WO2015092901A1

WO2015092901A1 - Electrode connection set, method for manufacturing solar cell, solar cell, and solar cell module

Info

Publication number: WO2015092901A1
Application number: PCT/JP2013/084126
Authority: WO
Inventors: 修一郎足立; 吉田　誠人; 野尻　剛; 倉田　靖; 祥晃栗原
Original assignee: 日立化成株式会社
Priority date: 2013-12-19
Filing date: 2013-12-19
Publication date: 2015-06-25

Abstract

　The present invention provides: an electrode connection set comprising an electrode composition and a connection material containing an adhesive; a solar cell manufacturing method for manufacturing a solar cell using said electrode set; a solar cell obtained using said manufacturing method; and a solar cell module having said solar cell and a sealant for sealing said solar cell so that part of a wiring member in said solar cell is exposed. The electrode composition contains phosphorus-containing copper alloy particles, tin-containing particles, glass particles, and a dispersion medium.

Description

Electrode connection set, solar cell manufacturing method, solar cell, and solar cell module

The present invention relates to an electrode connection set, a solar cell manufacturing method using the electrode connection set, a solar cell, and a solar cell module.

Generally, electrodes are formed on the light receiving surface and the back surface of a solar cell element provided with a silicon substrate. In order to efficiently extract the electrical energy converted in the solar cell element due to the incidence of light to the outside, it is necessary that the volume resistivity of the electrode is sufficiently low and that a good ohmic contact is formed with the silicon substrate. It is.

The electrodes used in the solar cell element include a light receiving surface current collecting electrode, a light receiving surface output extraction electrode, a back surface current collecting electrode and a back surface output extraction electrode, and are usually formed as follows. First, a texture (unevenness) is formed on the light-receiving surface side of a p-type silicon substrate, and then an electrode composition (for electrodes) is formed on an n ⁺ -type diffusion layer formed by thermally diffusing phosphorus or the like at high temperature. The electrode is formed by applying a paste composition (which may be referred to as a paste composition) by screen printing or the like, and firing it in the atmosphere at 800 ° C. to 900 ° C. The electrode composition forming these electrodes contains conductive metal powder, glass particles, various additives and the like.

In addition to the back surface collecting electrode among the electrodes, an electrode composition containing silver particles is generally used as the conductive metal powder. The use of silver particles requires that the volume resistivity of the silver particles is as low as 1.6 × 10 ⁻⁶ Ω · cm, that the silver particles are self-reduced and sintered under the above firing conditions, and that the silicon substrate is in good ohmic contact. There are advantages such as being able to form a contact (electrical connection).

As described above, the electrode composition containing silver particles exhibits excellent characteristics as an electrode of a solar cell element. On the other hand, since silver is a precious metal and the bullion itself is expensive, and because of the problem of resources, a proposal for a material to replace silver is desired.
A promising material that can replace silver is copper that is applied to semiconductor wiring materials. Copper is abundant in terms of resources, and the cost of bullion is as low as about 1/100 of silver. However, copper is a material that is easily oxidized at a high temperature of 200 ° C. or higher in the atmosphere, and it is difficult to form an electrode in the above process.

In order to solve the above-mentioned problems that copper has, copper particles have been reported that give oxidation resistance to copper using various methods and are not easily oxidized even when subjected to high-temperature firing (for example, Japanese Patent Application Laid-Open No. 2005-2005). No. 314755 and Japanese Patent Application Laid-Open No. 2004-217952). In addition, as a method for suppressing the oxidation of copper during firing, a method using an electrode paste composition (electrode composition) containing copper-containing particles and glass particles has also been reported (for example, JP-A 2011 -171272).

Here, the structure of general solar cells and solar cell modules will be described. A general solar cell element has a size of, for example, 125 mm × 125 mm or 156 mm × 156 mm, and produces a small amount of power alone. Therefore, actually, a plurality of solar cell elements are collectively used as a solar cell and a solar cell module. In many cases, the solar cell and the solar cell module are connected in series and / or in parallel via a wiring member in which a plurality of solar cell elements are electrically connected to the output extraction electrodes on the light receiving surface and the back surface. Have a structure. In addition, since the solar cell module is used in an outdoor environment, a plurality of solar cell elements connected via wiring members are sealed with a sealing material in order to ensure resistance to temperature change, wind and rain, snow accumulation, etc. It is formed. Usually, sealing is performed by a vacuum laminator after a sealing material including tempered glass, an ethylene vinyl acetate (EVA) sheet, a back sheet, and the like is laminated and sandwiched between solar cells having wiring members. In addition, a solar cell element means here what has a semiconductor substrate which has a pn junction, and the electrode formed on the semiconductor substrate. A solar cell means the thing of the state by which the wiring member was provided on the solar cell element and the several solar cell element was connected through the wiring member as needed. The solar cell module means a solar cell provided with a wiring member, in which a part of the wiring member in the solar cell is exposed and sealed with a sealing material.

When connecting the electrode of the solar cell element and the wiring member, it is necessary to reduce the electrical contact resistance between the electrode and the wiring member in order to efficiently extract the electric energy converted in the solar cell element to the outside. There is. Further, when the solar cell module is manufactured, in order to prevent the solar cell element from dropping from the wiring member in the step of transporting the solar cell in a state where a plurality of solar cell elements are connected by the wiring member, It is necessary to firmly maintain the adhesion between the element electrode and the wiring member.

Generally, solder is used to connect the electrode of the solar cell element and the wiring member (see, for example, Japanese Patent Application Laid-Open Nos. 2004-204256 and 2005-050780). Solder is widely used because it is excellent in connection reliability such as conductivity and fixing strength, is inexpensive and versatile. In recent years, lead-free solder has also become widespread as a solder used for connection between the electrode of the solar cell element and the wiring member from the environmental viewpoint.

On the other hand, connection methods that do not use solder have also been proposed. For example, Japanese Patent Application Laid-Open Nos. 2000-286436, 2001-357897, and Japanese Patent No. 3448924 disclose a connection method using a conductive paste.

However, when lead-free solder is used, since the melting temperature of the solder is usually about 230 ° C. to 260 ° C., the high temperature associated with the connection or the volumetric shrinkage of the solder affects the semiconductor structure of the solar cell element. It may cause deterioration of the performance of the element.
Further, as described in Japanese Patent Application Laid-Open No. 2000-286436, Japanese Patent Application Laid-Open No. 2001-357897, or Japanese Patent No. 3448924, a method for connecting an electrode of a solar cell element and a wiring member using a conductive paste is disclosed. The power generation performance may deteriorate significantly with time under high temperature and high humidity conditions, and sufficient connection reliability has not always been obtained.
On the other hand, when the connection between the copper-containing electrode and the wiring member as described in JP 2011-171272 A is performed with solder or conductive paste, the adhesion between the copper-containing electrode of the solar cell element and the wiring member is low. There was a tendency to run out.

The present invention has been made in view of the above problems, and the connection between the copper-containing electrode of the solar cell element and the wiring member has a structure having high strength (good adhesion) and high reliability, and is further stable. It aims at providing the electrode connection set which can provide the solar cell which shows electric power generation performance, the manufacturing method of a solar cell using an electrode connection set, a solar cell, and a solar cell module.

The present invention is as follows.
[1] An electrode connection set including a composition for an electrode including phosphorus-containing copper alloy particles, tin-containing particles, glass particles, and a dispersion medium, and a connection material including an adhesive.
[2] The electrode connection set according to [1], wherein the electrode composition further includes nickel particles.
[3] The electrode connection set according to [1] or [2], wherein the connection material further includes a curing agent and a film forming material.
[4] The electrode connection set according to any one of [1] to [3], wherein the connection material further includes conductive particles.
[5] A step of applying the electrode composition onto a semiconductor substrate having a pn junction, a step of heat-treating the semiconductor substrate to which the electrode composition is applied, and forming a copper-containing electrode, and the copper Any one of [1] to [4] including a step of laminating the connection material and the wiring member on the containing electrode in this order to obtain a laminated body, and a step of heating and pressing the laminated body. The manufacturing method of the solar cell which manufactures a solar cell using the electrode connection set of claim | item.
[6] The method for manufacturing a solar cell according to [5], wherein the heat treatment is performed at 450 ° C. to 900 ° C.
[7] A solar cell obtained by the production method according to [5] or [6].
[8] A solar cell obtained by the manufacturing method according to [5] or [6] and a sealing material that seals the solar cell so that a part of the wiring member in the solar cell is exposed. And a solar cell module.

According to the present invention, it is possible to provide a solar cell that has a structure in which the connection between the copper-containing electrode of the solar cell element and the wiring member has high strength (good adhesion) and high reliability, and further exhibits stable power generation performance. The electrode connection set, the solar cell manufacturing method using the electrode connection set, the solar cell, and the solar cell module can be provided.

It is a schematic sectional drawing which shows an example of the solar cell element concerning this invention. It is a schematic plan view which shows an example of the light-receiving surface side electrode structure of the solar cell element concerning this invention. It is a schematic plan view which shows an example of the light-receiving surface side electrode structure of the solar cell element concerning this invention. It is a schematic plan view which shows an example of the back surface side electrode structure of the solar cell element concerning this invention. It is a schematic plan view which shows an example of the light-receiving surface of the solar cell of this invention. It is a schematic plan view which shows an example of the back surface of the solar cell of this invention. It is a schematic sectional drawing which shows an example of the structure which connected the two solar cells of this invention. It is a figure which shows an example of the cross section of the wiring connection part of the solar cell of this invention. It is a figure for demonstrating an example of the manufacturing method of the solar cell module of this invention.

The electrode connection set of the present invention includes an electrode composition containing phosphorus-containing copper alloy particles, tin-containing particles, glass particles and a dispersion medium, a connection material containing an adhesive, and other elements as necessary.
Since the electrode connection set includes the electrode composition and the connection material in combination, an electrode obtained from the electrode composition using the connection material by further preparing a wiring member; The wiring member can be connected. In a solar cell in which the electrode obtained from the electrode composition obtained by using the present set and the wiring member are connected, the wiring connection portion between the electrode and the wiring member has high connection strength (adhesion). And high connection reliability.

This can be considered as follows, for example.
The copper-containing electrode formed by firing the electrode composition of the electrode connection set according to the present invention includes a metal portion showing an alloy phase containing copper and tin such as a Cu—Sn alloy phase, and a tin such as a Sn—PO glass phase. And a glass part containing phosphorus and oxygen. Among these, the Cu—Sn alloy phase forms a dense bulk metal part, and at the same time, creates a void in the electrode where the metal part and the glass part are not formed. This is presumably because the reaction during the formation of the bulk body and the sintering of the alloy phase proceed dramatically. It is preferable that the glass part is disposed between the semiconductor substrate and the metal part and is also present on the surface of the metal part.

The voids are open pores when viewed from the surface of the copper-containing electrode, and may reach the Sn—PO glass phase formed on the semiconductor substrate side. In addition, it is thought that the performance (for example, volume resistivity) as an electrode and the power generation performance of a solar cell element are not reduced by including the void in the copper-containing electrode. During the heat and pressure treatment of the laminate obtained by laminating the copper-containing electrode, the connection material, and the wiring member, the copper-containing electrode having this structure and the wiring member are thermocompression bonded with the connection material including the adhesive interposed therebetween. As a result, the connection strength between the copper-containing electrode and the wiring member is improved by a so-called anchor effect in which at least a part of the connection material enters the gap and the copper-containing electrode and the wiring member are dynamically bonded. Conceivable. As a result, it is considered that the reliability of the solar cell is improved and further stable power generation performance is exhibited. The portion where the copper-containing electrode and the wiring member are in contact may have a glass portion interposed between the copper-containing electrode and the wiring member, and the copper-containing electrode and the wiring member are in direct contact with each other. Also good.

On the other hand, when the connection between the copper-containing electrode and the wiring member is performed with solder or a conductive paste, the adhesion between the electrode and the wiring member is inferior to the case where the connection material is used. This is presumably because solder or conductive paste does not enter the gap formed in the copper-containing electrode as described above, and the anchor effect cannot be obtained.
Moreover, when the said composition for electrodes is not used, a space | gap part is hard to be formed in the electrode obtained after baking, the said anchor effect becomes small and there exists a possibility that the adhesiveness of an electrode and a wiring member may be inferior.
Thus, high adhesion between the electrode and the wiring member is first manifested by combining the electrode composition contained in the electrode connection set of the present invention and the connection material.

In addition, in the present invention, by combining the electrode composition and the connection material, a reduction in electrical contact resistance can be achieved separately from the connection strength. This can be considered as follows, for example.

As described above, the copper-containing electrode obtained from the electrode composition according to the present invention includes a void portion therein, and the connection material enters the void portion when the wiring member is thermocompression bonded. Here, a conductive layer including a metal part, a glass part, and a connection material is formed between the semiconductor substrate and the wiring member. At this time, the amount (volume) of the connection material entering the gap is increased as compared with an electrode having a small gap, for example, a conventional silver electrode, and as a result, the connection material interposed between the electrode and the wiring member. The thickness of the is significantly reduced. In addition, since the connection material is flow-excluded during the thermocompression bonding of the wiring member, the electrode and the wiring member are in direct contact with part of the conductive layer. As a result, the conductivity is improved and the electrical contact resistance between the electrode and the wiring member is reduced. In the portion where the electrode and the wiring member are in direct contact, the glass portion may be interposed between the metal portion and the wiring member, or the metal portion and the wiring member may be in direct contact. Furthermore, when the metal part and the wiring member are in direct contact, conductive components such as metal in the electrode and the wiring member are diffused from the contact part, so that the contact part is alloyed and the contact resistance is further reduced. This is also considered as one factor for improving the conductivity.

In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. .
In the present specification, “˜” indicates a range including the numerical values described before and after the minimum and maximum values, respectively.
Further, in the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. means.
In addition, in the present specification, the term “layer” includes a configuration of a shape formed in part in addition to a configuration of a shape formed on the entire surface when observed as a plan view.
The present invention will be described below.

[Electrode connection set]
The electrode connection set includes the electrode composition, the connection material, and other elements as necessary.
<Electrode composition>
The electrode composition includes phosphorus-containing copper alloy particles, tin-containing particles, glass particles, and a dispersion medium. A copper-containing electrode can be formed by applying this electrode composition to a semiconductor substrate having a pn junction and baking it. In the present invention, a silicon substrate is described as an example of a semiconductor substrate having a pn junction, but the semiconductor substrate in the present invention is not limited to a silicon substrate.

By using the electrode composition, the oxidation of copper during firing in the atmosphere is suppressed, and an electrode having a low resistivity can be formed. Furthermore, formation of a reactant phase between copper and the silicon substrate is suppressed, and a good ohmic contact can be formed between the formed electrode and the silicon substrate. This can be considered as follows, for example.

First, when the electrode composition of the present invention is fired, a Cu—Sn alloy phase and a Sn—PO glass phase are formed by the reaction between the phosphorus-containing copper alloy particles and the tin-containing particles. By forming the Cu—Sn alloy phase, an electrode having a low volume resistivity (hereinafter also simply referred to as “resistivity”) can be formed. Here, since the Cu—Sn alloy phase is generated at a relatively low temperature of about 500 ° C., the electrode can be fired at a low temperature, and the effect of reducing the process cost can be expected.

This can be considered as follows, for example.
Phosphorus-containing copper alloy particles and tin-containing particles react with each other in the firing step to form an electrode including a Cu—Sn alloy phase that is a metal part and a Sn—PO glass phase that is a glass part. The Cu—Sn alloy phase forms a dense bulk body between the Cu—Sn alloy phases. This bulk body is continuously formed in the electrode, and an electrode having a low resistivity is formed by functioning as a conductive layer. The dense bulk body here means a structure in which massive Cu—Sn alloy phases are in close contact with each other and are continuously formed in three dimensions.
On the other hand, the Sn—PO glass phase is formed between the Cu—Sn alloy phase and the silicon substrate. Thus, it can be considered that adhesion of the Cu—Sn alloy phase to the silicon substrate can be obtained.

It is preferable that the electrode composition further contains nickel-containing particles. As a result, it is considered that the Cu—Sn alloy phase and the nickel-containing particles further react to form a Cu—Sn—Ni alloy phase. Since this Cu—Sn—Ni alloy phase is formed even at a relatively high temperature of 800 ° C., it is considered that an electrode having a low resistivity can be formed while maintaining oxidation resistance even in a baking process at a higher temperature. In addition, by using a copper-containing electrode formed from an electrode composition containing the nickel-containing particles, better ohmic contact between the electrode and the silicon substrate can be achieved while maintaining adhesion to the silicon substrate. . The Cu-Sn-Ni alloy phase obtained by further including nickel-containing particles also forms a dense bulk body with the Cu-Sn-Ni alloy phase as well as the Cu-Sn alloy phase. To do. Note that even if the Cu—Sn alloy phase and the Cu—Sn—Ni alloy phase coexist in the electrode, it is considered that the function (for example, resistivity) is not lowered.

When copper particles imparted with oxidation resistance, which have been developed in the past, are used, the oxidation resistance is up to 300 ° C. at most, and it is almost oxidized at a high temperature of 800 ° C. to 900 ° C. For this reason, it has not been put into practical use as an electrode for a solar cell element, and further, an additive applied for imparting oxidation resistance inhibits sintering of copper particles, resulting in a resistivity like silver. There was a problem that a low electrode could not be obtained. In addition, as another technique for suppressing copper oxidation, a special method of firing a conductive composition using copper as a conductive metal powder in an atmosphere such as nitrogen has been proposed. In order to completely suppress the oxidation, an environment completely sealed with an atmospheric gas such as nitrogen is required, which is unsuitable for mass production of solar cell elements in terms of process costs.
According to the present invention, an electrode having a low resistivity can be formed without using a special method.

In addition, when the Sn—PO glass phase functions as a barrier layer for preventing mutual diffusion between copper and silicon, a good ohmic contact between the electrode formed by firing and the silicon substrate can be achieved. Can think. That is, the Sn—PO glass phase suppresses the formation of a reactant phase (Cu ₃ Si) formed when an electrode containing copper and silicon are heated in direct contact with each other, and the semiconductor performance (for example, pn It is considered that good ohmic contact can be expressed while maintaining adhesion to the silicon substrate without deteriorating the bonding characteristics.
Conventionally, ohmic contact with a silicon substrate has been cited as a problem for applying copper to an electrode of a solar cell element. The formation of Cu ₃ Si may extend to several μm from the interface of the silicon substrate, which may cause cracks on the silicon substrate side and cause performance deterioration of the solar cell element. In addition, the formed Cu ₃ Si lifts the electrode containing copper, etc., thereby hindering the adhesion between the electrode and the silicon substrate, which may lead to a decrease in the mechanical strength of the electrode.
According to the present invention, since the formation of the reactant phase (Cu ₃ Si) can be suppressed, good ohmic contact properties can be exhibited.

Hereinafter, each component contained in the composition for an electrode used in the present invention will be described in detail.
(Phosphorus-containing copper alloy particles)
The electrode composition contains phosphorus-containing copper alloy particles. As a phosphorus-containing copper alloy, a brazing material called phosphorus copper brazing (phosphorus content: about 7% by mass or less) is known. Phosphorus copper brazing is also used as a bonding agent between copper and copper. By using phosphorous-containing copper alloy particles in the electrode composition of the present invention, the reductivity of phosphorous to copper oxide is utilized. An electrode having excellent oxidation resistance and low resistivity can be formed. Furthermore, the electrode can be fired at a low temperature, and the effect that the process cost can be reduced can be obtained.

From the viewpoint of oxidation resistance and resistivity, the content of phosphorus atoms contained in the phosphorus-containing copper alloy particles is preferably 1% by mass or more and 8% by mass or less, and 1.5% by mass or more and 7.8% by mass. % Or less, more preferably 2% by mass or more and 7.5% by mass or less.
The content of copper atoms contained in the phosphorus-containing copper alloy particles is preferably 92% by mass or more and 99% by mass or less, more preferably 92.2% by mass or more and 98.5% by mass or less. More preferably, it is 5 mass% or more and 98 mass% or less.

In the electrode composition used in the present invention, the phosphorus-containing copper alloy particles may be used alone or in combination of two or more.

The phosphorus-containing copper alloy particles are an alloy containing copper and phosphorus, but may further contain other atoms. Other atoms include Ag, Mn, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Mo, Ti, Co, Ni, Au, etc. can be mentioned.
Moreover, the content rate of the other atom contained in the said phosphorus containing copper alloy particle can be 3 mass% or less in the said phosphorus containing copper alloy particle, for example, 1 mass from a viewpoint of oxidation resistance and a resistivity. % Or less is preferable.

The particle diameter of the phosphorus-containing copper alloy particles is not particularly limited, but the particle diameter when the volume integrated from the small particle diameter side is 50% (hereinafter sometimes abbreviated as “D50%”) is 0. It is preferably 4 μm to 10 μm, more preferably 1 μm to 7 μm. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the phosphorus containing copper alloy particle | grains in an electrode or the phosphorus containing copper alloy particle | grains, the tin containing particle | grains mentioned later, and the nickel containing particle added as needed becomes large because it is 10 micrometers or less. , The resistivity is more effectively reduced. The particle diameter of the phosphorus-containing copper alloy particles can be measured with a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
In addition, the shape of the phosphorus-containing copper alloy particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, etc., from the viewpoint of oxidation resistance and resistivity. It is preferably substantially spherical, flat, or plate-shaped.

The content of phosphorus-containing copper alloy particles in the electrode composition is not particularly limited. From the viewpoint of resistivity, the electrode composition is preferably 15% by mass or more and 75% by mass or less, more preferably 18% by mass or more and 70% by mass or less, and 20% by mass or more and 65% by mass or less. More preferably, it is more preferably 25% by mass or more and 50% by mass or less.

The phosphorus-containing copper alloy can be produced by a commonly used method. Also, the phosphorus-containing copper alloy particles can be prepared using a normal method of preparing metal powder using a phosphorus-containing copper alloy prepared so as to have a desired phosphorus content, for example, a water atomization method Can be produced by a conventional method. For details of the water atomization method, the description of Metal Handbook (Maruzen Co., Ltd. Publishing Division) can be referred to.
Specifically, after phosphorus-containing copper alloy is dissolved and powdered by nozzle spraying, the obtained powder is dried and classified, whereby desired phosphorus-containing copper alloy particles can be produced. Moreover, the phosphorus containing copper alloy particle | grains which have a desired particle diameter can be manufactured by selecting classification conditions suitably.

(Tin-containing particles)
The composition for electrodes used in the present invention contains tin-containing particles. By including the tin-containing particles, an electrode having a low resistivity can be formed in the electrode forming step described later.

The tin-containing particles are not particularly limited as long as they contain tin. Among them, at least one selected from tin particles and tin alloy particles is preferable, and at least one selected from tin alloy particles having a tin content of 1% by mass or more is preferable. In the electrode composition used in the present invention, the tin-containing particles may be used alone or in combination of two or more.
The purity of tin in the tin particles is not particularly limited. For example, the purity of the tin particles can be 95% by mass or more, preferably 97% by mass or more, and more preferably 99% by mass or more.

The type of alloy is not particularly limited as long as the tin alloy particles are alloy particles containing tin. Among these, from the viewpoint of reactivity with the melting point of the tin alloy particles, the phosphorus-containing copper alloy particles, and the nickel-containing particles added as necessary, the tin alloy particles having a tin content of 1% by mass or more. It is preferable that the tin content is preferably 3% by mass or more, more preferably tin alloy particles having a tin content of 5% by mass or more, more preferably tin content. A tin alloy particle having a rate of 10% by mass or more is particularly preferable. There is no restriction | limiting in particular about the upper limit of the content rate of tin.

The tin alloys contained in the tin alloy particles include Sn—Ag alloys, Sn—Cu alloys, Sn—Ag—Cu alloys, Sn—Ag—Sb alloys, Sn—Ag—Sb—Zn alloys, Sn -Ag-Cu-Zn alloy, Sn-Ag-Cu-Sb alloy, Sn-Ag-Bi alloy, Sn-Bi alloy, Sn-Ag-Cu-Bi alloy, Sn-Ag-In-Bi Alloy, Sn—Sb alloy, Sn—Bi—Cu alloy, Sn—Bi—Cu—Zn alloy, Sn—Bi—Zn alloy, Sn—Bi—Sb—Zn alloy, Sn—Zn alloy Sn—In alloy, Sn—Zn—In alloy, Sn—Pb alloy and the like.

Among the tin alloy particles, in particular, Sn-3.5Ag, Sn-0.7Cu, Sn-3.2Ag-0.5Cu, Sn-4Ag-0.5Cu, Sn-2.5Ag-0.8Cu-0 .5Sb, Sn-2Ag-7.5Bi, Sn-3Ag-5Bi, Sn-58Bi, Sn-3.5Ag-3In-0.5Bi, Sn-3Bi-8Zn, Sn-9Zn, Sn-52In, Sn-40Pb The tin alloy particles containing etc. have the same or lower melting point as Sn (232 ° C.). Therefore, these tin alloy particles are preferably used in that they melt at an initial stage of firing to cover the surface of the phosphorus-containing copper alloy particles and to react more uniformly with the phosphorus-containing copper alloy particles. it can. For example, in the case of Sn-AX-BY-CZ, the notation in the tin alloy includes A mass% of element X, B mass% of element Y, and C mass% of element Z in the tin alloy. Indicates that

The tin-containing particles may further contain other atoms that are inevitably mixed. Other atoms inevitably mixed include Ag, Mn, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Al, Zr, W , Mo, Ti, Co, Ni, Au and the like.
Further, the content of other atoms contained in the tin-containing particles can be, for example, 3% by mass or less in the tin-containing particles. From the viewpoint of the melting point and the reactivity with the phosphorus-containing copper alloy particles, 1% by mass. % Or less is preferable.

The particle diameter of the tin-containing particles is not particularly limited, but D50% is preferably 0.5 μm to 20 μm, more preferably 1 μm to 15 μm, and further preferably 5 μm to 15 μm. By setting the particle diameter of the tin-containing particles to 0.5 μm or more, the oxidation resistance of the tin-containing particles themselves is improved. Moreover, the contact area with the phosphorus containing copper alloy particle | grains in an electrode and the nickel containing particle added as needed becomes large because the particle diameter of a tin containing particle | grain is 20 micrometers or less, The reaction during baking is effective. move on. The particle size of the tin-containing particles can be measured with a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
Further, the shape of the tin-containing particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like. From the viewpoint of oxidation resistance and resistivity, a substantially spherical shape. It is preferably flat, plate-like.

The content of tin-containing particles in the electrode composition is not particularly limited. Especially, it is preferable that the content rate of the tin containing particle when the total content rate of the said phosphorus containing copper alloy particle and the said tin containing particle is 100 mass% is 5 mass% or more and 70 mass% or less, and 7 mass% It is more preferably 65% by mass or less, further preferably 9% by mass or more and 60% by mass or less, and particularly preferably 9% by mass or more and 45% by mass or less.
By making the content rate of a tin containing particle | grain 5 mass% or more, reaction with phosphorus containing copper alloy particle | grains can be produced more uniformly. Further, when the content of tin-containing particles is 70% by mass or less, the Cu—Sn alloy phase can be formed in a sufficient volume, and the resistivity of the electrode is further reduced.

The tin content in the electrode composition is not particularly limited. Especially, it is preferable that the content rate of tin in all the metals in the composition for electrodes is 5 mass% or more and 70 mass% or less, It is more preferable that it is 7 mass% or more and 65 mass% or less, 9 mass% or more More preferably, it is 60 mass% or less, and it is especially preferable that they are 9 mass% or more and 45 mass% or less.
By setting the tin content to 5% by mass or more, the reaction with the phosphorus-containing copper alloy particles can be caused more uniformly. In addition, when the content of tin is 70% by mass or less, the Cu—Sn alloy phase can be formed in a sufficient volume, and the resistivity of the electrode is further reduced.

(Nickel-containing particles)
The electrode composition used in the present invention preferably contains nickel-containing particles. By including nickel-containing particles in addition to phosphorus-containing copper alloy particles and tin-containing particles, oxidation resistance at higher temperatures can be expressed in the firing step. That is, by including nickel-containing particles, the electrode composition can be fired at a higher temperature.

The nickel-containing particles are not particularly limited as long as the particles contain nickel. Among these, at least one selected from nickel particles and nickel alloy particles is preferable, and at least one selected from nickel particles and nickel alloy particles having a nickel content of 1% by mass or more is preferable. In the electrode composition, the nickel-containing particles may be used singly or in combination of two or more.
The purity of nickel in the nickel particles is not particularly limited. For example, the purity of the nickel particles can be 95% by mass or more, preferably 97% by mass or more, and more preferably 99% by mass or more.

Also, the type of alloy is not limited as long as the nickel alloy particles are alloy particles containing nickel. Among these, from the viewpoint of the melting point of the nickel alloy particles and the reactivity with the phosphorus-containing copper alloy particles, the tin-containing particles and the Cu—Sn alloy phase, the nickel alloy particles may have a nickel content of 1% by mass or more. More preferably, the nickel alloy particles have a nickel content of 3% by mass or more, more preferably nickel alloy particles having a nickel content of 5% by mass or more, and a nickel content of 10%. Nickel alloy particles having a mass% or more are particularly preferred. There is no particular limitation on the upper limit of the nickel content.

Examples of the nickel alloy contained in the nickel alloy particles include a Ni—Fe alloy, a Ni—Cu alloy, a Ni—Cu—Zn alloy, a Ni—Cr alloy, a Ni—Cr—Ag alloy, and the like. In particular, nickel alloy particles containing Ni-58Fe, Ni-75Cu, Ni-6Cu-20Zn and the like can be suitably used in that they can more uniformly react with phosphorus-containing copper alloy particles and tin-containing particles. . For example, in the case of Ni-AX-BY-CZ, the nickel alloy contains A mass% of element X, B mass% of element Y, and C mass% of element Z in the nickel alloy. It shows that.

The nickel-containing particles may further contain other atoms inevitably mixed. Other atoms inevitably mixed include Ag, Mn, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Al, Zr, W , Mo, Ti, Co, Sn, Au and the like.
Moreover, the content rate of the other atom contained in the said nickel containing particle can be 3 mass% or less in the said nickel containing particle, for example, melting | fusing point, and the reactivity with phosphorus containing copper alloy particle | grains and tin containing particle | grains In view of the above, the content is preferably 1% by mass or less.

The particle diameter of the nickel-containing particles is not particularly limited, but as D50%, it is preferably 0.5 μm to 20 μm, more preferably 1 μm to 15 μm, and even more preferably 3 μm to 15 μm. When the thickness is 0.5 μm or more, the oxidation resistance of the nickel-containing particles themselves is improved. Moreover, the contact area with phosphorus containing copper alloy particle | grains and tin containing particle | grains in an electrode becomes large because it is 20 micrometers or less, and reaction with phosphorus containing copper alloy particle | grains and tin containing particle | grains advances effectively. The particle diameter of the nickel-containing particles can be measured with a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
Further, the shape of the nickel-containing particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, etc., but from the viewpoint of oxidation resistance and resistivity, a substantially spherical shape. It is preferably flat, plate-like.

Further, the content of nickel-containing particles in the electrode composition is not particularly limited. Among them, the content of the nickel-containing particles when the total content of the phosphorus-containing copper alloy particles, the tin-containing particles, and the nickel-containing particles is 100% by mass is 10% by mass to 70% by mass. Preferably, it is 12 mass% or more and 55 mass% or less, More preferably, it is 15 mass% or more and 50 mass% or less, It is especially preferable that it is 15 mass% or more and 35 mass% or less.
By setting the content of the nickel-containing particles to 10% by mass or more, the Cu—Sn—Ni alloy phase can be formed more uniformly. Further, when the content of the nickel-containing particles is 70% by mass or less, a sufficient volume of the Cu—Sn—Ni alloy phase can be formed, and the resistivity of the electrode is further reduced.

The nickel content in the electrode composition is not particularly limited. Especially, it is preferable that the nickel content rate in all the metals in an electrode composition is 10 mass% or more and 70 mass% or less, It is more preferable that it is 12 mass% or more and 55 mass% or less, 15 mass% or more and 50 mass% or less. % Or less, more preferably 15% by mass or more and 35% by mass or less.
By setting the nickel content to 10% by mass or more, the Cu—Sn—Ni alloy phase can be formed more uniformly. Further, when the nickel content is 70% by mass or less, a sufficient volume of the Cu—Sn—Ni alloy phase can be formed, and the resistivity of the electrode is further reduced.

The content ratio of the tin-containing particles and the nickel-containing particles added as necessary in the electrode composition is not particularly limited. From the viewpoint of adhesion to the silicon substrate, the mass ratio of nickel-containing particles to tin-containing particles (nickel-containing particles / tin-containing particles) is preferably 0.3 to 4.0, preferably 0.4 to 3.0. It is more preferable that

The content ratio of tin and nickel added as necessary in the electrode composition is not particularly limited. From the viewpoint of adhesion to the silicon substrate, the mass ratio of nickel to tin (nickel / tin) is preferably 0.3 to 4.0, and more preferably 0.4 to 3.0.

The content ratio of the phosphorus-containing copper alloy particles, the tin-containing particles, and the nickel-containing particles added as necessary in the electrode composition is not particularly limited. From the viewpoint of the resistivity of the electrode formed under high-temperature firing conditions and the adhesion to the silicon substrate, the mass ratio of the total amount of tin-containing particles and nickel-containing particles to the phosphorus-containing copper alloy particles ((nickel-containing particles + tin-containing particles ) / Phosphorus-containing copper alloy particles) is preferably 0.4 to 1.8, more preferably 0.6 to 1.4.

The content ratio of copper, tin, and nickel added as necessary in the electrode composition is not particularly limited. From the viewpoint of the resistivity of the electrode formed under high-temperature firing conditions and the adhesion to the silicon substrate, the mass ratio of the total amount of tin and nickel to copper ((nickel + tin) / copper) is 0.4 to 1.8. Is preferable, and 0.6 to 1.4 is more preferable.

Further, the ratio of the particle diameter of tin-containing particles (D50%) to the particle diameter of nickel-containing particles added as necessary (D50%) in the electrode composition is not particularly limited. From the viewpoint of the uniformity of the Sn—PO glass phase formed and the adhesion to the silicon substrate, the ratio of the particle diameter (D50%) of the nickel-containing particles to the particle diameter (D50%) of the tin-containing particles (nickel-containing) Particles / tin-containing particles) is preferably from 0.05 to 20, and more preferably from 0.5 to 10.

Further, the ratio of the particle diameter (D50%) of the phosphorus-containing copper alloy particles and the particle diameter (D50%) of the tin-containing particles in the electrode composition is not particularly limited. From the viewpoint of the resistivity of the electrode formed under high-temperature firing conditions and the adhesion to the silicon substrate, the ratio of the particle diameter (D50%) of the tin-containing particles to the particle diameter (D50%) of the phosphorus-containing copper alloy particles (tin content) Particles / phosphorus-containing copper alloy particles) is preferably 0.03 to 30, and more preferably 0.1 to 10.

In the electrode composition, the ratio of the particle size (D50%) of the phosphorus-containing copper alloy particles to the particle size (D50%) of the nickel-containing particles added as necessary is not particularly limited. From the viewpoint of the resistivity of the electrode formed under high-temperature firing conditions, the ratio of the particle diameter (D50%) of the nickel-containing particles to the particle diameter (D50%) of the phosphorus-containing copper alloy particles (nickel-containing particles / phosphorus-containing copper alloy particles) ) Is preferably 0.02 to 20, and more preferably 0.1 to 10.

From the viewpoint of oxidation resistance and electrode resistivity in the electrode composition, the total content of phosphorus-containing copper alloy particles, tin-containing particles, and nickel-containing particles added as necessary is from 60% by mass to 94%. It is preferable that it is mass% or less, and it is more preferable that it is 64 mass% or more and 88 mass% or less.

From the viewpoint of oxidation resistance and electrode resistivity, the content of all metals in the electrode composition is preferably 60% by mass to 94% by mass, and more preferably 64% by mass to 88% by mass. It is more preferable.

(Glass particles)
The composition for electrodes used in the present invention contains glass particles. When the electrode composition contains glass particles, the adhesion between the electrode and the silicon substrate is improved. Also. In particular, when forming an electrode on the light-receiving surface side of the solar cell, the silicon nitride film, which is an antireflection film, is removed by so-called fire-through during electrode formation, and an ohmic contact between the electrode and the silicon substrate is formed.

The glass particles are preferably glass particles containing glass having a glass softening temperature of 650 ° C. or lower and a crystallization start temperature exceeding 650 ° C. from the viewpoint of adhesion to a silicon substrate and electrode resistivity. . The glass softening temperature is measured by a usual method using a thermomechanical analyzer (TMA), and the crystallization start temperature is measured using a differential heat-thermogravimetric analyzer (TG-DTA). Measured by method.

When the electrode composition is used as an electrode on the solar cell light-receiving surface side, the glass particles soften and melt at the electrode formation temperature, oxidize the contacted silicon nitride film, and take in oxidized silicon dioxide. As long as the antireflection film can be removed, glass particles usually used in the technical field can be used without particular limitation.

In general, the glass particles contained in the electrode composition are preferably composed of glass containing lead from the viewpoint that silicon dioxide can be efficiently taken up. Examples of such glass containing lead include those described in Japanese Patent No. 3050064, and these can also be used favorably in the present invention.
In the present invention, it is preferable to use lead-free glass that does not substantially contain lead in consideration of the influence on the environment. Examples of the lead-free glass include lead-free glass described in paragraphs 0024 to 0025 of JP-A-2006-313744 and lead-free glass described in JP-A-2009-188281. It is also preferable to select the lead-free glass as appropriate and apply it to the electrode composition used in the present invention.

When the electrode composition is used as an electrode other than the electrode on the light receiving surface side of the solar cell, for example, as a back surface output extraction electrode, the glass softening temperature is 650 ° C. or lower and the crystallization start temperature exceeds 650 ° C. If it is a glass particle, it can be used without including a component required for fire through like the said lead.

As the glass component constituting the glass particles used in the electrode composition, silicon dioxide _(SiO 2), phosphorus oxide _(P _{2 O} 5), aluminum oxide _(Al _{2 O} 3), boron oxide _(B 2 _{O 3} ), Vanadium oxide (V ₂ O ₅ ), potassium oxide (K ₂ O), bismuth oxide (Bi ₂ O ₃ ), sodium oxide (Na ₂ O), lithium oxide (Li ₂ O), barium oxide (BaO), Strontium oxide (SrO), calcium oxide (CaO), magnesium oxide (MgO), beryllium oxide (BeO), zinc oxide (ZnO), lead oxide (PbO), cadmium oxide (CdO), tin oxide (SnO), zirconium oxide _(ZrO 2), tungsten oxide _(WO 3), molybdenum oxide _(MoO 3), lanthanum oxide _(La _{2 O} 3), acid Niobium _(Nb _{2 O} 5), tantalum oxide _(Ta _{2 O} 5), yttrium oxide _(Y _{2 O} 3), titanium oxide _(TiO 2), germanium oxide _(GeO 2), tellurium oxide _(TeO 2), lutetium oxide ( Lu ₂ O ₃ ), antimony oxide (Sb ₂ O ₃ ), copper oxide (CuO), iron oxide (FeO), silver oxide (Ag ₂ O), and manganese oxide (MnO).

Among them, it is preferable to use glass particles containing at least one selected from SiO ₂ , P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ , V ₂ O ₅ , Bi ₂ O ₃ , ZnO and PbO, More preferably, glass particles containing at least one selected from SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ and PbO are used. In the case of such glass particles, the softening temperature is more effectively lowered. Furthermore, in order to improve the wettability with phosphorus-containing copper alloy particles, tin-containing particles and nickel-containing particles added as necessary, sintering between the particles proceeds in the firing process, and an electrode with lower resistivity is obtained. Can be formed.

On the other hand, from the viewpoint of reducing the contact resistivity, glass particles containing phosphorous oxide (such as phosphate glass and P ₂ O ₅ glass particles) are preferable, and vanadium oxide is further contained in addition to phosphorous oxide. More preferred are glass particles (P ₂ O ₅ —V ₂ O ₅ based glass particles). By further containing vanadium oxide, the oxidation resistance is further improved and the contact resistivity of the electrode is further reduced. This can be attributed to, for example, that the softening temperature of the glass is lowered by further containing vanadium oxide. When using phosphorus oxide-vanadium oxide glass particles (P ₂ O ₅ —V ₂ O ₅ glass particles), the vanadium oxide content is preferably 1% by mass or more based on the total mass of the glass, It is more preferably 1% by mass to 70% by mass.

Although there is no restriction | limiting in particular as a particle diameter of the glass particle in the composition for electrodes used by this invention, The particle diameter (D50%) in case an integrated volume is 50% is 0.5 micrometer or more and 10 micrometers or less. It is preferably 0.8 μm or more and 8 μm or less. When the thickness is 0.5 μm or more, workability at the production of the electrode composition is improved. Moreover, it is more uniformly disperse | distributed in the composition for electrodes because it is 10 micrometers or less, a fire through can be efficiently produced in a baking process, and also adhesiveness with a silicon substrate improves. The particle size of the glass particles can be measured with a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
The shape of the glass particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and resistivity, It is preferably a flat shape or a plate shape.

The content of the glass particles is preferably 0.1% by mass to 12% by mass, more preferably 0.5% by mass to 10% by mass, based on the total mass of the electrode composition. More preferably, it is from 9% to 9% by mass. By including glass particles with a content in such a range, oxidation resistance, lower electrode resistivity, and lower contact resistivity can be achieved more effectively, and the phosphorus-containing copper alloy particles and tin-containing particles. And reaction between the nickel containing particles added as needed can be promoted.

The electrode composition has a glass particle content ratio (mass ratio) of 0.01 to 0.18 with respect to the total content of phosphorus-containing copper particles, tin-containing particles, and nickel-containing particles added as necessary. It is preferable that it is 0.03 to 0.15. By including glass particles with a content in such a range, oxidation resistance, lower electrode resistivity, and lower contact resistivity can be achieved more effectively, and the phosphorus-containing copper alloy particles, tin-containing particles, and The reaction between the nickel-containing particles can be promoted.

(Dispersion medium)
The electrode composition used in the present invention contains a dispersion medium. Thereby, the liquid physical properties (for example, viscosity and surface tension) of the electrode composition can be adjusted to the liquid physical properties required depending on the application method when applying to a semiconductor substrate or the like.
Examples of the dispersion medium include at least one of a solvent and a resin.

The solvent is not particularly limited, and hydrocarbon solvents such as hexane, cyclohexane, and toluene; halogenated hydrocarbon solvents such as dichloroethylene, dichloroethane, and dichlorobenzene; tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, 1,3-dioxolane Cyclic ether solvents such as trioxane, amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide; sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone and cyclohexanone; ethanol Alcohol solvents such as 2-propanol, 1-butanol and diacetone alcohol; 2,2,4-trimethyl-1,3-pentanediol monoacetate, 2,2,4- Limethyl-1,3-pentanediol monopropionate, 2,2,4-trimethyl-1,3-pentanediol monobutyrate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, Ester solvents of polyhydric alcohols such as 2,2,4-triethyl-1,3-pentanediol monoacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate; polyhydric alcohols such as butyl cellosolve, diethylene glycol monobutyl ether, diethylene glycol diethyl ether Ether solvents such as terpinene such as α-terpinene, terpineol such as α-terpineol, pinene such as α-pinene and β-pinene, myrcene, alloocimene, limonene, dipentene, carvone, o Examples include terpene solvents such as cymene and ferrandrene, and mixtures thereof.

The solvent is selected from an ester solvent of a polyhydric alcohol, a terpene solvent, and an ether solvent of a polyhydric alcohol from the viewpoint of imparting characteristics (coatability or printability) when forming the electrode composition on a semiconductor substrate. It is preferably at least one, and more preferably at least one selected from ester solvents of polyhydric alcohols and terpene solvents.
In the electrode composition used in the present invention, the solvent may be used alone or in combination of two or more.

In addition, as the resin, any resin that is usually used in the technical field can be used without particular limitation as long as it is a resin that can be thermally decomposed by baking treatment, and it may be a natural polymer compound or a synthetic polymer compound. Good. Specifically, cellulose resins such as methylcellulose, ethylcellulose, carboxymethylcellulose, and nitrocellulose; polyvinyl alcohol resin; polyvinylpyrrolidone resin; acrylic resin; vinyl acetate-acrylate copolymer; butyral resin such as polyvinyl butyral; phenol-modified alkyd Resins, alkyd resins such as castor oil fatty acid-modified alkyd resins; epoxy resins; phenol resins; rosin ester resins.

The resin in the electrode composition used in the present invention is preferably at least one selected from a cellulose resin and an acrylic resin from the viewpoint of disappearance in the electrode forming step.
In the present invention, the resins may be used alone or in combination of two or more.

Further, the weight average molecular weight of the resin in the present invention is not particularly limited. Among them, the weight average molecular weight is preferably from 5,000 to 500,000, and more preferably from 10,000 to 300,000. It exists in the tendency which can suppress that the viscosity of the composition for electrodes increases that the weight average molecular weight of the said resin is 5000 or more. If the weight average molecular weight of the resin is 5000 or more, the particles aggregate with each other due to steric repulsion when adsorbed on phosphorus-containing copper alloy particles, tin-containing particles and nickel-containing particles added as necessary. It is thought that it can be made difficult. On the other hand, when the weight average molecular weight of the resin is 500,000 or less, aggregation of the resins in the solvent is suppressed and the viscosity of the electrode composition tends to be suppressed from increasing. In addition, since the weight average molecular weight of the resin is 500,000 or less, it is suppressed that the combustion temperature of the resin becomes high, and the resin is not completely burned and remains as a foreign substance when the electrode composition is baked. Is suppressed, and an electrode having a lower resistivity tends to be formed.

In the electrode composition used in the present invention, the content of the dispersion medium can be appropriately selected according to the desired liquid properties and the type of the dispersion medium to be used. For example, the content of the dispersion medium is preferably 3% by mass or more and 40% by mass or less, more preferably 3% by mass or more and 39.9% by mass or less, based on the total mass of the electrode composition. More preferably, it is more than 35 mass% and it is especially preferably 7 mass% or more and 30 mass% or less.
When the content of the dispersion medium is within the above range, the application suitability when applying the composition for an electrode to a semiconductor substrate is improved, and an electrode having a desired width and height can be more easily formed. it can.
The types of the solvent and the resin in the dispersion medium and the content ratio in the dispersion medium can be appropriately selected in consideration of the method for applying the electrode composition.

Furthermore, in the electrode composition used in the present invention, from the viewpoint of oxidation resistance and electrode resistivity, the total content of phosphorus-containing copper alloy particles, tin-containing particles and nickel-containing particles added as necessary Is 60 mass% or more and 94 mass% or less, the glass particle content is 0.1 mass% or more and 12 mass% or less, and the dispersion medium content is 3 mass% or more and 39.9 mass% or less. Preferably, the total content of phosphorus-containing copper alloy particles, tin-containing particles and nickel particles added as necessary is 64 mass% or more and 88 mass% or less, and the glass particle content is 0.5. More preferably, the content of the dispersion medium is from 5% by mass to 10% by mass, and more preferably from 5% by mass to 35% by mass. Phosphorus-containing copper alloy particles, tin-containing particles, and nickel added as necessary The total content of the contained particles is 64 A is the amount% or more 88 wt% or less, the content of the glass particles is not more than 9 mass% 1 mass% or more, it is more preferable that the content ratio of the dispersion medium is 30 mass% or less 7 mass% or more.

(flux)
The electrode composition may contain a flux. By including the flux, the oxide film formed on the surface of the phosphorus-containing copper alloy particles can be removed, and the reduction reaction of the phosphorus-containing copper alloy particles during firing can be promoted. Further, since the melting of the tin-containing particles during firing proceeds, the reaction with the phosphorus-containing copper alloy particles proceeds, and as a result, the oxidation resistance is further improved and the resistivity of the formed electrode is further decreased. Furthermore, the effect that the adhesiveness of an electrode and a silicon substrate improves is also acquired.

The flux is not particularly limited as long as it can remove the oxide film formed on the surface of the phosphorus-containing copper alloy particles and promote the melting of the tin-containing particles. Specifically, fatty acids, boric acid compounds, fluorinated compounds, and borofluorinated compounds can be mentioned as preferred fluxes.

More specifically, the flux includes lauric acid, myristic acid, palmitic acid, stearic acid, sorbic acid, stearic acid, propionic acid, boron oxide, potassium borate, sodium borate, lithium borate, potassium borofluoride, borofluoride. Sodium fluoride, lithium borofluoride, acidic potassium fluoride, acidic sodium fluoride, acidic lithium fluoride, potassium fluoride, sodium fluoride, lithium fluoride and the like can be mentioned.
Among these, potassium borate and potassium borofluoride are particularly preferable fluxes from the viewpoints of heat resistance during electrode firing (characteristic that the flux does not volatilize at low temperatures during firing) and oxidation resistance complementation of the phosphorus-containing copper alloy particles.
In the electrode composition used in the present invention, each of these fluxes may be used alone or in combination of two or more.

In the electrode composition, the flux content in the case of containing the flux effectively expresses the oxidation resistance of the phosphorus-containing copper alloy particles, and promotes the melting of the tin-containing particles and the completion of the electrode firing. From the viewpoint of reducing the porosity of the part where the flux is sometimes removed, it is preferably 0.1% by mass to 5% by mass, and preferably 0.3% by mass to 4% by mass in the total mass of the electrode composition. More preferably, it is more preferably 0.5% to 3.5% by weight, particularly preferably 0.7% to 3% by weight, and 1% to 2.5% by weight. Very preferably.

(Other ingredients)
The electrode composition used in the present invention can further contain other components that are usually used in the technical field, if necessary, in addition to the components described above. Examples of other components include plasticizers, dispersants, surfactants, inorganic binders, metal oxides, ceramics, and organometallic compounds.

There is no restriction | limiting in particular as a manufacturing method of the composition for electrodes used by this invention. The phosphorus-containing copper alloy particles, the tin-containing particles, the glass particles, and the dispersion medium can be produced by dispersing or mixing them using a commonly used dispersion method or mixing method.
The dispersion method and the mixing method are not particularly limited, and can be appropriately selected and applied from commonly used dispersion methods and mixing methods.

<Connection material>
The connection material in the present invention includes an adhesive.
As long as the connection material includes an adhesive capable of connecting an electrode formed from the electrode composition and a wiring member to be described later in the manufacturing process of the solar cell, the shape, material, component, etc. There is no particular limitation. Examples of the shape of the connection material include a film shape, a paste shape, and a solution shape. About the shape of the said connection material, it can adjust suitably with the kind and content rate of the other component contained in a connection material. From the viewpoints of solar cell production efficiency, handleability, power generation performance stability, and the like, the connecting material is preferably in the form of a film.

From the viewpoint of forming a film-like connection material, the connection material preferably includes an adhesive, a curing agent, and a film-forming material.
As such a connection material, for example, a conductive adhesive film described in JP-A-2007-214533 can be exemplified, and these can be suitably used in the present invention. By using such a connection material, it is possible to provide a solar cell and a solar cell module that exhibit stable power generation performance. This can be considered as follows, for example.

When the electrode of the solar cell element and the wiring member are connected using the conductive adhesive film, it is possible to connect in a low temperature region around 200 ° C. Therefore, even when a thin solar cell element is used, the wiring Generation | occurrence | production of the curvature or crack in the case of a connection with a member can be suppressed. Further, since no solder seepage occurs at the time of solder connection, the light receiving area of the solar cell element can be expanded, and as a result, improvement in power generation performance can be expected.
By using the connection material, it is possible to expect effects such as improvement in power generation performance as described above.

Note that the conductive adhesive film described in Japanese Patent Application Laid-Open No. 2007-214533 contains conductive particles, and can exhibit conductivity between the substrates through the conductive particles during thermocompression bonding. The connection material used in the present invention is not limited to this composition, and may not contain the conductive particles. That is, when the connection material does not contain conductive particles, the copper-containing electrode and the wiring member can obtain conductivity by directly contacting the connection material at a portion where the connection material is flow-excluded by pressurization.

It is preferable that the connection material has a viscosity of 40000 Pa · s or less under conditions of thermocompression bonding of the wiring member. If the viscosity is 40000 Pa · s or less, it is possible to more easily enter the void formed in the electrode during thermocompression bonding of the wiring member. The viscosity of the connecting material is preferably 20000 Pa · s or less, and more preferably 15000 Pa · s or less. In addition, it is preferable that the viscosity of a connection material is 5000 Pa * s or more at the point of the handling in the manufacturing process of a solar cell.
The viscosity of the connecting material can be confirmed by using a shear viscometer measuring device (ARES) manufactured by Rheometric under the condition of a frequency of 10 Hz.
Hereinafter, each component will be described.

(adhesive)
The adhesive preferably exhibits insulating properties. The adhesive exhibiting insulating properties is not particularly limited, but it is preferable to use a thermosetting resin from the viewpoint of adhesion reliability.
A well-known thing can be used as a thermosetting resin, For example, an epoxy resin, a phenoxy resin, an acrylic resin, a polyimide resin, a polyamide resin, and a polycarbonate resin are mentioned. Among these, from the viewpoint of obtaining sufficient connection reliability, it is preferable to include at least one of an epoxy resin, a phenoxy resin, and an acrylic resin.

The content of the adhesive is not particularly limited. From the viewpoint of film formability before curing or adhesive strength after curing, it is preferably 20% by mass or more and 70% by mass or less in the connection material, more preferably 30% by mass or more and 60% by mass or less, More preferably, it is at least 50% by mass.

(Curing agent)
Examples of the curing agent that can be contained in the connecting material include an anion polymerizable catalyst type curing agent, a cationic polymerizable catalyst type curing agent, and a polyaddition type curing agent. These can be used alone or as a mixture of two or more. Of these, anionic or cationic polymerizable catalyst-type curing agents are preferred because they are excellent in rapid curability and do not require chemical equivalent considerations.

Examples of the anionic or cationic polymerizable catalyst-type curing agent include tertiary amine derivatives, imidazole derivatives, hydrazide compounds, boron trifluoride-amine complexes, onium salts (sulfonium salts, ammonium salts) amine imides, diaminomaleonitrile, Mention may be made of melamine and its derivatives, salts of polyamines, and dicyandiamide, and these modifications can also be used. Examples of the polyaddition type curing agent include polyamine, polymercaptan, polyphenol, and acid anhydride.
As the anionic or cationic polymerizable catalyst-type curing agent, specifically, a tertiary amine derivative or an imidazole derivative is preferably used in terms of adhesive strength, and an imidazole derivative is more preferably used.

As the curing agent, a latent curing agent is preferred because the active point of reaction initiation by thermocompression bonding is relatively clear and suitable for a connection method involving a thermocompression bonding process. Here, the latent curing agent is a substance that exhibits a curing function under certain specific conditions (such as temperature). Examples of the latent curing agent include those obtained by protecting a normal curing agent with microcapsules and the like, and those having a structure in which a curing agent and various compounds form a salt.
In such a latent curing agent, for example, when a specific temperature is exceeded, the curing agent is released from the microcapsule or salt into the system, and a curing function is exhibited.

Examples of the latent curing agent include a reaction product of an amine compound and an epoxy compound (amine-epoxy adduct system), a reaction product of an amine compound and an isocyanate compound or a urea compound (urea type adduct system), and the like. Commercial products of latent curing agents include Amicure (registered trademark, manufactured by Ajinomoto Co., Inc.), Novacure (registered trademark, manufactured by Asahi Kasei E-Materials Co., Ltd.) in which a microencapsulated amine is dispersed in a phenol resin, and the like. It is done.

The content of the curing agent in the connection material is not particularly limited, but from the viewpoint of adhesive strength, the content of the curing agent is 10% when the total content of the adhesive and the curing agent is 100% by mass. % To 50% by mass, more preferably 20% to 40% by mass.

(Film forming material)
Examples of the film forming material include phenoxy resin, acrylic rubber, polyimide resin, polyamide resin, polyurethane resin, polyester resin, polyester urethane resin, and polyvinyl butyral resin, and are preferably phenoxy resin or acrylic rubber.

The content of the film-forming material is not particularly limited, but from the viewpoint of the hardness of the produced connection material, ease of peeling from the release film described later, the adhesive, the curing agent, and the film-forming material. The content of the film-forming material is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 70% by mass or less when the total content is 100% by mass.

(Conductive particles)
The connection material can further contain conductive particles. By containing the conductive particles, the power generation performance of the solar cell module can be further improved.
The conductive particles are not particularly limited, and examples include gold particles, silver particles, copper particles, nickel particles, gold-plated nickel particles, gold / nickel-plated plastic particles, copper-plated particles, and nickel particles. . When conductive particles are contained, the particle diameter of the conductive particles is preferably 1 μm to 50 μm, more preferably 1 μm to 30 μm, and even more preferably 1 μm to 25 μm. In addition, the content of the conductive particles in the connection material is preferably 1% by volume or more and 15% by volume or less, preferably 2% by volume or more and 12% by volume or less, with the total volume of the connection material being 100% by volume from the viewpoint of conductivity. More preferably, it is not more than volume%, more preferably not less than 3 volume% and not more than 10 volume%.

(Other ingredients)
In addition to the components described above, the connection material may contain a modifying material such as a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent in order to improve adhesion or wettability. . Moreover, when adding electroconductive particle, in order to improve the dispersibility, a chelating material etc. for suppressing dispersing agents, such as calcium phosphate and a calcium carbonate, silver, or copper migration, etc. can be contained.

The connection material can be produced, for example, by applying a coating solution obtained by dissolving or dispersing the above-described various materials in a solvent onto a release film such as a polyethylene terephthalate film and removing the solvent.

<Wiring member>
The electrode connection set may include a wiring member as one of the elements.
The wiring member is not particularly limited, but a solder-coated copper wire (tab wire) for a solar cell can be suitably used. Examples of the solder composition include Sn—Pb, Sn—Pb—Ag, Sn—Ag—Cu, etc. In consideration of the influence on the environment, Sn—Ag—Cu based which does not substantially contain lead. It is preferable to use solder.

The thickness of the copper wire of the tab wire is not particularly limited, and 0.05 mm to 0 in view of the difference in thermal expansion coefficient or connection reliability with the solar cell element during the heating and pressing treatment and the resistivity of the tab wire itself. 0.5 mm, preferably 0.1 mm to 0.5 mm.

In addition, the cross-sectional shape of the tab wire is not particularly limited, and the cross-sectional shape can be any of a rectangle (flat wire) and an ellipse (round wire), and the copper-containing material of the connection material when the connection material is thermocompression bonded. From the viewpoint of penetration into the gap of the electrode, uniformity of pressure during thermocompression bonding, etc., it is preferable to use a rectangular (flat tab) cross-sectional shape.

Further, the total thickness of the tab wire is not particularly limited, and is preferably 0.1 mm to 0.7 mm, and preferably 0.15 mm to 0.5 mm, from the viewpoint of the uniformity of pressure during thermocompression bonding. More preferred.

[Method for manufacturing solar cell]
The manufacturing method of the solar cell of this invention forms an electrode using the said electrode connection set, and connects a wiring member to the obtained electrode.
That is, the manufacturing method of the solar cell includes a step of applying the electrode composition onto a semiconductor substrate having the pn junction (referred to as an electrode composition applying step), and a semiconductor to which the electrode composition is applied. A step of heat-treating the substrate to form a copper-containing electrode (referred to as an electrode forming step), and a step of laminating the connection material and the wiring member on the copper-containing electrode in this order to obtain a laminate (referred to as a lamination step). And a step of subjecting the laminate to a heat and pressure treatment (referred to as a heat and pressure treatment step).
The solar cell manufacturing method can manufacture a solar cell in which the electrode and the wiring member have high connection strength (adhesion) and high connection reliability.

(Solar cell element manufacturing process)
A solar cell element is obtained by the electrode composition applying step and the electrode forming step.

In the electrode composition application step, the electrode composition is applied to a region on the semiconductor substrate where the electrode is to be formed. Examples of a method for applying the electrode composition include screen printing, an ink jet method, and a dispenser method. From the viewpoint of productivity, application by screen printing is preferable.

When applying the electrode composition by screen printing, the electrode composition preferably has a viscosity in the range of 20 Pa · s to 1000 Pa · s. The viscosity of the electrode composition is measured using a Brookfield HBT viscometer at a temperature of 25 ° C. and a rotational speed of 5.0 rpm.

The application amount of the electrode composition can be appropriately selected according to the size of the copper-containing electrode to be formed. For example, the application amount of the electrode composition can be 2 g / m ² to 10 g / m ^2, and preferably 4 g / m ² to 8 g / m ² .

In the electrode forming step, the semiconductor substrate after application of the electrode composition is heat-treated after drying. Thereby, baking of the composition for electrodes is performed, a copper containing electrode is formed in the desired area | region on a semiconductor substrate, and a solar cell element can be obtained. By using the electrode composition, an electrode with low resistivity can be formed even when heat treatment (sometimes referred to as baking treatment) is performed in the presence of oxygen (for example, in the air).

As heat treatment conditions (firing conditions) for forming a copper-containing electrode on a semiconductor substrate using the electrode composition, commonly used heat treatment conditions can be applied.
Generally, the heat treatment temperature (firing temperature) is 800 ° C. to 900 ° C. However, when the electrode composition is used, it should be applied in a wide range from a lower temperature heat treatment condition to a general heat treatment condition. Can do. For example, an electrode having good characteristics can be formed at a wide range of heat treatment temperatures of 450 ° C. to 900 ° C.
The heat treatment time can be appropriately selected according to the heat treatment temperature and the like, and can be, for example, 1 second to 20 seconds.

As the heat treatment apparatus, any apparatus that can be heated to the above temperature can be used as appropriate, and examples thereof include an infrared heating furnace and a tunnel furnace. An infrared heating furnace is highly efficient because electric energy is directly input to a heating material in the form of electromagnetic waves and is converted into heat energy, and rapid heating is possible in a short time. Furthermore, since there is no product due to combustion and non-contact heating, contamination of the formed electrode can be suppressed. Since the tunnel furnace automatically and continuously conveys the sample from the entrance to the exit and fires it, it can be fired more uniformly by dividing the furnace body and controlling the transportation speed. From the viewpoint of the power generation performance of the solar cell element, it is preferable to perform heat treatment with a tunnel furnace.

Hereinafter, although the specific example of a solar cell element and its manufacturing method are demonstrated, referring drawings, this invention is not limited to this. Moreover, the magnitude | size of the member in each figure is notional, The relative relationship of the magnitude | size between members is not limited to this.
A sectional view showing an example of a typical solar cell element, and outlines of a light receiving surface and a back surface are shown in FIGS.
As shown in a schematic cross-sectional view in FIG. 1, an n ⁺ -type diffusion layer 2 is formed near the surface of one surface of the semiconductor substrate 1, and the light-receiving surface output extraction electrode 4 and the reflection are formed on the n ⁺ -type diffusion layer 2. A prevention film 3 is formed. A p ⁺ type diffusion layer 7 is formed in the vicinity of the surface of the other surface, and a back surface output extraction electrode 6 and a back surface current collecting electrode 5 are formed on the p ⁺ type diffusion layer 7. Usually, single crystal or polycrystalline silicon is used for the semiconductor substrate 1 of the solar cell element. This semiconductor substrate 1 contains boron or the like and constitutes a p-type semiconductor. Irregularities (also referred to as texture, not shown) are formed on the light receiving surface side by an etching solution containing NaOH and IPA (isopropyl alcohol) in order to suppress reflection of sunlight. Phosphorus or the like is diffused (doped) on the light receiving surface side, the n ⁺ diffusion layer 2 is provided with a thickness on the order of submicrons, and a pn junction is formed at the boundary with the p-type bulk portion. Further, on the light receiving surface side, an antireflection film 3 such as silicon nitride is provided on the n ⁺ type diffusion layer 2 with a film thickness of about 90 nm by PECVD or the like.

Next, the light receiving surface output extraction electrode 4 and the light receiving surface current collecting electrode 8 provided on the light receiving surface side schematically shown in FIG. 2, the back surface collecting electrode 5 formed on the back surface schematically shown in FIG. A method for forming the back surface output extraction electrode 6 will be described.
The light receiving surface output extraction electrode 4, the light receiving surface current collecting electrode 8, and the back surface output extraction electrode 6 are formed from the electrode composition. The back current collecting electrode 5 is formed of an aluminum electrode composition containing glass powder. As a first method for forming the light receiving surface output extraction electrode 4, the light receiving surface collecting electrode 8, the back surface output extracting electrode 6 and the back surface collecting electrode 5, the electrode composition and the aluminum electrode composition are used. For example, it may be formed by applying a desired pattern by screen printing or the like and then baking it at a temperature of about 750 ° C. to 900 ° C. in the air after drying.

At this time, on the light receiving surface side, the glass particles contained in the electrode composition forming the light receiving surface output extraction electrode 4 and the light receiving surface collecting electrode 8 react with the antireflection film 3 (fire-through). Then, the light receiving surface output extraction electrode 4 and the light receiving surface current collecting electrode 8 and the n ⁺ type diffusion layer 2 are electrically connected (ohmic contact).
In the present invention, by forming the light receiving surface output extraction electrode 4 and the light receiving surface current collecting electrode 8 using the electrode composition, copper is suppressed from being oxidized while containing copper as a conductive metal, A copper-containing electrode with low resistivity is formed with good productivity.
Further, it is preferable that the copper-containing electrode includes a Cu—Sn alloy phase and / or a Cu—Sn—Ni alloy phase and a Sn—PO glass phase, and the Sn—PO glass phase is Cu— More preferably (not shown) between the Sn alloy phase or the Cu—Sn—Ni alloy phase and the silicon substrate. Thereby, the reaction between copper and the silicon substrate is suppressed, and an electrode having a low resistivity and excellent adhesion can be formed.

On the back surface side, the aluminum in the aluminum electrode composition that forms the back current collecting electrode 5 during firing is diffused into the back surface of the semiconductor substrate 1 to form the p ⁺ -type diffusion layer 7. An ohmic contact can be obtained between the substrate 1 and the back surface collecting electrode 5 and the back surface output extraction electrode 6.

As a second method for forming the light receiving surface output extraction electrode 4, the light receiving surface current collecting electrode 8 and the back surface output extracting electrode 6, the aluminum electrode composition for forming the back surface collecting electrode 5 is first printed and dried. After firing at about 750 ° C. to 900 ° C. in the atmosphere to form the back current collecting electrode 5, the electrode composition is applied to the light receiving surface side and the back side, and after drying, about 450 ° C. to 650 ° C. in the air And a method of forming the light receiving surface output extraction electrode 4, the light receiving surface current collecting electrode 8 and the back surface output extraction electrode 6 by baking.

This method is effective in the following cases, for example. That is, when the aluminum electrode composition forming the back surface collecting electrode 5 is fired, at a firing temperature of 650 ° C. or less, depending on the composition of the aluminum electrode composition, the aluminum particles may be sintered and the semiconductor substrate 1 may be sintered. In some cases, the p ⁺ type diffusion layer cannot be sufficiently formed due to insufficient aluminum diffusion amount. In this state, an ohmic contact cannot be sufficiently formed between the semiconductor substrate 1 on the back surface, the back surface collecting electrode 5 and the back surface output extraction electrode 6, and the power generation performance as a solar cell element may be lowered. Therefore, after forming the back current collecting electrode 5 at an optimum firing temperature (for example, 750 ° C. to 900 ° C.) for the aluminum electrode composition, the electrode composition is applied, and after drying, a relatively low temperature (for example, 450 ° C.). It is preferable to form the light receiving surface output extraction electrode 4, the light receiving surface current collecting electrode 8 and the back surface output extraction electrode 6 by baking at ˜650 ° C.).
Regardless of which method is selected, the film thickness of the light-receiving surface current collecting electrode 8 and the back surface output extraction electrode 6 obtained after firing can be, for example, 3 μm to 50 μm, preferably 5 μm to 30 μm. . In addition, the film thickness of the layer or laminated body in this invention is taken as the value given as an arithmetic average value by measuring the thickness of five points of the target layer or laminated body. The film thickness of a layer or a laminated body shall be measured using the micrometer.

Further, as shown in the plan view of FIG. 3, the solar cell element can take a form in which the light receiving surface output extraction electrode 4 is not formed. The solar cell element shown in FIG. 3 can be manufactured in the same manner as the solar cell element having the structure shown in FIGS. This can be considered as follows, for example.

In the present invention, since the connection material is used, the object to which the wiring member is connected does not need solder wettability as described above. In the present invention, by using the connection material, the antireflection film 3 formed on the semiconductor substrate 1 and the wiring member can be firmly adhered. The electrical connection between the light receiving surface current collecting electrode 8 and the wiring member on the light receiving surface of the solar cell element is a portion where the light receiving surface current collecting electrode 8 and the wiring member are in direct contact with each other due to the flow exclusion of the connecting material. And when the connection material contains conductive particles, it is achieved by forming a portion where the light receiving surface current collecting electrode 8 and the wiring member are in contact via the conductive particles by thermocompression bonding. Is done.

(Solar cell manufacturing process)
Using the solar cell element obtained as described above, a solar cell including the solar cell element is further obtained by the laminating step and the heat and pressure treatment step.
More specifically, the solar cell of the present invention has a structure in which a conductive layer including a metal part including copper, a glass part, and a connection material is interposed between a semiconductor substrate and a wiring member. The conductive layer includes a structure in which the copper-containing electrode including the metal part and the glass part is in contact with the wiring member thereon, and a structure in which a part of the connection material enters the gap of the copper-containing electrode. . By having a structure in which the copper-containing electrode and the wiring member are in direct contact with each other, the connection reliability can be improved, and by having a structure in which a part of the connection material enters the void portion of the copper-containing electrode, Adhesion between the containing electrode and the wiring member is improved.

Next, specific examples of the solar cell of the present invention and a method for manufacturing the solar cell will be described with reference to FIGS. 5 to 7, but the present invention is not limited thereto. Moreover, the magnitude | size of the member in each figure is notional, The relative relationship of the magnitude | size between members is not limited to this.
As shown in FIGS. 5 to 7, the connection material 10 and the wiring member 9 are arranged in this order on the light receiving surface output extraction electrode 4 and the back surface output extraction electrode 6 to obtain a laminate (lamination process). By subjecting the laminated body to heat pressure treatment (thermocompression treatment), the light receiving surface output extraction electrode 4 and the wiring member 9 are pressure bonded, and the back surface output extraction electrode 6 and the wiring member 9 are pressure bonded to form a solar cell. Is done. When connecting a plurality of the solar cells, the wiring member 9 has a light receiving surface output extraction electrode 4 of one solar cell element at one end and a back surface output extraction electrode 6 of another solar cell element at the other end, respectively. 9 may be arranged so as to be connected via 9. In the case of manufacturing a solar cell, a solar cell element in which the light receiving surface output extraction electrode 4 is not formed can be used as shown in FIG.

Moreover, when manufacturing the solar cell of this invention, the heat press treatment conditions normally used in the said technical field can be applied as conditions for carrying out the thermocompression bonding of the said electrode and wiring member.
In general, the heating temperature is preferably 150 ° C. or higher and 200 ° C. or lower, and more preferably 150 ° C. or higher and 190 ° C. or lower. The pressure during pressure bonding is preferably 0.1 MPa or more and 4.0 MPa or less, and more preferably 0.5 MPa or more and 3.5 MPa or less. The heating and pressing time is preferably 3 seconds or more and 30 seconds or less, and more preferably 4 seconds or more and 20 seconds or less. By performing the heating and pressurizing treatment under the above conditions, the connection material can easily enter the gap of the copper-containing electrode, the adhesive force between the electrode and the wiring member is improved, and the connection material is efficiently eliminated. This facilitates direct contact between the electrode and the wiring member, and as a result, the electrical contact resistance between the electrode and the wiring member can be reduced. The direction of pressurization may be any direction as long as pressure is applied at least in the stacking direction of the electrode and the wiring member to bond the electrode and the wiring member.

As the thermocompression bonding apparatus, any apparatus capable of applying the above temperature and pressure can be used as appropriate. For example, a thermocompression bonding machine including a pressure bonding head having a heating mechanism can be suitably used. In this case, it is particularly preferable that the pressure of the pressure-bonding head ((target pressure) × (adhesion area)) can be appropriately set from the target pressure and the adhesion area.

[Structure of solar cell]
A solar cell manufactured using the electrode connection set includes a semiconductor substrate, an electrode formed on the semiconductor substrate, and a wiring member disposed on the electrode. The electrode includes a metal part and glass. And a portion corresponding to a void formed by firing during electrode formation. The solar cell has a partial structure in which a conductive layer including a metal part, a glass part and a connection material and a wiring member are stacked on a semiconductor substrate as a wiring connection part.
Due to the firing at the time of electrode formation, voids in the copper-containing electrode are generated irregularly and in an arbitrary shape, and the contour of the metal part constituting the electrode becomes an uneven shape due to the formation of the voids. At the time of thermocompression bonding between the electrode and the wiring member, the connection material enters the gap from the connection material application surface, that is, the wiring member side. As a result, a conductive layer including a metal part, a glass part, and a connection material that has entered a part corresponding to the gap is formed between the semiconductor substrate and the wiring member in the wiring connection part. In the conductive layer, the connection material penetrates into the gap.

In such a solar cell, for example, when the cross section in the stacking direction of the semiconductor substrate, the conductive layer, and the wiring member is observed, the boundary line between the electrode and the connection material is irregularly bent (see FIG. 8). ). The presence of the boundary line between the electrode and the connection material exhibiting the irregular bending state can be confirmed using, for example, a cross section (observation cross section) parallel to the stacking direction of the semiconductor substrate, the conductive layer, and the wiring member. .

The observation cross section applied to confirm the shape inside the conductive layer is the two sides along the direction parallel to the stacking direction of the semiconductor substrate, conductive layer and wiring member, and the stacking direction of the semiconductor substrate, conductive layer and wiring member. And a rectangular shape surrounded by two sides along the vertical direction. In this observation cross section, the length of the side in the direction parallel to the stacking direction of the semiconductor substrate, the conductive layer, and the wiring member is “height”, and the direction perpendicular to the stacking direction of the semiconductor substrate, the conductive layer, and the wiring member is The length is “width”. The observation cross section only needs to include at least a conductive layer and at least a part of each of the wiring member and the semiconductor substrate sandwiching the conductive layer.

The size of the observation cross section varies depending on the size of the solar cell. For example, the width is set to 100 μm to 500 μm, and the height is set to an arbitrary length larger than the thickness of the conductive layer, for example, 50 μm to 500 μm. it can. In addition, the observation cross section is not particularly limited as long as it is an observation cross section at the wiring connection portion, and is an observation cross section (for example, the area of the conductive layer in the observation cross section where the end portion of the solar cell or the connection material is extremely small or extremely large) On the other hand, it is preferable to exclude the area of the connecting material from 2% or less or 98% or more from the confirmation target.
When such an observation cross section is used, the shape of the copper-containing electrode in the wiring connection portion can be confirmed as follows.

In the observation cross section of the wiring connection portion, the total boundary line length including the total boundary line between the electrode and the connection material and the total boundary line between the electrode and the wiring member is the length of the width of the observation cross section. It can be confirmed by being longer than the length L (FIG. 8).

Further, in the observation cross section of the wiring connection portion, a line segment from a boundary line between the wiring member and the conductive layer to a glass portion or a metal portion that first contacts is drawn in a direction parallel to the height direction of the observation cross section. Can be confirmed by obtaining a plurality of line segments having different lengths (for example, line segment D1 and line segment D2 in FIG. 8).

Moreover, in the said wiring connection part, you may have a part which the electrode is in contact with the wiring member (FIG. 8, frame C). Such a portion where the electrode and the wiring member are in contact with each other is considered to be obtained by removing the connecting material from between the electrode and the wiring member by heat and pressure treatment. In the portion where the electrode and the wiring member are in direct contact with each other, the electrode and the wiring member are in a good connection state, so that the wiring member and the electrode can be electrically connected.
If there is a part where the electrode and the wiring member are in direct contact, the shape of the electrode can be determined by comparing the total length of the boundary line between the electrode and the connecting material or wiring member and the length in the width direction of the observation cross section. It is preferable to confirm.

In the solar cell according to the present invention, the irregular uneven state of the boundary surface between the electrode and the resin part that provides good connection strength between the electrode and the wiring member may be specified by the surface roughness of the electrode.
In this case, the arithmetic average roughness Ra of the electrode surface is preferably 0.8 or more and 6.3 or less. The arithmetic average roughness Ra can be obtained by measuring by the method described in JIS B 0601-2001. Specifically, the surface of the electrode formed on the semiconductor substrate was or was laminated on the surface of the electrode formed on the semiconductor substrate using a surface shape measuring instrument (Mitutoyo Corporation, trade name: Form Tracer SV-C3000, etc.). After removing the wiring member and the resin portion, the arithmetic average roughness Ra can be directly measured.

[Solar cell module]
The solar cell module of the present invention includes a solar cell obtained using the electrode connection set, and a sealing material that seals the solar cell by exposing a part of the wiring member in the solar cell. I have it.
In the solar cell module, for example, a plurality of the solar cells are connected in series and / or in parallel as necessary, sandwiched with tempered glass or the like for environmental resistance, the gap is filled with a transparent resin, and exposed. The thing provided with the wiring member made as an external terminal is included.

As a manufacturing method of a solar cell module, for example, as shown in FIG. 9, a glass plate 11, a sealing material 12, a solar cell 14 provided with a wiring member 9, a sealing material 12, and a back sheet 13 are used. A general method including a sealing step that is arranged in this order and is sealed with a vacuum laminator or the like can be suitably used. Lamination conditions are determined depending on the type of sealing material, but are preferably maintained at 130 ° C. to 160 ° C. for 3 minutes or more, more preferably 135 ° C. to 150 ° C. for 3 minutes or more.

Examples of the glass plate 11 include white plate tempered glass with dimples for solar cells. Examples of the sealing material 12 include an EVA sheet made of ethylene vinyl acetate (EVA). Examples of the back sheet 13 include polyethylene terephthalate (PET) -based or Tedlar-PET laminated material, metal foil-PET laminated material, and the like.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these embodiments.

<Example 1>
(A) Preparation of electrode composition A phosphorus-containing copper alloy containing 7% by mass of phosphorus was prepared by a conventional method, dissolved and powdered by a water atomization method, and then dried and classified. The classified powders were blended, deoxygenated and dehydrated to produce phosphorus-containing copper alloy particles containing 7% by mass of phosphorus. The phosphorus-containing copper alloy particles had a particle size (D50%) of 5.0 μm and a substantially spherical shape.

Silicon _(SiO 2) 3 parts by weight dioxide, lead oxide (PbO) 60 parts by mass, 18 parts by weight of boron oxide _(B ₂ O 3), bismuth oxide _(Bi _{2 O} 3) 5 parts by weight, aluminum oxide _(Al 2 _{O 3} ) A glass composed of 5 parts by mass and 9 parts by mass of zinc oxide (ZnO) (hereinafter sometimes abbreviated as “G01”) was prepared. The obtained glass G01 had a softening temperature of 420 ° C. and a crystallization start temperature of over 650 ° C.
By using the obtained glass G01, glass G01 particles having a particle diameter (D50%) of 2.5 μm were obtained. The shape was substantially spherical.

The shapes of the phosphorus-containing copper alloy particles and the glass particles were determined by observing with a TM-1000 scanning electron microscope manufactured by Hitachi High-Technologies Corporation. The particle diameters of the phosphorus-containing copper alloy particles and the glass particles were calculated using an LS 13 320 type laser scattering diffraction particle size distribution analyzer (measurement wavelength: 630 nm, Beckman Coulter, Inc.). The softening temperature and the crystallization start temperature of the glass were obtained from a differential heat (DTA) curve using a DTG-60H type differential thermal-thermogravimetric simultaneous measuring device manufactured by Shimadzu Corporation.

33.3 parts by mass of the phosphorus-containing copper alloy particles obtained above, 22.8 parts by mass of tin particles (Sn; particle diameter (D50%) is 5.0 μm; purity 99.9% by mass), nickel particles ( Ni; particle size (D50%) is 5.0 μm: purity 99.9% by mass) 22.2 parts by mass, glass G01 particles are 7.8 parts by mass, diethylene glycol monobutyl ether (BC) is 11.7 parts by mass, 2.2 parts by mass of polyethyl acrylate (EPA) was mixed and mixed using an automatic mortar kneader to prepare a paste, thereby preparing an electrode composition 1. When the viscosity of the obtained composition 1 for electrodes was measured on the conditions of the temperature of 25 degreeC, and rotation speed 5.0rpm using the Brookfield HBT viscometer, it was 31 Pa.s.

(B) Preparation of connecting material Acrylic rubber obtained by copolymerizing 40 parts by mass of butyl acrylate, 30 parts by mass of ethyl acrylate, 30 parts by mass of acrylonitrile, and 3 parts by mass of glycidyl methacrylate (product name: KS8200H, Hitachi Chemical Co., Ltd.) 125 g of company, weight average molecular weight: 850,000) and 50 g of phenoxy resin (product name: PKHC, Union Carbide, weight average molecular weight 45,000) are dissolved in 400 g of ethyl acetate to obtain a 30% by mass solution. It was. Next, 325 g of a liquid epoxy resin (Novacure HX-3941HP, Asahi Kasei E-Materials Co., Ltd., epoxy equivalent 185) containing a microcapsule-type latent curing agent was added to this solution and stirred to obtain an adhesive composition. . Furthermore, 56 g of nickel particles (Fukuda Metal Foil Powder Co., Ltd.) having a diameter of about 10 μm were added to this adhesive composition and stirred.

The adhesive composition obtained above is applied onto a polyethylene terephthalate film using an applicator (manufactured by YOSHIMITSU), and dried on a hot plate at a temperature of 70 ° C. for 10 minutes. A connection material 1 of 25 μm was produced. The film thickness of the connecting material was measured using a micrometer (Mitutoyo Corp, ID-C112). The viscosity of the connecting material 1 was 9800 Pa · s when measured under the conditions of 25 ° C. and a frequency of 10 Hz using a shear viscometer (ARES) manufactured by Rheometric.

(C) Production of Solar Cell Element The electrode composition 1 and the connection material 1 obtained in the above (a) and (b) were prepared as an electrode connection set.
Further, in addition to the electrode connection set, as a wiring member, a solder-plated rectangular wire for a solar cell (product name: SSA-TPS L 0.2 × 1.5 (10), thickness 0.2 mm × width 1.5 mm) Hitachi Metals Co., Ltd., which has a specification in which a Sn—Ag—Cu-based lead-free solder is plated to a thickness of 10 μm on one side, was prepared on a copper wire.
Using these, solar cell elements were produced as follows.

First, a p-type silicon substrate having a thickness of 190 μm in which an n ⁺ -type diffusion layer, a texture, and an antireflection film (silicon nitride film) were formed on the light receiving surface was prepared, and two pieces were cut into a size of 125 mm × 125 mm. On the light receiving surface, the electrode composition 1 was printed using a screen printing method so as to form an electrode pattern as shown in FIG. The electrode pattern is composed of a light receiving surface collecting electrode having a width of 150 μm and a light receiving surface output extraction electrode having a width of 1.5 mm, and the film thickness of each of the light receiving surface collecting electrode and the light receiving surface output extraction electrode after firing is 20 μm. The printing conditions (screen plate mesh, printing speed, printing pressure) were adjusted as appropriate. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.

Subsequently, on the surface opposite to the light-receiving surface (hereinafter also referred to as “back surface”), the electrode composition 1 as the electrode composition and the paste-like aluminum electrode composition are screened in the same manner as described above. Printing was performed so as to obtain an electrode pattern as shown in FIG.
The pattern of the back surface output extraction electrode made of the electrode composition 1 was composed of 123 mm × 5 mm, and was printed in two places in total. In addition, the printing conditions (screen plate mesh, printing speed, printing pressure) were appropriately adjusted so that the back surface output extraction electrode had a film thickness after firing of 20 μm. Moreover, the composition for aluminum electrodes was printed on the whole surface except the back surface output extraction electrode, and the back surface current collection electrode pattern was formed. Moreover, the printing conditions of the composition for aluminum electrodes were appropriately adjusted so that the film thickness of the back surface collecting electrode after firing was 20 μm. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.

Subsequently, using a tunnel furnace (Noritake Co., Ltd., one-row transport W / B tunnel furnace), a heat treatment (firing) is performed in an air atmosphere at a firing maximum temperature of 800 ° C. and a holding time of 10 seconds. Two solar cell elements 1 on which electrodes were formed (one for peel strength evaluation and one for power generation performance evaluation) were produced.

The connection material 1 is cut into the width (1.5 mm) of the light receiving surface output extraction electrode of the solar cell element 1, and between the prepared wiring member and the light receiving surface output extraction electrode and the back surface output extraction electrode of the solar cell element 1. In each, the cut connection material 1 was disposed. Next, using a thermocompression bonding machine (device name: MB-200WH, Hitachi Chemical Co., Ltd.), thermocompression bonding is performed at 180 ° C., 2 MPa, 10 seconds, and the electrode and the wiring member are connected via the connection material 1. Two solar cells 1 having the above structure were produced.

(D) Production of solar cell module About one of the obtained solar cells 1 (one for power generation performance evaluation), tempered glass (product name: white plate tempered glass 3KWE33, manufactured by AGC), ethylene vinyl acetate ( EVA), using a back sheet, as shown in FIG. 9, glass (glass plate 11) / EVA (sealing material 12) / solar cell 1 (solar cell 14) / EVA (sealing material 12) / back sheet (Back sheet 13) is laminated in this order, and this laminate is heated to 140 ° C. using a vacuum laminator (device name: LM-50 × 50, NPC Corporation) so that a part of the wiring member is exposed. Was laminated in a vacuum for 5 minutes to produce a solar cell module 1.

(E) Sectional shape of solar cell Solar cell element 1 was obtained by using a RCO-961 type diamond cutter (Refinetech Co., Ltd.) as a part (wiring connection part) to which the wiring member of solar cell 1 obtained was connected. And parallel to the stacking direction of the wiring member. An SEM photograph of the obtained cross section was obtained using an SEM (Hitachi High-Technologies Corporation, TM-1000 scanning electron microscope).
The observation cross section has a rectangular shape of 300 μm × 250 μm with the length in the cutting direction as the height and the length in the direction parallel to the cutting direction as the width, and the connection material in the wiring connection portion is 2% or less in area ratio Or, those not exceeding 98% were selected as observation cross sections.
In the observation cross section, the total length of the boundary line between the connecting material and the metal part or the glass part was measured using Adobe illuminator CS6. Measurements were performed at an magnification of about 10,000 times the actual sectional view. The line segment corresponding to the length of the boundary line was traced with the “pencil tool” and the length was measured by using the “object tool”. The width of the observation cross section was measured by drawing a straight line having the same length as the width of the observation cross section with the “Line Tool” and using the “Object Tool”. The lengths of the line segment corresponding to the obtained boundary line length and the line segment corresponding to the width of the observation cross section were compared.

In addition, about the composition of the composition 1 for electrodes, it shows in Table 1 about the structure of the solar cell 1 and the solar cell module 1, respectively. The same applies hereinafter.
In Table 2, “◯” in the column “Applied electrode” means that the target electrode is used, and “-” means that the target electrode is not used. To do. “-” In the other columns means that there is no corresponding item.

<Examples 2 to 6>
In Example 1, phosphorus content of phosphorus-containing copper alloy particles, particle diameter (D50%) and its content, composition of tin-containing particles, particle diameter (D50%) and its content, composition of nickel-containing particles, particles As shown in Table 1, the diameter (D50%) and its content, the type of glass particles, the particle size (D50%) and its content, the type of solvent and its content, the type of resin and its content are changed. Except for the above, electrode compositions 2 to 6 were prepared in the same manner as electrode composition 1, respectively.
Glass G02 is composed of 45 parts by mass of vanadium oxide (V ₂ O ₅ ), 24.2 parts by mass of phosphorus oxide (P ₂ O ₅ ), 20.8 parts by mass of barium oxide (BaO), and antimony oxide (Sb ₂ O ₃ ). 5 parts by mass and 5 parts by mass of tungsten oxide (WO ₃ ) were prepared. The softening temperature of this glass G02 was 492 ° C., and the crystallization start temperature exceeded 650 ° C. The solvent Ter in the table represents terpineol, and the resin EC represents ethyl cellulose.

Next, solar cell elements 2 to 6 were obtained in the same manner as in Example 1 except that the obtained electrode compositions 2 to 6 were used and the firing conditions (maximum temperature and holding time) were changed to the conditions shown in Table 2. 6. Solar cells 2 to 6 and solar cell modules 2 to 6 were produced, respectively.

<Example 7>
In Example 1, the electrode composition 1 was applied to form the light receiving surface current collecting electrode and the light receiving surface output extraction electrode, and the back surface output extraction electrode was formed as follows. Except having applied the electrode composition 7, it carried out similarly to Example 1, and produced the solar cell element 7, the solar cell 7, and the solar cell module 7, respectively.

The electrode composition 7 was prepared in the same manner as the electrode composition 1 except that the composition of the glass particles was changed from the glass G01 to the glass G03 shown below.
Glass G03 is composed of 13 parts by mass of silicon dioxide (SiO ₂ ), 58 parts by mass of boron oxide (B ₂ O ₃ ), 38 parts by mass of zinc oxide (ZnO), 12 parts by mass of aluminum oxide (Al ₂ O ₃ ), and barium oxide. (BaO) It prepared so that it might consist of 12 mass parts. The obtained glass G03 had a softening temperature of 583 ° C. and a crystallization start temperature of over 650 ° C.

<Example 8>
In Example 7, a solar cell element 8, a solar cell 8, and a solar cell were formed in the same manner as in Example 7 except that the electrode composition 8 shown below was applied in order to form the back surface output extraction electrode. Modules 8 were produced respectively.

The electrode composition 8 is composed of 40.9 parts by mass of phosphorus-containing copper alloy particles (phosphorus content is 8% by mass; particle size (D50%) is 5.0 μm) and tin particles (Sn; particle size (D50%)). Is 59.8 parts by weight, Ni-6Cu-20Zn particles (particle size (D50% is 5.0 μm) is 13.6 parts by weight), glass G03 particles are 6.8 parts by weight, diethylene glycol monobutyl ether It was prepared by mixing 19.0 parts by mass of (BC) and 6.0 parts by mass of polyethyl acrylate (EPA) and mixing them using an automatic mortar kneader to form a paste.

<Example 9>
A p-type silicon substrate having a thickness of 190 μm having an n ⁺ -type diffusion layer, a texture, and an antireflection film (silicon nitride) formed on the light-receiving surface was prepared, and two pieces were cut into a size of 125 mm × 125 mm. Thereafter, an aluminum electrode paste was printed on the back surface to form a back surface collecting electrode pattern. The back surface collecting electrode pattern was printed on the entire surface other than the back surface output extraction electrode as shown in FIG. Moreover, the printing conditions of the aluminum electrode composition were appropriately adjusted so that the film thickness of the back surface collecting electrode after firing was 30 μm. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.
Subsequently, using a tunnel furnace (Noritake Co., Ltd., single-row transport W / B tunnel furnace), heat treatment (firing) is performed at a firing maximum temperature of 800 ° C. and a holding time of 10 seconds in an air atmosphere. A power electrode and a p ⁺ -type diffusion layer were formed.

Thereafter, the electrode composition 1 obtained as described above was printed in a pattern of the light receiving surface current collecting electrode, the light receiving surface output extraction electrode and the back surface output extraction electrode shown in FIGS. The electrode pattern is composed of a 150 μm wide light receiving surface current collecting electrode and a 1.5 mm wide light receiving surface output extraction electrode, and printing conditions (screen plate mesh, printing speed so that the film thickness after firing is 20 μm, respectively. , Printing pressure) was appropriately adjusted. The pattern of the back surface output extraction electrode was 123 mm × 5 mm, and was printed in two places in total. The printing conditions (screen plate mesh, printing speed, printing pressure) were appropriately adjusted so that the film thickness after firing was 20 μm. This was placed in an oven heated to 150 ° C., and the solvent was removed by evaporation.

Next, using a tunnel furnace (Noritake Co., Ltd., one-row transport W / B tunnel furnace), heat treatment (firing) is performed in an air atmosphere at a firing maximum temperature of 650 ° C. and a holding time of 15 seconds to obtain a desired electrode. Two solar cell elements 9 having the above were formed. Thereafter, in the same manner as in Example 1, a solar cell 9 and a solar cell module 9 were produced.

<Example 10>
In Example 9, except that the electrode composition for forming the light receiving surface current collecting electrode, the light receiving surface output extraction electrode and the back surface output extraction electrode was changed to the electrode composition 9 as shown in Table 1. In the same manner as in Example 9, two solar cell elements 10 were produced. Thereafter, in the same manner as in Example 9, a solar cell 10 and a solar cell module 10 were produced.

<Example 11>
In Example 1, a solder-plated rectangular wire for solar cells (product name: SSA-TPS 0.2 × 1.5 (40), thickness 0.2 mm × width 1.5 mm), Sn— A solar cell 11 and a solar cell module in the same manner as in Example 1 except that an Ag-Cu-based lead-free solder having a thickness of 40 μm plated on one side and using Hitachi Metals Co., Ltd. was used. 11 was produced.

<Example 12>
In Example 1, the solar cell 12 and the solar cell module 12 were produced in the same manner as in Example 1 except that the thermocompression bonding conditions were changed to 170 ° C., 2 MPa, and 20 seconds.

<Example 13>
In Example 1, the solar cell 13 and the solar cell module 13 were produced in the same manner as in Example 1 except that the thermocompression bonding conditions were changed to 190 ° C., 1.5 MPa, and 10 seconds.

<Example 14>
In Example 1, the solar cell 14 and the solar cell module 14 were produced in the same manner as in Example 1 except that the connection material was changed from the connection material 1 to the connection material 2. The connection material 2 was produced in the same manner as the connection material 1 except that it did not contain Ni particles as conductive particles. The viscosity of the connecting material 2 was 9500 Pa · s as measured in the same manner as the connecting material 1.

<Example 15>
In Example 1, the solar cell 15 and the solar cell module 15 were formed in the same manner as in Example 1 except that the light receiving surface output extraction electrode was not formed and a light receiving surface electrode pattern as shown in FIG. 3 was applied. Produced.

<Example 16>
In Example 14, the solar cell 16 and the solar cell module 16 were formed in the same manner as in Example 14 except that the light receiving surface output extraction electrode was not formed and a light receiving surface electrode pattern as shown in FIG. 3 was applied. Produced.

<Example 17>
In Example 1, phosphorus content of phosphorus-containing copper alloy particles, particle diameter (D50%) and its content, composition of tin-containing particles, particle diameter (D50%) and its content, composition of nickel-containing particles, particles The electrode composition was the same as the electrode composition 1 except that the diameter (D50%) and its content, the type and content of the solvent, the type and content of the resin were changed as shown in Table 1. Product 10 was prepared. Three solar cell elements 17 were produced in the same manner as in Example 1 except that the electrode composition 10 was used. Thereafter, in the same manner as in Example 1, a solar cell 17 and a solar cell module 17 were produced.
Glass G04 was prepared so as to consist of 12.8 parts by mass of boron oxide, 8.7 parts by mass of silicon dioxide, and 78.5 parts by mass of bismuth oxide. The softening temperature of this glass G04 was 451 ° C., and the crystallization start temperature exceeded 650 ° C.

<Comparative Example 1>
In the production of the solar cell in Example 1, the solar cell C1 and the solar cell were obtained in the same manner as in Example 1 except that solder melting was used to connect the light receiving surface output extraction electrode and the back surface output extraction electrode to the wiring member. Battery module C1 was produced. Specifically, flux (product name: Deltalux, Senju Metal Industry Co., Ltd.) is applied to the electrode surface of the solar cell element 1, and then Sn—Ag—Cu based lead-free solder is melted at a temperature of 240 ° C. The wiring member was arranged and connected.

<Comparative example 2>
In preparing the electrode composition in Example 1, as shown in Table 1, an electrode composition C2 using silver particles was prepared without using phosphorus-containing copper alloy particles, tin-containing particles and nickel-containing particles. . Except having used the composition C2 for electrodes, it carried out similarly to Example 1, and produced the solar cell element C2, the solar cell C2, and the solar cell module C2.

<Comparative Example 3>
In the production of the solar cell in Example 1, the solar cell was formed in the same manner as in Example 1 except that the following conductive paste was used to connect the light receiving surface output extraction electrode and the back surface output extraction electrode to the wiring member. Battery C3 and solar cell module C3 were produced.
Specifically, 78.0 parts by mass of silver particles (Ag; particle diameter (D50%) is 3.0 μm; purity 99.8% by mass), 3.5 parts by mass of polyethylenedioxythiophene, and 1 epoxy resin .2 parts by mass and 17.3 parts by mass of N-methyl-2-pyrrolidone (NMP) were mixed together and mixed using an automatic mortar kneader to form a paste, thereby preparing a conductive paste. Next, the conductive paste is applied to the electrode surface of the solar cell element, and a wiring member (SSA-TPS L 0.2 × 1.5 (10)) is disposed thereon, which is placed at a temperature of 150 ° C. for 15 minutes. The conductive paste was cured by heating, and the solar cell element electrode and the wiring member were connected.

<Comparative example 4>
In Example 1, without using glass particles, the phosphorus content of the phosphorus-containing copper alloy particles, the particle diameter (D50%) and the content thereof, the composition of the tin-containing particles, the particle diameter (D50%) and the content thereof, Example 1 except that the composition of the nickel-containing particles, the particle diameter (D50%) and the content thereof, the type of the solvent and the content thereof, the type of the resin and the content thereof were changed as shown in Table 1. Similarly, an electrode composition C1 was prepared.

Then, using the obtained electrode composition C1, a solar cell element C4, a solar cell C4, and a solar cell module C4 were respectively produced in the same manner as in Example 1.

<Comparative Example 5>
In Example 1, without using tin-containing particles, the phosphorus content of the phosphorus-containing copper alloy particles, the particle size (D50%) and the content thereof, the composition of the nickel-containing particles, the particle size (D50%) and the content thereof Example 1 except that the types of glass particles, the particle diameter (D50%) and the content thereof, the types of the solvent and the content thereof, the types of the resin and the content thereof were changed as shown in Table 1. Similarly, an electrode composition C3 was prepared.

Next, using the obtained electrode composition C3, a solar cell element C5, a solar cell C5, and a solar cell module C5 were produced in the same manner as in Example 1.
In Table 1, “part” represents “part by mass”.

<Evaluation>
(Peel strength)
For one of the produced solar cells, the peel strength of the wiring member connected to the light receiving surface output extraction electrode and the back surface output extraction electrode was measured. The peel strength of the wiring member was measured by using a desktop peel tester (device name: EZ-S, manufactured by Shimadzu Corporation) and measuring the 90 ° peel adhesion strength of the wiring member. The measurement was performed in accordance with JIS K 6854-1; Adhesive-peeling adhesion strength test method, and the tensile speed of the wiring member was 50 mm / min and the tensile distance of the wiring member was 100 mm. For each test, a wiring member tensile distance-test force curve was plotted, and the average value of the test force at tensile distances of 10 mm, 20 mm, 30 mm, 40 mm, and 50 mm was taken as the peel adhesion strength. The obtained values are converted into relative values with the measured value of Comparative Example 1 (solar cell C1) as 100.0 and are shown in Table 3.

(Power generation performance)
Moreover, about another one of the produced solar cells, a solar cell module was produced as described above, and the power generation performance was evaluated. Evaluation is made with simulated sunlight (device name: WXS-155S-10, manufactured by Wacom Denso) and voltage-current (IV) evaluation measuring device (device name: IV CURVE TRACER MP-160, EKO INSTRUMENT. The measurement device of the company) was combined. Jsc (short-circuit current), Voc (open circuit voltage), FF (fill factor), and Eff (conversion efficiency), which indicate power generation performance as a solar cell, are measured in accordance with JIS-C-8913 and JIS-C-8914, respectively. Is obtained. Each obtained measurement value was converted into a relative value with the measurement value of Comparative Example 1 (solar cell module C1) as 100.0, and is shown in Table 3.

The peel strength of the wiring member in the solar cells produced in Examples 1 to 17 was higher than the measured value of Comparative Example 1. This is probably because the connecting material efficiently enters the void portion of the copper-containing electrode formed in the present invention, and the mechanical adhesive strength is improved by the anchor effect. On the other hand, for Comparative Example 2, it was found that the peel strength of the wiring member was lower than the measured value of Comparative Example 1. This is considered to be because the formed electrode contained almost no void portion and a sufficient anchor effect by the adhesive was not obtained.

Also in Comparative Example 3, the peel strength of the wiring member was lower than the measured value of Comparative Example 1. This is probably because the electrode and the wiring member are connected with a conductive paste, and the conductive particles in the conductive paste are insufficiently sintered, so that the mechanical strength cannot be maintained. For the same reason, since a large amount of contact resistance component between the conductive particles is contained, the resistivity at the wiring connection portion also increases, and as a result, it is considered that the power generation performance is lowered.

Further, the power generation performance of the solar cell modules produced in Examples 1 to 17 was almost the same as the measured value of Comparative Example 1. In particular, the solar cell modules 15 and 16 exhibited high power generation performance even though the light receiving surface output extraction electrode was not formed. From this, the adhesive is flow-excluded by thermocompression bonding, and the wiring member has a portion that is in direct contact with not only the light receiving surface and the back surface output extraction electrode, but also the light receiving surface current collecting electrode. It is considered that conductivity is obtained.

Moreover, in the observation cross section as a cross section parallel to the stacking direction of the wiring connection portion of the solar cell manufactured in Example 1, the electrode having a nonuniform shape is irregularly arranged on the silicon substrate, and the connection material and the electrode The boundary line was irregularly bent in the width direction of the observation cross section according to the contour of the electrode having an uneven shape. The total length of this boundary line was longer than the width of the observation cross section. The same applies to Examples 2 to 17.

In Comparative Example 4 and Comparative Example 5, the peel strength of the wiring member and the power generation performance of the solar cell module were both lower than the measured values of Example 1. From this, it is understood that tin-containing particles and glass particles are indispensable as electrode compositions for any properties.

Claims

An electrode composition comprising phosphorus-containing copper alloy particles, tin-containing particles, glass particles and a dispersion medium;
A connection material including an adhesive;
Including electrode connection set.
The electrode connection set according to claim 1, wherein the electrode composition further contains nickel particles.
The electrode connection set according to claim 1 or 2, wherein the connection material further includes a curing agent and a film forming material.
The electrode connection set according to any one of claims 1 to 3, wherein the connection material further includes conductive particles.
Applying the electrode composition onto a semiconductor substrate having a pn junction;
Heat-treating the semiconductor substrate provided with the electrode composition to form a copper-containing electrode;
Laminating the connection material and the wiring member in this order on the copper-containing electrode, and obtaining a laminate,
A step of heating and pressurizing the laminate,
A solar cell manufacturing method for manufacturing a solar cell using the electrode connection set according to any one of claims 1 to 4.
The method for manufacturing a solar cell according to claim 5, wherein the heat treatment is performed at 450 ° C to 900 ° C.
A solar cell obtained by the production method according to claim 5 or 6.
A solar cell obtained by the manufacturing method according to claim 5 or 6,
A sealing material that seals the solar cell so that a part of the wiring member in the solar cell is exposed;
A solar cell module.