JP5360818B2 - Tandem solar cell and production method thereof - Google Patents

Tandem solar cell and production method thereof Download PDF

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JP5360818B2
JP5360818B2 JP2009136219A JP2009136219A JP5360818B2 JP 5360818 B2 JP5360818 B2 JP 5360818B2 JP 2009136219 A JP2009136219 A JP 2009136219A JP 2009136219 A JP2009136219 A JP 2009136219A JP 5360818 B2 JP5360818 B2 JP 5360818B2
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山本▲あき▼勇
明弘 橋本
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University of Fukui
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Description

本発明は、吸収波長帯域の異なる光電変換セルを複数重ねてなるタンデム形太陽電池及びその生産方法に関し、特に太陽光スペクトルを有効に利用して高い光電変換効率を得ることのできるタンデム太陽電池及びその生産方法に関する。   The present invention relates to a tandem solar cell in which a plurality of photoelectric conversion cells having different absorption wavelength bands are stacked, and a method for producing the same, and in particular, a tandem solar cell capable of obtaining a high photoelectric conversion efficiency by effectively using a solar spectrum, and It relates to the production method.

太陽電池は、光エネルギーを電気エネルギーに変換する発電素子で、クリーンなエネルギー供給源として利用の拡大が図られている。このような太陽電池においては、変換効率の向上が今後の重要な課題の一つであり、そのために、吸収波長帯域の異なる光電変換セルを複数重ねてなるタンデム形太陽電池も開発されている。例えば、InGaP/GaAs/Ge３接合タンデム太陽電池では、非集光で３３％、５００倍集光で４０％という高い変換効率を有することが知られている。また、前記したInGaP/GaAs/Ge３接合タンデム太陽電池のGe太陽電池層をSi太陽電池層に置き換えたInGaP/GaAs/Si３接合タンデム太陽電池は、InGaP/GaAs/Ge３接合タンデム太陽電池よりも高い変換効率を有すると予測されている。   A solar cell is a power generation element that converts light energy into electric energy, and its use is being expanded as a clean energy supply source. In such a solar cell, improvement of conversion efficiency is one of important issues in the future, and for this purpose, a tandem solar cell in which a plurality of photoelectric conversion cells having different absorption wavelength bands are stacked has been developed. For example, an InGaP / GaAs / Ge three-junction tandem solar cell is known to have a high conversion efficiency of 33% for non-condensing and 40% for 500 times condensing. The InGaP / GaAs / Si3 junction tandem solar cell in which the Ge solar cell layer of the InGaP / GaAs / Ge3 junction tandem solar cell is replaced with a Si solar cell layer has a higher conversion than the InGaP / GaAs / Ge3 junction tandem solar cell. Expected to have efficiency.

ところで、Si太陽電池層とGaAs太陽電池層とを接続する方法としては、例えば、Si基板上にヘテロエピタキシャル成長法のような結晶成長法によってGaAs太陽電池層を形成するものが考えられるが、この方法では、Si太陽電池層とGaAs太陽電池層との格子定数及び熱膨張係数が大きく異なることから、良好な接続は得られないという問題がある。
特許文献１では、AlAs層を介してGaAs基板上に作製したGaAs太陽電池をSeS2を接着層としてSi太陽電池に接着したのち、AlAsをエッチングすることによりGaAs基板を分離する方法が記載されている（例えば段落００２７参照）が、基板として高価なGaAsを用いると、コスト高になるという問題がある。
また、特許文献２には、InGaP／GaAsモノリシック太陽電池を基板から剥離することが記載されているが（段落０００２〜０００３参照）、この技術は、基板が割れやすいという問題がある。この問題を解決するために、特許文献２に記載の発明では、GaAs等の半導体基板上にInGaP等からなる中間層を形成し、その上に太陽電池素子を形成した後に、GaAs半導体基板を溶解除去させるようにしているが、特許文献２に記載の発明では、基板として高価なGaAsを使用すると製造コストが高くなるという問題がある。 By the way, as a method of connecting the Si solar cell layer and the GaAs solar cell layer, for example, a method of forming a GaAs solar cell layer on a Si substrate by a crystal growth method such as a heteroepitaxial growth method can be considered. However, since the lattice constant and the thermal expansion coefficient of the Si solar cell layer and the GaAs solar cell layer are greatly different, there is a problem that a good connection cannot be obtained.
Patent Document 1 describes a method in which a GaAs solar cell fabricated on a GaAs substrate via an AlAs layer is bonded to a Si solar cell using SeS 2 as an adhesive layer, and then the AlGaAs is etched to separate the GaAs substrate. However, if expensive GaAs is used as a substrate, there is a problem that the cost increases.
Patent Document 2 describes that an InGaP / GaAs monolithic solar cell is peeled from a substrate (see paragraphs 0002 to 0003), but this technique has a problem that the substrate is easily broken. In order to solve this problem, in the invention described in Patent Document 2, an intermediate layer made of InGaP or the like is formed on a semiconductor substrate such as GaAs, a solar cell element is formed thereon, and then the GaAs semiconductor substrate is dissolved. Although it is made to remove, in invention of patent document 2, there exists a problem that manufacturing cost will become high when expensive GaAs is used as a board | substrate.

特開２０００−２７７７７９号公報JP 2000-277779 A 特開２００４−３１９９３４号公報JP 2004-319934 A

本発明は上記の問題に鑑みてなされたもので、効率良く低コストで生産が可能なInGaP/GaAs/Si３接合構造の太陽電池層を含むタンデム太陽電池及びその生産方法の提供を目的とする。   The present invention has been made in view of the above problems, and an object of the present invention is to provide a tandem solar cell including a solar cell layer having an InGaP / GaAs / Si 3 junction structure that can be produced efficiently and at low cost, and a production method thereof.

上記の課題を解決するために、本発明の発明者が鋭意研究を行った結果、GaAs太陽電池層との間で結晶成長法の適用が可能なGe介在層を介して、Si太陽電池層とGaAs太陽電池層とを接着することに想到した。
すなわち、請求項１に記載のタンデム太陽電池は、InGaP/(In)GaAs/Si３接合構造の太陽電池層を含むタンデム太陽電池において、(In)GaAs太陽電池層とSi太陽電池層とが、前記(In)GaAs太陽電池層の一部に形成されたGe介在層を介して接着されている構成としてある。
ここで、「(In)GaAs」は、InGaAs又はGaAsのいずれかであってもよいことを意味する。Ge介在層は、InGaP/(In)GaAs/Si３接合タンデム太陽電池を生産するに当たり、破損等の不都合を生じない範囲内で、また、製品としてのタンデム太陽電池の構造的強度を十分に保てる範囲内で、 Si太陽電池層への入射光量を最大するように、(In)GaAs太陽電池層及びSi太陽電池層に比して可能な限り小さくするのが好ましい。 In order to solve the above-mentioned problems, the inventors of the present invention have conducted intensive research, and as a result, a Si solar cell layer and a GaAs solar cell layer can be applied through a Ge intervening layer that can be applied with a crystal growth method. The idea was to bond the GaAs solar cell layer.
That is, the tandem solar cell according to claim 1 is a tandem solar cell including a solar cell layer having an InGaP / (In) GaAs / Si3 junction structure, wherein the (In) GaAs solar cell layer and the Si solar cell layer are It is configured to be bonded via a Ge intervening layer formed in a part of the (In) GaAs solar cell layer.
Here, “(In) GaAs” means that either InGaAs or GaAs may be used. Ge intervening layer is within the range that does not cause inconvenience such as breakage when producing InGaP / (In) GaAs / Si 3 junction tandem solar cells, and within the range where the structural strength of tandem solar cells as a product can be kept sufficiently. Among them, it is preferable to make it as small as possible as compared with the (In) GaAs solar cell layer and the Si solar cell layer so as to maximize the amount of light incident on the Si solar cell layer.

本発明のタンデム太陽電池は、InGaP/(In)GaAs/Si３接合構造の太陽電池層を含んでいればよく、この３接合構造の太陽電池層でタンデム太陽電池を構成するものとしてもよいし、この３接合構造の太陽電池層以外の太陽電池層を一つ又は複数有していてもよい。例えば、請求項２に記載するように、前記Si太陽電池層の他面にGe太陽電池層を形成し、InGaP/(In)GaAs/Si/Ge４接合構造の太陽電池層であってもよい。   The tandem solar cell of the present invention only needs to include a solar cell layer having an InGaP / (In) GaAs / Si 3 junction structure, and the tandem solar cell may be constituted by the solar cell layer having the 3 junction structure. You may have one or more solar cell layers other than the solar cell layer of this 3 junction structure. For example, as described in claim 2, a Ge solar cell layer may be formed on the other surface of the Si solar cell layer, and a solar cell layer having an InGaP / (In) GaAs / Si / Ge 4 junction structure may be used.

上記のタンデム太陽電池の生産方法は、請求項３に記載するように、InGaP/(In)GaAs/Si３接合構造の太陽電池層を含むタンデム太陽電池の生産方法において、Ge基板上に(In)GaAs 太陽電池層，InGaP 太陽電池層の順でInGaP/(In)GaAs太陽電池層を形成する工程と、前記Ge基板を、一部を残して(In)GaAs 太陽電池層から除去し、Ge介在層を形成する工程と、前記Ge介在層にSi太陽電池層を接着する工程とを有する方法である。
また、請求項４に記載するように、前記Si太陽電池層の他面にGe太陽電池層を配置して、InGaP/(In)GaAs/Si/Ge４接合構造の太陽電池層を形成してもよい。
前記Ge介在層と前記Si太陽電池層との接着は、請求項５に記載するように超音波融着法を用いてもよい。 According to a third aspect of the present invention, there is provided a production method of a tandem solar cell including a solar cell layer having an InGaP / (In) GaAs / Si3 junction structure on a Ge substrate. A step of forming an InGaP / (In) GaAs solar cell layer in the order of a GaAs solar cell layer and an InGaP solar cell layer, and removing the Ge substrate from the (In) GaAs solar cell layer, leaving a part of the Ge substrate. A layer forming step and a step of adhering a Si solar cell layer to the Ge intervening layer.
According to a fourth aspect of the present invention, a solar cell layer having an InGaP / (In) GaAs / Si / Ge4 junction structure may be formed by disposing a Ge solar cell layer on the other surface of the Si solar cell layer. Good.
The adhesion between the Ge intervening layer and the Si solar cell layer may use an ultrasonic fusion method as described in claim 5.

本発明のタンデム太陽電池は、Ge介在層が補強材となるため、タンデム太陽電池の生産工程においてInGaP/GaAs２接合タンデム太陽電池にクラック等が発生しにくいという利点がある。
また、本発明の方法では、InGaP/GaAs/Ge３接合タンデム太陽電池よりも高い開放端電圧と高い変換効率のInGaP/(In)GaAs/Si３接合タンデム太陽電池を、簡単，高効率かつ低コストで生産することができる。特に、InGaP/(In)GaAsを結晶成長させる際に用いたGe基板の一部を利用することで、さらに生産性とコスト性を高めることができる。 The tandem solar cell of the present invention has an advantage that cracks and the like are hardly generated in the InGaP / GaAs two-junction tandem solar cell in the production process of the tandem solar cell because the Ge intervening layer serves as a reinforcing material.
In the method of the present invention, an InGaP / (In) GaAs / Si3 junction tandem solar cell having a higher open-circuit voltage and higher conversion efficiency than that of an InGaP / GaAs / Ge3 junction tandem solar cell is simple, high efficiency and low cost. Can be produced. In particular, by using a part of the Ge substrate used for crystal growth of InGaP / (In) GaAs, productivity and cost can be further improved.

以下、本発明の好適な実施形態を、図面を参照しながら詳細に説明する。
図１（ａ）は、本発明のタンデム太陽電池の第一の実施形態にかかり、その構成を説明する概略図、図１（ｂ）は図１（ａ）のタンデム太陽電池のI-I方向矢視図である。
この実施形態のタンデム太陽電池は、Ge基板の上にエピタキシャル成長させて形成されたInGaP太陽電池層４及び GaAs太陽電池層２と、GaAs太陽電池層２に部分的なGe介在層１ａを介して接着されたSi太陽電池層１３とから構成されたInGaP/GaAs/Si３接合タンデム太陽電池である。 DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
1A is a schematic diagram illustrating the configuration of a tandem solar cell according to a first embodiment of the present invention, and FIG. 1B is a view in the direction II of the tandem solar cell of FIG. 1A. FIG.
The tandem solar cell of this embodiment is bonded to an InGaP solar cell layer 4 and a GaAs solar cell layer 2 formed by epitaxial growth on a Ge substrate, and a partial Ge intervening layer 1a to the GaAs solar cell layer 2. An InGaP / GaAs / Si 3 junction tandem solar cell composed of the Si solar cell layer 13 formed.

InGaP太陽電池層４とGaAs太陽電池層２との間にはトンネル層３が形成され、InGaP太陽電池層４の上面には、n-GaAsキャップ層５，電極６，反射防止膜７が形成されるとともにリード線８が電極６に接続された上で、接着剤１０によりガラス板９が貼着される。また、GaAs太陽電池層２の下面には、電極１１及び反射防止膜１２が形成され、Si太陽電池層１３の上面には、電極１４及び反射防止膜１５が形成される。
Ge介在層１ａは、InGaP太陽電池層４及び GaAs太陽電池層２をエピタキシャル成長させたGe基板の一部を残存させてInGaP/ GaAs太陽電池層から除去したものである。残存させるGe介在層１ａの割合は、InGaP/(In)GaAs/Si３接合構造のタンデム太陽電池を生産するに当たり、破損等の不都合を生じない範囲内で、また、製品としてのタンデム太陽電池の構造的強度を十分に保てる範囲内で、 Si太陽電池層１３への入射光量を最大するように、GaAs太陽電池層２及びSi太陽電池層１３に比して可能な限り小さくする。
なお、Ge介在層１ａとGaAs太陽電池層２との間には、トンネル層は存在しない方がよい。 A tunnel layer 3 is formed between the InGaP solar cell layer 4 and the GaAs solar cell layer 2, and an n-GaAs cap layer 5, an electrode 6 and an antireflection film 7 are formed on the upper surface of the InGaP solar cell layer 4. In addition, after the lead wire 8 is connected to the electrode 6, the glass plate 9 is adhered by the adhesive 10. Further, an electrode 11 and an antireflection film 12 are formed on the lower surface of the GaAs solar cell layer 2, and an electrode 14 and an antireflection film 15 are formed on the upper surface of the Si solar cell layer 13.
The Ge intervening layer 1a is formed by removing a part of the Ge substrate on which the InGaP solar cell layer 4 and the GaAs solar cell layer 2 are epitaxially grown and removing them from the InGaP / GaAs solar cell layer. The ratio of the remaining Ge intervening layer 1a is within a range that does not cause inconvenience such as damage when producing a tandem solar cell having an InGaP / (In) GaAs / Si 3 junction structure, and the structure of the tandem solar cell as a product. In order to maximize the amount of light incident on the Si solar cell layer 13 within a range in which sufficient strength can be maintained, it is made as small as possible compared to the GaAs solar cell layer 2 and the Si solar cell layer 13.
It should be noted that there is no tunnel layer between the Ge intervening layer 1a and the GaAs solar cell layer 2.

図２及び図３は、第一の実施形態のタンデム太陽電池を生産する手順の一例を説明する概略図である。
図２（ａ）に示すように、まずp型Ge基板1を準備する。そして、ＭＯＣＶＤ法により、p型Ge基板１の上面に、p型InGaP裏面電界層、p型GaAsベース層，n型GaAsエミッタ一層、n型InGaP窓層から成るGaAs太陽電池層２を形成する。
次に、図２（ｂ）に示すように、ＭＯＣＶＤ法を用いて、GaAs太陽電池層２の上面にp-AIGaAs/n-InGaPトンネル接合層３を形成し、p -AlInP裏面電界層、p -InGaPベース層、n-InGaPエミッタ一層、 n-AlInP窓層から成るInGaP太陽電池層４を形成する。InGaP太陽電池層４には、さらにn-GaAsキャップ層５、電極６、反射防止膜７を形成する。 2 and 3 are schematic diagrams illustrating an example of a procedure for producing the tandem solar cell of the first embodiment.
As shown in FIG. 2A, a p-type Ge substrate 1 is first prepared. Then, a GaAs solar cell layer 2 including a p-type InGaP back surface field layer, a p-type GaAs base layer, an n-type GaAs emitter layer, and an n-type InGaP window layer is formed on the upper surface of the p-type Ge substrate 1 by MOCVD.
Next, as shown in FIG. 2B, a p-AIGaAs / n-InGaP tunnel junction layer 3 is formed on the upper surface of the GaAs solar cell layer 2 by MOCVD, and a p-AlInP back surface field layer, p An InGaP solar cell layer 4 including an -InGaP base layer, an n-InGaP emitter layer, and an n-AlInP window layer is formed. On the InGaP solar cell layer 4, an n-GaAs cap layer 5, an electrode 6 and an antireflection film 7 are further formed.

次に、図２（ｃ）に示すように、電極６にリード線８を接続した後、図２（ｄ）に示すように、InGaP太陽電池層４の上面にガラス板９を紫外線硬化型接着材１０により接着する。
この後、図３（ａ）に示すように、Ge基板１をGaAs太陽電池層２から一部を残して除去する。この除去は、例えば、残存させる部分（すなわちGe介在層１ａとなる部分）にマスクを形成し、過酸化水素水を用いてGe基板をエッチングして行う。このようにしてGe残存部（すなわちGe介在層１ａ）を形成する。Ge介在層１ａの下端には、図３（ｂ）に示すように、メッキ法又は蒸着法等によりアルミニウム，金，銀，プラチナ，ニッケル等の金属層１ｂを形成し、また、GaAs太陽電池層２の下面には、電極１１と反射防止膜１２とを形成する。なお、電極１１をGe介在層１ａにも接続することで、Ge介在層１ａをSi太陽電池層１３との接続部として利用することが可能である。 Next, as shown in FIG. 2 (c), after connecting the lead wire 8 to the electrode 6, as shown in FIG. 2 (d), the glass plate 9 is bonded to the upper surface of the InGaP solar cell layer 4 by ultraviolet curable bonding. Adhering with the material 10.
Thereafter, as shown in FIG. 3A, the Ge substrate 1 is removed from the GaAs solar cell layer 2 while leaving a part. This removal is performed, for example, by forming a mask in the remaining portion (that is, the portion that becomes the Ge intervening layer 1a) and etching the Ge substrate using hydrogen peroxide. In this way, the remaining Ge portion (that is, the Ge intervening layer 1a) is formed. As shown in FIG. 3B, a metal layer 1b such as aluminum, gold, silver, platinum, nickel, or the like is formed at the lower end of the Ge intervening layer 1a by a plating method or a vapor deposition method, and a GaAs solar cell layer. An electrode 11 and an antireflection film 12 are formed on the lower surface of 2. In addition, it is possible to utilize the Ge intervening layer 1a as a connection part with the Si solar cell layer 13 by connecting the electrode 11 also to the Ge intervening layer 1a.

最後に、図３（ｃ）に示すように、公知の方法で生産したn＋-p接合構造のSi太陽電池層１３の上に図２〜図３（ｂ）の手順で得られたモノリシック型InGaP/GaAs２接合タンデム太陽電池を載置する。Si太陽電池層１３には、電極１４と反射防止膜１５を形成するほか、Ge介在層１ａの金属層１ｂと接触する部分に、予め蒸着法等によりアルミニウム，金，銀，プラチナ，ニッケル等の金属層１３ａを形成しておく。そして、例えば超音波融着法により金属層１ｂ，１３ａを接着して、メカニカルスタック型のInGaP/GaAs/Si３接合タンデム太陽電池を得る。 Finally, as shown in FIG. 3C, the monolithic type obtained by the procedure of FIGS. 2 to 3B on the n + -p junction structure Si solar cell layer 13 produced by a known method. An InGaP / GaAs 2-junction tandem solar cell is mounted. In addition to forming the electrode 14 and the antireflection film 15 on the Si solar cell layer 13, a portion such as aluminum, gold, silver, platinum, nickel, or the like previously deposited on the portion of the Ge intervening layer 1 a in contact with the metal layer 1 b by vapor deposition or the like. A metal layer 13a is formed. Then, for example, the metal layers 1b and 13a are bonded by an ultrasonic fusion method to obtain a mechanical stack type InGaP / GaAs / Si3 junction tandem solar cell.

上記のようにして得られたInGaP/GaAs/Si３接合構造のタンデム太陽電池は、Si太陽電池層１３とGaA太陽電池層２との間にGe介在層１ａが存在しているので、衝撃に強く、そのためInGaP/GaAs/Si３接合構造のタンデム太陽電池を生産する過程においてInGaP/GaAs太陽電池層にクラック等が生じにくく、従って、歩留まりよく生産することができる。   The InGaP / GaAs / Si three-junction tandem solar cell obtained as described above is strong against impact because the Ge intervening layer 1a exists between the Si solar cell layer 13 and the GaA solar cell layer 2. Therefore, in the process of producing a tandem solar cell having an InGaP / GaAs / Si 3 junction structure, the InGaP / GaAs solar cell layer is hardly cracked, and therefore can be produced with a high yield.

図４は、本発明のタンデム太陽電池の第二の実施形態にかかり、その構成を説明する概略図である。
この実施形態のタンデム太陽電池は、InGaP/GaAs/Si３接合構造のタンデム太陽電池を構成するSi太陽電池層１３の他面にGe太陽電池層１８を形成したInGaP/(In)GaAs/Si/Ge４接合構造のタンデム太陽電池である。
このInGaP/(In)GaAs/Si/Ge４接合構造のタンデム太陽電池の生産の手順は、第一の実施形態で得られたInGaP/(In)GaAs/Si 太陽電池層を構成するSi太陽電池層１３の下面に電極１７と反射防止膜１６を形成した後、このSi太陽電池層１３の下面に公知のn＋-p接合構造のGe太陽電池層１８を配置する。Ge太陽電池層１８の上面には電極１９と反射防止膜２０を形成しておく。
Si太陽電池層１３に対するGe太陽電池層１８の接着は、金属層１ａ及び金属層１３ａと同様の金属層１３ｂ，１８ａをSi太陽電池層１３の下面及びGe太陽電池層１８の上面に形成し、両者を接触させた状態で、例えば超音波融着法により両金属層１３ｂ，１８ａを溶融することで行うことができる。 FIG. 4 is a schematic diagram illustrating a configuration of a tandem solar cell according to a second embodiment of the present invention.
The tandem solar cell of this embodiment is an InGaP / (In) GaAs / Si / Ge4 in which a Ge solar cell layer 18 is formed on the other surface of the Si solar cell layer 13 constituting the tandem solar cell having an InGaP / GaAs / Si3 junction structure. This is a tandem solar cell with a junction structure.
This InGaP / (In) GaAs / Si / Ge 4-junction structure tandem solar cell production procedure is the same as the Si solar cell layer constituting the InGaP / (In) GaAs / Si solar cell layer obtained in the first embodiment. After forming the electrode 17 and the antireflection film 16 on the lower surface of 13, a Ge solar cell layer 18 having a known n + -p junction structure is disposed on the lower surface of the Si solar cell layer 13. An electrode 19 and an antireflection film 20 are formed on the upper surface of the Ge solar cell layer 18.
The adhesion of the Ge solar cell layer 18 to the Si solar cell layer 13 is performed by forming metal layers 13b and 18a similar to the metal layer 1a and the metal layer 13a on the lower surface of the Si solar cell layer 13 and the upper surface of the Ge solar cell layer 18. In a state where both are brought into contact with each other, for example, the both metal layers 13b and 18a can be melted by an ultrasonic fusion method.

［実施例１］
InGaP/GaAs/Si３接合構造のタンデム太陽電池において、厚さ３００μｍ，幅１ｍｍのGe介在層１ａを介在させた。
図５は、第一の実施形態のInGaP/GaAs/Si３接合構造のタンデム太陽電池における出力特性を示すグラフで、ＪＩＳで規定するＡＭ（Air Mass（エアマス））１．５、 １００mW/cm2の擬似太陽光照射下での電流密度−電圧特性を示すものである。ここで、本発明のInGaP/GaAs/Si３接合タンデム太陽電池の特性を実線で示し、従来のInGaP/GaAs/Ge３接合構造のタンデム太陽電池を点線で示している。
この結果から明らかなように、Ge太陽電池層に代えてSi太陽電池層を使用することにより、発生電流はほとんど変化することなしに開放端電圧を０．５Ｖ上昇させることができ、変換効率として、従来のInGaP/GaAs/Ge３接合タンデム太陽電池の２３％に対して、本発明のInGaP/GaAs/Si３接合構造のタンデム太陽電池では２８％の高効率を達成することができた。
［実施例２］
第二の実施形態で得られたInGaP/GaAs/Si/Ge４接合構造のタンデム太陽電池を、実施例１と同じ擬似太陽光照射下にさらし、電流密度一電圧特性を調べた。その結果、３．０５Ｖの開放端電圧と３０％の変換効率を得た。 [Example 1]
In a tandem solar cell having an InGaP / GaAs / Si 3 junction structure, a Ge intervening layer 1a having a thickness of 300 μm and a width of 1 mm was interposed.
FIG. 5 is a graph showing output characteristics of the tandem solar cell having the InGaP / GaAs / Si 3 junction structure according to the first embodiment. AM (Air Mass) defined by JIS 1.5, 100 mW / cm 2 The current density-voltage characteristic under pseudo-sunlight irradiation is shown. Here, the characteristics of the InGaP / GaAs / Si3 junction tandem solar cell of the present invention are shown by solid lines, and the conventional tandem solar cell of the InGaP / GaAs / Ge3 junction structure is shown by dotted lines.
As is apparent from this result, by using the Si solar cell layer instead of the Ge solar cell layer, the open-circuit voltage can be increased by 0.5 V with almost no change in the generated current, and the conversion efficiency is increased. As compared with 23% of the conventional InGaP / GaAs / Ge 3 junction tandem solar cell, the tandem solar cell of the InGaP / GaAs / Si 3 junction structure of the present invention was able to achieve a high efficiency of 28%.
[Example 2]
The InGaP / GaAs / Si / Ge 4-junction tandem solar cell obtained in the second embodiment was exposed to the same pseudo-sunlight irradiation as in Example 1, and the current density-voltage characteristics were examined. As a result, an open-circuit voltage of 3.05 V and a conversion efficiency of 30% were obtained.

本発明の好適な実施形態について説明したが、本発明は上記の実施形態に限定されない。
例えば、上記の説明では、GaAs太陽電池層として説明したが、InGaAs太陽電池層であってもよい。
また、第二の実施形態では、InGaP/GaAs/Si太陽電池層にGe太陽電池層１８を設けた場合についてのみ説明したが、InGaP/GaAs/Si太陽電池層に追加する太陽電池層はGe太陽電池層１８以外であってもよい。
さらに、Ge介在層１ａは、図１（ｂ）に示すような断面形状には限られない。
また、先の実施形態の説明では、Ge基板１上にGaAs太陽電池層，InGaP太陽電池層の順でInGaP/(In)GaAs太陽電池層を形成した後に一部を残してGe基板１を除去することでGe介在層１ａを形成しているが、本発明のタンデム太陽電池を形成する方法はこれに限定されない。 Although preferred embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments.
For example, in the above description, the GaAs solar cell layer is described, but an InGaAs solar cell layer may be used.
In the second embodiment, only the case where the Ge solar cell layer 18 is provided in the InGaP / GaAs / Si solar cell layer has been described. However, the solar cell layer added to the InGaP / GaAs / Si solar cell layer is a Ge solar cell. It may be other than the battery layer 18.
Furthermore, the Ge intervening layer 1a is not limited to the cross-sectional shape as shown in FIG.
In the description of the previous embodiment, after the InGaP / (In) GaAs solar cell layer is formed on the Ge substrate 1 in this order, the GaAs solar cell layer and the InGaP solar cell layer are removed, and the Ge substrate 1 is removed while leaving a part. Thus, the Ge intervening layer 1a is formed, but the method of forming the tandem solar cell of the present invention is not limited to this.

本発明は、InGaP/GaAs/Si３接合構造の太陽電池層を有するタンデム太陽電池に広範に適用が可能で、InGaP/GaAs/Si３接合構造に限らず、一つ又は複数の他の太陽電池層を有する４層以上の接合構造のタンデム太陽電池にも広範に適用が可能である。   The present invention can be widely applied to a tandem solar cell having a solar cell layer having an InGaP / GaAs / Si3 junction structure, and is not limited to an InGaP / GaAs / Si3 junction structure, but includes one or more other solar cell layers. The present invention can be widely applied to tandem solar cells having a junction structure of four or more layers.

図１（ａ）は、本発明のタンデム太陽電池の第一の実施形態にかかり、その構成を説明する概略図、図１（ｂ）は図１（ａ）のタンデム太陽電池のI-I方向矢視図である。1A is a schematic diagram illustrating the configuration of a tandem solar cell according to a first embodiment of the present invention, and FIG. 1B is a view in the direction II of the tandem solar cell of FIG. 1A. FIG. 第一の実施形態のタンデム太陽電池を生産する手順を説明する概略図である。It is the schematic explaining the procedure which produces the tandem solar cell of 1st embodiment. 第一の実施形態のタンデム太陽電池を生産する手順を説明する概略図である。It is the schematic explaining the procedure which produces the tandem solar cell of 1st embodiment. 本発明のタンデム太陽電池の第二の実施形態にかかり、その構成を説明する概略図である。It is the schematic concerning 2nd embodiment of the tandem solar cell of this invention, and explaining the structure. 第一の実施形態のInGaP/GaAs/Si３接合構造のタンデム太陽電池における出力特性を示すグラフである。It is a graph which shows the output characteristic in the tandem solar cell of the InGaP / GaAs / Si3 junction structure of 1st embodiment.

１：Ge基板
１ａ：Ge介在層
２：GaAs太陽電池層
３：トンネル接合層
４：InGaP太陽電池層
５：n-GaAsキャップ層
６：電極
７：反射防止膜
８：リード線
９：ガラス板
１０：接着剤
１１：電極
１２：反射防止膜
１３：Si太陽電池層
１４：電極
１６：反射防止膜
１７：電極
１５：反射防止膜
１８：Ge太陽電池層
1: Ge substrate 1a: Ge intervening layer 2: GaAs solar cell layer 3: Tunnel junction layer 4: InGaP solar cell layer 5: n-GaAs cap layer 6: Electrode 7: Antireflection film 8: Lead wire 9: Glass plate 10 : Adhesive 11: Electrode 12: Antireflection film 13: Si solar cell layer 14: Electrode 16: Antireflection film 17: Electrode 15: Antireflection film 18: Ge solar cell layer

Claims (5)

InGaP/(In)GaAs/Si３接合構造の太陽電池層を含むタンデム太陽電池において、
(In)GaAs太陽電池層とSi太陽電池層とが、前記(In)GaAs太陽電池層の一部に形成されたGe介在層を介して接着されていることを特徴とするタンデム太陽電池。 In a tandem solar cell including a solar cell layer of InGaP / (In) GaAs / Si 3 junction structure,
A tandem solar cell, wherein an (In) GaAs solar cell layer and a Si solar cell layer are bonded via a Ge intervening layer formed in a part of the (In) GaAs solar cell layer. 請求項１に記載のタンデム太陽電池において、前記Si太陽電池層の他面にGe太陽電池層を形成し、InGaP/(In)GaAs/Si/Ge４接合構造の太陽電池層を含むことを特徴とするタンデム太陽電池。 2. The tandem solar cell according to claim 1, wherein a Ge solar cell layer is formed on the other surface of the Si solar cell layer, and includes a solar cell layer having an InGaP / (In) GaAs / Si / Ge 4 junction structure. Tandem solar cell to do. InGaP/(In)GaAs/Si３接合構造の太陽電池層を含むタンデム太陽電池の生産方法において、
Ge基板上に(In)GaAs 太陽電池層，InGaP 太陽電池層の順でInGaP/(In)GaAs太陽電池層を形成する工程と、
前記Ge基板を、一部を残して(In)GaAs 太陽電池層から除去し、Ge介在層を形成する工程と、
前記Ge介在層にSi太陽電池層を接着する工程と、
を有することを特徴とするタンデム太陽電池の生産方法。 In a method for producing a tandem solar cell including a solar cell layer having an InGaP / (In) GaAs / Si 3 junction structure,
Forming an InGaP / (In) GaAs solar cell layer on a Ge substrate in the order of an (In) GaAs solar cell layer and an InGaP solar cell layer;
Removing the Ge substrate from the (In) GaAs solar cell layer, leaving a portion, and forming a Ge intervening layer;
Adhering a Si solar cell layer to the Ge intervening layer;
A method for producing a tandem solar cell, comprising: 前記Si太陽電池層の他面にGe太陽電池層を配置して、InGaP/(In)GaAs/Si/Ge４接合構造の太陽電池層を形成することを特徴とする請求項３に記載のタンデム太陽電池の生産方法。 The tandem solar according to claim 3, wherein a Ge solar cell layer is disposed on the other surface of the Si solar cell layer to form a solar cell layer having an InGaP / (In) GaAs / Si / Ge 4-junction structure. Battery production method. 前記Ge介在層と前記Si太陽電池層とを超音波融着法により接着することを特徴とする請求項３又は４に記載のタンデム太陽電池の生産方法。 The method for producing a tandem solar cell according to claim 3 or 4, wherein the Ge intervening layer and the Si solar cell layer are bonded by an ultrasonic fusion method.
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