体８が存在しないため、シリンドリカル状集光曲面群４の焦点距離が２０ｍｍとなっており、太陽電池素子側第２透明体３の厚さを、シリンドリカル状集光曲面群４の焦点距離と同じ２０ｍｍとした。
【０１２１】
また、実施例１においては、シリンドリカル状集光曲面群４の焦点距離３４ｍｍよりも、太陽電池素子側第２透明体３の厚さｄが薄い範囲において調査を行った。光源としては、太陽光シミュレーターを用い、１００ｍＷ／ｃｍ^２の強度の光を入射角Ｑを変えて照射した。
【０１２２】
また、表１は、発電効率調査時に、並べて配置した比較例０１の太陽電池の開放電圧Ｖ及び短絡電流Ｉを１００％として、実施例１及び比較例１の太陽電池の開放電圧Ｖと短絡電流Ｉの大きさを比較例０１と比較した結果を示している。
【０１２３】
比較例１においては、入射角Ｑ＝０°の場合、全ての入射光が直線スリット状光透過孔群６に集光されるため、比較例０１の太陽電池よりも高い発電効率を実現することができている。しかし、入射角が大きくなることにより、発電効率が急激に低下し、入射角Ｑ＝８０°においては、比較例０１の２０％程度の開放電圧と短絡電流しか得られないことがわかる。
【０１２４】
次に、実施例１において、太陽電池素子側第２透明体３の板厚ｄをシリンドリカル状集光曲面群４の焦点距離Ｆと等しくしたｄ＝３４ｍｍの場合、比較例１に比べると、入射角が大きくなった場合において、発電効率が大幅に改善されていることがわかる。また、Ｑ＝８０°の場合に、比較例０１の太陽電池と比べて僅かに発電効率が劣化しているが、発電量が大きくなる時間帯、すなわち、入射角が小さいＱ＝０°やＱ＝４０°において、高い発電効率が実現されており、１日のトータルの発電量を考えると、比較例０１の太陽電池に比べてより多くの発電量を得ることができた。
【０１２５】
さらに、板厚ｄを変えた太陽電池について調査した結果、表１に示すように、板厚ｄを２２ｍｍ以上３２ｍｍ以下とすることにより、全ての入射角において、比較例０１よりも大きな開放電圧と短絡電流を得ることが可能であることを確認した。
【０１２６】
太陽電池素子側第２透明体３の板厚ｄが１８ｍｍとさらに薄くなると、発電量が大きくなる時間帯、すなわち、入射角が小さい範囲において、直線スリット状光透過孔群６へと集光される光が減少し、開放電圧及び短絡電流が低下することになる。これは、入射角が小さい範囲では、直線スリット状光透過孔群６の位置が、集光位置よりシリンドリカル状集光曲面群４に近づき過ぎるため、集光される前の広がった状態の光束が、直線スリット状光透過孔群６を照射することになるからである。
【０１２７】
このように、焦点距離Ｆが３４ｍｍであるのに対して、板厚ｄが２２ｍｍ（１１Ｆ／１７）以上、３２ｍｍ（１６Ｆ／１７）以下の範囲において、すべての入射角の範囲において、比較例０１よりも大きな開放電圧と短絡電流が得られる。
【０１２８】
次に、板厚ｄを最適位置、すなわち、２８ｍｍの位置に固定して、直線スリット状光透過孔群６のスリット幅ＷＳを変えて、開放電圧Ｖと短絡電流Ｉとを調査した結果を表２に示す。
【０１２９】
【表２】

【０１３０】
表２に示すように、シリンドリカル状集光曲面群４の幅Ｗが１２ｍｍであるのに対して、スリット幅ＷＳを１．５ｍｍ（Ｗ／８）以上とし、８．０ｍｍ（２Ｗ／３）以下とすることにより、全ての入射角の範囲で、比較例０１よりも大きな開放電圧Ｖと短絡電流Ｉが得られた。
【０１３１】
スリット幅ＷＳがＷ／８より狭くなると、集光された光の一部が光反射層５により反射され、太陽電池素子に到達しなくなるため、発電効率の低下につながる。また、スリット幅ＷＳが２Ｗ／３より広くなると、直線スリット状光透過孔群６から入射した光が、再度、直線スリット状光透過孔群６から放射され、多重反射の効率が低下するため、発電効率の低下につながる。
【０１３２】
以上のように、本発明の太陽電池においては、シリンドリカル状集光曲面群４の焦点距離をＦとして、シリンドリカル状集光曲面群４の表面から直線スリット状光透過孔群６までの距離（ｄ）を、少なくとも、（１１Ｆ／１７）以上、（１６Ｆ／１７）以下とすることが好ましい。また、シリンドリカル状集光曲面群４の幅をＷとして、直線スリット状光透過孔群６のスリット幅ＷＳを（Ｗ／８）以上、（２Ｗ／３）以下とすることが望ましい。
【０１３３】
ところで、本実施例においては、太陽電池素子側第２透明体３と太陽電池素子との間の外縁部分にスペーサを設け、両者を所定の間隔で固定配置した構成について説明した。しかし、それに限定されず、紫外線硬化樹脂等の透明接着剤を用いて、太陽電池素子側第２透明体３と太陽電池素子とを接着固定してもよい。これにより、より強固に集光素子と太陽電池素子とを固定することが可能となり、太陽電池の信頼性が向上する。
【０１３４】
ここで、太陽電池素子の光電変換層２と光反射層５との間で安定した多重反射を実現するためには、光電変換層２により反射された光が、すぐに光透過孔群６から漏れ出さないように、該透明接着剤層の層厚を２ｍｍ以上とすることが望ましい。また、紫外線硬化樹脂が厚くなり過ぎると、樹脂硬化のための時間が長くなり、太陽電池製造のスループットが低下することになる。したがって、紫外線硬化樹脂層の層厚としては、１５ｍｍ以下とすることが望ましい。
【０１３５】
また、蛍光性微粒子を分散した紫外線硬化樹脂を用いて、太陽電池素子側第２透明体３と太陽電池素子とを接着固定することにより、さらに発電効率を高くすることが可能となる。例えば、粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を、紫外線硬化樹脂に１０体積％含有させ、太陽電池素子側第２透明体３と太陽電池素子とを、５ｍｍ厚の該紫外線硬化樹脂を用いて接着固定した太陽電池を作製した。この蛍光粒子は、光電変換に利用されない波長４００ｎｍ近傍の光を、光電変換に利用される波長６００ｎｍ近傍の光に変換し、蛍光粒子から発生する波長６００ｎｍ近傍の光が、太陽電池素子の光反射層５と光電変換層２との間で吸収、一部反射を繰り返すことにより、太陽電池の発電効率を高くすることが可能となる。
【０１３６】
蛍光粒子を含有しない紫外線硬化樹脂を用いて、集光素子と太陽電池素子とを接着固定した太陽電池と、蛍光粒子を含有した紫外線硬化樹脂を用いて、集光素子と太陽電池素子とを接着固定した太陽電池とに対して、太陽光シミュレーターを用いて、１００ｍＷ／ｃｍ^２の強度の光を、入射角Ｑを０°、４０°、８０°として入射させ、両者の開放電圧Ｖと短絡電流Ｉを比較した結果、蛍光粒子を含有させることにより、全ての入射角において、開放電圧Ｖが約１３％大きくなり、短絡電流Ｉが約１１％大きくなることが確認された。
【０１３７】
なお、実施例１に記載の太陽電池においては、図２に示すようにステンレス基板１上に、電極金属層９、多結晶Ｓｉ半導体層１０、多結晶Ｓｉ半導体層１１、多結晶Ｓｉ半導体層１２、集電電極１３、導電性透明膜１４を形成した多結晶Ｓｉ太陽電池を用いたが、これに限られるものではない。すなわち、太陽電池素子として、図１８に示す非晶質Ｓｉ太陽電池素子を用いることも可能であり、また、さらに発電効率を上げるため、図１７に示す多結晶半導体で構成したｐｎ接合と、図１８に示す非晶質半導体で構成したｐｉｎ接合とを積層したタンデム構造太陽電池素子を用いることも可能である。
【０１３８】
なお、実施例１に記載の太陽電池においては、集光素子として、透明フッ素樹脂からなる光入射側第１透明体８を用い、鉛ガラスからなる太陽電池素子側第２透明体３を用いたが、これに限られるものではない。すなわち、空気の屈折率をｎ０とし、光入射側第１透明体８の屈折率をｎ１とし、太陽電池素子側第２透明体３の屈折率をｎ２とすれば、ｎ０＜ｎ１＜ｎ２となるような材料により、光入射側第１透明体８と太陽電池素子側第２透明体３を構成することにより、光入射側第１透明体８は、シリンドリカル状集光曲面群４に対する入射角を小さくする集光補助層として機能することが可能である。
【０１３９】
なお、実施例１に記載の太陽電池においては、シリンドリカル状集光曲面群４として、曲率半径が一定な集光曲面群を用いたが、これに限られるものではない。直線スリット状光透過孔群６へと効率良く太陽光を集光することが可能であれば、曲率半径が異なる集光曲面を組み合わせて配列することも可能である。
【０１４０】
なお、実施例１に記載の太陽電池においては、蛍光粒子として、粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を用いた例について記載したが、これに限られるものではない。
【０１４１】
例えば、蛍光粒子として、粒径２〜２０μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの性蛍光粒子を使用することにより、２００〜４５０ｎｍの波長の光を吸収し、６２５ｎｍの波長の光を放射させることが可能である。また、Ｅｒ^３＋イオンを含有した酸化フッ化物系結晶化ガラスを用いることにより、８００ｎｍ近傍の波長の光を吸収し、５５０〜６６０ｎｍの波長の光を放射させることが可能である。
【０１４２】
これら以外の蛍光材料として、酸化ストロンチウムと酸化アルミニウムからなる化合物に希土類元素のユウロピウム（Ｅｕ）とジスプロシウム（Ｄｙ）を添加したＳｒＡｌ_２Ｏ_４：Ｅｕ，Ｄｙや、Ｓｒ_４Ａｌ_１４Ｏ_２５：Ｅｕ，Ｄｙや、ＣａＡｌ_２Ｏ_４：Ｅｕ，Ｄｙや、ＺｎＳ：Ｃｕ等の蛍光材料を用いることも可能である。
【０１４３】
また、シアニン系色素、ピリジン系色素、ローダミン系色素等の有機色素を含有させることによっても、同様に、短波長の光を長波長の光に変換することが可能であり、発電効率を高くすることが可能である。
【０１４４】
さらに、これらの蛍光材料を任意の組み合わせで複数同時に用いることにより、より高い発電効率を得ることが可能である。
【０１４５】
［実施例２］
本発明の実施例２として図１０に示す太陽電池を説明すれば以下の通りである。
【０１４６】
実施例２の太陽電池は、実施例１に記載の光入射側第１透明体８と太陽電池素子側第２透明体３と光透過孔群６を有する光反射層５で構成された集光素子と、基板１及び光電変換層２で構成された太陽電池素子との間に、透明基板１７が設けられた構成となっている。
【０１４７】
入射側第１透明体８から入射した太陽光は、シリンドリカル状集光曲面群４により、直線スリット状光透過孔群６に集光され、透明基板１７を透過した後、光電変換層２へと入射する。続いて、光電変換層２からの反射光が、光反射層５により反射され、再度光電変換層２へと再入射する。これにより、光反射層５と光電変換層２との間で、入射光７の多重反射が実現し、発電効率を高くすることが可能となる。
【０１４８】
実施例１においては、集光素子と太陽電池素子とを直接紫外線硬化樹脂で固定したため、紫外線硬化樹脂の厚さを少なくとも２ｍｍ以上まで厚くする必要があり、紫外線硬化樹脂を硬化するために長い時間を必要とした。これに対し、実施例２においては、透明基板１７の板厚を調整することにより、集光素子と太陽電池素子との間隔を制御することが可能となるので、紫外線硬化樹脂の層厚を薄くすることができる。
【０１４９】
例えば、板厚５ｍｍのガラス板を透明基板１７として採用し、集光素子と透明基板１７との間と、太陽電池素子と透明基板１７との間とに、それぞれ、２０μｍ厚の紫外線硬化樹脂層を形成し、集光素子と透明基板１７と太陽電池素子とを接着固定した太陽電池について、実施例１と同様な発電効率の調査を行った。その結果、実施例１とほぼ同様な開放電圧Ｖと短絡電流Ｉとが得られ、実施例２の構成においても、太陽電池の発電効率を高くすることができた。
【０１５０】
次に、上記透明基板１７として、粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を、１５体積％含有させた透明基板１７を用いた太陽電池を作製した。
この蛍光粒子は、光電変換に利用されない波長４００ｎｍ近傍の光を、光電変換に利用される波長６００ｎｍ近傍の光に変換する。そして、蛍光粒子から発生する波長６００ｎｍ近傍の光が、集光素子と太陽電池素子との間で吸収、一部反射を繰り返すことにより、太陽電池の発電効率を高くすることが可能となる。
【０１５１】
蛍光粒子を含有しない透明基板１７を用いた太陽電池と、蛍光粒子を含有した透明基板１７を用いた太陽電池に対して、太陽光シミュレーターを用いて、１００ｍＷ／ｃｍ^２の強度の光を、入射角Ｑを０°、４０°、８０°として入射させ、両者の開放電圧Ｖと短絡電流Ｉを比較した。その結果、蛍光粒子を含有した透明基板１７を用いることにより、全ての入射角において、開放電圧Ｖが約２０％大きくなり、短絡電流Ｉが約１６％大きくなることが確認された。
【０１５２】
次に、集光素子と透明基板１７と太陽電池素子とを接着固定するための紫外線硬化樹脂に粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を、１０体積％含有させた実施例２の構成の太陽電池を作製した。
【０１５３】
蛍光粒子を含有しない紫外線硬化樹脂を用いて、集光素子と透明基板１７と太陽電池素子とを接着固定した太陽電池と、蛍光粒子を含有した紫外線硬化樹脂を用いて、集光素子と透明基板１７と太陽電池素子とを接着固定した太陽電池とに対して、太陽光シミュレーターを用いて、１００ｍＷ／ｃｍ^２の強度の光を、入射角Ｑを０°、４０°、８０°として入射させ、両者の開放電圧Ｖと短絡電流Ｉを比較した。その結果、紫外線硬化樹脂に蛍光粒子を含有させることにより、全ての入射角において、開放電圧Ｖが約８％大きくなり、短絡電流Ｉが約６％大きくなることが確認された。
【０１５４】
ここでは、透明基板１７と紫外線硬化樹脂に対して、独立に蛍光粒子を含有させた構成について調査したが、透明基板１７と紫外線硬化樹脂の両方に蛍光粒子を含有させた場合においても、さらに開放電圧Ｖと短絡電流Ｉとを大きくすることが可能である。
【０１５５】
なお、実施例２に記載の太陽電池おいては、実施例１に記載の太陽電池と同様の太陽電池素子、集光素子、シリンドリカル状集光曲面群、蛍光粒子を用いたが、実施例１に記載の通りこれに限られるものではない。
【０１５６】
［実施例３］
本発明の実施例３として図１１に示す太陽電池を説明すれば以下の通りである。
【０１５７】
実施例３の太陽電池は、光入射側第１透明体８と太陽電池素子側第２透明体３とで構成されるシリンドリカル状集光曲面群４を有する集光素子と、光透過孔群６を有する光反射層５が設けられた透明基板１８と、基板１及び光電変換層２を有する太陽電池素子とで構成されている。すなわち、光透過孔群６を有する光反射層５が、太陽電池素子側第２透明体３の光出射側の表面ではなく、透明基板１７の光入射側の表面に形成されたことを特徴としている。
【０１５８】
透明基板１８として、板厚５ｍｍのガラス板を採用した。この場合、光入射側第１透明体８から入射した入射光７は、シリンドリカル状集光曲面群４により、透明基板１８上に形成された直線スリット状光透過孔群６に集光され、透明基板１８を透過した後、光電変換層２へと入射する。続いて、光電変換層２からの反射光は、光反射層５により反射され、再度光電変換層２へと再入射する。
【０１５９】
この場合も、実施例１と同様に、シリンドリカル状集光曲面群４と直線スリット状光透過孔群６を有する光反射層５との距離を最適化することにより、実施例１と同様な、開放電圧Ｖと短絡電流Ｉを得ることができた。
【０１６０】
また、実施例１及び実施例２においては、シリンドリカル状集光曲面群４が形成された太陽電池素子側第２透明体３の太陽電池素子側の片面に、直線スリット状光透過孔群６を有する光反射層５を形成した。このため、光反射層５の形成時や、光透過孔群６のパターニング時に、集光曲面群４に傷等の欠損が発生し、集光効率が低下する原因となった。
【０１６１】
これに対して、本実施例の構成によれば、シリンドリカル状集光曲面群４を有する集光素子と、直線スリット状光透過孔群６及び光反射層５を有する透明基板１８とを別々に作製することができる。これにより、集光素子に傷等の欠損が発生する確率が低下し、再現性良く発電効率の高い太陽電池を作製することが可能となる。
【０１６２】
次に、上記透明基板１８として、粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を、１５体積％含有させた透明基板１８を用いた太陽電池を作製した。
この蛍光粒子による発電効率向上作用は、前記実施例で説明したとおりである。
【０１６３】
蛍光粒子を含有しない透明基板１８を用いた太陽電池と、蛍光粒子を含有した透明基板１８を用いた太陽電池に対して、太陽光シミュレーターを用いて、１００ｍＷ／ｃｍ^２の強度の光を、入射角Ｑを０°、４０°、８０°として入射させ、両者の開放電圧Ｖと短絡電流Ｉを比較した。その結果、蛍光粒子を含有した透明基板１８を用いることにより、全ての入射角において、開放電圧Ｖが約２１％大きくなり、短絡電流Ｉが約１８％大きくなることが確認された。
【０１６４】
次に、透明基板１８と太陽電池素子とを接着固定する紫外線硬化樹脂に粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を、１０体積％含有させた実施例３の構成の太陽電池を作製した。
【０１６５】
さらに、集光素子と透明基板１８とを接着固定する場合、紫外線硬化樹脂の層は、光透過孔群６よりも光入射側に存在する。このため、蛍光粒子を含有しない紫外線硬化樹脂を用いる必要がある。なぜなら、集光素子と透明基板１８とを接着固定する紫外線硬化樹脂に蛍光粒子を含有させると、入射光が蛍光粒子によって散乱され、光透過孔群６への集光効率が低下することになるからである。
【０１６６】
性能測定では、蛍光粒子を含有しない紫外線硬化樹脂を用いて、透明基板１８と太陽電池素子とを接着固定した太陽電池と、蛍光粒子を含有した紫外線硬化樹脂を用いて、透明基板１８と太陽電池素子とを接着固定した太陽電池とを比較した。すなわち、太陽光シミュレーターを用いて、１００ｍＷ／ｃｍ^２の強度の光を、入射角Ｑを０°、４０°、８０°として、それぞれの太陽電池に入射させ、両者の開放電圧Ｖと短絡電流Ｉを比較した。その結果、紫外線硬化樹脂に蛍光粒子を含有させることにより、全ての入射角において、開放電圧Ｖが約８％大きくなり、短絡電流Ｉが約６％大きくなることが確認された。
【０１６７】
ここでは、透明基板１８と紫外線硬化樹脂に対して、蛍光粒子を含有させた構成について別々に調査したが、透明基板１８と紫外線硬化樹脂の両方に蛍光粒子を含有させることで、開放電圧Ｖと短絡電流Ｉを一層大きくすることが可能である。
【０１６８】
なお、実施例３に記載の太陽電池においては、実施例１と同様の太陽電池素子、集光素子、シリンドリカル状集光曲面群、蛍光粒子を用いたが、実施例１に記載の通りこれに限られるものではない。
【０１６９】
［実施例４］
本発明の実施例４として図１２に示す太陽電池を説明すれば以下の通りである。
【０１７０】
本実施例４の太陽電池は、実施例１において記載した集光素子、すなわち、シリンドリカル状集光曲面群４を有する光入射側第１透明体８及び太陽電池素子側第２透明体３と、光透過孔群６を有する光反射層５とで構成された集光素子と、太陽電池素子用透明基板１９及び光電変換層２０を有する太陽電池素子とで構成されている。実施例１との違いは、本実施例の太陽電池素子用透明基板１９及び光電変換層２０の光進行方向に対する積層順序が、実施例１の基板１及び光電変換層２の積層順序と逆になっていることである。
【０１７１】
上記の構成では、光入射側第１透明体８から入射した光は、シリンドリカル状集光曲面群４により、直線スリット状光透過孔群６に集光され、太陽電池素子用透明基板１９を透過し、光電変換層２０へと入射する。一方、光電変換層２０からの反射光は、光反射層５により反射され、再度光電変換層２０へと再入射する。
【０１７２】
本実施例４の太陽電池素子は、図１３に示すような構成であり、次のようにして作製した。
【０１７３】
ガラス製の太陽電池素子用透明基板１９上に、膜厚３０ｎｍのＳｎＯ_２透明導電層２１を反応性スパッタリングにより形成した後、遮蔽マスクを基板１９上に形成した透明導電層２１表面に装着した状態で、ＡｌＴｉ合金ターゲットを用いたスパッタリングにより、膜厚１００ｎｍのＡｌ_０．９５Ｔｉ_０．０５合金からなる、幅０．１ｍｍ、間隔５ｍｍのくし型集電電極２２を形成した。
【０１７４】
次に、ｐ型不純物ドープ半導体層であるｐ層２３、真性半導体であるｉ層２４、ｎ型不純物ドープ層であるｎ層２５がこの順に積層された光電変換層をプラズマＣＶＤ装置による気相成長法で形成した。各半導体層は、それぞれ、ＳｉＨ_４ガス・Ｈ_２ガス・ＣＨ_４ガス・Ｂ_２Ｈ_６ガスの混合ガスを用いて気相成長した膜厚１５ｎｍのａ−ＳｉＣ：Ｈのｐ層２３、ＳｉＨ_４ガス・Ｈ_２ガスの混合ガスを用いて気相成長した膜厚１００ｎｍのａ−Ｓｉ：Ｈのｉ層２４、ＳｉＨ_４ガス・Ｈ_２ガス・ＰＨ_３ガスの混合ガスを用いて気相成長した膜厚１５ｎｍのａ−Ｓｉ：Ｈのｎ層２５とした。
【０１７５】
上記のようにして各層形成した後、膜厚１００ｎｍのＡｌ_０．９５Ｔｉ_０．０５合金からなる光反射効果を有する電極金属層２６をスパッタリングにより形成した。最後に、紫外線硬化樹脂を電極金属層２６上に塗布し、電極金属層２６の保護膜２７として、太陽電池素子を完成させた。
【０１７６】
上記集光素子と太陽電池素子とを、実施例１と同様に、紫外線硬化樹脂を用いて接着固定して本実施例４の太陽電池とした。
【０１７７】
実施例４の太陽電池において光入射側第１透明体８を設けていない太陽電池を比較例４とし、また、集光素子を設けていない太陽電池素子のみの太陽電池を比較例０４として、実施例４の太陽電池の発電効率を実施例１と同様にして比較した。すなわち、実施例４の太陽電池素子側第２透明体３の板厚ｄを変えた場合において、光の入射角Ｑとともに発電効率がどのように変化するかを調べた。
【０１７８】
【表３】

【０１７９】
表３は、比較例０４の太陽電池素子の開放電圧Ｖと短絡電流Ｉとを、それぞれ１００％として、実施例４及び比較例４の太陽電池の開放電圧Ｖと短絡電流Ｉの大きさを比較例０４と比較した結果を示している。
【０１８０】
実施例４の集光素子は、実施例１と同じものであり、実施例４の太陽電池においても実施例１と同様な結果が得られていることがわかる。
【０１８１】
すなわち、シリンドリカル状集光曲面群４の焦点距離をＦとして、シリンドリカル状集光曲面群４の表面から直線スリット状光透過孔群６までの距離（ｄ）を、少なくとも、（１１Ｆ／１７）以上、（１６Ｆ／１７）以下とすることが好ましい。
【０１８２】
また、実施例１と同様に、蛍光性微粒子が分散した紫外線硬化樹脂を用いて、集光素子と太陽電池素子とを接着固定することにより、さらに発電効率を高くすることが可能となる。粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を、紫外線硬化樹脂に、１０体積％含有させ、集光素子と太陽電池素子とを、５ｍｍ厚の該紫外線硬化樹脂を用いて接着固定した太陽電池を作製した。
【０１８３】
そして、蛍光粒子を含有しない紫外線硬化樹脂を用いて、集光素子と太陽電池素子とを接着固定した太陽電池と、蛍光粒子を含有した紫外線硬化樹脂を用いて、集光素子と太陽電池素子とを接着固定した太陽電池とに対して、太陽光シミュレーターを用いて、１００ｍＷ／ｃｍ^２の強度の光を、入射角Ｑを０°、４０°、８０°として入射させ、両者の開放電圧Ｖと短絡電流Ｉを比較した。その結果、蛍光粒子を含有させることにより、すべての入射角において、開放電圧Ｖが１６％大きくなり、短絡電流Ｉが１４％大きくなることが確認された。
【０１８４】
また、実施例４においては、太陽電池素子用透明基板１９として、蛍光材料を含有した蛍光ガラスを用いることによっても、同様に発電効率を改善することが可能である。
【０１８５】
図１２に示す実施例４の太陽電池において、太陽電池素子用透明基板１９として、粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を、１５体積％含有させたガラス基板を用いて太陽電池を作製した。
【０１８６】
そして、蛍光粒子を含有しない太陽電池素子用透明基板１９を用いた太陽電池と、蛍光粒子を含有した太陽電池素子用透明基板１９を用いた太陽電池に対して、太陽光シミュレーターを用いて、１００ｍＷ／ｃｍ^２の強度の光を、入射角Ｑを０°、４０°、８０°として入射させ、両者の開放電圧Ｖと短絡電流Ｉを比較した。その結果、全ての入射角において、蛍光粒子を含有した太陽電池素子用透明基板１９を用いることにより、開放電圧Ｖが２０％大きくなり、短絡電流Ｉが１６％大きくなることが確認された。
【０１８７】
ここでは、太陽電池素子用透明基板１９と紫外線硬化樹脂に対して、それぞれ蛍光粒子を含有させた構成について別々に調査した。しかし、太陽電池素子用透明基板１９と紫外線硬化樹脂の両方に蛍光粒子を含有させることにより、開放電圧Ｖと短絡電流Ｉを一層大きくすることが可能である。
【０１８８】
以上の実施例においては、直線スリット状光透過孔群６を有する光反射層５が、太陽電池素子側第２透明体３の片面上に設けられた構成について説明したが、図１４に示すように、太陽電池素子用透明基板１９の光入射面に、直線スリット状光透過孔群６を有する光反射層５を設ける構成とした場合においても、同様に発電効率を向上させることが可能である。この場合、光反射層５よりも光電変換層２０側に存在する太陽電池素子用透明基板１９として、蛍光特性を有する基板を用いることにより、さらに高い発電効率を実現することができる。
【０１８９】
また、図１５に示すように、集光素子の太陽電池素子側第２透明体３と太陽電池素子の太陽電池素子用透明基板１９との間に、直線スリット状光透過孔群６を有する光反射層５を形成した透明基板２８を挿入し、集光素子と透明基板２８と太陽電池素子とを固定することによっても、同様に発電効率を向上させることが可能である。
【０１９０】
このような構成とすることにより、集光素子と光反射層５を有する透明基板２８と太陽電池素子とを別々に作製することが可能となり、太陽電池パネルの製造歩留まりを改善することができる。
【０１９１】
この場合、光反射層５よりも光電変換層２０側に存在する透明基板２８または太陽電池素子用透明基板１９として、蛍光特性を有する基板を用いることにより、さらに高い発電効率を実現することができる。また、紫外線硬化樹脂等の透明接着剤を用いて、集光素子と透明基板２８と太陽電池素子とを固定する場合、透明基板２８と太陽電池素子とを固定する透明接着剤に蛍光粒子を含有させることにより、より高い発電効率を実現することが可能となる。
【０１９２】
また、図１６に示すように、図１５における透明基板２８を上下逆転させ、太陽電池素子側に光反射層５が存在する構成としても、同様に発電効率を向上させることが可能である。
【０１９３】
なお、実施例４の太陽電池においては、太陽電池素子用透明基板１９に、透明導電層２１、くし型集電電極２２、ｐ型不純物ドープ半導体層であるｐ層２３、真性半導体であるｉ層２４、ｎ型不純物ドープ層であるｎ層２５、電極金属層２６、保護膜２７からなる非晶質Ｓｉ太陽電池を用いたが、これに限られるものではない。太陽電池素子として、多結晶Ｓｉ太陽電池素子を用いることも可能であり、また、さらに発電効率を上げるため、多結晶半導体で構成したｐｎ接合と、非晶質半導体で構成したｐｉｎ接合とを積層したタンデム構造太陽電池素子を用いることも可能である。
【０１９４】
なお、実施例４に記載の太陽電池においても、実施例１に記載の太陽電池と同様の集光素子、シリンドリカル状集光曲面群、蛍光粒子を用いたが、実施例１に記載の通りこれに限られるものではない。
【０１９５】
なお、特許請求の範囲には含めないが、図１、３、１０、１２に示すように、上記集光素子の片面であって、太陽電池素子側の上記第２透明体の上記集光領域に対向する光出射面に、光透過孔を有する光反射層が設けられている構成も、本発明に含まれる。
【０１９６】
また、この構成において、図１０に示すように、上記集光領域と光反射層とが設けられた上記集光素子と、上記太陽電池素子との間に透明基板を設けてもよい。
【０１９７】
さらに、上記太陽電池素子は、図１、３、１０、１１に示すように、透明基板上に光電変換層を設けた太陽電池素子であってよい。
【０１９８】
さらに、図１４に示すように、上記太陽電池素子の透明基板の光電変換層に対向する面に、上記光透過孔を有する光反射層が設けられていてもよい。
【０１９９】
上記の構成によれば、いずれにしても、集光領域により集光された光が、光透過孔を介して、集光素子に設けられた光反射層と太陽電池素子との間に入射するので、光電変換層と光反射層との間で多重反射が起きる。したがって、光電変換層に照射される光量が増大し、発電効率を高くすることが可能となる。
【０２００】
その上、上記太陽電池素子の透明基板上に、上記光電変換層と上記光反射層の両方を形成することが可能であり、必要最小限の基板枚数で、太陽電池を製造することが可能であり、太陽電池の低コスト化が実現するとともに、太陽電池の薄型化を実現することができる。
【０２０１】
さらに、図１１、１５、１６に示すように、上記集光素子と上記太陽電池素子との間に、透明基板が設けられており、該透明基板の片面に光透過孔が形成された光反射層を設けた構成も、本発明に含まれる。
【０２０２】
これにより、集光素子と太陽電池素子と光透過孔を有する光反射層が形成された透明基板とを別々に作製することが可能となり、製造プロセスにおいて発生する傷等の損傷が抑制され、高い発電効率を有する太陽電池を安定して製造することができる。
【０２０３】
また、本発明の太陽電池では、上記集光素子と上記太陽電池素子、または、上記集光素子と上記太陽電池素子と、それらの間に設けられた上記透明基板とが、透明接着剤により固定されていてもよい。
【０２０４】
したがって、上記集光素子と上記太陽電池素子、または、上記集光素子と上記透明基板と上記太陽電池素子とが、透明接着剤により強固に固定されることにより、太陽電池の強度を高くすることが可能となる。
【０２０５】
本発明は上述した各実施形態および実施例に限定されるものではなく、請求項に示した範囲で種々の変更が可能であり、異なる実施形態および実施例にそれぞれ開示された技術的手段を適宜組み合わせて得られる実施形態および実施例についても本発明の技術的範囲に含まれる。
【０２０６】
【発明の効果】
本発明に係る太陽電池は、以上のように、光電変換層を有する太陽電池素子と、空気より大きな屈折率を有する光入射側第１透明体および該光入射側第１透明体より大きな屈折率を有する太陽電池素子側第２透明体との間に集光領域を設けた集光素子と、光透過孔を有する光反射層とを備え、光反射層は、集光領域により集光された光が光透過孔を通過した後、太陽電池素子に入射し、太陽電池素子からの反射光が光反射層により反射され、太陽電池素子に再入射するように、太陽電池素子と集光素子との間に形成されていることを特徴としている。
【０２０７】
それゆえ、第１透明体を透過した光が集光領域へ入射するので、その入射角は第１透明体を設けていない場合に比較して小さくなる。したがって、集光された光が形成する光束を細く絞ることが可能となる。
【０２０８】
これにより、該光束に光透過孔の周囲を照射させることなく光透過孔内を通過させることが容易となるので、光反射層と太陽電池素子との間に導入される光量を増加させることができ、もって発電効率を高めることができる。
【０２０９】
また、太陽電池素子の表面または内部で反射された反射光の少なくとも一部は、光反射層における光透過孔以外の領域で反射され、太陽電池素子の方へ戻される。すなわち、太陽電池素子と反射層との間では、反射光が多重反射されることにより、光電変換層に照射される光量が増大するため、太陽電池の発電効率（光の利用効率）をさらに高くすることができるという効果を併せて奏する。
【０２１０】
また、本発明に係る太陽電池は、以上のように、光電変換層を有する太陽電池素子と、集光領域と集光補助層とを有する集光素子と、光透過孔を有する光反射層とを備え、上記集光補助層が、外部光の上記集光領域に対する入射角を該集光補助層を設けない場合に比較して小さくする機能を有し、光反射層が上記集光領域によって集光された光を光透過孔を介して上記太陽電池素子へ入射させるとともに、該太陽電池素子での反射光を反射し、該太陽電池素子へ再入射させる機能を有することを特徴としている。
【０２１１】
それゆえ、集光領域へ入射する光の入射角を小さくする集光補助層の機能によって、集光された光が形成する光束を細く絞ることが可能となる。これにより、既に説明したとおり、発電効率を高めることができる。
【０２１２】
また、光電変換層と光反射層との間での多重反射によって、太陽電池の発電効率を一層高めることができるという効果を併せて奏する。
【０２１３】
また、本発明の太陽電池は、上記の構成に加えて、上記集光曲面が、シリンドリカル状集光曲面であり、上記光透過孔が直線スリット状光透過孔であって、該シリンドリカル状集光曲面の円筒軸の方向と、該直線スリット状光透過孔の延伸方向とが平行に配置されていることを特徴としている。
【０２１４】
それゆえ、シリンドリカル状集光曲面によって線状に集光された光は直線スリット状光透過孔へと効率良く集光される。この結果、該直線スリット状光透過孔から入射した光が、光電変換層と光反射層との間で多重反射し、光電変換層に照射される光量が一層増大し、発電効率を一層高くすることが可能となる。さらに、太陽光の入射角度が変化した場合においても、入射太陽光を効率的に光透過孔へと集光することが可能となる。
【０２１５】
また、シリンドリカル状集光曲面は、少ない数で集光素子を構成することができるため、集光素子の構成を簡素化し、コストを下げることにも役立つ。このメリットは、光反射層の形成についても同様に当てはまるという効果を併せて奏する。
【０２１６】
また、本発明に係る太陽電池は、上記の構成に加えて、上記直線スリット状光透過孔を有する光反射層が、上記シリンドリカル状集光曲面の焦点距離よりも、シリンドリカル状集光曲面に近い位置に設けられていることを特徴としている。
【０２１７】
それゆえ、シリンドリカル状集光曲面の側部に入射した光の集光位置が、コマ収差の発生により、シリンドリカル状集光曲面の頂部に入射した光の集光焦点位置よりも、シリンドリカル状集光曲面に近い位置となる現象に対応することができ、シリンドリカル状集光曲面の側部に入射した光が、光透過孔群を通過し易くなる。
【０２１８】
これにより、シリンドリカル状集光曲面の頂部に入射した光と、側部に入射した光とを、効率良く直線スリット状光透過孔へと集光することが可能となり、太陽光等の光の入射角度が変化した場合においても高い発電効率を得ることが可能となるという効果をさらに奏する。
【０２１９】
また、本発明に係る太陽電池は、上記の構成に加えて、上記シリンドリカル状集光曲面の焦点距離をＦととすると、シリンドリカル状集光曲面の表面と上記直線スリット状光透過孔が設けられた位置との間隔が、（１１Ｆ／１７）以上、（１６Ｆ／１７）以下であることを特徴としている。
【０２２０】
それゆえ、上記間隔を上記の範囲に設定することにより、入射角の変動によらず、入射光のほとんどが直線スリット状光透過孔を通過することができるので、高い発電効率を維持することができるという効果をさらに奏する。
【０２２１】
また、本発明に係る太陽電池は、上記の構成に加えて、上記シリンドリカル状集光曲面の幅をＷとすると、上記直線スリット状光透過孔の幅が、（Ｗ／８）以上、（２Ｗ／３）以下であることを特徴としている。
【０２２２】
それゆえ、直線スリット状光透過孔の幅を上記の範囲とすることにより、光の透過率の増大と反射率の増大という、光反射層が備えるべき相反する機能を最適化することができるという効果をさらに奏する。
【０２２３】
また、本発明に係る太陽電池は、上記の構成に加えて、上記光反射層と上記光電変換層との間に、上記光電変換層の光電変換に寄与する波長の蛍光を発する透明基板が設けられていることを特徴としている。
【０２２４】
それゆえ、該透明基板は、その蛍光特性によって、光電変換に寄与する波長の光の光量が増大させるので、太陽電池の発電効率を一層高くすることができるという効果をさらに奏する。
【０２２５】
また、本発明に係る太陽電池は、上記光反射層と上記光電変換層との間の積層構造中に、上記光電変換層の光電変換に寄与する波長の蛍光を発する透明接着剤層が含まれていることを特徴としている。
【０２２６】
それゆえ、該透明接着剤層は、その蛍光特性によって、光電変換に寄与する波長の光の光量が増大させるので、太陽電池の発電効率を一層高くすることができる。
【０２２７】
また、光反射層と上記光電変換層との間に、透明接着剤層が介在する積層構造を形成することにより、太陽電池の構造的、機械的強度が高められ、また製造プロセスにおいて、破損等による歩留まり低下を抑制することもできるという効果をさらに奏する。
【０２２８】
また、本発明に係る太陽電池は、上記の構成に加えて、上記シリンドリカル状集光曲面の円筒軸方向を含み、かつ、集光素子に垂直な平面が、東西方向を向くように設置されていることを特徴としている。
【０２２９】
それゆえ、入射光の光軸を含みかつ円筒軸を含む平面と、集光素子が設けられた平面とが成す角度を常に一定とすることができるので、１日の太陽光の入射角度変化に対応して、該シリンドリカル状集光曲面と該直線スリット状光透過孔とを相対的に移動させる必要がなく、太陽光を効率良く直線スリット状光透過孔へと集光することができるという効果をさらに奏する。
【図面の簡単な説明】
【図１】本発明の太陽電池の構成例を示す断面斜視図である。
【図２】本発明の太陽電池に用いる太陽電池素子の構成例を示す断面図である。
【図３】図１の太陽電池に対する入射光の進路を説明するための説明図である。
【図４】本発明の太陽電池の設置方法を説明する図面である。
【図５】本発明に関連の有る太陽電池の構成例を示す断面斜視図である。
【図６】本発明の太陽電池の入射光の屈折状態を説明する断面図である。
【図７】（ａ）〜（ｃ）は、図５に示す太陽電池の集光状態を計算した結果を示す説明図である。
【図８】（ａ）〜（ｃ）は、図１に示す太陽電池の集光状態を計算した結果を示す説明図である。
【図９】（ａ）〜（ｃ）は、図１に示す太陽電池において、集光曲面と光反射層との距離を近づけたときの集光状態を計算した結果を示す説明図である。
【図１０】本発明の太陽電池の他の構成例を示す断面斜視図である。
【図１１】本発明の太陽電池のさらに他の構成例を示す断面斜視図である。
【図１２】本発明の太陽電池のさらに他の構成例を示す断面斜視図である。
【図１３】本発明の太陽電池に用いる太陽電池素子の他の構成例を示す断面図である。
【図１４】本発明の太陽電池のさらに他の構成例を示す断面斜視図である。
【図１５】本発明の太陽電池のさらに他の構成例を示す断面斜視図である。
【図１６】本発明の太陽電池のさらに他の構成例を示す断面斜視図である。
【図１７】従来の太陽電池素子の構成例を示す断面図である。
【図１８】従来の太陽電池素子の他の構成例を示す断面図である。
【図１９】従来の太陽電池素子のさらに他の構成例を示す断面図である。
【符号の説明】
１　基板
２　光電変換層
３　太陽電池素子側第２透明体
４　シリンドリカル状集光曲面群（集光領域）
５　光反射層
６　直線スリット状光透過孔群（光透過孔）
７　入射光
８　光入射側第１透明体
１５　縦方向
１６　横方向
１７、１８、２８　透明基板
１９　太陽電池素子用透明基板
２０　光電変換層
Ｆ　焦点距離
Ｑ　入射角[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solar cell.
[0002]
[Prior art]
Conventional solar cells include a polycrystalline Si solar cell that performs photoelectric conversion by a pn junction as shown in FIG. 17 (for example, see Patent Document 2), and a non-crystalline solar cell that performs photoelectric conversion by a pin junction as shown in FIG. It is a crystalline Si solar cell (for example, see Patent Document 1). Although not shown, there is a single crystal Si solar cell in which a pn junction is formed on a single crystal Si substrate.
[0003]
In the polycrystalline Si solar cell shown in FIG. 17, an electrode metal layer 172 having a light reflecting effect and a good electrical contact between the electrode metal layer 172 and the polycrystalline Si semiconductor layer 174 are provided on a substrate 171 also serving as a support. A polycrystalline Si semiconductor layer 173 doped with one of an n-type impurity and a p-type impurity at a high concentration, and a polycrystalline Si semiconductor layer slightly doped with the same conductivity type impurity as the polycrystalline Si semiconductor layer 173. 174, a polycrystalline Si semiconductor layer 175 doped with a conductive impurity at a high concentration opposite to the polycrystalline Si semiconductor layers 173 and 174, a current collecting electrode 176 for extracting current, and an antireflection layer for efficiently capturing light. 177.
[0004]
In the amorphous Si solar cell shown in FIG. 18, an electrode metal layer 182 having a light reflection effect and an n-type impurity doped with an n-type impurity are formed on a substrate 181 also serving as a support. A layer 183, an i-layer 184 made of an amorphous Si semiconductor and being an intrinsic semiconductor, a p-layer 185 made of an amorphous Si semiconductor and doped with a p-type impurity, a current collecting electrode 186 for extracting a current, an efficient light And an anti-reflection layer 187 for taking in light.
[0005]
In addition, in order to increase power generation efficiency, a tandem solar cell has been proposed in which a pn junction formed of a polycrystalline semiconductor shown in FIG. 17 and a pin junction formed of an amorphous semiconductor shown in FIG. 18 are stacked.
[0006]
In addition to these solar cells, a solar cell as shown in FIG. 19 in which light is incident from the substrate side has been proposed. The solar cell includes a transparent substrate 191, an antireflection layer 192 for efficiently taking in light, a current collecting electrode 193 for taking out current, and an amorphous Si semiconductor on the transparent substrate 191 in order from the light incident side. A p-layer 194 doped with a p-type impurity; an i-layer 195 made of an amorphous Si semiconductor and being an intrinsic semiconductor; an n-layer 196 made of an amorphous Si semiconductor and doped with an n-type impurity; And an electrode metal layer 197.
[0007]
[Patent Document 1]
JP-A-5-48127 (published February 26, 1993)
[0008]
[Patent Document 2]
JP-A-11-214717 (published August 6, 1999)
[0009]
[Problems to be solved by the invention]
However, the above-described conventional configuration has a problem that power generation efficiency is low due to various factors described below.
[0010]
The first factor lies in the antireflection layers 177, 187, and 192. That is, in the above-described conventional solar cell (FIGS. 17 to 19), the antireflection layer 177 made of a conductive transparent film is formed on the light incident surface or near the light incident surface for the purpose of minimizing surface reflection. , 187, and 192, it is difficult to completely reduce the surface reflection to zero, and there is a problem that a part of incident light is reflected. In addition, the antireflection layers 177, 187, and 192 generally have wavelength dependence, and a problem arises in that the surface reflection increases when the light wavelength deviates from the center of the design wavelength. In particular, in a tandem solar cell that uses light of a relatively wide wavelength for photoelectric conversion, the adverse effect is even greater.
[0011]
The second factor is in the collecting electrodes 176, 186, 193. That is, the current collecting electrodes 176, 186, and 193 provided on the light incident side for completely extracting the current completely reflect the incident light, so that the power generation efficiency is surely reduced.
[0012]
By the way, the polycrystalline Si semiconductor layers 174 and the amorphous Si semiconductor layers 184 and 195 which generate electric charge by absorbing light and generate electric power need to have a sufficient thickness to absorb incident light. To increase the efficiency, it is conceivable to increase the film thickness. However, if the thickness of the semiconductor layer is too large, the traveling distance of the charge increases, and thus a problem arises in that the amount of current that can be extracted to the outside decreases. In addition, an increase in the thickness of the semiconductor layer leads to an increase in manufacturing time and an increase in the amount of material used, which leads to an increase in cost.
[0013]
Therefore, in order to improve the incident light absorptance of the photoelectric conversion layer including the semiconductor layer as described above, how to increase the amount of incident light on the photoelectric conversion layer without increasing the thickness of the semiconductor layer itself. This is the biggest issue. This translates into an issue of how to make it possible to reduce the thickness of the semiconductor layer without reducing external output current by using external light such as sunlight without waste. .
[0014]
Furthermore, external light such as sunlight does not always irradiate the photoelectric conversion layer vertically, and the irradiation angle changes depending on the place, season, and time. It is necessary to consider the installation location and the movement of the sun.
[0015]
The present invention has been made in view of the above problems, and an object of the present invention is to efficiently convert the external light into a photoelectric conversion by considering an irradiation angle of the external light (mainly sunlight) and a change in the irradiation angle. The light incident on the photoelectric conversion layer and the light reflected on the current collecting electrode provided on the light incident side are reflected by the light reflection layer, so that the light incident on the photoelectric conversion layer is as external as possible. Another object of the present invention is to provide a solar cell having higher power generation efficiency than conventional solar cells.
[0016]
[Means for Solving the Problems]
In order to solve the above problems, a solar cell according to the present invention comprises a solar cell element having a photoelectric conversion layer, a light incident side first transparent body having a refractive index larger than air, and a light incident side first transparent body. A light-collecting element having a light-collecting region provided between the solar cell element-side second transparent body having a large refractive index; and a light-reflecting layer having a light-transmitting hole. After the emitted light passes through the light transmission hole, it enters the solar cell element, and the light reflected from the solar cell element is reflected by the light reflection layer and collected with the solar cell element so as to re-enter the solar cell element. It is characterized in that it is formed between an optical element.
[0017]
According to the above configuration, the light incident on the light-collecting element first passes through the light-incidence-side first transparent body, the light-collecting region, and the solar cell element-side second transparent body that constitute the light-collecting element. At this time, the light emitted from the solar cell element-side second transparent body toward the light reflection layer is collected by the action of the light collection region. Subsequently, the condensed light passes through a light transmission hole provided in the light reflection layer and enters the solar cell element.
[0018]
In this case, a plurality of light-collecting regions and a plurality of light transmitting holes may be provided. Further, one or a plurality of light transmitting holes may be arranged at each light condensing position of the plural light condensing regions.
[0019]
Subsequently, light incident on the solar cell element irradiates the photoelectric conversion layer and is absorbed by the photoelectric conversion layer, but a part of the light is reflected on the surface or inside the solar cell element to become reflected light. On the other hand, at least a part of the reflected light is reflected by a region other than the light transmitting holes in the light reflecting layer, and is returned to the solar cell element. That is, since the reflected light is multiply reflected between the solar cell element and the reflective layer, the amount of light applied to the photoelectric conversion layer increases, so that the power generation efficiency (light use efficiency) of the solar cell is increased. It has become possible.
[0020]
At this time, in order to further improve the light use efficiency, it is preferable to increase the amount of light introduced through the light transmission hole and introduced between the light reflection layer and the solar cell element as much as possible.
[0021]
For this purpose, it is preferable that the light beam formed by the light condensed in the light condensing area be narrowed down and then transmitted through the light transmitting hole so that the light beam does not irradiate around the light transmitting hole.
[0022]
In general, when a light-collecting region having a light-condensing function is formed at the boundary between a medium having a relatively small refractive index and a medium having a large refractive index, the smaller the incident angle of a parallel light beam incident on the medium having a smaller refractive index, the smaller the light is collected The movement of the light condensing position of the light condensed in the region and traveling in the medium having a large refractive index is reduced. As the movement of the light collecting position becomes smaller, the light condensing degree of the light passing through the light transmitting hole becomes higher. Therefore, reducing the angle of incidence of light incident on the light-collecting region is a point for increasing light use efficiency.
[0023]
According to the above configuration, external light such as the sun is refracted on the surface of the first transparent body having a higher refractive index than air before being incident on the light-collecting region. Smaller than the corner. That is, since the light transmitted through the first transparent body is incident on the light-collecting region, the angle of incidence is smaller than when the first transparent body is not provided. Therefore, it is possible to narrow the light beam formed by the collected light.
[0024]
This makes it easy for the light beam to pass through the light transmitting hole without irradiating the periphery of the light transmitting hole, so that the amount of light introduced between the light reflecting layer and the solar cell element can be increased. As a result, power generation efficiency can be increased.
[0025]
Further, a solar cell according to the present invention includes a solar cell element having a photoelectric conversion layer, a light-collecting element having a light-collecting region and a light-concentrating auxiliary layer, and a light reflecting layer having a light-transmitting hole. The light auxiliary layer has a function of reducing the incident angle of the external light with respect to the light collection area as compared with a case where the light collection auxiliary layer is not provided, and the light reflection layer is collected by the light collection area. Light is incident on the solar cell element through the light transmitting hole, and a function of reflecting light reflected by the solar cell element and re-entering the solar cell element is provided.
[0026]
According to the above configuration, the external light that has passed through the light transmission hole group is irradiated to the photoelectric conversion layer by repeating a series of actions of irradiation, absorption, and partial reflection between the photoelectric conversion layer and the light reflection layer. As described above, the amount of light that increases and the power generation efficiency of the solar cell increases.
[0027]
Furthermore, in the above configuration, since the light-condensing auxiliary layer having a function of reducing the incident angle of light incident on the light-condensing region is provided, the incident angle on the light-condensing region is set when there is no light-condensing auxiliary layer. In comparison, the light beam formed by the condensed light can be narrowed down.
[0028]
Thereby, as described above, the amount of light introduced between the light reflection layer and the solar cell element can be increased, and thus the power generation efficiency can be increased.
[0029]
Further, in the solar cell of the present invention, the condensing curved surface is a cylindrical converging curved surface, the light transmitting hole is a linear slit-shaped light transmitting hole, and the direction of the cylindrical axis of the cylindrical converging curved surface. The straight slit-shaped light transmitting holes are arranged in parallel with the extending direction.
[0030]
In the above configuration, in order to maximize the amount of light that passes through the light transmitting hole when the light collected by the light collecting area passes through the light transmitting hole, the cross-sectional shape of the light passing through the light transmitting hole must be equal to the light transmitting hole. Has a high similarity to the shape of the light-transmitting hole, and preferably the cross-sectional area of the light is within the area of the light transmitting hole.
[0031]
According to the above configuration, since the cylindrical converging curved surface creates a linear condensing state, as a light transmitting hole, the extending direction thereof is a linear slit shape arranged in parallel with the cylindrical axis of the cylindrical converging curved surface. By adopting the light transmitting hole, the light condensed in a linear shape is efficiently condensed to the linear slit-shaped light transmitting hole.
[0032]
As a result, light incident from the linear slit-shaped light transmitting hole is multiple-reflected between the photoelectric conversion layer and the light reflection layer, and the amount of light irradiated on the photoelectric conversion layer further increases, thereby further increasing power generation efficiency. It becomes possible.
[0033]
In addition, since the cylindrical condensing curved surface can cover an elongated condensing area, a large condensing element can be manufactured by arranging the elongated condensing areas side by side. That is, since the light-collecting element can be formed with a smaller number of light-collecting areas than the light-collecting area having a shorter shape, the structure of the light-collecting element can be simplified and the cost can be reduced. This advantage similarly applies to the formation of the light reflection layer.
[0034]
In addition, in the solar cell according to the present invention, in addition to the above configuration, the light reflecting layer having the linear slit-shaped light transmitting holes is closer to the cylindrical light-collecting curved surface than the focal length of the cylindrical light-collecting curved surface. It is characterized by being provided at a position.
[0035]
According to the above configuration, when the solar cell is installed outdoors, the incident angle of the solar ray incident on the solar cell is accompanied by seasonal fluctuation. The aim of the present configuration is to suppress a decrease in power generation efficiency due to this seasonal variation.
[0036]
Here, consider a state in which the cylindrical converging curved surface is placed on a horizontal surface with the convex surface facing upward, and further consider a cylinder having the cylindrical converging curved surface as a part of the cylindrical surface.
In this state, the direction of rotation that rotates a vertical plane including the light beam incident from directly above the cylindrical condensing curved surface and the center line (cylindrical axis) of the cylinder around the center line is referred to as the cylindrical collection direction. It is defined as the "lateral direction" with respect to the light curved surface.
[0037]
When a light beam incident from directly above the cylindrical light-collecting curved surface is incident on the cylindrical light-collecting curved surface in a state of being inclined in the lateral direction, the light incident on the side of the cylindrical light-collecting curved surface is generated due to coma aberration. The light position is closer to the cylindrical converging curved surface than the converging focal position of the light incident on the top of the cylindrical converging curved surface. In other words, since the light condensing position differs depending on the light incident position, the light condensing state deteriorates.
[0038]
Therefore, when the light reflecting layer is disposed at a position corresponding to the focal length of the cylindrical light-collecting element, light incident on the top of the cylindrical light-collecting curved surface passes through the linear slit-shaped light transmitting hole, but is cylindrical. Light incident on the side of the curved light-condensing surface is less likely to pass through the linear slit-shaped light transmitting hole, and the power generation efficiency is reduced accordingly.
[0039]
On the other hand, the cylindrical condensing curved surface and the light reflecting layer are arranged such that the distance between the cylindrical condensing curved surface and the light reflecting layer is shorter than the focal length of the cylindrical condensing curved surface. By arranging, the position of the light transmission hole formed in the light reflection layer and the light condensing position of the light incident on the side of the cylindrical condensing curved surface are close to each other. As a result, light incident on the side of the cylindrical condensing curved surface is more likely to pass through the light transmitting hole group. The light incident on the top of the cylindrical condensing curved surface passes through the light transmitting hole without change even if the position of the light reflecting layer changes in the optical axis direction.
[0040]
This makes it possible to efficiently condense the light incident on the top of the cylindrical condensing curved surface and the light incident on the side into the linear slit-shaped light transmitting hole efficiently, and the incidence of light such as sunlight High power generation efficiency can be obtained even when the angle changes.
[0041]
Further, the solar cell according to the present invention, in addition to the above configuration, provided that the focal length of the cylindrical condensing curved surface is F, the surface of the cylindrical condensing curved surface and the linear slit light transmitting hole are provided. The distance from the touched position is (11F / 17) or more and (16F / 17) or less.
[0042]
According to the above configuration, if the interval is smaller than (11F / 17), the position of the linear slit-shaped light transmitting hole is too close to the cylindrical condensing curved surface from the condensing position in a range where the incident angle is small. The spread light beam before being condensed irradiates the linear slit-shaped light transmitting hole. For this reason, in the range where the incident angle is small, that is, in the time period when the power generation amount is originally large, the light that cannot pass through the straight slit-shaped light transmitting hole increases, and the power generation efficiency decreases.
[0043]
On the other hand, if the interval is larger than (16F / 17), in the range where the incident angle is large, the light condensing position is located between the linear slit-shaped light transmitting hole and the cylindrical light condensing curved surface, Since the position of the slit-shaped light transmitting hole is too far away, the spread light beam after being condensed irradiates the straight slit-shaped light transmitting hole. For this reason, in the range where the incident angle is large, the amount of light that cannot pass through the straight slit-shaped light transmitting hole increases, and the power generation efficiency decreases.
[0044]
Therefore, by setting the interval in the above range, most of the incident light can pass through the linear slit-shaped light transmitting hole regardless of the variation of the incident angle, and thus high power generation efficiency can be maintained. .
[0045]
Further, in the solar cell according to the present invention, in addition to the above configuration, when the width of the cylindrical condensing curved surface is W, the width of the linear slit-shaped light transmitting hole is (W / 8) or more and (2W / 3) It is characterized by the following.
[0046]
In the above configuration, if the width of the linear slit-shaped light transmission hole is smaller than (W / 8) with respect to the width W of the cylindrical light-collecting curved surface, the light-collecting state at a time or season when the incident angle of sunlight increases. Therefore, the ratio of sunlight that does not enter the straight slit-shaped light transmitting hole increases. As a result, the power generation efficiency decreases. On the other hand, when the width of the linear slit-shaped light transmitting hole is wider than (2W / 3), light to be multiple-reflected between the photoelectric conversion layer and the light reflecting layer is emitted from the linear slit-shaped light transmitting hole. As a result, the utilization efficiency of the incident light decreases, and the power generation efficiency decreases.
[0047]
Therefore, by setting the width of the linear slit-shaped light transmitting hole in the above range, the opposing functions that the light reflecting layer should have, such as an increase in light transmittance and an increase in reflectivity, can be optimized.
[0048]
In addition, the solar cell according to the present invention, in addition to the above configuration, between the light reflection layer and the photoelectric conversion layer, provided a transparent substrate that emits fluorescence having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer. It is characterized by being done.
[0049]
With the above configuration, the light condensed by the light condensing element passes through the light transmission hole and enters the transparent substrate. The transparent substrate absorbs light having a wavelength that does not contribute to the photoelectric conversion of the photoelectric conversion layer, converts the light into a light having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer, and emits fluorescent light. The generated fluorescence is irradiated directly or after being once reflected by the reflection layer onto the photoelectric conversion layer.
[0050]
Therefore, the amount of light having a wavelength that contributes to photoelectric conversion increases, so that the power generation efficiency of the solar cell can be further increased.
[0051]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0052]
Further, the solar cell according to the present invention, in the laminated structure between the light reflecting layer and the photoelectric conversion layer, a transparent adhesive layer that emits fluorescence having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer is included. It is characterized by having.
[0053]
In the above configuration, various modes of a laminated structure in which a transparent adhesive layer is interposed between the light reflecting layer and the photoelectric conversion layer can be included. For example, a light-collecting element having a light-reflecting layer formed on the surface of the light-collecting element on the solar cell element side may be bonded and fixed to the solar cell element via a transparent adhesive layer. Alternatively, a transparent substrate that controls the distance between the light-collecting element and the solar cell element may be bonded and fixed between the light-collecting element and the solar cell element via a transparent adhesive layer. Alternatively, a transparent substrate having a light reflecting layer formed on the surface on the light-collecting element side may be bonded and fixed to the solar cell element via a transparent adhesive layer.
[0054]
As described above, in the laminated structure that can take various aspects, by the interposition of the transparent adhesive layer having the above-described fluorescent characteristics, light collected by the light-collecting element passes through the light transmission holes of the light reflection layer. It passes through and enters the transparent adhesive in the laminated structure. The reason why the power generation efficiency of the solar cell can be further increased by this is the same as the function of the transparent substrate having the fluorescence characteristic described above.
[0055]
Further, by forming a laminated structure in which a transparent adhesive layer is interposed between the light reflecting layer and the photoelectric conversion layer, the structural and mechanical strength of the solar cell is increased, and the solar cell is damaged in the manufacturing process. The yield can be suppressed from being lowered.
[0056]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0057]
In addition, the solar cell according to the present invention, in addition to the above configuration, including the cylindrical axis direction of the cylindrical condensing curved surface, and is installed so that a plane perpendicular to the condensing element faces the east-west direction. It is characterized by having.
[0058]
With the above configuration, in the morning and evening, when sunlight is incident on the cylindrical condensing curved surface from obliquely above in the east-west direction, a plane including the optical axis and including the cylindrical axis, and a plane provided with the condensing element Can always be constant, and light condensed linearly by the cylindrical converging curved surface is always converged on a plane that includes the optical axis and includes the cylindrical axis. .
[0059]
Further, according to the configuration described above, since the direction of the cylindrical axis of the cylindrical condensing curved surface and the extending direction of the linear slit-shaped light transmitting hole are arranged in parallel, the linear slit-shaped light transmitting hole is It is arranged on a plane including the optical axis and including the cylindrical axis.
[0060]
Accordingly, the sunlight can be efficiently transmitted through the linear slit light without moving the cylindrical condensing curved surface and the linear slit light transmission hole relatively in response to the change in the incident angle of the sunlight in one day. It becomes possible to condense light to the hole.
[0061]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the solar cell of the present invention will be described in detail with reference to the drawings.
[0062]
FIG. 1 shows a cross-sectional perspective view of the solar cell of the present invention.
[0063]
The solar cell of the present invention includes a solar cell element in which a photoelectric conversion layer 2 is provided on a substrate 1 also serving as a support, a light incident side first transparent body 8, and a solar cell element side second transparent body 3. And a light-condensing element provided with a group of cylindrical light-condensing curved surfaces 4 between the transparent bodies 3 and 8.
[0064]
Further, a light reflecting layer 5 having a linear slit-shaped light transmitting hole group 6 is provided on a surface of the solar cell element side second transparent body 3 on the side of the solar cell element (light emission side).
[0065]
In the group of cylindrical light-collecting curved surfaces 4, the convex surface of each cylindrical light-collecting curved surface (light-collecting region) faces the light incident side, and a plurality of cylindrical light-collecting curved surfaces are arranged in parallel with their respective cylindrical axes parallel. I have. The cylindrical axis means a central axis of the cylinder when a cylindrical light-condensing curved surface is considered as a part of the cylindrical surface.
[0066]
The linear slit-shaped light transmitting hole group 6 is constituted by linear slit-shaped light transmitting holes corresponding to the respective cylindrical condensing curved surfaces. Further, from the viewpoint that light condensed linearly on the cylindrical condensing curved surface passes through the linear slit light transmitting hole most efficiently, the direction of the cylindrical axis of the cylindrical condensing curved surface, The linear slit-shaped light transmitting holes are arranged so that the extending direction is parallel to the extending direction.
[0067]
Here, as shown in FIG. 1, the linear slit-shaped light transmitting hole is on the optical axis of light incident from directly above the corresponding cylindrical condensing curved surface, and the light is condensed. Is located at
[0068]
In the above-described configuration, the incident light 7 vertically incident on the light incident side first transparent body 8 is also vertically incident on the cylindrical condensing curved surface group 4 as it is, and the solar cell element is formed by the cylindrical condensing curved surface group 4. After being focused on the linear slit-shaped light transmitting hole group 6 provided on the surface of the side second transparent body 3, the light is irradiated onto the photoelectric conversion layer 2 of the solar cell element.
The reflected light from the photoelectric conversion layer 2 is reflected by the light reflection layer 5 provided in the light-collecting element, and again enters the photoelectric conversion layer 2 of the solar cell element. As described above, the light incident from the linear slit-shaped light transmitting hole group 6 is multiple-reflected between the solar cell element and the light reflection layer 5, that is, by repeating absorption and partial reflection in the solar cell element. In addition, the power generation efficiency of the solar cell element can be increased.
[0069]
Therefore, the light reflecting layer 5 only needs to be able to reflect at least the reflected light from the photoelectric conversion layer 2 in a region other than the linear slit light transmitting hole group 6. The facing surface may be any light reflecting layer 5 that can reflect light.
[0070]
On the other hand, the surface on the light incident side of the light reflecting layer 5, that is, the surface facing the cylindrical condensing curved surface group 4, may have a light reflecting function or a light absorbing function. However, in order to have a light absorbing function, it is necessary to add a layer having a light absorbing function, which leads to an increase in cost. Therefore, it is desirable that the configuration in which the light reflecting layer 5 is formed only of a material having light reflectivity, that is, the light incident side surface of the light reflecting layer 5 also has a light reflecting function.
[0071]
Further, here, the description has been made using the cylindrical condensing curved surface as the condensing element having the condensing region. However, it is sufficient that the condensing element has a function of condensing light on the linear slit-shaped light transmitting hole group 6. It is not limited to this. For example, FIG. 1 shows a light-collecting element in which cylindrical condensing curved surfaces having the same radius of curvature are always arranged in parallel, but the radius of curvature gradually decreases from the top to the side of the cylindrical condensing curved surface. By using such a cylindrical condensing curved surface, it is possible to reduce coma aberration generated at the side portion, and it is possible to suppress a decrease in power generation efficiency due to an increase in the incident angle.
[0072]
In addition, it is also possible to condense light to the linear slit-shaped light transmitting hole group 6 by configuring each condensing area with a Fresnel condensing element. In this case, by using a Fresnel light-collecting element having a small unevenness, the light-collecting element can be made thinner, and the solar cell can be made thinner.
[0073]
Further, as the photoelectric conversion layer 2, a photoelectric conversion layer such as a polycrystalline Si solar cell, an amorphous Si solar cell, or a tandem-structure solar cell as described in the related art can be used. In addition, a single crystal Si solar cell, CuInSe ₂ , Cu (In, Ga) (S, Se) ₂ , CuGaSe ₂ It is also possible to use a photoelectric conversion layer used in CIS-based solar cells and the like.
[0074]
FIG. 2 shows an example of a solar cell element, in which an electrode metal layer 9 having a light reflecting effect and a good electrical contact between the electrode metal layer 9 and the semiconductor layer are formed on a substrate 1 which also serves as a support. A polycrystalline Si semiconductor layer 10 doped with a p-type or n-type conductive impurity at a high concentration, and a polycrystalline Si semiconductor lightly doped with the same conductive impurity as the polycrystalline Si semiconductor layer 10. Layer 11, polycrystalline Si semiconductor layers 10, polycrystalline Si semiconductor layer 12 doped with impurities of the opposite conductivity type at a high concentration, current collecting electrode 13 for extracting current, and conductivity for efficiently capturing light And an antireflection layer 14 made of a transparent conductive film.
[0075]
In such a solar cell element, sunlight is introduced from the antireflection layer 14 side, and photoelectric conversion is performed in the polycrystalline Si semiconductor layer. At this time, the antireflection layer 14 generally has wavelength dependency, and it is impossible to completely prevent the reflection of light of all wavelengths. Therefore, the reflected light from the antireflection layer 14 exists. Will be. Further, the light applied to the current collecting electrode 13 for extracting a current is completely reflected by the current collecting electrode 13.
[0076]
In the solar cell of the present invention, the reflected light from the solar cell element is reflected by the light reflection layer 5 provided on the light-collecting element, and is incident on the solar cell element again. Thereby, the light incident from the light transmission hole group 6 can be multiple-reflected between the photoelectric conversion layer 2 and the light reflection layer 5 of the solar cell element, so that the power generation efficiency of the solar cell element can be increased. .
[0077]
Next, FIGS. 3 and 4 are diagrams illustrating a method of installing the solar cell.
[0078]
Here, in this specification, as shown in FIG. 3, the cylindrical axis direction of the cylindrical converging curved surface group 4 is referred to as a vertical direction 15, which is orthogonal to the vertical direction 15, and which is orthogonal to the vertical direction 15. A direction parallel to the light incident surface is referred to as a lateral direction 16.
[0079]
In a solar cell using sunlight as a light source, efficient power generation needs to be performed regardless of the incident angle of the incident light 7. For example, as shown in FIG. 4, at 8 o'clock in the morning, the incident light 7 enters the solar cell from obliquely above east, at 12:00 noon, the incident light 7 enters the solar cell from above vertically, and at 16:00 in the evening, The incident light 7 enters the solar cell from obliquely above the west. In order to perform efficient power generation, the incident lights 7 having such different incident angles are condensed by the cylindrical condensing curved surface group 4 and efficiently incident on the linear slit light transmitting hole group 6. Is required.
[0080]
FIG. 5 is a sectional perspective view of a solar cell filed by us in Japanese Patent Application No. 2001-296409 (not disclosed at the time of confirmation before the present application).
[0081]
As shown in FIG. 5, for a solar cell in which the light-collecting element is constituted only by the solar cell element-side second transparent body 3, when the incident light 7 is incident at an incident angle R from obliquely above the horizontal direction 16, the power generation is performed. Efficiency drops significantly. This is because the optical axis is deviated from the linear slit-shaped light transmitting hole group 6, so that the incident light 7 condensed by the cylindrical condensing curved surface group 4 does not enter the linear slit-shaped light transmitting hole group 6, and the light is reflected. This is because the light is reflected by the layer 5 and the sunlight is not irradiated on the photoelectric conversion layer 2 of the solar cell.
[0082]
On the other hand, when the incident light 7 is incident obliquely from above in the vertical direction 15 at an incident angle Q, the inclination of a plane including the optical axis and including the cylindrical axis is constant independently of the incident angle Q, and is cylindrically condensed. The position where light is condensed linearly by the curved surface group 4 exists on the plane. Therefore, the optical axis remains coincident with the linear slit-shaped light transmitting hole group 6, and the incident light 7 condensed by the cylindrical condensing curved surface group 4 enters the linear slit-shaped light transmitting hole group 6. As a result, it is possible to maintain high power generation efficiency even when sunlight enters obliquely from above.
[0083]
In view of the above situation, the solar cells are installed such that the vertical direction 15 of the cylindrical converging curved surface group 4 coincides with the traveling direction of the diurnal movement of the sun, that is, the east-west direction. That is, it is installed so that the plane including the cylindrical axis direction of the cylindrical converging curved surface and perpendicular to the condensing element faces the east-west direction. Thus, high power generation efficiency can be maintained throughout the day.
[0084]
Also in the solar cell of the present invention, for the same reason as the solar cell shown in FIG. 5, based on the above-described installation method, it is preferable that the vertical direction 15 be installed so as to coincide with the east-west direction. The solar cell of the present invention is different from the solar cell shown in FIG. 5 in that, when the incident angle Q of the incident light 7 is increased, the light incident side having a different refractive index is used for the purpose of maintaining higher power generation efficiency. This is a solar cell using a light-collecting element which is constituted by a first transparent body 8 and a second transparent body 3 on the solar cell element side, and in which a group of cylindrical converging curved surfaces 4 is provided between the transparent bodies 2 and 3.
[0085]
Hereinafter, the difference between the solar cell of the present invention and the solar cell of FIG. 5 will be described assuming that the cylindrical axial direction of the cylindrical converging curved surface group 4 of the solar cell is arranged to coincide with the east-west direction.
[0086]
In the solar cell without the light incident side first transparent body 8 shown in FIG. 5, when the sunlight 7 is incident at an incident angle Q = Q1 with respect to the vertical direction 15, Thus, the incident light 7 having the incident angle Q1 is incident.
[0087]
On the other hand, in the solar cell provided with the light incident side first transparent body 8 shown in FIG. 3, the incident light 7 incident on the light incident side first transparent body 8 at the incident angle Q1 as shown in FIG. , Refracted at a refraction angle (Q2) smaller than the incident angle Q1. This is because the refractive index n1 of the first transparent body 8 on the light incident side is larger than the refractive index n0 of the air into which the light enters.
[0088]
Therefore, the incident angle Q2 of sunlight on the cylindrical converging curved surface group 4 provided at the interface between the light incident side first transparent body 8 and the solar cell element side second transparent body 3 is determined by the light incident side first transparent body. It is equal to the angle of refraction at the body 8 and smaller than the angle of incidence Q1. That is, by providing the light incident side first transparent body 8, the incident angle of sunlight on the cylindrical condensing curved surface group 4 can be reduced.
[0089]
The incident angle Q2 is determined from the incident angle Q1 and the refractive indexes n0 and n1 so as to satisfy the law of refraction (n0sinQ1 = n1sinQ2).
[0090]
FIG. 7 shows the solar cell without the light-incident side first transparent body 8 shown in FIG. The figure shows the result of calculating how the optical path of light condensed by the cylindrical condensing curved surface group 4 changes when sunlight is irradiated. The unit of the numerical scale in the figure is mm.
[0091]
In the calculation, the refractive index n0 of air is set to 1.0, the refractive index n2 of the second solar cell element-side transparent body 3 is set to 1.5, and the cylindrical condensing curved surface group 4 having a radius of curvature of 10 mm has a width of 12 mm. The case where they are arranged at intervals was performed.
[0092]
When the refractive index between the second transparent body 3 on the solar cell element side and the solar cell element is different from the refractive index n2 of the second transparent body 3 on the solar cell element side, the light passes through the linear slit-shaped light transmitting hole group 6. The refracted light is refracted, but all the light transmitted through the linear slit-shaped light transmitting hole group 6 reaches the photoelectric conversion layer 2 and becomes light contributing to the photoelectric conversion. There is no. Therefore, here, the calculation was performed on the assumption that the refractive index between the solar cell element-side second transparent body 3 and the solar cell element is equal to the refractive index n2 of the solar cell element-side second transparent body 3.
[0093]
In FIG. 7, (a), (b), and (c) are the results of calculations for the case where Q1 = 0 °, Q1 = 40 °, and Q1 = 80 °, respectively. The incident light 7 obliquely from above in the vertical direction 15 (FIG. 5) is condensed while traveling along the vertical direction 15 in the second transparent body 3 on the solar cell element side. The light condensing state is projected on a vertical section of the solar cell, and the change in the condensing state depending on the incident angle is examined.
[0094]
As can be seen from FIGS. 7A to 7C, as the incident angle with respect to the vertical direction 15 increases, the condensing position of the incident light moves so as to approach the direction of the cylindrical converging curved surface group 4. As a result, when the incident angle Q1 becomes 80 °, as shown in FIG. 7C, the light incident on the linear slit-shaped light transmitting hole group 6 becomes a small part of the incident light, and most of the incident light Is irradiated on the light reflection layer 5 and is reflected by the light reflection layer 5. For this reason, the power generation efficiency is significantly reduced.
[0095]
On the other hand, FIG. 8 shows the result of performing similar calculations for the solar cell of the present invention shown in FIG. In the calculation, the refractive index n0 of air is 1.0, the refractive index n1 of the first transparent body 8 on the light incident side is 1.4, and the refractive index n2 of the second transparent body 3 on the solar cell element side is 1.9. This was performed for a case where the cylindrical condensing curved surface groups 4 having a curvature radius of 10 mm were arranged at intervals of 12 mm in width.
[0096]
When the refractive index between the second transparent body 3 on the solar cell element side and the solar cell element is different from the refractive index n2 of the second transparent body 3 on the solar cell element side, the light passes through the linear slit-shaped light transmitting hole group 6. The refracted light is refracted. Here, as described above, the refractive index between the solar cell element side second transparent body 3 and the solar cell element side second transparent body 3 The calculation was performed assuming that it was equal to the refractive index n2.
[0097]
In FIG. 8, (a), (b), and (c) are the results of calculations for the case where Q1 = 0 °, Q1 = 40 °, and Q1 = 80 °, respectively, as in the case of FIG.
The incident light 7 obliquely from above in the vertical direction 15 is condensed while traveling in the light condensing element along the vertical direction 15, but in FIG. The projection is performed to check the change in the light collection state depending on the incident angle.
[0098]
As described with reference to FIG. 6, the incident light 7 is incident from the atmosphere having a refractive index of 1.0 (n0) to the light incident side first transparent body 8 having a refractive index of 1.4 (n1) and is refracted. The incident angle Q2 of light incident on the cylindrical converging curved surface group 4 becomes smaller in accordance with the law of refraction. In the case of the incident angle Q1 = 40 ° in (b), the actual incident angle Q2 becomes 27.3 °. , (C), the actual incident angle Q2 = 44.7 °.
[0099]
For this reason, as can be seen from FIGS. 8A to 8C, even if the incident angle Q1 with respect to the vertical direction 15 becomes large, the condensing position of the incident light moves closer to the direction of the cylindrical converging curved surface group 4. The amount is much smaller than in the case of FIGS. 7 (a) to 7 (c).
As a result, even if the incident angle Q1 becomes 80 °, as shown in FIG. 8C, light that cannot enter the straight slit-shaped light transmitting hole group 6 becomes a small part of the incident light, The incident light can pass through the linear slit light transmitting hole group 6.
[0100]
As described above, the light incident side first transparent body 8 acts as a light collection auxiliary layer, so that the incident angle Q2 is substantially reduced, so that even when the actual incident angle Q1 of sunlight increases, the efficiency is improved. It is possible to condense incident light to the slit-shaped light transmitting hole group 6. Therefore, as compared with a solar cell that does not include the light-incident-side first transparent body 8, the power generation efficiency is maintained higher regardless of the incident angle of sunlight.
[0101]
FIGS. 8A, 8B, and 8C show the position of the focal length F of the cylindrical converging curved surface group 4, that is, the incident angle Q1 = 0 ° in the solar cell of the present invention. FIG. 3A shows a state in which a linear slit-shaped light transmission hole group 6 is provided at the light condensing position. At this time, although the light transmittance of the linear slit-shaped light transmitting hole group 6 is high as a whole in comparison with FIG. 7, when FIG. 8 (a) and FIG. 8 (c) are compared, FIG. 8) has lower power generation efficiency than FIG. 8A. As described above, as the incident angle Q1 increases, the light condensing position approaches the cylindrical condensing curved surface group 4, so that a part of the incident light is reflected by the light reflecting layer 5 and the linear slit is formed. This is because the amount of light condensed on the group of light transmitting holes 6 decreases.
[0102]
Therefore, in the solar cell of the present invention, as shown in FIG. 9, the distance d between the light reflecting layer 5 having the linear slit-shaped light transmitting hole group 6 and the cylindrical condensing curved surface group 4 (see FIGS. 1 and 9 ( b)) was made smaller than the focal length F of the cylindrical converging curved surface group 4. That is, when the linear slit-shaped light transmitting hole group 6 is provided at a position closer to the cylindrical light-collecting curved surface group 4 than the focal length F of the cylindrical light-collecting curved surface group 4, the light transmission of the linear slit-shaped light transmitting hole group 6 can be achieved. The rate can be further increased.
[0103]
Furthermore, by optimizing the slit width of the linear slit-shaped light transmitting hole group 6, even when the incident angle Q1 = 0 ° shown in FIG. 9A, the incident angle Q1 = 80 shown in FIG. Also in the case of °, it is possible to condense all the incident light to the linear slit-shaped light transmitting hole group 6, and it is possible to realize higher power generation efficiency. Detailed examination results will be described later.
[0104]
【Example】
[Example 1]
Example 1 of the present invention will be described below with reference to FIG. 1 and FIG. 2 for the solar cell shown in FIG.
[0105]
The solar cell element 2 shown in FIG. 1 or FIG. 2 was manufactured by a method similar to the conventional method.
The manufacturing method is described below.
[0106]
As shown in FIG. 2, a solar cell element composed of a substrate 1 and a photoelectric conversion layer 2 is formed on a stainless steel substrate 1 also serving as a support, by a 100-nm thick Al film having a light reflection effect. _0.95 Ti _0.05 After the electrode metal layer 9 made of an alloy is formed by sputtering, a p-type or n-type conductivity type impurity provided in order to improve the electrical contact between the electrode metal layer 9 and the semiconductor layer has a high concentration. The doped polycrystalline Si semiconductor layer 10, the polycrystalline Si semiconductor layer 11, which is slightly doped with impurities of the same conductivity type as the polycrystalline Si semiconductor layer 10, and the conductivity type impurities opposite to the polycrystalline Si semiconductor layers 10, 11 are increased. A polycrystalline Si semiconductor layer 12 doped at a certain concentration was sequentially formed by a plasma CVD apparatus.
[0107]
The polycrystalline Si semiconductor layer 10 is made of SiH at a substrate temperature of 250 ° C. ₄ Gas, H ₂ Gas, PH ₃ A mixed gas having an optimized gas mixing ratio was introduced into a CVD apparatus, and the gas pressure was set to 20 Pa, and a high-frequency power of 100 W was applied to form the gas. Thus, a polycrystalline Si semiconductor layer 10 with a thickness of 30 nm doped with P at a high concentration was deposited on the electrode metal layer 9.
[0108]
Next, the polycrystalline Si semiconductor layer 11 is made of SiH at a substrate temperature of 550 ° C. ₄ Gas, H ₂ Gas, PH ₃ A mixed gas having an optimized gas mixing ratio was introduced into a CVD apparatus, and a gas pressure of 50 Pa was applied thereto, and a high-frequency power of 350 W was applied to form a gas. Thus, a 150 nm-thick polycrystalline Si semiconductor layer 11 lightly doped with P was deposited on the polycrystalline Si semiconductor layer 10.
[0109]
In a conventional solar cell, the polycrystalline Si semiconductor layer 11 is a layer that absorbs light, generates electric charges, and generates power. In order to sufficiently absorb light, the thickness is usually set to be 5000 nm or more and 50000 nm or less. On the other hand, in the present invention, since the incident light from the linear slit-shaped light transmitting hole group 6 is multiple-reflected between the photoelectric conversion layer 2 and the light reflection layer 5 of the solar cell element, the efficiency is improved. Since light can be absorbed into the polycrystalline Si semiconductor layer 11, the thickness of the polycrystalline Si semiconductor layer 11 can be reduced. That is, high power generation efficiency can be obtained even when the film thickness is as thin as 100 nm or more and 3000 nm or less. Therefore, the time for forming the polycrystalline Si semiconductor layer 13 can be significantly reduced, and the cost of the solar cell can be reduced.
[0110]
Next, the polycrystalline Si semiconductor layer 12 is made of SiH at a substrate temperature of 350 ° C. ₄ Gas, H ₂ Gas, BF ₃ A mixed gas having an optimized gas mixing ratio was introduced into a CVD apparatus, and a gas pressure of 50 Pa was applied thereto, and a high-frequency power of 100 W was applied to form the gas. On the polycrystalline Si semiconductor layer 11, a p-type polycrystalline Si semiconductor layer 12 doped with B and having a thickness of 15 nm was deposited.
[0111]
Next, the substrate 1 on which a pn junction composed of the polycrystalline Si semiconductor layers 10 to 12 is formed is attached to a sputtering apparatus, and a shielding mask corresponding to the shape of the comb-shaped current collecting electrode 13 is provided on the substrate 1. While being mounted on the surface of the layer 12, a 100 nm thick Al _0.95 Ti _0.05 A comb-shaped current collecting electrode 13 having a width of 0.1 mm and an interval of 5 mm made of an alloy was formed.
[0112]
Finally, In ₂ O ₃ By conducting reactive sputtering in an oxygen atmosphere using a target, a conductive transparent film 14 having a thickness of 65 nm was formed on the polycrystalline Si semiconductor layer 12 and the current collecting electrode 13.
[0113]
On the other hand, the light-collecting device including the light-incident-side first transparent member 8, the solar cell-device-side second transparent member 3, and the cylindrical condensing curved surface group 4 in FIG. 1 was manufactured as follows.
[0114]
First, a solar cell element-side second transparent body 3 made of lead glass having a cylindrical condensing curved surface group 4 on one side and a flat surface on the other side was formed by a roll method.
The solar cell element-side second transparent body 3 had a refractive index of 1.9. The cylindrical light-collecting curved surface group 4 has a configuration in which cylindrical light-collecting curved surfaces having a curvature radius of 10 mm are arranged at an interval of 12 mm in width.
[0115]
Next, with the shielding mask corresponding to the linear slit-shaped light transmitting hole group 6 mounted on the flat surface of the solar cell element-side second transparent body 3, sputtering using an AlTi alloy target was performed to form a film thickness. 100nm Al _0.95 Ti _0.05 A light reflecting layer 5 made of an alloy was formed, and a group of straight slit light transmitting holes 6 was also formed. The slit width WS of the linear slit-shaped light transmitting hole group 6 was set to 1/6 of the width W of the cylindrical condensing curved surface group 4 (WS = 2 mm).
[0116]
Next, a transparent fluororesin using fluorovinyl ether was coated in a molten state so as to cover the cylindrical converging curved surface group 4 of the second transparent body 3 on the solar cell element side, and the light incident surface side was formed flat. Thereafter, the first transparent body 8 on the light incident side was formed by cooling and solidifying. The light incident side first transparent body 8 had a refractive index of 1.4 and a thickness of 0.5 mm at the thinnest part.
[0117]
A spacer was provided at an outer edge portion between the solar cell element and the second transparent body 3 on the solar cell element side, and the spacer was fixedly arranged so that the interval between them was 10 mm, and the power generation efficiency was examined.
[0118]
Here, the solar cell shown in FIG. 5 in which the first transparent body 8 on the light incident side is not formed is referred to as Comparative Example 1, and the solar cell including only the solar cell element without the light condensing element is referred to as Comparative Example 01, and the power generation efficiency is similarly calculated. investigated.
[0119]
[Table 1]

[0120]
Table 1 shows that, with respect to the solar cell of Example 1, when the position where the linear slit-shaped light transmitting hole group 6 is formed, that is, the thickness d of the second transparent body 3 on the solar cell element side is changed, the incident angle Q of light is changed. It is also a result of examining how the power generation efficiency changes. In Comparative Example 1, since the light incident side first transparent body 8 does not exist, the focal length of the cylindrical condensing curved surface group 4 is 20 mm, and the thickness of the solar cell element side second transparent body 3 is The focal length of the cylindrical condensing curved surface group 4 was set to 20 mm.
[0121]
In Example 1, the investigation was performed in a range where the thickness d of the second solar cell element-side transparent body 3 was smaller than the focal length of the cylindrical condensing curved surface group 4 of 34 mm. As a light source, 100 mW / cm ² Irradiation was performed while changing the incident angle Q.
[0122]
Table 1 shows that the open-circuit voltage V and the short-circuit current of the solar cells of Example 1 and Comparative Example 1 were set to 100% when the open-circuit voltage V and the short-circuit current I of the solar cell of Comparative Example 01 were arranged side by side during the power generation efficiency investigation. The result which compared the magnitude | size of I with the comparative example 01 is shown.
[0123]
In Comparative Example 1, when the incident angle Q = 0 °, all the incident light is condensed on the linear slit-shaped light transmitting hole group 6, thereby realizing higher power generation efficiency than the solar cell of Comparative Example 01. Has been made. However, it can be seen that the power generation efficiency sharply decreases as the incident angle increases, and that at an incident angle Q = 80 °, only the open-circuit voltage and the short-circuit current of about 20% of Comparative Example 01 can be obtained.
[0124]
Next, in Example 1, when d = 34 mm where the plate thickness d of the solar cell element-side second transparent body 3 was equal to the focal length F of the cylindrical condensing curved surface group 4, the incident light was higher than that in Comparative Example 1. It can be seen that the power generation efficiency is greatly improved when the angle is increased. Further, when Q = 80 °, the power generation efficiency is slightly deteriorated as compared with the solar cell of Comparative Example 01, but the time zone when the power generation amount is large, that is, when the incident angle is small Q = 0 ° or Q At = 40 °, high power generation efficiency was realized, and in consideration of the total power generation per day, a larger power generation could be obtained as compared with the solar cell of Comparative Example 01.
[0125]
Further, as a result of investigating solar cells having different plate thicknesses d, as shown in Table 1, by setting the plate thickness d to 22 mm or more and 32 mm or less, at all incident angles, the open-circuit voltage was larger than that of Comparative Example 01. It was confirmed that a short-circuit current could be obtained.
[0126]
When the plate thickness d of the solar cell element-side second transparent body 3 is further reduced to 18 mm, the light is condensed to the linear slit-shaped light transmitting hole group 6 in a time zone in which the amount of generated power is large, that is, in a range where the incident angle is small. Light and the open-circuit voltage and short-circuit current are reduced. This is because, in a range where the incident angle is small, the position of the linear slit-shaped light transmitting hole group 6 is too close to the cylindrical condensing curved surface group 4 from the condensing position, so that the spread luminous flux before being condensed is reduced. This is because the linear slit light transmitting hole group 6 is irradiated.
[0127]
As described above, when the focal length F is 34 mm and the plate thickness d is in the range of 22 mm (11F / 17) or more and 32 mm (16F / 17) or less, Comparative Example 01 is obtained in all incident angles. Larger open voltage and short circuit current can be obtained.
[0128]
Next, with the plate thickness d fixed at the optimum position, that is, at the position of 28 mm, the slit voltage WS of the linear slit-shaped light transmitting hole group 6 was changed, and the open-circuit voltage V and the short-circuit current I were investigated. It is shown in FIG.
[0129]
[Table 2]

[0130]
As shown in Table 2, while the width W of the cylindrical condensing curved surface group 4 is 12 mm, the slit width WS is set to 1.5 mm (W / 8) or more, and 8.0 mm (2 W / 3) or less. As a result, an open-circuit voltage V and a short-circuit current I larger than those in Comparative Example 01 were obtained in all the incident angle ranges.
[0131]
When the slit width WS is smaller than W / 8, a part of the collected light is reflected by the light reflection layer 5 and does not reach the solar cell element, which leads to a decrease in power generation efficiency. Further, when the slit width WS is larger than 2W / 3, light incident from the linear slit-shaped light transmitting hole group 6 is radiated again from the linear slit-shaped light transmitting hole group 6, and the efficiency of multiple reflection is reduced. This leads to lower power generation efficiency.
[0132]
As described above, in the solar cell of the present invention, the distance (d) from the surface of the cylindrical converging curved surface group 4 to the linear slit-shaped light transmitting hole group 6 is defined as F, where F is the focal length of the cylindrical converging curved surface group 4. ) Is preferably at least (11F / 17) or more and (16F / 17) or less. Further, it is desirable that the width of the cylindrical condensing curved surface group 4 is W, and the slit width WS of the linear slit light transmitting hole group 6 is (W / 8) or more and (2W / 3) or less.
[0133]
By the way, in the present embodiment, the configuration in which the spacer is provided on the outer edge portion between the solar cell element-side second transparent body 3 and the solar cell element and both are fixedly arranged at a predetermined interval has been described. However, the present invention is not limited thereto, and the solar cell element-side second transparent body 3 and the solar cell element may be bonded and fixed using a transparent adhesive such as an ultraviolet curable resin. This makes it possible to more securely fix the light-collecting element and the solar cell element, thereby improving the reliability of the solar cell.
[0134]
Here, in order to realize stable multiple reflection between the photoelectric conversion layer 2 and the light reflection layer 5 of the solar cell element, light reflected by the photoelectric conversion layer 2 is immediately transmitted from the light transmission hole group 6. The transparent adhesive layer preferably has a thickness of 2 mm or more so as not to leak out. Further, when the ultraviolet curable resin is too thick, the time for curing the resin becomes longer, and the throughput of solar cell production is reduced. Therefore, it is desirable that the thickness of the ultraviolet curable resin layer be 15 mm or less.
[0135]
Further, the power generation efficiency can be further increased by bonding and fixing the solar cell element-side second transparent body 3 and the solar cell element using an ultraviolet curable resin in which fluorescent fine particles are dispersed. For example, Y having a particle size of 5 μm ₂ O ₂ S: 10% by volume of Eu, Mg, Ti fluorescent particles are contained in the ultraviolet curable resin, and the second transparent body 3 on the solar cell element side and the solar cell element are bonded and fixed using the ultraviolet curable resin having a thickness of 5 mm. A solar cell was manufactured. The fluorescent particles convert light having a wavelength of about 400 nm, which is not used for photoelectric conversion, into light having a wavelength of about 600 nm, which is used for photoelectric conversion. By repeating absorption and partial reflection between the layer 5 and the photoelectric conversion layer 2, the power generation efficiency of the solar cell can be increased.
[0136]
A solar cell in which a light-collecting element and a solar cell element are bonded and fixed using an ultraviolet-curable resin containing no fluorescent particles, and a light-collecting element and a solar cell element are bonded using an ultraviolet-curable resin containing fluorescent particles. 100 mW / cm using the solar simulator with respect to the fixed solar cell ² Of light having an incident angle of 0 °, 40 °, and 80 °, and comparing the open-circuit voltage V and the short-circuit current I of both, as a result of including fluorescent particles, at all incident angles, It was confirmed that the open-circuit voltage V increased by about 13% and the short-circuit current I increased by about 11%.
[0137]
In the solar cell described in Example 1, as shown in FIG. 2, an electrode metal layer 9, a polycrystalline Si semiconductor layer 10, a polycrystalline Si semiconductor layer 11, and a polycrystalline Si semiconductor layer 12 were formed on a stainless steel substrate 1. Although a polycrystalline Si solar cell in which the collector electrode 13 and the conductive transparent film 14 are formed was used, the present invention is not limited to this. That is, it is possible to use the amorphous Si solar cell element shown in FIG. 18 as the solar cell element. Further, in order to further increase the power generation efficiency, a pn junction formed of a polycrystalline semiconductor shown in FIG. It is also possible to use a tandem solar cell element in which a pin junction made of an amorphous semiconductor shown in FIG. 18 is laminated.
[0138]
In the solar cell described in Example 1, the light incident side first transparent body 8 made of a transparent fluororesin and the solar cell element side second transparent body 3 made of lead glass were used as the condensing element. However, it is not limited to this. That is, if the refractive index of air is n0, the refractive index of the first transparent body 8 on the light incident side is n1, and the refractive index of the second transparent body 3 on the solar cell element side is n2, n0 <n1 <n2. The light incident side first transparent body 8 and the solar cell element side second transparent body 3 are made of such a material, so that the light incident side first transparent body 8 has an incident angle with respect to the cylindrical condensing curved surface group 4. It can function as a light-concentrating auxiliary layer for reducing the size.
[0139]
In the solar cell described in Example 1, a group of condensed curved surfaces having a constant radius of curvature was used as the group of cylindrical condensed curved surfaces 4, but the present invention is not limited to this. If sunlight can be efficiently condensed onto the linear slit-shaped light transmitting hole group 6, it is also possible to arrange the light collecting curved surfaces having different radii of curvature in combination.
[0140]
In the solar cell described in Example 1, Y having a particle size of 5 μm was used as the fluorescent particles. ₂ O ₂ S: An example using fluorescent particles of Eu, Mg, and Ti has been described, but the present invention is not limited to this.
[0141]
For example, as fluorescent particles, Y having a particle size of 2 to 20 μm is used. ₂ O ₂ By using S: Eu, Mg, Ti sex fluorescent particles, it is possible to absorb light having a wavelength of 200 to 450 nm and emit light having a wavelength of 625 nm. Also, Er ³⁺ By using the oxyfluoride-based crystallized glass containing ions, light having a wavelength of about 800 nm can be absorbed and light having a wavelength of 550 to 660 nm can be emitted.
[0142]
Other fluorescent materials include SrAl in which rare earth elements europium (Eu) and dysprosium (Dy) are added to a compound composed of strontium oxide and aluminum oxide. ₂ O ₄ : Eu, Dy and Sr ₄ Al ₁₄ O ₂₅ : Eu, Dy, CaAl ₂ O ₄ : Eu, Dy, and a fluorescent material such as ZnS: Cu can also be used.
[0143]
In addition, by including an organic dye such as a cyanine dye, a pyridine dye, and a rhodamine dye, it is also possible to convert short-wavelength light into long-wavelength light, thereby increasing power generation efficiency. It is possible.
[0144]
Furthermore, higher power generation efficiency can be obtained by using a plurality of these fluorescent materials simultaneously in an arbitrary combination.
[0145]
[Example 2]
The following describes the solar cell shown in FIG. 10 as Embodiment 2 of the present invention.
[0146]
The solar cell according to the second embodiment includes a light incident side first transparent body 8, a solar cell element side second transparent body 3, and a light reflecting layer 5 having a light transmitting hole group 6 described in the first embodiment. A transparent substrate 17 is provided between the element and a solar cell element including the substrate 1 and the photoelectric conversion layer 2.
[0147]
The sunlight incident from the incident side first transparent body 8 is condensed by the group of cylindrical condensing curved surfaces 4 into the group of linear slit-shaped light transmitting holes 6, passes through the transparent substrate 17, and then to the photoelectric conversion layer 2. Incident. Subsequently, the reflected light from the photoelectric conversion layer 2 is reflected by the light reflection layer 5 and reenters the photoelectric conversion layer 2. Thereby, multiple reflection of the incident light 7 is realized between the light reflection layer 5 and the photoelectric conversion layer 2, and the power generation efficiency can be increased.
[0148]
In Example 1, since the light-collecting element and the solar cell element were directly fixed with the ultraviolet curing resin, it was necessary to increase the thickness of the ultraviolet curing resin to at least 2 mm or more, and it took a long time to cure the ultraviolet curing resin. Needed. On the other hand, in the second embodiment, by adjusting the thickness of the transparent substrate 17, it is possible to control the distance between the light-collecting element and the solar cell element. can do.
[0149]
For example, a glass plate having a thickness of 5 mm is adopted as the transparent substrate 17, and a 20 μm-thick ultraviolet curable resin layer is provided between the condensing element and the transparent substrate 17 and between the solar cell element and the transparent substrate 17. The solar cell in which the light-collecting element, the transparent substrate 17 and the solar cell element were bonded and fixed was examined for power generation efficiency in the same manner as in Example 1. As a result, almost the same open-circuit voltage V and short-circuit current I as in Example 1 were obtained, and even in the configuration of Example 2, the power generation efficiency of the solar cell could be increased.
[0150]
Next, as the transparent substrate 17, Y having a particle size of 5 μm was used. ₂ O ₂ S: A solar cell was produced using a transparent substrate 17 containing 15% by volume of Eu, Mg, and Ti fluorescent particles.
The fluorescent particles convert light near the wavelength of 400 nm that is not used for photoelectric conversion into light near the wavelength of 600 nm that is used for photoelectric conversion. Then, light having a wavelength of about 600 nm generated from the fluorescent particles is repeatedly absorbed and partially reflected between the light-collecting element and the solar cell element, whereby the power generation efficiency of the solar cell can be increased.
[0151]
A solar cell using the transparent substrate 17 containing no fluorescent particles and a solar cell using the transparent substrate 17 containing the fluorescent particles were subjected to 100 mW / cm using a solar simulator. ² Of light having an incident angle of 0 °, 40 °, and 80 °, and the open-circuit voltage V and the short-circuit current I were compared. As a result, it was confirmed that the use of the transparent substrate 17 containing the fluorescent particles increased the open-circuit voltage V by about 20% and increased the short-circuit current I by about 16% at all incident angles.
[0152]
Next, Y of 5 μm in particle diameter was applied to an ultraviolet curable resin for bonding and fixing the light collecting element, the transparent substrate 17 and the solar cell element. ₂ O ₂ S: A solar cell having the structure of Example 2 containing 10% by volume of Eu, Mg, and Ti fluorescent particles was produced.
[0153]
A solar cell in which a light-collecting element, a transparent substrate 17 and a solar cell element are bonded and fixed using an ultraviolet-curable resin containing no fluorescent particles, and a light-collecting element and a transparent substrate are used using an ultraviolet-curable resin containing fluorescent particles. 17 and a solar cell having a solar cell element bonded and fixed thereto, using a solar simulator to obtain 100 mW / cm. ² Of light having an incident angle of 0 °, 40 °, and 80 °, and the open-circuit voltage V and the short-circuit current I were compared. As a result, it was confirmed that by including the fluorescent particles in the ultraviolet curable resin, the open-circuit voltage V increased by about 8% and the short-circuit current I increased by about 6% at all incident angles.
[0154]
Here, the configuration in which the fluorescent particles are independently contained in the transparent substrate 17 and the ultraviolet curable resin was investigated. However, even when the fluorescent particles are contained in both the transparent substrate 17 and the ultraviolet curable resin, the structure is further opened. It is possible to increase the voltage V and the short-circuit current I.
[0155]
In the solar cell described in Example 2, the same solar cell element, light-collecting element, cylindrical light-collecting curved surface group, and fluorescent particles as those in Example 1 were used. However, the present invention is not limited to this as described in (1).
[0156]
[Example 3]
The following describes the solar cell shown in FIG. 11 as Embodiment 3 of the present invention.
[0157]
The solar cell according to the third embodiment includes a condensing element having a cylindrical condensing curved surface group 4 composed of a light incident side first transparent body 8 and a solar cell element side second transparent body 3, and a light transmitting hole group 6. And a solar cell element having the substrate 1 and the photoelectric conversion layer 2. That is, the light reflecting layer 5 having the light transmitting hole group 6 is formed on the light incident side surface of the transparent substrate 17 instead of the light emitting side surface of the solar cell element side second transparent body 3. I have.
[0158]
As the transparent substrate 18, a glass plate having a thickness of 5 mm was employed. In this case, the incident light 7 incident from the light incident side first transparent body 8 is condensed by the group of cylindrical condensing curved surfaces 4 on the group of linear slit-shaped light transmitting holes 6 formed on the transparent substrate 18 and becomes transparent. After passing through the substrate 18, the light enters the photoelectric conversion layer 2. Subsequently, the reflected light from the photoelectric conversion layer 2 is reflected by the light reflection layer 5 and reenters the photoelectric conversion layer 2.
[0159]
Also in this case, as in the first embodiment, by optimizing the distance between the cylindrical condensing curved surface group 4 and the light reflecting layer 5 having the linear slit-shaped light transmitting hole group 6, the same as in the first embodiment, Open voltage V and short-circuit current I were obtained.
[0160]
In Example 1 and Example 2, a linear slit-shaped light transmitting hole group 6 was formed on one side of the solar cell element side of the solar cell element side second transparent body 3 on which the cylindrical condensing curved surface group 4 was formed. The light reflection layer 5 having the same was formed. For this reason, when forming the light reflection layer 5 or patterning the light transmission hole group 6, a defect such as a scratch is generated in the light collection curved surface group 4, which causes a reduction in light collection efficiency.
[0161]
On the other hand, according to the configuration of this embodiment, the light-collecting element having the cylindrical light-collecting curved surface group 4 and the transparent substrate 18 having the linear slit-shaped light transmitting hole group 6 and the light reflecting layer 5 are separately provided. Can be made. As a result, the probability that defects such as scratches occur in the light-collecting element is reduced, and a solar cell with high power generation efficiency with high reproducibility can be manufactured.
[0162]
Next, as the transparent substrate 18, Y having a particle size of 5 μm was used. ₂ O ₂ S: A solar cell was produced using the transparent substrate 18 containing 15% by volume of Eu, Mg, and Ti fluorescent particles.
The function of improving the power generation efficiency by the fluorescent particles is as described in the above embodiment.
[0163]
The solar cell using the transparent substrate 18 containing no fluorescent particles and the solar cell using the transparent substrate 18 containing the fluorescent particles were measured for 100 mW / cm using a solar simulator. ² Of light having an incident angle of 0 °, 40 °, and 80 °, and the open-circuit voltage V and the short-circuit current I were compared. As a result, it was confirmed that the use of the transparent substrate 18 containing the fluorescent particles increased the open-circuit voltage V by about 21% and increased the short-circuit current I by about 18% at all incident angles.
[0164]
Next, an ultraviolet curable resin for bonding and fixing the transparent substrate 18 and the solar cell element is coated with Y having a particle diameter of 5 μm. ₂ O ₂ S: A solar cell having a configuration of Example 3 containing 10% by volume of Eu, Mg, and Ti fluorescent particles was produced.
[0165]
Further, when the light condensing element and the transparent substrate 18 are bonded and fixed, the layer of the ultraviolet curing resin exists on the light incident side of the light transmitting hole group 6. Therefore, it is necessary to use an ultraviolet curable resin containing no fluorescent particles. This is because, if fluorescent particles are contained in an ultraviolet curable resin that adheres and fixes the light-collecting element and the transparent substrate 18, incident light is scattered by the fluorescent particles, and the light-collecting efficiency to the light transmitting hole group 6 is reduced. Because.
[0166]
In the performance measurement, a transparent substrate 18 and a solar cell were bonded and fixed using a UV curable resin containing no fluorescent particles, and a transparent substrate 18 and a solar cell were bonded using a UV curable resin containing fluorescent particles. A comparison was made with a solar cell in which the element was bonded and fixed. That is, using a solar simulator, 100 mW / cm ² The light having the intensities described above was incident on the respective solar cells with the incident angles Q being 0 °, 40 °, and 80 °, and the open-circuit voltage V and the short-circuit current I of both were compared. As a result, it was confirmed that by including the fluorescent particles in the ultraviolet curable resin, the open-circuit voltage V increased by about 8% and the short-circuit current I increased by about 6% at all incident angles.
[0167]
Here, the structure in which the transparent substrate 18 and the ultraviolet curable resin contain fluorescent particles was separately investigated. However, by including the fluorescent particles in both the transparent substrate 18 and the ultraviolet curable resin, the open-circuit voltage V The short-circuit current I can be further increased.
[0168]
In the solar cell described in Example 3, the same solar cell element, light-collecting element, cylindrical light-collecting curved surface group, and fluorescent particles as in Example 1 were used. It is not limited.
[0169]
[Example 4]
The following describes the solar cell shown in FIG. 12 as Embodiment 4 of the present invention.
[0170]
The solar cell according to the fourth embodiment includes a light-collecting element described in the first embodiment, that is, a light-incident-side first transparent body 8 and a solar-cell-element-side second transparent body 3 having a cylindrical condensing curved surface group 4, The light-condensing element includes the light-reflecting layer 5 having the light-transmitting hole group 6 and the solar cell element including the transparent substrate 19 for a solar cell element and the photoelectric conversion layer 20. The difference from Example 1 is that the stacking order of the solar cell element transparent substrate 19 and the photoelectric conversion layer 20 in the light traveling direction in the present example is opposite to the stacking order of the substrate 1 and the photoelectric conversion layer 2 in Example 1. It is becoming.
[0171]
In the above configuration, the light incident from the light incident side first transparent body 8 is condensed on the linear slit light transmitting hole group 6 by the cylindrical condensing curved surface group 4 and transmitted through the solar cell element transparent substrate 19. Then, the light enters the photoelectric conversion layer 20. On the other hand, the reflected light from the photoelectric conversion layer 20 is reflected by the light reflection layer 5 and reenters the photoelectric conversion layer 20.
[0172]
The solar cell element of Example 4 had a configuration as shown in FIG. 13 and was manufactured as follows.
[0173]
A 30 nm-thick SnO film is formed on a transparent substrate 19 ₂ After the transparent conductive layer 21 is formed by reactive sputtering, the shielding mask is mounted on the surface of the transparent conductive layer 21 formed on the substrate 19, and the Al mask having a thickness of 100 nm is formed by sputtering using an AlTi alloy target. _0.95 Ti _0.05 A comb-shaped current collecting electrode 22 made of an alloy and having a width of 0.1 mm and an interval of 5 mm was formed.
[0174]
Next, a photoelectric conversion layer in which a p-layer 23 as a p-type impurity-doped semiconductor layer, an i-layer 24 as an intrinsic semiconductor, and an n-layer 25 as an n-type impurity-doped layer are stacked in this order is vapor-phase grown by a plasma CVD apparatus. Formed by the method. Each semiconductor layer is made of SiH ₄ Gas H ₂ Gas / CH ₄ Gas B ₂ H ₆ A-SiC: H p-layer 23 with a thickness of 15 nm grown by vapor phase using a gas mixture of SiH ₄ Gas H ₂ A-Si: H i-layer 24 having a thickness of 100 nm grown by vapor phase using a mixed gas of SiH ₄ Gas H ₂ Gas / PH ₃ An n-layer 25 of a-Si: H having a film thickness of 15 nm was formed by vapor phase growth using a gas mixture.
[0175]
After forming each layer as described above, a 100 nm thick Al _0.95 Ti _0.05 An electrode metal layer 26 made of an alloy and having a light reflection effect was formed by sputtering. Finally, an ultraviolet curable resin was applied on the electrode metal layer 26 to complete the solar cell element as the protective film 27 of the electrode metal layer 26.
[0176]
The light-collecting element and the solar cell element were bonded and fixed using an ultraviolet curable resin in the same manner as in Example 1 to obtain a solar cell of Example 4.
[0177]
In the solar cell of Example 4, the solar cell not provided with the light incident side first transparent body 8 is referred to as Comparative Example 4, and the solar cell including only the solar cell element not provided with the light collecting element is referred to as Comparative Example 04. The power generation efficiency of the solar cell of Example 4 was compared in the same manner as in Example 1. That is, when the plate thickness d of the second transparent body 3 on the solar cell element side in Example 4 was changed, it was examined how the power generation efficiency changes with the incident angle Q of light.
[0178]
[Table 3]

[0179]
Table 3 compares the magnitudes of the open-circuit voltage V and the short-circuit current I of the solar cells of Example 4 and Comparative Example 4 with the open-circuit voltage V and the short-circuit current I of the solar cell element of Comparative Example 04 being 100%, respectively. 19 shows the result of comparison with Example 04.
[0180]
The light-collecting device of Example 4 is the same as that of Example 1, and it can be seen that the same result as that of Example 1 was obtained also in the solar cell of Example 4.
[0181]
That is, assuming that the focal length of the cylindrical converging curved surface group 4 is F, the distance (d) from the surface of the cylindrical converging curved surface group 4 to the linear slit light transmitting hole group 6 is at least (11F / 17) or more. , (16F / 17) or less.
[0182]
Further, as in the first embodiment, the power generation efficiency can be further increased by bonding and fixing the light-collecting element and the solar cell element using an ultraviolet curable resin in which fluorescent fine particles are dispersed. Y with a particle size of 5 μm ₂ O ₂ S: Producing a solar cell in which fluorescent particles of Eu, Mg, and Ti are contained in an ultraviolet curable resin at 10% by volume, and a light-collecting element and a solar cell element are adhered and fixed using the ultraviolet curable resin having a thickness of 5 mm. did.
[0183]
Then, using a UV curable resin containing no fluorescent particles, a solar cell in which the light-collecting element and the solar cell element are bonded and fixed, and a light-collecting element and a solar cell element using the UV curable resin containing the fluorescent particles 100 mW / cm using a solar simulator with respect to a solar cell having ² Of light having an incident angle of 0 °, 40 °, and 80 °, and the open-circuit voltage V and the short-circuit current I were compared. As a result, it was confirmed that the inclusion of the fluorescent particles increased the open-circuit voltage V by 16% and the short-circuit current I by 14% at all incident angles.
[0184]
In Example 4, the power generation efficiency can be similarly improved by using fluorescent glass containing a fluorescent material as the transparent substrate 19 for a solar cell element.
[0185]
In the solar cell of Example 4 shown in FIG. ₂ O ₂ S: A solar cell was manufactured using a glass substrate containing 15% by volume of fluorescent particles of Eu, Mg, and Ti.
[0186]
Then, the solar cell using the transparent substrate 19 for the solar cell element containing no fluorescent particles and the solar cell using the transparent substrate 19 for the solar cell element containing the fluorescent particles were subjected to 100 mW using a solar simulator. / Cm ² Of light having an incident angle of 0 °, 40 °, and 80 °, and the open-circuit voltage V and the short-circuit current I were compared. As a result, it was confirmed that the open-circuit voltage V was increased by 20% and the short-circuit current I was increased by 16% by using the solar cell element transparent substrate 19 containing the fluorescent particles at all incident angles.
[0187]
Here, the structure in which fluorescent particles were contained in the transparent substrate for solar cell element 19 and the ultraviolet curable resin was separately investigated. However, by including fluorescent particles in both the solar cell element transparent substrate 19 and the ultraviolet curable resin, the open-circuit voltage V and the short-circuit current I can be further increased.
[0188]
In the above embodiment, the configuration in which the light reflecting layer 5 having the linear slit-shaped light transmitting hole group 6 is provided on one surface of the solar cell element-side second transparent body 3 has been described, but as shown in FIG. Even when the light reflection layer 5 having the linear slit-shaped light transmission hole group 6 is provided on the light incident surface of the transparent substrate 19 for a solar cell element, the power generation efficiency can be similarly improved. . In this case, even higher power generation efficiency can be realized by using a substrate having a fluorescent property as the solar cell element transparent substrate 19 located closer to the photoelectric conversion layer 20 than the light reflection layer 5.
[0189]
In addition, as shown in FIG. 15, light having a linear slit-shaped light transmission hole group 6 between the solar cell element side second transparent body 3 of the light condensing element and the solar cell element transparent substrate 19 of the solar cell element. By inserting the transparent substrate 28 on which the reflective layer 5 is formed and fixing the light-collecting element, the transparent substrate 28, and the solar cell element, the power generation efficiency can be similarly improved.
[0190]
With such a configuration, the solar cell element and the transparent substrate 28 having the light condensing element and the light reflection layer 5 can be separately manufactured, and the manufacturing yield of the solar cell panel can be improved.
[0191]
In this case, higher power generation efficiency can be realized by using a substrate having a fluorescent property as the transparent substrate 28 or the transparent substrate 19 for a solar cell element which is present on the photoelectric conversion layer 20 side of the light reflection layer 5. . When fixing the light-collecting element, the transparent substrate 28, and the solar cell element using a transparent adhesive such as an ultraviolet curable resin, the transparent adhesive that fixes the transparent substrate 28 and the solar cell element contains fluorescent particles. By doing so, higher power generation efficiency can be realized.
[0192]
Also, as shown in FIG. 16, even when the transparent substrate 28 in FIG. 15 is turned upside down and the light reflection layer 5 is present on the solar cell element side, the power generation efficiency can be similarly improved.
[0193]
In the solar cell of Example 4, a transparent conductive layer 21, a comb-shaped current collecting electrode 22, a p-layer 23 as a p-type impurity-doped semiconductor layer, and an i-layer as an intrinsic semiconductor were formed on a transparent substrate 19 for a solar cell element. Although an amorphous Si solar cell including an n-type impurity doped layer 24, an n-type impurity doped layer 25, an electrode metal layer 26, and a protective film 27 was used, the present invention is not limited to this. As the solar cell element, a polycrystalline Si solar cell element can be used. In order to further increase the power generation efficiency, a pn junction made of a polycrystalline semiconductor and a pin junction made of an amorphous semiconductor are stacked. It is also possible to use a tandem-structure solar cell element described above.
[0194]
In the solar cell described in Example 4, a light-collecting element, a cylindrical condensed curved surface group, and fluorescent particles similar to those in the solar cell described in Example 1 were used. It is not limited to.
[0195]
Although not included in the claims, as shown in FIGS. 1, 3, 10, and 12, the light-collecting region of the second transparent body on one side of the light-collecting element and on the solar cell element side The present invention also includes a configuration in which a light reflecting layer having a light transmitting hole is provided on the light emitting surface facing the light emitting surface.
[0196]
In this configuration, as shown in FIG. 10, a transparent substrate may be provided between the solar cell element and the light-collecting element provided with the light-collecting region and the light reflecting layer.
[0197]
Further, the solar cell element may be a solar cell element having a photoelectric conversion layer provided on a transparent substrate as shown in FIGS.
[0198]
Further, as shown in FIG. 14, a light reflecting layer having the light transmitting holes may be provided on a surface of the transparent substrate of the solar cell element facing the photoelectric conversion layer.
[0199]
According to the above configuration, in any case, the light condensed by the light condensing region enters between the light reflection layer provided in the light condensing element and the solar cell element via the light transmitting hole. Therefore, multiple reflection occurs between the photoelectric conversion layer and the light reflection layer. Therefore, the amount of light irradiated to the photoelectric conversion layer increases, and the power generation efficiency can be increased.
[0200]
In addition, it is possible to form both the photoelectric conversion layer and the light reflection layer on the transparent substrate of the solar cell element, and it is possible to manufacture a solar cell with the minimum necessary number of substrates. In addition, the cost of the solar cell can be reduced, and the thickness of the solar cell can be reduced.
[0201]
Further, as shown in FIGS. 11, 15, and 16, a transparent substrate is provided between the light-collecting element and the solar cell element, and a light reflection hole having a light-transmitting hole formed on one surface of the transparent substrate. A configuration in which a layer is provided is also included in the present invention.
[0202]
This makes it possible to separately manufacture the light-collecting element, the solar cell element, and the transparent substrate on which the light-reflecting layer having light-transmitting holes is formed. A solar cell having power generation efficiency can be stably manufactured.
[0203]
In the solar cell of the present invention, the light-collecting element and the solar cell element, or the light-collecting element and the solar cell element, and the transparent substrate provided therebetween are fixed with a transparent adhesive. It may be.
[0204]
Therefore, the light-collecting element and the solar cell element, or the light-collecting element, the transparent substrate, and the solar cell element are firmly fixed by a transparent adhesive to increase the strength of the solar cell. Becomes possible.
[0205]
The present invention is not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the claims, and the technical means disclosed in the different embodiments and examples may be appropriately changed. Embodiments and examples obtained in combination are also included in the technical scope of the present invention.
[0206]
【The invention's effect】
As described above, the solar cell according to the present invention has a solar cell element having a photoelectric conversion layer, a light incident side first transparent body having a refractive index higher than air, and a refractive index higher than the light incident side first transparent body. And a light-reflecting layer having a light-transmitting hole, the light-reflecting layer being condensed by the light-collecting region. After the light passes through the light transmitting hole, the light enters the solar cell element, and the reflected light from the solar cell element is reflected by the light reflection layer and re-enters the solar cell element, so that the solar cell element and the light condensing element It is characterized by being formed between.
[0207]
Therefore, since the light transmitted through the first transparent body is incident on the light-collecting region, the angle of incidence is smaller than when the first transparent body is not provided. Therefore, it is possible to narrow the light beam formed by the collected light.
[0208]
This makes it easy for the light beam to pass through the light transmitting hole without irradiating the periphery of the light transmitting hole, so that the amount of light introduced between the light reflecting layer and the solar cell element can be increased. As a result, power generation efficiency can be increased.
[0209]
Further, at least a part of the reflected light reflected on the surface or inside of the solar cell element is reflected on a region other than the light transmitting holes in the light reflecting layer, and is returned toward the solar cell element. That is, since the reflected light is multiple-reflected between the solar cell element and the reflective layer, the amount of light applied to the photoelectric conversion layer increases, so that the power generation efficiency (light use efficiency) of the solar cell is further increased. It also has the effect of being able to do so.
[0210]
Further, the solar cell according to the present invention, as described above, a solar cell element having a photoelectric conversion layer, a light-collecting element having a light-collecting region and a light-concentrating auxiliary layer, and a light-reflecting layer having a light-transmitting hole. The light-condensing auxiliary layer has a function of reducing the angle of incidence of external light with respect to the light-condensing region as compared with a case where the light-condensing auxiliary layer is not provided, and the light reflecting layer is It is characterized by having a function of making the condensed light incident on the solar cell element through the light transmission hole, reflecting the light reflected by the solar cell element, and re-entering the solar cell element.
[0211]
Therefore, the function of the light-condensing auxiliary layer that reduces the angle of incidence of light incident on the light-condensing region makes it possible to narrow the light beam formed by the condensed light. Thereby, as described above, the power generation efficiency can be increased.
[0212]
In addition, the multiple reflection between the photoelectric conversion layer and the light reflection layer has an effect that the power generation efficiency of the solar cell can be further increased.
[0213]
Further, in the solar cell according to the present invention, in addition to the above-described configuration, the light-collecting curved surface is a cylindrical light-collecting curved surface, and the light transmitting hole is a linear slit-shaped light transmitting hole, It is characterized in that the direction of the curved cylindrical axis and the extending direction of the linear slit-shaped light transmitting hole are arranged in parallel.
[0214]
Therefore, the light condensed linearly by the cylindrical condensing curved surface is efficiently condensed to the linear slit-shaped light transmitting hole. As a result, light incident from the linear slit-shaped light transmitting hole is multiple-reflected between the photoelectric conversion layer and the light reflection layer, and the amount of light irradiated on the photoelectric conversion layer further increases, thereby further increasing power generation efficiency. It becomes possible. Further, even when the incident angle of the sunlight changes, the incident sunlight can be efficiently condensed to the light transmitting hole.
[0215]
Further, since the cylindrical light-collecting curved surface can form the light-collecting element with a small number, it is also useful to simplify the structure of the light-collecting element and reduce the cost. This merit also has an effect that the same applies to the formation of the light reflection layer.
[0216]
In addition, in the solar cell according to the present invention, in addition to the above configuration, the light reflecting layer having the linear slit-shaped light transmitting holes is closer to the cylindrical light-collecting curved surface than the focal length of the cylindrical light-collecting curved surface. It is characterized by being provided at a position.
[0217]
Therefore, the condensing position of the light incident on the side of the cylindrical condensing curved surface is more than the condensing focal position of the light incident on the top of the cylindrical condensing curved surface due to the occurrence of coma. It is possible to cope with the phenomenon that the position is close to the curved surface, and light incident on the side of the cylindrical condensed curved surface easily passes through the light transmission hole group.
[0218]
This makes it possible to efficiently condense the light incident on the top of the cylindrical condensing curved surface and the light incident on the side into the linear slit-shaped light transmitting hole with high efficiency. There is an additional effect that high power generation efficiency can be obtained even when the angle changes.
[0219]
Further, the solar cell according to the present invention, in addition to the above configuration, provided that the focal length of the cylindrical condensing curved surface is F, the surface of the cylindrical condensing curved surface and the linear slit light transmitting hole are provided. The distance from the touched position is (11F / 17) or more and (16F / 17) or less.
[0220]
Therefore, by setting the interval in the above range, most of the incident light can pass through the straight slit-shaped light transmitting hole regardless of the variation of the incident angle, and thus high power generation efficiency can be maintained. The effect of being able to play is further exhibited.
[0221]
Further, in the solar cell according to the present invention, in addition to the above configuration, when the width of the cylindrical condensing curved surface is W, the width of the linear slit-shaped light transmitting hole is (W / 8) or more and (2W / 3) It is characterized by the following.
[0222]
Therefore, by setting the width of the linear slit-shaped light transmission hole in the above range, it is possible to optimize the contradictory functions that the light reflection layer should have, such as an increase in light transmittance and an increase in reflectance. More effect.
[0223]
In addition, the solar cell according to the present invention, in addition to the above configuration, between the light reflection layer and the photoelectric conversion layer, provided a transparent substrate that emits fluorescence having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer. It is characterized by being done.
[0224]
Therefore, the transparent substrate increases the amount of light having a wavelength contributing to photoelectric conversion due to its fluorescent characteristics, and thus has an effect of further increasing the power generation efficiency of the solar cell.
[0225]
Further, the solar cell according to the present invention, in the laminated structure between the light reflecting layer and the photoelectric conversion layer, a transparent adhesive layer that emits fluorescence having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer is included. It is characterized by having.
[0226]
Therefore, the amount of light having a wavelength contributing to photoelectric conversion increases in the transparent adhesive layer due to its fluorescent property, so that the power generation efficiency of the solar cell can be further increased.
[0227]
Further, by forming a laminated structure in which a transparent adhesive layer is interposed between the light reflecting layer and the photoelectric conversion layer, the structural and mechanical strength of the solar cell is increased, and the solar cell is damaged in the manufacturing process. Further, it is possible to suppress a decrease in the yield due to the above.
[0228]
In addition, the solar cell according to the present invention, in addition to the above configuration, including the cylindrical axis direction of the cylindrical condensing curved surface, and is installed so that a plane perpendicular to the condensing element faces the east-west direction. It is characterized by having.
[0229]
Therefore, the angle between the plane including the optical axis of the incident light and including the cylindrical axis and the plane on which the light-collecting element is formed can always be constant. Correspondingly, there is no need to relatively move the cylindrical condensing curved surface and the linear slit-shaped light transmitting hole, and the sunlight can be efficiently condensed on the linear slit-shaped light transmitting hole. Play more.
[Brief description of the drawings]
FIG. 1 is a cross-sectional perspective view showing a configuration example of a solar cell of the present invention.
FIG. 2 is a cross-sectional view illustrating a configuration example of a solar cell element used for the solar cell of the present invention.
FIG. 3 is an explanatory diagram for explaining a path of incident light with respect to the solar cell of FIG. 1;
FIG. 4 is a view illustrating a method for installing a solar cell according to the present invention.
FIG. 5 is a cross-sectional perspective view showing a configuration example of a solar cell related to the present invention.
FIG. 6 is a cross-sectional view illustrating a refraction state of incident light of the solar cell of the present invention.
FIGS. 7A to 7C are explanatory diagrams showing the results of calculating the light-collecting state of the solar cell shown in FIG.
8 (a) to 8 (c) are explanatory views showing the results of calculating the light-collecting state of the solar cell shown in FIG.
9 (a) to 9 (c) are explanatory diagrams showing calculation results of a light-collecting state when the distance between the light-condensing curved surface and the light reflecting layer is reduced in the solar cell shown in FIG.
FIG. 10 is a sectional perspective view showing another configuration example of the solar cell of the present invention.
FIG. 11 is a cross-sectional perspective view showing still another configuration example of the solar cell of the present invention.
FIG. 12 is a cross-sectional perspective view showing still another configuration example of the solar cell of the present invention.
FIG. 13 is a cross-sectional view illustrating another configuration example of the solar cell element used for the solar cell of the present invention.
FIG. 14 is a cross-sectional perspective view showing still another configuration example of the solar cell of the present invention.
FIG. 15 is a cross-sectional perspective view showing still another configuration example of the solar cell of the present invention.
FIG. 16 is a cross-sectional perspective view showing still another configuration example of the solar cell of the present invention.
FIG. 17 is a cross-sectional view illustrating a configuration example of a conventional solar cell element.
FIG. 18 is a cross-sectional view illustrating another configuration example of a conventional solar cell element.
FIG. 19 is a cross-sectional view showing yet another configuration example of a conventional solar cell element.
[Explanation of symbols]
1 substrate
2 Photoelectric conversion layer
3 Solar cell element side second transparent body
4. Cylindrical condensing curved surface group (condensing area)
5 Light reflection layer
6 straight slit-shaped light transmission holes (light transmission holes)
7 Incident light
8. Light incident side first transparent body
15 Vertical direction
16 horizontal direction
17, 18, 28 transparent substrate
19 Transparent substrate for solar cell element
20 photoelectric conversion layer
F focal length
Q Incident angle

Claims (9)

A solar cell element having a photoelectric conversion layer,
A light-collecting element in which a light-collecting region is provided between a first transparent body on the light incident side having a refractive index larger than air and a second transparent body on the solar cell element side having a larger refractive index than the first transparent body; ,
A light reflection layer having a light transmission hole,
The light reflecting layer receives the light condensed by the light condensing region, passes through the light transmitting hole, and then enters the solar cell element. A solar cell characterized by being formed between a solar cell element and a condensing element so as to be incident. A solar cell element having a photoelectric conversion layer,
A light-collecting element having a light-collecting region and a light-concentrating auxiliary layer,
A light reflection layer having a light transmission hole,
The light-condensing auxiliary layer has a function of reducing an incident angle of the external light with respect to the light-condensing region as compared with a case where the light-condensing auxiliary layer is not provided,
The light reflection layer causes the light condensed by the light condensing region to enter the solar cell element through the light transmission hole, reflects the light reflected by the solar cell element, and re-enters the solar cell element. A solar cell having a function of causing the solar cell to have a function of causing the solar cell to function. The light-collecting region is a cylindrical light-collecting curved surface,
The light transmission hole is a straight slit-shaped light transmission hole,
The solar cell according to claim 1, wherein a direction of a cylindrical axis of the cylindrical converging curved surface and an extending direction of the linear slit-shaped light transmitting hole are arranged in parallel. The light reflection layer having the linear slit-shaped light transmission hole is provided at a position closer to the cylindrical light-collecting curved surface than the focal length of the cylindrical light-collecting curved surface. Solar cells. Assuming that the focal length of the cylindrical condensing curved surface is F, the distance between the light incident side surface of the cylindrical condensing curved surface and the position where the linear slit-shaped light transmitting hole is provided is (11F / 17) or more, The solar cell according to claim 3, wherein the ratio is (16F / 17) or less. The width of the linear slit-shaped light transmitting hole is not less than (W / 8) and not more than (2W / 3), where W is the width of the cylindrical condensing curved surface. Solar cells. The solar cell according to claim 1, wherein a transparent substrate that emits fluorescence having a wavelength that contributes to photoelectric conversion of the photoelectric conversion layer is provided between the light reflection layer and the photoelectric conversion layer. battery. 2. A transparent adhesive layer emitting fluorescence having a wavelength contributing to photoelectric conversion of the photoelectric conversion layer is included in a laminated structure between the light reflection layer and the photoelectric conversion layer. Or the solar cell according to 2. The solar cell according to claim 3, wherein a plane including the cylindrical axial direction of the cylindrical converging curved surface and perpendicular to the condensing element is installed so as to face the east-west direction.

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