JP6170710B2 - Method for producing conductive paste composition for solar cell - Google Patents
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Description
本発明は、ファイヤースルー法で形成する太陽電池電極用に好適な導電性ペースト組成物の製造方法に関する。 The present invention relates to a method for producing a conductive paste composition suitable for a solar cell electrode formed by a fire-through method.
例えば、一般的なシリコン系太陽電池は、ｐ型多結晶半導体であるシリコン基板の上面にｎ+層を介して反射防止膜および受光面電極が備えられると共に、下面にｐ+層を介して裏面電極(以下、これらを区別しないときは単に「電極」という。)が備えられた構造を有しており、受光により半導体のｐｎ接合に生じた電力を電極を通して取り出すようになっている。上記反射防止膜は、十分な可視光透過率を保ちつつ表面反射率を低減して受光効率を高めるためのもので、窒化珪素、二酸化チタン、二酸化珪素等の薄膜から成る。 For example, a general silicon-based solar cell is provided with an antireflection film and a light-receiving surface electrode on an upper surface of a silicon substrate which is a p-type polycrystalline semiconductor via an n + layer, and on the lower surface via a p + layer. It has a structure provided with electrodes (hereinafter simply referred to as “electrodes” when they are not distinguished from each other), and power generated at the pn junction of the semiconductor by light reception is taken out through the electrodes. The antireflection film is for reducing the surface reflectance and increasing the light receiving efficiency while maintaining a sufficient visible light transmittance, and is made of a thin film such as silicon nitride, titanium dioxide, or silicon dioxide.
上記の反射防止膜は電気抵抗値が高いことから、半導体のｐｎ接合に生じた電力を効率よく取り出すことの妨げとなる。そこで、太陽電池の受光面電極は、例えば、ファイヤースルーと称される方法で形成される。この電極形成方法では、例えば、前記反射防止膜をｎ+層上の全面に設けた後、例えばスクリーン印刷法を用いてその反射防止膜上に導電性ペーストすなわちペースト状の電極材料を適宜の形状で塗布し、焼成処理を施す。これにより、電極材料が加熱熔融させられると同時にこれに接触している反射防止膜が熔融させられ、受光面電極と半導体とが接触させられる。上記導電性ペーストは、例えば、銀粉末と、ガラスフリット(ガラス原料を熔融し急冷した後に必要に応じて粉砕したフレーク状または粉末状のガラスのかけら)と、有機質ベヒクルと、有機溶媒とを主成分とするもので、焼成過程において、この導電性ペースト中のガラス成分が反射防止膜を破るので、導電性ペースト中の導体成分とｎ+層とによってオーミックコンタクトが形成される(例えば、特許文献１を参照。)。そのため、反射防止膜を部分的に除去してその除去部分に電極を形成する場合に比較して工程が簡単になり、除去部分と電極形成位置との位置ずれも生じない利点がある。なお、上記ガラスフリットは例えば硼珪酸ガラスが用いられる。 Since the above-described antireflection film has a high electric resistance value, it prevents an electric power generated at the pn junction of the semiconductor from being efficiently extracted. Therefore, the light-receiving surface electrode of the solar cell is formed by a method called fire-through, for example. In this electrode formation method, for example, after the antireflection film is provided on the entire surface of the n + layer, a conductive paste, that is, a paste-like electrode material is appropriately formed on the antireflection film by using, for example, a screen printing method. And apply a baking process. As a result, the electrode material is heated and melted, and at the same time, the antireflection film in contact with the electrode material is melted, and the light receiving surface electrode and the semiconductor are brought into contact with each other. The conductive paste is mainly composed of, for example, silver powder, glass frit (a piece of flaky or powdered glass that is crushed as necessary after melting and quenching a glass raw material), an organic vehicle, and an organic solvent. In the baking process, the glass component in the conductive paste breaks the antireflection film, so that an ohmic contact is formed by the conductive component in the conductive paste and the n + layer (for example, Patent Documents). See 1). Therefore, the process is simplified as compared with the case where the antireflection film is partially removed and an electrode is formed on the removed portion, and there is an advantage that no displacement occurs between the removed portion and the electrode formation position. For example, borosilicate glass is used as the glass frit.
また、従来から、上述した太陽電池の受光面電極形成において、ファイヤースルー性を向上させてオーミックコンタクトを改善し、延いては曲線因子(ＦＦ値)やエネルギー変換効率を高める等の目的で種々の提案が為されている。例えば、導電性ペーストに燐・バナジウム・ビスマスなどのＶ族元素を添加することによって、ガラスおよび銀の反射防止膜に対する酸化還元作用を促進し、ファイヤースルー性を向上させることが提案されている(例えば、前記特許文献１を参照。)。 Conventionally, in the light receiving surface electrode formation of the above-described solar cell, it is possible to improve the fire-through property and improve the ohmic contact, and for various purposes such as increasing the fill factor (FF value) and energy conversion efficiency. Proposals have been made. For example, it has been proposed that by adding a group V element such as phosphorus, vanadium, or bismuth to a conductive paste, the redox action of glass and silver on the antireflection film is promoted and the fire-through property is improved ( (For example, see the said patent document 1.).
ところで、上述した太陽電池において、受光面側に位置するｎ層を薄くすることによって表面再結合速度を低下させ、より多くの電流を取り出せるようにすること、すなわちシャローエミッタ化することが試みられている。シャローエミッタ化すると、特に400(nm)付近の短波長側も発電に寄与するようになるため、太陽電池の効率向上の面では理想的な解と考えられている。シャローエミッタは受光面側のｎ層厚みが70〜100(nm)と、従来のシリコン太陽電池セルの100〜200(nm)に比較して更に薄くされたもので、受光により発生した電気のうちｐｎ接合に達する前に熱に変わって有効に利用できなかった部分が減じられるので、短絡電流が増大し、延いては発電効率が高められる利点がある。 By the way, in the solar cell described above, an attempt has been made to reduce the surface recombination speed by thinning the n layer located on the light receiving surface side so that more current can be taken out, that is, to form a shallow emitter. Yes. When a shallow emitter is used, the short wavelength side near 400 (nm) also contributes to power generation, so it is considered an ideal solution in terms of improving the efficiency of solar cells. The shallow emitter has an n-layer thickness on the light-receiving surface side of 70 to 100 (nm), which is thinner than the conventional silicon solar cell 100 to 200 (nm). Since the portion that cannot be effectively used by changing to heat before reaching the pn junction is reduced, there is an advantage that the short-circuit current increases and the power generation efficiency is increased.
このような利点のある反面で、シャローエミッタでは、セルを高シート抵抗にする必要があるため表面近傍のドナー元素(例えば燐)濃度が低下し或いはｐｎ接合が浅くなる。表面近傍のドナー元素濃度が低下するとAg-Si間のバリア障壁が増加し、受光面電極のオーミックコンタクトの確保が困難になる。また、ｐｎ接合が浅くなるとファイヤースルーで反射防止膜を十分に破り且つｐｎ接合に電極が侵入しないような侵入深さ制御が非常に困難になる。 On the other hand, in the shallow emitter, since the cell needs to have a high sheet resistance, the concentration of the donor element (for example, phosphorus) near the surface is lowered or the pn junction is shallow. When the donor element concentration near the surface decreases, the barrier barrier between Ag and Si increases, and it becomes difficult to ensure ohmic contact of the light-receiving surface electrode. Further, when the pn junction becomes shallow, it becomes very difficult to control the penetration depth so that the antireflection film is sufficiently broken by fire-through and the electrode does not penetrate the pn junction.
これに対して、導電性ペーストのガラスフリットとして、Teを網目形成成分として含むガラスを用いて電気特性を向上させることが提案されている(例えば、特許文献２を参照。)。Teが含まれていると電極−シリコン界面のガラス層中へのAg等の導電成分の溶解量が増大するため、接触抵抗が低下してオーミックコンタクトの確保が容易になる。また、温度変化に対する導電成分溶解量の変化が小さくなることから、焼成処理の降温過程において、ガラス中に溶解していた導電成分が緩やかに析出するため、最適焼成温度範囲(すなわち焼成マージン)が広がる。これらが電気特性向上をもたらすものと考えられる。この導電性ペーストによれば、ファイヤースルーの制御が容易になるため、ｎ層の薄層化にも対応できる。 On the other hand, it has been proposed to improve electrical characteristics by using glass containing Te as a network forming component as a glass frit of a conductive paste (see, for example, Patent Document 2). If Te is contained, the amount of the conductive component such as Ag dissolved in the glass layer at the electrode-silicon interface increases, so that the contact resistance is lowered and it is easy to secure the ohmic contact. In addition, since the change in the amount of the conductive component dissolved with respect to the temperature change becomes small, the conductive component dissolved in the glass gradually precipitates during the temperature-decreasing process of the baking treatment, so that the optimum baking temperature range (that is, the baking margin) is spread. These are considered to bring about improvement of electrical characteristics. According to this conductive paste, since control of fire-through becomes easy, it is possible to cope with thinning of n layers.
また、導電性ペースト中にガラスフリットとは別にTeやSe等の低融点金属を例えば0.1〜10重量%の範囲で含有する組成とすることも提案されている(例えば、特許文献３を参照。)。この導電性ペーストは、特にシャローエミッタを対象としたものではないが、接触抵抗が低くＦＦ値を大きくできる電極を形成することを目的としたものである。 In addition, it has been proposed that the conductive paste contains a low melting point metal such as Te or Se in a range of, for example, 0.1 to 10% by weight in addition to the glass frit (see, for example, Patent Document 3). ). This conductive paste is not particularly intended for a shallow emitter, but is intended to form an electrode having a low contact resistance and a large FF value.
しかしながら、上記特許文献２に記載のTeを含むガラスが用いられた導電性ペーストでは、接触抵抗が低下する反面ではんだ接着強度が不十分になっていた。一方、上記特許文献３に記載のTeやSeをガラスとは別に添加する導電性ペーストでは、はんだ接着強度は維持される反面で接触抵抗が十分に低くならない問題があった。また、Teは侵食抑制作用が強いため、添加量が多くなるとファイヤースルーが不十分になって、却って電気特性の低下や最適焼成温度範囲を狭めることになる。そのため、導電性ペーストにTeを添加する効果は、未だ十分に得られておらず、一層の特性向上が望まれていた。 However, in the conductive paste using the glass containing Te described in Patent Document 2, the contact resistance is reduced, but the solder adhesive strength is insufficient. On the other hand, the conductive paste in which Te or Se described in Patent Document 3 is added separately from glass has a problem that the contact resistance is not sufficiently lowered while the solder adhesive strength is maintained. Further, Te has a strong erosion inhibiting action, so if the addition amount increases, fire-through will be insufficient, and on the contrary, the electrical characteristics will be lowered and the optimum firing temperature range will be narrowed. Therefore, the effect of adding Te to the conductive paste has not yet been sufficiently obtained, and further improvement in characteristics has been desired.
本発明は、以上の事情を背景として為されたもので、その目的は、ＦＦ値や出力特性を一層向上させ得る太陽電池用導電性ペースト組成物の製造方法を提供することにある。 The present invention has been made against the background described above, and an object thereof is to provide a method for producing a conductive paste composition for a solar cell that can further improve the FF value and output characteristics.
斯かる目的を達成するため、本発明の要旨とするところは、導電性粉末と、ガラスフリットと、ベヒクルとを含む太陽電池用導電性ペースト組成物の製造方法であって、メカノケミカル法によってTe化合物粒子を前記ガラスフリットの粒子表面に分散して固着させて複合粒子を得る複合化処理工程と、前記導電性粉末と、前記複合粒子と、前記ベヒクルと含むペースト原料を混合する混合工程とを、含むことにある。 In order to achieve such an object, the gist of the present invention is a method for producing a conductive paste composition for a solar cell containing a conductive powder, a glass frit, and a vehicle. and decryption process steps of the compound particles are fixed distributed on the particle surfaces of the glass frit to obtain the composite particles, and the conductive powder, wherein the composite particles, a mixing step of mixing the paste material containing said vehicle , To include.
このようにすれば、太陽電池用導電性ペースト組成物に含まれる複合粒子は、複合化処理工程において、Te化合物粒子がメカノケミカル法によってガラスフリットの表面に固着されていることから、混合工程を含むペースト調製の際から、電極形成のために太陽電池用基板に塗布されて焼成処理を施されてガラスフリットが熔融するまでの間、ガラスフリット表面にTe化合物粒子が留まる。そのため、本発明の製造方法により製造したペースト組成物を用いてファイヤースルーにより電極を形成すると、ガラス中への導電成分溶解量の増大に寄与するTeの割合が増えることから、Teによる侵食抑制作用が許容できる程度にTe量を留めながら、ガラス中への導電成分溶解量を十分に多くしてオーミックコンタクトを確保することができるので、ＦＦ値や出力特性等の電気特性を高め得る。上記ガラスフリットおよびTe化合物粒子は、全量が複合粒子として含まれていることが理想であるが、何れか或いは両方が複合化していない形態で含まれていても、複合粒子として含まれている割合に応じて本発明の効果を享受することができる。 In this way, the composite particles contained in the conductive paste composition for solar cells are mixed in the compounding process because the Te compound particles are fixed to the surface of the glass frit by the mechanochemical method in the compounding process. The Te compound particles remain on the surface of the glass frit from the preparation of the paste to be applied until the glass frit is melted by being applied to the solar cell substrate for electrode formation and subjected to a baking treatment. Therefore, when an electrode is formed by fire-through using the paste composition produced by the production method of the present invention, the proportion of Te that contributes to an increase in the amount of conductive component dissolved in the glass increases. However, since the ohmic contact can be secured by sufficiently increasing the amount of the conductive component dissolved in the glass while keeping the amount of Te to an acceptable level, electrical characteristics such as FF value and output characteristics can be improved. Ideally, the glass frit and Te compound particles are all contained as composite particles, but even if either or both of them are contained in a non-complexed form, they are contained as composite particles. The effect of the present invention can be enjoyed accordingly.
なお、「メカノケミカル法」は、非加熱の粉砕・混合操作であり、例えばロータを備えた容器内に処理対象の粉体を投入し、ロータを高速回転させることによって粉体粒子個々に衝撃力、圧縮力、剪断力を均一に作用させ、機械的エネルギで結晶構造を破壊し或いは結合状態を切断して活性化させることにより、固相反応を促進させる方法である。この処理方法によれば、ガラスフリット粒子の表面にTe化合物粒子が分散した状態で強固に固着された複合粒子を得るに際して何ら加熱処理を伴わないため、容易且つ安価に複合粒子を製造し得る。「メカノケミカル法」に用いられる処理装置は、例えば、軸心が略水平方向に伸びる円筒状の混合容器と、上述したように粒子個々に衝撃力等が均一に作用する特殊形状のロータとを備えたもので、そのロータは例えば周速50(m/s)以上の高速回転が可能なものが好ましい。 The “mechanochemical method” is an unheated pulverization / mixing operation. For example, the powder to be treated is put into a container equipped with a rotor and the rotor is rotated at a high speed, whereby the impact force is individually applied to the powder particles. In this method, the solid-phase reaction is promoted by applying a compressive force and a shearing force uniformly, breaking the crystal structure with mechanical energy, or activating by cutting the bonded state. According to this treatment method, since no heat treatment is involved in obtaining composite particles firmly fixed in a state where Te compound particles are dispersed on the surface of the glass frit particles, the composite particles can be produced easily and inexpensively. A processing apparatus used in the “mechanochemical method” includes, for example, a cylindrical mixing container having an axial center extending in a substantially horizontal direction, and a specially shaped rotor in which an impact force or the like acts uniformly on each particle as described above. It is preferable that the rotor is capable of rotating at a high speed of, for example, a peripheral speed of 50 (m / s) or more.
このような「メカノケミカル法」で得られる複合粒子は、ガラスフリット粒子の表面に強固に固着されたTe化合物粒子によってその表面に凹凸が形成されるので、２種類の粉体を単に混合しただけの混合粉体に比較して安息角が小さく、極めて高い流動性を有する。また、複合粒子は単に混合しただけの混合粉体よりも濡れ性が良い(例えば、粉体を円筒状の容器に入れて下から水を浸透させると、混合粉体では水が殆ど浸透せず、複合粒子は水がよく浸透することから、良好な濡れ性が確かめられる。)。そのため、複合粒子を含むペースト組成物は、ペースト中における複合粒子の分散性がよいことから、ファイヤースルーの際に導電性ペーストと基板との界面にTe化合物粒子が好適に分布する。したがって、その界面近傍における導電成分の溶解量の増大の程度や侵食抑制作用の程度のばらつきが小さくなるため、形成される電極と基板との界面の一様性が高められ延いては良好な電気特性が得られる。 Since the composite particles obtained by such a “mechanochemical method” have irregularities formed on the surface by the Te compound particles firmly fixed on the surface of the glass frit particles, the two kinds of powders are simply mixed. The angle of repose is smaller than that of the mixed powder, and it has extremely high fluidity. In addition, the composite particles have better wettability than a mixed powder that is simply mixed (for example, if the powder is placed in a cylindrical container and water is infiltrated from below, the mixed powder hardly permeates water. Since the composite particles penetrate well with water, good wettability is confirmed.) Therefore, since the paste composition containing composite particles has good dispersibility of the composite particles in the paste, Te compound particles are suitably distributed at the interface between the conductive paste and the substrate during fire-through. Therefore, since the degree of increase in the amount of the conductive component dissolved in the vicinity of the interface and the variation in the degree of the erosion suppressing action are reduced, the uniformity of the interface between the electrode to be formed and the substrate is enhanced, and good electrical characteristics can be obtained. Characteristics are obtained.
本発明においては、Te化合物粒子がガラスフリット粒子の表面に固着された複合粒子を導電性ペースト組成物中に含むことを必須とするが、ガラスフリットの一部または全部がTeを網目修飾酸化物として含むガラスから成ることを妨げない。Teをガラス中に含む場合には、ハンダ接着強度が十分に得られるようにその含有量を定めることが望ましい。 In the present invention, it is essential that the conductive paste composition contains composite particles in which Te compound particles are fixed to the surface of the glass frit particles. However, part or all of the glass frit contains Te as a network-modified oxide. Does not prevent it from being made of glass. When Te is contained in the glass, it is desirable to determine its content so that the solder adhesive strength can be sufficiently obtained.
ここで、好適には、前記複合粒子はTe化合物粒子／ガラスフリット粒子の粒径比が1/10〜1/40の範囲内である。粒径比が1/10以下であれば、Te化合物粒子の粒径がガラスフリット粒子に対して十分に小さいため、ガラスフリット粒子の表面にTe化合物粒子が高い一様性を以て固着される。粒径比が1/40以上であれば、ガラスフリット粒子の表面に固着されるTe量(質量比)が十分に多くなるため、Teによる導電成分溶解量の増大効果が十分に得られる。 Here, the composite particles preferably have a Te compound particle / glass frit particle size ratio in the range of 1/10 to 1/40. When the particle size ratio is 1/10 or less, the particle size of the Te compound particles is sufficiently small with respect to the glass frit particles, so that the Te compound particles are fixed to the surface of the glass frit particles with high uniformity. When the particle size ratio is 1/40 or more, the amount of Te (mass ratio) fixed to the surface of the glass frit particles is sufficiently increased, and thus the effect of increasing the amount of conductive component dissolved by Te can be sufficiently obtained.
前記複合粒子は前記Te化合物粒子がTeO2換算で前記ガラスフリット粒子100質量部に対して0.1〜60質量部の範囲で付着したものである。Te化合物粒子が0.1質量部以上の割合で含まれていれば、Teによる導電成分溶解量の増大による電気特性向上効果を十分に享受できる。また、Te化合物粒子が60質量部以下の割合に留められていれば、Te化合物粒子が凝集することによって複合粒子が得られ難くなることが十分に抑制される。 The composite particles are obtained by attaching the Te compound particles in a range of 0.1 to 60 parts by mass with respect to 100 parts by mass of the glass frit particles in terms of TeO 2 . If Te compound particles are contained at a ratio of 0.1 parts by mass or more, the effect of improving electrical characteristics due to an increase in the amount of conductive component dissolved by Te can be fully enjoyed. Further, if the Te compound particles are kept at a ratio of 60 parts by mass or less, it is sufficiently suppressed that the composite particles are hardly obtained due to aggregation of the Te compound particles.
なお、ガラスフリット粒子とTe化合物粒子との質量比は、以下の理論によって好ましい範囲が与えられる。Herseyが提唱した「Ordered Mixture」と称される概念によれば、相対的に大きいホスト粒子と、それよりも十分に小さいゲスト粒子とを混合したとき、ホスト粒子の表面にゲスト粒子が付着した状態となり、極めて均質な混合物として取り扱うことができる。特に、ゲスト粒子の粒径がホスト粒子の粒径の1/10以下であるときには、ホスト粒子の表面がゲスト粒子で均一にコーティングされた複合粒子が得られる。直径Ｄのホスト粒子の表面に直径ｄのゲスト粒子が規則的に六方最密充填状態で、すなわち、重なり無く密接して粒子一層の厚みで配列する場合、ゲスト粒子の個数Ｎhexは下記(１)式で与えられる。
Ｎhex＝(2π／√3)[(D/d)＋1]2 ・・・(１)
The mass ratio between the glass frit particles and the Te compound particles is given a preferable range by the following theory. According to the concept called “Ordered Mixture” proposed by Hersey, when a relatively large host particle and a guest particle sufficiently smaller than that are mixed, the guest particle adheres to the surface of the host particle. And can be handled as a very homogeneous mixture. In particular, when the particle size of the guest particles is 1/10 or less of the particle size of the host particles, composite particles in which the surface of the host particles is uniformly coated with the guest particles can be obtained. When guest particles having a diameter d are regularly packed in a hexagonal close-packed state on the surface of a host particle having a diameter D, that is, arranged in a single layer thickness without overlapping, the number N hex of guest particles is as follows: ).
N hex = (2π / √3) [(D / d) +1] 2 (1)
実際には、ゲスト粒子はある程度の空隙を含む不規則充填状態をとるため、ゲスト粒子の中心間隔が平均してλｄであるとすると、ゲスト粒子の個数Ｎrndは下記(２)式で与えられる。λの値は、モデルシミュレーションから約４/３が適当とされる。これが粒子一層の厚みでホスト粒子の表面にゲスト粒子が重なり無く配列するときの最大粒子数であり、これを越えるとゲスト粒子が過剰となって凝集が生じ易くなる。
Ｎrnd＝Ｎhex／λ2 ・・・(２)
Actually, since the guest particles are in an irregularly packed state including a certain amount of voids, the number N rnd of guest particles is given by the following equation (2) when the center interval of guest particles is λd on average. . An appropriate value of λ is about 4/3 from model simulation. This is the maximum number of particles when the guest particles are arranged on the surface of the host particle without overlapping with the thickness of one layer of the particle, and if it exceeds this, the guest particles become excessive and aggregation tends to occur.
N rnd = N hex / λ 2 (2)
本願においてはガラスフリット粒子がホスト粒子、Te化合物粒子がゲスト粒子に対応するが、これらは密度が互いに異なるため、ホスト粒子の密度をρh、ゲスト粒子の密度をρgとして、それらの質量比の上限ｒmは下記(３)式に示すように上記Ｎrndを１個の粒子の質量比で除することで得られる。Te化合物量は、上記の最大粒子数が最善、すなわち、Te化合物粒子が重なり無く可及的に多くガラスフリット粒子の表面に固着することが最善と考えられるが、これよりもある程度少なくとも、或いはこれよりもある程度多くとも(すなわち重なりが少々生じても、或いは、ガラスフリット粒子に固着されないTe化合物粒子が少々生じても)十分に良好な特性が得られる。前記上限値「60質量部」は、ガラスフリット粒子の密度3.4(g/cm3)、TeO2粒子の密度5.8(g/cm3)、粒径比(D/d)1/10として、得られる計算値「42.1質量部」に対して、重なりを許容し得るTeO2粒子量の上限に当たるものと考えられる。本願発明においては、複合粒子は、このようにTe化合物粒子がガラスフリットの粒子表面に粒子一層の厚みで固着されたものであることが好ましい。
ｒm＝Ｎrnd／[(D3×ρh)／(d3×ρg)] ・・・(３)
In the present application, glass frit particles correspond to host particles, and Te compound particles correspond to guest particles, but these have different densities, so the density of host particles is ρ h and the density of guest particles is ρ g. the upper limit r m obtained by dividing by the following (3) the weight ratio of one particle of the N rnd as shown in the expression. Regarding the amount of Te compound, it is considered that the above maximum number of particles is the best, that is, it is best that the Te compound particles adhere to the surface of the glass frit particles as much as possible without overlapping, but at least to some extent, or this Sufficiently good characteristics (that is, even if there is a little overlap or even a few Te compound particles not fixed to the glass frit particles). The upper limit “60 parts by mass” is obtained as a density of glass frit particles of 3.4 (g / cm 3 ), a density of TeO 2 particles of 5.8 (g / cm 3 ), and a particle size ratio (D / d) of 1/10. The calculated value of “42.1 parts by mass” is considered to be the upper limit of the amount of TeO 2 particles that can be allowed to overlap. In the present invention, the composite particles are preferably particles in which the Te compound particles are fixed to the particle surface of the glass frit with a thickness of one particle.
r m = N rnd / [(D 3 × ρ h ) / (d 3 × ρ g )] (3)
なお、前記ガラスフリットは、特に限定されず、太陽電池用導電性ペースト組成物に通常用いられるPbO-SiO2-B2O3系、SiO2-B2O3-ZnO系等の適宜のものを適用し得る。 The glass frit is not particularly limited, and may be an appropriate one such as a PbO—SiO 2 —B 2 O 3 type or SiO 2 —B 2 O 3 —ZnO type usually used for a conductive paste composition for solar cells. Can be applied.
また、本発明において、Te化合物は、特に限定されず、ファイヤースルーの際に変化し難い適宜の化合物を用い得る。例えば、テルル化亜鉛、テルル化カドミウム、テルル化水銀、テルル化鉛、テルル化ビスマス、テルル化銀等のテルル化金属、二酸化テルル、三酸化テルル等のテルル酸化物、オルトテルル酸、亜テルル酸等のオキソ酸とその塩、水酸化テルル等の水酸化物、塩化テルル、四臭化テルル等のハロゲン化物、硫酸ジテルル、燐酸テルル等の塩、テルル酸、メタテルル酸等とその塩等の無機化合物、ジアリールテルリド等のテルリド、ビス(４−メトキシフェニル)テルロキシド等のテルロキシド、メチルフェニルテルロン等のテルロン等の有機化合物、これらの混合物或いは複合化物が挙げられる。 In the present invention, the Te compound is not particularly limited, and an appropriate compound that hardly changes during fire-through can be used. For example, zinc telluride, cadmium telluride, mercury telluride, lead telluride, bismuth telluride, telluride metals such as silver telluride, tellurium oxide, tellurium oxide such as tellurium trioxide, orthotelluric acid, telluric acid, etc. Oxoacids and salts thereof, hydroxides such as tellurium hydroxide, halides such as tellurium chloride and tellurium tetrabromide, salts such as ditelluric sulfate and tellurium phosphate, and inorganic compounds such as telluric acid and metatelluric acid and salts thereof And tellurides such as diaryl telluride, telluroxides such as bis (4-methoxyphenyl) telluroxide, organic compounds such as telluron such as methylphenyl telluron, and mixtures or composites thereof.
また、好適には、前記導電性粉末は、Ag粉末である。本発明が適用される導電性ペースト組成物に含まれる導電性粉末は特に限定されず、Au,Ag,Cu,Al等が挙げられる。この中でも、AgはTeが存在することによる溶解量増大効果が顕著に得られるため、本願発明の適用対象として特に好ましい。 Preferably, the conductive powder is an Ag powder. The conductive powder contained in the conductive paste composition to which the present invention is applied is not particularly limited, and examples thereof include Au, Ag, Cu, and Al. Among these, Ag is particularly preferable as an application target of the present invention because an effect of increasing the dissolution amount due to the presence of Te is remarkably obtained.
また、好適には、前記ガラスフリットは平均粒径(D50)が0.3〜6(μm)の範囲内である。ガラスフリットの平均粒径が小さすぎると、電極の焼成時に融解が早すぎるため電気的特性が低下すると共に、Te化合物粒子に対して十分に大きい粒径とすることが困難になる。平均粒径が0.3(μm)以上であれば、これらの問題が生じ難い。しかも、凝集が生じ難いのでペースト調製時に一層良好な分散性が得られる。また、ガラスフリットの平均粒径が導電性粉末の平均粒径よりも著しく大きい場合にも粉末全体の分散性が低下するが、6(μm)以下であれば一層良好な分散性が得られる。しかも、ガラスの一層の熔融性が得られる。 Preferably, the glass frit has an average particle diameter (D50) in the range of 0.3 to 6 (μm). If the average particle size of the glass frit is too small, the melting is too early when the electrode is fired, so that the electrical characteristics are lowered and it is difficult to make the particle size sufficiently larger than the Te compound particles. If the average particle size is 0.3 (μm) or more, these problems are unlikely to occur. In addition, since agglomeration is unlikely to occur, better dispersibility can be obtained during paste preparation. Also, the dispersibility of the whole powder is lowered when the average particle size of the glass frit is significantly larger than the average particle size of the conductive powder, but better dispersibility can be obtained when it is 6 (μm) or less. Moreover, a further meltability of the glass can be obtained.
なお、上記ガラスフリットの平均粒径は空気透過法による値である。空気透過法は、粉体層に対する流体(例えば空気)の透過性から粉体の比表面積を測定する方法をいう。この測定方法の基礎となるのは、粉体層を構成する全粒子の濡れ表面積とそこを通過する流体の流速および圧力降下の関係を示すコゼニー・カーマン(Kozeny-Carmann)の式であり、装置によって定められた条件で充填された粉体層に対する流速と圧力降下を測定して試料の比表面積を求める。この方法は充填された粉体粒子の間隙を細孔と見立てて、空気の流れに抵抗となる粒子群の濡れ表面積を求めるもので、通常はガス吸着法で求めた比表面積よりも小さな値を示す。求められた上記比表面積および粒子密度から粉体粒子を仮定した平均粒径を算出できる。 The average particle size of the glass frit is a value obtained by the air permeation method. The air permeation method is a method for measuring the specific surface area of a powder from the permeability of a fluid (for example, air) to a powder layer. The basis of this measurement method is the Kozeny-Carmann equation, which shows the relationship between the wetted surface area of all particles making up the powder layer and the flow velocity and pressure drop of the fluid passing therethrough. The specific surface area of the sample is obtained by measuring the flow velocity and pressure drop with respect to the powder layer filled under the conditions determined by the above. In this method, the gap between the filled powder particles is regarded as pores, and the wetted surface area of the particles that resists the flow of air is determined. Usually, the value is smaller than the specific surface area determined by the gas adsorption method. Show. An average particle diameter assuming powder particles can be calculated from the obtained specific surface area and particle density.
また、好適には、前記Te化合物粒子は平均粒径(D50)が0.03〜0.4(μm)の範囲内である。Te化合物粒子は、この粒径の範囲内で、前記のガラスフリット粒子との粒径比となるように適宜の粒径のものを用い得る。 Preferably, the Te compound particles have an average particle diameter (D50) in the range of 0.03 to 0.4 (μm). Te compound particles having an appropriate particle size can be used so that the particle size ratio with the glass frit particles is within the range of the particle size.
また、好適には、前記導電性粉末は平均粒径(D50)が0.3〜3.0(μm)の範囲内の銀粉末である。導電性粉末としては銅粉末やニッケル粉末等も用い得るが、銀粉末が高い導電性を得るために最も好ましい。また、銀粉末の平均粒径が3.0(μm)以下であれば一層良好な分散性が得られるので一層高い導電性が得られる。また、0.3(μm)以上であれば凝集が抑制されて一層良好な分散性が得られる。なお、0.3(μm)未満の銀粉末は著しく高価であるため、製造コストの面からも0.3(μm)以上が好ましい。また、導電性粉末、ガラスフリット共に平均粒径が3.0(μm)以下であれば、細線パターンで電極を印刷形成する場合にも目詰まりが生じ難い利点がある。 Preferably, the conductive powder is a silver powder having an average particle diameter (D50) in the range of 0.3 to 3.0 (μm). Although copper powder, nickel powder, etc. can be used as the conductive powder, silver powder is most preferable in order to obtain high conductivity. Further, if the average particle size of the silver powder is 3.0 (μm) or less, better dispersibility can be obtained, and thus higher conductivity can be obtained. Moreover, if it is 0.3 (μm) or more, aggregation is suppressed and better dispersibility can be obtained. Since silver powder of less than 0.3 (μm) is extremely expensive, 0.3 (μm) or more is preferable from the viewpoint of manufacturing cost. Further, if the average particle diameter of both the conductive powder and the glass frit is 3.0 (μm) or less, there is an advantage that clogging hardly occurs even when the electrode is printed by a fine line pattern.
なお、前記銀粉末は特に限定されず、球状や鱗片状等、どのような形状の粉末が用いられる場合にも導電性を保ったまま細線化が可能である。但し、球状粉を用いた場合が印刷性に優れると共に、塗布膜における銀粉末の充填率が高くなるため、導電性の高い銀が用いられることと相俟って、鱗片状等の他の形状の銀粉末が用いられる場合に比較して、その塗布膜から生成される電極の導電率が高くなる。そのため、必要な導電性を確保したまま線幅を一層細くすることが可能となることから、特に好ましい。 The silver powder is not particularly limited, and thinning can be performed while maintaining conductivity even when a powder of any shape such as a spherical shape or a scale shape is used. However, when the spherical powder is used, the printability is excellent and the filling rate of the silver powder in the coating film is increased, so that, together with the use of highly conductive silver, other shapes such as scales are used. Compared with the case where the silver powder of this is used, the electrical conductivity of the electrode produced | generated from the coating film becomes high. Therefore, it is particularly preferable because the line width can be further reduced while ensuring the necessary conductivity.
また、好適には、前記太陽電池用導電性ペースト組成物は、25(℃)−20(rpm)における粘度が150〜250(Pa・s)の範囲内、粘度比(すなわち、［10(rpm)における粘度］/［100(rpm)における粘度］)が3〜8である。このような粘度特性を有するペーストを用いることにより、スキージングの際に好適に低粘度化してスクリーンメッシュを透過し、その透過後には高粘度に戻って印刷幅の広がりが抑制されるので、スクリーンを容易に透過して目詰まりを生じないなど印刷性を保ったまま細線パターンが容易に得られる。ペースト組成物の粘度は、160〜200(Pa・s)の範囲が一層好ましく、粘度比は3.2〜6.5の範囲が一層好ましい。また、設計線幅が100(μm)以下の細線化には粘度比4〜6が望ましい。 Preferably, the conductive paste composition for solar cells has a viscosity ratio (that is, [10 (rpm) within a range of 150 to 250 (Pa · s) at 25 (° C.) to 20 (rpm). )] / [Viscosity at 100 (rpm)]) is 3-8. By using a paste having such a viscosity characteristic, the viscosity is suitably reduced during squeezing and transmitted through the screen mesh. After the transmission, the viscosity returns to a high viscosity and the expansion of the printing width is suppressed. Thus, a fine line pattern can be easily obtained while maintaining the printability such that clogging does not easily occur and clogging does not occur. The viscosity of the paste composition is more preferably in the range of 160 to 200 (Pa · s), and the viscosity ratio is more preferably in the range of 3.2 to 6.5. In addition, a viscosity ratio of 4 to 6 is desirable for thinning a design line width of 100 (μm) or less.
なお、線幅を細くしても断面積が保たれるように膜厚を厚くすることは、例えば、印刷製版の乳剤厚みを厚くすること、テンションを高くすること、線径を細くして開口径を広げること等でも可能である。しかしながら、乳剤厚みを厚くすると版離れが悪くなるので印刷パターン形状の安定性が得られなくなる。また、テンションを高くし或いは線径を細くすると、スクリーンメッシュが伸び易くなるので寸法・形状精度を保つことが困難になると共に印刷製版の耐久性が低下する問題がある。しかも、太幅で設けられることから膜厚を厚くすることが無用なバスバーも厚くなるため、材料の無駄が多くなる問題もある。 Note that increasing the film thickness so that the cross-sectional area can be maintained even if the line width is reduced includes, for example, increasing the emulsion thickness of the printing plate, increasing the tension, and reducing the line diameter. It is also possible to widen the aperture. However, when the emulsion thickness is increased, the separation of the plate is deteriorated, so that the stability of the printed pattern shape cannot be obtained. In addition, when the tension is increased or the wire diameter is reduced, the screen mesh is easily stretched, so that it is difficult to maintain the dimensional and shape accuracy and the durability of the printing plate making is lowered. In addition, since it is provided with a large width, a bus bar that is unnecessary to increase the film thickness is also increased, resulting in a problem of waste of material.
また、好適には、前記太陽電池用導電性ペースト組成物は、前記導電性粉末を64〜90重量部、前記ベヒクルを3〜20重量部の範囲内の割合で含むものである。このようにすれば、印刷性が良好で線幅の細く導電性の高い電極を容易に形成できるペースト組成物が得られる。 Preferably, the conductive paste composition for a solar cell includes the conductive powder in a proportion in the range of 64 to 90 parts by weight and the vehicle in a range of 3 to 20 parts by weight. In this way, a paste composition can be obtained that can easily form an electrode having good printability, thin line width, and high conductivity.
また、好適には、前記導電性ペースト組成物は、前記ガラスフリットを前記導電性粉末100重量部に対して1〜10重量部の範囲で含むものである。1重量部以上含まれていれば十分な浸食性(ファイヤスルー性)が得られるので、良好なオーミックコンタクトが得られる。また、10重量部以下に留められていれば絶縁層が形成され難いので十分な導電性が得られる。導電性粉末100重量部に対するガラス量は、1〜8重量部が一層好ましく、1〜7重量部が更に好ましい。 Preferably, the conductive paste composition contains the glass frit in a range of 1 to 10 parts by weight with respect to 100 parts by weight of the conductive powder. If it is contained in an amount of 1 part by weight or more, sufficient erosion property (fire-through property) can be obtained, so that a good ohmic contact can be obtained. Further, if it is kept at 10 parts by weight or less, it is difficult to form an insulating layer, and sufficient conductivity can be obtained. The amount of glass based on 100 parts by weight of the conductive powder is more preferably 1 to 8 parts by weight, and still more preferably 1 to 7 parts by weight.
また、本願発明の製造方法により製造された導電性ペースト組成物は、裏面電極形成に用いることもできるが、前述したようにファイヤースルーによる電極形成時の銀の析出を好適に制御し得るものであるから、受光面電極に好適に用い得る。 In addition, the conductive paste composition produced by the production method of the present invention can also be used for the formation of the back electrode, but as described above, it can suitably control the silver precipitation during the electrode formation by fire-through. Therefore, it can be suitably used for the light-receiving surface electrode.
以下、本発明の一実施例を図面を参照して詳細に説明する。なお、以下の実施例において図は適宜簡略化或いは変形されており、各部の寸法比および形状等は必ずしも正確に描かれていない。 Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.
図１は、本発明の一実施例の導電性組成物が適用されたシリコン系太陽電池１０を備えた太陽電池モジュール１２の断面構造を模式的に示す図である。図１において、太陽電池モジュール１２は、上記太陽電池１０と、これを封止する封止材１４と、受光面側において封止材１４上に設けられた表面ガラス１６と、裏面側から太陽電池１０および封止材１４を保護するために設けられた保護フィルム(すなわちバックシート)１８とを備えている。上記封止材１４は、例えば、ＥＶＡから成るもので、十分な耐候性を有するように、架橋剤、紫外線吸収剤、接着保護剤等が適宜配合されている。また、上記保護フィルム１８は、例えば弗素樹脂やポリエチレンテレフタレート(ＰＥＴ)樹脂、或いはＰＥＴやＥＶＡ等から成る樹脂フィルムを複数枚貼り合わせたもの等から成るもので、高い耐候性や水蒸気バリア性等を備えている。 FIG. 1 is a diagram schematically showing a cross-sectional structure of a solar cell module 12 including a silicon-based solar cell 10 to which a conductive composition according to an embodiment of the present invention is applied. In FIG. 1, the solar cell module 12 includes the solar cell 10, a sealing material 14 for sealing the solar cell 10, a surface glass 16 provided on the sealing material 14 on the light receiving surface side, and a solar cell from the back surface side. 10 and a protective film (that is, a back sheet) 18 provided to protect the sealing material 14. The sealing material 14 is made of, for example, EVA, and is appropriately blended with a crosslinking agent, an ultraviolet absorber, an adhesion protective agent and the like so as to have sufficient weather resistance. The protective film 18 is made of, for example, fluorine resin, polyethylene terephthalate (PET) resin, or a laminate of a plurality of resin films made of PET, EVA, etc., and has high weather resistance, water vapor barrier properties, etc. I have.
また、上記の太陽電池１０は、例えばｐ型多結晶半導体であるシリコン基板２０と、その上下面にそれぞれ形成されたｎ層２２およびｐ+層２４と、そのｎ層２２上に形成された反射防止膜２６および受光面電極２８と、そのｐ+層２４上に形成された裏面電極３０とを備えている。上記シリコン基板２０の厚さ寸法は例えば100〜200(μm)程度である。 The solar cell 10 includes, for example, a silicon substrate 20 which is a p-type polycrystalline semiconductor, an n layer 22 and a p + layer 24 respectively formed on the upper and lower surfaces thereof, and a reflection formed on the n layer 22. A prevention film 26 and a light receiving surface electrode 28, and a back electrode 30 formed on the p + layer 24 are provided. The thickness dimension of the silicon substrate 20 is, for example, about 100 to 200 (μm).
上記のｎ層２２およびｐ+層２４は、シリコン基板２０の上下面に不純物濃度の高い層を形成することで設けられたもので、その高濃度層の厚さ寸法はｎ層２２が例えば70〜100(nm)程度、ｐ+層２４が例えば500(nm)程度である。ｎ層２２は、一般的なシリコン系太陽電池では100〜200(nm)程度であるが、本実施例ではそれよりも薄くなっており、シャローエミッタと称される構造を成している。なお、ｎ層２２に含まれる不純物は、ｎ型のドーパント、例えば燐(P)で、ｐ+層２４に含まれる不純物は、ｐ型のドーパント、例えばアルミニウム(Al)や硼素(B)である。 The n layer 22 and the p + layer 24 are provided by forming layers having a high impurity concentration on the upper and lower surfaces of the silicon substrate 20, and the thickness dimension of the high concentration layer is, for example, 70 n. ˜100 (nm), and the p + layer 24 is about 500 (nm), for example. The n layer 22 is about 100 to 200 (nm) in a general silicon-based solar cell, but is thinner than that in this embodiment, and has a structure called a shallow emitter. The impurity contained in the n layer 22 is an n-type dopant such as phosphorus (P), and the impurity contained in the p + layer 24 is a p-type dopant such as aluminum (Al) or boron (B). .
また、前記の反射防止膜２６は、例えば、窒化珪素 Si3N4等から成る薄膜で、例えば可視光波長の１／４程度の光学的厚さ、例えば80(nm)程度で設けられることによって10(％)以下、例えば2(％)程度の極めて低い反射率に構成されている。 The antireflection film 26 is a thin film made of, for example, silicon nitride Si 3 N 4 , and is provided with an optical thickness of, for example, about 1/4 of the visible light wavelength, for example, about 80 (nm). It is configured to have an extremely low reflectance of 10 (%) or less, for example, 2 (%).
また、前記の受光面電極２８は、例えば一様な厚さ寸法の厚膜導体から成るもので、図２に示されるように、受光面３２の略全面に、多数本の細線部を有する櫛状を成す平面形状で設けられている。 The light receiving surface electrode 28 is made of, for example, a thick film conductor having a uniform thickness. As shown in FIG. 2, the light receiving surface electrode 28 is a comb having a large number of thin line portions substantially on the entire surface of the light receiving surface 32. Are provided in a planar shape.
上記の厚膜導体は、Ag、ガラス、およびTe化合物を含む厚膜銀から成るもので、Ag 100重量部に対してガラスおよびTe化合物の合計量が1〜10重量部の範囲内、例えば、4.8重量部程度、ガラスを100重量部に対して、Te化合物量が0.1〜60重量部の範囲内、例えば、15重量部程度の割合で含まれる。上記ガラスは、例えば、PbO-SiO2-B2O3系の鉛ガラス、或いはSiO2-B2O3-ZnO系の無鉛ガラスであり、これら主要成分の他にS、Li、P、Al等を含むものが好ましいが、その組成は特に限定されず、一般に太陽電池の電極用とされる適宜のものが用いられている。また、上記Te化合物量は、含有形態に拘わらずTeO2換算した値である。 The above thick film conductor is composed of thick film silver containing Ag, glass, and Te compound, and the total amount of glass and Te compound is in the range of 1 to 10 parts by weight with respect to 100 parts by weight of Ag, for example, About 4.8 parts by weight, with respect to 100 parts by weight of glass, the amount of Te compound is contained in the range of 0.1 to 60 parts by weight, for example, about 15 parts by weight. The glass is, for example, PbO—SiO 2 —B 2 O 3 based lead glass or SiO 2 —B 2 O 3 —ZnO based lead-free glass. In addition to these main components, S, Li, P, Al However, the composition is not particularly limited, and an appropriate material generally used for an electrode of a solar cell is used. The amount of the Te compound is a value converted to TeO 2 regardless of the content form.
また、上記の導体層の厚さ寸法は例えば20〜30(μm)の範囲内、例えば25(μm)程度で、細線部の各々の幅寸法は例えば80〜130(μm)の範囲内、例えば100(μm)程度で、十分に高い導電性を備えている。 In addition, the thickness dimension of the conductor layer is, for example, in the range of 20-30 (μm), for example, about 25 (μm), and the width dimension of each thin wire portion is, for example, in the range of 80-130 (μm), for example, It is about 100 (μm) and has sufficiently high conductivity.
また、前記の裏面電極３０は、ｐ+層２４上にアルミニウムを導体成分とする厚膜材料を略全面に塗布して形成された全面電極３４と、その全面電極３４上に帯状に塗布して形成された厚膜銀から成る帯状電極３６とから構成されている。この帯状電極３６は、裏面電極３０に半田リボン３８や導線等を半田付け可能にするために設けられたものである。前記受光面電極２８にも裏面側と同様に半田リボン３８が溶着されている。 The back electrode 30 is formed by applying a full-surface electrode 34 formed by applying a thick film material containing aluminum as a conductor component on the p + layer 24 over substantially the entire surface, and a strip-like application on the full-surface electrode 34. The band-shaped electrode 36 made of thick silver is formed. The strip electrode 36 is provided in order to make it possible to solder a solder ribbon 38 or a conductive wire to the back electrode 30. A solder ribbon 38 is welded to the light receiving surface electrode 28 in the same manner as the back surface side.
上記のような受光面電極２８は、例えば、導体粉末と、ガラスフリットの表面にTe化合物が固着した複合粒子と、ベヒクルと、溶剤とから成る電極用ペーストを用いて良く知られたファイヤースルー法によって形成されたものである。その受光面電極形成を含む太陽電池１０の製造方法の一例を以下に説明する。 The light-receiving surface electrode 28 as described above is, for example, a well-known fire-through method using an electrode paste composed of conductive powder, composite particles in which a Te compound is fixed to the surface of a glass frit, a vehicle, and a solvent. It is formed by. An example of the manufacturing method of the solar cell 10 including the formation of the light receiving surface electrode will be described below.
まず、上記ガラスフリットを作製する。S源として硫酸アンモニウム (NH4)2SO4を、Li源として炭酸リチウム Li2CO3を、P源としてリン酸二水素アンモニウム NH4H2PO4を、Si源として二酸化珪素 SiO2を、B源として硼酸H3BO3を、Pb源として鉛丹 Pb3O4を、Al源として酸化アルミニウム Al2O3を、それぞれ用意し、所望するガラス組成になるように秤量して調合する。これを坩堝に投入して組成に応じた900〜1200(℃)の範囲内の温度で、30分〜1時間程度溶融し、急冷することでガラス化させる。このガラスを遊星ミルやボールミル等の適宜の粉砕装置を用いて粉砕する。粉砕時間は1〜8時間程度、粉砕後の平均粒径(D50)は例えば0.3〜6(μm)程度である。なお、上記ガラス粉末の平均粒径は空気透過法を用いて算出したものである。 First, the glass frit is produced. Ammonium sulfate (NH 4 ) 2 SO 4 as S source, lithium carbonate Li 2 CO 3 as Li source, ammonium dihydrogen phosphate NH 4 H 2 PO 4 as P source, silicon dioxide SiO 2 as Si source, B Prepare boric acid H 3 BO 3 as a source, red lead Pb 3 O 4 as a Pb source, and aluminum oxide Al 2 O 3 as an Al source, and weigh and prepare them to obtain a desired glass composition. This is put into a crucible, melted at a temperature in the range of 900 to 1200 (° C.) according to the composition for about 30 minutes to 1 hour, and rapidly cooled to be vitrified. This glass is pulverized using an appropriate pulverizing apparatus such as a planetary mill or a ball mill. The pulverization time is about 1 to 8 hours, and the average particle size (D50) after pulverization is about 0.3 to 6 (μm), for example. In addition, the average particle diameter of the said glass powder is computed using the air permeation method.
また、Te化合物として例えばTeO2粉末を用意する。TeO2粉末は、例えば、平均粒径が10(μm)程度の市販の粉末(例えば、稀産金属株式会社製)である。これを遊星ミルやボールミル等の適宜の粉砕装置を用いて粉砕する。粉砕時間は1〜8時間程度、粉砕後の平均粒径は0.03〜0.4(μm)程度とした。 Further, for example, TeO 2 powder is prepared as a Te compound. TeO 2 powder is, for example, a commercially available powder (for example, manufactured by Rare Metal Co., Ltd.) having an average particle size of about 10 (μm). This is pulverized using an appropriate pulverizer such as a planetary mill or a ball mill. The pulverization time was about 1 to 8 hours, and the average particle size after pulverization was about 0.03 to 0.4 (μm).
次いで、このようにしてそれぞれ用意したガラス粉末およびTeO2粉末を、例えばメカノケミカル法によって複合化処理する。この複合化処理には、例えば、ホソカワミクロン(株)製ノビルタ NOB-130を用いたが、処理装置は特に限定されない。複合化処理の運転条件は、例えば、羽根回転数を2500(rpm)、処理時間を10〜20分間の範囲内、例えば10分間、動力負荷を4.5〜5.0(kW)の範囲内、例えば4.7(kW)とした。羽根と容器内面と間には3(mm)程度の隙間が設けられており、容器内に材料を投入して運転すると、ガラス粉末およびTeO2粉末が混合され、更には機械的作用力が加えられることでTeO2粉末がガラス粉末表面に一粒子層の厚みで強固に固着され、複合粒子が得られる。本実施例においては、このようにして製造した複合粒子が通常のペーストのガラスフリットに代えて用いられる。 Next, the glass powder and TeO 2 powder respectively prepared in this way are combined by a mechanochemical method, for example. For this composite treatment, for example, Nobilta NOB-130 manufactured by Hosokawa Micron Corporation was used, but the treatment apparatus is not particularly limited. The operating conditions of the composite treatment are, for example, a blade rotation speed of 2500 (rpm), a treatment time in the range of 10 to 20 minutes, for example, 10 minutes, and a power load in the range of 4.5 to 5.0 (kW), for example, 4.7 ( kW). A gap of about 3 (mm) is provided between the blade and the inner surface of the container. When the material is put into the container and operated, glass powder and TeO 2 powder are mixed, and mechanical working force is added. As a result, the TeO 2 powder is firmly fixed to the surface of the glass powder with a thickness of one particle layer, and composite particles are obtained. In this embodiment, the composite particles produced in this way are used in place of ordinary paste glass frit.
図３は、作成した複合粒子の電子顕微鏡写真、図４、図５はその図３に対応する複合粒子のEDX(エネルギー分散型Ｘ線分析)マッピング結果であって、それぞれSiピーク、Teピークを示す図である。図示は省略するが、Zn、Pb、Al、O等の各ピークもSiピークと同様な分布を示している。図３において中央に位置する粒径5(μm)程度の粒子は、図４のSiピーク等からガラス粉であることが判る。図５のTeピークもそれよりも低濃度であるが同様なパターンで一様な分布を示しており、ガラス粉末の周囲にTeO2が均一にコーティングされていることが明らかである。 3 is an electron micrograph of the prepared composite particles, and FIGS. 4 and 5 are EDX (energy dispersive X-ray analysis) mapping results of the composite particles corresponding to FIG. FIG. Although illustration is omitted, each peak of Zn, Pb, Al, O, etc. shows the same distribution as the Si peak. In FIG. 3, the particle having a particle size of about 5 (μm) located in the center is found to be glass powder from the Si peak in FIG. Although the Te peak in FIG. 5 has a lower concentration than that, it shows a uniform distribution with a similar pattern, and it is clear that TeO 2 is uniformly coated around the glass powder.
また、導体粉末として、例えば、平均粒径(D50)が0.3〜3.0(μm)の範囲内、例えば平均粒径が1.6(μm)程度の市販の球状の銀粉末を用意する。このような平均粒径が十分に小さい銀粉末を用いることにより、塗布膜における銀粉末の充填率を高め延いては導体の導電率を高めることができる。また、前記ベヒクルは、有機溶剤に有機結合剤を溶解させて調製したもので、有機溶剤としては、例えばブチルカルビトールアセテートが、有機結合剤としては、例えばエチルセルロースが用いられる。ベヒクル中のエチルセルロースの割合は例えば15(wt%)程度である。また、ベヒクルとは別に添加する溶剤は、例えばブチルカルビトールアセテートである。すなわち、これに限定されるものではないが、ベヒクルに用いたものと同じ溶剤でよい。この溶剤は、ペーストの粘度調整の目的で添加される。 As the conductor powder, for example, a commercially available spherical silver powder having an average particle size (D50) in the range of 0.3 to 3.0 (μm), for example, an average particle size of about 1.6 (μm) is prepared. By using such silver powder having a sufficiently small average particle diameter, the filling rate of the silver powder in the coating film can be increased and the electrical conductivity of the conductor can be increased. The vehicle is prepared by dissolving an organic binder in an organic solvent. For example, butyl carbitol acetate is used as the organic solvent, and ethyl cellulose is used as the organic binder. The ratio of ethyl cellulose in the vehicle is, for example, about 15 (wt%). A solvent added separately from the vehicle is, for example, butyl carbitol acetate. That is, although it is not limited to this, the same solvent as that used for the vehicle may be used. This solvent is added for the purpose of adjusting the viscosity of the paste.
以上のペースト原料をそれぞれ用意して、例えば導体粉末を77〜90(wt%)の範囲内、例えば83(wt%)、複合粒子を1〜10(wt%)の範囲内、例えば4(wt%)、ベヒクルを5〜14(wt%)の範囲内、例えば8(wt%)、溶剤を2〜5(wt%)の範囲内、例えば5(wt%)の割合で秤量し、攪拌機等を用いて混合した後、例えば三本ロールミルで分散処理を行う。これにより、前記電極用ペーストが得られる。 Prepare the above paste raw materials, for example, conductor powder in the range of 77 to 90 (wt%), for example 83 (wt%), composite particles in the range of 1 to 10 (wt%), for example 4 (wt %), The vehicle is weighed in the range of 5 to 14 (wt%), for example, 8 (wt%), the solvent is in the range of 2 to 5 (wt%), for example, 5 (wt%), and the stirrer etc. Then, for example, a dispersion treatment is performed with a three-roll mill. Thereby, the electrode paste is obtained.
上記のようにして電極用ペーストを調製する一方、適宜のシリコン基板に例えば、熱拡散法やイオンプランテーション等の良く知られた方法で不純物を拡散し或いは注入して前記ｎ層２２およびｐ+層２４を形成することにより、前記シリコン基板２０を作製する。次いで、これに例えばＰＥ−ＣＶＤ(プラズマＣＶＤ)等の適宜の方法で窒化珪素薄膜を形成し、前記反射防止膜２６を設ける。 While preparing the electrode paste as described above, the n layer 22 and the p + layer are diffused or implanted into an appropriate silicon substrate by a well-known method such as a thermal diffusion method or ion plantation. By forming 24, the silicon substrate 20 is produced. Next, a silicon nitride thin film is formed thereon by an appropriate method such as PE-CVD (plasma CVD), and the antireflection film 26 is provided.
次いで、上記の反射防止膜２６上に前記図２に示すパターンで前記電極用ペーストをスクリーン印刷する。これを例えば150(℃)で乾燥し、更に、近赤外炉において700〜900(℃)の範囲内の温度で焼成処理を施す。これにより、その焼成過程で電極用ペースト中のガラス成分が反射防止膜２６を溶かし、その電極用ペーストが反射防止膜２６を破るので、電極用ペースト中の導体成分すなわち銀とｎ層２２との電気的接続が得られ、前記図１に示されるようにシリコン基板２０と受光面電極２８とのオーミックコンタクトが得られる。受光面電極２８は、このようにして形成される。 Next, the electrode paste is screen-printed on the antireflection film 26 with the pattern shown in FIG. This is dried at, for example, 150 (° C.), and further subjected to a baking treatment at a temperature in the range of 700 to 900 (° C.) in a near infrared furnace. As a result, the glass component in the electrode paste melts the antireflection film 26 in the firing process, and the electrode paste breaks the antireflection film 26. Therefore, the conductor component in the electrode paste, that is, silver and the n layer 22 Electrical connection is obtained, and an ohmic contact between the silicon substrate 20 and the light-receiving surface electrode 28 is obtained as shown in FIG. The light receiving surface electrode 28 is formed in this way.
なお、前記裏面電極３０は、上記工程の後に形成してもよいが、受光面電極２８と同時に焼成して形成することもできる。裏面電極３０を形成するに際しては、上記シリコン基板２０の裏面全面に、例えばアルミニウムペーストをスクリーン印刷法等で塗布し、焼成処理を施すことによってアルミニウム厚膜から成る前記全面電極３４を形成する。更に、その全面電極３４の表面に前記電極用ペーストをスクリーン印刷法等を用いて帯状に塗布して焼成処理を施すことによって、前記帯状電極３６を形成する。これにより、裏面全面を覆う全面電極３４と、その表面の一部に帯状に設けられた帯状電極３６とから成る裏面電極３０が形成され、前記の太陽電池１０が得られる。上記工程において、同時焼成で製造する場合には、受光面電極２８の焼成前に印刷処理を施すことになる。 The back electrode 30 may be formed after the above process, but may be formed by firing at the same time as the light receiving surface electrode 28. When the back electrode 30 is formed, the full surface electrode 34 made of a thick aluminum film is formed on the entire back surface of the silicon substrate 20 by, for example, applying an aluminum paste by screen printing or the like and performing a baking process. Further, the strip electrode 36 is formed by applying the electrode paste on the surface of the entire surface electrode 34 in a strip shape by screen printing or the like and performing a baking treatment. Thereby, the back electrode 30 which consists of the full surface electrode 34 which covers the whole back surface, and the strip | belt-shaped electrode 36 provided in strip shape on a part of the surface is formed, and the said solar cell 10 is obtained. In the above process, when manufacturing by simultaneous firing, a printing process is performed before firing the light-receiving surface electrode 28.
本実施例の太陽電池１０は、上述したように受光面電極２８がファイヤースルー法で設けられているが、その受光面電極２８が、PbO-SiO2-B2O3系ガラスやSiO2-B2O3-ZnO系ガラスにTeO2を固着した複合粒子を含む厚膜銀ペーストを用いてファイヤースルーによって形成されていることから、Teの存在によってガラス中へのAg溶解量が増大するため、好適にオーミックコンタクトが得られ、電気的特性に優れた太陽電池１０が得られる。 In the solar cell 10 of this example, the light-receiving surface electrode 28 is provided by the fire-through method as described above, and the light-receiving surface electrode 28 is made of PbO—SiO 2 —B 2 O 3 glass or SiO 2 —. Because it is formed by fire-through using a thick film silver paste containing composite particles in which TeO 2 is fixed to B 2 O 3 -ZnO-based glass, the presence of Te increases the amount of Ag dissolved in the glass The ohmic contact is preferably obtained, and the solar cell 10 having excellent electrical characteristics can be obtained.
特に、本実施例においては、TeO2がメカノケミカル法によってガラスフリットの表面に一粒子層の厚みで固着されていることから、ペースト調製の際から、基板２０に塗布されて焼成処理を施されてガラスフリットが熔融するまでの間、ガラスフリット表面にTe化合物粒子が留まる。そのため、ファイヤースルーの際にガラス中へのAg溶解量の増大に寄与するTeの割合が増えることから、Teによる侵食抑制作用が許容できる程度にTe量を留めながら、ガラス中へのAg溶解量を十分に多くしてオーミックコンタクトを確保することができるので、ＦＦ値や出力特性等の電気特性を高め得る。 In particular, in this example, TeO 2 is fixed to the surface of the glass frit with a thickness of one particle layer by a mechanochemical method, so that it is applied to the substrate 20 and subjected to a firing treatment from the preparation of the paste. Until the glass frit melts, Te compound particles remain on the glass frit surface. Therefore, the proportion of Te that contributes to an increase in the amount of Ag dissolved in the glass during fire-through increases, so the amount of dissolved Ag in the glass while retaining the amount of Te to an extent that the erosion-inhibiting action by Te is acceptable. Since the ohmic contact can be ensured by sufficiently increasing the FF, electrical characteristics such as FF value and output characteristics can be improved.
すなわち、ガラスフリット表面に固着され得ない程度まで過剰に混合されたTe化合物は、ペースト中でガラスから遊離した状態となって、Ag溶解量の増大作用が低下すると共に侵食抑制作用が強くなる。そのため、複合粒子を作製するに際しては、Ag溶解量の増大効果の観点ではTe化合物量が多いことが望まれるが、その量はガラスフリット粒子の表面に全量が固着される範囲に留めることが望ましいと考えられる。その最適量は、ガラス粉末の比重および平均粒径と、Te化合物粉末の比重および平均粒径とによって定められるもので、前記(３)式によって求められる「質量比の上限ｒm」がそれである。実際に良好な特性が得られるTe量は、最適量を含む一定の広がりを有するもので、以下、幾つかのガラス系について適切な条件を検討した結果を説明する。 That is, the Te compound that is excessively mixed to such an extent that it cannot be fixed to the glass frit surface is released from the glass in the paste, and the action of increasing the amount of dissolved Ag is lowered and the action of erosion is strengthened. Therefore, when producing composite particles, it is desirable that the amount of Te compound is large from the viewpoint of the effect of increasing the amount of dissolved Ag, but it is desirable to keep the amount within the range in which the entire amount is fixed to the surface of the glass frit particles. it is conceivable that. The optimum amount is determined by the specific gravity and average particle diameter of the glass powder and the specific gravity and average particle diameter of the Te compound powder, and is the “upper limit r m of the mass ratio” obtained by the above equation (3). . The amount of Te with which good characteristics can be actually obtained has a certain spread including the optimum amount, and the results of studying appropriate conditions for several glass systems will be described below.
下記の表１〜３は、それぞれPbO-SiO2-B2O3系ガラス(比重4.8または5.3)およびSiO2-B2O3-ZnO系ガラス(比重3.4)の３種のガラスについて、TeO2との平均粒径の比および質量比を種々変更して評価した結果をまとめたものである。この評価では、ガラスの平均粒径を0.3〜6(μm)の範囲、TeO2粉末の平均粒径を0.03〜0.4(μm)の範囲、TeO2／ガラス粒径比を1/5〜1/50の範囲とした。また、これらの値とTeO2の比重5.8とから、前記(３)式で不規則充填の場合の最大質量比(ガラス100重量部に対する値)を求めると共に、それを含む一定幅の質量比の範囲で評価を行った。各試料は、何れも前述した製造工程に従ってペーストを調製して受光面電極２８を形成し太陽電池１０を製造して、その出力を測定してＦＦ値を求めた。太陽電池の出力は市販のソーラーシミュレータを用いて測定した。表１〜３において、「出力判定」は、ＦＦ値に基づいて適否を判断した結果を示したもので、ＦＦ値75以上を「○」(すなわち実施例)、75未満を「×」(すなわち比較例)とした。ＦＦ値は良好なオーミックコンタクトが得られているか否かの判定であり、一般に、太陽電池はＦＦ値が70以上であれば使用可能とされているが、高いほど好ましいのはもちろんであり、本実施例においては、ＦＦ値が75より大きいものを合格とした。 Tables 1 to 3 below show TeO for three types of glasses: PbO—SiO 2 —B 2 O 3 glass (specific gravity 4.8 or 5.3) and SiO 2 —B 2 O 3 —ZnO glass (specific gravity 3.4). 2 summarizes the results of various changes in the ratio of the average particle size to 2 and the mass ratio. In this evaluation, the average particle size of the glass is in the range of 0.3 to 6 (μm), the average particle size of the TeO 2 powder is in the range of 0.03 to 0.4 (μm), and the TeO 2 / glass particle size ratio is 1/5 to 1/1 /. The range was 50. Also, from these values and the specific gravity of TeO2 5.8, the maximum mass ratio (value for 100 parts by weight of glass) in the case of irregular filling is obtained by the above equation (3), and the range of the mass ratio of a constant width including it. Was evaluated. For each sample, a paste was prepared in accordance with the manufacturing process described above to form the light-receiving surface electrode 28, the solar cell 10 was manufactured, and the output was measured to obtain the FF value. The output of the solar cell was measured using a commercially available solar simulator. In Tables 1 to 3, the “output determination” indicates the result of determining suitability based on the FF value, and an FF value of 75 or more is “◯” (that is, an example), and less than 75 is “×” (that is, Comparative example). The FF value is a determination as to whether or not a good ohmic contact is obtained. In general, a solar cell can be used if the FF value is 70 or more. In the examples, those having an FF value greater than 75 were considered acceptable.
なお、各試料を用意するに際しては、印刷性を同等とするために、25(℃)−20(rpm)における粘度が220〜240(Pa・s)になるようにベヒクル量および溶剤量を適宜調整した。また、受光面電極２８を形成する際の印刷製版は、線径23(μm)のSUS325製スクリーンメッシュに20(μm)厚の乳剤を設けたものとした。また、グリッドラインの幅寸法が80(μm)となるように印刷条件を設定した。また、基板のシート抵抗は90±10(Ω/□)を用いて評価を行った。 When preparing each sample, the vehicle amount and the solvent amount are appropriately adjusted so that the viscosity at 25 (° C.)-20 (rpm) is 220 to 240 (Pa · s) in order to make the printability equal. It was adjusted. The printing plate making for forming the light-receiving surface electrode 28 was made by providing a 20 (μm) thick emulsion on a SUS325 screen mesh having a wire diameter of 23 (μm). The printing conditions were set so that the width of the grid line would be 80 (μm). The sheet resistance of the substrate was evaluated using 90 ± 10 (Ω / □).
表１は、比重4.8のPbO-SiO2-B2O3系ガラスの評価結果である。粒径比1/5では、不規則充填の計算値が71(%)であり、TeO2粉末量をこれを含む60〜80(%)の範囲としたところ、ＦＦ値は70〜73(%)に留まった。ガラス粉末の平均粒径を0.3〜6(μm)、TeO2の平均粒径を0.03〜0.2(μm)とした粒径比1/10〜1/40の範囲では、何れも十分に高いＦＦ値を得ることができた。すなわち、粒径比1/10では計算値29.8(%)に対し、TeO2量が20〜40(%)の範囲で、ガラス粉末粒径0.3(μm)の場合には75〜76(%)、2(μm)の場合には75〜77(%)のＦＦ値がそれぞれ得られた。TeO2量が50(%)では、何れもＦＦ値が74(%)に留まった。粒径比1/20では計算値13.6(%)に対し、TeO2量が5〜25(%)の範囲で76〜78(%)の高いＦＦ値が得られた。TeO2量が35(%)ではＦＦ値が74(%)に留まった。粒径比1/30では計算値8.8(%)に対し、TeO2量が0.1〜20(%)の範囲で76〜78(%)の高いＦＦ値が得られた。TeO2量が30(%)ではＦＦ値が74(%)に留まった。また、「単に混合」とあるのはメカノケミカル法を用いなかったもので、メカノケミカル法を用いた場合にＦＦ値が78(%)であったTeO2量が10(%)の条件でも、ＦＦ値が74(%)に留まった。粒径比1/40では計算値6.5(%)に対し、TeO2量が0.1〜15(%)の範囲で76〜77(%)の高いＦＦ値が得られた。TeO2量が25(%)ではＦＦ値が74(%)に留まった。粒径比1/50では計算値5.1(%)に対し、1〜10(%)の範囲で評価したが、ＦＦ値が73(%)に留まった。 Table 1 shows the evaluation results of PbO—SiO 2 —B 2 O 3 glass having a specific gravity of 4.8. When the particle size ratio is 1/5, the calculated value of irregular filling is 71 (%), and the TeO 2 powder amount is in the range of 60 to 80 (%) including this, the FF value is 70 to 73 (% ). FF value is sufficiently high in the range of particle size ratio of 1/10 to 1/40 where the average particle size of glass powder is 0.3-6 (μm) and the average particle size of TeO 2 is 0.03-0.2 (μm) Could get. That is, for the particle size ratio 1/10, the calculated value 29.8 (%), TeO 2 amount in the range of 20-40 (%), in the case of glass powder particle size 0.3 (μm) 75-76 (%) In the case of 2 (μm), FF values of 75 to 77 (%) were obtained. When the amount of TeO 2 was 50 (%), the FF value remained at 74 (%) in all cases. At a particle size ratio of 1/20, a high FF value of 76 to 78 (%) was obtained when the TeO 2 content was in the range of 5 to 25 (%) with respect to the calculated value of 13.6 (%). When the amount of TeO 2 was 35 (%), the FF value remained at 74 (%). When the particle size ratio was 1/30, a high FF value of 76 to 78 (%) was obtained when the TeO 2 content was in the range of 0.1 to 20 (%) with respect to the calculated value of 8.8 (%). When the amount of TeO 2 was 30 (%), the FF value remained at 74 (%). In addition, `` simply mixed '' means that the mechanochemical method was not used, and when the mechanochemical method was used, the FF value was 78 (%) and the TeO 2 amount was 10 (%), The FF value remained at 74 (%). At a particle size ratio of 1/40, a high FF value of 76 to 77 (%) was obtained when the TeO 2 content was in the range of 0.1 to 15 (%) with respect to the calculated value of 6.5 (%). When the amount of TeO 2 was 25 (%), the FF value remained at 74 (%). The particle size ratio 1/50 was evaluated in the range of 1 to 10 (%) with respect to the calculated value 5.1 (%), but the FF value remained at 73 (%).
表２は、比重5.3のPbO-SiO2-B2O3系ガラスの評価結果である。この評価結果において、粒径比1/5では、計算値64.3(%)に対し、TeO2粉末量が50〜70(%)の範囲で評価したが、ＦＦ値は70〜72(%)に留まった。粒径比1/10〜1/40の範囲では、何れも十分に高いＦＦ値を得ることができた。すなわち、粒径比1/10では計算値27.0(%)に対し、TeO2量が15〜35(%)の範囲で75〜78(%)のＦＦ値が得られた。TeO2量が1(%)或いは45(%)では、ＦＦ値が74(%)に留まった。また、単に混合した場合には、TeO2量が25(%)でもＦＦ値が74(%)に留まった。粒径比1/20では計算値12.3(%)に対し、TeO2量が0.2〜20(%)の範囲で76〜78(%)の高いＦＦ値が得られた。TeO2量が30(%)ではＦＦ値が74(%)に留まった。粒径比1/30では計算値7.9(%)に対し、TeO2量が0.1〜10(%)の範囲で76〜77(%)の高いＦＦ値が得られた。TeO2量が20(%)ではＦＦ値が74(%)に留まった。粒径比1/40では計算値5.9(%)に対し、TeO2量が0.1〜10(%)の範囲で76〜77(%)の高いＦＦ値が得られた。TeO2量が20(%)ではＦＦ値が74(%)に留まった。粒径比1/50では計算値4.6(%)に対し、TeO2量が1〜10(%)の範囲で評価したが、ＦＦ値が73〜74(%)に留まった。 Table 2 shows the evaluation results of PbO—SiO 2 —B 2 O 3 glass having a specific gravity of 5.3. In this evaluation result, when the particle size ratio was 1/5, the TeO 2 powder amount was evaluated in the range of 50 to 70 (%) with respect to the calculated value of 64.3 (%), but the FF value was 70 to 72 (%). Stayed. In the range of the particle size ratio of 1/10 to 1/40, sufficiently high FF values could be obtained. That is, when the particle size ratio was 1/10, FF values of 75 to 78 (%) were obtained when the TeO 2 content was in the range of 15 to 35 (%) with respect to the calculated value of 27.0 (%). When the amount of TeO 2 was 1 (%) or 45 (%), the FF value remained at 74 (%). In addition, when they were simply mixed, the FF value remained at 74 (%) even when the amount of TeO 2 was 25 (%). At a particle size ratio of 1/20, a high FF value of 76 to 78 (%) was obtained when the TeO 2 content was in the range of 0.2 to 20 (%) compared to the calculated value of 12.3 (%). When the amount of TeO 2 was 30 (%), the FF value remained at 74 (%). At a particle size ratio of 1/30, a high FF value of 76 to 77 (%) was obtained when the TeO 2 content was in the range of 0.1 to 10 (%) with respect to the calculated value of 7.9 (%). When the amount of TeO 2 was 20 (%), the FF value remained at 74 (%). At a particle size ratio of 1/40, a high FF value of 76 to 77 (%) was obtained when the TeO 2 content was in the range of 0.1 to 10 (%) with respect to the calculated value of 5.9 (%). When the amount of TeO 2 was 20 (%), the FF value remained at 74 (%). At a particle size ratio of 1/50, the TeO 2 content was evaluated in the range of 1 to 10 (%) with respect to the calculated value of 4.6 (%), but the FF value remained at 73 to 74 (%).
表３は、比重3.4のSiO2-B2O3-ZnO系ガラスの評価結果である。この評価結果において、粒径比1/5では、計算値100.2(%)に対し、TeO2粉末量が90〜110(%)の範囲で評価したが、ＦＦ値は67〜71(%)に留まった。粒径比1/10〜1/40の範囲では、何れも十分に高いＦＦ値を得ることができた。すなわち、粒径比1/10では計算値42.1(%)に対し、TeO2量が40〜60(%)の範囲で75〜76(%)のＦＦ値が得られた。TeO2量が1(%)或いは70(%)では、ＦＦ値が74(%)に留まった。粒径比1/20では計算値19.2(%)に対し、TeO2量が10〜30(%)の範囲で75〜76(%)のＦＦ値が得られた。TeO2量が40(%)ではＦＦ値が74(%)に留まった。粒径比1/30では計算値12.4(%)に対し、TeO2量が0.2〜25(%)の範囲で75〜76(%)のＦＦ値が得られた。TeO2量が35(%)ではＦＦ値が74(%)に留まった。粒径比1/40では計算値9.1(%)に対し、TeO2量が0.1〜20(%)の範囲で75〜76(%)のＦＦ値が得られた。TeO2量が30(%)ではＦＦ値が74(%)に留まった。粒径比1/50では計算値7.2(%)に対し、TeO2量が2〜30(%)の範囲で評価したが、ＦＦ値が72〜74(%)に留まった。 Table 3 shows the evaluation results of SiO 2 —B 2 O 3 —ZnO glass having a specific gravity of 3.4. In this evaluation result, when the particle size ratio was 1/5, the TeO 2 powder amount was evaluated in the range of 90 to 110 (%) with respect to the calculated value of 100.2 (%), but the FF value was 67 to 71 (%). Stayed. In the range of the particle size ratio of 1/10 to 1/40, sufficiently high FF values could be obtained. That is, when the particle size ratio was 1/10, the FF value of 75 to 76 (%) was obtained when the TeO 2 content was in the range of 40 to 60 (%) with respect to the calculated value of 42.1 (%). When the amount of TeO 2 was 1 (%) or 70 (%), the FF value remained at 74 (%). At a particle size ratio of 1/20, an FF value of 75 to 76 (%) was obtained when the TeO 2 content was in the range of 10 to 30 (%) with respect to the calculated value of 19.2 (%). When the amount of TeO 2 was 40 (%), the FF value remained at 74 (%). At a particle size ratio of 1/30, FF values of 75 to 76 (%) were obtained when the TeO 2 content was in the range of 0.2 to 25 (%) with respect to the calculated value of 12.4 (%). When the amount of TeO 2 was 35 (%), the FF value remained at 74 (%). At a particle size ratio of 1/40, an FF value of 75 to 76 (%) was obtained when the TeO 2 content was in the range of 0.1 to 20 (%) with respect to the calculated value of 9.1 (%). When the amount of TeO 2 was 30 (%), the FF value remained at 74 (%). At a particle size ratio of 1/50, the TeO 2 content was evaluated in the range of 2 to 30 (%) with respect to the calculated value of 7.2 (%), but the FF value remained at 72 to 74 (%).
上記の評価結果によれば、ガラス粉末の比重や粒径に拘わらず、TeO2／ガラス粒径比が1/10〜1/40の範囲において、TeO2／ガラス質量比を不規則充填の計算値に対して−12(%)〜＋20(%)程度の範囲で適宜選択することにより、75(%)以上のＦＦ値を得ることができる。±12(%)程度の範囲とすれば、76(%)以上のＦＦ値が得られ、−12(%)〜＋2(%)程度の範囲とすれば、77〜78(%)のＦＦ値が得られる。Te量を計算値に対して著しく少なくすると、ガラス粉末表面への固着状態に著しいムラが生じることから、ガラスへのAg溶解量がばらつき易くなるため、好結果が得られないものと考えられる。また、計算値に対して著しく多くすると、Teによる侵食抑制作用が顕著に現れると共に、複合化されない余剰のTe化合物が多くなって、ガラスとは別にペーストにTe化合物を添加した従来技術と同様な状態となるので、接触抵抗も十分に低くできず、延いては特性が得られなくなるものと考えられる。 According to the above evaluation results, regardless of the specific gravity and particle size of the glass powder, the TeO 2 / glass mass ratio is calculated for irregular filling when the TeO 2 / glass particle size ratio is in the range of 1/10 to 1/40. An FF value of 75 (%) or more can be obtained by appropriately selecting the value within a range of about −12 (%) to +20 (%). If it is in the range of about ± 12 (%), an FF value of 76 (%) or more is obtained, and if it is in the range of about -12 (%) to +2 (%), the FF value of 77 to 78 (%) Is obtained. When the amount of Te is remarkably reduced with respect to the calculated value, remarkable unevenness occurs in the fixed state on the surface of the glass powder, so that the amount of Ag dissolved in the glass tends to vary, and it is considered that good results cannot be obtained. In addition, when the calculated value is significantly increased, the erosion-inhibiting effect by Te appears remarkably, and the excess Te compound that is not compounded increases, which is the same as the conventional technique in which the Te compound is added to the paste separately from glass. Therefore, it is considered that the contact resistance cannot be sufficiently lowered and the characteristics cannot be obtained.
また、粒径比1/5、1/50では良好な結果が得られていないが、粒径比1/5ではガラス粉末の表面に一様にTe化合物を固着しようとすると、ガラスフリットに対してTe化合物量が比較的多くなる。そのため、Te量が過剰となって特性が得られなかったものと考えられる。また、粒径比1/50ではTe量が著しく少なくなるため添加効果が得られなかったものと考えられる。 Also, good results have not been obtained with a particle size ratio of 1/5 and 1/50, but with a particle size ratio of 1/5, trying to fix the Te compound uniformly on the surface of the glass powder, Therefore, the amount of Te compound is relatively large. Therefore, it is considered that the characteristics were not obtained due to an excessive amount of Te. Further, it is considered that the addition effect could not be obtained at a particle size ratio of 1/50 because the amount of Te was remarkably reduced.
また、比重3.4のSiO2-B2O3-ZnO系ガラスで粒径比1/10とした場合において、TeO2量を60(%)としても75(%)のＦＦ値が得られている。ガラス比重および粒径比の影響もあるが、このようにTeO2量は少なくとも60(%)までは許容される。 Further, when the particle size ratio is 1/10 with SiO 2 —B 2 O 3 —ZnO glass having a specific gravity of 3.4, an FF value of 75 (%) is obtained even when the amount of TeO 2 is 60 (%). . Although there is an influence of glass specific gravity and particle size ratio, the amount of TeO 2 is thus allowed up to at least 60 (%).
また、ガラス比重4.8の粒径比1/30、ガラス比重5.3の粒径比1/10に示すように、特性の得られたTeO2量と同量としても、メカノケミカル法によらないガラス粉末とTeO2粉末とを「単に混合」しただけの粉末では、特性が得られない。このような混合粉末では、Teがガラス表面に留まらないことから、ガラスへのAg溶解量の増大に対する寄与が小さいためと考えられる。 In addition, as shown in the particle size ratio 1/30 of glass specific gravity 4.8 and the particle size ratio 1/10 of glass specific gravity 5.3, glass powder not depending on mechanochemical method even if the amount is the same as the amount of TeO 2 obtained characteristics If the powder is simply “mixed” with TeO 2 powder, the characteristics cannot be obtained. In such a mixed powder, it is considered that Te does not stay on the glass surface, so that the contribution to the increase in the amount of Ag dissolved in the glass is small.
以上、本発明を図面を参照して詳細に説明したが、本発明は更に別の態様でも実施でき、その主旨を逸脱しない範囲で種々変更を加え得るものである。 As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.
１０：太陽電池、１２：太陽電池モジュール、１４：封止材、１６：表面ガラス、１８：保護フィルム、２０：シリコン基板、２２：ｎ層、２４：ｐ+層、２６：反射防止膜、２８：受光面電極、３０：裏面電極、３２：受光面、３４：全面電極、３６：帯状電極、３８：半田リボン 10: solar cell, 12: solar cell module, 14: sealing material, 16: surface glass, 18: protective film, 20: silicon substrate, 22: n layer, 24: p + layer, 26: antireflection film, 28 : Light receiving surface electrode, 30: Back electrode, 32: Light receiving surface, 34: Full surface electrode, 36: Strip electrode, 38: Solder ribbon
Claims (3)
メカノケミカル法によってTe化合物粒子を前記ガラスフリットの粒子表面に分散して固着させて複合粒子を得る複合化処理工程と、
前記導電性粉末と、前記複合粒子と、前記ベヒクルと含むペースト原料を混合する混合工程と
を、含むことを特徴とする太陽電池用導電性ペースト組成物の製造方法。 A method for producing a conductive paste composition for a solar cell comprising a conductive powder, a glass frit, and a vehicle,
And decryption process to obtain a composite particle by fixing by dispersing Te compound particles on the particle surfaces of the glass frit by mechanochemical method,
A mixing step of mixing the conductive powder, the composite particles, and the paste raw material containing the vehicle;
The method of manufacturing a solar cell conductive paste composition which comprises.
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