JP4726354B2 - Paste composition and solar cell using the same - Google Patents

Paste composition and solar cell using the same Download PDF

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JP4726354B2
JP4726354B2 JP2001251166A JP2001251166A JP4726354B2 JP 4726354 B2 JP4726354 B2 JP 4726354B2 JP 2001251166 A JP2001251166 A JP 2001251166A JP 2001251166 A JP2001251166 A JP 2001251166A JP 4726354 B2 JP4726354 B2 JP 4726354B2
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paste composition
mass
boron
boron compound
organic
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JP2003069056A (en
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隆 和辻
高潮 頼
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TOYO ALMINIUM KABUSHIKI KAISHA
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TOYO ALMINIUM KABUSHIKI KAISHA
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/2225Diffusion sources

Description

【0001】
【発明の属する技術分野】
この発明は、一般的にはペースト組成物およびそれを用いた太陽電池に関し、特定的には、結晶系シリコン太陽電池を構成するp型シリコン半導体基板の上に電極を形成する際に用いられるペースト組成物、およびそれを用いた太陽電池に関するものである。
【0002】
【従来の技術】
p型シリコン半導体基板の上に電極が形成された電子部品として、太陽電池が知られている。図1に示すように、太陽電池は、厚みが300〜400μmのp型シリコン半導体基板1を用いて構成される。p型シリコン半導体基板1の受光面側には、厚みが0.3〜0.5μmのn型不純物層2と、その上に反射防止膜3とグリッド電極4が形成されている。
【0003】
また、p型シリコン半導体基板1の裏面側には、裏面電極層5が形成されている。裏面電極層5は、アルミニウム粉末、ガラスフリットおよび有機質ビヒクルからなるペースト組成物をスクリーン印刷等によって塗布し、乾燥した後、660℃(アルミニウムの融点)以上の温度にて焼成することによって形成されている。この焼成の際にアルミニウムがp型シリコン半導体基板1の内部に拡散することにより、裏面電極層5とp型シリコン半導体基板1との間にAl−Si合金層6が形成されると同時に、アルミニウム原子の拡散による拡散層としてp+層7が形成される。このp+層7の存在により、生成キャリアの収集効率が向上するBSF(Back Surface Field)効果が得られる。実際の裏面電極は、焼成後の裏面電極層5、Al−Si合金層6およびp+層7の三層をそのままで使用する場合と、電気抵抗を低減させるために、焼成後の裏面電極層5、または焼成後の裏面電極層5とAl−Si合金層6を化学的方法等によって除去した後、銀や銅からなる電極層を形成して使用する場合がある。いずれの場合においても、p+層7がBSF効果を発揮する。
【0004】
【発明が解決しようとする課題】
近年、太陽電池の出力を向上させることが強く要求されている。太陽電池の出力の向上を図るための一つの対策として、BSF効果の向上や電極の電気抵抗の低減が望まれている。この目的のために、上記のp+層を形成するために用いられるペースト組成物について種々検討されている。
【0005】
たとえば、特開2000−90734号公報には、アルミニウム粉末、ガラスフリット、有機質ビヒクルに加えて、さらにアルミニウム含有有機化合物を含有する導電性ペーストが開示されている。また、特開平8−148447号公報には、ペースト全体に対する配合比率が60〜90wt%の範囲内にある固形分と、10〜40wt%の範囲内にある有機質ビヒクルからなり、かつ、固形分は、固形分全体に対する配合比率が85〜98.5wt%の範囲内にある銀粉末と、0.5〜10wt%の範囲内にあるアルミニウム粉末と、1〜10wt%の範囲内にあるガラスフリットを含んだものであることを特徴とした導電性ペーストが開示されている。しかしながら、これらの公報で開示されたペーストを用いても、太陽電池の出力のさらなる向上という要求を充分満足するほど、BSF効果の向上や電極の電気抵抗の低減を達成できていないのが現状である。
【0006】
そこで、この発明の目的は、BSF効果をさらに向上させることが可能なペースト組成物と、その組成物を用いて形成された電極を備えた太陽電池を提供することである。
【0007】
【課題を解決するための手段】
本発明者らは、鋭意研究を重ねた結果、特定の組成を有するペースト組成物を使用することにより、上記の目的を達成できることを見出した。この知見に基づいて、本発明に従ったペースト組成物は、次のような特徴を備えている。
【0008】
この発明に従ったペースト組成物は、p型シリコン半導体基板の上に電極を形成するためのペースト組成物であって、アルミニウム粉末と、有機質ビヒクルと、ガラスフリットと、無機ホウ素化合物および有機ホウ素化合物からなる群から選ばれた少なくとも1種とを含む。
【0009】
好ましくは、この発明のペースト組成物は、無機ホウ素化合物および有機ホウ素化合物からなる群から選ばれた少なくとも1種を、ホウ素換算で0.01質量%以上5.0質量%以下含む。
【0010】
さらに好ましくは、この発明のペースト組成物は、アルミニウム粉末を60質量%以上75質量%以下、ガラスフリットを0.3質量%以上5.0質量%以下、有機質ビヒクルを20質量%以上30質量%以下、無機ホウ素化合物および有機ホウ素化合物からなる群から選ばれた少なくとも1種を、ホウ素換算で0.01質量%以上5.0質量%以下含む。
【0011】
この発明のペースト組成物において、無機ホウ素化合物は、炭化物、酸化物、塩化物、臭化物、ヨウ化物、弗化物、窒化物およびホウ酸から選ばれた少なくとも1種であるのが好ましい。
【0012】
また、この発明のペースト組成物において、有機ホウ素化合物は、トリメトキシボロン、トリエトキシボロン、トリプロポキシボロンおよびトリプトキシボロンからなる群から選ばれた少なくとも1種であるのが好ましい。
【0013】
この発明に従った太陽電池は、上述の特徴を有するペースト組成物をp型シリコン半導体基板の上に塗布した後、焼成することにより形成した電極を備える。
【0014】
【発明の実施の形態】
この発明のペースト組成物は、アルミニウム粉末、ガラスフリット、有機質ビヒクルに加えて、さらに、無機ホウ素化合物および有機ホウ素化合物からなる群より選ばれた少なくとも1種のホウ素含有物を含有することを特徴としている。従来の組成にホウ素含有物を加えることにより、BSF効果をさらに向上させることが可能な電極形成材料としてのペースト組成物が得られる。
【0015】
上記のホウ素含有物を含有させることにより、BSF効果が向上する理由は明らかではないが、次のように推測される。ホウ素原子の存在によって、ペーストの焼成時にアルミニウム原子がp型シリコン半導体基板の表面から内部に拡散しやすくなるので、BSF効果が向上する。あるいは、ペーストの焼成時にホウ素原子そのものがp型シリコン半導体基板の内部に拡散することによって、BSF効果が向上する。
【0016】
本発明のペースト組成物に含められる無機ホウ素化合物としては、炭化物、酸化物、塩化物、臭化物、ヨウ化物、弗化物、窒化物またはホウ酸が挙げられるが、これらの化合物に限定されるものではない。また、本発明のペースト組成物に含められる有機ホウ素化合物としては、トリメトキシボロン、トリエトキシボロン、トリプロポキシボロンまたはトリプトキシボロンが挙げられるが、これらの化合物に限定されるものではない。
【0017】
本発明のペースト組成物に含められる無機ホウ素化合物および有機ホウ素化合物からなる群より選ばれた少なくとも1種のホウ素含有物の含有量は、ホウ素換算で0.01質量%以上5.0質量%以下であることが好ましい。ホウ素含有物の含有量が0.01質量%未満では、BSF効果を高めるほどの充分な添加効果を得ることができない。ホウ素含有物の含有量が5.0質量%を超えると、スクリーン印刷等におけるペーストの塗布性が低下する。
【0018】
また、本発明のペースト組成物に含められるアルミニウム粉末の含有量は、60質量%以上75質量%以下であることが好ましい。アルミニウム粉末の含有量が60質量%未満では、焼成後の裏面電極の電気抵抗が高くなり、太陽電池の特性低下を招くおそれがある。アルミニウム粉末の含有量が75質量%を超えると、スクリーン印刷等におけるペーストの塗布性が低下する。
【0019】
さらに、本発明のペースト組成物に含められるガラスフリットの含有量は、0.3質量%以上5.0質量%以下であることが好ましい。ガラスフリットは、焼成後の裏面電極とp型シリコン半導体基板との密着性を向上させるために添加されているものである。ガラスフリットの含有量が0.3質量%未満では、焼成後の裏面電極の接着強度が低下する。ガラスフリットの含有量が5.0質量%を超えれば、ガラスの偏析が生じるおそれがある。
【0020】
本発明のペースト組成物に含まれるガラスフリットとしては、SiO2-Bi23−PbO系の他に、B23−SiO2−Bi23系、B23−SiO2−ZnO系、B23−SiO2−PbO系等のホウ素を含んだものも挙げられる。しかし、本発明のペースト組成物では、ガラスフリット中のホウ素の有無にかかわらず、上記のホウ素含有物を含有させることによって、BSF効果を確実に向上させることができる。
【0021】
本発明のペースト組成物に含められる有機質ビヒクルとしては、エチルセルロース、アクリル樹脂、アルキッド樹脂等を溶剤に溶解したものが使用される。有機質ビヒクルの含有量は20質量%以上30質量%以下であることが好ましい。有機質ビヒクルの含有量が20質量%未満では、ペーストの印刷性が低下する。有機質ビヒクルの含有量が30質量%を超えれば、焼成後の裏面電極の密度が低下し、電極の電気抵抗が増大する。
【0022】
【実施例】
以下、本発明の一つの実施例について説明する。
【0023】
まず、アルミニウム粉末を60〜75質量%、ガラスフリットを0.3〜5.0質量%、有機質ビヒクルを20〜30質量%の範囲内で含有するとともに、ホウ素粉末、無機ホウ素化合物または有機ホウ素化合物のホウ素(B)含有物を表1に示す割合(ホウ素(B)換算添加量)で含有する各種のペースト組成物を作製した。
【0024】
具体的には、エチルセルロースをグリコールエーテル系有機溶剤に溶解した有機質ビヒクルに、アルミニウム粉末とB23−SiO2−PbO系のガラスフリットを加え、さらに表1に示す各種のホウ素含有物を加えて、周知の混合機にて混合し、ペースト組成物を得た。
【0025】
ここで、アルミニウム粉末は、p型シリコン半導体基板との反応性の確保、塗布性、および塗布膜の均一性の点から、平均粒径2〜20μmの球形、または球形に近い形状を有する粒子からなる粉末を用いるのが好ましい。上記のペースト組成物の作製で用いたアルミニウム(Al)粉末の平均粒径を表1に示す。
【0026】
表1に示すホウ素(B)含有物として、ホウ素(B)粉末は試薬の250メッシュ通過品、ホウ酸は試薬の250メッシュ通過品、酸化ホウ素は試薬の250メッシュ通過品、炭化ホウ素は共立マテリアル株式会社製のB4C−J5、トリエトキシボロンは試薬を用いた。
【0027】
上記の各種のペースト組成物を厚みが300μm、大きさが2インチ(50.8mm)×2インチ(50.8mm)のp型シリコン半導体基板に180メッシュのスクリーン印刷版を用いて塗布・印刷し、乾燥させた。
【0028】
塗布量は、焼成後の電極の厚みが40〜60μmになるように設定した。スクリーン印刷の評価は、シリコン(Si)基板に100%印刷できれば○、スクリーン印刷版にペースト組成物が残留し、シリコン基板への印刷面積が100%未満から95%の範囲であれば△、95%未満であれば×とした。この評価は表1のスクリーン印刷性で示している。
【0029】
ペーストが印刷されたp型シリコン半導体基板を乾燥した後、赤外線焼成炉にて、空気雰囲気で400℃/分の加熱速度で加熱し、710〜720℃の温度で30秒間保持する条件で焼成した。焼成後、冷却することにより、図1に示すようにp型シリコン半導体基板1に裏面電極層5を形成した構造を得た。
【0030】
その後、裏面電極層を形成したp型シリコン半導体基板を塩酸水溶液に浸漬することによって、裏面電極層5とAl−Si合金層6を溶解除去した後、p+層7が形成されたp型シリコン半導体基板の表面抵抗を、4探針式表面抵抗測定器にて測定した。p+層7の表面抵抗とBSF効果との間には相関関係があり、その表面抵抗が小さいほど、BSF効果が高いとされている。シリコン(Si)基板のp+層の表面抵抗を表1に示す。
【0031】
【表1】

Figure 0004726354
【0032】
表1に示す結果から、アルミニウム粉末の平均粒径に関係なく、無添加の従来例においては焼成後のp+層の表面抵抗が12.0Ω□以上であったのに対して、ホウ素含有物を0.01質量%以上添加した場合にはp+層の表面抵抗を10.0Ω□以下まで低減させることができる。また、ホウ素含有物は、ホウ酸、酸化ホウ素またはトリエトキシボロンのいずれの形態で添加しても上記の効果を達成できることがわかる。
【0033】
以上に開示された実施の形態や実施例はすべての点で例示であって制限的なものではないと考慮されるべきである。本発明の範囲は、以上の実施の形態や実施例ではなく、特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての修正や変形を含むものと意図される。
【0034】
【発明の効果】
以上のように、この発明によれば、ホウ素含有物を含む本発明のペースト組成物を塗布したp型シリコン半導体基板を焼成することにより、p+層の表面抵抗を低減させることができるので、BSF効果をより一層高めることができ、結果として太陽電池の出力を向上させることができる。
【図面の簡単な説明】
【図1】 この発明が適用される太陽電池の断面構造を模式的に示す図である。
【符号の説明】
1:p型シリコン半導体基板、2:n型不純物層、3:反射防止膜、4:グリッド電極、5:裏面電極層、6:Al−Si合金層、7:p+層。[0001]
BACKGROUND OF THE INVENTION
The present invention relates generally to a paste composition and a solar cell using the same, and more specifically, a paste used when forming an electrode on a p-type silicon semiconductor substrate constituting a crystalline silicon solar cell. The present invention relates to a composition and a solar cell using the composition.
[0002]
[Prior art]
A solar cell is known as an electronic component having electrodes formed on a p-type silicon semiconductor substrate. As shown in FIG. 1, the solar cell is configured using a p-type silicon semiconductor substrate 1 having a thickness of 300 to 400 μm. On the light receiving surface side of the p-type silicon semiconductor substrate 1, an n-type impurity layer 2 having a thickness of 0.3 to 0.5 μm, and an antireflection film 3 and a grid electrode 4 are formed thereon.
[0003]
A back electrode layer 5 is formed on the back side of the p-type silicon semiconductor substrate 1. The back electrode layer 5 is formed by applying a paste composition made of aluminum powder, glass frit and organic vehicle by screen printing or the like, drying, and firing at a temperature of 660 ° C. (melting point of aluminum) or higher. Yes. During the firing, aluminum diffuses into the p-type silicon semiconductor substrate 1, thereby forming an Al—Si alloy layer 6 between the back electrode layer 5 and the p-type silicon semiconductor substrate 1. A p + layer 7 is formed as a diffusion layer by atomic diffusion. The presence of the p + layer 7 provides a BSF (Back Surface Field) effect that improves the collection efficiency of generated carriers. The actual back electrode includes three cases of the back electrode layer 5 after firing, the Al—Si alloy layer 6 and the p + layer 7 as they are, and the back electrode layer after firing in order to reduce electric resistance. 5 or after the back electrode layer 5 and the Al—Si alloy layer 6 after firing are removed by a chemical method or the like, an electrode layer made of silver or copper may be formed and used. In any case, the p + layer 7 exhibits the BSF effect.
[0004]
[Problems to be solved by the invention]
In recent years, there has been a strong demand for improving the output of solar cells. As one measure for improving the output of the solar cell, improvement of the BSF effect and reduction of the electric resistance of the electrode are desired. For this purpose, various studies have been made on paste compositions used to form the p + layer.
[0005]
For example, Japanese Patent Application Laid-Open No. 2000-90734 discloses a conductive paste containing an aluminum-containing organic compound in addition to aluminum powder, glass frit, and an organic vehicle. Japanese Patent Application Laid-Open No. 8-148447 includes a solid content in the range of 60 to 90 wt% with respect to the total paste and an organic vehicle in the range of 10 to 40 wt%, and the solid content is A silver powder having a blending ratio with respect to the whole solid content in the range of 85 to 98.5 wt%, an aluminum powder in the range of 0.5 to 10 wt%, and a glass frit in the range of 1 to 10 wt%. A conductive paste characterized in that it is contained is disclosed. However, even if the pastes disclosed in these publications are used, the BSF effect cannot be improved and the electrical resistance of the electrode cannot be reduced to the extent that the requirement for further improvement of the output of the solar cell is sufficiently satisfied. is there.
[0006]
Accordingly, an object of the present invention is to provide a paste composition capable of further improving the BSF effect and a solar cell including an electrode formed using the composition.
[0007]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that the above object can be achieved by using a paste composition having a specific composition. Based on this finding, the paste composition according to the present invention has the following characteristics.
[0008]
The paste composition according to the present invention is a paste composition for forming an electrode on the p-type silicon semiconductor substrate, aluminum powder, an organic vehicle, and glass frit, no machine boron compound and organic boron And at least one selected from the group consisting of compounds.
[0009]
Preferably, the paste composition of the present invention, at least one selected from the group consisting of non-aircraft boron compound and organic boron compounds include boron terms 0.01 mass% to 5.0 mass% or less.
[0010]
More preferably, in the paste composition of the present invention, the aluminum powder is 60% by mass to 75% by mass, the glass frit is 0.3% by mass to 5.0% by mass, and the organic vehicle is 20% by mass to 30% by mass. hereinafter, at least one selected from the group consisting of non-aircraft boron compound and organic boron compounds include boron terms 0.01 mass% to 5.0 mass% or less.
[0011]
In the paste composition of the present invention, the inorganic boron compound is preferably at least one selected from carbide, oxide, chloride, bromide, iodide, fluoride, nitride, and boric acid.
[0012]
In the paste composition of the present invention, the organic boron compound is preferably at least one selected from the group consisting of trimethoxyboron, triethoxyboron, tripropoxyboron, and tryptoxyboron.
[0013]
A solar cell according to the present invention includes an electrode formed by applying a paste composition having the above-described characteristics onto a p-type silicon semiconductor substrate and then baking it.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Paste composition of the present invention, aluminum powder, glass frit, in addition to the organic vehicle, the further, in that it contains at least one boron-containing compound selected from the group consisting of non-aircraft boron compound and organic boron compound It is a feature. By adding a boron-containing material to a conventional composition, a paste composition can be obtained as an electrode forming material that can further improve the BSF effect.
[0015]
The reason why the BSF effect is improved by containing the boron-containing material is not clear, but is presumed as follows. The presence of boron atoms facilitates diffusion of aluminum atoms from the surface of the p-type silicon semiconductor substrate to the inside during baking of the paste, thereby improving the BSF effect. Alternatively, when the paste is baked, the boron atoms themselves diffuse into the p-type silicon semiconductor substrate, thereby improving the BSF effect.
[0016]
Examples of inorganic boron compounds included in the paste composition of the present invention include carbides, oxides, chlorides, bromides, iodides, fluorides, nitrides, and boric acid, but are not limited to these compounds. Absent. Further, examples of the organic boron compound included in the paste composition of the present invention include trimethoxyboron, triethoxyboron, tripropoxyboron, and tryptoxyboron, but are not limited to these compounds.
[0017]
Content of at least one boron-containing compound included is that no machine boron compounds and selected from the group consisting of organic boron compound in the paste composition of the present invention, 5.0 mass 0.01 mass% in terms of boron % Or less is preferable. When the content of the boron-containing material is less than 0.01% by mass, it is not possible to obtain a sufficient addition effect that enhances the BSF effect. When the content of the boron-containing material exceeds 5.0% by mass, the applicability of the paste in screen printing or the like decreases.
[0018]
Moreover, it is preferable that content of the aluminum powder included in the paste composition of this invention is 60 mass% or more and 75 mass% or less. If the content of the aluminum powder is less than 60% by mass, the electrical resistance of the back electrode after firing becomes high, and there is a risk of degrading the characteristics of the solar cell. When the content of the aluminum powder exceeds 75% by mass, the applicability of the paste in screen printing or the like decreases.
[0019]
Furthermore, the content of the glass frit included in the paste composition of the present invention is preferably 0.3% by mass or more and 5.0% by mass or less. Glass frit is added to improve the adhesion between the back electrode after firing and the p-type silicon semiconductor substrate. When the glass frit content is less than 0.3% by mass, the adhesive strength of the back electrode after firing is lowered. If the glass frit content exceeds 5.0% by mass, segregation of the glass may occur.
[0020]
The glass frit contained in the paste composition of the present invention includes, in addition to the SiO 2 —Bi 2 O 3 —PbO series, B 2 O 3 —SiO 2 —Bi 2 O 3 series, B 2 O 3 —SiO 2 — Examples thereof include those containing boron such as ZnO-based and B 2 O 3 —SiO 2 —PbO-based. However, in the paste composition of the present invention, regardless of the presence or absence of boron in the glass frit, the BSF effect can be reliably improved by containing the above boron-containing material.
[0021]
As the organic vehicle included in the paste composition of the present invention, one obtained by dissolving ethyl cellulose, acrylic resin, alkyd resin or the like in a solvent is used. The content of the organic vehicle is preferably 20% by mass or more and 30% by mass or less. If the content of the organic vehicle is less than 20% by mass, the printability of the paste is lowered. If the content of the organic vehicle exceeds 30% by mass, the density of the back electrode after firing decreases, and the electrical resistance of the electrode increases.
[0022]
【Example】
Hereinafter, one embodiment of the present invention will be described.
[0023]
First, the aluminum powder is contained in the range of 60 to 75% by mass, the glass frit in the range of 0.3 to 5.0% by mass, the organic vehicle in the range of 20 to 30% by mass, and the boron powder, inorganic boron compound or organic boron compound. Various paste compositions containing the boron (B) -containing material in the proportions shown in Table 1 (boron (B) equivalent addition amount) were prepared.
[0024]
Specifically, aluminum powder and B 2 O 3 —SiO 2 —PbO glass frit are added to an organic vehicle in which ethyl cellulose is dissolved in a glycol ether organic solvent, and various boron-containing materials shown in Table 1 are added. The mixture was mixed with a known mixer to obtain a paste composition.
[0025]
Here, the aluminum powder is formed from particles having an average particle diameter of 2 to 20 μm or a shape close to a sphere from the viewpoint of ensuring reactivity with the p-type silicon semiconductor substrate, coating properties, and uniformity of the coating film. It is preferable to use the following powder. Table 1 shows the average particle diameter of the aluminum (Al) powder used in the preparation of the paste composition.
[0026]
As the boron (B) -containing materials shown in Table 1, boron (B) powder is a 250-mesh product of reagent, boric acid is a 250-mesh product of reagent, boron oxide is a 250-mesh product of reagent, and boron carbide is a Kyoritsu material. Reagents were used for B4C-J5 and triethoxyboron manufactured by Co., Ltd.
[0027]
The above-mentioned various paste compositions were applied and printed on a p-type silicon semiconductor substrate having a thickness of 300 μm and a size of 2 inches (50.8 mm) × 2 inches (50.8 mm) using a 180 mesh screen printing plate. , Dried.
[0028]
The coating amount was set so that the thickness of the electrode after firing was 40 to 60 μm. Evaluation of screen printing is as follows: ○ if the 100% printing can be performed on the silicon (Si) substrate; Δ if the paste composition remains on the screen printing plate and the printing area on the silicon substrate is less than 100% to 95%. If it was less than%, it was set as x. This evaluation is shown by the screen printability in Table 1.
[0029]
After drying the p-type silicon semiconductor substrate on which the paste was printed, it was heated in an infrared baking furnace at a heating rate of 400 ° C./min in an air atmosphere and held at a temperature of 710 to 720 ° C. for 30 seconds. . After firing, cooling was performed to obtain a structure in which the back electrode layer 5 was formed on the p-type silicon semiconductor substrate 1 as shown in FIG.
[0030]
Thereafter, the p-type silicon semiconductor substrate on which the back electrode layer is formed is immersed in an aqueous hydrochloric acid solution to dissolve and remove the back electrode layer 5 and the Al—Si alloy layer 6, and then the p-type silicon on which the p + layer 7 is formed. The surface resistance of the semiconductor substrate was measured with a 4-probe surface resistance measuring instrument. There is a correlation between the surface resistance of the p + layer 7 and the BSF effect, and the smaller the surface resistance, the higher the BSF effect. Table 1 shows the surface resistance of the p + layer of the silicon (Si) substrate.
[0031]
[Table 1]
Figure 0004726354
[0032]
From the results shown in Table 1, regardless of the average particle diameter of the aluminum powder, in the conventional additive-free example, the surface resistance of the p + layer after firing was 12.0Ω □ or more, whereas the boron-containing material When 0.01 mass% or more is added, the surface resistance of the p + layer can be reduced to 10.0 Ω □ or less. Moreover, boron-containing compound is boric acid, it can be seen that also achieve the effect of the added in any form of boron oxide or triethoxy boron.
[0033]
It should be considered that the embodiments and examples disclosed above are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .
[0034]
【The invention's effect】
As described above, according to the present invention, the surface resistance of the p + layer can be reduced by firing the p-type silicon semiconductor substrate coated with the paste composition of the present invention containing a boron-containing material. The BSF effect can be further enhanced, and as a result, the output of the solar cell can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a cross-sectional structure of a solar cell to which the present invention is applied.
[Explanation of symbols]
1: p-type silicon semiconductor substrate, 2: n-type impurity layer, 3: antireflection film, 4: grid electrode, 5: back electrode layer, 6: Al—Si alloy layer, 7: p + layer.

Claims (6)

p型シリコン半導体基板の上に電極を形成するためのペースト組成物であって、
アルミニウム粉末と、有機質ビヒクルと、ガラスフリットと、無機ホウ素化合物および有機ホウ素化合物からなる群から選ばれた少なくとも1種とを含む、ペースト組成物。
A paste composition for forming an electrode on a p-type silicon semiconductor substrate,
Comprising aluminum powder, an organic vehicle, and glass frit and at least one selected from the group consisting of non-aircraft boron compound and organic boron compound, the paste composition.
機ホウ素化合物および有機ホウ素化合物からなる群から選ばれた少なくとも1種を、ホウ素換算で0.01質量%以上5.0質量%以下含む、請求項1に記載のペースト組成物。At least one selected from the group consisting of non-aircraft boron compound and organic boron compound, in terms of boron containing 0.01 wt% to 5.0 wt% or less, the paste composition according to claim 1. アルミニウム粉末を60質量%以上75質量%以下、ガラスフリットを0.3質量%以上5.0質量%以下、有機質ビヒクルを20質量%以上30質量%以下、無機ホウ素化合物および有機ホウ素化合物からなる群から選ばれた少なくとも1種を、ホウ素換算で0.01質量%以上5.0質量%以下含む、請求項1に記載のペースト組成物。75 mass% 60 mass% or more of aluminum powder below 5.0 wt% 0.3 wt% of glass frit or less, the organic vehicle 20 mass% to 30 mass%, consisting of non-aircraft boron compound and organic boron compound The paste composition of Claim 1 which contains at least 1 sort (s) chosen from the group 0.01 to 5.0 mass% in conversion of boron. 前記無機ホウ素化合物は、炭化物、酸化物、塩化物、臭化物、ヨウ化物、弗化物、窒化物およびホウ酸から選ばれた少なくとも1種である、請求項1から請求項3までのいずれか1項に記載のペースト組成物。  4. The inorganic boron compound according to claim 1, wherein the inorganic boron compound is at least one selected from carbides, oxides, chlorides, bromides, iodides, fluorides, nitrides, and boric acid. The paste composition as described in 2. 前記有機ホウ素化合物は、トリメトキシボロン、トリエトキシボロン、トリプロポキシボロンおよびトリプトキシボロンからなる群から選ばれた少なくとも1種である、請求項1から請求項3までのいずれか1項に記載のペースト組成物。  4. The organic boron compound according to claim 1, wherein the organic boron compound is at least one selected from the group consisting of trimethoxyboron, triethoxyboron, tripropoxyboron, and tryptoxyboron. 5. Paste composition. 請求項1から請求項5までのいずれか1項に記載のペースト組成物をp型シリコン半導体基板の上に塗布した後、焼成することにより形成した電極を備えた、太陽電池。  The solar cell provided with the electrode formed by apply | coating the paste composition of any one of Claim 1- Claim 5 on the p-type silicon semiconductor substrate, and baking.
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