JP2004128419A - Solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell that realizes high-reliability and high generation efficiency by improving environment resistance and increasing the utilization efficiency of external light irradiating a photoelectric conversion layer. <P>SOLUTION: The light incidence surface of a condensing element 3 where the external light enters is set to a flat surface part 5. Thereby the light incidence surface of the condensing element 3 becomes resistant to dust, and therefore the time degradation of the generation efficiency is prevented. Light condensed by a group of cylindrical light condensing curved surfaces 4 enters from a group of linear slit-like light-transmitting holes 6 and multiply reflected between the photoelectric conversion layer 2 and light-reflection layer 7 of a solar cell element. Thereby the quantity of light to be applied to the photoelectric conversion layer 2 is increased and the generation efficiency is enhanced. <P>COPYRIGHT: (C)2004,JPO

Description

【０１１７】
表１は、直線スリット状光透過孔群８の光軸上の位置、すなわち、集光素子３のシリンドリカル状集光曲面群４と光反射層７との間隔ｄを変えた場合において、入射光９の入射角Ｑ１に対して、発電効率がどのように変化するかを調べた結果を示している。
【０１１８】
光源としては、太陽光シミュレーターを用い、１００ｍＷ／ｃｍ^２の強度の光を斜め上から照射した。また、表１は、並べて配置した比較例１の太陽電池の開放電圧Ｖ及び短絡電流Ｉを１００％として、本発明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１と比較した結果を示している。
【０１１９】
焦点距離Ｆが３５ｍｍであるのに対して、ｄ＝３５ｍｍ（Ｆ）とした場合、入射角度Ｑ１＝０°、４０°においては、開放電圧Ｖ及び短絡電流Ｉがともに比較例１より大きくなっており、入射角度Ｑ１＝６０°において、短絡電流Ｉが比較例１よりも小さくなっていることがわかる。
【０１２０】
入射角度Ｑ１＝６０°において、短絡電流Ｉが比較例１よりも小さくなっている理由は、図５（ｃ）を参照して上述したように、シリンドリカル状集光曲面の両端部付近で集光された光が、直線スリット状光透過孔を通過できないからである。
【０１２１】
しかしながら、この場合においても、発電量が大きくなる入射角度の小さい時間帯において、比較例１より大きな発電効率が実現しており、一日のトータル発電量を考慮すると、ｄ＝Ｆとした実施例１において、比較例１より多くの発電量が得られることになる。
【０１２２】
また、表１を見ると、ｄが１５ｍｍ（３Ｆ／７）以上、３０ｍｍ（６Ｆ／７）以下の範囲において、入射角度Ｑ＝６０°までのすべての入射角度において、比較例１よりも本発明の太陽電池の開放電圧Ｖと短絡電流Ｉの両方が大きくなっていることが分かる。したがって、実施例１の太陽電池においては、集光素子３のシリンドリカル状集光曲面群４と光反射層７との間隔ｄを（３Ｆ／７）以上、（６Ｆ／７）以下とすることが望ましい。
【０１２３】
上記間隔ｄが（３Ｆ／７）より小さくなると、入射角が小さい範囲では、直線スリット状光透過孔の位置が、集光位置よりシリンドリカル状集光曲面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を照射することになる。このため、入射角が小さい範囲において、すなわち発電量が本来大きくなる時間帯で、直線スリット状光透過孔を通過できない光が増加し、発電効率が低下する。
【０１２４】
一方、上記間隔が（６Ｆ／７）より大きくなると、入射角が大きい範囲では、集光位置が、直線スリット状光透過孔とシリンドリカル状集光曲面との間に位置し、集光位置と直線スリット状光透過孔の位置とが離れ過ぎるため、集光された後の広がった状態の光束が、直線スリット状光透過孔を照射することになる。このため、入射角が大きい範囲において、直線スリット状光透過孔を通過できない光が増加し、発電効率が低下する。
【０１２５】
そこで、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。
【０１２６】
次に、間隔ｄを最適条件、すなわち、ｄ＝２５ｍｍ（５Ｆ／７）に固定して、直線スリット状光透過孔群８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。
【０１２７】
【表２】

【０１２８】
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１０ｍｍであるのに対して、スリット１つあたりの幅Ｗを２ｍｍ（Ｗ／５）以上とし、６ｍｍ（３Ｗ／５）以下とすることにより、６０°までのすべての入射角に対して、比較例１よりも大きな開放電圧Ｖと短絡電流Ｉが得られた。
【０１２９】
スリット幅ＷＳが狭くなりすぎると、集光された光の一部が光反射層７により反射され、太陽電池素子の光電変換層２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が広くなりすぎると、直線スリット状光透過孔群８から入射し、光電変換層２と光反射層７との間で多重反射すべき光が、再度、直線スリット状光透過孔群８から放射される。この結果、光の利用効率が低下するため、発電効率の低下につながる。
【０１３０】
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８が形成された光反射層７までの間隔ｄを（３Ｆ／７）以上、（６Ｆ／７）以下とすることが望ましい。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８のスリット幅ＷＳを（Ｗ／５）以上、（３Ｗ／５）以下とすることが望ましい。
次に、図１に示す実施例１の構成の太陽電池と、図１３に示す比較例２の構成の太陽電池とを屋外に配置し、その発電効率の変化を比較した結果を表３に示す。
【０１３１】
【表３】

【０１３２】
測定に際して、光源として、太陽光シミュレーターを用い、１００ｍＷ／ｃｍ^２の強度の光を集光素子３の平面部５に対して垂直に照射した。そして、実施例１及び比較例２の初期状態における開放電圧Ｖと短絡電流Ｉとを１００％として、一定期間屋外に配置した後、再度同一条件での測定を行い、開放電圧Ｖと短絡電流Ｉとを初期状態と比較した。
【０１３３】
その結果、表３に示すように、実施例１の太陽電池においては、屋外に１０日間放置することにより、僅かに開放電圧Ｖと短絡電流Ｉとが減少するが、その後、放置日数が増加しても、開放電圧Ｖと短絡電流Ｉとは、ほとんど変化しておらず、安定した発電効率が確保されていることが分かる。
【０１３４】
これに対して、比較例２の太陽電池では、開放電圧Ｖと短絡電流Ｉとがともに、放置日数の増加に伴い徐々に減少し、発電効率が低下していることがわかる。
【０１３５】
この発電効率の違いは、既に説明したように、集光素子３に対する塵埃の付着量の違いに起因している。すなわち、比較例２の太陽電池においては、放置日数の増加にともない、光入射面としてのシリンドリカル状集光曲面群４の凹部に沿って、塵埃付着の増加が確認され、この塵埃付着が発電効率低下の原因となっている。一方、実施例１の太陽電池においては、光入射面が平面部５となっており、凹凸が無いため、このような塵埃付着の増加は確認されず、安定した発電効率が得られている。
【０１３６】
なお、本実施例においては、集光素子３（図１）と透明基板６と太陽電池素子との間にスペーサを設け、各々を固定配置した構成について説明しているが、紫外線硬化樹脂等の透明接着剤を用いて、集光素子３と透明基板６と太陽電池素子とを互いに接着固定してもよい。これにより、より強固に集光素子３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。
【０１３７】
しかしながら、集光曲面群の焦点距離を短くし、太陽電池の厚さを薄くするためには、集光素子３と直線スリット状光透過孔群８との間の媒質の屈折率ｎ２は可能な限り小さいことが望ましい。したがって、透明基板６と太陽電池素子とを透明接着剤により接着固定する一方、集光素子３と透明基板６との間には、屈折率１の空気が介在するように、スペーサを用いて集光素子３と透明基板６とを固定することが望ましい。
【０１３８】
次に、実施例１の太陽電池において、透明基板６として、蛍光特性を有する透明基板（透明材層）を用いた実施例について説明する。
【０１３９】
実施例１においては、透明基板６として、板厚２ｍｍのポリカーボネート樹脂製の透明基板を用いたが、ここではその代わりとして、粒径５μｍのＹ_２Ｏ_２Ｓ：Ｅｕ，Ｍｇ，Ｔｉの蛍光粒子を、１５体積％含有させた板厚２ｍｍのポリカーボネート樹脂製の透明基板を用いた。
【０１４０】
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。このため、蛍光粒子から発生する波長６００ｎｍ近傍の光もまた、光反射層７と太陽電池素子との間で多重反射することにより、太陽電池の発電効率を高くすることが可能となる。
【０１４１】
蛍光粒子を含有しない透明基板６を用いた太陽電池と、蛍光粒子を含有した透明基板６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、入射角度Ｑ０が０°、４０°、６０°となるように入射させ、両者の開放電圧Ｖと短絡電流Ｉを比較した。その結果、蛍光粒子を含有した透明基板６を用いることにより、全ての入射角度Ｑ０において、開放電圧Ｖが５％程度大きくなり、短絡電流Ｉが２５％程度大きくなることが確認された。
【０１４２】
また、実施例１の太陽電池において、蛍光性微粒子が分散した紫外線硬化樹脂（透明材層）を用いて、透明基板６と太陽電池素子とを接着固定した場合も、同様に、発電効率を高くすることが可能となる。
【０１４３】
ここでは、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、透明基板６と太陽電池素子とを、５０μｍ厚の該紫外線硬化樹脂を用いて接着固定した。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、該紫外線硬化樹脂の層が、光反射層７と光電変換層２との間に配置されているため、蛍光粒子から発生する波長６００ｎｍ近傍の光が、光反射層７と太陽電池素子との間で多重反射する。これにより、太陽電池の発電効率を高くすることが可能となる。
【０１４４】
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６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６と太陽電池素子とを接着固定した本発明の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、入射角度Ｑ０が０°、４０°、６０°となるように入射させ、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、開放電圧Ｖが３％程度大きくなり、短絡電流Ｉが１７％程度大きくなることが確認された。
【０１４５】
なお、蛍光粒子を含有させた透明基板６および紫外線硬化樹脂を組み合わせて用いることにより、多重反射の光路に蛍光粒子が多く存在することになるため、発電効率を一層向上させることができる。
【０１４６】
上記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。
【０１４７】
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。
【０１４８】
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。
【０１４９】
［実施例２］
実施例１においては、太陽の日周運動を考慮して、上記太陽電池の縦方向１６（図３）が東西方向と一致するように配置した場合について説明した。しかし、実際には地軸が傾いているため、季節によっては、太陽光７が横方向１７の斜め上から入射することになる。
【０１５０】
例えば、春分の日の南中時に、太陽光としての入射光９が垂直真上から入射し、直線スリット状光透過孔群８に集光されるように、上記太陽電池を設置すると、地軸が２３．４°傾いているため、冬至や夏至には、入射光９は、横方向１７の斜め上から±２３．４°の入射角Ｑ_１で入射する。この結果、入射光９の光軸が直線スリット状光透過孔群８から横方向１７に変位するため、入射光９は光反射層７により反射され、発電効率が著しく低下することになる。
【０１５１】
実施例２の太陽電池は、上記問題点を解決するために、図７に示すように構成されている。すなわち、シリンドリカル状集光曲面群４が設けられた集光素子３と、直線スリット状光透過孔群８が設けられた透明基板６とが、入射光９の入射角度Ｑ_１に対応して、横方向１７に相対的に移動可能に支持されている。
【０１５２】
このように、季節に伴う太陽光の入射角度の変化に対応して、集光素子３と透明基板６とを相対的に移動させ、太陽光の集光位置と直線スリット状光透過孔群８の位置とを一致させる、あるいは集光された太陽光が形成する光束が、できるだけ直線スリット状光透過孔群８を通過できるようにすることで、上記光電変換層２に入射する太陽光を増大させることができ、もって発電効率を高めることが可能となる。
【０１５３】
また、図８に示すように、透明基板６と光電変換層２を有する太陽電池素子とが透明接着剤等により接着固定されている場合にも、透明基板６と太陽電池素子とを一体的に、移動可能とすることにより、同様に、高い発電効率を実現することが可能となる。
【０１５４】
なお、太陽光の入射角度が年内変化する影響を解消する別の手立てとして、集光素子３の平面部５が、常に太陽光を垂直に受光するように、太陽電池を東西方向に平行な回転軸の周りに回転させてもよい。この場合の回転角度は、１日当たりに換算して、高々０．２５°程度でよい。
【０１５５】
［実施例３］
本発明の実施例３として、図９に示す構成の太陽電池を作製した。
【０１５６】
実施例３の太陽電池は、実施例１に記載の集光素子３と、太陽電池素子用透明基板１８及び光電変換層１９を有する太陽電池素子とで構成されている。ここで、直線スリット状光透過孔群８を有する光反射層７は、太陽電池素子用透明基板１８の光入射面、すなわち光電変換層１９に対向する面に設けられている。
【０１５７】
この太陽電池においては、集光素子３の平面部５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８に集光され、太陽電池素子用透明基板１８を透過し、光電変換層１９へと入射する。
【０１５８】
一方、光電変換層１９からの反射光は、光反射層７により反射され、光電変換層１９に再入射することにより、光電変換層１９と光反射層７との間で入射光９が多重反射する。これにより、高い発電効率が実現される。
【０１５９】
実施例３の太陽電池素子は、図１０に示すような構成であり、次のようにして作製した。
【０１６０】
まず、太陽電池素子用透明基板１８に、膜厚３０ｎｍのＳｎＯ_２透明導電層２０を反応性スパッタリングにより形成した後、遮蔽マスクを透明導電層２０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のくし型の集電電極２１を形成した。
【０１６１】
次に、ｐ型不純物ドープ半導体層であるｐ層２２、真性半導体であるｉ層２３、ｎ型不純物ドープ層であるｎ層２４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２２〜２３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２２、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２３、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２４とした。
【０１６２】
上記光電変換層１９を形成した後、膜厚１００ｎｍのＡｌからなる光反射効果を有する電極金属層２５をスパッタリングにより形成し、紫外線硬化樹脂を電極金属層２５上に塗布し、電極金属層２５の保護膜２６とした。
【０１６３】
実施例３の集光素子３を有する太陽電池と、集光素子３を取り外した上記太陽電池素子（比較例３）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３における集光素子３のシリンドリカル状集光曲面群４と、太陽電池素子用透明基板１８上の光反射層７との間隔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。
【０１６４】
【表４】

【０１６５】
表４は、実施例３と比較例３の太陽電池に対して、太陽光シミュレーターを用いて１００ｍＷ／ｃｍ^２の強度の光を、入射角度Ｑ１が０°、４０°、６０°となるように入射させ、比較例３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３の太陽電池の開放電圧Ｖと短絡電流Ｉとを示している。
【０１６６】
実施例３の集光素子３は、実施例１と同じものであり、実施例３の太陽電池においても実施例１と同様な結果が得られた。
【０１６７】
すなわち、実施例３の太陽電池においても、実施例１と同様に、シリンドリカル状集光曲面群４の焦点距離をＦ（３５ｍｍ）として、シリンドリカル状集光曲面群４の表面と光反射層７との間隔ｄを（３Ｆ／７）以上、（６Ｆ／７）以下とすることが望ましい。
【０１６８】
また、図１１に示すように、実施例１と同様に、集光素子３と、太陽電池素子用透明基板１８及び光電変換層１９を有する太陽電池素子との間に、光透過孔群８を有する光反射層７を設けた透明基板６を設けた場合においても、上記実施例３と同様に、高い発電効率を実現することが可能である。
【０１６９】
また、図９及び図１１に示す実施例３の太陽電池において、集光素子３と直線スリット状光透過孔群８とを相対的に横方向１７に移動可能に配置してもよい。これにより、太陽光の入射角度が季節変化するのに対して、発電効率を高く維持できる点は実施例２で説明したとおりである。
【０１７０】
また、実施例１と同様に、直線スリット状光透過孔群８を有する光反射層７よりも光電変換層側に配置される透明基板もしくは透明接着剤として、蛍光特性を有する透明基板もしくは透明接着剤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可能となる。
【０１７１】
［実施例４］
本発明の実施例４として、図１２に示す構成の太陽電池を作製した。
【０１７２】
実施例４の太陽電池は、実施例１の太陽電池の集光素子３の光入射面側、すなわち、平面部５上に、低屈折率反射防止膜２７（反射防止機能を有する透明材層）が形成された構成となっている。
【０１７３】
集光素子３としては、良好な集光特性を得るため、屈折率１．５程度以上の透明材料を用いることが望ましいが、この場合、光入射面においては、少なくとも４％程度以上の表面反射が発生することになる。太陽光の入射角度が大きくなると、この表面反射の割合は、さらに大きくなる。
【０１７４】
そこで、本実施例４においては、低屈折率反射防止膜２７のように、集光素子３より屈折率の小さい膜を集光素子３の光入射面に設けることにより、この表面反射を２％程度以下に抑えることが可能となり、表面反射による発電効率の低下を抑制することができる。
【０１７５】
具体的な作製方法を説明する。実施例４の太陽電池では、実施例１で作製した太陽電池に対して、さらに、集光素子３の平面部５上に、フルオロビニルエーテルを使用した紫外線硬化型の透明フッ素樹脂をコーティングし、紫外線を照射することにより、上記透明フッ素樹脂を硬化させた。これにより、屈折率１．３５の低屈折率反射防止膜２７を備えた太陽電池を作製した。実施例１の太陽電池においては、４％の表面反射が存在したが、実施例４の太陽電池においては、１．４％の表面反射に抑えることができた。
【０１７６】
次に、太陽光シミュレーターを用いて１００ｍＷ／ｃｍ^２の強度の光を、入射角度Ｑ１が０°となるように入射させ、実施例４と実施例１の開放電圧Ｖと短絡電流Ｉを比較した。その結果、実施例４の太陽電池の方が、開放電圧Ｖが１％程度大きくなり、短絡電流Ｉが３％程度大きくなることが確認された。
【０１７７】
ここでは、実施例１の太陽電池に対して、低屈折率反射防止膜２７を適用した実施例について記載しているが、実施例２及び実施例３に記載の太陽電池に対しても、同様な効果を得ることが可能である。
【０１７８】
なお、特許請求の範囲には記載していないが、本発明は、さらに太陽電池における以下の構成を、その技術的範囲に含む。
【０１７９】
例えば、本発明に係る太陽電池は、図１、図３、図１１、及び図１２に示すように、上記光透過孔群を有する上記光反射層が、上記集光素子と上記太陽電池素子との間に設けられた第１透明基板上に形成されていることを特徴としている。
【０１８０】
上記の構成により、上記集光素子と上記第１透明基板と上記太陽電池素子とを、それぞれ、独立して形成することが可能であり、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。
【０１８１】
なお、上記太陽電池素子の光電変換層は、図１、図３、図７、図８、及び図１２に示すように、太陽電池素子用透明基板上に設けることができる。
【０１８２】
また、本発明に係る太陽電池は、上記の構成に加えて、上記第１透明基板と上記太陽電池素子とが、透明接着剤により固定されていることを特徴としている。
【０１８３】
上記の構成により、上記第１透明基板と上記太陽電池素子とが、あらかじめ、接着固定されていることにより、上記第１透明基板および上記太陽電池素子の機械的強度が高められ、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が可能であるとともに、太陽電池の薄型化を実現することができる。
【０１８４】
また、本発明に係る太陽電池は、図９に示すように、上記光電変換層が太陽電池素子用透明基板の一方の面に設けられており、上記太陽電池素子用透明基板の上記光電変換層に対向する面に、上記光透過孔群を有する上記光反射層が設けられていることを特徴としている。
【０１８５】
上記の構成により、上記太陽電池素子用透明基板上に、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。
【０１８６】
また、本発明に係る太陽電池は、図１、図３、図７、図８、図１１及び図１２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第１透明基板が設けられており、該第１透明基板に、上記光透過孔群を有する上記光反射層が設けられており、上記光電変換層が太陽電池素子用透明基板上に設けられていることを特徴としている。
【０１８７】
上記の構成により、上記集光素子と上記第１透明基板と上記太陽電池素子とを、それぞれ、独立して形成することが可能であり、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。
【０１８８】
また、本発明に係る太陽電池は、上記の構成に加えて、図７及び図８に示すように、上記集光素子と光反射とが、相対的に移動可能に支持されていることを特徴としている。
【０１８９】
上記の構成によれば、上記集光素子と上記光反射層とを、相対的に移動させることによって、該集光素子により集光される光が、該光反射層に設けられた光透過孔を通過するときの通過光量を調節できるので、季節変化や時間変化に伴い太陽光等の光の入射角が変化した場合においても、集光素子により集光された光の位置を、光透過孔の位置に対して調節することが可能となる。
【０１９０】
従って、光の入射角が変化した場合においても、光を効率良く光透過孔を通過させることが可能となり、季節変化や時間変化に係り無く、太陽電池の発電効率を高くすることができる。
【０１９１】
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。
【０１９２】
【発明の効果】
本発明に係る太陽電池は、以上のように、外部光が入射する平坦な光入射面を備えると共に、光出射側に、外部光を集光するための集光構造を備えた集光素子と、光透過孔を有する光反射層とを備え、該光反射層は、上記集光構造により集光された光が上記光透過孔を通過した後、上記太陽電池素子に入射し、該太陽電池素子からの反射光が該光反射層により反射され、該太陽電池素子に再入射するように、該太陽電池素子と該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。
【０１９３】
それゆえ、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）を高くすることができる。
【０１９４】
また、集光素子の光入射面における屈折作用により、集光構造へ入射する光の入射角が小さくなり、集光光束が細く絞られるため、光透過孔に導くことが容易となる。この結果、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可能となるので、発電効率を一層高めることができる。
【０１９５】
さらに、外部光が入射する光入射面は、平坦なので塵埃等が付着し易い凹凸を持っていない。このため、塵埃等の付着によって該集光素子の集光効率が、経時的に劣化することを最小限に抑えることができる。すなわち、耐環境性に優れ、高発電効率を長期間維持できる、信頼性の高い太陽電池を提供することができる。このように、本発明に係る太陽電池は、上記種々の効果を併せて奏する。
【０１９６】
また、本発明に係る太陽電池は、以上のように、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、該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材層が設けられていることを特徴としている。
【０１９７】
それゆえ、光電変換に寄与する波長の光の光量が増大するので、太陽電池の発電効率を一層高くすることが可能となるというさらなる効果を奏する。
【０１９８】
また、本発明に係る太陽電池は、以上のように、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の積層構造中に、該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。
【０１９９】
それゆえ、既に説明した該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の働きと同様に、太陽電池の発電効率を一層高めることができる。
【０２００】
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さらなる効果を併せて奏する。
【０２０１】
また、本発明に係る太陽電池は、以上のように、上記の構成に加えて、上記集光素子の光入射面上に、上記集光素子を構成する材料の屈折率よりも小さな屈折率を有する透明材層が設けられていることを特徴としている。
【０２０２】
それゆえ、光入射面での反射を抑える分、該集光素子内部により多くの光を入射させることができる。その上、既に説明したように、集光素子自体が、集光構造に入射する光の入射角を小さくする働きを持っている上に、上記透明材層が光の入射角を小さくする働きも加わる。これにより、該光束を光透過孔に導くことが一層容易となり、光反射層と太陽電池素子との間に導入される光量をさらに増加させることができる。この結果、発電効率をさらに高めることができるというさらなる効果を奏する。
【０２０３】
また、本発明に係る太陽電池は、以上のように、上記の構成に加えて、上記集光構造が、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り、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。
【０２０４】
それゆえ、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ので、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できる。
【０２０５】
また、シリンドリカル状集光曲面は、集光構造を備えた集光素子を簡易に形成するのに有利なため、集光素子の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ので、太陽電池の製造コスト増大を回避できるというさらなる効果を併せて奏する。
【０２０６】
また、本発明に係る太陽電池は、以上のように、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。
【０２０７】
それゆえ、シリンドリカル状集光曲面の円筒軸に対して斜めに入射する光の集光位置に合わせて、光反射層をシリンドリカル状集光曲面側に近づけて配置するので、集光された後の広がった光束が直線スリット状光透過孔を照射する状態を減らすことができる。すなわち、斜めに入射する光の透過光量を増大させることができるので、発電効率を向上させることができるというさらなる効果を奏する。
【０２０８】
また、本発明に係る太陽電池は、以上のように、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とすると、シリンドリカル状集光曲面の光出射側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、（３Ｆ／７）以上、（６Ｆ／７）以下であることを特徴としている。
【０２０９】
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さらなる効果を奏する。
【０２１０】
また、本発明に係る太陽電池は、以上のように、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／５）以上、（３Ｗ／５）以下であることを特徴としている。
【０２１１】
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さらなる効果を奏する。
【０２１２】
また、本発明に係る太陽電池は、以上のように、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。
【０２１３】
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さらなる効果を奏する。
【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模式的な断面図である。
【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】（ａ）〜（ｃ）は、本発明の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６】（ａ）〜（ｃ）は、本発明の太陽電池において、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である。
【図７】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８】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９】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１０】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模式的な断面図である。
【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１４】従来の太陽電池素子の構成例を示す模式的な断面図である。
【図１５】従来の太陽電池素子の他の構成例を示す模式的な断面図である。
【図１６】従来の太陽電池素子のさらに他の構成例を示す模式的な断面図である。
【符号の説明】
１　基板
２　光電変換層
３　集光素子
４　シリンドリカル状集光曲面群（集光構造）
５　平面部（光入射面）
６　透明基板（透明材層）
７　光反射層
８　直線スリット状光透過孔群（光透過孔）
９　入射光（外部光）
１６　縦方向
１７　横方向
１８　太陽電池素子用透明基板
１９　光電変換層
２７　低屈折率反射防止膜（反射防止機能を有する透明材層）
Ｆ　焦点距離
Ｑ、Ｑ_１、Ｑ_２　入射角度
ｄ　間隔[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solar cell.
[0002]
[Prior art]
Conventional thin-film solar cells include a polycrystalline Si solar cell that performs photoelectric conversion by a pn junction as shown in FIG. 14 and a photoelectric conversion by a pin junction as shown in FIG. It is an amorphous 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. 14, an electrode metal layer 142 having a light reflecting effect and a good electrical contact between the electrode metal layer 142 and the polycrystalline Si semiconductor layer 144 are formed on a substrate 141 also serving as a support. A polycrystalline Si semiconductor layer 143 doped with one of an n-type impurity or a p-type impurity at a high concentration, and a polycrystalline Si semiconductor lightly doped with an impurity of the same conductivity type as the polycrystalline Si semiconductor layer 143. The layer 144, the polycrystalline Si semiconductor layer 145 doped with impurities of a conductivity type opposite to that of the polycrystalline Si semiconductor layers 143 and 144 at a high concentration, a current collecting electrode 146 for extracting current, and a reflection for efficiently capturing light. And a prevention layer 147.
[0004]
Further, in the amorphous Si solar cell shown in FIG. 15, an electrode metal layer 152 having a light reflection effect, an n-type impurity doped with an amorphous Si semiconductor on a substrate 151 also serving as a support. A layer 153, an i-layer 154 made of an amorphous Si semiconductor and serving as an intrinsic semiconductor, a p-layer 155 made of an amorphous Si semiconductor and doped with a p-type impurity, a current collecting electrode 156 for extracting current, and light efficiently. And an antireflection layer 157 for taking in the light.
[0005]
Further, in order to increase power generation efficiency, a tandem solar cell has been proposed in which a pn junction shown in FIG. 14 and a pin junction shown in FIG. 15 are stacked.
[0006]
In addition to these solar cells, a solar cell as shown in FIG. 16 in which light is incident from the substrate side has been proposed. In this solar cell, an anti-reflection layer 162 for efficiently taking in light, a current collecting electrode 163 for taking out current, and an amorphous Si semiconductor are formed on a transparent substrate 161 for solar cell elements in order from the light incident side. A p-layer 164 doped with a p-type impurity, an i-layer 165 made of an amorphous Si semiconductor and being an intrinsic semiconductor, an n-layer 166 made of an amorphous Si semiconductor and doped with an n-type impurity, having a light reflection effect. And an electrode metal layer 167.
[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 conventional configurations shown in FIGS. 14 to 16 have a problem that power generation efficiency is low due to various factors described below.
[0010]
The first factor lies in the antireflection layers 147, 157, and 162. That is, in the conventional solar cell, the antireflection layers 147, 157, and 162 made of a conductive transparent film are provided in the light incident surface or in the vicinity of the light incident surface for the purpose of minimizing surface reflection. It is difficult to completely reduce the surface reflection to zero, which causes a problem that a part of incident light is reflected. In addition, the antireflection layers 147, 157, and 162 generally have wavelength dependence, and there is a problem in that the surface wavelength increases when the light wavelength deviates from the design wavelength center. 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 lies in the current collecting electrodes 146, 156, 163. That is, the current collecting electrodes 146, 156, and 163 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]
Incidentally, the polycrystalline Si semiconductor layer 144 and the amorphous Si semiconductor i layers 154 and 155, which generate light by absorbing light to generate electric power, need to have a sufficient thickness to absorb incident light. In order to increase power generation 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 also translates into an issue of how to make it possible to reduce the thickness of the semiconductor layer by reducing the external output current by using external light such as sunlight without waste. it can.
[0014]
Further, in order to cope with an application in which solar cells are expected to grow rapidly in the future, such as installing a solar cell outdoors, a structure that takes environmental resistance into consideration is required.
[0015]
Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to improve the environmental resistance of a solar cell, and to increase the use efficiency of external light for irradiating a photoelectric conversion layer. Another object of the present invention is to provide a solar cell that achieves higher reliability and higher power generation efficiency than conventional solar cells.
[0016]
[Means for Solving the Problems]
In order to solve the above-described problems, a solar cell according to the present invention includes a flat light incident surface on which external light is incident, and a light-collecting structure including a light-collecting structure for condensing external light on a light output side. An optical element, comprising a light reflection layer having a light transmission hole, the light reflection layer, after the light collected by the light collection structure passes through the light transmission hole, is incident on the solar cell element, The light-reflecting layer is formed between the solar cell element and the light-collecting element such that light reflected from the solar cell element is reflected by the light reflection layer and re-enters the solar cell element. .
[0017]
According to the above configuration, the following operation and effect can be obtained.
[0018]
First, the light that has entered the light-collecting element is collected by the light-collecting structure, passes through the light transmitting hole, and irradiates the solar cell element. In this case, a plurality of light transmission holes may be provided corresponding to the light-collecting structure. As the light collecting structure, an array of cylindrical light collecting curved surfaces, a Fresnel light collecting element, or the like is suitable.
[0019]
Subsequently, part of the light irradiated to the solar cell element is absorbed by the photoelectric conversion layer, but 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]
Second, external light such as sunlight is refracted on the light incident surface of the light-collecting element having a higher refractive index than air. The angle of refraction at this time is smaller than the angle of incidence according to the law of refraction. Therefore, when the light transmitted through the light-collecting element enters the light-collecting structure, the angle of incidence is smaller than when the external light directly enters the light-collecting structure. In general, the smaller the incident angle of the parallel light beam incident on the light-collecting structure having the light-collecting function, the smaller the movement of the light-collecting position of the light collected by the light-collecting structure. Then, as the movement of the light condensing position becomes smaller, the light condensing degree of the light transmitted through the light transmitting hole becomes higher. This makes it easy to guide the light flux to the light transmission holes without irradiating the light reflection layer, so that it is possible to increase the amount of light introduced between the light reflection layer and the solar cell element. The power generation efficiency can be further increased.
[0021]
Third, since the light-collecting element has a light incident surface on which external light is incident, the light incident surface is disposed in contact with or close to the outside. Such a light incident surface is easily exposed to dust and the like. However, since the light incident surface is flat, the light incident surface does not have irregularities to which dust and the like easily adhere. For this reason, it is possible to minimize the deterioration of the light-collecting efficiency of the light-collecting element over time due to the attachment of dust or the like. That is, a highly reliable solar cell which is excellent in environmental resistance and can maintain high power generation efficiency for a long time can be provided.
[0022]
In addition, in order to solve the above problems, the solar cell according to the present invention contributes to photoelectric conversion of the photoelectric conversion layer between the light reflection layer and the photoelectric conversion layer in addition to the above configuration. It is characterized in that a transparent material layer that emits fluorescence of a wavelength is provided.
[0023]
With the above configuration, the light condensed by the light condensing element passes through the light transmission hole and enters the transparent material layer. The transparent material layer 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 the light as fluorescence, due to its fluorescence characteristics. . The generated fluorescence is irradiated directly or after being once reflected by the reflection layer onto the photoelectric conversion layer.
[0024]
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.
[0025]
The transparent material layer is provided as a separate transparent substrate between the light-collecting element and the solar cell element, and the light-reflecting layer is laminated on a surface of the transparent substrate on the light-collecting element side. May be. Further, a configuration may be adopted in which a photoelectric conversion layer is formed on one surface of the transparent substrate, a light reflection layer is formed on the other surface, and the light reflection layer is arranged on the light-collecting element side. Further, the number of transparent substrates provided is not limited to one.
[0026]
Further, the transparent material layer may be a transparent adhesive layer described later.
[0027]
In any case, the above-described effect can be obtained by providing one or more transparent material layers that emit fluorescence having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer between the light reflection layer and the photoelectric conversion layer. Obtainable.
[0028]
In addition, in order to solve the above-mentioned problem, the solar cell according to the present invention may further include, in addition to the above configuration, a photoelectric conversion layer having a photoelectric conversion layer in a stacked structure between the light reflection layer and the photoelectric conversion layer. It is characterized in that it includes a transparent adhesive layer that emits fluorescence of a wavelength that contributes to conversion.
[0029]
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 transparent substrate having a light reflection layer formed on the surface on the light-collecting element side may be bonded and fixed to a solar cell element via a transparent adhesive layer. Alternatively, another transparent substrate having a light reflection layer formed on the surface on the light-collecting element side may be replaced with a transparent adhesive layer on a transparent substrate for a solar cell element having a photoelectric conversion layer formed on a surface far from the light-collecting element. It may be adhered and fixed via a.
[0030]
As described above, in the laminated structure that can take various aspects, by the interposition of the transparent adhesive layer that emits fluorescence having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer, light collected by the light collection element is Then, the light passes through the light transmission hole of the light reflection layer and enters the transparent adhesive layer 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 material layer that emits fluorescence having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer described above.
[0031]
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.
[0032]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0033]
Further, in order to solve the above-mentioned problems, the solar cell according to the present invention, in addition to the above configuration, on the light incident surface of the light-collecting element, has a refractive index higher than the refractive index of the material forming the light-collecting element. It is characterized in that a transparent material layer having a small refractive index is provided.
[0034]
According to the above configuration, the following operation and effect can be obtained.
[0035]
First, since the refractive index of the transparent material layer is smaller than the refractive index of the material forming the light-collecting element, the reflectance on the light incident surface can be reduced. In other words, more light can be made to enter the inside of the light-collecting element because the reflection on the light incident surface is suppressed.
[0036]
Second, since the refractive index of the transparent material layer is higher than that of air, light incident on the transparent material layer is refracted at a smaller refraction angle than the incident angle according to the law of refraction. Therefore, as described above, the light-collecting element itself has a function of reducing the incident angle of light incident on the light-collecting structure, and the transparent material layer also has a function of reducing the incident angle of light. Therefore, the effect of narrowing the light beam formed by the light collected by the light collecting structure can be synergistically enhanced.
[0037]
This makes it easier to guide the light flux to each light transmitting hole without irradiating the light reflecting layer to the light reflecting layer, so that the amount of light introduced between the light reflecting layer and the solar cell element can be further increased. As a result, the power generation efficiency can be further increased.
[0038]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0039]
Further, in order to solve the above problem, in the solar cell according to the present invention, in addition to the above-described configuration, the light-collecting structure is a cylindrical light-collecting curved surface, and the light transmission hole has a linear slit-like light transmission. And wherein the direction of the cylindrical axis of the cylindrical converging curved surface and the extending direction of the linear slit-shaped light transmitting hole are arranged in parallel.
[0040]
In the above configuration, in order to maximize the amount of light passing through the light transmitting hole when the light collected by the light collecting structure 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.
[0041]
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.
[0042]
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.
[0043]
Further, since the cylindrical condensing curved surface can form an elongated condensing structure, if the elongated condensing structures are arranged side by side, a light exit surface of a large condensing element can be manufactured. That is, since a light-collecting element having a light-collecting structure can be easily formed as compared with a light-collecting structure having a shorter or more complicated shape, it is also useful to reduce the cost of the light-collecting element. This advantage similarly applies to the formation of the light reflection layer.
[0044]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0045]
In addition, the solar cell according to the present invention, in order to solve the above-described problems, in addition to the above configuration, the light reflection layer having the linear slit-shaped light transmission hole, the focal length of the cylindrical condensing curved surface Are also provided at positions close to the cylindrical converging curved surface.
[0046]
According to the above configuration, when the solar cell is installed outdoors, the incident angle of the solar ray incident on the solar cell varies depending on the time of day. The purpose of this configuration is to suppress a decrease in power generation efficiency due to the change in the incident angle.
[0047]
For example, consider light incident perpendicularly and light obliquely incident on a cylindrical axis of a cylindrical condensing curved surface. The vertically incident light is condensed linearly at the focal point of the cylindrical converging curved surface, parallel to the extending direction of the linear slit-shaped light transmitting hole. On the other hand, the obliquely incident light has its condensing position closer to the cylindrical condensing curved surface than the condensing position of the vertically incident light.
[0048]
Therefore, when the light reflecting layer having the linear slit-shaped light transmitting hole is disposed at the focal point of the cylindrical condensing curved surface, the vertically incident light passes through the linear slit light transmitting hole, but the obliquely incident light is Since the light is condensed before reaching the linear slit-shaped light transmitting hole, it becomes a spread light beam after being collected and reaches the linear slit-shaped light transmitting hole. As a result, a part of the light obliquely incident irradiates the light reflection layer around the linear slit-shaped light transmission, so that the transmittance is reduced.
[0049]
Therefore, according to the above configuration, the light reflection layer is arranged closer to the cylindrical light-collecting curved surface in consideration of the fact that the light-condensing position of obliquely incident light approaches the cylindrical light-collecting curved surface. Both the vertically incident light and the obliquely incident light can pass through the linear slit-shaped light transmitting hole, or the amount of obliquely incident light can be increased. Therefore, power generation efficiency can be improved.
[0050]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0051]
Further, in order to solve the above-mentioned problems, the solar cell according to the present invention, in addition to the above-described configuration, assuming that the focal length of the cylindrical converging curved surface is F, the light exiting side of the cylindrical converging curved surface. The distance between the surface and the position where the linear slit-shaped light transmitting hole is provided is (3F / 7) or more and (6F / 7) or less.
[0052]
According to the above configuration, if the interval is smaller than (3F / 7), the position of the linear slit-shaped light transmitting hole is more cylindrical than the light condensing position in a range where the angle of incidence of obliquely incident light is small. Since the light flux is too close to the curved surface, the spread light flux 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.
[0053]
On the other hand, if the distance is larger than (6F / 7), the light condensing position is located between the linear slit light transmitting hole and the cylindrical light condensing curved surface in a range where the angle of incidence of the obliquely incident light is large. Since the light condensing position and the position of the linear slit-shaped light transmitting hole are too far apart, the light beam in a spread state after being condensed irradiates the linear slit 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.
[0054]
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. .
[0055]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0056]
Further, in order to solve the above problem, the solar cell according to the present invention, in addition to the above configuration, when the width of the cylindrical converging curved surface is W, the width of the linear slit-shaped light transmitting hole is: It is not less than (W / 5) and not more than (3W / 5).
[0057]
In the above configuration, if the width of the linear slit-shaped light transmitting hole is smaller than (W / 5) 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 (3W / 5), light to be multiple-reflected between the light reflecting layer and the photoelectric conversion 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.
[0058]
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.
[0059]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0060]
Further, in order to solve the above problems, the solar cell according to the present invention includes, in addition to the above configuration, a cylindrical axis direction of the cylindrical condensing curved surface, and a plane perpendicular to the condensing element, It is characterized by being installed facing east and west.
[0061]
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. .
[0062]
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.
[0063]
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.
[0064]
In addition, the configuration described as the present invention may be arbitrarily combined with each configuration described as the invention as needed.
[0065]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS. 1 to 6 and FIG.
[0066]
(Example of configuration as a premise of the present invention)
FIG. 13 is a cross-sectional perspective view of a solar cell filed by the present inventor in Japanese Patent Application No. 2001-296409 (not disclosed at the time of confirmation before the present application). The solar cell has a solar cell element in which a photoelectric conversion layer 2 is provided on a substrate 1 also serving as a support, a cylindrical condensing curved surface group 4 on the incident side of incident light 9, and a straight line on the solar cell element side. The light converging element 3 is provided with a light reflection layer 7 having a slit-shaped light transmission hole group 8.
[0067]
In the cylindrical light-collecting curved surface group 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. . 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.
[0068]
The linear slit-shaped light transmitting hole group 8 formed on the transparent substrate 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.
[0069]
Here, in FIG. 13, the corresponding linear slit-shaped light transmission is located on the optical axis of the incident light 9 that enters from directly above the cylindrical condensing curved surface and at the position where the light is condensed. Holes are located.
[0070]
In the above configuration, the incident light 9 perpendicularly incident on the cylindrical condensing curved surface group 4 (condensing element 3) is linearly collected by the cylindrical condensing curved surface group 4 on the linear slit-shaped light transmitting hole group 8. The light is irradiated to 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 7 provided on the light-collecting element 3 and again enters the photoelectric conversion layer 2 of the solar cell element. As described above, light incident from the linear slit-shaped light transmitting hole group 8 is multiple-reflected between the solar cell element and the light reflection layer 7, 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.
[0071]
Therefore, the light reflection layer 7 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-shaped light transmission hole group 8. The facing surface may be any light reflecting layer 7 that can reflect light.
[0072]
On the other hand, the surface on the light incident side of the light reflecting layer 7, 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 7 is formed only of a material having light reflectivity, that is, the light incident side surface of the light reflecting layer 7 also has a light reflecting function.
[0073]
Further, here, the description has been made using the cylindrical condensing curved surface as the condensing element having the condensing region, but it is sufficient that the condensing element has a function of condensing light in the linear slit-shaped light transmitting hole group 8, It is not limited to this. For example, FIG. 13 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.
[0074]
Further, it is also possible to condense light to the linear slit-shaped light transmitting hole group 8 by configuring each condensing area with a Fresnel light 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.
[0075]
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.
[0076]
However, as a result of intensive study, in the solar cell having the configuration shown in FIG. 13, since the cylindrical converging curved surface group 4 exists on the incident side of the incident light 9, the cylindrical converging curved surface group 4 It has been found that there is a problem that dust and the like easily adhere to the concave portion. For this reason, it was newly confirmed that the power generation efficiency gradually deteriorates with long-term use of the solar cell. Therefore, in the solar cell, in order to maintain high power generation efficiency for a long period of time, it is necessary to periodically clean the cylindrical converging curved surface group 4. This leads to an increase in maintenance work and an increase in running cost.
[0077]
(Configuration example of the present invention)
FIG. 1 is a cross-sectional perspective view of a solar cell of the present invention having improved environmental resistance in view of the above-described new problem.
[0078]
As shown in FIG. 1, the solar cell of the present invention has a configuration in which the light reflecting layer 7 is separated from the light-collecting element 3 in the solar cell configuration described with reference to FIG. Is separately provided between the light-collecting element 3 and the solar cell element.
[0079]
Further, in the light-collecting device 3 of the present invention, the positional relationship between the light incident surface and the light-emitting surface is reversed with respect to the light-collecting device 3 shown in FIG. That is, in the solar cell of the present invention, the light incident surface of the light-collecting element 3 is a flat plane portion 5, and the group of cylindrical light-condensing curved surfaces 4 of the light-collecting element 3 is a light emitting surface. Further, the cylindrical condensing curved surface group 4 and the light reflection layer 7 provided on the transparent substrate 6 face each other.
[0080]
According to the above configuration, the incident light 9 enters from the flat portion 5 of the light-collecting element 3 and is condensed by the cylindrical light-condensing curved surface group 4 on the linear slit-shaped light transmitting hole group 8. More specifically, each cylindrical condensing curved surface group constituting the cylindrical condensing curved surface group 4 condenses the incident light 9 on the corresponding linear slit light transmitting hole of the linear slit light transmitting hole group 8, respectively. .
[0081]
The light transmitted through the straight slit-shaped light transmission hole group 8 is multiple-reflected between the light reflection layer 7 and the photoelectric conversion layer 2 as described with reference to FIG. It can be higher than that.
[0082]
As described above, since the solar cell of the present invention has no irregularities on the light incident surface, unlike the solar cell shown in FIG. 13, adhesion of dust is suppressed, and high power generation efficiency can be maintained for a long time. Become.
[0083]
Moreover, in the solar cell, periodic cleaning of the light-collecting element 3 is unnecessary or less necessary in order to maintain high power generation efficiency for a long period of time. This reduces maintenance work or running costs. Therefore, it can be said that the solar cell of the present invention has a structure with high environmental resistance, which is adapted to applications where rapid growth is expected in the future, such as installation outdoors.
[0084]
FIG. 2 shows a configuration example of the solar cell element. That is, the solar cell element of this example was provided on the substrate 1 also serving as a support, in order to improve the electrical contact between the electrode metal layer 10 having a light reflection effect and the electrode metal layer 10 and the semiconductor layer. A polycrystalline Si semiconductor layer 11 doped with one of p-type impurities or n-type impurities at a high concentration, a polycrystalline Si semiconductor layer 12 slightly doped with impurities of the same conductivity type as the polycrystalline Si semiconductor layer 11, A polycrystalline Si semiconductor layer 13 doped with impurities of a conductivity type opposite to that of the crystalline Si semiconductor layers 11 and 12 at a high concentration, a current collecting electrode 14 for extracting current, and a conductive transparent film for efficiently capturing light. And an anti-reflection layer 15.
[0085]
In such a solar cell element, sunlight is introduced from the antireflection layer 15 side, and photoelectric conversion is performed in the polycrystalline Si semiconductor layers 11 to 13. However, the anti-reflection layer 15 generally has wavelength dependency, and it is impossible to completely prevent reflection of light of all wavelengths. become. Further, light applied to the current collecting electrode 14 for extracting a current is completely reflected by the current collecting electrode 14.
[0086]
For such a reason, in the solar cell of the present invention, the reflected light from the photoelectric conversion layer 2 of the solar cell element is reflected by the light reflection layer 7 provided on the transparent substrate 6, and the photoelectric conversion of the solar cell element is performed again. The power generation efficiency is increased by making the light incident on the layer 2.
[0087]
Next, FIGS. 3 and 4 are diagrams illustrating a method of installing the solar cell. In the present specification, as shown in FIG. 3, the cylindrical axis direction of the cylindrical converging curved surface group 4 is called a vertical direction 16, and is included in a plane orthogonal to the vertical direction 16 and parallel to the plane portion 5. The direction is referred to as a lateral direction 17.
[0088]
In a solar cell using sunlight as a light source, efficient power generation needs to be performed regardless of the incident angle of sunlight. For example, as shown in FIG. 4, at 8 o'clock in the morning, sunlight enters the solar cell from obliquely above east, at 12:00 noon, the sunlight enters the solar cell from vertically above, and at 16:00 in the evening, sunlight enters the solar cell. Enters the solar cell obliquely from above the west. In order to perform efficient power generation, the sunlight whose incident angle changes within the day should be efficiently condensed by the cylindrical converging curved surface group 4 and incident on the linear slit-shaped light transmitting hole group 8. Is required.
[0089]
Here, as shown in FIG. 3, the incident light 9 as sunlight is incident on the incident angle Q ₁ , The plane including the optical axis and including the cylindrical axis also has an incident angle Q ₁ The position where the light is condensed linearly by the cylindrical converging curved surface group 4 moves along the horizontal direction 9. As a result, the optical axis deviates from the linear slit-shaped light transmitting hole group 8, so that the incident light 9 condensed by the cylindrical condensing curved surface group 4 does not enter the linear slit light transmitting hole group 8, but is reflected by the light. It is reflected by the layer 7. Therefore, the power generation efficiency is significantly reduced.
[0090]
On the other hand, the incident light 9 is incident at an incident angle Q ₂ , The inclination of the plane including the optical axis and the cylindrical axis is determined by the incident angle Q ₂ The position where light is condensed linearly by the cylindrical converging curved surface group 4 exists on the plane. Therefore, the state where the optical axis passes through the linear slit-shaped light transmitting hole group 8 is maintained, so that the incident light 9 collected by the cylindrical light collecting curved surface group 4 is incident on the linear slit light transmitting hole group 8. . As a result, it is possible to maintain high power generation efficiency even when sunlight enters obliquely from above.
[0091]
Therefore, as shown in FIG. 4, the solar cell of the present invention is installed so that the vertical direction 16 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, the solar cell shown in FIG. 1 is installed so that a plane including the cylindrical axial direction of the cylindrical condensing curved surface and perpendicular to the condensing element 3 faces the east-west direction. Accordingly, high power generation efficiency can be maintained even in the morning and evening when sunlight is obliquely incident from above.
[0092]
In addition, the solar cell of the present invention has an advantage that the incident light 9 is refracted in the plane portion 5 of the light-collecting element 3 (FIG. 1), so that the incident angle with respect to the cylindrical light-condensing curved surface group 4 is reduced. ing.
[0093]
That is, assuming that the incident angle of the incident light 9 is Q0, the refractive index of the atmosphere is n0, and the refractive index of the light-collecting element 3 is n1, the refraction angle Q1 of the incident light 9 in the plane portion 5 is defined by the law of refraction (n0 sin Q0 = n1 sin Q1). ). Since the refractive index n0 of the atmosphere is 1, Q1 <Q0 is satisfied by using the light-collecting element 3 made of a material satisfying n1> 1.
[0094]
Therefore, the refraction angle Q1 in the plane portion 5 of the light-collecting element 3, that is, the substantial incident angle on the cylindrical light-collecting element group 4 can be made smaller than the incident angle Q0 of the incident light 9. The light beam condensed by the cylindrical light-condensing element group 4 is narrowed down as the incident angle of the parallel light incident on the cylindrical light-condensing element group 4 becomes smaller. For this reason, the light-collecting element 3 of the present invention makes it possible to realize efficient light-collecting characteristics and, consequently, realize high power generation efficiency.
[0095]
Next, as shown in FIG. 4, FIG. 5 shows an incident angle Q0 (Q in FIG. 3) on the cylindrical condensing curved surface group 4 of the solar cell of the present invention from obliquely above in the vertical direction 16. ₂ (Corresponding to FIG. 2) shows the result of calculation of the condensing state when parallel light is incident. Here, the calculation of the light-collecting state is performed by setting the refractive index n0 of the air to 1.0, the refractive index n1 of the light-collecting element 3 to 1.5, and the cylindrical light-converging curved surface group 4 having a radius of curvature of 10 mm to a width of 10 mm. Were performed at the intervals of
[0096]
When the refractive index n2 between the cylindrical condensing curved surface group 4 and the light reflecting layer 7 is different from the refractive index between the light reflecting layer 7 and the solar cell element, the linear slit light transmitting hole group 8 is formed. The transmitted light is refracted, but all the light that has passed through the linear slit-shaped light transmission hole group 8 repeatedly absorbs and partially reflects between the photoelectric conversion layer 2 and the light reflection layer 8 to generate power. There is no need to find the optical path to contribute to efficiency. Therefore, the calculation was performed assuming that the refractive index between the light reflecting layer 7 and the solar cell element was equal to the refractive index n2 between the cylindrical condensing curved surface group 4 and the light reflecting layer 7.
[0097]
Further, between the cylindrical light-condensing curved surface group 4 and the light reflecting layer 7, in order to realize a light condensing function by the cylindrical light-condensing curved surface group 4, at least a refractive index smaller than the refractive index n 1 of the light condensing element 3. It is necessary to provide a transparent body (transparent medium) having the following formula. Here, air (n2 = 1) is provided between the cylindrical condensing curved surface group 4 and the light reflecting layer 7. Calculated as
[0098]
In FIG. 5, (a), (b), and (c) are the results calculated for the cases of Q0 = 0 °, Q0 = 40 °, and Q0 = 60 °, respectively. The unit of the numerical scale in the figure is mm. The incident light 9 obliquely from above in the vertical direction 16 is collected while traveling along the vertical direction in the solar cell of the present invention. In FIG. 5, the light condensing state in that case is projected on a cross section cut along a plane perpendicular to the light condensing element 3 including the lateral direction 17, and a change in the light condensing state due to the incident angle Q0 is examined. I have.
[0099]
In addition, when the substantial incident angle Q1 to the cylindrical converging curved surface group 4 is calculated according to the law of refraction, they are Q1 = 0 °, Q1 = 25.4 °, and Q1 = 35.7 °, respectively.
[0100]
As can be seen from FIG. 5, as the incident angle increases, the condensing position of the incident light 9 moves in the direction of the cylindrical converging curved surface group 4. Therefore, when the linear slit light transmitting hole group 8 is provided at the light condensing position at Q0 = 0 ° shown in FIG. 5A, that is, at the position of the focal length F of the cylindrical light condensing curved surface group 4, FIG. In the case of Q0 = 60 ° shown in c), the incident light from the end of each cylindrical condensing curved surface group 4 is applied to the light reflecting layer 7 instead of the linear slit light transmitting hole group 8. Therefore, as the incident angle of the incident light 9 incident on the vertical direction 16 increases, the light reflected by the light reflecting layer 7 increases. As a result, the power generation efficiency is slightly reduced as the incident angle increases.
[0101]
As a countermeasure against this, as shown in FIG. 6, a linear slit-shaped light transmitting hole group 8 is provided at a position closer to the cylindrical converging curved surface group 4 than the focal length F of the cylindrical converging curved surface group 4, and The slit width of the slit-shaped light transmission hole group 8 was optimized. In other words, the position on the optical axis of the linear slit-shaped light transmitting hole group 8 is set to satisfy d <F when the distance d between the cylindrical condensing curved surface and the corresponding linear slit-shaped light transmitting hole is set. .
[0102]
Thereby, all the incident light is transferred to the linear slit-shaped light transmission hole group 8 regardless of whether Q0 = 0 ° shown in FIG. 5A or Q0 = 60 ° shown in FIG. Light can be collected. That is, even when the incident angle increases, the incident light can be efficiently condensed to the linear slit-shaped light transmitting hole group 8 and high power generation efficiency can be realized.
[0103]
【Example】
[Example 1]
As Example 1 of the present invention, a solar cell having the configuration shown in FIG. 1 was manufactured.
[0104]
The solar cell element was produced by a method similar to the conventional method. The manufacturing method is described below.
[0105]
As shown in FIG. 2, a 100-nm-thick Al film having a light reflection effect is formed on a stainless steel substrate 1 also serving as a support. _0.95 Ti _0.05 After the electrode metal layer 10 made of an alloy is formed by sputtering, one of p-type impurities and n-type impurities provided to improve the electrical contact between the electrode metal layer 10 and the semiconductor layer is highly concentrated. Doped polycrystalline Si semiconductor layer 11, polycrystalline Si semiconductor layer 12, lightly doped with impurities of the same conductivity type as polycrystalline Si semiconductor layer 11, polycrystalline Si semiconductor layer 11, conduction opposite to polycrystalline Si semiconductor layer 12 A polycrystalline Si semiconductor layer 13 doped with a high-type impurity at a high concentration was sequentially formed by a plasma CVD apparatus.
[0106]
The polycrystalline Si semiconductor layer 11 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. On the electrode metal layer 10, a 30 nm-thick polycrystalline Si semiconductor layer 11 doped with P at a high concentration was deposited.
[0107]
Next, the polycrystalline Si semiconductor layer 12 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. In this manner, a 150 nm-thick polycrystalline Si semiconductor layer 12 lightly doped with P was deposited on the polycrystalline Si semiconductor layer 11.
[0108]
The polycrystalline Si semiconductor layer 12 is a layer that absorbs light, generates electric charge, and performs power generation. In order to sufficiently absorb light, in a conventional solar cell, the thickness is usually 5,000 nm or more and 50,000 nm or less. Is set. On the other hand, in the present invention, since the incident light from the linear slit-shaped light transmitting hole group 8 repeats absorption and partial reflection between the photoelectric conversion layer 2 and the light reflection layer 7, the polycrystalline Si semiconductor layer 12 can be made thinner. 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.
[0109]
Next, the polycrystalline Si semiconductor layer 13 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. Thus, on the polycrystalline Si semiconductor layer 12, a p-type polycrystalline Si semiconductor layer 13 doped with B and having a thickness of 15 nm was deposited.
[0110]
Next, the substrate 1 on which a pn junction formed of the polycrystalline Si semiconductor layers 11 to 13 is formed is attached to a sputtering apparatus, and a shielding mask corresponding to the shape of the comb-shaped current collecting electrode 14 is placed on the polycrystalline Si semiconductor layer of the substrate 1. 13 with a thickness of 100 nm using an AlTi alloy target. _0.95 Ti _0.05 A comb-shaped current collecting electrode 14 having a width of 0.1 mm and an interval of 5 mm made of an alloy was formed.
[0111]
Finally, In ₂ O ₃ By performing reactive sputtering in an oxygen atmosphere using a target, a conductive transparent film having a thickness of 65 nm was formed as an antireflection layer 15 on the polycrystalline Si semiconductor layer 13 and the comb-shaped current collecting electrode 14.
[0112]
On the other hand, as the light-collecting device 3 shown in FIG. 1, a polycarbonate resin light-collecting device having a refractive index of 1.5 was produced by an injection molding method. The condensing curved surface group had a configuration in which cylindrical condensing curved surface groups 4 having a curvature radius of 10 mm were arranged at intervals of 10 mm in width, and the focal length F thereof was approximately 35 mm.
[0113]
Next, as the light reflecting layer 7 having the linear slit-shaped light transmitting hole group 8, the linear slit light transmitting hole group 8 is formed on a polycarbonate resin transparent substrate 6 having a refractive index of 1.5 and a plate thickness of 2 mm. In the state where the shielding plate to be attached is mounted, the Al _0.95 Ti _0.05 After forming the light reflecting layer 7 made of an alloy, the light shielding layer 7 was formed by removing the shielding plate. The slit width WS of the linear slit-shaped light transmitting hole group 8 was set to a width (WS = 2.5 mm) which was 幅 of the width W (W = 10 mm) of the cylindrical condensing curved surface group 4.
[0114]
The power generation efficiency of the solar cell thus manufactured was investigated. In this case, incident light 9 as sunlight enters from the side of the flat part 5 of the light-collecting element 3 and is condensed by the group of cylindrical condensing curved surfaces 4, thereby transmitting through the light-transmitting hole group 8. A spacer was provided and fixedly arranged between the light-collecting element 3, the transparent substrate 6, and the solar cell element having the photoelectric conversion layer 2 so that the emitted light was irradiated to the photoelectric conversion layer 2.
[0115]
As Comparative Example 1, the power generation efficiency of a solar cell having only the solar cell element was also investigated.
[0116]
[Table 1]

[0117]
Table 1 shows that when the position on the optical axis of the linear slit-shaped light transmitting hole group 8, that is, the distance d between the cylindrical condensing curved surface group 4 of the condensing element 3 and the light reflecting layer 7 is changed, the incident light is changed. 9 shows the result of examining how the power generation efficiency changes for the 9 incident angles Q1.
[0118]
As a light source, 100 mW / cm ² The light of the intensity | strength was irradiated from diagonally above. Further, Table 1 compares the magnitudes of the open-circuit voltage V and the short-circuit current I of the solar cell of the present invention with Comparative Example 1 assuming that the open-circuit voltage V and the short-circuit current I of the solar cell of Comparative Example 1 arranged side by side are 100%. The results are shown.
[0119]
When the focal length F is 35 mm and d = 35 mm (F), the open-circuit voltage V and the short-circuit current I are both larger than those of Comparative Example 1 at the incident angle Q1 = 0 ° and 40 °. It can be seen that the short-circuit current I is smaller than that of the comparative example 1 at the incident angle Q1 = 60 °.
[0120]
The reason why the short-circuit current I is smaller than that of the comparative example 1 at the incident angle Q1 = 60 ° is that light is condensed near both ends of the cylindrical light-condensing curved surface as described above with reference to FIG. This is because the emitted light cannot pass through the linear slit-shaped light transmitting hole.
[0121]
However, even in this case, the power generation efficiency is higher than that of the comparative example 1 in the time period when the incident angle at which the power generation amount is large and the incident angle is small. In Example 1, a larger amount of power generation is obtained than in Comparative Example 1.
[0122]
In addition, Table 1 shows that the present invention is better than Comparative Example 1 at all incident angles up to the incident angle Q = 60 ° when d is 15 mm (3F / 7) or more and 30 mm (6F / 7) or less. It can be seen that both the open-circuit voltage V and the short-circuit current I of the solar cell of FIG. Therefore, in the solar cell of Example 1, the distance d between the cylindrical condensing curved surface group 4 of the condensing element 3 and the light reflecting layer 7 is set to (3F / 7) or more and (6F / 7) or less. desirable.
[0123]
If the distance d is smaller than (3F / 7), the position of the linear slit-shaped light transmitting hole is too close to the cylindrical light-collecting curved surface from the light-collecting position in the range where the incident angle is small, so that the light before the light is condensed. The spread light beam irradiates the linear slit-shaped light transmission 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.
[0124]
On the other hand, if the interval is larger than (6F / 7), 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, and 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.
[0125]
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. .
[0126]
Next, the interval d was fixed to an optimum condition, that is, d = 25 mm (5F / 7), and the open voltage V and the short-circuit current I were investigated by changing the slit width WS of the linear slit-shaped light transmitting hole group 8. Table 2 shows the results.
[0127]
[Table 2]

[0128]
As shown in Table 2, while the width W of the cylindrical condensing curved surface group 4 is 10 mm, the width W per slit is 2 mm (W / 5) or more, and 6 mm (3 W / 5) or less. As a result, for all incident angles up to 60 °, a larger open-circuit voltage V and a shorter-circuit current I than in Comparative Example 1 were obtained.
[0129]
If the slit width WS is too narrow, a part of the condensed light is reflected by the light reflection layer 7 and does not reach the photoelectric conversion layer 2 of the solar cell element, leading to a decrease in power generation efficiency. If the slit width WS is too large, the light that enters from the group of linear slit-shaped light transmitting holes 8 and that is to be multiple-reflected between the photoelectric conversion layer 2 and the light reflecting layer 7 is again transmitted through the linear slit-shaped light transmitting hole. Radiated from hole group 8. As a result, the light use efficiency decreases, which leads to a decrease in power generation efficiency.
[0130]
As described above, in the solar cell of the present invention, the light in which the linear slit-shaped light transmission hole group 8 is formed from the surface of the cylindrical condensing curved surface group 4 with the focal length of the cylindrical condensing curved surface group 4 being F. It is desirable that the distance d to the reflective layer 7 is not less than (3F / 7) and not more than (6F / 7). It is desirable that the width of the cylindrical condensing curved surface group 4 be W and the slit width WS of the linear slit-shaped light transmitting hole group 8 be (W / 5) or more and (3W / 5) or less.
Next, the solar cell having the configuration of Example 1 shown in FIG. 1 and the solar cell having the configuration of Comparative Example 2 shown in FIG. .
[0131]
[Table 3]

[0132]
At the time of measurement, a solar simulator was used as a light source, and 100 mW / cm ² The light having the intensity shown in FIG. Then, assuming that the open-circuit voltage V and the short-circuit current I in the initial state of Example 1 and Comparative Example 2 are 100%, the device is placed outdoors for a certain period of time, and then the measurement is performed again under the same conditions. And were compared with the initial state.
[0133]
As a result, as shown in Table 3, in the solar cell of Example 1, the open-circuit voltage V and the short-circuit current I slightly decreased when the solar battery was left outdoors for 10 days. However, the open-circuit voltage V and the short-circuit current I hardly change, indicating that stable power generation efficiency is secured.
[0134]
On the other hand, in the solar cell of Comparative Example 2, both the open-circuit voltage V and the short-circuit current I gradually decreased as the number of days of standing increased, indicating that the power generation efficiency decreased.
[0135]
This difference in power generation efficiency is due to the difference in the amount of dust adhering to the light collecting element 3 as described above. That is, in the solar cell of Comparative Example 2, along with the increase in the number of days of standing, an increase in dust adhesion was confirmed along the concave portion of the cylindrical light-converging curved surface group 4 as a light incident surface, and this dust adhesion was considered as a power generation efficiency. It is causing the decline. On the other hand, in the solar cell of Example 1, since the light incidence surface is the flat portion 5 and there is no unevenness, such an increase in dust adhesion is not confirmed, and stable power generation efficiency is obtained.
[0136]
In this embodiment, a configuration is described in which a spacer is provided between the light-collecting element 3 (FIG. 1), the transparent substrate 6, and the solar cell element, and each is fixedly arranged. The light collecting element 3, the transparent substrate 6, and the solar cell element may be bonded and fixed to each other using a transparent adhesive. Thereby, the light-collecting element 3 and the solar cell element can be more firmly fixed, and the reliability of the solar cell is improved.
[0137]
However, in order to shorten the focal length of the condensing curved surface group and reduce the thickness of the solar cell, the refractive index n2 of the medium between the condensing element 3 and the linear slit light transmitting hole group 8 is possible. It is desirable to be as small as possible. Therefore, the transparent substrate 6 and the solar cell element are bonded and fixed with a transparent adhesive, while the light collector 3 and the transparent substrate 6 are collected using spacers so that air having a refractive index of 1 is interposed therebetween. It is desirable that the optical element 3 and the transparent substrate 6 be fixed.
[0138]
Next, an example in which a transparent substrate (transparent material layer) having fluorescent characteristics is used as the transparent substrate 6 in the solar cell of Example 1 will be described.
[0139]
In the first embodiment, a transparent substrate made of a polycarbonate resin having a thickness of 2 mm was used as the transparent substrate 6, but here, instead, Y having a particle size of 5 μm was used instead. ₂ O ₂ S: A 2 mm-thick transparent substrate made of polycarbonate resin containing 15% by volume of Eu, Mg, and Ti fluorescent particles was used.
[0140]
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. For this reason, light having a wavelength of about 600 nm generated from the fluorescent particles is also multiple-reflected between the light reflection layer 7 and the solar cell element, so that the power generation efficiency of the solar cell can be increased.
[0141]
The solar cell using the transparent substrate 6 containing no fluorescent particles and the solar cell using the transparent substrate 6 containing the fluorescent particles were measured using a solar simulator at 100 mW / cm. ² , And the open-circuit voltage V and the short-circuit current I of the two were compared so that the incident angle Q0 was 0 °, 40 °, and 60 °. As a result, it was confirmed that the use of the transparent substrate 6 containing the fluorescent particles increased the open-circuit voltage V by about 5% and the short-circuit current I by about 25% at all incident angles Q0.
[0142]
Also, in the solar cell of Example 1, when the transparent substrate 6 and the solar cell element are bonded and fixed using an ultraviolet curable resin (transparent material layer) in which fluorescent fine particles are dispersed, the power generation efficiency is similarly increased. It is possible to do.
[0143]
Here, Y having a particle size of 5 μm ₂ O ₂ S: The fluorescent particles of Eu, Mg, and Ti were contained in an ultraviolet curable resin at 10% by volume, and the transparent substrate 6 and the solar cell element were bonded and fixed using the ultraviolet curable resin having a thickness of 50 μm. 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. And, since the layer of the ultraviolet curable resin is disposed between the light reflection layer 7 and the photoelectric conversion layer 2, light having a wavelength of about 600 nm generated from the fluorescent particles is transmitted to the light reflection layer 7 and the solar cell element. Multiple reflections between This makes it possible to increase the power generation efficiency of the solar cell.
[0144]
A solar cell in which the transparent substrate 6 and the solar cell element are bonded and fixed using an ultraviolet curable resin containing no fluorescent particles, and the transparent substrate 6 and the solar cell element are bonded using an ultraviolet curable resin containing fluorescent particles. 100 mW / cm using a solar simulator with respect to the fixed solar cell of the present invention. ² Is incident so that the incident angles Q0 are 0 °, 40 °, and 60 °, and the open-circuit voltage V is compared with the short-circuit current I. As a result, the open-circuit voltage V Was increased by about 3%, and the short-circuit current I was increased by about 17%.
[0145]
By using a combination of the transparent substrate 6 containing the fluorescent particles and the ultraviolet curable resin, many fluorescent particles are present in the multiple reflection optical path, so that the power generation efficiency can be further improved.
[0146]
As other fluorescent materials, SrAl obtained by adding rare earth elements europium (Eu) and dysprosium (Dy) 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.
[0147]
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.
[0148]
Furthermore, higher power generation efficiency can be obtained by using a plurality of these fluorescent materials simultaneously in an arbitrary combination.
[0149]
[Example 2]
In the first embodiment, the case where the solar cells are arranged so that the vertical direction 16 (FIG. 3) coincides with the east-west direction in consideration of the diurnal movement of the sun has been described. However, since the earth axis is actually tilted, the sunlight 7 enters from obliquely above the horizontal direction 17 depending on the season.
[0150]
For example, when the solar cell is installed so that the incident light 9 as sunlight is incident from right above vertically and condensed on the linear slit-shaped light transmission hole group 8 during the south mid-spring day, Since it is tilted by 23.4 °, at the winter solstice or the summer solstice, the incident light 9 has an incident angle Q of ± 23.4 ° from an oblique upper side in the horizontal direction 17. ₁ Incident. As a result, since the optical axis of the incident light 9 is displaced in the horizontal direction 17 from the linear slit-shaped light transmitting hole group 8, the incident light 9 is reflected by the light reflection layer 7, and the power generation efficiency is significantly reduced.
[0151]
The solar cell according to the second embodiment is configured as shown in FIG. 7 in order to solve the above problem. That is, the light-collecting element 3 provided with the cylindrical light-condensing curved surface group 4 and the transparent substrate 6 provided with the linear slit-shaped light transmitting hole group 8 form the incident angle Q of the incident light 9. ₁ , And is supported so as to be relatively movable in the lateral direction 17.
[0152]
Thus, in response to the change in the incident angle of the sunlight with the season, the light-collecting element 3 and the transparent substrate 6 are relatively moved, and the light-condensing position of the sunlight and the linear slit-shaped light transmitting hole group 8 are changed. Or by allowing the luminous flux formed by the collected sunlight to pass through the group of straight slit-shaped light transmitting holes 8 as much as possible, thereby increasing the sunlight incident on the photoelectric conversion layer 2. Power generation efficiency can be improved.
[0153]
Also, as shown in FIG. 8, even when the transparent substrate 6 and the solar cell element having the photoelectric conversion layer 2 are bonded and fixed with a transparent adhesive or the like, the transparent substrate 6 and the solar cell element are integrally formed. By making it movable, it is also possible to realize high power generation efficiency.
[0154]
In addition, as another means for eliminating the influence of the change in the incident angle of sunlight within the year, the solar cell is rotated in parallel to the east-west direction so that the flat portion 5 of the light-collecting element 3 always receives the sunlight vertically. It may be rotated about an axis. The rotation angle in this case may be at most about 0.25 ° per day.
[0155]
[Example 3]
As Example 3 of the present invention, a solar cell having the configuration shown in FIG. 9 was manufactured.
[0156]
The solar cell according to the third embodiment includes the light-collecting element 3 described in the first embodiment and a solar cell element including the solar cell element transparent substrate 18 and the photoelectric conversion layer 19. Here, the light reflecting layer 7 having the linear slit-shaped light transmitting hole group 8 is provided on the light incident surface of the transparent substrate 18 for a solar cell element, that is, the surface facing the photoelectric conversion layer 19.
[0157]
In this solar cell, light incident from the plane portion 5 of the light-collecting element 3 is condensed by the group of cylindrical light-condensing curved surfaces 4 into a group of linear slit-shaped light transmitting holes 8, and the transparent substrate 18 for a solar cell element is formed. The light passes through and enters the photoelectric conversion layer 19.
[0158]
On the other hand, the reflected light from the photoelectric conversion layer 19 is reflected by the light reflection layer 7 and re-enters the photoelectric conversion layer 19, so that the incident light 9 is multiply reflected between the photoelectric conversion layer 19 and the light reflection layer 7. I do. Thereby, high power generation efficiency is realized.
[0159]
The solar cell element of Example 3 had a configuration as shown in FIG. 10 and was manufactured as follows.
[0160]
First, a 30 nm-thick SnO film is formed on the transparent substrate 18 for a solar cell element. ₂ After the transparent conductive layer 20 is formed by reactive sputtering, a 100 nm-thick Al film is formed by sputtering using an AlTi alloy target while a shielding mask is mounted on the surface of the transparent conductive layer 20. _0.95 Ti _0.05 A comb-shaped current collecting electrode 21 made of an alloy and having a width of 0.1 mm and an interval of 5 mm was formed.
[0161]
Next, a photoelectric conversion layer in which a p-layer 22 as a p-type impurity-doped semiconductor layer, an i-layer 23 as an intrinsic semiconductor, and an n-layer 24 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 of the semiconductor layers 22 to 23 is made of SiH ₄ Gas H ₂ Gas / CH ₄ Gas B ₂ H ₆ A-SiC: H p-layer 22 having a thickness of 15 nm grown by vapor phase using a gas mixture of SiH ₄ Gas H ₂ A-Si: H i-layer 23 having a thickness of 100 nm grown by vapor phase using a gas mixture ₄ Gas H ₂ Gas / PH ₃ An n-layer 24 of a-Si: H having a film thickness of 15 nm was formed by vapor-phase growth using a mixed gas of gases.
[0162]
After forming the photoelectric conversion layer 19, an electrode metal layer 25 made of Al having a light reflection effect and having a thickness of 100 nm is formed by sputtering, and an ultraviolet curable resin is applied on the electrode metal layer 25. The protective film 26 was formed.
[0163]
The power generation efficiency of the solar cell having the light-collecting element 3 of Example 3 and the above-described solar cell element (Comparative Example 3) from which the light-collecting element 3 was removed were compared in the same manner as in Example 1. That is, when the distance d between the cylindrical condensing curved surface group 4 of the condensing element 3 and the light reflecting layer 7 on the transparent substrate 18 for a solar cell element in the third embodiment is changed, the power generation is performed together with the incident angle Q of light. We examined how the efficiency changes.
[0164]
[Table 4]

[0165]
Table 4 shows that the solar cells of Example 3 and Comparative Example 3 were 100 mW / cm using a solar simulator. ² Of light having an intensity of 0.degree. Is incident so that the incident angles Q1 are 0.degree., 40.degree., And 60.degree., And the open-circuit voltage V and the short-circuit current I of the solar cell element of Comparative Example 3 are each set to 100%. 9 shows the open-circuit voltage V and the short-circuit current I of the solar cell of Example 3.
[0166]
The light-collecting element 3 of the third embodiment is the same as that of the first embodiment, and the same result as that of the first embodiment is obtained in the solar cell of the third embodiment.
[0167]
That is, in the solar cell according to the third embodiment, similarly to the first embodiment, the focal length of the cylindrical converging curved surface group 4 is set to F (35 mm), and the surface of the cylindrical converging curved surface group 4 and the light reflecting layer 7 are formed. It is desirable that the distance d between (3F / 7) and (6F / 7) be smaller.
[0168]
As shown in FIG. 11, similarly to the first embodiment, the light transmission hole group 8 is formed between the light-collecting element 3 and the solar cell element having the solar cell element transparent substrate 18 and the photoelectric conversion layer 19. Even in the case where the transparent substrate 6 provided with the light reflecting layer 7 is provided, high power generation efficiency can be realized as in the third embodiment.
[0169]
In the solar cell according to the third embodiment shown in FIGS. 9 and 11, the light-collecting element 3 and the linear slit-shaped light transmitting hole group 8 may be arranged so as to be relatively movable in the horizontal direction 17. As described above, the power generation efficiency can be maintained high while the incident angle of sunlight changes seasonally as described in the second embodiment.
[0170]
As in the first embodiment, as a transparent substrate or a transparent adhesive disposed closer to the photoelectric conversion layer than the light reflection layer 7 having the linear slit-shaped light transmission holes 8, a transparent substrate or a transparent adhesive having fluorescent characteristics is used. By using the agent, it is possible to realize higher power generation efficiency.
[0171]
[Example 4]
As Example 4 of the present invention, a solar cell having the configuration shown in FIG. 12 was manufactured.
[0172]
The solar cell according to the fourth embodiment has a low-refractive-index antireflection film 27 (a transparent material layer having an antireflection function) on the light-incident surface side of the light-collecting element 3 of the solar cell according to the first embodiment, that is, on the plane portion 5. Is formed.
[0173]
As the light-collecting element 3, it is desirable to use a transparent material having a refractive index of about 1.5 or more in order to obtain good light-collecting characteristics. Will occur. As the incident angle of sunlight increases, the ratio of the surface reflection further increases.
[0174]
Therefore, in the fourth embodiment, a film having a smaller refractive index than the light-collecting element 3 such as the low-refractive-index antireflection film 27 is provided on the light incident surface of the light-collecting element 3 so that the surface reflection is reduced by 2%. And the power generation efficiency can be prevented from lowering due to surface reflection.
[0175]
A specific manufacturing method will be described. In the solar cell according to the fourth embodiment, the solar cell manufactured in the first embodiment is further coated on the flat portion 5 of the light-condensing element 3 with an ultraviolet-curable transparent fluororesin using fluorovinyl ether. To cure the transparent fluororesin. Thus, a solar cell including the low-refractive-index antireflection film 27 having a refractive index of 1.35 was manufactured. Although the solar cell of Example 1 had a surface reflection of 4%, the solar cell of Example 4 was able to suppress the surface reflection to 1.4%.
[0176]
Next, using a sunlight simulator, 100 mW / cm ² And the open-circuit voltage V and the short-circuit current I of Example 4 and Example 1 were compared. As a result, it was confirmed that the open-circuit voltage V of the solar cell of Example 4 was increased by about 1% and the short-circuit current I was increased by about 3%.
[0177]
Here, an example in which the low-refractive-index antireflection film 27 is applied to the solar cell of Example 1 is described, but the same applies to the solar cells described in Examples 2 and 3. It is possible to obtain various effects.
[0178]
Although not described in the claims, the technical scope of the present invention further includes the following configuration of the solar cell.
[0179]
For example, in the solar cell according to the present invention, as shown in FIGS. 1, 3, 11, and 12, the light reflection layer having the light transmission hole group includes the light condensing element and the solar cell element. It is characterized by being formed on a first transparent substrate provided between them.
[0180]
With the above configuration, the light-collecting element, the first transparent substrate, and the solar cell element can be formed independently of each other, and damages such as scratches generated in a manufacturing process are suppressed, and high A solar cell having power generation efficiency can be stably manufactured.
[0181]
The photoelectric conversion layer of the solar cell element can be provided on a transparent substrate for a solar cell element as shown in FIGS. 1, 3, 7, 8, and 12.
[0182]
Further, the solar cell according to the present invention is characterized in that, in addition to the above configuration, the first transparent substrate and the solar cell element are fixed by a transparent adhesive.
[0183]
With the above configuration, the first transparent substrate and the solar cell element are bonded and fixed in advance, so that the mechanical strength of the first transparent substrate and the solar cell element is increased. It is possible to suppress a decrease in yield due to breakage and the like, and to realize a thin solar cell.
[0184]
Further, in the solar cell according to the present invention, as shown in FIG. 9, the photoelectric conversion layer is provided on one surface of the transparent substrate for a solar cell element, and the photoelectric conversion layer of the transparent substrate for a solar cell element is provided. The light reflection layer having the light transmission hole group is provided on a surface facing the light reflection layer.
[0185]
With the above configuration, it is possible to form both the photoelectric conversion layer and the light reflection layer on the transparent substrate for a solar cell element, and to manufacture a solar cell with the minimum required number of substrates. It is possible, and the cost of the solar cell can be reduced, and the thickness of the solar cell can be reduced.
[0186]
Also, as shown in FIGS. 1, 3, 7, 8, 11, and 12, a solar cell according to the present invention includes a first transparent substrate between the light-collecting element and the solar cell element. Is provided on the first transparent substrate, the light reflection layer having the light transmission hole group is provided, and the photoelectric conversion layer is provided on the transparent substrate for a solar cell element. And
[0187]
With the above configuration, the light-collecting element, the first transparent substrate, and the solar cell element can be formed independently of each other, and damages such as scratches generated in a manufacturing process are suppressed, and high A solar cell having power generation efficiency can be stably manufactured.
[0188]
The solar cell according to the present invention is characterized in that, in addition to the above-described configuration, as shown in FIGS. 7 and 8, the light-collecting element and the light reflection are relatively movably supported. And
[0189]
According to the configuration, by moving the light-collecting element and the light-reflecting layer relatively, the light condensed by the light-collecting element passes through the light-transmitting hole provided in the light-reflective layer. Can adjust the amount of light passing through the light transmission hole even when the incident angle of light such as sunlight changes due to seasonal changes or time changes. Can be adjusted with respect to the position.
[0190]
Therefore, even when the incident angle of light changes, light can efficiently pass through the light transmitting hole, and the power generation efficiency of the solar cell can be increased regardless of seasonal changes and time changes.
[0191]
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.
[0192]
【The invention's effect】
As described above, the solar cell according to the present invention includes a flat light incident surface on which external light is incident, and a light-condensing element including a light-condensing structure for condensing external light on the light-emitting side. A light reflection layer having a light transmission hole, the light reflection layer being configured such that light condensed by the light collection structure passes through the light transmission hole and then enters the solar cell element, and the solar cell The light-reflecting layer is formed between the solar cell element and the light-collecting element such that light reflected from the element is reflected by the light reflection layer and re-enters the solar cell element.
[0193]
Therefore, between the solar cell element and the reflective layer, the reflected light is multiple-reflected, so that the amount of light irradiated on the photoelectric conversion layer is increased, so that the power generation efficiency (light use efficiency) of the solar cell is increased. can do.
[0194]
In addition, due to the refraction effect on the light incident surface of the light condensing element, the angle of incidence of light incident on the light condensing structure is reduced, and the condensed light beam is narrowed down, so that it is easy to guide the light to the light transmitting hole. As a result, the amount of light introduced between the light reflection layer and the solar cell element can be increased, so that the power generation efficiency can be further increased.
[0195]
Further, since the light incident surface on which the external light is incident is flat, the light incident surface does not have irregularities to which dust and the like easily adhere. For this reason, it is possible to minimize the deterioration of the light-collecting efficiency of the light-collecting element over time due to the attachment of dust or the like. That is, a highly reliable solar cell which is excellent in environmental resistance and can maintain high power generation efficiency for a long time can be provided. As described above, the solar cell according to the present invention has the various effects described above.
[0196]
Further, the solar cell according to the present invention, as described above, in addition to the above configuration, between the light reflection layer and the photoelectric conversion layer, fluorescence of a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer. A transparent material layer that emits light is provided.
[0197]
Therefore, since the amount of light having a wavelength that contributes to photoelectric conversion increases, it is possible to further enhance the power generation efficiency of the solar cell.
[0198]
Further, as described above, the solar cell according to the present invention, in addition to the above configuration, contributes to the photoelectric conversion of the photoelectric conversion layer in the stacked structure between the light reflection layer and the photoelectric conversion layer. It is characterized by including a transparent adhesive layer that emits fluorescence of a wavelength.
[0199]
Therefore, the power generation efficiency of the solar cell can be further increased, similarly to the function of the transparent substrate that emits fluorescence having a wavelength that contributes to the photoelectric conversion of the photoelectric conversion layer described above.
[0200]
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-mentioned effects.
[0201]
Further, as described above, the solar cell according to the present invention, in addition to the above configuration, on the light incident surface of the light-collecting element, a refractive index smaller than the refractive index of the material constituting the light-collecting element. Characterized in that a transparent material layer is provided.
[0202]
Therefore, more light can be made to enter the inside of the light-collecting element because the reflection on the light incident surface is suppressed. In addition, as described above, the light collecting element itself has a function of reducing the incident angle of light incident on the light collecting structure, and the transparent material layer also has a function of reducing the incident angle of light. Join. This makes it easier to guide the light flux to the light transmission holes, and can further increase the amount of light introduced between the light reflection layer and the solar cell element. As a result, there is an additional effect that the power generation efficiency can be further increased.
[0203]
Further, in the solar cell according to the present invention, as described above, in addition to the above configuration, the light-collecting structure 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 cylindrical axis of the cylindrical converging curved surface and the extending direction of the linear slit-shaped light transmitting hole are arranged in parallel.
[0204]
Therefore, the light condensed linearly is efficiently condensed to the linear slit-shaped light transmission hole, and the light incident from the linear slit-shaped light transmission hole is formed between the photoelectric conversion layer and the light reflection layer. The amount of light that is multiple-reflected between the layers and irradiates the photoelectric conversion layer further increases, and the power generation efficiency can be further increased.
[0205]
In addition, the cylindrical light-collecting curved surface is advantageous for easily forming a light-collecting device having a light-collecting structure, and thus is useful for reducing the cost of the light-collecting device. This advantage is similarly applied to the formation of the light reflection layer, and thus has an additional effect that an increase in the manufacturing cost of the solar cell can be avoided.
[0206]
Further, as described above, 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 more cylindrical than the focal length of the cylindrical condensing curved surface. It is characterized in that it is provided at a position close to the condensing curved surface.
[0207]
Therefore, the light reflection layer is arranged close to the cylindrical light-condensing curved surface side in accordance with the light-condensing position of light obliquely incident on the cylindrical axis of the cylindrical light-condensing curved surface. The state in which the spread light beam irradiates the linear slit-shaped light transmission hole can be reduced. That is, since the transmitted light amount of the light obliquely incident can be increased, the power generation efficiency can be further improved.
[0208]
In addition, as described above, the solar cell according to the present invention, in addition to the above configuration, when the focal length of the cylindrical condensing curved surface is F, the surface of the cylindrical condensing curved surface on the light emission side and the straight line. The distance from the position where the slit-shaped light transmitting hole is provided is (3F / 7) or more and (6F / 7) or less.
[0209]
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. It has the further effect of being able to.
[0210]
Further, as described above, in addition to the above configuration, the solar cell according to the present invention has a configuration in which the width of the cylindrical condensing curved surface is W and the width of the linear slit-shaped light transmitting hole is (W / 5) ) Or more and (3W / 5) or less.
[0211]
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, that is, increase in light transmittance and increase in reflectance. It has a further effect.
[0212]
Further, as described above, the solar cell according to the present invention, in addition to the above configuration, includes the cylindrical axis direction of the cylindrical condensing curved surface, and a plane perpendicular to the condensing element faces east-west. It is characterized by being installed as follows.
[0213]
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 it is possible to efficiently condense sunlight to the linear slit-shaped light transmitting hole. It works.
[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 schematic 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.
FIGS. 5A to 5C are explanatory diagrams showing the results of calculating the light-collecting state of the solar cell of the present invention.
FIGS. 6 (a) to 6 (c) show the results of calculating the light-collecting state when the distance between the light-condensing curved surface and the light reflecting layer is reduced in the solar cell of the present invention.
FIG. 7 is a cross-sectional perspective view showing another configuration example of the solar cell of the present invention.
FIG. 8 is a cross-sectional perspective view showing still another configuration example of the solar cell of the present invention.
FIG. 9 is a cross-sectional perspective view showing still another configuration example of the solar cell of the present invention.
FIG. 10 is a schematic sectional view showing another configuration example of the solar cell element used for 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 perspective view showing a configuration example of a solar cell related to the present invention.
FIG. 14 is a schematic cross-sectional view illustrating a configuration example of a conventional solar cell element.
FIG. 15 is a schematic cross-sectional view showing another configuration example of a conventional solar cell element.
FIG. 16 is a schematic cross-sectional view showing yet another configuration example of a conventional solar cell element.
[Explanation of symbols]
1 substrate
2 Photoelectric conversion layer
3 Condensing element
4 Cylindrical condensing curved surface group (condensing structure)
5 flat part (light incident surface)
6 Transparent substrate (transparent material layer)
7 Light reflection layer
8 Linear slit-shaped light transmission holes (light transmission holes)
9 Incident light (external light)
16 vertical direction
17 horizontal direction
18 Transparent substrate for solar cell element
19 Photoelectric conversion layer
27 Low-refractive-index antireflection film (transparent material layer having antireflection function)
F focal length
Q, Q ₁ , Q ₂ Incident angle
d interval

Claims (9)

A solar cell element having a photoelectric conversion layer,
A light-condensing element having a flat light incident surface on which external light is incident and a light-condensing structure for condensing external light on the light-emitting side,
A light reflection layer having a light transmission hole,
The light reflecting layer is such that light condensed by the light condensing structure passes through the light transmitting hole and then enters the solar cell element, and reflected light from the solar cell element is reflected by the light reflecting layer. A solar cell formed between the solar cell element and the light-collecting element so as to re-enter the solar cell element. The solar cell according to claim 1, wherein a transparent material layer 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. . 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. The solar cell according to 1. 2. The solar cell according to claim 1, wherein a transparent material layer having a smaller refractive index than a material forming the light collecting element is provided on a light incident surface of the light collecting element. 3. . The light-collecting structure is a cylindrical light-collecting curved surface, the light-transmitting hole is a linear slit-shaped light-transmitting hole, and the direction of the cylindrical axis of the cylindrical light-collecting curved surface and the extension of the linear slit-shaped light-transmitting hole. The solar cell according to claim 1, wherein the direction is arranged in parallel. The light reflection layer having the linear slit-shaped light transmission hole is provided at a position closer to the cylindrical converging curved surface than the focal length of the cylindrical converging curved surface. Solar cells. Assuming that the focal length of the cylindrical condensing curved surface is F, the distance between the surface on the light emitting side of the cylindrical condensing curved surface and the position where the linear slit-shaped light transmitting hole is provided is (3F / 7) or more, The solar cell according to claim 5, wherein the ratio is (6F / 7) or less. The width of the linear slit-shaped light transmitting hole is not less than (W / 5) and not more than (3W / 5), where W is the width of the cylindrical condensing curved surface. Solar cells. The solar cell according to claim 5, 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 east-west.

Images