JP2002151715A - Thin-film solar cell - Google Patents
Thin-film solar cellInfo
- Publication number
- JP2002151715A JP2002151715A JP2000339960A JP2000339960A JP2002151715A JP 2002151715 A JP2002151715 A JP 2002151715A JP 2000339960 A JP2000339960 A JP 2000339960A JP 2000339960 A JP2000339960 A JP 2000339960A JP 2002151715 A JP2002151715 A JP 2002151715A
- Authority
- JP
- Japan
- Prior art keywords
- semiconductor layer
- substrate
- crystalline semiconductor
- solar cell
- thin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/545—Microcrystalline silicon PV cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/546—Polycrystalline silicon PV cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/548—Amorphous silicon PV cells
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は高い光電変換効率を
有する薄膜太陽電池に関する。The present invention relates to a thin-film solar cell having high photoelectric conversion efficiency.
【０００２】[0002]
【従来の技術】将来の需給が懸念され、かつ地球温暖化
現象の原因となる二酸化炭素排出の問題がある石油等の
化石燃料の代替エネルギー源として太陽電池が注目され
ている。2. Description of the Related Art Solar cells are attracting attention as an alternative energy source for fossil fuels such as petroleum, which is concerned about future supply and demand and has a problem of carbon dioxide emission causing global warming.
【０００３】この太陽電池は光エネルギーを電力に変換
する光電変換層にｐｎ接合を用いており、このｐｎ接合
を構成する半導体として一般的にはシリコンが最もよく
用いられている。光電変換効率の点からは単結晶シリコ
ンを用いることが好ましいが原料供給や大面積化、低コ
スト化の問題が有る。In this solar cell, a pn junction is used for a photoelectric conversion layer for converting light energy into electric power, and silicon is generally most often used as a semiconductor constituting the pn junction. From the viewpoint of photoelectric conversion efficiency, it is preferable to use single crystal silicon, but there are problems of raw material supply, enlargement of area, and cost reduction.
【０００４】一方、大面積化および低コスト化を実現す
るのに有利な材料としてアモルファスシリコンを光電変
換層とした薄膜太陽電池も実用化されているが、その光
電変換効率は単結晶シリコン太陽電池と比較して劣る。
さらにアモルファスシリコンには光を照射するにつれて
膜中の欠陥密度が増加するＳｔａｅｂｌｅｒ−Ｗｒｏｎ
ｓｋｉ効果と呼ばれる現象が生じるため、アモルファス
シリコン太陽電池には光電変換効率の経時劣化という問
題が避けられない。On the other hand, a thin film solar cell using amorphous silicon as a photoelectric conversion layer has been put to practical use as a material advantageous for realizing a large area and a low cost. Inferior to.
Further, the amorphous silicon has a defect density in the film which increases as the light is irradiated. Staebler-Wron
Since a phenomenon called a ski effect occurs, an amorphous silicon solar cell inevitably suffers from a problem of deterioration of photoelectric conversion efficiency with time.
【０００５】そこで近年、単結晶シリコン太陽電池レベ
ルの高くて安定な光電変換効率と、アモルファスシリコ
ン太陽電池レベルの大面積化、低コスト化を兼ね備えた
太陽電池を実現するために、結晶質シリコンの光電変換
層への使用が検討されている。特にアモルファスシリコ
ンの場合と同様の化学的気相成長法（以下、ＣＶＤ法と
する）による薄膜形成技術を用いて、結晶質シリコン薄
膜を形成した薄膜太陽電池（以下、結晶質シリコン薄膜
太陽電池とする）が注目されている。In recent years, in order to realize a solar cell having both high and stable photoelectric conversion efficiency at the level of a single-crystal silicon solar cell and large area and low cost at the level of an amorphous silicon solar cell, crystalline silicon has been developed. Use for a photoelectric conversion layer is being studied. In particular, a thin film solar cell (hereinafter, referred to as a crystalline silicon thin film solar cell) in which a crystalline silicon thin film is formed using a thin film forming technique by a chemical vapor deposition method (hereinafter, referred to as a CVD method) similar to that of amorphous silicon. Do) is attracting attention.
【０００６】ところが現在までのところ、精力的な研究
開発が行われているにも関わらず、上記の方法により作
製された結晶質シリコン薄膜太陽電池の光電変換効率
は、アモルファスシリコン太陽電池の光電変換効率と比
較して同等レベルでしかない。その大きな要因として、
得られた結晶質シリコン層中の欠陥密度が高いことが挙
げられる。欠陥密度を低減させるには、結晶粒径を増大
させることが有効である。また膜厚方向にキャリアが流
れる構造となる太陽電池においては、多結晶粒の存在形
態としては膜厚方向を横切るような粒界が存在しない構
造、すなわち膜厚方向に対し結晶粒が柱状に成長した構
造が望ましく、膜厚方向に対し結晶方位が揃っている場
合にそのような構造が得られやすい。[0006] However, the photoelectric conversion efficiency of the crystalline silicon thin-film solar cell manufactured by the above-described method has not been improved despite the intensive research and development. Only at the same level as efficiency. The major factor is that
The defect density in the obtained crystalline silicon layer is high. In order to reduce the defect density, it is effective to increase the crystal grain size. In a solar cell having a structure in which carriers flow in the film thickness direction, the polycrystal grains are present in a structure in which there is no grain boundary crossing the film thickness direction, that is, crystal grains grow in a columnar shape in the film thickness direction. Such a structure is easily obtained when the crystal orientation is aligned with the film thickness direction.
【０００７】結晶粒径の大きな結晶質シリコン薄膜を得
る試みは様々な手法で行われている。例えば、基板上に
ＣＶＤ法等により形成した非晶質シリコン薄膜にレーザ
ー光を照射して溶融させた後、凝固により多結晶シリコ
ン薄膜を得る、いわゆるレーザーアニール法が知られて
いる。また非晶質シリコン膜の一部分にリンあるいはボ
ロン等をドーピングすることにより、選択的に固相成長
による結晶化を開始させる、いわゆるパーシャルドーピ
ング法が知られている。ところが、上述のような方法に
は高い装置コストが必要であったり、数十時間もの熱処
理時間を要する等、実用に供する上で困難な問題が存在
する。[0007] Various attempts have been made to obtain a crystalline silicon thin film having a large crystal grain size. For example, a so-called laser annealing method is known in which an amorphous silicon thin film formed on a substrate by a CVD method or the like is irradiated with a laser beam and melted, and then a polycrystalline silicon thin film is obtained by solidification. Also, a so-called partial doping method is known in which crystallization by solid phase growth is selectively started by doping a part of an amorphous silicon film with phosphorus or boron. However, the above-mentioned methods have difficult problems in practical use, such as high equipment cost and heat treatment time of several tens of hours.
【０００８】一方、膜厚方向に対し結晶方位が揃ってい
る結晶シリコン薄膜を得る試みも様々な手法で行われて
いる。例えば、特開平７−２４０５３１号公報には、半
導体薄膜の堆積中あるいは堆積後に不活性ガスビームを
複数の方向から照射することを特徴とする太陽電池およ
び多層薄膜の製造方法が示されている。該方法による
と、チャネリングビームとなる不活性ガスビームの照射
方向に結晶シリコンの最稠密方向である＜１１１＞方向
が揃ったシリコン薄膜が得られるとしている。また特開
平１１−２７８９８８号公報には、シリコン膜堆積中に
基板に垂直な方向からＳｉＨ3ビームを照射し、基板に
平行な方向からＨビームを照射することを特徴とする単
結晶薄膜の製造方法が示されている。該方法によると、
分子量が大きいので非チャネリングビームとなるＳｉＨ
3ビームの照射方向である基板表面に垂直な方向に結晶
シリコンの最稠密方向である＜１１１＞方向が揃い、分
子量が小さいのでチャネリングビームとなるＨビームの
照射方向に結晶シリコンの＜１１０＞方向が揃うことに
より、単結晶のシリコン薄膜が得られるとしている。On the other hand, various attempts have been made to obtain a crystalline silicon thin film in which the crystal orientation is aligned with the film thickness direction. For example, Japanese Patent Application Laid-Open No. Hei 7-240531 discloses a method of manufacturing a solar cell and a multilayer thin film, wherein an inert gas beam is irradiated from a plurality of directions during or after the deposition of a semiconductor thin film. According to this method, a silicon thin film in which the <111> direction, which is the densest direction of crystalline silicon, is aligned with the irradiation direction of an inert gas beam serving as a channeling beam is described. Japanese Patent Application Laid-Open No. 11-278988 discloses a method for manufacturing a single crystal thin film, which comprises irradiating a SiH 3 beam from a direction perpendicular to a substrate and irradiating an H beam from a direction parallel to the substrate during deposition of a silicon film. The method is shown. According to the method,
SiH which is a non-channeling beam due to its high molecular weight
The <111> direction, which is the densest direction of crystalline silicon, is aligned with the direction perpendicular to the substrate surface, which is the three- beam irradiation direction, and the <110> direction of crystalline silicon, in the H-beam irradiation direction, which is a channeling beam because of its low molecular weight That a single-crystal silicon thin film can be obtained.
【０００９】[0009]
【発明が解決しようとする課題】結晶質シリコン薄膜太
陽電池が注目されているのは、素子構造がアモルファス
シリコン太陽電池と同様のものとすることができるの
で、素子を構成する部材や製造プロセスの大部分を流用
できると考えられるからである。ところが、Ｈ．Ｙａｍ
ａｍｏｔｏ ｅｔ ａｌ，ＰＶＳＥＣ−１１，Ｓａｐｐ
ｏｒｏ，Ｊａｐａｎ，１９９９において、ガラス上に酸
化錫を積層した表面凹凸によるテクスチャー構造を有す
る基板上にプラズマＣＶＤ法により微結晶シリコンを形
成した場合、図２に示すように、個々の凹凸表面に垂直
な方向にシリコンの結晶粒が優先的に成長し、異なる凹
凸表面から成長した互いに結晶方位の異なる結晶粒同士
がぶつかることで多量の欠陥が発生することが報告され
た。非晶質半導体層ではなく結晶質半導体層であること
に起因するこのような欠陥は、キャリアの再結合中心と
なるため光電変換効率を著しく劣化させるので、極力排
除されなければならない。Ｈ．Ｙａｍａｍｏｔｏらは、
表面凹凸を有する酸化錫の上にさらに酸化亜鉛を厚く積
層することで凹凸大きさを小さくした場合、酸化錫の場
合と同様に酸化亜鉛の表面に垂直な方向にシリコン結晶
粒が成長し、異なる凹凸表面から成長した結晶粒同士は
ぶつかるがそれらの方位差が小さいため、発生する欠陥
が少なくなることも同時に報告した。しかるに、結晶質
半導体層中の欠陥を低減するためには基板の表面凹凸を
できるだけ小さくすればよいのは明らかである。The crystalline silicon thin-film solar cell has attracted attention because its element structure can be similar to that of an amorphous silicon solar cell. This is because it is thought that most can be diverted. However, H. Yama
amoto et al, PVSEC-11, Sapp
According to Oro, Japan, 1999, when microcrystalline silicon is formed by a plasma CVD method on a substrate having a texture structure with surface irregularities in which tin oxide is laminated on glass, as shown in FIG. It has been reported that silicon crystal grains grow preferentially in various directions, and a large number of defects occur when crystal grains having different crystal orientations grown from different uneven surfaces collide with each other. Such a defect caused by a crystalline semiconductor layer instead of an amorphous semiconductor layer becomes a recombination center of carriers and significantly deteriorates photoelectric conversion efficiency. Therefore, such a defect must be eliminated as much as possible. H. Yamamoto et al.
If the size of the irregularities is reduced by further laminating zinc oxide on tin oxide having surface irregularities, silicon crystal grains grow in the direction perpendicular to the surface of zinc oxide, similar to the case of tin oxide, and differ It has also been reported that the crystal grains grown from the uneven surface collide with each other, but the difference in their orientation is small, so that the generated defects are reduced. However, it is clear that the surface irregularities of the substrate may be reduced as much as possible in order to reduce defects in the crystalline semiconductor layer.
【００１０】しかしながら、特許第１６８１１８３号公
報に示されている通り、表面凹凸を有する透明導電膜に
は，光の乱反射を生じさせ、シリコン膜中における光路
長を大きくするので光吸収により発生する電流値を増大
させる、いわゆる光閉込効果という重要な機能がある。
さらに光閉込効果は光電変換効率の向上により光電変換
層を薄くできるので、製膜工程を短時間化できるという
利点も産み出す。このことは光吸収特性の違いからアモ
ルファスシリコン太陽電池の数倍もの光電変換層厚さを
要求される結晶質シリコン薄膜太陽電池において、スル
ープットの大幅な向上をもたらすことになる。したがっ
て、表面凹凸をなくす、あるいは小さくすることは回避
すべきである。However, as shown in Japanese Patent No. 1681183, a transparent conductive film having surface irregularities causes irregular reflection of light and increases the optical path length in the silicon film, so that a current generated by light absorption is generated. There is an important function of increasing the value, the so-called optical confinement effect.
Further, the light confinement effect can produce a thin film forming process in a short time because the photoelectric conversion layer can be made thinner by improving the photoelectric conversion efficiency. This leads to a significant improvement in throughput in a crystalline silicon thin-film solar cell that requires a photoelectric conversion layer thickness several times that of an amorphous silicon solar cell due to differences in light absorption characteristics. Therefore, eliminating or reducing surface irregularities should be avoided.
【００１１】ところが現状のところ、結晶質シリコン薄
膜太陽電池の高効率化を図る上で重要な要素である、結
晶質シリコン薄膜中の欠陥密度低減と凹凸表面による光
閉込効果とは両立させることが非常に困難であり、解決
されていない。例えば、先述した特開平７−２４０５３
１号公報または特開平１１−２７８９８８号公報に示さ
れている結晶シリコン薄膜の製造方法を用いることで膜
中欠陥密度の小さいシリコン薄膜が作製できるが、シリ
コン薄膜を形成する基板が実質上平坦であるため、光閉
込効果を発現することができないので高効率化には限界
があることが明らかである。However, at present, it is important to achieve both the reduction of the defect density in the crystalline silicon thin film and the light confinement effect by the uneven surface, which are important factors for increasing the efficiency of the crystalline silicon thin film solar cell. Is very difficult and has not been solved. For example, as described in Japanese Patent Laid-Open No. 7-24053,
Although a silicon thin film having a small defect density in the film can be manufactured by using the method for manufacturing a crystalline silicon thin film disclosed in Japanese Patent Application Laid-Open No. 11-278988 or Japanese Patent Application Laid-Open No. 11-278988, the substrate on which the silicon thin film is formed is substantially flat. Because of this, it is apparent that the light confinement effect cannot be exhibited, so that there is a limit to high efficiency.
【００１２】それから、特開平１０−１５０２０９号公
報には、基板の法線方向と柱状結晶粒の長手方向あるい
は凹凸表面の法線方向との関係がある範囲内に規定され
ていることを特徴とする光電変換素子が開示されている
が、基板の法線方向と柱状結晶粒の長手方向が小さくな
い傾きを持つ限りは前述した欠陥の発生は不可避であ
る。さらに、特開平１０−１１７００６号公報、特開平
１０−２９４４８１号公報、特開平１１−２１４７２８
号公報、特開平１１−２６６０２７号公報、特開２００
０−５８８９２号公報には、表面を凹凸化した裏面電極
上に多結晶シリコン層から成る光電変換層を有する下部
光電変換素子を形成しており、該多結晶シリコン層が基
板表面に平行な（１１０）の優先結晶配向面を有する薄
膜太陽電池が示されているが、凹凸形状を有する裏面電
極表面近傍での多結晶シリコン層形成にあたっては、前
述した多結晶シリコンの成長挙動について全く考慮され
ていないため、欠陥の発生が避けられないのは明らかで
ある。Japanese Patent Application Laid-Open No. 10-150209 is characterized in that the relationship between the normal direction of the substrate and the longitudinal direction of the columnar crystal grains or the normal direction of the uneven surface is defined within a certain range. However, as long as the normal direction of the substrate and the longitudinal direction of the columnar crystal grains have an inclination that is not small, occurrence of the above-described defect is inevitable. Further, JP-A-10-117006, JP-A-10-294481, and JP-A-11-214728
JP, JP-A-11-266027, JP-A-200
In JP-A-58892, a lower photoelectric conversion element having a photoelectric conversion layer made of a polycrystalline silicon layer is formed on a back electrode having a roughened surface, and the polycrystalline silicon layer is parallel to the substrate surface ( Although a thin-film solar cell having a preferred crystal orientation plane of (110) is shown, when forming a polycrystalline silicon layer near the surface of a back electrode having an uneven shape, the above-described growth behavior of polycrystalline silicon is completely considered. Obviously, the absence of defects will inevitably lead to defects.
【００１３】本発明の目的は、十分な光閉込効果を有し
つつ、欠陥密度の増大が抑制された結晶質半導体層を有
する、高効率な薄膜太陽電池を提供することにある。An object of the present invention is to provide a highly efficient thin-film solar cell having a crystalline semiconductor layer having a sufficient light confinement effect and a suppressed increase in defect density.
【００１４】[0014]
【課題を解決するための手段】本発明による薄膜太陽電
池は、基板と、基板上に順に積層された第１導電型結晶
質半導体層、真性結晶質半導体層および第２導電型半導
体層からなる光電変換素子構造とを備える。本発明にお
いて、光電変換素子構造を支持する基板の表面は、凹凸
間隔Ｌに対する凹凸大きさＲの比Ｒ／Ｌが０．１〜１．
５の範囲にあるような凹凸によるテクスチャー構造を有
している。本発明において、第１導電型結晶質半導体層
および真性結晶質半導体層は、基板に垂直な方向に柱状
に成長している結晶粒により主として構成されている。A thin-film solar cell according to the present invention comprises a substrate, a first conductive type crystalline semiconductor layer, an intrinsic crystalline semiconductor layer and a second conductive type semiconductor layer which are sequentially laminated on the substrate. A photoelectric conversion element structure. In the present invention, the ratio R / L of the unevenness size R to the unevenness interval L on the surface of the substrate supporting the photoelectric conversion element structure is 0.1 to 1.
It has a texture structure with irregularities in the range of 5. In the present invention, the first-conductivity-type crystalline semiconductor layer and the intrinsic crystalline semiconductor layer are mainly constituted by crystal grains growing in a columnar direction in a direction perpendicular to the substrate.
【００１５】本発明において、第１導電型結晶質半導体
層は１ｎｍ以上２００ｎｍ未満の厚みを有することが好
ましい。また、基板の表面から高さ２００ｎｍまでの部
分において、基板に垂直な方向に柱状に成長している結
晶粒は、当該部分における結晶粒全体の少なくとも５０
％以上を占め、かつ基板に垂直な方向に１００ｎｍ以上
の長さを有することが好ましい。In the present invention, the first conductivity type crystalline semiconductor layer preferably has a thickness of 1 nm or more and less than 200 nm. Further, in a portion having a height of 200 nm from the surface of the substrate, crystal grains growing in a columnar shape in a direction perpendicular to the substrate are at least 50% of the total crystal grains in the portion.
%, And has a length of 100 nm or more in a direction perpendicular to the substrate.
【００１６】本発明において、第１導電型結晶質半導体
層は１ｎｍ以上１００ｎｍ以下の厚みを有することが好
ましい。In the present invention, the first conductive type crystalline semiconductor layer preferably has a thickness of 1 nm or more and 100 nm or less.
【００１７】本発明において、基板は、主として酸化亜
鉛からなる透明電極部を表面部として有するものである
ことが好ましい。In the present invention, the substrate preferably has a transparent electrode portion mainly composed of zinc oxide as a surface portion.
【００１８】本発明において、第１導電型結晶質半導体
層および真性結晶質半導体層は、主としてシリコンから
成ることが好ましく、第１導電型結晶質半導体層および
真性結晶質半導体層において基板に平行に配向する結晶
面は主として（１１０）であることが好ましい。In the present invention, the first conductive type crystalline semiconductor layer and the intrinsic crystalline semiconductor layer are preferably mainly composed of silicon, and the first conductive type crystalline semiconductor layer and the intrinsic crystalline semiconductor layer are parallel to the substrate. The crystal plane to be oriented is preferably mainly (110).
【００１９】本発明において、主としてシリコンから成
る真性結晶質半導体層について得られる、（２２０）面
のＸ線回折ピークの積分強度Ｉ220と（１１１）面のＸ
線回折ピークの積分強度Ｉ111との比Ｉ220／Ｉ111が３
以上であることが好ましい。In the present invention, the integrated intensity I 220 of the (220) plane X-ray diffraction peak and the X intensity of the (111) plane obtained for an intrinsic crystalline semiconductor layer mainly composed of silicon are obtained.
The ratio of I 220 / I 111 to the integrated intensity I 111 of the X-ray diffraction peak is 3
It is preferable that it is above.
【００２０】本発明において、主としてシリコンから成
る第１導電型結晶質半導体層はホウ素を不純物として含
有することが好ましい。In the present invention, the first conductive type crystalline semiconductor layer mainly composed of silicon preferably contains boron as an impurity.
【００２１】なお、本明細書において、特に言及しない
限り、「結晶質半導体層」という用語は、方位の異なる
複数の結晶粒を構成要素として含むあらゆる形態の半導
体層を包含する。したがって、「結晶質半導体層」とい
う用語は、たとえば、複数の結晶子の集合体である半導
体層のみならず、微結晶あるいはマイクロクリスタルと
呼ばれる結晶成分と非晶質成分が混在した状態の半導体
層も含む。In this specification, unless otherwise specified, the term “crystalline semiconductor layer” encompasses any form of semiconductor layer containing a plurality of crystal grains having different orientations as constituent elements. Therefore, the term “crystalline semiconductor layer” refers to, for example, a semiconductor layer in which a crystal component and an amorphous component called microcrystal or microcrystal are mixed, as well as a semiconductor layer that is an aggregate of a plurality of crystallites. Including.
【００２２】本発明による薄膜太陽電池において、半導
体層を支持する基板表面には凹凸によるテクスチャー構
造が設けられている。この凹凸の大きさは代表的には
０．０１〜１０μｍ、より好ましくは０．０５〜２μｍ
の範囲であり、目視ではその凹凸形状を判別できない。
すなわち、目視では当該基板表面は平滑な面として認識
される。そこで、本明細書において「基板に垂直」ある
いは「基板に平行」というとき、特に断りのない限り、
「垂直」および「平行」の基準は、この目視により平滑
であるとみなされる基板面（巨視的基板面）である。In the thin-film solar cell according to the present invention, the surface of the substrate supporting the semiconductor layer is provided with a textured structure by unevenness. The size of the unevenness is typically 0.01 to 10 μm, more preferably 0.05 to 2 μm.
And the uneven shape cannot be visually discriminated.
That is, the substrate surface is visually recognized as a smooth surface. Therefore, in this specification, when "perpendicular to the substrate" or "parallel to the substrate", unless otherwise specified,
The criteria for "vertical" and "parallel" are the substrate surface (macroscopic substrate surface) that is considered visually smooth.
【００２３】一方、微視的にみれば、半導体層を支持す
る基板表面は凹凸によるテクスチャー構造を形成してい
る。この凹凸形状は、原子間力顕微鏡により測定するこ
とができ、凹凸大きさＲおよび凹凸間隔Ｌは次のように
定義される。すなわち、基板表面の任意の領域におい
て、原子間力顕微鏡により長さ５μｍにわたって表面凹
凸形状の線測定を行い、測定により得られた表面形状波
形について、日本工業規格ＪＩＳＢ０６０２−１９９４
で規定された表面凹凸の算術平均値Ｒａを凹凸大きさＲ
とし、日本工業規格ＪＩＳＢ０６０２−１９９４で規定
された表面凹凸の平均間隔Ｓｍを凹凸間隔Ｌとする。On the other hand, microscopically, the surface of the substrate that supports the semiconductor layer has a textured structure formed by irregularities. This uneven shape can be measured by an atomic force microscope, and the unevenness size R and the unevenness interval L are defined as follows. That is, in an arbitrary region of the substrate surface, a line measurement of the surface unevenness is performed over a length of 5 μm with an atomic force microscope, and the surface shape waveform obtained by the measurement is subjected to Japanese Industrial Standard JISB0602-1994.
The arithmetic mean value Ra of the surface irregularities specified in
The average interval Sm of the surface irregularities specified in Japanese Industrial Standard JISB0602-1994 is defined as the irregularity interval L.
【００２４】[0024]
【発明の実施の形態】本発明者は、平滑な表面を有する
ガラス板に被覆された酸化亜鉛をエッチングすることで
凹凸大きさＲと凹凸間隔Ｌとの比Ｒ／Ｌを適宜変化させ
た基板上に、プラズマＣＶＤ法によりシリコン結晶質半
導体層を形成する検討を行った。その結果、チャネリン
グ粒子が少ない条件においては、図６の曲線６１に示す
ように、Ｒ／Ｌの平均値が小さい、言い換えれば表面凹
凸が小さい場合のみシリコン結晶質半導体層の配向性を
強めることができるのに対して、チャネリング粒子が多
い条件においては、図６の曲線６２に示すように、Ｒ／
Ｌの平均値が小さい場合、すなわち表面凹凸が小さい場
合だけでなく、Ｒ／Ｌが０．１〜１．５の範囲にある場
合に、（２２０）面のＸ線回折ピークの積分強度Ｉ220
と（１１１）面のＸ線回折ピークの積分強度Ｉ111との
比Ｉ220／Ｉ111を３以上とすることが可能であることを
発見した。BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has developed a substrate in which the ratio R / L of the size R of irregularities to the distance L between irregularities is appropriately changed by etching zinc oxide coated on a glass plate having a smooth surface. A study was conducted on forming a silicon crystalline semiconductor layer by a plasma CVD method. As a result, under the condition that the number of channeling particles is small, as shown by the curve 61 in FIG. 6, it is possible to enhance the orientation of the silicon crystalline semiconductor layer only when the average value of R / L is small, in other words, only when the surface unevenness is small. On the other hand, under the condition that the number of the channeling particles is large, as shown by the curve 62 in FIG.
Not only when the average value of L is small, that is, when the surface roughness is small, but also when R / L is in the range of 0.1 to 1.5, the integrated intensity I 220 of the X-ray diffraction peak of the (220) plane is obtained.
It has been discovered that the ratio I 220 / I 111 between the X-ray diffraction peak and the integrated intensity I 111 of the (111) plane can be set to 3 or more.
【００２５】この発見により初めて、光閉込効果による
光吸収量の増大と、結晶質半導体層中の欠陥が増大しな
いことによる膜厚方向に対する良好なキャリア輸送特性
との両立が可能となり、高い光電変換効率を有する薄膜
太陽電池が実現できた。For the first time, this discovery makes it possible to increase both the amount of light absorption due to the light confinement effect and good carrier transport characteristics in the film thickness direction due to no increase in defects in the crystalline semiconductor layer. A thin-film solar cell with conversion efficiency has been realized.
【００２６】本発明の薄膜太陽電池に用いる基板材料と
しては、ガラス、金属、あるいはポリイミドやポリビニ
ルといった２００℃程度の耐熱性を有する樹脂、さらに
はそれらが積層されたもの等、種々のものが使用でき
る。さらには、それらの表面に金属膜、透明導電膜、あ
るいは絶縁膜等を被覆したものも含まれる。また、基板
厚さは特に限定されるものではないが、構造を支持し得
るよう適当な強度や重量を有するように、例えば０．１
〜３０ｍｍ程度である。As the substrate material used for the thin-film solar cell of the present invention, various materials such as glass, metal, and resin having heat resistance of about 200 ° C. such as polyimide and polyvinyl, and those laminated thereon are used. it can. Further, those in which the surface is covered with a metal film, a transparent conductive film, an insulating film, or the like are also included. Further, the thickness of the substrate is not particularly limited, but for example, 0.1 mm so as to have appropriate strength and weight to support the structure.
It is about 30 mm.
【００２７】基板の表面に凹凸を設ける手段としては、
例えば、平滑な表面を有する基板上に、堆積すると同時
に表面に凹凸が形成されるような膜を形成してもよい。
該表面に凹凸が形成される膜は基板と同じ材料であって
も、または異なる材料であっても構わない。また、基板
表面に対してサンドブラストのような機械加工、あるい
はエッチングといった化学的加工処理を行うことでも凹
凸の形成は可能である。Means for providing irregularities on the surface of the substrate include:
For example, a film may be formed on a substrate having a smooth surface so as to deposit and form irregularities on the surface at the same time.
The film on which the irregularities are formed on the surface may be the same material as the substrate or a different material. The irregularities can also be formed by performing mechanical processing such as sandblasting or chemical processing such as etching on the substrate surface.
【００２８】本発明の薄膜太陽電池は、凹凸間隔Ｌに対
する凹凸大きさＲの比Ｒ／Ｌが０．１〜１．５の範囲に
あるような凹凸によるテクスチャー構造を有する基板、
ならびに図１に示すような、テクスチャーを有する基板
上においても、基板に垂直な方向に柱状に成長している
結晶粒により主として構成されている第１導電型結晶質
半導体層および真性結晶質半導体層を有するので、十分
な光閉込効果を生じさせるとともに、光電変換素子構造
中の欠陥増大を抑制し、高い光電変換効率をもたらすこ
とができる。なお光閉込効果を向上させるためにはＲ／
Ｌの値が大きい方が望ましく、光電変換素子中の欠陥増
大を抑制するためにはＲ／Ｌの値が小さい方が望まし
い。したがって、この両者を満足させることのできる凹
凸テクスチャー構造としては、Ｒ／Ｌの値が０．２〜
１．２の範囲にあるものが好ましく、０．２５〜０．８
の範囲にあるものがより好ましい。The thin-film solar cell of the present invention has a substrate having a texture structure with irregularities such that the ratio R / L of the irregularity size R to the irregularity interval L is in the range of 0.1 to 1.5.
And a first conductivity type crystalline semiconductor layer and an intrinsic crystalline semiconductor layer mainly composed of crystal grains growing in a columnar direction in a direction perpendicular to the substrate even on a textured substrate as shown in FIG. Therefore, not only can a sufficient light confinement effect be produced, but also an increase in defects in the photoelectric conversion element structure can be suppressed, and high photoelectric conversion efficiency can be achieved. In order to improve the optical confinement effect, R /
A larger value of L is desirable, and a smaller value of R / L is desirable in order to suppress an increase in defects in the photoelectric conversion element. Therefore, as an uneven texture structure that can satisfy both of them, the value of R / L is 0.2 to 0.2.
Those in the range of 1.2 are preferable, and 0.25 to 0.8
Are more preferable.
【００２９】そして、第１導電型結晶質半導体層が１ｎ
ｍ以上２００ｎｍ未満の厚みを有し、基板の表面から高
さ２００ｎｍまでの部分において、基板に垂直な方向に
柱状に成長している結晶粒が、当該部分における結晶粒
全体の少なくとも５０％以上を占め、かつ基板に垂直な
方向に１００ｎｍ以上の長さを有する場合には、同一の
結晶粒内に第１導電型結晶質半導体層と真性結晶質半導
体層との接合界面が形成されている傾向が強く、特に好
ましい。The first conductive type crystalline semiconductor layer is 1n
In a portion having a thickness of at least 200 m and less than 200 nm, and in a portion from the surface of the substrate to a height of 200 nm, at least 50% or more of all the crystal grains in the portion perpendicular to the substrate grow in a columnar direction. When it occupies and has a length of 100 nm or more in a direction perpendicular to the substrate, a bonding interface between the first conductivity type crystalline semiconductor layer and the intrinsic crystalline semiconductor layer tends to be formed in the same crystal grain. Is particularly preferred.
【００３０】さらには、第１導電型結晶質半導体層の膜
厚を１ｎｍ以上１００ｎｍ以下とすることにより、直列
抵抗の低減、または導電型層における光吸収量の低減と
いった効果が得られるので光電変換効率の向上に効果的
である。Further, by setting the thickness of the first conductivity type crystalline semiconductor layer to 1 nm or more and 100 nm or less, an effect such as a reduction in series resistance or a reduction in light absorption in the conductivity type layer can be obtained. It is effective for improving efficiency.
【００３１】太陽電池用基板は、電極に用いるための導
電性膜で被覆されていることが多い。そのような導電性
膜は、基板表面の凹凸テクスチャーを形成することがで
きる。そのような導電性膜には、蒸着法等の公知技術に
より形成し得るＡｇ、Ａｌ、Ｔｉ、Ｐｄ等の可視光反射
率の高い金属およびその合金を用いることもできる。し
かしながら、透明導電膜を用いることで、光閉込効果を
高めることが可能であり、さらには、基板に含まれてい
る不純物が光電変換部を形成する際に光電変換部へ取り
込まれることを防止することもできるので、特に好まし
い。また、透明導電膜は必ずしも単独で用いられる必要
はなく、例えば金属膜と光電変換部との間に挿入されて
いてもよい。The solar cell substrate is often coated with a conductive film to be used as an electrode. Such a conductive film can form an uneven texture on the substrate surface. For such a conductive film, a metal having a high visible light reflectance, such as Ag, Al, Ti, or Pd, which can be formed by a known technique such as an evaporation method, or an alloy thereof can be used. However, by using a transparent conductive film, it is possible to enhance the light confinement effect, and further, it is possible to prevent impurities contained in the substrate from being taken into the photoelectric conversion unit when forming the photoelectric conversion unit. It is particularly preferable because it can be performed. Further, the transparent conductive film does not necessarily have to be used alone, and may be inserted, for example, between the metal film and the photoelectric conversion unit.
【００３２】これらの透明導電膜は、例えばスパッタリ
ング法、常圧ＣＶＤ法、減圧ＣＶＤ法、電子ビーム蒸着
法、ゾルゲル法、電析法等の公知の方法により作製でき
る。その中でも特に、スパッタリング法は、透明導電膜
の透過率や抵抗率を薄膜太陽電池に適したものに制御す
ることが容易であるので望ましい。These transparent conductive films can be produced by a known method such as a sputtering method, a normal pressure CVD method, a low pressure CVD method, an electron beam evaporation method, a sol-gel method, and an electrodeposition method. Among them, the sputtering method is particularly preferable because it is easy to control the transmittance and resistivity of the transparent conductive film to those suitable for a thin-film solar cell.
【００３３】なお、これらの透明導電膜中に微量の不純
物が添加されていてもよい。例えば、酸化亜鉛の場合で
は、５×１０20〜５×１０21ｃｍ-3程度のガリウムやア
ルミニウムといった第３Ｂ族元素あるいは銅のような第
１Ｂ族元素が含有されることにより抵抗率が低減するの
で、電極として使用するのに好ましい。また、これらの
透明導電膜の厚さは薄すぎると特性の均一性に問題が生
じ、厚すぎると透過率の減少による光電変換効率の低下
やコストの増大を引き起こすため、好ましくは０．１〜
２μｍ程度である。A small amount of impurities may be added to these transparent conductive films. For example, in the case of zinc oxide, the resistivity is reduced by containing a Group 3B element such as gallium or aluminum or a Group 1B element such as copper at about 5 × 10 20 to 5 × 10 21 cm −3. Therefore, it is preferable to use it as an electrode. In addition, when the thickness of these transparent conductive films is too small, there is a problem in uniformity of characteristics. When the thickness is too large, a decrease in transmittance causes a decrease in photoelectric conversion efficiency or an increase in cost.
It is about 2 μm.
【００３４】透明導電膜は広く用いられている酸化錫、
酸化インジウムあるいはＩＴＯといった材料を用いても
よい。しかしながら、主として酸化亜鉛から成る材料に
は、安価である、耐プラズマ性が高く変質しにくいとい
う利点があるので、透明電極部として用いるのに好まし
い。The transparent conductive film is a widely used tin oxide,
A material such as indium oxide or ITO may be used. However, a material mainly composed of zinc oxide is advantageous in that it is inexpensive, has high plasma resistance and is hardly deteriorated, and is therefore preferably used as a transparent electrode portion.
【００３５】一方、巨視的基板面の法線方向に対する第
１導電型シリコン結晶質半導体層の優先配向面を（１１
０）とすることで、その上に形成される真性シリコン結
晶質半導体層の優先配向面を（１１０）とすることがで
きる。そうすると、優先配向面が（１１１）や（１０
０）である場合のように、シリコン層形成の際にシリコ
ン層がエッチングされる傾向が強く、膜損傷の恐れがあ
り形成速度が遅くなる条件を用いることなく真性シリコ
ン結晶質半導体層を形成できるので、高効率な薄膜太陽
電池を短時間で安定に製造することが可能となる。特
に、基板表面に接している第１導電型シリコン結晶質半
導体層の上に形成された真性シリコン結晶質半導体層の
（２２０）Ｘ線回折ピークの積分強度Ｉ220と（１１
１）Ｘ線回折ピークの積分強度Ｉ111の比Ｉ220／Ｉ111
が３以上、より好ましくは５以上である場合に、良好な
光電変換特性が得られる。On the other hand, the preferred orientation plane of the first conductivity type silicon crystalline semiconductor layer with respect to the normal direction of the macroscopic substrate surface is (11).
By setting 0), the preferred orientation plane of the intrinsic silicon crystalline semiconductor layer formed thereon can be (110). Then, the preferred orientation plane is (111) or (10).
As in the case of (0), the silicon layer has a strong tendency to be etched when the silicon layer is formed, and the intrinsic silicon crystalline semiconductor layer can be formed without using a condition that the film formation may be damaged and the formation speed is reduced. Therefore, a highly efficient thin-film solar cell can be stably manufactured in a short time. In particular, the integrated intensity I 220 of the (220) X-ray diffraction peak of the intrinsic silicon crystalline semiconductor layer formed on the first conductive type silicon crystalline semiconductor layer in contact with the substrate surface and (11)
1) Ratio of integrated intensity I 111 of X-ray diffraction peak I 220 / I 111
Is 3 or more, more preferably 5 or more, good photoelectric conversion characteristics are obtained.
【００３６】また、第１導電型シリコン結晶質半導体層
がホウ素を不純物として含有する場合は、特に（１１
０）配向の傾向が強くなるので望ましい。その理由は明
らかではないが、参考文献（１）〜（４）には、面方位
が（１００）あるいは（１１１）である単結晶シリコン
の表面にボロンが存在するとシリコンの反応性が低下す
るという報告があり、同様の現象により（１００）ある
いは（１１１）が基板に平行となる結晶粒の成長が抑制
されるためであると考えられる。ホウ素の含有量として
０．０１〜１０原子％の範囲であれば、（１１０）配向
が強められる効果が得られる。より好ましくは０．０５
〜９原子％、最も好ましくは０．２〜８原子％である。When the first-conductivity-type silicon crystalline semiconductor layer contains boron as an impurity, (11)
0) It is desirable because the orientation tends to be strong. Although the reason is not clear, references (1) to (4) indicate that the presence of boron on the surface of single crystal silicon having a plane orientation of (100) or (111) decreases the reactivity of silicon. It is reported that the similar phenomenon suppresses the growth of crystal grains in which (100) or (111) is parallel to the substrate. When the boron content is in the range of 0.01 to 10 atomic%, the effect of enhancing the (110) orientation can be obtained. More preferably 0.05
-9 atomic%, most preferably 0.2-8 atomic%.
【００３７】以下、実施例により本発明をさらに説明す
る。Hereinafter, the present invention will be further described with reference to examples.
【００３８】実施例１ 図３に作製した薄膜太陽電池の構造を示す。平滑な表面
を有するガラス板３１ａ上にテクスチャー構造を有する
酸化錫３１ｂを形成した上に、通常の電子ビーム蒸着法
により厚さ５０ｎｍの酸化亜鉛層３１ｃを形成したもの
を基板３１として用いた。原子間力顕微鏡により測定し
た基板表面の凹凸大きさＲと凹凸間隔Ｌとの比Ｒ／Ｌは
０．８であった。Example 1 FIG. 3 shows the structure of the manufactured thin-film solar cell. A substrate 31 was prepared by forming tin oxide 31b having a texture structure on a glass plate 31a having a smooth surface and forming a zinc oxide layer 31c having a thickness of 50 nm by a normal electron beam evaporation method. The ratio R / L of the unevenness size R and the unevenness interval L on the substrate surface measured by an atomic force microscope was 0.8.
【００３９】続いて、該基板３１の上にｐ型シリコン結
晶質半導体層３２、ｉ型シリコン結晶質半導体層３３、
ｎ型シリコン半導体層３４を高周波プラズマＣＶＤによ
り順に形成した。プラズマＣＶＤ装置は前記各層ごとの
形成室が設けられており、各形成室およびロードロック
室間は真空を破ることなく基板を搬送できるようになっ
ている。各形成室内部には平行平板型の電極が設けられ
ている。電極は、カソード電極とそれに対向するアノー
ド電極からなる。カソード電極にプラズマ励起用高周波
電力が導入される。各形成室において、基板は、温度制
御機能を有するアノード電極側に、テクスチャー構造を
有する表面側がカソード電極に対向するように設置され
る。Subsequently, a p-type silicon crystalline semiconductor layer 32, an i-type silicon crystalline semiconductor layer 33,
The n-type silicon semiconductor layers 34 were sequentially formed by high frequency plasma CVD. The plasma CVD apparatus is provided with a forming chamber for each of the layers, and the substrate can be transferred between each forming chamber and the load lock chamber without breaking the vacuum. Inside each forming chamber, a parallel plate type electrode is provided. The electrode is composed of a cathode electrode and an anode electrode opposed thereto. High frequency power for plasma excitation is introduced to the cathode electrode. In each forming chamber, the substrate is placed on the anode electrode side having a temperature control function such that the surface side having the texture structure faces the cathode electrode.
【００４０】基板表面に直接形成されるｐ型シリコン結
晶質半導体層３２の形成条件は以下のとおりである。原
料ガスはＳｉＨ4、Ｈ2およびＢ2Ｈ6の混合ガスとした。
ガス混合比はｐ型シリコン結晶質半導体層中のボロン濃
度が０．８原子％となるように調整した。投入する高周
波の周波数は４０．６８ＭＨｚ、形成室圧力は２５Ｐ
ａ、基板温度は１５０℃とした。また、膜厚は２０ｎｍ
とした。The conditions for forming the p-type silicon crystalline semiconductor layer 32 directly formed on the substrate surface are as follows. The source gas was a mixed gas of SiH 4 , H 2 and B 2 H 6 .
The gas mixture ratio was adjusted so that the boron concentration in the p-type silicon crystalline semiconductor layer was 0.8 atomic%. The frequency of the high frequency to be charged is 40.68 MHz and the pressure of the forming chamber is 25 P
a, the substrate temperature was 150 ° C. The film thickness is 20 nm
And
【００４１】ｐ型シリコン結晶質半導体層３２を形成し
た後、ｉ型シリコン結晶質半導体層３３を形成した。ｉ
型シリコン結晶質半導体層３３の形成条件は次のとおり
である。原料ガスはＳｉＨ4およびＨ2の混合ガスとし
た。ガス混合比はｉ型シリコン層が十分に結晶化される
ように調整した。投入する高周波の周波数は４０．６８
ＭＨｚ、形成室圧力は４０Ｐａ、基板温度は１５０℃と
した。また、膜厚は１μｍとした。After forming the p-type silicon crystalline semiconductor layer 32, an i-type silicon crystalline semiconductor layer 33 was formed. i
The conditions for forming the type silicon crystalline semiconductor layer 33 are as follows. The source gas was a mixed gas of SiH 4 and H 2 . The gas mixture ratio was adjusted so that the i-type silicon layer was sufficiently crystallized. High frequency of 40.68
MHz, the formation chamber pressure was 40 Pa, and the substrate temperature was 150 ° C. The thickness was 1 μm.
【００４２】また、この条件を用いてｉ型シリコン結晶
質半導体層を平坦なガラス基板上に製膜した場合、（２
２０）Ｘ線回折ピークの積分強度Ｉ220と（１１１）Ｘ
線回折ピークの積分強度Ｉ111の比Ｉ220／Ｉ111は、図
６に示すように１０．０であり、このｉ型シリコン結晶
質半導体層３３自体が基板面に対して強い（２２０）配
向を示すものであった。When an i-type silicon crystalline semiconductor layer is formed on a flat glass substrate using these conditions, (2)
20) X-ray diffraction peak integrated intensity I 220 and (111) X
The ratio I 220 / I 111 of the integrated intensity I 111 of the line diffraction peak is 10.0 as shown in FIG. 6, and the i-type silicon crystalline semiconductor layer 33 itself has a strong (220) orientation with respect to the substrate surface. It was shown.
【００４３】ｉ型シリコン結晶質半導体層３３を形成し
た後、ｎ型シリコン半導体層３４を形成した。ｎ型シリ
コン半導体層３４の形成条件は以下のとおりである。原
料ガスはＳｉＨ4、Ｈ2およびＰＨ3の混合ガスとした。
ガス混合比はｎ型シリコン半導体層中のリン濃度が０．
８％となるように調整した。投入する高周波の周波数は
４０．６８ＭＨｚ、形成室圧力は２５Ｐａ、基板温度は
１５０℃とした。また、膜厚は２０ｎｍとした。After forming the i-type silicon crystalline semiconductor layer 33, an n-type silicon semiconductor layer 34 was formed. The conditions for forming the n-type silicon semiconductor layer 34 are as follows. The source gas was a mixed gas of SiH 4 , H 2 and PH 3 .
The gas mixture ratio is such that the phosphorus concentration in the n-type silicon semiconductor layer is 0.
It was adjusted to be 8%. The frequency of the high frequency to be charged was 40.68 MHz, the pressure of the forming chamber was 25 Pa, and the substrate temperature was 150 ° C. The thickness was 20 nm.
【００４４】その後、プラズマＣＶＤ装置から基板を取
り出し、通常の電子ビーム蒸着法により膜厚５０ｎｍの
酸化亜鉛を形成して裏面反射層３５とした。そしてレー
ザースクライブ法により１ｃｍ角の大きさに分離した。
その後、通常の電子ビーム蒸着法により裏面電極３６と
して銀を形成して、ガラス板３１ａ側から光を入射する
スーパーストレート型薄膜太陽電池を作製した。Thereafter, the substrate was taken out of the plasma CVD apparatus, and zinc oxide having a thickness of 50 nm was formed by a normal electron beam evaporation method to form a back reflection layer 35. Then, it was separated into 1 cm squares by a laser scribe method.
Thereafter, silver was formed as the back electrode 36 by a normal electron beam evaporation method, and a super straight type thin film solar cell in which light was incident from the glass plate 31a side was manufactured.
【００４５】図４にこの薄膜太陽電池の断面を透過型電
子顕微鏡により観察した像を模式的に示す。ただしｎ型
シリコン半導体層３４、裏面反射層３５、裏面電極３６
は省略している。基板表面上には複数の結晶粒が生成し
ており、そのうち約５０％の結晶粒は個々の凹凸表面に
垂直な方向に成長しているのに対して、残りの約５０％
の結晶粒は基板に垂直な方向に成長していた。そして、
基板に垂直な方向に成長している結晶粒のほとんどは基
板に垂直な方向に１００ｎｍ以上の長さを有する柱状結
晶粒であり、膜厚が増えるにつれて基板に平行な方向の
粒径が増大しながら、当該部分においてその割合を増し
ていた。FIG. 4 schematically shows an image obtained by observing a cross section of the thin film solar cell with a transmission electron microscope. However, the n-type silicon semiconductor layer 34, the back reflection layer 35, the back electrode 36
Is omitted. A plurality of crystal grains are formed on the surface of the substrate, and about 50% of the crystal grains grow in a direction perpendicular to the respective uneven surface, while the remaining about 50%
Was grown in the direction perpendicular to the substrate. And
Most of the crystal grains growing in the direction perpendicular to the substrate are columnar crystal grains having a length of 100 nm or more in the direction perpendicular to the substrate, and the grain size in the direction parallel to the substrate increases as the film thickness increases. However, the ratio was increased in this part.
【００４６】さらに、ｉ型層全体に相当する領域の結晶
方位に関する情報を得るため、直径０．８μｍの制限視
野しぼりを入れて制限視野電子線回折を行った。得られ
た回折像から、このｉ型シリコン結晶質半導体層では、
基板に平行に（１１０）面が配向していることが分かっ
た。すなわち基板に垂直な方向に成長しているｐ型シリ
コン結晶質半導体層の結晶粒は、基板に平行に（１１
０）面を配向させており、その上に形成されたｉ型シリ
コン結晶質半導体層は下地となるｐ型シリコン結晶質半
導体層の結晶方位を引き継ぐ形で成長していることが分
かった。Further, in order to obtain information on the crystal orientation in a region corresponding to the entire i-type layer, a restricted area electron beam diffraction was performed with a restricted area of 0.8 μm in diameter. From the obtained diffraction image, in the i-type silicon crystalline semiconductor layer,
It was found that the (110) plane was oriented parallel to the substrate. That is, the crystal grains of the p-type silicon crystalline semiconductor layer growing in the direction perpendicular to the substrate are parallel to the substrate (11
It has been found that the 0) plane is oriented, and the i-type silicon crystalline semiconductor layer formed thereon grows in a form that inherits the crystal orientation of the underlying p-type silicon crystalline semiconductor layer.
【００４７】また、ｉ型シリコン結晶質半導体層の（１
１０）配向性の度合いを定量的に調べるために、この薄
膜太陽電池と同じプロセスでｉ型層まで形成したものに
ついてＸ線回折を行ったところ、（２２０）面のＸ線回
折ピークの積分強度Ｉ220と（１１１）Ｘ線回折ピーク
の積分強度Ｉ111の比Ｉ220／Ｉ111が６．５であった。Further, (1) of the i-type silicon crystalline semiconductor layer
10) In order to quantitatively examine the degree of orientation, X-ray diffraction was performed on an i-type layer formed by the same process as this thin-film solar cell. The integrated intensity of the X-ray diffraction peak on the (220) plane was obtained. The ratio I 220 / I 111 between I 220 and the integrated intensity I 111 of the (111) X-ray diffraction peak was 6.5.
【００４８】この薄膜太陽電池のＡＭ１．５（１００ｍ
Ｗ／ｃｍ2）照射条件下における電流−電圧特性の測定
を行ったところ、セル面積１ｃｍ2において開放電圧
０．５２５Ｖ、短絡電流２２．８ｍＡ／ｃｍ2、形状因
子０．７０５、光電変換効率８．４４％という値が得ら
れた。The AM1.5 (100 m
W / cm 2) current under the irradiation condition - was measured for the voltage characteristic, the open-circuit voltage 0.525V, a short circuit current 22.8mA / cm 2 in cell area 1 cm 2, the shape factor 0.705, photoelectric conversion efficiency 8 A value of .44% was obtained.
【００４９】比較例１ 凹凸形状の効果を検証するために、平滑な表面を有する
ガラス板上にテクスチャー構造を有する酸化錫を形成し
た後、液温２５℃の０．５％塩酸水溶液に３０秒間浸し
てエッチングを行うことで表面凹凸を尖鋭化し、さらに
通常の電子ビーム蒸着法により厚さ５０ｎｍの酸化亜鉛
層を形成したものを基板として用いた。原子間力顕微鏡
により測定した、この基板表面の凹凸大きさＲと凹凸間
隔Ｌとの比Ｒ／Ｌは１．６５であった。この基板作製工
程以外は、実施例１と同様に薄膜太陽電池を作製した。Comparative Example 1 In order to verify the effect of the uneven shape, tin oxide having a textured structure was formed on a glass plate having a smooth surface, and then placed in a 0.5% hydrochloric acid aqueous solution at a liquid temperature of 25 ° C. for 30 seconds. The surface was sharpened by immersion and etching, and a zinc oxide layer having a thickness of 50 nm formed by a normal electron beam evaporation method was used as a substrate. The ratio R / L of the unevenness size R of the substrate surface to the unevenness interval L, as measured by an atomic force microscope, was 1.65. Except for this substrate manufacturing step, a thin-film solar cell was manufactured in the same manner as in Example 1.
【００５０】図５にこの薄膜太陽電池の断面を透過型電
子顕微鏡により観察した像を模式的に示す。ただし図４
と同様に、ｎ型シリコン半導体層、裏面反射層、裏面電
極は省略している。凹凸表面上には複数の結晶粒が生成
しており、そのほとんどの結晶粒が個々の凹凸表面に垂
直な方向に成長していた。これら凹凸表面に垂直な方向
に成長している結晶粒は、やがて隣接する凹凸表面から
成長してきた結晶粒と衝突した後、基板に垂直な方向へ
と成長方向を徐々に変化させていた。しかし、基板に垂
直な方向に顕著に成長している結晶粒は確認されなかっ
た。FIG. 5 schematically shows an image obtained by observing a cross section of the thin film solar cell with a transmission electron microscope. However, FIG.
Similarly, the n-type silicon semiconductor layer, the back reflection layer, and the back electrode are omitted. A plurality of crystal grains were formed on the uneven surface, and most of the crystal grains were grown in a direction perpendicular to each of the uneven surfaces. The crystal grains growing in the direction perpendicular to the uneven surface gradually collided with the crystal grains grown from the adjacent uneven surface, and thereafter gradually changed the growth direction to the direction perpendicular to the substrate. However, no crystal grains remarkably grown in the direction perpendicular to the substrate were found.
【００５１】さらに、ｉ型層全体に相当する領域の結晶
方位に関する情報を得るため、直径０．８μｍの制限視
野しぼりを入れて制限視野電子線回折を行った。得られ
た回折像から、このｉ型シリコン結晶質半導体層は基板
に平行な配向面を明確には有していないことが分かっ
た。これは凹凸形状が適切でないため、ｐ型シリコン結
晶質半導体層の結晶粒が基板に平行な配向面を有してお
らず、そのため、その上に形成されたｉ型シリコン結晶
質半導体層も基板に平行な配向面を有することなく成長
を開始しているためであると考えられる。Further, in order to obtain information on the crystal orientation in a region corresponding to the entire i-type layer, a selected area electron beam diffraction was performed with a narrowed area of 0.8 μm in diameter. From the obtained diffraction image, it was found that this i-type silicon crystalline semiconductor layer did not clearly have an orientation plane parallel to the substrate. This is because the p-type silicon crystalline semiconductor layer does not have an orientation plane parallel to the substrate because the irregular shape is not appropriate. Therefore, the i-type silicon crystalline semiconductor layer formed thereon is It is considered that the growth was started without having an orientation plane parallel to.
【００５２】また、ｉ型シリコン結晶質半導体層の（１
１０）配向性の度合いを定量的に調べるために、この薄
膜太陽電池と同じプロセスでｉ型層まで形成したものに
ついてＸ線回折を行ったところ、（２２０）Ｘ線回折ピ
ークの積分強度Ｉ220と（１１１）Ｘ線回折ピークの積
分強度Ｉ111の比Ｉ220／Ｉ111が２．０であり、実施例
１の場合と比較して著しく配向性が劣っていた。Further, (1) of the i-type silicon crystalline semiconductor layer
10) In order to quantitatively examine the degree of orientation, X-ray diffraction was performed on an i-type layer formed by the same process as the thin-film solar cell. (220) The integrated intensity of the X-ray diffraction peak I 220 And the ratio I 220 / I 111 of the integrated intensity I 111 of the (111) X-ray diffraction peak was 2.0, indicating that the orientation was significantly inferior to that of Example 1.
【００５３】この薄膜太陽電池のＡＭ１．５（１００ｍ
Ｗ／ｃｍ2）照射条件下における電流−電圧特性の測定
を行ったところ、セル面積１ｃｍ2において開放電圧
０．５０８Ｖ、短絡電流２０．６ｍＡ／ｃｍ2、形状因
子０．６７０、光電変換効率７．０１％という値が得ら
れた。実施例１の結果と比較して、開放電圧、短絡電
流、形状因子の全てにおいて特性の低下が生じていた。
さらに、実施例１および比較例１の素子について分光感
度測定を行った結果から、比較例１の素子は特に短波長
側での感度が劣ることが判明した。これは、光電変換層
の基板側、すなわちｐ型シリコン結晶質半導体層とｉ型
シリコン結晶質半導体層との界面近傍の構造に問題があ
ることを意味しており、透過型電子顕微鏡観察結果によ
り矛盾なく説明できる。The AM1.5 (100 m) of this thin-film solar cell
W / cm 2) current under the irradiation condition - was measured for the voltage characteristic, the open-circuit voltage 0.508V, a short circuit current 20.6mA / cm 2 in cell area 1 cm 2, the shape factor 0.670, photoelectric conversion efficiency 7 A value of 0.011% was obtained. As compared with the result of Example 1, the characteristics were reduced in all of the open-circuit voltage, the short-circuit current, and the shape factor.
Further, the results of spectral sensitivity measurement of the devices of Example 1 and Comparative Example 1 revealed that the device of Comparative Example 1 was inferior in sensitivity especially on the short wavelength side. This means that there is a problem in the structure of the photoelectric conversion layer on the substrate side, that is, the structure near the interface between the p-type silicon crystalline semiconductor layer and the i-type silicon crystalline semiconductor layer. Explain consistently.
【００５４】比較例２ 凹凸形状の効果を検証するために、基板３１表面の酸化
亜鉛層３１ｃを厚さ５００ｎｍとしたこと以外は、実施
例１と同様に薄膜太陽電池を作製した。原子間力顕微鏡
により測定した基板表面の凹凸大きさＲと凹凸間隔Ｌと
の比Ｒ／Ｌの平均値は０．０５であった。Comparative Example 2 A thin-film solar cell was manufactured in the same manner as in Example 1, except that the thickness of the zinc oxide layer 31c on the surface of the substrate 31 was changed to 500 nm in order to verify the effect of the uneven shape. The average value of the ratio R / L between the unevenness size R and the unevenness interval L on the substrate surface measured by an atomic force microscope was 0.05.
【００５５】ｉ型シリコン結晶質半導体層の（１１０）
配向性の度合いを定量的に調べるために、この薄膜太陽
電池と同じプロセスでｉ型層まで形成したものについて
Ｘ線回折を行ったところ、（２２０）Ｘ線回折ピークの
積分強度Ｉ220と（１１１）Ｘ線回折ピークの積分強度
Ｉ111の比Ｉ220／Ｉ111が９．０であり、平坦なガラス
基板上に製膜した場合と同等の値であった。(110) of the i-type silicon crystalline semiconductor layer
In order to quantitatively examine the degree of orientation, X-ray diffraction was performed on an i-type layer formed by the same process as the thin-film solar cell. The integrated intensity of the (220) X-ray diffraction peak I 220 and (220) 111) The ratio I 220 / I 111 of the integrated intensity I 111 of the X-ray diffraction peak was 9.0, which was the same value as when a film was formed on a flat glass substrate.
【００５６】この薄膜太陽電池のＡＭ１．５（１００ｍ
Ｗ／ｃｍ2）照射条件下における電流−電圧特性の測定
を行ったところ、セル面積１ｃｍ2において開放電圧
０．５２８Ｖ、短絡電流１９．６ｍＡ／ｃｍ2、形状因
子０．７０８、光電変換効率７．３３％という値が得ら
れた。実施例１の結果と比較すると、開放電圧、形状因
子の値はほぼ同じであるのに対し、光閉込効果が小さい
ので短絡電流が低下していた。The AM1.5 (100 m)
W / cm 2) current under the irradiation condition - was measured for the voltage characteristic, the open-circuit voltage 0.528V, a short circuit current 19.6mA / cm 2 in cell area 1 cm 2, the shape factor 0.708, photoelectric conversion efficiency 7 A value of .33% was obtained. Compared with the results of Example 1, the values of the open voltage and the shape factor were almost the same, but the short-circuit current was low because the optical confinement effect was small.
【００５７】実施例２ チャネリング粒子の効果を検証するために、ｐ型シリコ
ン結晶質半導体層の形成時に原料ガス中にＳｉＨ4、Ｈ2
およびＢ2Ｈ6の他にＡｒガスを添加したこと以外は、実
施例１と同様に薄膜太陽電池を作製した。このときのＳ
ｉＨ4、Ｈ2およびＢ2Ｈ6の混合比は実施例１と同じであ
り、Ａｒの添加量は全混合ガスの５％となるように調整
した。Example 2 In order to verify the effect of the channeling particles, SiH 4 and H 2 were added to the source gas during the formation of the p-type silicon crystalline semiconductor layer.
And B 2 in addition to, except that the addition of Ar gas H 6 was produced in the same manner as in the thin-film solar cell as in Example 1. S at this time
The mixing ratio of iH 4 , H 2 and B 2 H 6 was the same as in Example 1, and the addition amount of Ar was adjusted to be 5% of the total mixed gas.
【００５８】この薄膜太陽電池の断面を透過型電子顕微
鏡により観察すると、実施例１の場合と同様に、基板表
面上には複数の結晶粒が生成していたが、実施例１の場
合よりも結晶粒密度が低減されており、なおかつ約８０
％の結晶粒は基板に垂直な方向に成長していた。そし
て、基板に垂直な方向に成長している結晶粒のほとんど
は基板に垂直な方向に１００ｎｍ以上の長さを有する柱
状結晶粒であり、膜厚が増えるにつれて基板に平行な方
向の粒径が増大しながら、当該部分においてその割合を
増すという傾向は同様であった。When the cross section of this thin-film solar cell was observed with a transmission electron microscope, a plurality of crystal grains were formed on the substrate surface as in the case of the first embodiment. The grain density has been reduced and
% Of the crystal grains were grown in a direction perpendicular to the substrate. Most of the crystal grains growing in the direction perpendicular to the substrate are columnar crystal grains having a length of 100 nm or more in the direction perpendicular to the substrate, and the grain size in the direction parallel to the substrate increases as the film thickness increases. The trend of increasing the proportion in that part while increasing was similar.
【００５９】さらに、ｉ型層全体に相当する領域の結晶
方位に関する情報を得るため、直径０．８μｍの制限視
野しぼりを入れて制限視野電子線回折を行った。得られ
た回折像から、このｉ型シリコン結晶質半導体層では基
板に平行に（１１０）面が配向していることが分かっ
た。すなわち基板に垂直な方向に成長しているｐ型シリ
コン結晶質半導体層の結晶粒では、基板に平行に（１１
０）面が配向しており、その上に形成されたｉ型シリコ
ン結晶質半導体層は下地となるｐ型シリコン結晶質半導
体層の結晶方位を引き継ぐ形で成長していることが分か
った。Further, in order to obtain information on the crystal orientation of the region corresponding to the entire i-type layer, a selected area electron beam diffraction was performed with a narrowed area of 0.8 μm in diameter. From the obtained diffraction image, it was found that in this i-type silicon crystalline semiconductor layer, the (110) plane was oriented parallel to the substrate. That is, in the crystal grains of the p-type silicon crystalline semiconductor layer growing in the direction perpendicular to the substrate, (11)
It was found that the (0) plane was oriented, and the i-type silicon crystalline semiconductor layer formed thereon was grown in a form inheriting the crystal orientation of the underlying p-type silicon crystalline semiconductor layer.
【００６０】また、ｉ型シリコン結晶質半導体層の（１
１０）配向性の度合いを定量的に調べるために、この薄
膜太陽電池と同じプロセスでｉ型層まで形成したものに
ついてＸ線回折を行ったところ、（２２０）Ｘ線回折ピ
ークの積分強度Ｉ220と（１１１）Ｘ線回折ピークの積
分強度Ｉ111の比Ｉ220／Ｉ111が８であった。Further, (1) of the i-type silicon crystalline semiconductor layer
10) In order to quantitatively examine the degree of orientation, X-ray diffraction was performed on an i-type layer formed by the same process as the thin-film solar cell. (220) The integrated intensity of the X-ray diffraction peak I 220 And the ratio I 220 / I 111 of the integrated intensity I 111 of the (111) X-ray diffraction peak was 8.
【００６１】Ａｒ添加により基板に平行に（１１０）配
向している結晶粒が優先的に成長する傾向が強められる
理由は未だ明らかではないが、シースポテンシャルによ
り基板に垂直な方向に加速されたプラズマ中のＡｒ+の
作用によりシリコンのチャネリング方向である＜１１０
＞への成長が促進されること、さらには基板に平行に
（１１０）が向いていない結晶粒をスパッタする効果に
よるものと考えられる。It is not yet clear why Ar addition increases the tendency of the crystal grains oriented in (110) parallel to the substrate to grow preferentially. However, plasma accelerated in a direction perpendicular to the substrate by a sheath potential is not clear. <110 due to the action of Ar + in the channeling direction of silicon.
This is considered to be due to the fact that the growth to> is promoted, and further, the effect of sputtering crystal grains whose (110) is not oriented parallel to the substrate.
【００６２】なお、本実施例では添加する希ガスとして
Ａｒを用いたが、ＨｅあるいはＮｅなどであってもよ
い。Although Ar is used as a rare gas to be added in this embodiment, He or Ne may be used.
【００６３】この薄膜太陽電池のＡＭ１．５（１００ｍ
Ｗ／ｃｍ2）照射条件下における電流−電圧特性の測定
を行ったところ、セル面積１ｃｍ2において開放電圧
０．５４２Ｖ、短絡電流２３．１ｍＡ／ｃｍ2、形状因
子０．７１４、光電変換効率８．９４％という値が得ら
れた。実施例１の素子と比較して、さらに開放電圧、形
状因子の向上が成された。これはｐ型シリコン結晶質半
導体層とｉ型シリコン結晶質半導体層との界面近傍の構
造がさらに適切なものとなったためであり、透過型電子
顕微鏡観察結果により矛盾なく説明できる。The AM1.5 (100 m
W / cm 2) current under the irradiation condition - was measured for the voltage characteristic, the open-circuit voltage 0.542V, a short circuit current 23.1mA / cm 2 in cell area 1 cm 2, the shape factor 0.714, photoelectric conversion efficiency 8 A value of .94% was obtained. The open-circuit voltage and the form factor were further improved as compared with the device of Example 1. This is because the structure near the interface between the p-type silicon crystalline semiconductor layer and the i-type silicon crystalline semiconductor layer has become more appropriate, and can be consistently explained by the results of observation with a transmission electron microscope.
【００６４】上述した実施例以外に、本発明による実施
の形態が多く存在することは、当業者に明らかである。
例えば、テクスチャー構造を有する基板としてステンレ
ス鋼板やアルミニウム板といった金属製基板の上に酸化
錫あるいは酸化亜鉛といった透明導電膜を被覆したもの
でもよい。テクスチャー構造として透明導電膜を形成す
る際に自然に発生する凹凸を利用してもよいし、透明導
電膜の形成後にエッチングを行ってテクスチャー構造を
形成してもよい。また、金属製基板自体にエッチングを
施すことで凹凸を設けてもよい。そして薄膜太陽電池の
構造として、基板上に光電変換層として形成したシリコ
ン結晶質半導体層側より光を入射するサブストレート型
であってもよい。It is apparent to those skilled in the art that there are many embodiments according to the present invention other than the above-described embodiments.
For example, a metal substrate such as a stainless steel plate or an aluminum plate as a substrate having a texture structure may be coated with a transparent conductive film such as tin oxide or zinc oxide. As the texture structure, unevenness which occurs naturally when forming the transparent conductive film may be used, or the texture structure may be formed by performing etching after forming the transparent conductive film. Also, the metal substrate itself may be etched to provide the irregularities. The structure of the thin film solar cell may be a substrate type in which light is incident from the side of a silicon crystalline semiconductor layer formed as a photoelectric conversion layer on a substrate.
【００６５】[0065]
【発明の効果】本発明の薄膜太陽電池では、テクスチャ
ー構造を有する基板上においても、第１導電型結晶質半
導体層ならびに真性結晶質半導体層が基板に垂直な方向
に柱状に成長した結晶粒により主として構成されてい
る。このような構造により、光閉込効果による光吸収量
の増大と、結晶質半導体層中の欠陥が低減されることに
よる膜厚方向に対する良好なキャリア輸送特性との両立
が可能となり、高い光電変換効率を得られる。According to the thin-film solar cell of the present invention, even on a substrate having a texture structure, the first conductivity type crystalline semiconductor layer and the intrinsic crystalline semiconductor layer are formed by crystal grains grown in a columnar direction in a direction perpendicular to the substrate. It is mainly composed. With such a structure, it is possible to increase both the amount of light absorption due to the light confinement effect and good carrier transport characteristics in the film thickness direction by reducing defects in the crystalline semiconductor layer. Gain efficiency.
【図１】 テクスチャー構造を有する基板上と、基板に
垂直な方向に柱状に成長した結晶粒により構成されてい
るシリコン結晶質半導体層とを示す模式図。FIG. 1 is a schematic diagram showing a substrate having a texture structure and a silicon crystalline semiconductor layer composed of crystal grains grown in a column shape in a direction perpendicular to the substrate.
【図２】 凹凸表面に垂直な方向に柱状に成長した結晶
粒により構成されているシリコン結晶質半導体層を示す
模式図。FIG. 2 is a schematic diagram showing a silicon crystalline semiconductor layer composed of crystal grains grown in a column shape in a direction perpendicular to the uneven surface.
【図３】 本発明による薄膜太陽電池構造の一例を示す
模式図。FIG. 3 is a schematic view showing an example of a thin-film solar cell structure according to the present invention.
【図４】 実施例１におけるサンプル断面の透過型電子
顕微鏡観察像を示す模式図。FIG. 4 is a schematic view showing a transmission electron microscope observation image of a cross section of a sample in Example 1.
【図５】 比較例１におけるサンプル断面の透過型電子
顕微鏡観察像を示す模式図。FIG. 5 is a schematic diagram showing a transmission electron microscope observation image of a cross section of a sample in Comparative Example 1.
【図６】 比Ｉ220／Ｉ111とＲ／Ｌとの関係を示す図。FIG. 6 is a diagram showing the relationship between the ratio I 220 / I 111 and R / L.
１１、２１…基板 １２、２２…表面凹凸層 １３、２３…シリコン結晶質半導体層 １４、２４…凹凸大きさＲ １５、２５…凹凸間隔Ｌ １６…凹凸表面 １７…目視による仮想的な基板面 ３１…基板 ３１ａ、４１ａ、５１ａ…ガラス板 ３１ｂ、４１ｂ、５１ｂ…酸化錫層 ３１ｃ、４１ｃ、５１ｃ…酸化亜鉛層 ３２、４２、５２…ｐ型シリコン結晶質半導体層 ３３、４３、５３…Ｉ型シリコン結晶質半導体層 ３４…ｎ型シリコン半導体層 ３５…裏面反射層 ３６…裏面電極 ６１…チャネリング粒子が少ない条件における、基板凹
凸形状の指標Ｒ／Ｌに対するＩ220／Ｉ111曲線 ６２…チャネリング粒子が多い条件における、基板凹凸
形状の指標Ｒ／Ｌに対するＩ220／Ｉ111曲線11, 21 ... substrate 12, 22 ... surface unevenness layer 13, 23 ... silicon crystalline semiconductor layer 14, 24 ... unevenness size R 15, 25 ... unevenness distance L 16 ... unevenness surface 17 ... virtual substrate surface 31 by visual observation ... Substrates 31a, 41a, 51a ... Glass plates 31b, 41b, 51b ... Tin oxide layers 31c, 41c, 51c ... Zinc oxide layers 32, 42, 52 ... P-type silicon crystalline semiconductor layers 33, 43, 53 ... I-type silicon Crystalline semiconductor layer 34 n-type silicon semiconductor layer 35 back reflection layer 36 back electrode 61 I 220 / I 111 curve 62 relative to index R / L of substrate unevenness under conditions with few channeling particles 62 many channeling particles under the condition, I 220 / I 111 curve for indicators R / L of the substrate irregularities
Claims (7)
１導電型結晶質半導体層、真性結晶質半導体層および第
２導電型半導体層からなる光電変換素子構造とを備え、 前記光電変換素子構造を支持する前記基板の表面は、凹
凸間隔Ｌに対する凹凸大きさＲの比Ｒ／Ｌが０．１〜
１．５の範囲にあるような凹凸によるテクスチャー構造
を有しており、かつ前記第１導電型結晶質半導体層およ
び前記真性結晶質半導体層は、前記基板に垂直な方向に
柱状に成長している結晶粒により主として構成されてい
る、薄膜太陽電池。1. A photoelectric conversion device comprising: a substrate; and a photoelectric conversion element structure including a first conductivity type crystalline semiconductor layer, an intrinsic crystalline semiconductor layer, and a second conductivity type semiconductor layer, which are sequentially stacked on the substrate. The surface of the substrate supporting the element structure has a ratio R / L of the unevenness R to the unevenness L of 0.1 to 0.1%.
The first conductive type crystalline semiconductor layer and the intrinsic crystalline semiconductor layer have a texture structure due to irregularities as in the range of 1.5, and grow in a columnar direction in a direction perpendicular to the substrate. Thin-film solar cell mainly composed of crystal grains.
以上２００ｎｍ未満の厚みを有し、 前記基板の表面から高さ２００ｎｍまでの部分におい
て、前記基板に垂直な方向に柱状に成長している結晶粒
が、当該部分における結晶粒全体の少なくとも５０％以
上を占め、かつ前記基板に垂直な方向に１００ｎｍ以上
の長さを有する、請求項１に記載の薄膜太陽電池。2. The method according to claim 1, wherein the first conductive type crystalline semiconductor layer has a thickness of 1 nm.
In a portion having a thickness of not less than 200 nm and a height from the surface of the substrate to 200 nm, at least 50% or more of the entire crystal grains in the portion in a columnar direction perpendicular to the substrate are grown. The thin-film solar cell according to claim 1, wherein the thin-film solar cell has a length of 100 nm or more in a direction perpendicular to the substrate.
以上１００ｎｍ以下の厚みを有する、請求項１または２
に記載の薄膜太陽電池。3. The first conductive type crystalline semiconductor layer has a thickness of 1 nm.
3. The film according to claim 1, having a thickness of at least 100 nm.
2. The thin-film solar cell according to 1.
透明電極部を前記表面部として有するものである、請求
項１から３のいずれか１項に記載の薄膜太陽電池。4. The thin-film solar cell according to claim 1, wherein the substrate has a transparent electrode portion mainly made of zinc oxide as the surface portion.
記真性結晶質半導体層は主としてシリコンから成り、 前記第１導電型結晶質半導体層および前記真性結晶質半
導体層において前記基板に平行に配向する結晶面は主と
して（１１０）である、請求項１から４のいずれか１項
に記載の薄膜太陽電池。5. The first conductive type crystalline semiconductor layer and the intrinsic crystalline semiconductor layer are mainly made of silicon, and are oriented in parallel with the substrate in the first conductive type crystalline semiconductor layer and the intrinsic crystalline semiconductor layer. The thin-film solar cell according to any one of claims 1 to 4, wherein the crystal plane to be formed is mainly (110).
質半導体層について得られる、（２２０）面のＸ線回折
ピークの積分強度Ｉ220と（１１１）面のＸ線回折ピー
クの積分強度Ｉ111との比Ｉ220／Ｉ111が３以上であ
る、請求項５に記載の薄膜太陽電池。6. An integrated intensity I 220 of an X-ray diffraction peak on a (220) plane and an integrated intensity I 111 of an X-ray diffraction peak on a (111) plane, which are obtained for the intrinsic crystalline semiconductor layer mainly composed of silicon. The thin-film solar cell according to claim 5, wherein the ratio I220 / I111 is 3 or more.
型結晶質半導体層はホウ素を不純物として含有する、請
求項５または６に記載の薄膜太陽電池。7. The thin-film solar cell according to claim 5, wherein the first conductive type crystalline semiconductor layer mainly composed of silicon contains boron as an impurity.
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