JP3760361B2 - Conductive composition for solar cell - Google Patents
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- JP3760361B2 JP3760361B2 JP04563398A JP4563398A JP3760361B2 JP 3760361 B2 JP3760361 B2 JP 3760361B2 JP 04563398 A JP04563398 A JP 04563398A JP 4563398 A JP4563398 A JP 4563398A JP 3760361 B2 JP3760361 B2 JP 3760361B2
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- 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
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Description
【０００１】
【発明の属する技術分野】
本発明は、太陽電池用導電性組成物に関するものである。
【０００２】
【従来の技術】
従来より電子部品の厚膜電極用の導電性組成物（以下、導電ペーストとする。）として、導電粉末とガラスフリットを有機ビヒクルに分散させたものが用いられてきた。この種の導電ペーストを、セラミック基板あるいはセラミック部品等に印刷または塗布し、その後、乾燥、焼成して有機成分を除去し、導電粒子を焼結させて導電性被膜を形成する。
【０００３】
近年、省エネルギー化、低コスト化を目的に、厚膜電極の焼成においてもその低温化が求められているが、この場合、大気中で低温焼成できる材料としては、固有抵抗が低く比較的安価なＡｇ粉末を用いた導電ペースト（以下、Ａｇペーストとする。）がよく用いられてきた。しかしながら、Ａｇ粒子がネッキングし粒子成長するためには焼成時にある程度の熱量を必要とするため、特に７００℃以下の低温で焼成する場合などでは焼結不足となり、所望の導電性や膜強度が得られないことがあった。
【０００４】
一方、半導体素子、例えばＳｉ太陽電池の電極形成用としても、Ａｇ粉末、ガラスフリットおよび有機ビヒクルから構成されるＡｇペーストがよく用いられている。Ｓｉ太陽電池の代表的な例を図６に示す。ｎ＋／ｐ／ｐ＋接合を形成したＳｉウェハ２３の受光面に、反射防止膜２１（ＴｉＯ2）とＡｇ電極２５を形成し、Ｓｉウェハ２３の裏面にＡｌ電極２７を形成した構造である。受光面側Ａｇペーストは反射防止膜２１の上からスクリーン印刷され、近赤外線炉で焼成される。この時、Ａｇ電極２５が反射防止膜２１やＳｉウェハ２３表面のＳｉＯ2などの絶縁被膜を貫通せず、かつ、ＳｉとオーミックコンタクトしないとＳｉに対する接触抵抗が増大する。その結果、太陽電池Ｖ−Ｉ特性の曲線因子であるフィルファクタ（以下、ＦＦとする。）が劣化してしまう。比較的高温でＡｇペーストを焼き付けると接触抵抗が低下しＦＦを向上できるが、この場合、Ａｇやガラス成分など電極からの拡散成分がＳｉウェハのｐｎ接合を破壊し、電圧特性が劣化してしまう不具合が発生していた。
【０００５】
【発明が解決しようとする課題】
Ａｇ電極の焼結性を向上させる手段としては、一般的にＰｂやＢｉをＡｇペースト中に添加することが知られている。しかし、これらの添加元素は自らガラス化することでＡｇの焼結促進に作用するため、その効果が得られる焼成温度は約７００℃以上と高い。また、導電成分であるＡｇ粉末を微粒子化して焼結開始温度を下げる試みもなされているが、この場合はコスト高となり実用的ではない。
【０００６】
本発明は上記のような問題点に鑑みてなされたものであり、粒子成長や緻密化といった厚膜電極の焼結作用を促進できるとともに、低温焼成化が可能な太陽電池用導電性組成物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】
本発明は、上記の課題を解決するために太陽電池用導電性組成物を完成するに至った。本願発明の太陽電池用導電性組成物は、Ａｇ粉末と、Ｖ 2 Ｏ 5 、ＡｇＶＯ 3 、Ａｇ 4 Ｖ 2 Ｏ 7 およびＣｕＶ 2 Ｏ 6 からなる群から選ばれる少なくとも１種のＶ化合物と、有機ビヒクルと、からなることに特徴がある。
【０００８】
Ａｇペースト中に添加されたＶあるいはそれらの化合物は、Ａｇペーストの焼成時において、４００℃前後の低温領域から導電成分であるＡｇ粒子と固相反応を起こし、Ａｇ粒子表面に複合酸化物の層を生成する（Ｖの場合はＡｇ4Ｖ2Ｏ 7 ）。この反応層を介してＡｇの拡散が起こるため、低温領域からＡｇのネッキングと粒子成長が開始する。さらに昇温するとＡｇ電極中に生成した複合酸化物相が融解し、生じた融液がＡｇ粒子の液相焼結を助長して、Ａｇ電極の焼結が促進される。
【０００９】
また、Ｓｉ太陽電池用受光面側ＡｇペーストでＶあるいはそれらの化合物を添加した場合、Ｓｉに対してオーミックコンタクトできるようになる理由は次のように考えられる。すなわち、電極焼成時に生成した、Ａｇと添加元素間の複合酸化物相の融液が、Ｓｉウェハ表面の反射防止膜やＳｉＯ2の絶縁被膜を融解することで絶縁被膜中のＡｇの拡散を容易にし、Ｓｉウェハに対する接触抵抗を下げることによる効果である。ＶとＡｇとの固相反応が低温から開始すること、および反応によって生じた複合酸化物が低融点であることから、従来のものよりもその効果は大きく、かつ添加量も少量で済む。その結果、電極の導電性やハンダ付性を損ねることなく、Ｓｉ太陽電池特性ＦＦを確保することが可能となる。
【００１０】
本願発明の太陽電池用導電性組成物は、Ａｇ粉末と、Ｖ 2 Ｏ 5 、ＡｇＶＯ 3 、Ａｇ 4 Ｖ 2 Ｏ 7 およびＣｕＶ 2 Ｏ 6 からなる群から選ばれる少なくとも１種のＶ化合物と、ガラスフリットと、有機ビヒクルと、からなることに特徴がある。このように、必要に応じてガラスフリットを添加してもよい。
また、本願発明の太陽電池用導電性組成物において、前記Ｖ化合物は、ＡｇＶＯ 3 およびＡｇ 4 Ｖ 2 Ｏ 7 からなる群から選ばれる少なくとも１種であることを特徴とする。
【００１１】
本願発明の導電性組成物においては、前記Ｖ化合物の添加量は、前記Ａｇ粉末１００重量部に対して０．２〜１６重量部の範囲内であることが好ましい。
【００１２】
すなわち、添加量が０．２重量部未満の場合には、添加効果に乏しいため好ましくない。一方、添加量が１６重量部を超える場合には、添加量が過剰で固有抵抗が上昇してしまうため好ましくない。なお、さらに好ましくは接合部の半田付け性の確保のためにも、添加量がＡｇ粉末１００重量部に対して０．２〜３．０重量部の範囲内である。
【００１３】
本願発明の導電性組成物においては、前記Ｖ化合物の添加量は、前記導電性組成物１００ｗｔ％のうち０．１〜１０ｗｔ％の範囲内であることが好ましい。
【００１４】
すなわち、添加量が０．１ｗｔ％未満の場合には、添加効果に乏しいため好ましくない。一方、添加量が１０ｗｔ％を超える場合には、添加量が過剰で固有抵抗が上昇してしまうため好ましくない。なお、さらに好ましくは接合部の半田付け性の確保のためにも、添加量が０．１〜２．０ｗｔ％の範囲内である。
【００１５】
【発明の実施の形態】
本願発明で用いられるＶ化合物においては、その形状、粒径、添加量等は必ずしも限定されるものではない。
【００１６】
なお、Ｖの化合物とは、Ｖ2Ｏ 5 などの酸化物、ＡｇＶＯ3、ＣｕＶ2Ｏ6などの複合酸化物、その他有機金属として含有するものなど、その形態は限定されるものではない。ただし、Ｓｉ太陽電池の受光面側のＡｇ電極に用いる場合には、Ａｇペースト中のガラスフリットに、Ｖ金属もしくはその化合物を固溶させて添加することが好ましい。
【００１７】
本願発明で用いられる有機溶剤も特に限定されるものではなく、α−テルピネオールなど導電ペーストに用いられる一般的なものが使用可能である。
【００１８】
本願発明で用いられるガラスフリットの含有量は必ずしも限定されるものではなく、その組成も限定されるものではないが、ＰｂＯ−Ｂ2Ｏ3−ＳｉＯ2系ガラスやＢｉ2Ｏ3−Ｂ2Ｏ3−ＳｉＯ2系ガラス、ＺｎＯ−Ｂ2Ｏ3−ＳｉＯ2系ガラスなどが代表的である。
【００１９】
次に、本発明を実施例に基づき、さらに具体的に説明するが、本発明はかかる実施例のみに限定されるものではない。
【００２０】
【実施例】
（実施例１）平均粒径１μｍのＡｇ粉末と、軟化点３５０℃のＰｂＯ−Ｂ2Ｏ3−ＳｉＯ2系ガラスフリットと、α−テルピネオール溶剤にセルロース樹脂を溶解して作製した有機ビヒクルと、金属酸化物（Ｖ2Ｏ 5 ）を表１に示す比率で調合し、３本ロールミルで混練して導電ペーストを準備した。金属酸化物は平均粒径１〜３μｍのものを用いた。なお、試料Ｎｏ．1と試料Ｎｏ．１０は上記金属酸化物を含まない比較例である。
【００２１】
【表１】
【００２２】
得られたＡｇペーストをアルミナ基板上にライン幅４００μｍ、ライン長さ２００ｍｍのパターンでスクリーン印刷し、１５０℃で５分間乾燥した後、近赤外線ベルト炉を用いて５５０℃で５分間焼成し（ピーク保持時間１分間）、焼き付けたＡｇ電極を形成した。次にライン両端間の電気抵抗と電極厚みを測定して、各Ａｇ電極の固有抵抗ρを求めた。更にＡｇ電極の焼成面をＳＥＭで観察し、Ａｇ結晶粒子の平均粒径を測長し求めた。結果を表１に併せて示す。
【００２３】
表１の結果から明らかなように、試料Ｎｏ．３〜Ｎｏ．６、およびＮｏ．１１においてＡｇ粒子の焼結成長が著しく、かつ固有抵抗が低下していることがわかる。なお、試料Ｎｏ．２ではＶ2Ｏ5の添加量が少なく充分な添加効果が得られていない。逆に試料Ｎ０．７では添加量が過剰なために、固有抵抗が上昇する結果となった。
【００２４】
試料Ｎｏ．１とＮｏ．４の焼結面ＳＥＭ写真を図１と図２に示す。Ｖ2Ｏ 5 を添加したＡｇ電極の焼結面はＡｇのみの場合に比べてネッキングと粒子成長が著しく進行していることがわかる。なお、本発明にかかるＡｇペーストで形成したＡｇ電極の膜強度が、Ａｇのみの電極に比べて上昇することをテープ剥離試験によって確認しているが、これはＳＥＭ写真にみられるような焼結構造に起因するものと考えられる。
【００２５】
さらに試料No.1とNo.4のＡｇペーストについて、焼成温度を４００℃から８５０℃まで変化させた時のＡｇ粒子径の変化を、上記と同様の方法で求めた。結果を図３に示す。本発明によりＡｇ電極の焼結を低温領域から促進できることが、この結果からも明らかである。
【００２６】
（実施例２）平均粒径１μｍのＡｇ粉末と、軟化点３５０℃のＰｂＯ−Ｂ2Ｏ3−ＳｉＯ2系ガラスフリットと、α−テルピネオ−ル溶剤にセルロース樹脂を溶解して作製した有機ビヒクルと、添加物（Ｖ2Ｏ5、ＡｇＶＯ3、Ｖレジネート）を表２に示す比率で調合し、３本ロールミルで混練して導電ペーストを準備した。金属酸化物は平均粒径１〜３μｍのものを使用し、Ｖレジネートには金属含有量が５ｗｔ％のものを用いた。なお、試料Ｎｏ．１は上記添加物を含まない比較例であり、試料Ｎｏ．２はＰ化合物としてＡｇ3ＰＯ4を添加した比較例である。
【００２７】
【表２】
【００２８】
得られたＡｇペーストを図４に示すような電極間隔の異なるパターンを用いて、予め０．１μｍの反射防止膜１１（ＴｉＯ2）がコーティングされたＳｉウエハ１３の受光面側（ｎ＋側）にスクリーン印刷した。試料を１５０℃で５分間乾燥した後、近赤外線ベルト炉にて７５０℃で５分間焼成し（ピーク保持時間１分間）、焼き付けたＡｇ電極１５を形成した。次に、間隔の異なる対向電極間の電気抵抗を数点測定し、電極間距離を０に外挿した時の抵抗値を算出、この値をＳｉに対する接触抵抗値Ｒｃとした。
【００２９】
次に、直径４インチ（10.16ｃｍ）のｐｎ接合型Ｓｉウエハ１３の裏面側（ｐ側）にＡｌ電極ペーストを全面に塗布する一方、０．１μｍの反射防止膜１１（ＴｉＯ2）をコーティングした受光面側（ｎ＋側）に上記Ａｇペーストをライン幅２００μｍ、ライン間隔５ｍｍで格子状にスクリーン印刷した。そして１５０℃で５分間乾燥した後、近赤外線ベルト炉で７５０℃５分間焼成し、焼き付けたＡｇ電極１５を形成することにより、図５のＳｉ太陽電池セル１７を得た。得られた各Ｓｉ太陽電池セルについて、ＦＦならびに格子状電極の半田付け性を調べた。結果を接触抵抗値Ｒｃと併せて表２に示す。なお、半田付け性の結果において、○は半田濡れ面積が電極面積の７５％以上、△は半田濡れ面積が電極面積の５０〜７５％、×は半田濡れ面積が電極面積の５０％以下を示す。
【００３０】
表２の結果から明らかなように、試料Ｎｏ．３〜Ｎｏ．７、Ｎｏ．１０〜Ｎｏ．１３で、接触抵抗が１Ω以下に低減でき、その結果ＦＦが０．７以上と従来のペーストに比べて著しく向上している。また、本発明にかかるＡｇペーストで形成したＡｇ電極は従来のＰ化合物を添加したＡｇ電極に比べて半田付け性が向上しており、Ｓｉ太陽電池特性と半田付け性の両立が可能となった。
【００３１】
【発明の効果】
本発明の太陽電池用導電性組成物を用いれば、Ａｇ電極の焼結性を著しく促進させることができる。特に７００℃以下の低温焼成における電極の導電性や膜強度を向上させることができ、よって低温焼成化による低コスト化や、基板素子の処理温度に上限制約がある場合（ガラス基板、Ｎｉメッキを施したサーミスタ素子など）の電極形成に寄与することが可能である。
【００３２】
よって、Ｓｉ太陽電池の受光面側Ａｇ電極に適用した場合、半田付け性を損なうことなくオーミック電極を形成することができ、Ｓｉ太陽電池特性ＦＦを従来の０．５程度から実用範囲である０．７以上に向上させることができる。また、電極焼成後に安定したＦＦが得られるため、従来特性を回復させるために行われていた酸処理などの後工程を省略することができ、Ｓｉ太陽電池のコストダウンにも寄与することができる。
【図面の簡単な説明】
【図１】 試料No.1の焼結面のＳＥＭの写真である。
【図２】 試料No.4の焼結面のＳＥＭの写真である。
【図３】 焼成温度とＡｇの平均粒子径との関係を示すグラフである。
【図４】 測定サンプルを示す平面図である。
【図５】 Ｓｉ太陽電池セルを示す平面図である。
【図６】 Ｓｉ太陽電池を示す説明図である。 [0001]
BACKGROUND OF THE INVENTION
The present invention relates to a conductive composition for a solar cell.
[0002]
[Prior art]
Conventionally, conductive powder and glass frit dispersed in an organic vehicle have been used as a conductive composition for a thick film electrode of an electronic component (hereinafter referred to as a conductive paste). This type of conductive paste is printed or applied to a ceramic substrate or ceramic component, and then dried and baked to remove organic components and sinter the conductive particles to form a conductive coating.
[0003]
In recent years, for the purpose of energy saving and cost reduction, lowering of the temperature is also required in the firing of thick film electrodes. In this case, as a material that can be fired at low temperature in the atmosphere, the specific resistance is low and relatively inexpensive. A conductive paste using Ag powder (hereinafter referred to as Ag paste) has been often used. However, in order for the Ag particles to neck and grow, a certain amount of heat is required at the time of firing. In particular, when firing at a low temperature of 700 ° C. or less, sintering is insufficient, and desired conductivity and film strength can be obtained. I couldn't.
[0004]
On the other hand, an Ag paste composed of Ag powder, glass frit, and an organic vehicle is often used for forming electrodes of semiconductor elements such as Si solar cells. A typical example of a Si solar cell is shown in FIG . In this structure, an antireflection film 21 (TiO 2 ) and an Ag electrode 25 are formed on the light receiving surface of the Si wafer 23 on which the n + / p / p + junction is formed, and an Al electrode 27 is formed on the back surface of the Si wafer 23. The light receiving surface side Ag paste is screen-printed from above the antireflection film 21 and baked in a near infrared furnace. At this time, if the Ag electrode 25 does not penetrate the insulating coating such as SiO 2 on the surface of the antireflection film 21 or the Si wafer 23 and does not make ohmic contact with Si, the contact resistance to Si increases. As a result, the fill factor (hereinafter referred to as FF), which is a curve factor of the solar cell VI characteristics, is deteriorated. When the Ag paste is baked at a relatively high temperature, the contact resistance can be reduced and the FF can be improved, but in this case, the diffusion component from the electrode such as Ag or glass component destroys the pn junction of the Si wafer and the voltage characteristics deteriorate. There was a bug.
[0005]
[Problems to be solved by the invention]
As means for improving the sinterability of the Ag electrode, it is generally known to add Pb or Bi to the Ag paste. However, since these additive elements vitrify themselves to promote the sintering of Ag, the firing temperature at which the effect is obtained is as high as about 700 ° C. or higher. In addition, attempts have been made to lower the sintering start temperature by making the Ag powder, which is a conductive component, fine, but in this case, the cost increases and is not practical.
[0006]
The present invention has been made in view of the above-described problems. A conductive composition for a solar cell capable of promoting the sintering action of a thick film electrode such as particle growth and densification and capable of being fired at a low temperature is provided. The purpose is to provide.
[0007]
[Means for Solving the Problems]
This invention came to complete the electrically conductive composition for solar cells in order to solve said subject. The conductive composition for solar cell of the present invention comprises an Ag powder, at least one V compound selected from the group consisting of V 2 O 5 , AgVO 3 , Ag 4 V 2 O 7, and CuV 2 O 6 , and organic It is characterized by comprising a vehicle.
[0008]
V Ah Rui those compounds added in Ag paste, at the time of baking the Ag paste, cause Ag particles and solid phase reaction is a conductive component from the low temperature region of about 400 ° C., the composite oxide Ag particle surface (In the case of V, Ag 4 V 2 O 7 ) . Since Ag diffusion occurs through this reaction layer, Ag necking and particle growth start from a low temperature region. When the temperature is further increased, the composite oxide phase generated in the Ag electrode is melted, and the resulting melt promotes liquid phase sintering of Ag particles, thereby promoting the sintering of the Ag electrode.
[0009]
Also, if the V Ah Rui in Si solar cell light-receiving surface side Ag paste prepared by adding these compounds, the reason that will allow ohmic contacts to Si is considered as follows. That is, the melt of the composite oxide phase between Ag and the additive element generated during electrode firing melts the antireflection film on the Si wafer surface and the SiO 2 insulating film, thereby facilitating the diffusion of Ag in the insulating film. And lowering the contact resistance with respect to the Si wafer. Since the solid-phase reaction between V and Ag starts at a low temperature and the composite oxide generated by the reaction has a low melting point, the effect is greater than that of the conventional one, and the amount added is small. As a result, the Si solar cell characteristic FF can be secured without impairing the conductivity and solderability of the electrode.
[0010]
The conductive composition for solar cell of the present invention comprises an Ag powder, at least one V compound selected from the group consisting of V 2 O 5 , AgVO 3 , Ag 4 V 2 O 7 and CuV 2 O 6 , and glass It is characterized by comprising a frit and an organic vehicle. Thus, glass frit may be added as necessary.
In the conductive composition for a solar cell of the present invention, the V compound is at least one selected from the group consisting of AgVO 3 and Ag 4 V 2 O 7 .
[0011]
In the conductive composition of the present invention, the amount of the V compound added is preferably in the range of 0.2 to 16 parts by weight with respect to 100 parts by weight of the Ag powder.
[0012]
That is, when the addition amount is less than 0.2 parts by weight, the effect of addition is poor, which is not preferable. On the other hand, when the addition amount exceeds 16 parts by weight, the addition amount is excessive and the specific resistance increases, which is not preferable. More preferably, the addition amount is in the range of 0.2 to 3.0 parts by weight with respect to 100 parts by weight of Ag powder in order to ensure solderability of the joint.
[0013]
In the conductive composition of the present invention, the amount of the V compound added is preferably in the range of 0.1 to 10 wt% of 100 wt% of the conductive composition.
[0014]
That is, when the addition amount is less than 0.1 wt%, it is not preferable because the addition effect is poor. On the other hand, when the addition amount exceeds 10 wt%, the addition amount is excessive and the specific resistance increases, which is not preferable. More preferably, the addition amount is in the range of 0.1 to 2.0 wt% in order to ensure the solderability of the joint.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the V compound used in the present invention, the shape, particle size, addition amount, etc. are not necessarily limited.
[0016]
Note that the compound of V, V 2 O 5 of which oxides, AgVO 3, CuV composite oxide such as 2 O 6, such as one containing as other organometallic, its form is not intended to be limiting. However, when used in the Ag electrode on the light-receiving surface side of the Si solar cells, the glass frit in the Ag paste, is preferably added by solid solution V metals or their compounds.
[0017]
The organic solvent used in the present invention is not particularly limited, and general solvents used for conductive pastes such as α-terpineol can be used.
[0018]
The content of the glass frit used in the present invention is not necessarily limited, and the composition thereof is not limited, either PbO—B 2 O 3 —SiO 2 glass or Bi 2 O 3 —B 2 O. Typical examples include 3- SiO 2 glass and ZnO—B 2 O 3 —SiO 2 glass.
[0019]
Next, the present invention will be described more specifically based on examples. However, the present invention is not limited to the examples.
[0020]
【Example】
(Example 1) Ag powder having an average particle diameter of 1 μm, a PbO—B 2 O 3 —SiO 2 glass frit having a softening point of 350 ° C., an organic vehicle prepared by dissolving a cellulose resin in an α-terpineol solvent, A metal oxide (V 2 O 5 ) was prepared at a ratio shown in Table 1, and kneaded with a three-roll mill to prepare a conductive paste. A metal oxide having an average particle diameter of 1 to 3 μm was used. Sample No. 1 and sample no. 10 is a comparative example not containing the above metal oxide.
[0021]
[Table 1]
[0022]
The obtained Ag paste was screen-printed on an alumina substrate with a pattern having a line width of 400 μm and a line length of 200 mm, dried at 150 ° C. for 5 minutes, and then fired at 550 ° C. for 5 minutes using a near infrared belt furnace (peak A baked Ag electrode was formed for a holding time of 1 minute. Next, the electrical resistance between both ends of the line and the electrode thickness were measured to determine the specific resistance ρ of each Ag electrode. Furthermore, the fired surface of the Ag electrode was observed with an SEM, and the average particle diameter of the Ag crystal particles was measured and determined. The results are also shown in Table 1.
[0023]
As is clear from the results in Table 1, sample No. 3-No. 6, Contact and No. 11 shows that the Ag particles are significantly sintered and the specific resistance is lowered. Sample No. In No. 2, the addition amount of V 2 O 5 is small and a sufficient addition effect is not obtained. On the contrary, the sample N0.7 resulted in an increase in specific resistance due to an excessive amount added.
[0024]
Sample No. 1 and N o. The sintered surface SEM photograph of No. 4 is shown in FIGS. It can be seen that the necking and particle growth proceeded significantly on the sintered surface of the Ag electrode to which V 2 O 5 was added as compared with the case of Ag alone. It has been confirmed by a tape peeling test that the film strength of the Ag electrode formed from the Ag paste according to the present invention is higher than that of the Ag-only electrode. This is a sintered structure as seen in the SEM photograph. This is thought to be due to the structure.
[0025]
Further, with respect to the Ag pastes of Samples No. 1 and No. 4, the change in Ag particle diameter when the firing temperature was changed from 400 ° C. to 850 ° C. was determined by the same method as described above. The results are shown in FIG . It is clear from this result that the sintering of the Ag electrode can be promoted from the low temperature region according to the present invention.
[0026]
(Example 2) An organic vehicle prepared by dissolving a cellulose resin in an Ag powder having an average particle diameter of 1 μm, a PbO—B 2 O 3 —SiO 2 glass frit having a softening point of 350 ° C., and an α-terpineol solvent. When the additive of (V 2 O 5, AgVO 3 , V Rejine g) were blended in the proportions shown in Table 2, were prepared conductive paste was kneaded with a three-roll mill. A metal oxide having an average particle diameter of 1 to 3 μm was used, and a V resinate having a metal content of 5 wt% was used. Sample No. 1 is a comparative example which does not contain the above additives. 2 is a comparative example in which Ag 3 PO 4 was added as a P compound.
[0027]
[Table 2]
[0028]
The obtained Ag paste was used on the light receiving surface side (n + side) of the Si wafer 13 previously coated with a 0.1 μm antireflection film 11 (TiO 2 ) using patterns having different electrode intervals as shown in FIG. Screen printed. The sample was dried at 150 ° C. for 5 minutes and then baked at 750 ° C. for 5 minutes in a near-infrared belt furnace (peak retention time 1 minute) to form a baked Ag electrode 15. Next, several points were measured for the electrical resistance between the opposing electrodes with different intervals, and the resistance value when the interelectrode distance was extrapolated to 0 was calculated, and this value was defined as the contact resistance value Rc for Si.
[0029]
Next, an Al electrode paste was applied to the entire back surface (p side) of a 4 inch (10.16 cm) pn junction Si wafer 13 while an antireflection film 11 (TiO 2 ) of 0.1 μm was coated. The Ag paste was screen-printed in a grid pattern with a line width of 200 μm and a line interval of 5 mm on the light receiving surface side (n + side). And dried for 5 minutes at 0.99 ° C., and calcined in the near infrared belt furnace 750 ° C. for 5 minutes, by forming an Ag electrode 15 was baked to obtain a Si solar cell 17 of FIG. About each obtained Si photovoltaic cell, solderability of FF and a grid-like electrode was investigated. The results are shown in Table 2 together with the contact resistance value Rc. In the results of solderability, ◯ indicates that the solder wetted area is 75% or more of the electrode area, Δ indicates that the solder wetted area is 50 to 75% of the electrode area, and x indicates that the solder wetted area is 50% or less of the electrode area. .
[0030]
As is clear from the results in Table 2, the sample No. 3-No. 7, no. 10- No. 13, the contact resistance can be reduced to 1Ω or less, and as a result, the FF is 0.7 or more, which is remarkably improved as compared with the conventional paste. In addition, the Ag electrode formed from the Ag paste according to the present invention has improved solderability as compared with the conventional Ag electrode to which a P compound is added, and it has become possible to achieve both Si solar cell characteristics and solderability. .
[0031]
【The invention's effect】
If the conductive composition for solar cells of the present invention is used, the sinterability of the Ag electrode can be remarkably promoted. In particular, it is possible to improve the electrode conductivity and film strength in low-temperature firing at 700 ° C. or lower, and therefore, when the cost is reduced due to low-temperature firing and the upper limit is imposed on the processing temperature of the substrate element (glass substrate, Ni plating) It is possible to contribute to the electrode formation of the thermistor element etc. which were given.
[0032]
Therefore, when applied to the light receiving surface side Ag electrode of the Si solar cell, an ohmic electrode can be formed without impairing the solderability, and the Si solar cell characteristic FF is about 0 from the conventional level of about 0.5. .7 or more. Moreover, since stable FF is obtained after electrode baking, post-processes, such as an acid treatment performed in order to recover the conventional characteristic, can be omitted, and it can contribute to the cost reduction of Si solar cells. .
[Brief description of the drawings]
FIG. 1 is a SEM photograph of a sintered surface of sample No. 1;
FIG. 2 is a SEM photograph of the sintered surface of Sample No. 4.
FIG. 3 is a graph showing the relationship between the firing temperature and the average particle diameter of Ag.
FIG. 4 is a plan view showing a measurement sample.
FIG. 5 is a plan view showing a Si solar battery cell.
FIG. 6 is an explanatory view showing a Si solar cell.
Claims (7)
Ｖ 2 Ｏ 5 、ＡｇＶＯ 3 、Ａｇ 4 Ｖ 2 Ｏ 7 およびＣｕＶ 2 Ｏ 6 からなる群から選ばれる少なくとも１種のＶ化合物と、
有機ビヒクルと、
からなることを特徴とする太陽電池用導電性組成物。Ag powder;
At least one V compound selected from the group consisting of V 2 O 5 , AgVO 3 , Ag 4 V 2 O 7 and CuV 2 O 6 ;
An organic vehicle,
A conductive composition for a solar cell, comprising:
Ｖ 2 Ｏ 5 、ＡｇＶＯ 3 、Ａｇ 4 Ｖ 2 Ｏ 7 およびＣｕＶ 2 Ｏ 6 からなる群から選ばれる少なくとも１種のＶ化合物と、
ガラスフリットと、
有機ビヒクルと、
からなることを特徴とする太陽電池用導電性組成物。Ag powder;
At least one V compound selected from the group consisting of V 2 O 5 , AgVO 3 , Ag 4 V 2 O 7 and CuV 2 O 6 ;
Glass frit,
An organic vehicle,
A conductive composition for a solar cell, comprising:
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP04563398A JP3760361B2 (en) | 1997-03-24 | 1998-02-26 | Conductive composition for solar cell |
| US09/258,641 US6071437A (en) | 1998-02-26 | 1999-02-26 | Electrically conductive composition for a solar cell |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9-69476 | 1997-03-24 | ||
| JP6947697 | 1997-03-24 | ||
| JP04563398A JP3760361B2 (en) | 1997-03-24 | 1998-02-26 | Conductive composition for solar cell |
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| Publication Number | Publication Date |
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| JPH10326522A JPH10326522A (en) | 1998-12-08 |
| JP3760361B2 true JP3760361B2 (en) | 2006-03-29 |
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