JPWO2018180441A1 - Paste composition for solar cell - Google Patents

Paste composition for solar cell Download PDF

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JPWO2018180441A1
JPWO2018180441A1 JP2019509193A JP2019509193A JPWO2018180441A1 JP WO2018180441 A1 JPWO2018180441 A1 JP WO2018180441A1 JP 2019509193 A JP2019509193 A JP 2019509193A JP 2019509193 A JP2019509193 A JP 2019509193A JP WO2018180441 A1 JPWO2018180441 A1 JP WO2018180441A1
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solar cell
aluminum
silicon
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paste composition
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マルワン ダムリン
マルワン ダムリン
正博 中原
正博 中原
紹太 鈴木
紹太 鈴木
直哉 森下
直哉 森下
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TOYO ALMINIUM KABUSHIKI KAISHA
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Abstract

本発明は、パッシベーション膜の開口部の直径が１００μｍ以下であり、開口部の総面積が結晶系太陽電池セルの面積の０．５〜５％である結晶系太陽電池セルに対して適用した場合に、優れた変換効率が達成できるとともに、焼成後の電極層界面でのボイドの発生を抑制し、更に静的機械荷重試験後の変換効率の低下率を抑制できる太陽電池用ペースト組成物を提供する。本発明は、具体的には、開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対してｐ＋層を形成する用途に用いる、ガラス粉末、有機ビヒクル及び導電性材料を含有する太陽電池用ペースト組成物であって、（１）前記開口部は直径が１００μｍ以下であり、前記開口部の総面積は前記結晶系太陽電池セルの面積の０．５〜５％であり、（２）前記導電性材料は、アルミニウム粉末と、長径が５μｍ以下のシリコンの初晶を有するアルミニウム−シリコン合金粉末とを含有する、ことを特徴とする太陽電池用ペースト組成物を提供する。The present invention is applied to a crystalline solar cell in which the diameter of the opening of the passivation film is 100 μm or less and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell. In addition, the present invention provides a solar cell paste composition that can achieve excellent conversion efficiency, suppress generation of voids at the electrode layer interface after firing, and suppress the rate of decrease in conversion efficiency after static mechanical load test. I do. The present invention specifically relates to a solar cell containing a glass powder, an organic vehicle, and a conductive material, which is used for forming ap + layer for a crystalline solar cell having a passivation film provided with an opening. A paste composition, wherein (1) the opening has a diameter of 100 μm or less, and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell; Provided is a solar cell paste composition, wherein the conductive material contains aluminum powder and aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5 μm or less.

Description

本発明は、太陽電池用ペースト組成物に関し、特にレーザー照射などを用いて開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対してｐ＋層を形成することを目的とした太陽電池用ペースト組成物に関する。より具体的には、開口部の直径が１００μｍ以下であり、開口部の総面積が結晶系太陽電池セルの面積の０．５〜５％である結晶系太陽電池セルに対して適用する太陽電池用ペースト組成物に関する。The present invention relates to a solar cell paste composition, and more particularly to a solar cell paste composition for forming a p + layer on a crystalline solar cell having a passivation film provided with an opening by using laser irradiation or the like. The present invention relates to a paste composition. More specifically, a solar cell applied to a crystalline solar cell in which the diameter of the opening is 100 μm or less and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell The present invention relates to a paste composition.

近年、結晶系太陽電池セルの変換効率（発電効率）、信頼性等を向上させることを目的として、種々の研究開発が行われている。その一つとして、セル裏面に窒化ケイ素、酸化ケイ素、酸化アルミニウム等からなるパッシベーション膜を有するＰＥＲＣ（Passivated emitter and rear cell）型高変換効率セルが注目されている。   In recent years, various research and development have been performed for the purpose of improving the conversion efficiency (power generation efficiency), reliability, and the like of crystalline solar cells. As one of them, a PERC (Passivated emitter and rear cell) type high conversion efficiency cell having a passivation film made of silicon nitride, silicon oxide, aluminum oxide, or the like on the back surface of the cell has attracted attention.

ＰＥＲＣ型高変換効率セルは、例えばアルミニウムを主成分とする電極層を備えた構造を有する。この電極層（特に裏面電極層）は、例えばアルミニウムを主体とするペースト組成物を、パッシベーション膜の開口部を被覆するようにパターン形状に塗布し、必要に応じて乾燥後、焼成することにより形成される。例えば、特許文献１には、アルミニウム粉末と、アルミニウム−シリコン合金粉末と、シリコン粉末と、ガラス粉末と、有機ビヒクルとを含むペースト組成物が開示されている。そして、電極層の構成を適切に設計することで、ＰＥＲＣ型高変換効率セルの変換効率を高められることが知られている。   The PERC type high conversion efficiency cell has a structure including an electrode layer containing, for example, aluminum as a main component. The electrode layer (particularly, the back electrode layer) is formed by applying a paste composition mainly composed of, for example, aluminum in a pattern shape so as to cover the openings of the passivation film, and drying and firing as necessary. Is done. For example, Patent Document 1 discloses a paste composition including aluminum powder, aluminum-silicon alloy powder, silicon powder, glass powder, and an organic vehicle. It is known that the conversion efficiency of a PERC type high conversion efficiency cell can be increased by appropriately designing the configuration of the electrode layer.

また、近年ではＰＥＲＣ型高変換効率セルの変換効率を更に高める方法として、パッシベーション膜の開口部の面積を小さくし、パッシベーション膜の面積を増やすことにより、電子とホールとの再結合を抑制することが検討されてきている。   In recent years, as a method of further increasing the conversion efficiency of a PERC type high conversion efficiency cell, the recombination between electrons and holes is suppressed by reducing the area of the opening of the passivation film and increasing the area of the passivation film. Are being considered.

特開２０１３−１４３４９９号公報JP 2013-143499 A

しかしながら、従来のペースト組成物を用いて電極層を形成した場合に、特に開口部の直径が１００μｍ以下であり、開口部の総面積が結晶系太陽電池セルの面積の０．５〜５％である結晶系太陽電池セルに対しては変換効率の向上に未だ改善の余地がある。また、電極層界面にボイドと称される空隙が生じる場合がある他、静的機械荷重試験後の変換効率の低下率が３％以上になるという問題がある。電極層界面にボイドが生じた場合には、抵抗を増加させるとともに結晶系太陽電池セルの長期信頼性の低下の原因となり得る。   However, when the electrode layer is formed using the conventional paste composition, particularly, the diameter of the opening is 100 μm or less, and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell. For some crystalline solar cells, there is still room for improvement in the conversion efficiency. In addition, a void called a void may be formed at the interface of the electrode layer, and there is a problem that the conversion efficiency after the static mechanical load test decreases by 3% or more. When a void is generated at the interface of the electrode layer, the resistance may be increased and the long-term reliability of the crystalline solar cell may be reduced.

本発明は、上記に鑑みてなされたものであり、パッシベーション膜の開口部の直径が１００μｍ以下であり、開口部の総面積が結晶系太陽電池セルの面積の０．５〜５％である結晶系太陽電池セルに対して適用した場合でも優れた変換効率が達成できるとともに、焼成後の電極層界面でのボイドの発生を抑制し、更に静的機械荷重試験後の変換効率の低下率を抑制できる太陽電池用ペースト組成物を提供することを目的とする。また、当該太陽電池用ペースト組成物を用いた裏面電極の形成方法を提供することも目的とする。   The present invention has been made in view of the above, and has a crystal in which the diameter of an opening of a passivation film is 100 μm or less and the total area of the opening is 0.5 to 5% of the area of a crystalline solar cell. Excellent conversion efficiency can be achieved even when applied to solar cells, and the generation of voids at the electrode layer interface after firing is suppressed, and the rate of decrease in conversion efficiency after static mechanical load tests is suppressed. It is an object of the present invention to provide a solar cell paste composition that can be used. Another object of the present invention is to provide a method for forming a back electrode using the paste composition for a solar cell.

本発明者は、上記目的を達成すべく鋭意研究を重ねた結果、特定の導電性材料を含むペースト組成物が上記目的を達成できることを見出し、本発明を完成するに至った。   The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a paste composition containing a specific conductive material can achieve the above object, and have completed the present invention.

即ち、本発明は、下記の太陽電池用ペースト組成物に関する。
１．開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対してｐ＋層を形成する用途に用いる、ガラス粉末、有機ビヒクル及び導電性材料を含有する太陽電池用ペースト組成物であって、
（１）前記開口部は直径が１００μｍ以下であり、前記開口部の総面積は前記結晶系太陽電池セルの面積の０．５〜５％であり、
（２）前記導電性材料は、アルミニウム粉末と、長径が５μｍ以下のシリコンの初晶を有するアルミニウム−シリコン合金粉末とを含有する、
ことを特徴とする太陽電池用ペースト組成物。
２．前記アルミニウム粉末１００質量部に対して、前記アルミニウム−シリコン合金粉末４０〜７００質量部、前記ガラス粉末０．１〜１５質量部、及び前記有機ビヒクル２０〜４５質量部を含有する、上記項１に記載の太陽電池用ペースト組成物。
３．前記開口部の直径が２０〜１００μｍである、上記項１又は２に記載の太陽電池用ペースト組成物。
４．開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対して、前記開口部を被覆するように、ガラス粉末、有機ビヒクル及び導電性材料を含有する太陽電池用ペースト組成物を塗布することにより塗膜を形成する工程１、並びに、
前記塗膜を７００〜９００℃で焼成する工程２、
を有する、結晶系太陽電池セルの裏面電極の形成方法であって、
（１）前記開口部は直径が１００μｍ以下であり、前記開口部の総面積は前記結晶系太陽電池セルの面積の０．５〜５％であり、
（２）前記導電性材料は、アルミニウム粉末と、長径が５μｍ以下のシリコンの初晶を有するアルミニウム−シリコン合金粉末とを含有する、
ことを特徴とする裏面電極の形成方法。
５．前記アルミニウム粉末１００質量部に対して、前記アルミニウム−シリコン合金粉末４０〜７００質量部、前記ガラス粉末０．１〜１５質量部、及び前記有機ビヒクル２０〜４５質量部を含有する、上記項４に記載の裏面電極の形成方法。
６．前記開口部の直径が２０〜１００μｍである、上記項４又は５に記載の裏面電極の形成方法。That is, the present invention relates to the following solar cell paste composition.
1. A solar cell paste composition containing a glass powder, an organic vehicle, and a conductive material, which is used for forming ap + layer for a crystalline solar cell having a passivation film provided with an opening,
(1) The opening has a diameter of 100 μm or less, and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell,
(2) The conductive material contains an aluminum powder and an aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5 μm or less,
A paste composition for a solar cell, comprising:
2. The above-mentioned item 1, which comprises 40 to 700 parts by mass of the aluminum-silicon alloy powder, 0.1 to 15 parts by mass of the glass powder, and 20 to 45 parts by mass of the organic vehicle with respect to 100 parts by mass of the aluminum powder. The paste composition for a solar cell according to the above.
3. Item 3. The paste composition for a solar cell according to Item 1 or 2, wherein the diameter of the opening is 20 to 100 μm.
4. By applying a solar cell paste composition containing a glass powder, an organic vehicle and a conductive material to a crystalline solar cell having a passivation film having an opening so as to cover the opening. Step 1 of forming a coating film, and
Baking the coating film at 700 to 900 ° C.,
A method for forming a back electrode of a crystalline solar cell, comprising:
(1) The opening has a diameter of 100 μm or less, and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell,
(2) The conductive material contains an aluminum powder and an aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5 μm or less,
A method for forming a back electrode, comprising:
5. The above item 4, which contains 40 to 700 parts by mass of the aluminum-silicon alloy powder, 0.1 to 15 parts by mass of the glass powder, and 20 to 45 parts by mass of the organic vehicle with respect to 100 parts by mass of the aluminum powder. The method for forming the back electrode described in the above.
6. Item 6. The method for forming a back electrode according to Item 4 or 5, wherein the diameter of the opening is 20 to 100 μm.

本発明の太陽電池用ペースト組成物は、結晶系太陽電池セル（特にＰＥＲＣ型高変換効率セル）の中でもパッシベーション膜の開口部の直径が１００μｍ以下であり、開口部の総面積が結晶系太陽電池セルの面積の０．５〜５％である結晶系太陽電池セルに対して適用した場合でも優れた変換効率が達成できるとともに、焼成後の電極層界面でのボイドの発生を抑制し、更に静的機械荷重試験後の変換効率の低下率を抑制できる。   The paste composition for a solar cell of the present invention has a diameter of an opening of a passivation film of 100 μm or less among crystalline solar cells (particularly, a PERC type high conversion efficiency cell), and the total area of the opening is a crystalline solar cell. Even when applied to a crystalline solar cell having a cell area of 0.5 to 5%, excellent conversion efficiency can be achieved, the generation of voids at the interface of the electrode layer after firing is suppressed, and the static electricity is reduced. The rate of decrease in conversion efficiency after a dynamic mechanical load test can be suppressed.

ＰＥＲＣ型太陽電池セルの断面構造の一例を示す模式図であり、（ａ）はその実施形態の一例を示し、（ｂ）はその実施形態の他例を示す。It is a schematic diagram which shows an example of the cross-section of a PERC type solar cell, (a) shows an example of the embodiment, (b) shows another example of the embodiment. 実施例及び比較例において作製された電極構造の断面の模式図である。It is a schematic diagram of a section of an electrode structure produced in an example and a comparative example. アルミニウム粉末、及びアルミニウム−シリコン合金粉末の表面を電子顕微鏡により観察した観察像を示す図である。詳細には、（ａ）はシリコン含有量が２０原子％のアルミニウム−シリコン合金粉末、（ｂ）はアルミニウム粉末、（ｃ）はシリコン含有量が１５原子％のアルミニウム−シリコン合金粉末の観察像である。It is a figure which shows the observation image which observed the surface of aluminum powder and aluminum-silicon alloy powder with the electron microscope. Specifically, (a) is an observation image of an aluminum-silicon alloy powder having a silicon content of 20 atom%, (b) is an aluminum powder, and (c) is an observation image of an aluminum-silicon alloy powder having a silicon content of 15 atom%. is there.

以下、本発明の太陽電池用ペースト組成物について詳細に説明する。なお、本明細書において、「〜」で示される範囲は、特に説明する場合を除き「以上、以下」を意味する。   Hereinafter, the solar cell paste composition of the present invention will be described in detail. In this specification, the range indicated by “to” means “more or less” unless otherwise specified.

本発明の太陽電池用ペースト組成物は、例えば、結晶系太陽電池セルの電極を形成するために使用することができる。結晶系太陽電池セルとしては特に限定されないが、例えば、ＰＥＲＣ（Passivated emitter and rear cell）型高変換効率セル（以下、「ＰＥＲＣ型太陽電池セル」という。）が挙げられる。本発明の太陽電池用ペースト組成物は、例えば、ＰＥＲＣ型太陽電池セルの裏面電極を形成するために使用することができる。以下、本発明のペースト組成物を、単に「ペースト組成物」とも記載する。   The solar cell paste composition of the present invention can be used, for example, for forming an electrode of a crystalline solar cell. The crystalline solar cell is not particularly limited, and examples thereof include a PERC (Passivated emitter and rear cell) type high conversion efficiency cell (hereinafter, referred to as a “PERC solar cell”). The solar cell paste composition of the present invention can be used, for example, to form a back electrode of a PERC solar cell. Hereinafter, the paste composition of the present invention is also simply referred to as “paste composition”.

最初に、ＰＥＲＣ型太陽電池セルの構造の一例を説明する。   First, an example of the structure of the PERC solar cell will be described.

１．ＰＥＲＣ型太陽電池セル
図１（ａ）、（ｂ）は、ＰＥＲＣ型太陽電池セルの一般的な断面構造の模式図である。ＰＥＲＣ型太陽電池セルは、シリコン半導体基板１、ｎ型不純物層２、反射防止膜（パッシベーション膜）３、グリッド電極４、電極層（裏面電極層）５、合金層６、ｐ＋層７を構成要素として備えることができる。 1. PERC solar cell FIGS. 1A and 1B are schematic views of a general sectional structure of a PERC solar cell. The PERC solar cell includes a silicon semiconductor substrate 1, an n-type impurity layer 2, an antireflection film (passivation film) 3, a grid electrode 4, an electrode layer (backside electrode layer) 5, an alloy layer 6, and a p + layer 7. Can be provided as an element.

シリコン半導体基板１は特に限定されず、例えば、厚みが１８０〜２５０μｍのｐ型シリコン基板が用いられる。   The silicon semiconductor substrate 1 is not particularly limited, and for example, a p-type silicon substrate having a thickness of 180 to 250 μm is used.

ｎ型不純物層２は、シリコン半導体基板１の受光面側に設けられる。ｎ型不純物層２の厚みは、例えば、０．３〜０．６μｍである。   N-type impurity layer 2 is provided on the light receiving surface side of silicon semiconductor substrate 1. The thickness of the n-type impurity layer 2 is, for example, 0.3 to 0.6 μm.

反射防止膜３及びグリッド電極４は、ｎ型不純物層２の表面に設けられる。反射防止膜３は、例えば、窒化シリコン膜で形成されパッシベーション膜とも称される。反射防止膜３は、いわゆるパッシベーション膜として作用することで、シリコン半導体基板１の表面での電子の再結合を抑制でき、結果として、発生したキャリアの再結合率を減らすことを可能にする。これにより、ＰＥＲＣ型太陽電池セルの変換効率が高められる。   The antireflection film 3 and the grid electrode 4 are provided on the surface of the n-type impurity layer 2. The antireflection film 3 is formed of, for example, a silicon nitride film and is also called a passivation film. By acting as a so-called passivation film, the antireflection film 3 can suppress the recombination of electrons on the surface of the silicon semiconductor substrate 1, and as a result, can reduce the recombination rate of generated carriers. Thereby, the conversion efficiency of the PERC solar cell is increased.

反射防止膜（パッシベーション膜）３は、シリコン半導体基板１の裏面側、つまり、前記受光面と逆側の面にも設けられる。また、この裏面側の反射防止膜（パッシベーション膜）３を貫通し、かつ、シリコン半導体基板１の裏面の一部を削るように形成されたコンタクト孔（本発明での開口部）が、シリコン半導体基板１の裏面側に形成されている。   The antireflection film (passivation film) 3 is also provided on the back surface side of the silicon semiconductor substrate 1, that is, on the surface opposite to the light receiving surface. Further, a contact hole (opening in the present invention) penetrating through the anti-reflection film (passivation film) 3 on the rear surface side and formed so as to cut a part of the rear surface of the silicon semiconductor substrate 1 is formed by a silicon semiconductor. It is formed on the back side of the substrate 1.

電極層５は、前記コンタクト孔を通じてシリコン半導体基板１に接触するように形成されている。電極層５は、本発明のペースト組成物によって形成される部材であり、所定のパターン形状に形成される。図１（ａ）の形態のように、電極層５は、ＰＥＲＣ型太陽電池セルの裏面全体を覆うように形成されていてもよいし、又は図１（ｂ）の形態のようにコンタクト孔及びその近傍を覆うように形成されていてもよい。電極層５の主成分はアルミニウムであるので、電極層５はアルミニウム電極層である。   The electrode layer 5 is formed so as to contact the silicon semiconductor substrate 1 through the contact hole. The electrode layer 5 is a member formed by the paste composition of the present invention, and is formed in a predetermined pattern shape. 1A, the electrode layer 5 may be formed so as to cover the entire back surface of the PERC solar cell, or the contact hole and the contact hole may be formed as shown in FIG. 1B. It may be formed so as to cover the vicinity thereof. Since the main component of the electrode layer 5 is aluminum, the electrode layer 5 is an aluminum electrode layer.

電極層５は、例えば、ペースト組成物を所定のパターン形状に塗布し、焼成することで形成される。塗布方法は特に限定されず、例えば、スクリーン印刷等の公知の方法が挙げられる。ペースト組成物を塗布し、必要に応じて乾燥させた後、例えば、アルミニウムの融点（約６６０℃）を超える温度にて短時間焼成することで、電極層５が形成される。   The electrode layer 5 is formed, for example, by applying a paste composition in a predetermined pattern shape and firing the paste composition. The coating method is not particularly limited, and examples thereof include known methods such as screen printing. After the paste composition is applied and dried if necessary, the electrode layer 5 is formed by baking for a short time at a temperature exceeding the melting point of aluminum (about 660 ° C.), for example.

本発明では、焼成温度はアルミニウムの融点（約６６０℃）を超える温度であればよいが、７００〜９００℃程度が好ましく、７８０〜９００℃程度がより好ましい。焼成時間は所望の電極層５が形成される範囲で焼成温度に応じて適宜設定することができる。   In the present invention, the firing temperature may be a temperature higher than the melting point of aluminum (about 660 ° C.), but is preferably about 700 to 900 ° C., and more preferably about 780 to 900 ° C. The firing time can be appropriately set according to the firing temperature within a range where a desired electrode layer 5 is formed.

このように焼成すると、ペースト組成物に含まれるアルミニウムが、シリコン半導体基板１の内部に拡散する。これにより、電極層５とシリコン半導体基板１との間に、アルミニウム−シリコン（Ａｌ−Ｓｉ）合金層（合金層６）が形成され、これと同時に、アルミニウム原子の拡散によって、不純物層としてのｐ＋層７が形成される。When fired in this manner, aluminum contained in the paste composition diffuses into silicon semiconductor substrate 1. As a result, an aluminum-silicon (Al-Si) alloy layer (alloy layer 6) is formed between the electrode layer 5 and the silicon semiconductor substrate 1, and at the same time, the diffusion of aluminum atoms causes p as an impurity layer. The + layer 7 is formed.

ｐ＋層７は、電子の再結合を防止し、生成キャリアの収集効率を向上させる効果、いわゆるＢＳＦ（Back Surface Field）効果をもたらすことができる。The p + layer 7 has an effect of preventing recombination of electrons and improving collection efficiency of generated carriers, that is, a so-called BSF (Back Surface Field) effect.

前記電極層５と合金層６とで形成される電極が、図１に示す裏面電極８である。従って、裏面電極８は、ペースト組成物を用いて形成され、例えば、裏面側の反射防止膜（パッシベーション膜）３に設けたコンタクト孔９（開口部）を被覆するように塗工し、必要に応じて乾燥後、焼成することによって裏面電極８を形成できる。   The electrode formed by the electrode layer 5 and the alloy layer 6 is the back electrode 8 shown in FIG. Therefore, the back surface electrode 8 is formed using a paste composition, and is coated, for example, so as to cover the contact hole 9 (opening) provided in the antireflection film (passivation film) 3 on the back surface side. The back electrode 8 can be formed by drying and baking accordingly.

ここで、本発明のペースト組成物を用いて裏面電極８を形成することにより、パッシベーション膜の開口部の直径が１００μｍ以下（好ましくは２０〜１００μｍ）であり、開口部の総面積が結晶系太陽電池セルの面積の０．５〜５％（特に２〜４％、更には２．５〜３．５％）である結晶系太陽電池セルに対して適用した場合でも優れた変換効率が達成できるとともに、焼成後の電極層界面でのボイドの発生を抑制し、更に静的機械荷重試験後の変換効率の低下率を抑制できる。   Here, by forming the back electrode 8 using the paste composition of the present invention, the diameter of the opening of the passivation film is 100 μm or less (preferably 20 to 100 μm), and the total area of the opening is Excellent conversion efficiency can be achieved even when applied to a crystalline solar cell having a battery cell area of 0.5 to 5% (particularly 2 to 4%, furthermore 2.5 to 3.5%). At the same time, generation of voids at the interface of the electrode layer after firing can be suppressed, and the rate of decrease in conversion efficiency after the static mechanical load test can be suppressed.

２．ペースト組成物
本発明のペースト組成物は、開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対してｐ＋層を形成する用途に用いる、ガラス粉末、有機ビヒクル及び導電性材料を含有する太陽電池用ペースト組成物であって、
（１）前記開口部は直径が１００μｍ以下であり、前記開口部の総面積は前記結晶系太陽電池セルの面積の０．５〜５％であり、
（２）前記導電性材料は、アルミニウム粉末と、長径が５μｍ以下のシリコンの初晶を有するアルミニウム−シリコン合金粉末とを含有する、
ことを特徴とする。 2. Paste composition The paste composition of the present invention contains glass powder, an organic vehicle, and a conductive material used for forming ap + layer for a crystalline solar cell having a passivation film provided with an opening. A paste composition for a solar cell,
(1) The opening has a diameter of 100 μm or less, and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell,
(2) The conductive material contains an aluminum powder and an aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5 μm or less,
It is characterized by the following.

前述したように、ペースト組成物を使用することで、ＰＥＲＣ型太陽電池セル等の太陽電池セルの裏面電極を形成することができる。つまり、本発明のペースト組成物は、シリコン基板上に形成されたパッシベーション膜に設けた開口部（コンタクト孔）を通じてシリコン基板に電気的に接触する太陽電池用裏面電極を形成するために用いることができる。そして、本発明のペースト組成物によれば、結晶系太陽電池セル（特にＰＥＲＣ型太陽電池セル）の中でもパッシベーション膜の開口部の直径が１００μｍ以下であり、開口部の総面積が結晶系太陽電池セルの面積の０．５〜５％である結晶系太陽電池セルに対して適用した場合でも優れた変換効率が達成できるとともに、焼成後の電極層界面でのボイドの発生を抑制し、更に静的機械荷重試験後の変換効率の低下率を抑制できる。   As described above, the back electrode of a solar cell such as a PERC solar cell can be formed by using the paste composition. That is, the paste composition of the present invention can be used to form a back electrode for a solar cell that is in electrical contact with the silicon substrate through an opening (contact hole) provided in the passivation film formed on the silicon substrate. it can. According to the paste composition of the present invention, the diameter of the opening of the passivation film is 100 μm or less, and the total area of the opening is smaller than that of crystalline solar cells (especially, PERC type solar cells). Even when applied to a crystalline solar cell having a cell area of 0.5 to 5%, excellent conversion efficiency can be achieved, the generation of voids at the interface of the electrode layer after firing is suppressed, and the static electricity is reduced. The rate of decrease in conversion efficiency after a dynamic mechanical load test can be suppressed.

ペースト組成物は、ガラス粉末、有機ビヒクル及び導電性材料（金属粒子）を構成成分として含む。そして、ペースト組成物が導電性材料（金属粒子）を含むことで、ペースト組成物の塗膜が焼成されて形成される焼結体は、シリコン基板と電気的に接続する導電性が発揮される。
（導電性材料）
本発明において、導電性材料は、アルミニウム粉末と、長径が５μｍ以下のシリコンの初晶を有するアルミニウム−シリコン合金粉末とを含有する。The paste composition contains glass powder, an organic vehicle, and a conductive material (metal particles) as constituent components. Since the paste composition contains a conductive material (metal particles), the sintered body formed by firing the coating film of the paste composition exhibits conductivity to be electrically connected to the silicon substrate. .
(Conductive material)
In the present invention, the conductive material contains aluminum powder and aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5 μm or less.

上記アルミニウム粉末は合金が形成されていないアルミニウムをいうが、不可避不純物及び原料由来の微量の添加元素の存在は排除しない。   The aluminum powder refers to aluminum in which no alloy is formed, but does not exclude the presence of inevitable impurities and trace amounts of additional elements derived from raw materials.

本発明で用いるアルミニウム−シリコン合金粉末は、アルミニウムとシリコンとの合金粉末を示すが、アルミニウム及びシリコン中の不可避不純物及び原料由来の微量の添加元素の存在は排除しない。本発明では、当該アルミニウム−シリコン合金におけるシリコン含有量は１２〜３０原子％が好ましく、１７〜２５原子％がより好ましい。このようなアルミニウム−シリコン合金粉末を導電性材料に含有することにより、ペースト組成物の塗膜を焼成する際にペースト組成物中のアルミニウムとシリコン基板中のシリコンとの過剰な反応を抑制し、電極層界面（詳細には電極層とシリコン基板との界面）でのボイドの発生を抑制することができる。   The aluminum-silicon alloy powder used in the present invention refers to an alloy powder of aluminum and silicon, but does not exclude the presence of unavoidable impurities in aluminum and silicon and trace amounts of additional elements derived from raw materials. In the present invention, the silicon content in the aluminum-silicon alloy is preferably from 12 to 30 at%, more preferably from 17 to 25 at%. By containing such an aluminum-silicon alloy powder in a conductive material, an excessive reaction between aluminum in the paste composition and silicon in the silicon substrate is suppressed when firing the coating film of the paste composition, The generation of voids at the electrode layer interface (specifically, the interface between the electrode layer and the silicon substrate) can be suppressed.

本発明で用いるアルミニウム−シリコン合金粉末は、長径が５μｍ以下（即ち、０μｍ超過５μｍ以下）のシリコンの初晶を有することを特徴とする。このようなアルミニウム−シリコン合金粉末を導電性材料に含有することにより、電極層の抵抗を低くし、優れた変換効率を達成できるとともに、静的機械荷重試験後の変換効率の低下率を抑制することができる。初晶の長径は５μｍ以下であればよいが、その中でも１〜５μｍが好ましく、２〜５μｍがより好ましい。   The aluminum-silicon alloy powder used in the present invention has a primary crystal of silicon having a major axis of 5 μm or less (that is, more than 0 μm and 5 μm or less). By containing such an aluminum-silicon alloy powder in a conductive material, the resistance of the electrode layer can be reduced, excellent conversion efficiency can be achieved, and the rate of decrease in conversion efficiency after a static mechanical load test is suppressed. be able to. The major axis of the primary crystal may be 5 μm or less, and preferably 1 to 5 μm, more preferably 2 to 5 μm.

アルミニウム−シリコン合金粉末の初晶の有無及び初晶の形状は、アルミニウム−シリコン合金粉末の断面を光学顕微鏡により観察することにより特定することができる。   The presence or absence and the shape of the primary crystal of the aluminum-silicon alloy powder can be specified by observing the cross section of the aluminum-silicon alloy powder with an optical microscope.

アルミニウム粉末、及びアルミニウム−シリコン合金粉末の一例の光学顕微鏡による観察像が図３に示されている。（ａ）で示されるシリコン含有量が２０原子％のアルミニウム−シリコン合金粉末の断面の観察像にはシリコンの初晶が不定形の灰色点として確認できる。これに対して、（ｂ）で示されるアルミニウム粉末（シリコンは含まない）及び（ｃ）で示されるシリコン含有量が１５原子％のアルミニウム−シリコン合金粉末の断面の観察像にはシリコンの初晶は確認できない。   FIG. 3 shows an image observed by an optical microscope of an example of the aluminum powder and the aluminum-silicon alloy powder. In the observed image of the cross section of the aluminum-silicon alloy powder having a silicon content of 20 atomic% shown in (a), the primary crystal of silicon can be confirmed as an irregular gray point. On the other hand, the observation images of the cross sections of the aluminum powder (not including silicon) shown in (b) and the aluminum-silicon alloy powder having a silicon content of 15 atom% shown in (c) show primary silicon crystals. Can not be confirmed.

長径が５μｍ以下の初晶を有するアルミニウム−シリコン合金粉末を得る方法としては限定的ではないが、例えば、シリコン含有量が１２原子％以上、好ましくは１２〜３０原子％のアルミニウム−シリコン合金の溶湯に０．０５原子％以上のリン（Ｐ）を添加してアトマイズする方法、又は当該溶湯を１０３Ｋ／ｓ以上の速度で急冷しながらアトマイズする方法が挙げられる。急冷法であれば、初晶の長径を５μｍ以下とするために急冷速度を１０３Ｋ／ｓ以上としてアトマイズすることが好ましい。その他、例えば、アルミニウム−シリコン合金粉末をヘリウム（Ｈｅ）、アルゴン（Ａｒ）等の不活性ガスでアトマイズする方法も挙げられる。   A method for obtaining an aluminum-silicon alloy powder having a primary crystal having a major axis of 5 μm or less is not limited. For example, a molten aluminum-silicon alloy having a silicon content of 12 atom% or more, preferably 12 to 30 atom%. And atomizing by adding 0.05 atomic% or more of phosphorus (P) to the alloy, or atomizing the molten metal while rapidly cooling the molten metal at a rate of 103 K / s or more. In the case of the quenching method, it is preferable to atomize the quenching speed at 103 K / s or more in order to make the major diameter of the primary crystal 5 μm or less. In addition, for example, a method of atomizing an aluminum-silicon alloy powder with an inert gas such as helium (He) or argon (Ar) may be used.

アルミニウム粉末に対するアルミニウム−シリコン合金粉末の含有量は限定されないが、アルミニウム粉末１００質量部に対してアルミニウム−シリコン合金粉末の含有量は４０〜７００質量部が好ましく、４０〜２５０質量部がより好ましい。   Although the content of the aluminum-silicon alloy powder with respect to the aluminum powder is not limited, the content of the aluminum-silicon alloy powder is preferably 40 to 700 parts by mass, more preferably 40 to 250 parts by mass, per 100 parts by mass of the aluminum powder.

導電性材料（アルミニウム粉末、及びアルミニウム−シリコン合金粉末）の形状は特に限定されず、例えば、球状、楕円状、不定形状、鱗片状、繊維状等のいずれでもよい。導電性材料の形状が球状であれば、ペースト組成物により形成される電極層５において、導電性材料の充填性が増大して電気抵抗を効果的に低下させることができる。   The shape of the conductive material (aluminum powder and aluminum-silicon alloy powder) is not particularly limited, and may be, for example, any of a sphere, an ellipse, an irregular shape, a scale, and a fiber. If the shape of the conductive material is spherical, the filling property of the conductive material in the electrode layer 5 formed of the paste composition is increased, and the electric resistance can be effectively reduced.

また、導電性材料の形状が球状である場合、ペースト組成物により形成される電極層５において、シリコン半導体基板１と導電性材料との接点が増えるので、良好なＢＳＦ層を形成しやすい。球状の場合には、レーザー回折法により測定される平均粒子径が１〜１０μｍの範囲であることが好ましい。   In addition, when the shape of the conductive material is spherical, the number of contacts between the silicon semiconductor substrate 1 and the conductive material increases in the electrode layer 5 formed of the paste composition, so that a good BSF layer is easily formed. In the case of a spherical shape, the average particle size measured by a laser diffraction method is preferably in the range of 1 to 10 μm.

なお、本発明の効果が阻害されない範囲で、必要に応じてアルミニウム粉末、及びアルミニウム−シリコン合金粉末以外の他の金属粒子を含有することは許容される。これらの導電性材料は、いずれもガスアトマイズ法などの公知の方法で製造することができる。
（ガラス粉末）
ガラス粉末は、導電性材料とシリコンとの反応、及び、導電性材料自身の焼結を助ける作用があるとされている。In addition, as long as the effects of the present invention are not impaired, it is permissible to include metal particles other than aluminum powder and aluminum-silicon alloy powder as necessary. Any of these conductive materials can be manufactured by a known method such as a gas atomizing method.
(Glass powder)
The glass powder is said to have a function of assisting the reaction between the conductive material and silicon and sintering of the conductive material itself.

ガラス粉末としては特に限定されず、例えば、太陽電池セルの電極層を形成するために使用されているペースト組成物に含まれる公知のガラス成分とすることができる。ガラス粉末の具体例としては、鉛（Ｐｂ）、ビスマス（Ｂｉ）、バナジウム（Ｖ）、ホウ素（Ｂ）、シリコン（Ｓｉ）、スズ（Ｓｎ）、リン（Ｐ）及び亜鉛（Ｚｎ）からなる群から選択される少なくとも一種が挙げられる。また、鉛を含むガラス粉末、又は、ビスマス系、バナジウム系、スズ−リン系、ホウケイ酸亜鉛系、アルカリホウケイ酸系等の無鉛のガラス粉末を用いることができる。特に人体への影響を考慮すると、無鉛のガラス粉末を用いることが望ましい。   The glass powder is not particularly limited, and may be, for example, a known glass component contained in a paste composition used for forming an electrode layer of a solar cell. Specific examples of the glass powder include a group consisting of lead (Pb), bismuth (Bi), vanadium (V), boron (B), silicon (Si), tin (Sn), phosphorus (P), and zinc (Zn). At least one selected from the group consisting of: Further, a glass powder containing lead, or a lead-free glass powder such as a bismuth-based, vanadium-based, tin-phosphorus-based, zinc borosilicate-based, or alkali borosilicate-based powder can be used. In particular, in consideration of the effect on the human body, it is desirable to use lead-free glass powder.

具体的にガラス粉末は、Ｂ２Ｏ３、Ｂｉ２Ｏ３、ＺｎＯ、ＳｉＯ２、Ａｌ２Ｏ３、ＢａＯ、ＣａＯ、ＳｒＯ、Ｖ２Ｏ５、Ｓｂ２Ｏ３、ＷＯ３、Ｐ２Ｏ５及びＴｅＯ２からなる群より選ばれる少なくとも１種の成分を含むことができる。例えば、ガラス粉末において、Ｂ２Ｏ３成分とＢｉ２Ｏ３成分とのモル比（Ｂ２Ｏ３／Ｂｉ２Ｏ３）が０．８以上４．０以下であるガラスフリットと、Ｖ２Ｏ５成分とＢａＯ成分とのモル比（Ｖ２Ｏ５／ＢａＯ）が１．０以上２．５以下であるガラスフリットとを組み合わせてもよい。Specifically glass powder, B 2 O 3, Bi 2 O 3, ZnO, SiO 2, Al 2 O 3, BaO, CaO, SrO, V 2 O 5, Sb 2 O 3, WO 3, P 2 O 5 And at least one component selected from the group consisting of and TeO 2 . For example, the glass powder, the glass frit B 2 O 3 molar ratio of the component and Bi 2 O 3 component (B 2 O 3 / Bi 2 O 3) is 0.8 to 4.0, V 2 O 5 molar ratio of the component and the BaO component (V 2 O 5 / BaO) may be combined with the glass frit is 1.0 to 2.5.

ガラス粉末の軟化点は、例えば、７５０℃以下とすることができる。ガラス粉末に含まれる粒子の平均粒子径は、例えば、１〜３μｍとすることができる。   The softening point of the glass powder can be, for example, 750 ° C. or lower. The average particle diameter of the particles contained in the glass powder can be, for example, 1 to 3 μm.

ペースト組成物中に含まれるガラス粉末の含有量は、例えば、導電性材料１００質量部に対して、０．５〜４０質量部であることが好ましく、特にアルミニウム粉末１００質量部に対して、０．１〜１５質量部であることが好ましい。この場合、シリコン半導体基板１および反射防止膜３（パッシベーション膜）との密着性が良好となり、また、電気抵抗も増大しにくい。
（有機ビヒクル）
有機ビヒクルとしては、溶剤に、必要に応じて各種添加剤及び樹脂を溶解した材料を使用できる。又は、溶剤を含まず、樹脂そのものを有機ビヒクルとして使用してもよい。The content of the glass powder contained in the paste composition is preferably, for example, 0.5 to 40 parts by mass with respect to 100 parts by mass of the conductive material, and in particular, 0 to 100 parts by mass of the aluminum powder. It is preferably from 1 to 15 parts by mass. In this case, the adhesion between the silicon semiconductor substrate 1 and the antireflection film 3 (passivation film) is improved, and the electric resistance is hardly increased.
(Organic vehicle)
As the organic vehicle, a material in which various additives and a resin are dissolved in a solvent as necessary can be used. Alternatively, the resin itself may be used as an organic vehicle without containing a solvent.

溶剤は、公知の種類が使用可能であり、具体的には、ジエチレングリコールモノブチルエーテル、ジエチレングリコールモノブチルエーテルアセテート、ジプロピレングリコールモノメチルエーテル等が挙げられる。   Known types of solvents can be used, and specific examples thereof include diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and dipropylene glycol monomethyl ether.

各種添加剤としては、例えば、酸化防止剤、腐食抑制剤、消泡剤、増粘剤、タックファイヤー、カップリング剤、静電付与剤、重合禁止剤、チキソトロピー剤、沈降防止剤等を使用することができる。具体的には、例えば、ポリエチレングリコールエステル化合物、ポリエチレングリコールエーテル化合物、ポリオキシエチレンソルビタンエステル化合物、ソルビタンアルキルエステル化合物、脂肪族多価カルボン酸化合物、燐酸エステル化合物、ポリエステル酸のアマイドアミン塩、酸化ポリエチレン系化合物、脂肪酸アマイドワックス等を使用することができる。   As various additives, for example, an antioxidant, a corrosion inhibitor, an antifoaming agent, a thickener, a tack fire, a coupling agent, an electrostatic imparting agent, a polymerization inhibitor, a thixotropic agent, an antisettling agent, and the like are used. be able to. Specifically, for example, polyethylene glycol ester compounds, polyethylene glycol ether compounds, polyoxyethylene sorbitan ester compounds, sorbitan alkyl ester compounds, aliphatic polycarboxylic acid compounds, phosphate ester compounds, amide amine salts of polyester acids, polyethylene oxide A series compound, a fatty acid amide wax and the like can be used.

樹脂としては公知の種類が使用可能であり、エチルセルロース、ニトロセルロース、ポリビニールブチラール、フェノール樹脂、メラニン樹脂、ユリア樹脂、キシレン樹脂、アルキッド樹脂、不飽和ポリエステル樹脂、アクリル樹脂、ポリイミド樹脂、フラン樹脂、ウレタン樹脂、イソシアネート化合物、シアネート化合物等の熱硬化樹脂、ポリエチレン、ポリプロピレン、ポリスチレン、ＡＢＳ樹脂、ポリメタクリル酸メチル、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリ酢酸ビニル、ポリビニルアルコール、ポリアセタール、ポリカーボネート、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリフェニレンオキサイド、ポリスルフォン、ポリイミド、ポリエーテルスルフォン、ポリアリレート、ポリエーテルエーテルケトン、ポリ４フッ化エチレン、シリコン樹脂等の二種以上を組み合わせて用いることができる。   Known types of resins can be used, and ethyl cellulose, nitrocellulose, polyvinyl butyral, phenol resin, melanin resin, urea resin, xylene resin, alkyd resin, unsaturated polyester resin, acrylic resin, polyimide resin, furan resin, Urethane resin, isocyanate compound, thermosetting resin such as cyanate compound, polyethylene, polypropylene, polystyrene, ABS resin, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyacetal, polycarbonate, polyethylene terephthalate, Polybutylene terephthalate, polyphenylene oxide, polysulfone, polyimide, polyethersulfone, polyarylate, polyetherether ketone Emissions, polytetrafluoroethylene, can be used in combination of two or more kinds of such as silicon resin.

有機ビヒクルに含まれる樹脂、溶剤、各種添加剤の割合は任意に調整することができ、例えば、公知の有機ビヒクルと同様の成分比とすることができる。   The proportions of the resin, solvent, and various additives contained in the organic vehicle can be arbitrarily adjusted. For example, the component ratios can be the same as those of known organic vehicles.

有機ビヒクルの含有比率は特に限定されないが、例えば、良好な印刷性を有するという観点から、導電性材料１００質量部に対して、１０〜５００質量部であることが好ましく、２０〜４５質量部であることが特に好ましい。また、特にアルミニウム粉末１００質量部に対して、１０〜５００質量部であることが好ましく、２０〜４５質量部であることが好ましい。   Although the content ratio of the organic vehicle is not particularly limited, for example, from the viewpoint of having good printability, it is preferably 10 to 500 parts by mass, and preferably 20 to 45 parts by mass with respect to 100 parts by mass of the conductive material. It is particularly preferred that there is. In addition, the amount is particularly preferably from 10 to 500 parts by mass, and more preferably from 20 to 45 parts by mass, per 100 parts by mass of the aluminum powder.

本発明のペースト組成物は、例えば、太陽電池セルの電極層（特には図１で示されるようなＰＥＲＣ型太陽電池セルの裏面電極８）を形成するための使用として適している。よって、本発明のペースト組成物は、太陽電池裏面電極形成剤としても使用され得る。   The paste composition of the present invention is suitable for use, for example, for forming an electrode layer of a solar cell (particularly, a back electrode 8 of a PERC-type solar cell as shown in FIG. 1). Therefore, the paste composition of the present invention can also be used as a solar cell back electrode forming agent.

３．裏面電極の形成方法
本発明の結晶系太陽電池セルの裏面電極（図１の裏面電極８）の形成方法は、
開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対して、前記開口部を被覆するように、ガラス粉末、有機ビヒクル及び導電性材料を含有する太陽電池用ペースト組成物を塗布することにより塗膜を形成する工程１、並びに、
前記塗膜を７００〜９００℃で焼成する工程２、を有し、
（１）前記開口部は直径が１００μｍ以下であり、前記開口部の総面積は前記結晶系太陽電池セルの面積の０．５〜５％であり、
（２）前記導電性材料は、アルミニウム粉末と、長径が５μｍ以下のシリコンの初晶を有するアルミニウム−シリコン合金粉末とを含有する、
ことを特徴とする。 3. Method for Forming Back Electrode The method for forming the back electrode (back electrode 8 in FIG. 1) of the crystalline solar cell of the present invention is as follows.
By applying a solar cell paste composition containing a glass powder, an organic vehicle and a conductive material to a crystalline solar cell having a passivation film having an opening so as to cover the opening. Step 1 of forming a coating film, and
Baking the coating film at 700 to 900 ° C.,
(1) The opening has a diameter of 100 μm or less, and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell,
(2) The conductive material contains an aluminum powder and an aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5 μm or less,
It is characterized by the following.

結晶系太陽電池セル及び太陽電池用ペースト組成物については、基本的には前述の通りであるが、パッシベーション膜に設けた開口部の直径は１００μｍ以下の中でも、２０〜１００μｍであることが好ましい。開口部は、通常、レーザー照射などで形成できる。   The crystalline solar cell and the paste composition for a solar cell are basically as described above, but the diameter of the opening provided in the passivation film is preferably 20 to 100 μm, even if it is 100 μm or less. The opening can be usually formed by laser irradiation or the like.

本発明の裏面電極の形成方法は、工程１において、開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対して、前記開口部を被覆するように、太陽電池用ペースト組成物を塗布することにより塗膜を形成する。   In the method for forming a back electrode according to the present invention, in a step 1, a solar cell paste composition is applied to a crystalline solar cell having a passivation film having an opening so as to cover the opening. This forms a coating film.

ペースト組成物の塗膜を形成する際は、スクリーン印刷などの公知の塗工方法を用いて行うことができる。塗膜の厚さは、焼成後の裏面電極の厚さに応じて設定できるが、パッシベーション膜の平面部（開口部以外）を基準として５〜４０μｍ程度が好ましい。   When a coating film of the paste composition is formed, a known coating method such as screen printing can be used. Although the thickness of the coating film can be set according to the thickness of the back electrode after firing, it is preferably about 5 to 40 μm based on the flat portion (except for the opening) of the passivation film.

工程１により塗膜を形成後は、工程２において、塗膜を７００〜９００℃で焼成する。焼成温度は７００〜９００℃でよいが、７８０〜９００℃程度が好ましい。   After forming the coating film in Step 1, in Step 2, the coating film is baked at 700 to 900 ° C. The firing temperature may be 700 to 900 ° C, but is preferably about 780 to 900 ° C.

焼成により、ペースト組成物に含まれるアルミニウムが、シリコン半導体基板１の内部に拡散し、電極層５とシリコン半導体基板１との間にアルミニウム−シリコン（Ａｌ−Ｓｉ）合金層（合金層６）が形成され、これと同時に、アルミニウム原子の拡散によって、不純物層としてのｐ＋層７が形成される。By the firing, aluminum contained in the paste composition diffuses into silicon semiconductor substrate 1, and an aluminum-silicon (Al-Si) alloy layer (alloy layer 6) is formed between electrode layer 5 and silicon semiconductor substrate 1. At the same time, the p + layer 7 as an impurity layer is formed by diffusion of aluminum atoms.

以下に実施例及び比較例を示して本発明を具体的に説明する。但し、本発明は実施例に限定されない。   Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the embodiments.

実施例１
（ペースト組成物の調製）
ガスアトマイズ法により生成したアルミニウム粉末と、同じくガスアトマイズ法により生成した長径が２．０μｍのシリコンの初晶を有するアルミニム−シリコン合金粉末を、４０質量％：６０質量％となるように調整した導電性材料１００質量部と、Ｂ２Ｏ３−Ｂｉ２Ｏ３−ＳｒＯ−ＢａＯ−Ｓｂ２Ｏ３＝４０／４０／１０／５／５（ｍｏｌ％）のガラス粉末１．５質量部を、エチルセルロースをブチルジグリコールに溶解した樹脂液３５質量部に、既知の分散装置（ディスパー）を用いてペースト化した。 Example 1
(Preparation of paste composition)
A conductive material in which aluminum powder produced by a gas atomization method and aluminum-silicon alloy powder similarly produced by a gas atomization method and having a primary crystal of silicon having a long diameter of 2.0 μm are adjusted to be 40% by mass: 60% by mass. 100 parts by mass, 1.5 parts by mass of glass powder of B 2 O 3 —Bi 2 O 3 —SrO—BaO—Sb 2 O 3 = 40/40/10/5/5 (mol%), and ethyl cellulose in butyl A paste was formed into 35 parts by mass of the resin solution dissolved in diglycol using a known dispersing device (disper).

なお、長径が２．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末は、シリコン含有量が２０原子％のアルミニウム−シリコン合金の溶湯に０．０１％のＰ（リン）を添加してアトマイズすることで調製した。
（太陽電池セルである焼成基板の作製）
評価用の太陽電池セルである焼成基板を次のように作製した。The aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 2.0 μm is atomized by adding 0.01% P (phosphorus) to a molten aluminum-silicon alloy having a silicon content of 20 atom%. It was prepared by doing.
(Preparation of fired substrate as solar cell)
A fired substrate as a solar cell for evaluation was prepared as follows.

まず、図２の（Ａ）に示すように、まず、厚みが１６０μｍのシリコン半導体基板１（抵抗値３Ω・ｃｍ。裏面側にパッシベーション膜を含む。）を準備した。そして、図２の（Ｂ）に示すように、レーザー発振器として波長が５３２ｎｍのＹＡＧレーザーを用いて、開口部の総面積がセル全体の３．１％となるように５００μｍ間隔で直径５０μｍのコンタクト孔９を形成した。なお、セル全体における開口部の総面積は、一つあたりの開口の半径の二乗にπを乗じて、これを隣り合う開口部間の距離（ピッチ）で除することで算出した。   First, as shown in FIG. 2A, a silicon semiconductor substrate 1 having a thickness of 160 μm (resistance value: 3 Ω · cm; including a passivation film on the back surface side) was prepared. Then, as shown in FIG. 2B, a YAG laser having a wavelength of 532 nm is used as a laser oscillator, and contacts having a diameter of 50 μm are arranged at intervals of 500 μm so that the total area of the openings is 3.1% of the entire cell. Hole 9 was formed. The total area of the openings in the entire cell was calculated by multiplying the square of the radius of each opening by π and dividing the result by the distance (pitch) between adjacent openings.

なお、図２では、パッシベーション膜は図示しておらずシリコン半導体基板１に含まれるものとして取り扱い、パッシベーション膜はシリコン半導体基板１の裏面側に３０ｎｍの酸化アルミニウム層と１００ｎｍの窒化ケイ素層との積層体として含まれている。   In FIG. 2, the passivation film is not shown and is treated as included in the silicon semiconductor substrate 1. The passivation film is formed by stacking a 30 nm aluminum oxide layer and a 100 nm silicon nitride layer on the back surface of the silicon semiconductor substrate 1. Included as body.

次に、図２の（Ｃ）に示すように、裏面全体（コンタクト孔９が形成されている側の面）を覆うように、上記で得たペースト組成物１０を、シリコン半導体基板１の表面上に、スクリーン印刷機を用いて、１．０〜１．１ｇ／ｐｃになるように印刷した。次いで、図示はしていないが、受光面に公知の技術で調製したＡｇペーストを印刷した。   Next, as shown in FIG. 2C, the paste composition 10 obtained above is applied to the surface of the silicon semiconductor substrate 1 so as to cover the entire back surface (the surface on the side where the contact holes 9 are formed). Using a screen printer, printing was performed on the upper surface so as to be 1.0 to 1.1 g / pc. Next, although not shown, an Ag paste prepared by a known technique was printed on the light receiving surface.

その後、８００℃に設定した赤外ベルト炉を用いて焼成した。この焼成により、図２の（Ｄ）に示すように、電極層５を形成し、また、この焼成の際にアルミニウムがシリコン半導体基板１の内部に拡散することにより、電極層５とシリコン半導体基板１との間にＡｌ−Ｓｉの合金層６が形成されると同時に、アルミニウム原子の拡散による不純物層としてｐ＋層（ＢＳＦ層）７が形成された。これにより、評価用の焼成基板を製作した。
（太陽電池セルの評価）
得られた太陽電池セルの評価においては、ワコム電創のソーラーシュミレータ：ＷＸＳ−１５６Ｓ−１０、Ｉ−Ｖ測定装置：ＩＶ１５０４０−１０を用いて、Ｉ−Ｖ測定を実施した。Ｅｆｆが２１．５％以上で合格とした。
（ボイド「Ｖｏｉｄ」の評価）
ボイドの評価については、焼成基板の断面を光学顕微鏡（２００倍）で観察し、シリコン半導体基板１と電極層５との界面におけるボイドの有無を評価した。ボイドが確認されなかったものを合格（○）、ボイドが確認されたものを不合格（×）と評価した。
（静的機械荷重試験後の変換効率の低下率）
静的機械荷重試験後の変換効率の低下率は、ＩＥＣ６１２１５に従い特定した。具体的には、２４００Ｐａの静荷重を水平に設置したモジュールの表面及び裏面に１時間行い、これを３サイクル繰り返し、その後ソーラーシュミレータを用いて変換効率の測定を行い、試験前後での低下率を計算した。なお、モジュールは、ガラス及びバックシートの間に封止材を挟持し、封止材中に太陽電池セルを直列に配列することで作製した。Thereafter, firing was performed using an infrared belt furnace set at 800 ° C. By this baking, as shown in FIG. 2D, an electrode layer 5 is formed, and at the time of this baking, aluminum diffuses into the silicon semiconductor substrate 1 to form the electrode layer 5 and the silicon semiconductor substrate. At the same time, an Al + Si alloy layer 6 was formed, and at the same time, ap + layer (BSF layer) 7 was formed as an impurity layer by diffusion of aluminum atoms. Thus, a fired substrate for evaluation was manufactured.
(Evaluation of solar cells)
In the evaluation of the obtained solar cell, IV measurement was performed using a Wacom Denso's solar simulator: WXS-156S-10 and an IV measurement device: IV15040-10. Eff was 21.5% or more and passed.
(Evaluation of void "Void")
Regarding the evaluation of voids, the cross section of the fired substrate was observed with an optical microscope (magnification: 200), and the presence or absence of voids at the interface between the silicon semiconductor substrate 1 and the electrode layer 5 was evaluated. Those in which voids were not confirmed were evaluated as pass (○), and those in which voids were confirmed were evaluated as failed (x).
(Decrease in conversion efficiency after static mechanical load test)
The conversion efficiency reduction rate after the static mechanical load test was specified in accordance with IEC61215. Specifically, a static load of 2400 Pa is applied to the front and back surfaces of the horizontally placed module for one hour, and this is repeated for three cycles. Thereafter, the conversion efficiency is measured using a solar simulator, and the reduction rate before and after the test is measured. Calculated. The module was manufactured by sandwiching a sealing material between glass and a back sheet, and arranging solar cells in series in the sealing material.

各評価結果を下記表１に示す。   The results of each evaluation are shown in Table 1 below.

実施例２
開口部の総面積がセル全体の３．１％となるように３００μｍ間隔で直径３０μｍのコンタクト孔９を形成したセルを用いた以外は、実施例１と同様にして評価を行った。 Example 2
The evaluation was performed in the same manner as in Example 1 except that cells having contact holes 9 having a diameter of 30 μm were formed at intervals of 300 μm so that the total area of the openings was 3.1% of the entire cell.

実施例３
開口部の総面積がセル全体の３．１％となるように７００μｍ間隔で直径７０μｍのコンタクト孔を形成したセルを用いた以外は、実施例１と同様にして評価を行った。 Example 3
Evaluation was performed in the same manner as in Example 1 except that cells having contact holes with a diameter of 70 μm were formed at intervals of 700 μm so that the total area of the openings was 3.1% of the entire cell.

実施例４
ガスアトマイズ法により生成したアルミニウム粉末と、同じくガスアトマイズ法により生成した長径が４．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末を、３０質量％：７０質量％となるように調整した以外は実施例１と同様にしてペースト組成物を調製し、評価を行った。 Example 4
The procedure was performed except that the aluminum powder produced by the gas atomization method and the aluminum-silicon alloy powder similarly produced by the gas atomization method and having the primary crystal of silicon having a long diameter of 4.0 μm were adjusted to 30% by mass: 70% by mass. A paste composition was prepared and evaluated in the same manner as in Example 1.

なお、長径が４．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末は、シリコン含有量が２３原子％のアルミニウム−シリコン合金の溶湯に、１０３Ｋ／Ｓｅｃの冷却速度でアトマイズすることで調製した。   The aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 4.0 μm was prepared by atomizing a melt of an aluminum-silicon alloy having a silicon content of 23 atom% at a cooling rate of 103 K / Sec. .

実施例５
ガスアトマイズ法により生成したアルミニウム粉末と、同じくガスアトマイズ法により生成した長径が５．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末を、５０質量％：５０質量％となるように調整した以外は実施例１と同様にしてペースト組成物を調製し、評価を行った。 Example 5
Except that the aluminum powder produced by the gas atomization method and the aluminum-silicon alloy powder also produced by the gas atomization method and having the primary crystal of silicon having a long diameter of 5.0 μm were adjusted to 50% by mass: 50% by mass. A paste composition was prepared and evaluated in the same manner as in Example 1.

なお、長径が５．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末は、シリコン含有量が２５原子％のアルミニウム−シリコン合金の溶湯を用いてＨｅガスでアトマイズすることで調製した。   The aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5.0 μm was prepared by atomizing with a He gas using a molten aluminum-silicon alloy having a silicon content of 25 atom%.

比較例１
ガスアトマイズ法により生成したアルミニウム粉末のみを用いた以外は、実施例１と同様にしてペーストを作成し、評価を行った。つまり、比較例１ではシリコンの初晶を有するアルミニウム−シリコン合金粉末は用いていない。 Comparative Example 1
A paste was prepared and evaluated in the same manner as in Example 1, except that only the aluminum powder produced by the gas atomizing method was used. That is, in Comparative Example 1, an aluminum-silicon alloy powder having a primary crystal of silicon was not used.

比較例２
ガスアトマイズ法により生成したアルミニウム粉末と、同じくガスアトマイズ法により生成した長径が７．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末を、５０質量％：５０質量％となるように調整した以外は実施例１と同様にしてペーストを作成し、評価を行った。 Comparative Example 2
Except that the aluminum powder produced by the gas atomization method and the aluminum-silicon alloy powder produced by the gas atomization method and having the primary crystal of silicon having a major axis of 7.0 μm were adjusted to 50% by mass: 50% by mass. A paste was prepared and evaluated in the same manner as in Example 1.

なお、長径が７．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末は、シリコン含有量が３５原子％のアルミニウム−シリコン合金の溶湯に０．００５％のＰ（リン）を添加してアトマイズすることで調製した。   The aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 7.0 μm is atomized by adding 0.005% P (phosphorus) to a molten aluminum-silicon alloy having a silicon content of 35 atom%. It was prepared by doing.

比較例３
ガスアトマイズ法により生成したアルミニウム粉末と、同じくガスアトマイズ法により生成した長径が１０．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末を、５０質量％：５０質量％となるように調整した以外は実施例１と同様にしてペーストを作成し、評価を行った。 Comparative Example 3
Except that the aluminum powder produced by the gas atomization method and the aluminum-silicon alloy powder similarly produced by the gas atomization method and having a primary crystal of silicon having a major axis of 10.0 μm were adjusted to 50% by mass: 50% by mass. A paste was prepared and evaluated in the same manner as in Example 1.

なお、長径が１０．０μｍのシリコンの初晶を有するアルミニム−シリコン合金粉末は、シリコン含有量が４０原子％のアルミニウム−シリコン合金の溶湯をアトマイズすることで調製した。   The aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 10.0 μm was prepared by atomizing a molten aluminum-silicon alloy having a silicon content of 40 atomic%.

比較例４
ガスアトマイズ法により生成したアルミニウム粉末と、同じくガスアトマイズ法により生成した長径が６．０μｍのシリコンの初晶を有するアルミニウム−シリコン合金粉末を、５０質量％：５０質量％となるように調整した以外は実施例１と同様にしてペーストを作成し、評価を行った。 Comparative Example 4
Except that the aluminum powder produced by the gas atomization method and the aluminum-silicon alloy powder similarly produced by the gas atomization method and having the primary crystal of silicon having a long diameter of 6.0 μm were adjusted to 50% by mass: 50% by mass. A paste was prepared and evaluated in the same manner as in Example 1.

なお、長径が６．０μｍのシリコンの初晶を有するアルミニム−シリコン合金粉末は、シリコン含有量が３５原子％のアルミニウム−シリコン合金の溶湯をアトマイズすることで調製した。   The aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 6.0 μm was prepared by atomizing a molten aluminum-silicon alloy having a silicon content of 35 atomic%.

比較例５
開口部の総面積がセル全体の３．１％となるように１１００μｍ間隔で直径１１０μｍのコンタクト孔９を形成したセルを用いた以外は、実施例１と同様にして評価を行った。 Comparative Example 5
Evaluation was performed in the same manner as in Example 1 except that cells having contact holes 9 having a diameter of 110 μm were formed at intervals of 1100 μm so that the total area of the openings was 3.1% of the entire cell.

比較例６
開口部の総面積がセル全体の０．４％となるように１４００μm等間隔で直径５０μｍのコンタクト孔９を形成したセルを用いた以外は、実施例１と同様にして評価を行った。 Comparative Example 6
Evaluation was performed in the same manner as in Example 1 except that cells having contact holes 9 having a diameter of 50 μm were formed at regular intervals of 1400 μm so that the total area of the openings was 0.4% of the entire cell.

比較例７
開口部の総面積がセル全体の６．１％となるように３６０μｍ等間隔で直径５０μｍのコンタクト孔９を形成したセルを用いた以外は、実施例１と同様にして評価を行った。 Comparative Example 7
Evaluation was performed in the same manner as in Example 1 except that cells having contact holes 9 having a diameter of 50 μm were formed at regular intervals of 360 μm so that the total area of the openings was 6.1% of the entire cell.

Figure 2018180441
Figure 2018180441

表１結果から明らかな通り、本発明所定の導電性材料を用いることにより、パッシベーション膜の開口部の直径が１００μｍ以下であり、開口部の総面積が結晶系太陽電池セルの面積の０．５〜５％である結晶系太陽電池セルに対して適用した場合でも優れた変換効率が達成できる（Ｅｆｆが２２．０％以上）とともに、焼成後の電極層界面でのボイドの発生を抑制し、更に静的機械荷重試験後の変換効率の低下率を抑制（低下率３％未満）できることが分かる。   As is clear from the results shown in Table 1, by using the predetermined conductive material of the present invention, the diameter of the opening of the passivation film is 100 μm or less, and the total area of the opening is 0.5% of the area of the crystalline solar cell. Excellent conversion efficiency can be achieved even when applied to a crystalline solar cell of up to 5% (Eff is 22.0% or more), and the generation of voids at the electrode layer interface after firing is suppressed, Further, it can be seen that the rate of decrease in the conversion efficiency after the static mechanical load test can be suppressed (less than 3%).

１：シリコン半導体基板
２：ｎ型不純物層
３：反射防止膜（パッシベーション膜）
４：グリッド電極
５：電極層
６：合金層
７：ｐ＋層
８：裏面電極
９：コンタクト孔（開口部）
１０：ペースト組成物1: silicon semiconductor substrate 2: n-type impurity layer 3: antireflection film (passivation film)
4: grid electrode 5: electrode layer 6: alloy layer 7: p + layer 8: back electrode 9: contact hole (opening)
10: Paste composition

Claims (6)

開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対してｐ＋層を形成する用途に用いる、ガラス粉末、有機ビヒクル及び導電性材料を含有する太陽電池用ペースト組成物であって、
（１）前記開口部は直径が１００μｍ以下であり、前記開口部の総面積は前記結晶系太陽電池セルの面積の０．５〜５％であり、
（２）前記導電性材料は、アルミニウム粉末と、長径が５μｍ以下のシリコンの初晶を有するアルミニウム−シリコン合金粉末とを含有する、
ことを特徴とする太陽電池用ペースト組成物。A solar cell paste composition containing a glass powder, an organic vehicle, and a conductive material, which is used for forming ap + layer for a crystalline solar cell having a passivation film provided with an opening,
(1) The opening has a diameter of 100 μm or less, and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell,
(2) The conductive material contains an aluminum powder and an aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5 μm or less,
A paste composition for a solar cell, comprising: 前記アルミニウム粉末１００質量部に対して、前記アルミニウム−シリコン合金粉末４０〜７００質量部、前記ガラス粉末０．１〜１５質量部、及び前記有機ビヒクル２０〜４５質量部を含有する、請求項１に記載の太陽電池用ペースト組成物。   The aluminum-silicon alloy powder contains 40 to 700 parts by mass, the glass powder 0.1 to 15 parts by mass, and the organic vehicle 20 to 45 parts by mass with respect to 100 parts by mass of the aluminum powder. The paste composition for a solar cell according to the above. 前記開口部の直径が２０〜１００μｍである、請求項１又は２に記載の太陽電池用ペースト組成物。   The solar cell paste composition according to claim 1, wherein the diameter of the opening is 20 to 100 μm. 開口部を設けたパッシベーション膜を有する結晶系太陽電池セルに対して、前記開口部を被覆するように、ガラス粉末、有機ビヒクル及び導電性材料を含有する太陽電池用ペースト組成物を塗布することにより塗膜を形成する工程１、並びに、
前記塗膜を７００〜９００℃で焼成する工程２、
を有する、結晶系太陽電池セルの裏面電極の形成方法であって、
（１）前記開口部は直径が１００μｍ以下であり、前記開口部の総面積は前記結晶系太陽電池セルの面積の０．５〜５％であり、
（２）前記導電性材料は、アルミニウム粉末と、長径が５μｍ以下のシリコンの初晶を有するアルミニウム−シリコン合金粉末とを含有する、
ことを特徴とする裏面電極の形成方法。By applying a solar cell paste composition containing a glass powder, an organic vehicle and a conductive material to a crystalline solar cell having a passivation film having an opening so as to cover the opening. Step 1 of forming a coating film, and
Baking the coating film at 700 to 900 ° C.,
A method for forming a back electrode of a crystalline solar cell, comprising:
(1) The opening has a diameter of 100 μm or less, and the total area of the opening is 0.5 to 5% of the area of the crystalline solar cell,
(2) The conductive material contains an aluminum powder and an aluminum-silicon alloy powder having a primary crystal of silicon having a major axis of 5 μm or less,
A method for forming a back electrode, comprising: 前記アルミニウム粉末１００質量部に対して、前記アルミニウム−シリコン合金粉末４０〜７００質量部、前記ガラス粉末０．１〜１５質量部、及び前記有機ビヒクル２０〜４５質量部を含有する、請求項４に記載の裏面電極の形成方法。   The aluminum-silicon alloy powder contains 40 to 700 parts by mass, the glass powder 0.1 to 15 parts by mass, and the organic vehicle 20 to 45 parts by mass with respect to 100 parts by mass of the aluminum powder. The method for forming the back electrode described in the above. 前記開口部の直径が２０〜１００μｍである、請求項４又は５に記載の裏面電極の形成方法。   The method for forming a back electrode according to claim 4, wherein the diameter of the opening is 20 to 100 μm.
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