JP2004281813A - Manufacturing method for solar cell - Google Patents

Manufacturing method for solar cell Download PDF

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JP2004281813A
JP2004281813A JP2003072526A JP2003072526A JP2004281813A JP 2004281813 A JP2004281813 A JP 2004281813A JP 2003072526 A JP2003072526 A JP 2003072526A JP 2003072526 A JP2003072526 A JP 2003072526A JP 2004281813 A JP2004281813 A JP 2004281813A
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electrode wiring
wiring pattern
solar cell
ink
semiconductor substrate
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Makiko Emoto
真樹子 江本
Naoki Ishikawa
直揮 石川
Michihiko Shirakashi
充彦 白樫
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Ebara Corp
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Ebara Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H01L31/035272—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
    • H01L31/03529—Shape of the potential jump barrier or surface barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar 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
    • Y02E10/547—Monocrystalline silicon PV cells

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Electrodes Of Semiconductors (AREA)
  • Photovoltaic Devices (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a solar cell by which a fine and highly accurate electrode wiring pattern is formed, a formation of excess paste is prevented without using a screen printing technique, and a change in the electrode wiring pattern is made easily. <P>SOLUTION: The electrode wiring pattern 21 is formed on a semiconductor board 13 composing the solar cell using ink scattered with metal ultrafine particles. It is desirable to use an ink jet printer to form the electrode wiring pattern 21. It is also desirable to embed electrode wiring pattern 21 in a groove 42 formed beforehand on the semiconductor board 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、太陽電池の製造方法に係り、特に微細な電極配線パターンの形成方法に関する。
【０００２】
【従来の技術】
太陽電池は、一般にシリコン等の半導体基板の内部にＰＮ接合が形成され、表面側および裏面側に取出し電極が配置されている。半導体基板内部のＰＮ接合に入射した光は、電子とホールの対を形成し、光起電力が形成され、取出し電極から発電電力が取出される。
【０００３】
このような太陽電池においては、電極配線パターンの形成は導電材ペーストをスクリーン印刷により行うことが一般的である。スクリーン印刷による電極配線パターンの形成は、電極配線パターンが開口したスクリーンマスクを使用して、導電材ペーストをスクリーンマスクに開口した電極配線パターンに従って塗布することにより行う。そして、高温で焼成することにより、導電材からなる電極配線パターンが形成される。
【０００４】
【発明が解決しようとする課題】
しかしながら、スクリーン印刷を用いた電極配線パターンの形成は、その微細化に限界がある。即ち、スクリーン印刷に用いるスクリーンマスク自体の精度、およびその位置合わせ精度に限界があり、電極配線パターンの微細化による光電変換効率の向上に限界が生じることになる。また、スクリーン印刷法を用いると、作業上必然的に余剰ペーストが発生し、多量のペーストが無駄になるという問題がある。また、電極配線パターンの形状を変更したい場合に、スクリーンマスクを再度製作する必要があり、設計変更等に際して時間とコストが必要となるという問題がある。
【０００５】
また、一般に電極配線パターンを微細化すると、電極配線の抵抗が上昇し、発電電力出力に損失が生じるという問題がある。このような問題を解決するため、太陽電池を構成する半導体基板上に予め溝を設け、その溝に金属めっき等で銅等の配線材料を埋め込んで電極配線パターンを形成するという方法がある。この方法により、線幅が細く、且つ深さがあるので低抵抗の電極配線パターンが形成されるが、非常に手間がかかるためコスト高となり、量産化が現実には難しいという問題がある。
【０００６】
本発明は上述した事情に鑑みて為されたもので、微細な且つ高精度の電極配線パターンを形成することができる太陽電池の製造方法を提供することを目的とする。また、スクリーン印刷技術を用いることなく、余剰ペーストの発生を防止できるようにした太陽電池の製造方法を提供することを目的とする。さらにまた、電極配線パターンの変更を簡単に行えるようにした太陽電池の製造方法を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明の太陽電池の製造方法は、太陽電池を構成する半導体基板上に、金属超微粒子を分散したインクを使用して電極配線パターンを形成することを特徴とする。
【０００８】
また、本発明の他の態様によれば、前記電極配線パターンの形式は、インクジェットプリンタを用いて行うことを特徴とする。さらにまた、本発明の他の態様によれば、前記電極配線パターンは、前記半導体基板上に予め設けられた溝に埋込まれることを特徴とする。
【０００９】
上述した太陽電池の製造方法によれば、金属超微粒子が分散したインクを使用して、またインクジェットプリンタを用いて電極配線パターンの形成を行うことで、微細且つ高精度の電極配線パターンを半導体基板上に形成することができる。電極配線パターンを微細化することにより、光の照射面積が広がり、発電電力が増加し、光電変換効率を向上することができる。そして、インクジェットプリンタを用いて電極配線パターンを形成するので、従来のスクリーン印刷技術を用いる必要がなくなり、余剰ペーストの発生という問題を解消することができる。これにより、材料の無駄をなくし製造コストを低減することができる。また、電極配線パターン自体はスクリーンマスクによらず、コンピュータ上の設計データをそのまま使用することができるので、電極配線パターンの設計変更が容易であり、試作期間が短縮され、また他品種少量生産への対応も容易である。
【００１０】
さらにまた、太陽電池を構成する半導体基板上に設けられた微細な配線用の溝に、インクジェットプリンタを用いて高精度の導電性インクの埋め込みが可能となるので、上記溝内に電極配線用の導電性金属を容易に埋め込むことができる。これにより、微細幅で深さが比較的深い導電性金属が埋め込まれた電極配線を容易に形成することができ、この電極配線は低抵抗で且つ配線幅が狭く受光面積が広いので、太陽電池の発電出力を向上させることができる。
【００１１】
【発明の実施の形態】
以下、本発明の実施の形態について添付図面を参照しながら説明する。各図中、同一符号は同一または相当部分を示す。
【００１２】
図１は、本発明の太陽電池の製造工程に用いられるインクジェットプリンタを示す。このインクジェットプリンタ１０は、インクカートリッジ１１を備え、このカートリッジ１１内に金属超微粒子が分散したインクを貯留する。このインクは、例えばガス蒸発法により金属蒸気と溶剤蒸気とを接触せしめて金属超微粒子分散液を得て、この分散液に低分子量の溶剤を加えて金属超微粒を沈降させ、得られた沈降物に溶剤および分散剤を添加してインク特性に優れた分散液からなるインクジェット用インクが得られる（特開２００２−１２１４３７号公報参照）。そして、このインクジェット用インクは、インクの供給安定性、インクの液的形成飛翔安定性、プリンタヘッドの高速応答性などのインクジェットプリンタ用インクに要求される特性を満足するものである（同公報参照）。このような金属超微粒子分散液からなるインクジェット用インクは市販されていて、この市販品を利用することができる。
【００１３】
この金属超微粒子としては、粒径が１μｍ未満、好ましくは５００ｎｍ以下、更に好ましくは１０ｎｍ以下の銀、金、銅等の各種金属の微粒子を用いることができる。尚、粒径が小さい金属超微粒子と大きい金属超微粒子を混合したインクを用いてもよい。ここでは、粒径５ｎｍ程度の銀の超微粒子を分散させたインクを用いている。粒径５ｎｍ程度の銀の超微粒子を用いることで、比較的低温の３００℃程度で十分な焼結性が得られ、微細電極配線パターンの形成に好適である。
【００１４】
カートリッジ１１の下面にはインクジェット用ノズル１２が配置され、その直下に配置された半導体基板１３にインクが噴出される。カートリッジ１１は横方向駆動機構１５により紙面の水平方向に移動可能であり、また半導体基板１３は送り方向の移動機構１４により紙面に対して垂直方向に移動可能となっている。したがって、水平方向の移動機構１５および送り方向の移動機構１４の位置決め精度と、噴射ノズル１２の噴射タイミングの精度を制御することで、通常の市販のインクジェットプリンタ並みまたはそれ以上の精密なインクの塗布が可能である。
【００１５】
図２は、半導体基板上に形成した電極配線パターンの一例を示す。この電極配線パターン２１は、半導体基板１３の内部に形成されたＰＮ接合により生じた光起電力を取出すためのものであり、半導体基板の表裏側両面にこのような電極配線パターン２１が設けられている。ここで、半導体基板の寸法は、一例として１０ｃｍ×３．３ｃｍ程度であり、厚さは１００μｍ程度である。半導体基板は、単結晶、多結晶、またはガラス（アモルファス）基板等である。
【００１６】
電極配線パターン２１は、１本の共通電極２１ａとこれに接続する多数の個別電極２１ｂとから構成されている。特に、表面側に用いられる電極配線パターンは、太陽光の入射面積をできるだけ広げるために電極幅Ｗはできるだけ狭いことが好ましい。超微粒子金属を分散させたインクを用い、このインクをインクジェットプリンタにより塗布してパターンを形成することで、半導体基板上に幅５０μｍ以下の微細且つ高精度の電極配線を形成できる。
【００１７】
半導体基板上に印刷された電極配線パターンは、大気中で３００℃、１０分間程度焼成し、インク中に含まれる高分子バインダや溶媒を除去し、金属超微粒子の焼結を行う。焼成により形成された電極配線パターンの導電層は、その抵抗値が数μΩ・ｃｍと非常に低く、且つ引き剥がし強度も高く、半導体基板との密着性も良好である。
【００１８】
インクジェットプリンタを用いた電極配線パターンの印刷は、近年広く普及している市販のインクジェットプリンタと同様に、コンピュータの図面データの出力により行われる。従って、コンピュータの図面データを変更することにより、任意の電極配線パターンを印刷することが可能である。このため、例えば試作開発時には、各種の電極配線パターンを容易に形成することができ、最適な電極配線パターンを短時間で決定することが可能となる。また、生産現場においては、多品種少量生産のような場合に、設計仕様に対応して任意のパターンを形成することができるため、従来技術のスクリーン印刷におけるスクリーンマスクの変更という問題がなくなり、生産の柔軟性が極めて高くなる。
【００１９】
また、粒径が数百〜数ｎｍの金属超微粒子を用いることで、焼成温度を低くすることができ、例えば３００℃程度の温度の炉を用いることで焼成が可能となるので、高温の炉を用いることによる設備および品質面における各種の問題点を解消することができる。なお、金属超微粒子としては、銀の他に金や銅等の各種導電性の高い金属の同様な粒径の超微粒子を用いることができる。
【００２０】
つぎに、本発明の第１の実施形態である金属超微粒子が分散したインクを用いた太陽電池の製造方法について説明する。まず、図３（ａ）に示すように、Ｎ形の太陽電池用半導体基板３１を用意する。そして、表面酸化物を水酸化カリウムなどで洗浄除去後、片面にボロンなどの不純物を熱拡散して、Ｐ＋層３２を形成する。アルミのペーストを塗布後に加熱焼成しても、同様の層を得ることができる。そして、半導体基板の反対側の面に、リンなどの不純物を熱拡散してＮ＋層３３を形成する（図３（ｂ）参照）。
【００２１】
つぎに、図３（ｃ）に示すように、粒径が例えば数ｎｍの銀の超微粒子が分散したインクを用い、図１に示すようにインクジェットプリンタを用いて半導体基板上に電極配線パターン３４を形成する。そして、半導体基板の裏面側にも同様に電極配線パターン３５を形成する。なお、裏面側は太陽光が入射しない場合には配線幅Ｗを狭くする必要がないため、従来技術であるスクリーン印刷方式を使用してもよい。そして、表裏面に電極配線パターンが印刷された半導体基板を焼成炉内で焼成し、超微粒子金属の焼結を行う。上述したように銀等の超微粒子金属のインクを用いて形成された電極配線パターンの導電体は固有抵抗が低く、且つ半導体基板との良好な密着性が得られる。
【００２２】
つぎに、本発明の第２の実施形態である埋め込み形の電極配線を備えた太陽電池の製造方法について、図４を参照して説明する。まず、図４（ａ）に示すように、Ｎ形の太陽電池用の半導体基板４１を用意する。そして、この表面酸化物を水酸化カリウムで洗浄除去する。つぎに、図４（ｂ）に示すように、半導体基板の表面にダイシングまたはＹＡＧレーザを用いて電極配線の形成部に溝４２を形成する。溝の深さは要求仕様に応じて異なるが、例えば数十μｍ程度に形成することが好ましい。溝の幅は電極配線幅と等しくなるので、数十μｍ以下に形成することが好ましい。
【００２３】
つぎに、図４（ｃ）に示すように、半導体基板の表面側にリンなどの不純物を熱拡散してＮ＋層４３を形成する。そして、半導体基板の裏面側にボロン等の不純物を熱拡散して、Ｐ＋層４４を形成する。そして、図４（ｄ）に示すように、インクジェットプリンタを用いて、銀の超微粒子を分散したインクを表面電極用の溝内にこれを埋め込むように塗布して電極層４５を形成する。この時、電極配線部の溝の形成の際に用いた設計データによりインクジェットプリンタの出力パターンを制御するので、精密な位置合わせが可能となり、電極形成用の溝内に銀の超微粒子を分散したインクを正確に埋め込むことができる。そして、半導体基板の裏面側にも電極４６を形成するが、上述したように半導体基板の裏面側を光の入射面として用いない場合には、電極配線の精度が低くてもよいため、スクリーン印刷により行うようにしてもよい。そして、表裏面に電極配線パターンが印刷された半導体基板を焼成炉内で焼成し、超微粒子金属の焼結を行う。上述したように超微粒子金属のインクを用いて形成された電極配線パターンの導電体は固有抵抗が低く、且つ半導体基板との良好な密着性が得られる。
【００２４】
なお、上述の実施形態では半導体基板がＮ形のものを用いる例について説明したが、Ｐ形の半導体基板を用い、Ｎ形の不純物拡散層を形成するようにしても勿論よい。また、表面に反射防止膜やパッシベーション膜を形成してもよく、また表面にテクスチャリングを施すようにしても勿論よい。これらの工程の付加により太陽電池のより高い光電変換効率等が得られる。
【００２５】
なお、上記実施形態は本発明の実施例の一態様を述べたもので、本発明の趣旨を逸脱することなく種々の変形実施例が可能なことは勿論である。
【００２６】
【発明の効果】
上述したように本発明によれば、金属超微粒子が分散したインクを配線材料として使用することで、微細な高精度の配線パターンを形成することができる。これにより、太陽電池を構成する半導体基板の受光面を拡大して、光電変換効率をより高めることができる。また、インクジェットプリンタを用いて電極配線パターンを印刷により形成することで、従来のスクリーン印刷に伴う余剰ペーストの発生が防止され、設計および生産のフレキシビリティが拡大する。また、インクジェットプリンタにより、埋込型の電極配線を容易に形成できるので、太陽電池の埋込配線を量産技術として用いることが可能になる。
【図面の簡単な説明】
【図１】金属超微粒子を分散したインクを用いて電極配線パターンを印刷により形成するインクジェットプリンタを示す模式的な断面図である。
【図２】半導体基板上に形成された電極配線パターンの一例を示す平面図である。
【図３】本発明の第１の実施形態の太陽電池の製造方法を示す拡大断面図である。
【図４】本発明の第２の実施形態の太陽電池の製造方法を示す拡大断面図である。
【符号の説明】
１０ インクジェットプリンタ
１１ インクカートリッジ
１２ インク噴射ノズル
１３ 半導体基板
１４ 送り方向の移動機構
１５ 水平方向の移動機構
２１ 電極配線パターン
３１，４１ 半導体基板
３２，３３，４３，４４ 隔離層
４２ 溝
３４，３５，４５，４６ 電極
Ｗ 配線幅[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a solar cell, and more particularly to a method for forming a fine electrode wiring pattern.
[0002]
[Prior art]
In a solar cell, a PN junction is generally formed inside a semiconductor substrate such as silicon, and extraction electrodes are arranged on a front surface side and a back surface side. The light incident on the PN junction inside the semiconductor substrate forms a pair of an electron and a hole, a photoelectromotive force is formed, and the generated power is extracted from the extraction electrode.
[0003]
In such a solar cell, an electrode wiring pattern is generally formed by screen printing a conductive material paste. The formation of the electrode wiring pattern by screen printing is performed by applying a conductive material paste according to the electrode wiring pattern opened in the screen mask using a screen mask in which the electrode wiring pattern is opened. Then, by firing at a high temperature, an electrode wiring pattern made of a conductive material is formed.
[0004]
[Problems to be solved by the invention]
However, formation of an electrode wiring pattern using screen printing has a limitation in miniaturization. That is, there is a limit to the accuracy of the screen mask itself used for screen printing and the accuracy of its alignment, which limits the improvement of the photoelectric conversion efficiency due to the miniaturization of the electrode wiring pattern. In addition, when the screen printing method is used, there is a problem that surplus paste is inevitably generated in the operation, and a large amount of paste is wasted. In addition, when it is desired to change the shape of the electrode wiring pattern, it is necessary to remanufacture the screen mask, and there is a problem that time and cost are required for a design change or the like.
[0005]
Further, in general, when the electrode wiring pattern is miniaturized, there is a problem that the resistance of the electrode wiring increases and a loss occurs in the generated power output. In order to solve such a problem, there is a method in which a groove is provided in advance on a semiconductor substrate constituting a solar cell, and a wiring material such as copper is buried in the groove by metal plating or the like to form an electrode wiring pattern. According to this method, a low-resistance electrode wiring pattern is formed because the line width is small and the depth is large. However, there is a problem that it is very troublesome, the cost is high, and mass production is actually difficult.
[0006]
The present invention has been made in view of the above circumstances, and has as its object to provide a method for manufacturing a solar cell capable of forming a fine and highly accurate electrode wiring pattern. It is another object of the present invention to provide a method of manufacturing a solar cell that can prevent generation of excess paste without using a screen printing technique. It is still another object of the present invention to provide a method of manufacturing a solar cell in which an electrode wiring pattern can be easily changed.
[0007]
[Means for Solving the Problems]
The method for manufacturing a solar cell according to the present invention is characterized in that an electrode wiring pattern is formed on a semiconductor substrate constituting the solar cell using an ink in which ultrafine metal particles are dispersed.
[0008]
According to another aspect of the present invention, the form of the electrode wiring pattern is performed using an inkjet printer. According to still another aspect of the present invention, the electrode wiring pattern is embedded in a groove provided in advance on the semiconductor substrate.
[0009]
According to the above-described method for manufacturing a solar cell, a fine and highly accurate electrode wiring pattern is formed on a semiconductor substrate by using an ink in which ultrafine metal particles are dispersed and by forming an electrode wiring pattern using an ink jet printer. Can be formed on. By making the electrode wiring pattern finer, the light irradiation area is increased, the generated power is increased, and the photoelectric conversion efficiency can be improved. Then, since the electrode wiring pattern is formed using an ink jet printer, it is not necessary to use a conventional screen printing technique, and the problem of the generation of excess paste can be solved. As a result, waste of materials can be eliminated and manufacturing costs can be reduced. In addition, since the electrode wiring pattern itself can use the design data on the computer without using a screen mask, it is easy to change the design of the electrode wiring pattern, shortening the trial production period, and reducing the production volume to other types. Is also easy.
[0010]
Furthermore, since it is possible to embed a highly accurate conductive ink using an inkjet printer in a fine wiring groove provided on a semiconductor substrate constituting a solar cell, an electrode wiring for the electrode wiring is provided in the groove. The conductive metal can be easily embedded. This makes it possible to easily form an electrode wiring in which a conductive metal having a fine width and a relatively deep depth is embedded. This electrode wiring has a low resistance, a narrow wiring width, and a large light receiving area, and therefore, the solar cell Power generation output can be improved.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the respective drawings, the same reference numerals indicate the same or corresponding parts.
[0012]
FIG. 1 shows an ink jet printer used in the manufacturing process of the solar cell of the present invention. The ink jet printer 10 includes an ink cartridge 11, and stores ink in which ultrafine metal particles are dispersed. This ink is obtained, for example, by bringing a metal vapor and a solvent vapor into contact with each other by a gas evaporation method to obtain a dispersion liquid of ultrafine metal particles, adding a low molecular weight solvent to the dispersion liquid, and precipitating ultrafine metal particles. By adding a solvent and a dispersant to the product, an inkjet ink comprising a dispersion having excellent ink properties can be obtained (see Japanese Patent Application Laid-Open No. 2002-121437). The ink-jet ink satisfies the characteristics required for the ink-jet printer ink, such as the ink supply stability, the liquid formation flight stability of the ink, and the high-speed response of the printer head (see the same publication). ). An inkjet ink comprising such a dispersion liquid of ultrafine metal particles is commercially available, and this commercially available product can be used.
[0013]
As the metal ultrafine particles, fine particles of various metals such as silver, gold and copper having a particle size of less than 1 μm, preferably 500 nm or less, more preferably 10 nm or less can be used. Note that an ink in which ultrafine metal particles having a small particle size and ultrafine metal particles having a large particle size are mixed may be used. Here, an ink in which ultrafine silver particles having a particle size of about 5 nm are dispersed is used. By using ultrafine silver particles having a particle size of about 5 nm, sufficient sinterability can be obtained at a relatively low temperature of about 300 ° C., which is suitable for forming a fine electrode wiring pattern.
[0014]
An ink jet nozzle 12 is arranged on the lower surface of the cartridge 11, and ink is ejected to a semiconductor substrate 13 arranged immediately below the ink jet nozzle 12. The cartridge 11 can be moved in the horizontal direction on the paper by a lateral driving mechanism 15, and the semiconductor substrate 13 can be moved in the vertical direction with respect to the paper by a moving mechanism 14 in the feeding direction. Therefore, by controlling the positioning accuracy of the horizontal moving mechanism 15 and the moving mechanism 14 in the feed direction and the accuracy of the ejection timing of the ejection nozzles 12, it is possible to apply ink with a precision as high as that of an ordinary commercially available inkjet printer. Is possible.
[0015]
FIG. 2 shows an example of an electrode wiring pattern formed on a semiconductor substrate. The electrode wiring pattern 21 is for extracting photovoltaic power generated by a PN junction formed inside the semiconductor substrate 13, and such an electrode wiring pattern 21 is provided on both front and back surfaces of the semiconductor substrate. I have. Here, the dimensions of the semiconductor substrate are, for example, about 10 cm × 3.3 cm, and the thickness is about 100 μm. The semiconductor substrate is a single crystal, polycrystal, glass (amorphous) substrate, or the like.
[0016]
The electrode wiring pattern 21 includes one common electrode 21a and a number of individual electrodes 21b connected thereto. In particular, in the electrode wiring pattern used on the front surface side, it is preferable that the electrode width W is as narrow as possible in order to increase the incident area of sunlight as much as possible. By using an ink in which ultrafine metal particles are dispersed and applying the ink by an ink jet printer to form a pattern, a fine and highly accurate electrode wiring having a width of 50 μm or less can be formed on a semiconductor substrate.
[0017]
The electrode wiring pattern printed on the semiconductor substrate is baked in air at 300 ° C. for about 10 minutes to remove the polymer binder and the solvent contained in the ink, and to sinter the ultrafine metal particles. The conductive layer of the electrode wiring pattern formed by firing has a very low resistance value of several μΩ · cm, high peeling strength, and good adhesion to a semiconductor substrate.
[0018]
Printing of an electrode wiring pattern using an ink jet printer is performed by outputting drawing data of a computer, similarly to a commercially available ink jet printer that has been widely used in recent years. Therefore, an arbitrary electrode wiring pattern can be printed by changing the drawing data of the computer. Therefore, for example, at the time of prototype development, various electrode wiring patterns can be easily formed, and an optimum electrode wiring pattern can be determined in a short time. Also, at the production site, in the case of high-mix low-volume production, an arbitrary pattern can be formed in accordance with the design specifications, so that the problem of changing the screen mask in conventional screen printing is eliminated. Flexibility becomes extremely high.
[0019]
In addition, by using metal ultrafine particles having a particle diameter of several hundreds to several nm, the firing temperature can be lowered. For example, by using a furnace at a temperature of about 300 ° C., firing becomes possible. Can solve various problems in equipment and quality. In addition, as the metal ultrafine particles, ultrafine particles having a similar particle diameter of various highly conductive metals such as gold and copper other than silver can be used.
[0020]
Next, a method for manufacturing a solar cell using an ink in which ultrafine metal particles are dispersed according to the first embodiment of the present invention will be described. First, as shown in FIG. 3A, an N-type solar cell semiconductor substrate 31 is prepared. Then, after the surface oxide is removed by washing with potassium hydroxide or the like, impurities such as boron are thermally diffused on one side to form the P + layer 32. A similar layer can be obtained by heating and baking after applying the aluminum paste. Then, an impurity such as phosphorus is thermally diffused on the surface on the opposite side of the semiconductor substrate to form an N + layer 33 (see FIG. 3B).
[0021]
Next, as shown in FIG. 3 (c), using an ink in which ultrafine silver particles having a particle size of, for example, several nm are dispersed, and using an ink-jet printer as shown in FIG. To form Then, an electrode wiring pattern 35 is similarly formed on the back side of the semiconductor substrate. When the sunlight does not enter the rear surface side, it is not necessary to reduce the wiring width W. Therefore, a screen printing method which is a conventional technique may be used. Then, the semiconductor substrate having the electrode wiring pattern printed on the front and back surfaces is fired in a firing furnace to sinter the ultrafine metal. As described above, the conductor of the electrode wiring pattern formed using the ink of ultrafine metal such as silver has low specific resistance and good adhesion to the semiconductor substrate.
[0022]
Next, a method for manufacturing a solar cell having an embedded electrode wiring according to a second embodiment of the present invention will be described with reference to FIG. First, as shown in FIG. 4A, a semiconductor substrate 41 for an N-type solar cell is prepared. Then, the surface oxide is washed and removed with potassium hydroxide. Next, as shown in FIG. 4B, a groove 42 is formed on the surface of the semiconductor substrate by using dicing or a YAG laser at a portion where the electrode wiring is to be formed. The depth of the groove varies depending on the required specifications, but is preferably formed, for example, to about several tens of μm. Since the width of the groove is equal to the width of the electrode wiring, it is preferable to form the groove to several tens μm or less.
[0023]
Next, as shown in FIG. 4C, an impurity such as phosphorus is thermally diffused on the surface side of the semiconductor substrate to form an N + layer 43. Then, impurities such as boron are thermally diffused to the back surface side of the semiconductor substrate to form the P + layer 44. Then, as shown in FIG. 4D, an ink in which ultrafine silver particles are dispersed is applied by using an ink jet printer so as to fill the grooves for the surface electrodes, thereby forming the electrode layer 45. At this time, since the output pattern of the ink jet printer is controlled by the design data used in forming the groove of the electrode wiring portion, precise alignment becomes possible, and ultrafine silver particles are dispersed in the groove for forming the electrode. Ink can be embedded accurately. The electrode 46 is also formed on the back surface side of the semiconductor substrate. However, when the back surface side of the semiconductor substrate is not used as a light incident surface as described above, the accuracy of the electrode wiring may be low. May be performed. Then, the semiconductor substrate having the electrode wiring pattern printed on the front and back surfaces is fired in a firing furnace to sinter the ultrafine metal. As described above, the conductor of the electrode wiring pattern formed using the ink of ultrafine metal has low specific resistance and good adhesion to the semiconductor substrate.
[0024]
In the above-described embodiment, an example in which an N-type semiconductor substrate is used has been described. However, an N-type impurity diffusion layer may be formed using a P-type semiconductor substrate. Further, an anti-reflection film or a passivation film may be formed on the surface, or the surface may be textured. By adding these steps, higher photoelectric conversion efficiency and the like of the solar cell can be obtained.
[0025]
It should be noted that the above-described embodiment describes one mode of the embodiment of the present invention, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.
[0026]
【The invention's effect】
As described above, according to the present invention, a fine and highly accurate wiring pattern can be formed by using an ink in which ultrafine metal particles are dispersed as a wiring material. Thereby, the light receiving surface of the semiconductor substrate constituting the solar cell can be enlarged, and the photoelectric conversion efficiency can be further increased. Further, by forming an electrode wiring pattern by printing using an ink jet printer, the generation of excess paste due to conventional screen printing is prevented, and the flexibility of design and production is expanded. In addition, since the embedded electrode wiring can be easily formed by the ink jet printer, the embedded wiring of the solar cell can be used as a mass production technique.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an ink-jet printer that forms an electrode wiring pattern by printing using ink in which ultrafine metal particles are dispersed.
FIG. 2 is a plan view showing an example of an electrode wiring pattern formed on a semiconductor substrate.
FIG. 3 is an enlarged sectional view illustrating the method for manufacturing the solar cell according to the first embodiment of the present invention.
FIG. 4 is an enlarged sectional view illustrating a method for manufacturing a solar cell according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Ink-jet printer 11 Ink cartridge 12 Ink ejection nozzle 13 Semiconductor substrate 14 Moving mechanism 15 in the feeding direction Horizontal moving mechanism 21 Electrode wiring patterns 31, 41 Semiconductor substrates 32, 33, 43, 44 Isolation layer 42 Grooves 34, 35, 45 , 46 Electrode W Wiring width

Claims (6)

太陽電池を構成する半導体基板上に、金属超微粒子を分散したインクを使用して電極配線パターンを形成することを特徴とする太陽電池の製造方法。A method for manufacturing a solar cell, comprising forming an electrode wiring pattern on a semiconductor substrate constituting a solar cell using ink in which ultrafine metal particles are dispersed. 前記電極配線パターンの形成は、インクジェットプリンタを用いて行うことを特徴とする請求項１記載の太陽電池の製造方法。The method according to claim 1, wherein the forming of the electrode wiring pattern is performed using an inkjet printer. 前記電極配線パターンは、前記半導体基板上に予め設けられた溝に埋込まれることを特徴とする請求項１記載の太陽電池の製造方法。The method according to claim 1, wherein the electrode wiring pattern is embedded in a groove provided in advance on the semiconductor substrate. 前記半導体基板として、単結晶、多結晶、またはガラス（アモルファス）基板を用いることを特徴とする請求項１記載の太陽電池の製造方法。The method according to claim 1, wherein a single crystal, polycrystal, or glass (amorphous) substrate is used as the semiconductor substrate. 前記金属超微粒子として、粒径が１μｍ未満、好ましくは５００ｎｍ以下、更に好ましくは１０ｎｍ以下の銀の超微粒子を用いることを特徴とする請求項１記載の太陽電池の製造方法。The method for manufacturing a solar cell according to claim 1, wherein ultrafine silver particles having a particle size of less than 1 μm, preferably 500 nm or less, more preferably 10 nm or less are used as the metal ultrafine particles. 請求項５記載の金属超微粒子と、粒径が１μｍ以上のものを混合したインクを使用して電極パターンを形成することを特徴とする太陽電池の製造方法。A method for manufacturing a solar cell, comprising forming an electrode pattern using an ink obtained by mixing the ultrafine metal particles according to claim 5 with a particle having a particle size of 1 μm or more.
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