WO2015115566A1

WO2015115566A1 - Electrode connection set, method for manufacturing solar cell, solar cell and solar cell module

Info

Publication number: WO2015115566A1
Application number: PCT/JP2015/052573
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: 2014-01-31
Filing date: 2015-01-29
Publication date: 2015-08-06
Also published as: TW201547043A

Abstract

　Provided is an electrode connection set comprising: an electrode composition containing phosphorus- and tin- containing copper alloy particles and glass particles; and an adhesive-containing connection material. Also provided are a method for manufacturing a solar cell using said electrode connection set, a solar cell, and a solar cell module.

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, a solar cell, and a solar cell module.

Generally, electrodes are formed on a light receiving surface and a back surface of a solar cell element provided with a semiconductor substrate such as a silicon substrate. In order to efficiently extract the electric energy converted in the solar cell element by the incidence of light to the outside, the electrode has a sufficiently low volume resistivity (hereinafter also simply referred to as “resistivity”), and the electrode However, it is necessary to form a good ohmic contact with the semiconductor substrate.

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. When an electrode is formed using a p-type silicon substrate which is a kind of semiconductor substrate, texture (unevenness) is formed on the light-receiving surface side of the p-type silicon substrate, and then phosphorus or the like is thermally heated at a high temperature. An electrode composition (sometimes referred to as an electrode paste composition) is applied onto the n ⁺ -type diffusion layer formed by diffusing on the surface by screen printing or the like, and this is applied in the atmosphere at 800 ° C to An electrode is formed by baking at 900 ° C. The electrode composition forming these electrodes contains conductive metal powder, glass particles, various additives and the like.

Silver particles are generally used as the conductive metal powder other than the back surface collecting electrode among the electrodes. The silver particles have a low resistivity of 1.6 × 10 ⁻⁶ Ω · cm, the silver particles are self-reduced and sintered under the above firing conditions, and have good ohmic contact with the semiconductor substrate. There is an advantage that (electrical connection) can be formed.

As shown above, an electrode formed from a composition for an electrode 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 JP-A-2005-314755 and JP-A-2004-217952, in order to solve the above-mentioned problems of copper, oxidation resistance is imparted to copper using various methods, and high-temperature firing is performed. Copper particles that are difficult to oxidize have been reported. Japanese Patent Application Laid-Open No. 2011-171272 also reports a method of using an electrode paste composition (electrode composition) containing copper-containing particles and glass particles as a method of suppressing copper oxidation during firing. ing.

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, the solar cell module includes a plurality of solar cell elements connected via a wiring member as a sealing material in order to ensure resistance to temperature change, wind and rain, snow accumulation, and the like. And sealed. 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. A solar cell module means what sealed the solar cell provided with the wiring member with the 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.

As described in JP-A-2004-204256 and JP-A-2005-050780, generally, solder is used for connection between the electrode of the solar cell element and the wiring member. 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 become widespread as a solder used for connection between an electrode of a solar cell element and a wiring member in consideration of environmental considerations.

On the other hand, as connection methods that do not use solder, Japanese Patent Application Laid-Open Nos. 2000-286436, 2001-357897, and Japanese Patent No. 3448924 disclose connection methods that use 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 JP-A-2000-286436, JP-A-2001-357897 and JP-A-3448924, there is a method for connecting an electrode of a solar cell element and a wiring member using a conductive paste. 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 a conductive paste, the adhesion between the copper-containing electrode of the solar cell element and the wiring member is insufficient. There was a tendency to.

The present invention has been made in view of the above problems, and uses an electrode connection set and an electrode connection set capable of obtaining excellent adhesion between the electrode and the wiring member and excellent connection reliability. It aims at providing the manufacturing method of a solar cell, a solar cell, and a solar cell module.

Specific means for achieving the above object are as follows.
<1> An electrode connection set comprising an electrode composition comprising phosphorus-tin-containing copper alloy particles and glass particles, and a connection material containing an adhesive.
<2> The electrode connection set according to <1>, wherein the electrode composition further includes nickel-containing particles.
<3> The electrode connection set according to <2>, wherein the nickel-containing particles are at least one selected from the group consisting of nickel particles and nickel alloy particles having a nickel content of 1% by mass or more.
<4> The electrode connection set according to any one of <1> to <3>, wherein the phosphorus-tin-containing copper alloy particles are phosphorus-tin-nickel-containing copper alloy particles further containing nickel.
<5> The electrode connection set according to <4>, wherein the phosphorus-tin-nickel-containing copper alloy particles have a phosphorus content of 2.0 mass% to 15.0 mass%.
<6> The electrode connection set according to <4> or <5>, wherein the phosphorus-tin-nickel-containing copper alloy particles have a tin content of 3.0% by mass to 30.0% by mass.
<7> The electrode connection set according to any one of <4> to <6>, wherein the phosphorus-tin-nickel-containing copper alloy particles have a nickel content of 3.0% by mass to 30.0% by mass. .
<8> In the particle size distribution of the phosphorus-tin-containing copper alloy particles, the particle diameter (D50%) when the volume integrated from the small diameter side is 50% is 0.4 μm to 10.0 μm <1> to <7 > The electrode connection set according to any one of the above.
<9> The electrode connection set according to any one of <1> to <8>, wherein the glass particles have a softening point of 650 ° C. or lower and a crystallization start temperature exceeding 650 ° C.
<10> The electrode connection set according to <9>, wherein the softening point of the glass particles is 583 ° C. or lower.
<11> The electrode connection set according to any one of <1> to <10>, wherein the glass particles contain lead (Pb).
<12> The electrode connection set according to any one of <1> to <11>, wherein a content ratio of the glass particles is 0.1% by mass to 12% by mass.
<13> The electrode connection set according to any one of <1> to <12>, wherein the connection material further includes a curing agent and a film forming material.
<14> The electrode connection set according to any one of <1> to <13>, wherein the connection material further includes conductive particles.
<15> The electrode connection set according to any one of <1> to <14>, wherein the electrode composition further contains a dispersion medium.
<16> 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 <15>, including a step of laminating the connection material and the wiring member on the containing electrode in this order to obtain a laminate, and a step of heating and pressurizing the laminate. The manufacturing method of the solar cell which manufactures a solar cell using the electrode connection set of claim | item.
<17> The method for producing a solar cell according to <16>, wherein the heat treatment is performed at 450 ° C. to 900 ° C.
<18> A solar cell obtained by the method for manufacturing a solar cell according to <16> or <17>.
<19> A solar cell module having a solar cell obtained by the method for producing a solar cell according to <16> or <17>, and a sealing material that seals the solar cell.

According to the present invention, an electrode connection set capable of obtaining excellent adhesion between the electrode and the wiring member and excellent connection reliability, a solar cell manufacturing method using the electrode connection set, a solar cell, and A 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.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless explicitly specified, unless otherwise clearly considered essential in principle. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto.

The electrode connection set of the present invention includes an electrode composition including phosphorus-tin-containing copper alloy particles and glass particles, a connection material including an adhesive, and other elements as required.
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 the solar cell obtained by using this set in which the electrode obtained from the electrode composition 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 heat treatment (firing) of the electrode composition of the electrode connection set according to the present invention includes a metal part showing an alloy phase containing copper and tin, such as a Cu—Sn alloy phase, and Sn—PO glass. And a glass part containing tin, phosphorus and oxygen. Among these, the Cu—Sn alloy phase forms a dense bulk metal portion. Moreover, the space | gap part in which the metal part and the glass part are not formed arises in an electrode. This is presumably because the reaction during the formation of the bulk metal part 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.

At least a part of the void is an open pore when viewed from the surface of the copper-containing electrode, and reaches the inside of the copper-containing electrode or the Sn—PO glass phase formed on the semiconductor substrate side. There is also. In addition, it is thought that the performance (for example, resistivity) as an electrode and the electric power generation performance of a solar cell element are not caused by the said copper containing electrode including the said space | gap part. At the time of 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. Thus, when 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 to each other. 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 metal portion of the copper-containing electrode and the wiring member are in direct contact with each other. You may do it.

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 heat processing (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, the high adhesion between the electrode and the wiring member is first manifested by combining the electrode composition and the connection material included in the electrode connection set of the present invention.

Further, in the present invention, by combining the electrode composition and the connection material, a reduction in electrical contact resistance can be exhibited 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, a connection interposed between the electrode and the wiring member. The material thickness 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 this specification, the amount of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication, when there are a plurality of substances corresponding to each component in the composition. Means quantity.
In this specification, the term “layer” includes a configuration formed in a part in addition to a configuration formed in the entire surface when observed as a plan view.
In this specification, the term “lamination” indicates that layers are stacked, and two or more layers may be combined, or two or more layers may be detachable.
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-tin-containing copper alloy particles and glass particles. A copper-containing electrode can be formed by applying this electrode composition to a semiconductor substrate having a pn junction and heat-treating (firing) 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.
Semiconductor substrates other than silicon substrates include gallium phosphide substrates, gallium nitride substrates, diamond substrates, aluminum nitride substrates, indium nitride substrates, gallium arsenide substrates, germanium substrates, zinc selenide substrates, zinc telluride substrates, cadmium telluride substrates. Examples include a substrate, a cadmium sulfide substrate, an indium phosphide substrate, a silicon carbide substrate, a germanium silicide substrate, and a copper indium selenium substrate.

By using the electrode composition, the oxidation of copper during heat treatment (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 according to the present invention is heat-treated (fired), a Cu—Sn alloy phase and a Sn—PO glass phase are formed by the reaction between copper and tin in the phosphorus-tin-containing copper alloy particles. . By forming the Cu—Sn alloy phase, an electrode having a low resistivity can be formed. Here, since the Cu—Sn alloy phase is generated even at a relatively low temperature of about 500 ° C., the electrode can be heat-treated (fired) at a low temperature, and the effect of reducing the process cost can be expected.

This can be considered as follows, for example.
Copper and tin in the phosphorus-tin-containing copper alloy particles react with each other in a heat treatment (firing) step to form a Cu—Sn alloy phase as a metal part and a Sn—PO glass phase as a glass part. An electrode is formed. The Cu—Sn alloy phase forms a dense bulk metal portion between the Cu—Sn alloy phases. This bulk metal part is formed in the electrode and functions as a conductive layer, whereby an electrode having a low resistivity is formed. In addition, the dense bulk metal portion 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.

Preferably, the electrode composition further contains nickel-containing particles, or the phosphorus-tin-containing copper alloy particles further contain nickel. As a result, it is considered that the Cu—Sn alloy phase and nickel 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 such as 800 ° C., an electrode having a low resistivity can be formed while maintaining oxidation resistance even in a heat treatment (firing) step at a higher temperature. Conceivable. Further, by using a copper-containing electrode formed from the electrode-containing composition containing the nickel-containing particles or the electrode-containing composition containing phosphorus-tin-nickel-containing copper alloy particles, the electrode can be maintained while maintaining adhesion to the silicon substrate. A better ohmic contact between the silicon substrate and the silicon substrate can be achieved. Similarly to the Cu—Sn alloy phase, the Cu—Sn—Ni alloy phase obtained by the electrode composition further containing nickel-containing particles or the phosphorus-tin-containing copper alloy particles further containing nickel is Cu— A dense bulk metal portion is formed between the Sn—Ni alloy phases or together with the Cu—Sn alloy phase. 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) of the electrode is not lowered.

When using copper particles imparted with oxidation resistance, which has been developed in the past, the oxidation resistance is at most 300 ° C., and the copper particles are almost oxidized at a high temperature of 800 ° C. to 900 ° C. For this reason, it has not been put to practical use as an electrode for solar cell elements, and further, the additive applied to impart oxidation resistance inhibits the sintering of copper particles, and as a result when silver is used as a result. There is a problem that an electrode having a low resistivity cannot be obtained. As another technique for suppressing copper oxidation, there has been proposed a method through a special manufacturing process in which a conductive composition using copper as a conductive metal powder is heat-treated (fired) in an atmosphere such as nitrogen. . However, in this method, in order to suppress the oxidation of the copper particles, a sealed environment is required so as to have an atmosphere filled with nitrogen or the like, which is not suitable for mass production of solar cell elements in terms of manufacturing cost.
According to the present invention, an electrode having a low resistivity can be formed without using a special method.

In addition, since 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 heat treatment (firing) and the silicon substrate can be obtained. It can be considered that it can be achieved. That is, the formation of a reactant phase (Cu ₃ Si) formed when a copper-containing electrode and a silicon substrate are directly contacted and heated is suppressed, and silicon performance (eg, pn junction characteristics) is not degraded. It is considered that good ohmic contact can be expressed while maintaining the adhesion between the substrate and the electrode.
Conventionally, an ohmic contact property between a silicon substrate and an electrode 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 copper-containing electrode, which may hinder the adhesion between the electrode and the silicon substrate, resulting in 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 particles containing phosphorus-tin)
The electrode composition according to the present invention contains at least one phosphor-tin-containing copper alloy particle. Generally, as a copper alloy containing phosphorus, 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, but by using copper alloy particles containing phosphorus in the electrode composition according to the present invention, the reducibility of phosphorus to copper oxide is improved. It is possible to form an electrode having excellent oxidation resistance and low resistivity. Furthermore, the electrode can be subjected to low-temperature heat treatment (firing), and the process cost can be reduced.

The phosphorus-tin-containing copper alloy particles in the present invention are particles composed of a copper alloy further containing tin in addition to phosphorus. By including the phosphorus-tin-containing copper alloy particles, an electrode including a Cu—Sn alloy phase that is a metal part and a Sn—PO glass phase that is a glass part is formed in a heat treatment (firing) step.

Specifically, by including the phosphorus-tin-containing copper alloy particles, an electrode having excellent oxidation resistance and low resistivity utilizing the reducibility of the phosphorus atom in the phosphorus-tin-containing copper alloy particles to the copper oxide. Is formed. Further, due to the reaction between copper and tin in the phosphorus-tin-containing copper alloy particles, a Cu—Sn alloy phase and a Sn—PO glass phase are formed in the electrode while keeping the resistivity low. For example, the Sn—PO glass phase functions as a barrier layer for preventing mutual diffusion between copper and silicon, so that a reactant phase is formed between the copper-containing electrode and the silicon substrate. It can be considered that two characteristic mechanisms of suppressing and forming a good ohmic contact between the copper-containing electrode and the silicon substrate can be realized at once in a heat treatment (firing) step.

When phosphorus-tin-containing copper alloy particles are used in the present invention, the phosphorus content contained in the phosphorus-tin-containing copper alloy is not particularly limited. From the viewpoint of oxidation resistance and electrode resistivity, the phosphorus content is preferably 2% by mass to 15% by mass, more preferably 3% by mass to 12% by mass, and more preferably 4% by mass to 10%. More preferably, it is at most mass%. When the phosphorus content in the phosphorus-tin-containing copper alloy is 15% by mass or less, a lower resistivity can be achieved, and the productivity of the phosphorus-tin-containing copper alloy particles tends to be excellent. Further, when the phosphorus content contained in the phosphorus-tin-containing copper alloy is 2% by mass or more, more excellent oxidation resistance tends to be achieved.

Further, the tin content contained in the phosphorus-tin-containing copper alloy when using the phosphorus-tin-containing copper alloy particles in the present invention is not particularly limited. From the viewpoint of oxidation resistance and reactivity with copper and phosphorus during heat treatment (firing), it is preferably 5% by mass to 30% by mass, more preferably 6% by mass to 25% by mass, More preferably, it is 7 mass% or more and 20 mass% or less. When the tin content in the phosphorus-tin-containing copper alloy is 30% by mass or less, a sufficient volume of the Cu—Sn alloy phase can be formed, and the resistivity of the electrode tends to decrease. Moreover, it exists in the tendency which can produce reaction with copper and phosphorus more uniformly by making content rate of tin into 5 mass% or more.

Further, when the phosphorus-tin-containing copper alloy particles are used in the present invention, the combination of phosphorus content and tin content contained in the phosphorus-tin-containing copper alloy includes oxidation resistance, electrode resistivity, and heat treatment (firing). From the viewpoint of reactivity with copper and phosphorus, the phosphorus content is preferably 2% by mass or more and 15% by mass or less, and the tin content is preferably 5% by mass or more and 30% by mass or less. More preferably, the content is 3% by mass or more and 12% by mass or less, and the tin content is more preferably 6% by mass or more and 25% by mass or less, and the phosphorus content is 4% by mass or more and 10% by mass or less. Is more preferably 7% by mass or more and 20% by mass or less.

The phosphorus-tin-containing copper alloy in the present invention further contains at least one metal atom selected from the group consisting of silver, manganese and cobalt (hereinafter also referred to as “specific metal atom”) in addition to phosphorus and tin. A copper alloy is also preferred. By further including the specific metal atom, a lower resistance electrode tends to be formed.
The content rate of the specific metal atom in the copper alloy containing phosphorus, tin, and the specific metal atom can be appropriately selected according to the type and purpose of the specific metal atom. The content of the specific metal atom can be, for example, 0.05% by mass to 20% by mass, preferably 0.1% by mass to 15% by mass, and 1% by mass to 10% by mass. Is more preferable. When the content of the specific metal atom is 0.05% by mass or more, the melting point of the alloy particles can be further lowered, and the sintering reaction of the alloy particles in the heat treatment (firing) step tends to further progress. Further, when the content of the specific metal atom is 20% by mass or less, the oxidation resistance is improved and an electrode having a low resistivity tends to be formed.

The phosphorus-tin-containing copper alloy is a copper alloy containing phosphorus and tin, but may further contain other atoms inevitably mixed other than silver, manganese and cobalt. Other atoms that are inevitably mixed include, for example, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Al, Zr, W, and Mo. Ti, Ni and Au can be mentioned.
The content of other atoms inevitably mixed in the phosphorus-tin-containing copper alloy particles can be, for example, 3% by mass or less in the phosphorus-tin-containing copper alloy particles, From the standpoint of the property and resistivity of the electrode, it is preferably 1% by mass or less.

Note that the content of each element in the phosphorus-tin-containing copper alloy constituting the phosphorus-tin-containing copper alloy particles can be measured by quantitative analysis using an inductively coupled plasma mass spectrometry (ICP-MS) method.

In addition, the content of each element in the phosphorus-tin-containing copper alloy constituting the phosphorus-tin-containing copper alloy particles can also be measured by a quantitative analysis by an energy dispersive X-ray spectroscopy (EDX) method. Specifically, phosphorus-tin-containing copper alloy particles are embedded in a resin, cured, and then cut with a diamond cutter or the like, and polished with water-resistant abrasive paper, polishing liquid, or the like as necessary. It is preferable to analyze the cross section of certain phosphorus-tin-containing copper alloy particles. The reason can be considered as follows, for example.

Since the phosphorus-tin-containing copper alloy particles of the present invention contain phosphorus, the phosphorus-tin-containing copper alloy particles may absorb moisture depending on the handling environment, and as a result, the surface of the particles may be oxidized. is there. The film formed by this oxidation is formed on the very surface and is thought to have little effect on the quality of the phosphorus-tin-containing copper alloy particles. However, due to the increase in the oxygen content on the particle surface, etc. May cause a difference in the content of each metal element. Therefore, when measuring the content of each element in the phosphorus-tin-containing copper alloy particles, it is considered preferable to measure the particle cross section instead of the particle surface.

In the present invention, the phosphorus-tin-containing copper alloy particles may be used singly or in combination of two or more.
In the present invention, “use in combination of two or more types of phosphorus-tin-containing copper alloy particles” means two or more types of phosphorus-tin having the same particle shape such as the particle size and particle size distribution described later, although the component ratio is different. When using a combination of copper alloy particles containing two or more types of phosphorus-tin containing copper alloy particles having the same component ratio but different particle shapes, using two or more types of component ratios and particle shapes are different. For example, a combination of phosphorus-tin-containing copper alloy particles may be used.

The particle diameter of the phosphorus-tin-containing copper alloy particles is not particularly limited, but the particle diameter (D50%) when the volume integrated from the small diameter side is 50% in the particle size distribution is 0.4 μm to 10 μm. Is preferably 1 μm to 7 μm. When the D50% of the phosphorus-tin-containing copper alloy particles is 0.4 μm or more, the oxidation resistance tends to be more effectively improved. Further, when the D50% of the phosphorus-tin-containing copper alloy particles is 10 μm or less, the contact area between the phosphorus-tin-containing copper alloy particles in the electrode is increased, and the resistivity tends to be more effectively reduced. The particle size (D50%) of the phosphorus-tin-containing copper alloy particles is measured by a laser diffraction particle size distribution analyzer (for example, Beckman Coulter, Inc., LS 13 320 type laser scattering diffraction particle size distribution analyzer). The Specifically, phosphorus-tin-containing copper alloy particles are added in a range of 0.01 mass% to 0.3 mass% to 125 g of a solvent (terpineol) to prepare a dispersion. About 100 ml of this dispersion is poured into a cell and measured at 25 ° C. The particle size distribution is measured as a solvent refractive index of 1.48.
The shape of the phosphorus-tin-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, and the like. From the viewpoint, it is preferably substantially spherical, flat or plate-like.

The phosphorus-tin-containing copper alloy can be produced by a commonly used method. Also, the phosphorus-tin-containing copper alloy particles should be prepared using a normal method of preparing metal powder using a phosphorus-tin-containing copper alloy prepared so as to have a desired phosphorus content and tin content. Can do. For example, it can be manufactured by a conventional method using a water atomizing method. For details of the water atomization method, the description of Metal Handbook (Maruzen Co., Ltd. Publishing Division) can be referred to.
Specifically, a desired phosphorus-tin-containing copper alloy particle is manufactured by dissolving a phosphorus-tin-containing copper alloy and pulverizing this by nozzle spraying, and then drying and classifying the obtained powder. be able to. In addition, phosphorus-tin-containing copper alloy particles having a desired particle diameter can be produced by appropriately selecting the classification conditions.

(Phosphorus particles containing phosphorus-tin-nickel)
In the electrode composition according to the present invention, the phosphorus-tin-containing copper alloy particles may further contain nickel, so that the phosphorus-tin-containing copper alloy particles may be used as the phosphorus-tin-nickel-containing copper alloy particles. The phosphorus-tin-nickel-containing copper alloy particles are copper alloy particles further containing tin and nickel in addition to phosphorus. By using phosphorus-tin-nickel-containing copper alloy particles, oxidation resistance at higher temperatures can be expressed in the heat treatment (firing) step. That is, by using phosphorus-tin-nickel-containing copper alloy particles, the electrode composition can be heat-treated (fired) at a higher temperature.

Specifically, the electrode composition of the present invention contains phosphorus-tin-nickel-containing copper alloy particles as metal particles, so that first, a copper oxide of phosphorus atoms in the phosphorus-tin-nickel-containing copper alloy particles An electrode having excellent oxidation resistance and low resistivity is formed by utilizing the reducing property against the above. Further, since the alloy particles contain tin and nickel, the Cu—Sn alloy phase, or the Cu—Sn—Ni alloy phase and the Sn—PO glass phase are kept in the electrode while keeping the resistivity of the electrode low. It is formed. For example, the Sn—P—O glass phase is formed in a three-dimensional continuous structure of a Cu—Sn alloy phase or a Cu—Sn—Ni alloy phase, so that the electrode itself has a dense structure, and as a result, the electrode An improvement in strength is obtained. In addition, since the Sn—PO glass phase functions as a barrier layer for preventing mutual diffusion between copper and silicon, a good ohmic contact is formed between the copper-containing electrode and the silicon substrate. It can be considered that such a characteristic mechanism can be realized collectively in the heat treatment (firing) step.

The phosphorus content contained in the phosphorus-tin-nickel-containing copper alloy constituting the phosphorus-tin-nickel-containing copper alloy particles in the present invention is not particularly limited. From the viewpoint of improving oxidation resistance (reducing the resistivity of the electrode) and forming ability of the Sn—PO glass phase, the phosphorus content is preferably 2.0% by mass to 15.0% by mass. More preferably, the content is from 5% by mass to 12.0% by mass, and even more preferably from 3.0% by mass to 10.0% by mass. When the phosphorus content in the phosphorus-tin-nickel-containing copper alloy is 15.0% by mass or less, a lower resistivity can be achieved, and the productivity of the phosphorus-tin-nickel-containing copper alloy particles can be improved. It tends to be excellent. In addition, when the phosphorus content in the phosphorus-tin-nickel-containing copper alloy is 2.0 mass% or more, the Sn—PO glass phase can be effectively formed, and the adhesion to the semiconductor substrate is improved. Therefore, an electrode excellent in ohmic contact tends to be formed.

Further, the tin content contained in the phosphorus-tin-nickel-containing copper alloy constituting the phosphorus-tin-nickel-containing copper alloy particles is not particularly limited. From the viewpoints of oxidation resistance, reactivity with copper and nickel during heat treatment (firing) and ability to form a Sn—PO glass phase, the tin content is 3.0% by mass to 30.0% by mass. It is preferably 4.0% by mass to 25.0% by mass, more preferably 5.0% by mass to 20.0% by mass. When the tin content in the phosphorus-tin-nickel-containing copper alloy is 30.0% by mass or less, a Cu—Sn—Ni alloy phase having a lower resistivity tends to be formed. Also, by setting the tin content in the phosphorus-tin-nickel-containing copper alloy to 3.0% by mass or more, the reactivity with copper and nickel during heat treatment (firing) and the reactivity with phosphorus are improved. However, there is a tendency that a Cu—Sn—Ni alloy phase and a Sn—P—O glass phase can be formed effectively.

Further, the nickel content contained in the phosphorus-tin-nickel-containing copper alloy constituting the phosphorus-tin-nickel-containing copper alloy particles is not particularly limited. From the viewpoint of oxidation resistance, the nickel content in the phosphorus-tin-nickel-containing copper alloy is preferably 3.0% by mass to 30.0% by mass, more preferably 3.5% by mass to 25.0% by mass. More preferably, the content is 4.0% by mass to 20.0% by mass. When the nickel content in the phosphorus-tin-nickel-containing copper alloy is 30.0% by mass or less, a Cu—Sn—Ni alloy phase having a low resistivity tends to be formed more effectively. . In addition, by setting the nickel content in the phosphorus-tin-nickel-containing copper alloy to 3.0% by mass or more, oxidation resistance particularly in a high temperature region of 500 ° C. or more tends to be improved.

Furthermore, the combination of phosphorus content, tin content, and nickel content contained in the phosphorus-tin-nickel-containing copper alloy constituting the phosphorus-tin-nickel-containing copper alloy particles includes oxidation resistance and electrode resistivity. From the viewpoint of the reactivity of copper, phosphorus, tin and nickel during heat treatment (firing), the ability to form a Sn—PO glass phase, and the adhesion between the electrode and the silicon substrate, the phosphorus content is 2.0 mass. % To 15.0% by mass, a tin content of 3.0% to 30.0% by mass, and a nickel content of 3.0% to 30.0% by mass The phosphorus content is 2.5% by mass to 12.0% by mass, the tin content is 4.0% by mass to 25.0% by mass, and the nickel content is 3.5% by mass. More preferably, the content is from 2% by mass to 25.0% by mass, and the phosphorus content is 3. Mass% to 10.0 mass%, tin content is 5.0 mass% to 20.0 mass%, and nickel content is 4.0 mass% to 20.0 mass% More preferably.

The phosphorus-tin-nickel-containing copper alloy particles are copper alloy particles containing phosphorus, tin, and nickel, but may further contain other atoms inevitably mixed therein. Examples of other atoms inevitably mixed include Ag, Mn, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Al, and Zr. , W, Mo, Ti, Co, Au and Bi.
The content of other atoms inevitably mixed in the phosphorus-tin-nickel-containing copper alloy particles can be, for example, 3% by mass or less in the phosphorus-tin-nickel-containing copper alloy particles, From the viewpoint of reducing the resistivity and the electrode resistivity, it is preferably 1% by mass or less.

Phosphorus-tin-nickel-containing copper alloy particles may be used singly or in combination of two or more. In the present invention, “use in combination of two or more types of phosphorus-tin-nickel-containing copper alloy particles” means two or more types of phosphorus having the same particle shape such as the particle size and particle size distribution described later, although the component ratio is different. -When tin-nickel-containing copper alloy particles are used in combination, when the component ratio is the same, but two or more types of phosphorus-tin-nickel-containing copper alloy particles having different particle shapes are used in combination, the component ratio and particle shape are An example is a combination of two or more types of phosphorus-tin-nickel-containing copper alloy particles that are different from each other.

The particle diameter of the phosphorus-tin-nickel-containing copper alloy particles is not particularly limited. In the particle size distribution, when the volume integrated from the small diameter side is 50%, the particle diameter (D50%) is preferably 0.4 μm to 10 μm, and more preferably 1 μm to 7 μm. When the D50% of the phosphorus-tin-nickel-containing copper alloy particles is 0.4 μm or more, the oxidation resistance tends to be more effectively improved. By setting the D50% of the phosphorus-tin-nickel-containing copper alloy particles to 10 μm or less, the contact area between the phosphorus-tin-nickel-containing copper alloy particles in the electrode is increased, and the resistivity of the electrode is more effectively reduced. Tend to.

The particle diameter of the phosphorus-tin-nickel-containing copper alloy particles is the same as the method for measuring the particle diameter of the phosphorus-tin-containing copper alloy particles.

The shape of the phosphorus-tin-nickel-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, and the like. From the viewpoint of oxidation resistance and low resistivity, the shape of the phosphorus-tin-nickel-containing copper alloy particles is preferably substantially spherical, flat or plate-like.

The phosphorus-tin-nickel-containing copper alloy can be produced by a commonly used method, and the phosphorus-tin-nickel-containing copper alloy particles have a desired phosphorus content, tin content, and nickel content. The phosphor-tin-nickel-containing copper alloy prepared as described above can be used in the same manner as the phosphor-tin-containing copper alloy particles.

(Nickel-containing particles)
When the electrode composition used in the present invention contains phosphorus-tin-containing copper alloy particles, it is preferable that nickel-containing particles are further included as metal particles. When the electrode composition used in the present invention contains nickel-containing particles in addition to the phosphorus-tin-containing copper alloy particles, oxidation resistance at higher temperatures can be expressed in the heat treatment (firing) step. It tends to be possible. That is, when the electrode composition used in the present invention contains nickel-containing particles, the electrode composition tends to be heat-treated (fired) at a higher temperature. When the electrode composition used in the present invention contains nickel-containing particles, it may be used in combination with phosphorus-tin-containing copper alloy particles or in combination with phosphorus-tin-nickel-containing copper alloy particles. . Further, when the electrode composition used in the present invention contains phosphorus-tin-nickel-containing copper alloy particles, it is not always necessary to use them together with the nickel-containing particles.

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.
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 Cu—Sn alloy phase during heat treatment (firing), the nickel alloy particles preferably have a nickel content of 1% by mass or more. Is more preferably nickel alloy particles having a nickel content of 5% by mass or more, more preferably nickel alloy particles having a nickel content of 10% by mass or more. Particularly preferred are alloy particles. There is no particular limitation on the upper limit of the nickel content.

Examples of the nickel alloy constituting the nickel alloy particles include a Ni—Fe alloy, a Ni—Cu alloy, a Ni—Cu—Zn alloy, a Ni—Cr alloy, and a Ni—Cr—Ag alloy. In particular, nickel alloy particles containing Ni-58Fe, Ni-75Cu, Ni-6Cu-20Zn, etc., react more uniformly with phosphorus-tin-containing copper alloy particles or phosphorus-tin-nickel-containing copper alloy particles during heat treatment (firing). It can be preferably used in that it can be used. 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.
In the electrode composition, these nickel-containing particles may be used alone or in combination of two or more.
In the present invention, “use in combination of two or more kinds of nickel-containing particles” means that two or more kinds of nickel-containing particles having the same particle shape such as particle diameter and particle size distribution described later are used in combination although the component ratio is different. In this case, there are cases where two or more kinds of nickel-containing particles having the same component ratio but different particle shapes are used in combination, and two or more kinds of nickel-containing particles having different component ratios and particle shapes are used in combination. .

The nickel-containing particles may further contain other atoms inevitably mixed. Examples of other atoms inevitably mixed include Ag, Mn, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Al, and Zr. , W, Mo, Ti, Co, Sn, and Au.
The content of other atoms inevitably mixed in the nickel-containing particles can be, for example, 3% by mass or less in the nickel-containing particles, the melting point, and the phosphorus content during heat treatment (firing). From the viewpoint of reactivity with tin-containing copper alloy particles or phosphorus-tin-nickel-containing copper alloy particles, the content is preferably 1% by mass or less.

The particle diameter of the nickel-containing particles is not particularly limited, and the particle diameter (D50%) is preferably 0.5 μm to 20 μm, more preferably 1 μm to 15 μm, and more preferably 3 μm to 15 μm. Further preferred. When the particle diameter (D50%) of the nickel-containing particles is 0.5 μm or more, the oxidation resistance of the nickel-containing particles themselves tends to be improved. Further, when the particle diameter (D50%) of the nickel-containing particles is 20 μm or less, the contact area between the nickel-containing particles and the phosphorus-tin-containing copper alloy particles or the phosphorus-tin-nickel-containing copper alloy particles is increased, The reaction during heat treatment (firing) with phosphorus-tin-containing copper alloy particles or phosphorus-tin-nickel-containing copper alloy particles tends to proceed effectively.
The method for measuring the particle diameter (D50%) of the nickel-containing particles is the same as the method for measuring the particle diameter of the phosphorus-tin-containing copper alloy particles.
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, and the like. From the viewpoint of oxidation resistance and reduction in the resistivity of the electrode, it is preferably substantially spherical, flat or plate-like.

Moreover, the content rate of the nickel containing particle in the case where the composition for electrodes contains nickel containing particle is not particularly limited. In particular, the content of the nickel-containing particles is 10% by mass or more and 70% when the total content of the phosphorus-tin-containing copper alloy particles or the phosphorus-tin-nickel-containing copper alloy particles and the nickel-containing particles is 100% by mass. It is preferably at most mass%, more preferably at least 12 mass% and at most 55 mass%, further preferably at least 15 mass% and at most 50 mass%, and at least 15 mass% and at most 35 mass%. Is particularly preferred.
By setting the content of the nickel-containing particles to 10% by mass or more, the Cu—Sn—Ni alloy phase tends to 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 tends to be further reduced.

The total content of the phosphorus-tin-containing copper alloy particles (or phosphorus-tin-nickel-containing copper alloy particles) and the nickel-containing particles added as necessary in the composition for an electrode depends on oxidation resistance and electrode resistance. From the viewpoint of rate, it is preferably 60% by mass or more and 94% by mass or less, and more preferably 64% by mass or more and 88% by mass or less.

(Glass particles)
The composition for electrodes used in the present invention contains glass particles. When the electrode composition contains glass particles, adhesion between the electrode and the silicon substrate is improved during heat treatment (firing). Further, particularly in the formation of the electrode on the light-receiving surface side of the solar cell, the silicon nitride layer as the antireflection layer is removed by so-called fire-through during heat treatment (firing), and an ohmic contact between the electrode and the silicon substrate is formed.

The glass particles are preferably glass particles containing glass having a 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 softening temperature and the crystallization start temperature are measured by a usual method using a differential thermal-thermogravimetric analyzer (TG-DTA).

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 layer, and take in oxidized silicon dioxide. As long as the antireflection layer can be removed, glass particles usually used in the technical field can be used without particular limitation.

In general, glass particles contained in the electrode composition preferably contain lead from the viewpoint that silicon dioxide can be efficiently incorporated. Examples of the glass containing lead include those described in Japanese Patent No. 3050064.
In the present invention, it is also 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 the lead-free glass described in paragraphs 0024 to 0025 of JP-A-2006-313744 and the lead-free glass described in JP-A-2009-188281. It is also preferable to select an appropriate material from free glass and apply it to the electrode composition used in the present invention.

Further, 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, a back surface output extraction electrode, it includes a glass having a softening temperature of 650 ° C. or lower and a crystallization start temperature exceeding 650 ° C. If it is a glass particle, the glass particle which does not contain the component required for fire through like the said lead can be used. The softening point of the glass particles is more preferably 583 ° C. or lower.

Examples of the glass component constituting the glass particles used in the electrode composition include silicon oxide (SiO or 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 ), niobium oxide (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, Fe ₂ O ₃ or Fe ₃ O ₄ ), silver oxide (AgO or Ag ₂₎ O) and manganese oxide (MnO).

Among them, glass particles containing at least one selected from the group consisting of 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 are used. It is more preferable to use glass particles containing at least one selected from the group consisting of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ and PbO. In the case of such glass particles, the softening temperature tends to decrease more effectively. Furthermore, since the wettability with the phosphorus-tin-containing copper alloy particles or the phosphorus-tin-nickel-containing copper alloy particles and the nickel-containing particles added as necessary is improved, the inter-particles in the heat treatment (firing) process are improved. Sintering progresses and it tends to be possible to form an electrode with a lower resistivity.

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

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 particle diameter of the glass particles is 0.5 μm or more, the workability during the production of the electrode composition tends to be improved. Moreover, since the particle diameter of the glass particles is 10 μm or less, the glass particles can be more uniformly dispersed in the electrode composition, and fire-through can be efficiently generated in the heat treatment (firing) step, and the adhesion to the silicon substrate is also improved. It tends to improve. The method for measuring the particle size (D50%) of the glass particles is the same as the method for measuring the particle size of the phosphorus-tin-containing copper alloy particles.
Moreover, there is no restriction | limiting in particular as a shape of the said glass particle, Any of substantially spherical shape, flat shape, block shape, plate shape, scale shape, etc. may be sufficient. From the viewpoint of oxidation resistance and electrode resistivity, it is preferably substantially spherical, flat or plate-like.

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 resistance can be achieved more effectively, and the reaction between the metal particles can be promoted. There is a tendency.

In the electrode composition, the ratio of the content of glass particles to the total content of metal particles (mass ratio, glass particles / metal particles) is preferably 0.01 to 0.18, preferably 0.03 to 0. .15 is more preferable. Inclusion of glass particles in such a content ratio tends to more effectively achieve oxidation resistance, lower electrode resistivity and lower contact resistance, and promote the reaction between the metal particles. It is in.

(Dispersion medium)
The electrode composition used in the present invention may contain 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 selected from the group consisting of a solvent and a resin.

The solvent is not particularly limited, and is a hydrocarbon solvent such as hexane, cyclohexane or toluene, a halogenated hydrocarbon solvent such as dichloroethylene, dichloroethane or dichlorobenzene, tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, or 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, 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, terpinene, terpineol, pinene, myrcene, alloocimene, limonene, dipentene, carvone, oscene, ferrandylene, and other terpene solvents, and mixtures thereof. It is.

The solvent is a group consisting of a polyhydric alcohol ester solvent, a terpene solvent, and a polyhydric alcohol ether solvent from the viewpoint of application characteristics (applicability or printability) when applying the electrode composition onto a semiconductor substrate. It is preferably at least one selected from the group consisting of polyhydric alcohol ester solvents and terpene solvents, and more preferably at least one selected from the group consisting of terpene solvents.
In the electrode composition used in the present invention, the solvent may be used alone or in combination of two or more.

Further, as the resin, any resin that is usually used in the technical field can be used without particular limitation as long as it can be thermally decomposed by heat treatment (firing), and even a natural polymer compound can be a synthetic polymer compound. May be. Specifically, cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, nitrocellulose, polyvinyl alcohol resins, polyvinyl pyrrolidone resins, acrylic resins, vinyl acetate-acrylic acid ester copolymers, butyral resins such as polyvinyl butyral, phenol-modified alkyds, etc. Examples thereof include resins, alkyd resins such as castor oil fatty acid-modified alkyd resins, epoxy resins, phenol resins, rosin ester resins and the like.

In the present invention, when the resin is contained in the electrode composition, it is preferably at least one selected from the group consisting of a cellulose resin and an acrylic resin from the viewpoint of disappearance in heat treatment (firing).
In the present invention, the resins may be used alone or in combination of two or more.

In the present invention, the weight average molecular weight of the resin when the resin is contained in the electrode composition is not particularly limited. Among them, the weight average molecular weight of the resin is preferably 5,000 or more and 500,000 or less, and more preferably 10,000 or more and 300,000 or less. 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. Further, if the weight average molecular weight of the resin is 5000 or more, it is considered that the particles can be made difficult to aggregate due to the steric repulsion when the resin is adsorbed to the metal particles in the electrode composition. . 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 is increased, and when the electrode composition is heat-treated (fired), the resin is not combusted and remains as a foreign substance. Therefore, there is a tendency that a lower resistivity electrode can be formed.

The weight average molecular weight is obtained by conversion from a molecular weight distribution measured using GPC (gel permeation chromatography) using a standard polystyrene calibration curve. The calibration curve is approximated in three dimensions using five standard polystyrene sample sets (PStQuick MP-H, PStQuick B, Tosoh Corporation). The measurement conditions of GPC are as follows.
Equipment: (Pump: L-2130 type [Hitachi High-Technologies Corporation]), (Detector: L-2490 type RI [Hitachi High-Technologies Corporation]), (Column oven: L-2350 [Corporation] Hitachi High-Technologies])
Column: Gelpack GL-R440 + Gelpack GL-R450 + Gelpack GL-R400M (3 in total) (Hitachi Chemical Co., Ltd.)
-Column size: 10.7 mm x 300 mm (inner diameter)
・ Eluent: Tetrahydrofuran ・ Sample concentration: 10 mg / 2 mL
・ Injection volume: 200 μL
・ Flow rate: 2.05 mL / min ・ Measurement temperature: 25 ° C.

In the present invention, when the dispersion medium contains the dispersion medium, 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 5% by mass or more and 35% by mass or less, based on the total mass of the electrode composition, and 7% by mass. More preferably, it is 30 mass% or less.
When the content of the dispersion medium is within the above range, the application characteristics when applying the electrode composition to the semiconductor substrate are improved, and an electrode having a desired width and height can be more easily formed. It tends to be possible.
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.

(flux)
The electrode composition may contain a flux. When the electrode composition contains a flux, the oxide film formed on the surface of the phosphorus-tin-containing copper alloy particles or the phosphorus-tin-nickel-containing copper alloy particles is removed, and the phosphorus-tin during the heat treatment (firing) There is a tendency that the reduction reaction of the copper alloy particles containing phosphorus or the tin-nickel-containing copper alloy particles can be promoted. Furthermore, since the electrode composition contains a flux, the adhesion between the electrode and the silicon substrate tends to be improved.

The flux can remove the oxide film formed on the surface of the phosphorus-tin-containing copper alloy particles or the phosphorus-tin-nickel-containing copper alloy particles and promote the melting of the nickel-containing particles added as necessary If there is no restriction in particular. 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 them, the heat resistance during heat treatment (firing) of the electrode composition (the property that the flux does not volatilize at low temperatures during heat treatment (firing)) and the oxidation resistance of the phosphorus-tin-containing copper alloy particles or phosphor-tin-nickel-containing copper alloy particles From the viewpoint of complementing the properties, potassium borate and potassium borofluoride are particularly preferable fluxes.
In the electrode composition used in the present invention, each of these fluxes may be used alone or in combination of two or more.

When the electrode composition contains a flux, the flux content is such that the oxidation resistance of the phosphorus-tin-containing copper alloy particles or the phosphorus-tin-nickel-containing copper alloy particles is effectively expressed, and the electrode composition From the viewpoint of reducing voids generated in the portion where the flux is removed when the heat treatment (firing) of the product is completed, the content is preferably 0.1% by mass to 5% by mass in the total mass of the electrode composition. It is more preferably 3% by mass to 4% by mass, further preferably 0.5% by mass to 3.5% by mass, particularly preferably 0.7% by mass to 3% by mass, and 1% by mass. % To 2.5% by mass is very particularly preferred.

(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. It can manufacture by disperse | distributing or mixing the said metal particle, glass particles, and other components, such as a dispersion medium added as needed, using the dispersion method or mixing method used normally.
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 state of the connecting material include a film form, a paste form, and a solution form. About the state of the said connection material, it can adjust suitably with the kind and content rate of the 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. Moreover, since the solder seepage does not occur as in the case 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. When the viscosity is 40000 Pa · s or less, the wiring member tends to easily penetrate into the void formed in the electrode during thermocompression bonding. The viscosity of the connecting material is more preferably 20000 Pa · s or less, and further 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 under the conditions of 25 ° C. and a frequency of 10 Hz using a TA Instruments Japan Co., Ltd. and a shear viscometer measuring device (ARES).
Hereinafter, each component contained in the connecting material used in the present invention will be described in detail.

(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 phenol resin, a melamine resin, and an alkyd resin are mentioned. Among these, an epoxy resin is preferable from the viewpoint of obtaining sufficient connection reliability.

The content of the adhesive is not particularly limited. From the viewpoint of film formability before curing or adhesive strength after curing, the content of the adhesive is preferably 20% by mass or more and 70% by mass or less, and 30% by mass or more and 60% by mass or less in the connection material. It is more preferable that it is 40 mass% or more and 50 mass% or less.

(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 may be used alone or in combination 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 anionic or cationic polymerizable catalyst-type curing agents include tertiary amine derivatives, imidazole derivatives, hydrazide compounds, boron trifluoride-amine complexes, onium salts (sulfonium salts, ammonium salts, etc.), amine imides, diamino maleos Nitriles, melamine and derivatives thereof, salts of polyamines, and dicyandiamide can be used, and modifications thereof can also be used. Examples of the polyaddition type curing agent include polyamines, polymercaptans, polyphenols, and acid anhydrides.
As the anionic or cationic polymerizable catalyst-type curing agent, it is preferable to use a tertiary amine derivative or an imidazole derivative, and it is more preferable to use an imidazole derivative in terms of adhesive strength.

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 (Ajinomoto Co., Inc., registered trademark), NovaCure (Asahi Kasei E-Materials Co., Ltd., registered trademark) in which microencapsulated amine is dispersed in phenolic resin, etc. 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 resin, polycarbonate resin, acrylic rubber, polyimide resin, polyamide resin, polyurethane resin, polyester resin, polyester urethane resin, and polyvinyl butyral resin, and are phenoxy resin or acrylic rubber. It is preferable.
The weight average molecular weight of the film forming material is preferably from 5,000 to 2,000,000, more preferably from 8,000 to 1,000,000, and even more preferably from 10,000 to 1,000,000.
The weight average molecular weight of the film forming material is measured according to a conventional method using a gel permeation chromatography method (GPC).

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 thereof include gold particles, silver particles, copper particles, nickel particles, gold-plated nickel particles, gold / nickel-plated plastic particles, copper-plated particles, and nickel particles. It is done. When conductive particles are contained, the particle size (D50%) 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. . The method for measuring the particle size (D50%) of the conductive particles is the same as the method for measuring the particle size of the phosphorus-tin-containing copper alloy particles.
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 can 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.

Further, the cross-sectional shape of the tab wire is not particularly limited, and any of a rectangular shape (flat tab) and an elliptical shape (round tab) can be applied, and the copper content 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 (firing) the substrate to form a copper-containing electrode (referred to as an electrode formation step), and a step of laminating the connection material and the wiring member in this order on the copper-containing electrode to obtain a laminate (lamination) 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 the application of the electrode composition is dried (heated) after drying. Thereby, the heat processing (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 (baking) is performed in the presence of oxygen (for example, in the air).

As a heat treatment (firing) condition for forming a copper-containing electrode on a semiconductor substrate using the electrode composition, a commonly used heat treatment (firing) condition can be applied.
In general, the heat treatment (firing) temperature is 800 ° C. to 900 ° C., but when the electrode composition is used, a wide range from a lower temperature heat treatment (firing) condition to a general heat treatment (firing) condition. Can be applied to. For example, an electrode having good characteristics can be formed by heat treatment (firing) performed in a wide temperature range of 450 ° C. to 900 ° C.
The heat treatment (firing) time can be appropriately selected according to the heat treatment (firing) 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. The infrared heating furnace is highly efficient and can be rapidly heated in a short time because electric energy is directly input to the heating material in the form of electromagnetic waves and converted into heat energy. 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 performs heat treatment (firing), it can be more uniformly heat treated (firing) by controlling the division of the furnace body and the conveying speed. From the viewpoint of the power generation performance of the solar cell element, it is preferable to perform heat treatment (firing) with a tunnel furnace.

Hereinafter, although the specific example of the solar cell element of this invention 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 the schematic sectional view in FIG. 1, in the vicinity of the surface of the one surface of the semiconductor substrate 1, n ⁺ -type diffusion layer 2 is formed, the light-receiving surface output extraction electrode 4 and reflected on the n ⁺ -type diffusion layer 2 A prevention layer 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 ⁺ -type 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 layer 3 such as silicon nitride is provided on the n ⁺ type diffusion layer 2 with a thickness of about 90 nm by PECVD (plasma enhanced chemical vapor deposition) 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, and the back surface collecting electrode 5 and the back surface formed on the back surface schematically shown in FIG. A method for forming the 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 the first method for forming the light receiving surface output extraction electrode 4, the light receiving surface current collecting electrode 8, the back surface output extraction electrode 6 and the back surface current collecting electrode 5, the electrode composition and the aluminum electrode composition are screen printed. For example, it may be formed by applying a desired pattern, etc., and then drying and then heat-treating (baking) at a temperature of about 750 ° C. to 900 ° C. in the air.

At that 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 current collecting electrode 8 react with the antireflection layer 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, the light receiving surface output extraction electrode 4 and the light receiving surface current collecting electrode 8 are formed by using the electrode composition, so that copper oxidation is suppressed while containing copper as the conductive metal. A copper-containing electrode with low resistivity is formed with good productivity.
Further, the copper-containing electrode preferably 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 a Cu—Sn alloy phase or More preferably (not shown) between the Cu—Sn—Ni alloy phase and the semiconductor substrate. As a result, the reaction between copper and the semiconductor substrate is suppressed, and an electrode having low resistivity and excellent adhesion can be formed.

On the back surface side, aluminum in the aluminum electrode composition that forms the back current collecting electrode 5 during heat treatment (firing) diffuses to the back surface of the semiconductor substrate 1 to form the p ⁺ -type diffusion layer 7. Thus, an ohmic contact can be obtained between the semiconductor 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 heat treatment (baking) in the atmosphere at about 750 ° C. to 900 ° C. to form the back current collecting electrode 5, the electrode composition is applied to the light receiving surface side and the back surface side, and after drying, 450 ° C. 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 heat treatment (baking) at about 650 ° C. can be mentioned.

This method is effective in the following cases, for example. That is, when the aluminum electrode composition for forming the back surface collecting electrode 5 is heat-treated (fired), at a heat treatment (baking) temperature of 650 ° C. or less, the aluminum particles are fired depending on the composition of the aluminum electrode composition. As a result, the amount of aluminum diffused into the semiconductor substrate 1 may be insufficient, and the p ⁺ -type diffusion layer may not be sufficiently formed. 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 heat treatment (firing) temperature (for example, 750 ° C. to 900 ° C.) for the aluminum electrode composition, the electrode composition is applied, and after drying, the temperature is relatively low ( For example, 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 preferably formed by heat treatment (baking) at 450 ° C. to 650 ° C., for example.
Regardless of which method is selected, the thickness of the light receiving surface collecting electrode 8 and the back surface output extraction electrode 6 obtained after the heat treatment (firing) is, for example, 3 μm to 50 μm, preferably 5 μm to 30 μm. Can do. In addition, the thickness of the layer or laminated body in this invention measures the thickness of five points of the layer or laminated body used as object, and makes it the value given as the arithmetic mean value. The 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 layer 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. When the connection material contains conductive particles, the light receiving surface collecting electrode 8 and the wiring member are formed by forming a portion in contact with the conductive particles through thermocompression bonding. Is done.

(Solar cell manufacturing process)
By using the solar cell element obtained as described above, the solar cell including the solar cell element can be obtained by further passing through 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 has 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 pressurizing 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 that can apply the above temperature and pressure to the electrode and the wiring member can be appropriately employed. 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 heat treatment (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 that has penetrated into a part corresponding to the gap part, and a wiring member are laminated on a semiconductor substrate as a wiring connection part. Have.
Due to the heat treatment (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 nonuniform 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.

The solar cell of the present invention will be described with reference to FIG. FIG. 8 is an observation cross section 100 as an example of the cross section of the electrode of the solar cell of the present invention. As shown in the observation cross section 100, a gap portion 106 exists inside the electrode 104 formed on the semiconductor substrate 102, and a part of the gap portion 106 exists in the center portion in the thickness direction of the electrode 104. is doing.

It is considered that a part of the gap 106 existing inside the electrode 104 forms an open pore, and the gap 106 communicates to the electrode surface. For this reason, when the connection material and the wiring member are arranged on the electrode 104 and pressed, the connection material enters at least a part of the gap 106 to form a resin portion. In this case, the shape of the interface between the electrode 104 and the resin portion is complicated and the contact area between the electrode 104 and the resin portion is increased as compared with the case where the gap portion 106 does not exist inside the electrode 104, and the so-called anchor effect It is considered that the adhesion between the electrode 104 and the wiring member is improved by the expression of the above. As a result, it is considered that the reliability of the solar cell is improved and further stable power generation performance is exhibited. The gap portion 106 may include a portion that does not form a resin portion without entering the connection material and exists in a void state.

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, using a surface shape measuring instrument (Mitutoyo Co., Ltd., trade name: Form Tracer SV-C3000) or the like, the surface of the electrode formed on the semiconductor substrate is laminated before or after the wiring member is laminated. 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 this invention has a solar cell obtained using the said electrode connection set, and the sealing material which has sealed the said solar cell.
In the solar cell module, for example, a plurality of the solar cells are connected in series and / or in parallel as necessary, and sandwiched with tempered glass or the like for environmental resistance, and the gap is filled with a transparent resin and sealed. The wiring member located outside the sealing portion is provided as an external terminal.

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 containing ethylene vinyl acetate (EVA). Examples of the back sheet 13 include polyethylene terephthalate (PET), Tedlar-PET laminated material, metal foil-PET laminated material, and the like.

[Method for Manufacturing Semiconductor Device]
In the method for manufacturing a semiconductor device of the present invention, an electrode is formed using the electrode connection set, and a wiring member is connected to the obtained electrode.
That is, the manufacturing method of the semiconductor device includes a step of applying the electrode composition onto a semiconductor substrate (referred to as an electrode composition applying step), and a heat treatment (firing) of the semiconductor substrate to which the electrode composition is applied. ), Forming a copper-containing electrode (referred to as an electrode forming step), laminating the connection material and the wiring member in this order on the copper-containing electrode, and obtaining a laminate (referred to as a laminating step), A step of subjecting the laminate to a heat and pressure treatment (referred to as a heat and pressure treatment step).
By the semiconductor device manufacturing method, a semiconductor device in which the electrode and the wiring member have high connection strength (adhesion) and high connection reliability can be manufactured.

[Semiconductor device]
A semiconductor device 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 portion and glass. And a portion corresponding to a void formed by heat treatment (firing) during electrode formation. The semiconductor device 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.
In this case, examples of the wiring member include a circuit member having a circuit or an electrode portion.

[Method of manufacturing electronic parts]
The manufacturing method of the electronic component of this invention forms an electrode using the said electrode connection set, and connects a wiring member to the obtained electrode.
That is, the method of manufacturing the electronic component includes a step of applying the electrode composition onto a substrate (referred to as an electrode composition application step), and a heat treatment (firing) of the substrate to which the electrode composition is applied. Then, a step of forming a copper-containing electrode (referred to as an electrode forming step), a step of stacking the connection material and the wiring member on the copper-containing electrode in this order to obtain a laminated body (referred to as a stacking step), and the lamination And a step of subjecting the body to a heat and pressure treatment (referred to as a heat and pressure treatment step).
By the method for manufacturing an electronic component, an electronic component in which the electrode and the wiring member have high connection strength (adhesion) and high connection reliability can be manufactured.

[Electronic parts]
An electronic component manufactured using the electrode connection set includes a substrate, an electrode formed on the substrate, and a wiring member disposed on the electrode. The electrode includes a metal part and a glass part. And a portion corresponding to a void formed by heat treatment (firing) during electrode formation. The electronic component has a partial structure in which a conductive layer including a metal part, a glass part, and a connection material that has penetrated into a part corresponding to the gap part and a wiring member are laminated on a substrate as a wiring connection part. ing.
In this case, examples of the wiring member include a circuit member having a circuit or an electrode portion.

The semiconductor device of the present invention can be used for various electronic devices. The semiconductor device of the present invention has excellent adhesion between the electrode and the wiring member, and is excellent in reliability. Details and preferred aspects of the configuration, materials, etc. relating to the semiconductor device of the present invention are the same as details and preferred aspects of the configuration, materials, etc. relating to the solar cell of the present invention described above.
Moreover, the electronic component of the present invention can be used for various electronic devices. The electronic component of this invention is excellent in the adhesiveness between an electrode and a wiring member, and is excellent in reliability. Details and preferred aspects of the configuration, materials, and the like relating to the electronic component of the present invention are the same as details and preferred aspects of the configuration, materials, etc. relating to the solar cell of the present invention described above.

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-tin-containing copper alloy containing 6% by mass of phosphorus and 15% by mass of tin was prepared by a conventional method, dissolved, powdered by a water atomization method, and then dried. And classified. For classification, a forced vortex classifier (turbo classifier; TC-15, Nisshin Engineering Co., Ltd.) was used. The classified powder was blended with an inert gas and subjected to deoxygenation and dehydration treatment to produce phosphorus-tin-containing copper alloy particles containing 6% by mass of phosphorus and 15% by mass of tin. The particle diameter (D50%) of the phosphorus-tin-containing copper alloy particles was 5.0 μm, and the shape thereof was substantially spherical.

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} ) 5 parts by mass and 9 parts by mass of zinc oxide (ZnO) (hereinafter, sometimes abbreviated as “G01”) were 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-tin-containing copper alloy particles and the glass particles were determined by observing them using a Hitachi High-Technologies Corporation TM-1000 scanning electron microscope. The particle sizes of the phosphorus-tin-containing copper alloy particles and glass particles were calculated using a Beckman Coulter, Inc., LS 13, 320 type laser scattering diffraction particle size distribution analyzer (measurement wavelength: 630 nm). The softening temperature and the crystallization start temperature of the glass were obtained from a differential heat (DTA) curve using a Shimadzu Corporation, DTG-60H type differential thermal-thermogravimetric simultaneous measuring device. Specifically, in the DTA curve, the softening point can be estimated from the endothermic part, and the crystallization start temperature can be estimated from the heat generating part.

72.0 parts by mass of the phosphorus-tin-containing copper alloy particles obtained above, 8.0 parts by mass of glass G01 particles, 20.0 parts by mass of diethylene glycol monobutyl ether (BC), and polyethyl acrylate (EPA) Was mixed using an automatic mortar kneader to make a paste, and an electrode composition 1 was prepared. 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 (product name: KS8200H, Hitachi Chemical Co., Ltd.) 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. Co., Ltd.), 125 g of 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. It was. Further, 56 g of Ni particles having a diameter of about 10 μm were added to the adhesive composition and stirred.

The adhesive composition obtained above was applied onto a polyethylene terephthalate film using an applicator (YOSHIMITSU SEIKI, Irie Shokai Co., Ltd.), and dried on a hot plate at a temperature of 70 ° C. for 10 minutes. A connection material 1 having a thickness of 25 μm was prepared. The thickness of the connection material was measured using a micrometer (Mitutoyo Corporation, 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 TS Instrument Japan Co., Ltd. and a shear viscometer measuring device (ARES). .

(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 Sn—Ag—Cu-based lead-free solder is plated on a single side to a thickness of 10 μm, 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 layer (silicon nitride layer) were formed on the light receiving surface was prepared, and two pieces were cut into a size of 125 mm × 125 mm. The electrode composition 1 was printed on the light receiving surface by screen printing so as to have 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 thickness of each of the light receiving surface collecting electrode and the light receiving surface output extraction electrode after heat treatment (firing) is 20 μm. The printing conditions (screen plate mesh, printing speed, printing pressure, etc.) 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, an electrode composition 1 as an electrode composition and an aluminum electrode composition (PVG Solutions Inc., PVG-AD) on a surface opposite to the light-receiving surface (hereinafter also referred to as “back surface”). −02) was printed by screen printing in the same manner as described above so as to obtain an electrode pattern as shown in FIG.
The pattern of the back surface output extraction electrode formed by using the electrode composition 1 was composed of two lines, and was printed so that the size of one line was 123 mm × 5 mm. The printing conditions (screen plate mesh, printing speed, printing pressure, etc.) were appropriately adjusted so that the back surface output extraction electrode had a thickness after heat treatment (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. Further, the printing conditions (screen plate mesh, printing speed, printing pressure, etc.) of the aluminum electrode composition were appropriately adjusted so that the thickness of the back surface collecting electrode after heat treatment (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., single row W / B tunnel furnace), heat treatment (firing) was performed at a maximum temperature of 800 ° C. and a holding time of 10 seconds (firing) in an air atmosphere. Thus, two solar cell elements 1 on which desired 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 was performed under the conditions of 180 ° C., 2 MPa, 10 seconds, and the electrode and the wiring member were connected via the connection material 1. Two solar cells 1 having a connected 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, Asahi Glass Co., Ltd.), 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 Sheets (back sheet 13) are laminated in this order, and this laminate is placed on the outside of the sealed part using a vacuum laminator (device name: LM-50 × 50, NPC Corporation). As described above, vacuum lamination was performed at a temperature of 140 ° C. for 5 minutes to produce a solar cell module 1.

(E) Cross-sectional shape of solar cell A portion (wiring connecting portion) to which the wiring member of the obtained solar cell 1 is connected is a solar cell element using an RCO-961 type diamond cutter (Refinetech Co., Ltd.). 1 and the wiring member were cut in parallel to the stacking direction. An SEM photograph of the obtained cross section was obtained using SEM (Hitachi High-Technologies Corporation, TM-1000 scanning electron microscope).
The observation cross section has a rectangular shape of 300 μm × 250 μm, where the length in the cutting direction is the height, the length in the direction parallel to the cutting direction is the width, and the area of the connection material is relative to the area of the conductive layer in the observation cross section. The observation cross section was selected to be 2% or less, or 98% or less.
In the observation cross section, the total length of the boundary line between the connection material and the electrode was measured using Adobe illustrator 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 and the structure of the solar cell 1 and the solar cell module 1 in Table 2 and Table 3, respectively. The same applies hereinafter.
In Table 2 and Table 3, “◯” in the column of “Applied electrode” means that the target electrode is used, and “-” means that the target electrode is not used. Means that. “-” In the other columns means that there is no corresponding item.

<Examples 2 to 5>
In Example 1, phosphorus content of copper alloy particles, tin content and nickel content, particle size (D50%) and content thereof, composition of nickel-containing particles, particle size (D50%) and content thereof, glass Composition 1 for electrodes except having changed the kind of particle | grain, particle diameter (D50%) and its content, the kind and content of a solvent, and the kind and content of resin as shown in Table 1. In the same manner, electrode compositions 2 to 5 were prepared.
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 weight, and was prepared as consisting of tungsten oxide (WO 3) ₅ parts by weight. The softening temperature of this glass G02 was 492 ° C., and the crystallization start temperature exceeded 650 ° C.

Then, using the obtained electrode compositions 2 to 5, respectively, except that the heat treatment (firing) conditions (maximum temperature and holding time) and the like were changed to the conditions shown in Tables 2 and 3, respectively. Thus, solar cell elements 2 to 5, solar cells 2 to 5 and solar cell modules 2 to 5 were produced, respectively.

<Example 6>
In Example 1, a solar cell 6 and a solar cell module 6 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 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 6, 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 6 was prepared in the same manner as the electrode composition 5 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 10 parts by mass of silicon dioxide (SiO ₂ ), 38 parts by mass of boron oxide (B ₂ O ₃ ), 28 parts by mass of zinc oxide (ZnO), 12 parts by mass of aluminum oxide (Al ₂ O ₃ ), and oxidation. It prepared so that it might consist of 12 mass parts of barium (BaO). 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 7 shown below was applied to form the back surface output extraction electrode. Modules 8 were produced respectively.

The electrode composition 7 was prepared in the same manner as the electrode composition 5 except that the composition of the glass particles was changed from the glass G01 to the glass G04 shown below.
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.

<Example 9>
In Example 1, an electrode composition 8 was prepared in the same manner as in Example 1 except that the solvent and the resin of the electrode composition 1 were changed as shown in Table 1. Subsequently, using this, a solar cell element 9, a solar cell 9, and a solar cell module 9 were respectively produced in the same manner as in Example 1.
The solvent Ter in the table represents terpineol, and the resin EC represents ethyl cellulose.

<Example 10>
A p-type silicon substrate having a thickness of 190 μm in which an n ⁺ -type diffusion layer, a texture, and an antireflection layer (silicon nitride layer) were 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 composition (PVG Solutions, PVG-AD-02) 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. Also, the printing conditions (screen plate mesh, printing speed, printing pressure, etc.) of the aluminum electrode composition were appropriately adjusted so that the thickness of the back surface collecting electrode after heat treatment (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) was performed at a maximum temperature of 800 ° C. and a holding time of 10 seconds (firing) in an air atmosphere. Then, a current collecting electrode on the back surface 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 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 printing conditions (screen plate mesh, The printing speed, printing pressure, etc.) were adjusted as appropriate. The pattern of the back surface output extraction electrode was 123 mm × 5 mm, and was printed in two places in total. Printing conditions (screen plate mesh, printing speed, printing pressure, etc.) were appropriately adjusted so that the thickness after heat treatment (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., 1-row transport W / B tunnel furnace), heat treatment (firing) was performed in an air atmosphere at a maximum heat treatment (firing) temperature of 650 ° C. and a holding time of 10 seconds. Two solar cell elements 10 on which desired electrodes were formed were produced. Thereafter, in the same manner as in Example 1, a solar cell 10 and a solar cell module 10 were produced.

<Example 11>
Example 10 is the same as Example 10 except that the electrode composition for forming the light receiving surface collecting electrode, the light receiving surface output extraction electrode, and the back surface output extraction electrode is changed to the electrode composition 5. Thus, two solar cell elements 11 were produced. Thereafter, in the same manner as in Example 10, a solar cell 11 and a solar cell module 11 were produced.

<Example 12>
In Example 5, the solar cell 12 and the solar cell module 12 were formed in the same manner as in Example 5 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.

<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. Then, wiring members were arranged and connected.

<Comparative example 2>
In the preparation of the electrode composition in Example 1, as shown in Table 1, an electrode composition C2 using silver particles was prepared without using copper alloy 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 and tin content of the copper alloy particles, the particle diameter (D50%) and the content thereof, the type and content of the solvent, and the type and content of the resin An electrode composition C1 was prepared in the same manner as in Example 1 except that the amount was changed as shown in Table 1.

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, the phosphorus content of the 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, the type of glass particles, the particle size (D50) %) And the content thereof, the type and content of the solvent, and the type and content of the resin were changed as shown in Table 1, and the electrode composition C3 was prepared in the same manner as in Example 1. 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 table-top peel tester (device name: EZ-S, Shimadzu Corporation) and measuring the 90 ° peel adhesion strength of the wiring member. The measurement was performed in accordance with JIS K 6854-1: 1999; 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 4.

(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 was made using simulated sunlight (device name: WXS-155S-10, Wacom Denso Co., Ltd.) and voltage-current (IV) evaluation measuring device (device name: IV CURVE TRACER MP-160, Hidehiro) The measurement device of Seiki Co., Ltd.) was used in combination. 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 JIS-C-8913: 2005 and JIS-C-8914: 2005, respectively. It was obtained by performing the measurement in conformity. The obtained measured values are shown in Table 4 in terms of relative values with the measured value of Comparative Example 1 (solar cell module C1) as 100.0.

The peel strength of the wiring members in the solar cells produced in Examples 1 to 12 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 12 was almost the same as the measured value of Comparative Example 1. In particular, the solar cell module 12 showed high power generation performance even though the light receiving surface output extraction electrode was not formed. From this, the connection material is eliminated by thermocompression bonding, and the wiring member has a portion that is in direct contact with not only the back surface output extraction electrode but also the light receiving surface current collecting electrode. It is thought that it 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. Examples 2 to 12 were the same.

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.

Note that the entire disclosures of Japanese applications 2014-017939 and 2014-017940 are incorporated herein by reference. In addition, all the documents, patent applications, and technical standards described in this specification are the same as when individual documents, patent applications, and technical standards are specifically and individually described to be incorporated by reference. Which is incorporated herein by reference.

Claims

An electrode composition comprising phosphorus-tin-containing copper alloy particles and glass particles;
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-containing particles.
3. The electrode connection set according to claim 2, wherein the nickel-containing particles are at least one selected from the group consisting of nickel particles and nickel alloy particles having a nickel content of 1% by mass or more.
The electrode connection set according to any one of claims 1 to 3, wherein the phosphorus-tin-containing copper alloy particles are phosphorus-tin-nickel-containing copper alloy particles further containing nickel.
The electrode connection set according to claim 4, wherein the phosphorus-tin-nickel-containing copper alloy particles have a phosphorus content of 2.0 mass% to 15.0 mass%.
The electrode connection set according to claim 4 or 5, wherein the phosphorus-tin-nickel-containing copper alloy particles have a tin content of 3.0 mass% to 30.0 mass%.
The electrode connection set according to any one of claims 4 to 6, wherein the phosphorus-tin-nickel-containing copper alloy particles have a nickel content of 3.0 mass% to 30.0 mass%.
The particle diameter (D50%) when the volume integrated from the small diameter side in the particle size distribution of the phosphorus-tin-containing copper alloy particles is 50% (D50%) is 0.4 μm to 10.0 μm. The electrode connection set according to claim 1.
The electrode connection set according to any one of claims 1 to 8, wherein the glass particles have a softening point of 650 ° C or lower and a crystallization start temperature exceeding 650 ° C.
The electrode connection set according to claim 9, wherein a softening point of the glass particles is 583 ° C or lower.
The electrode connection set according to any one of claims 1 to 10, wherein the glass particles contain lead (Pb).
The electrode connection set according to any one of claims 1 to 11, wherein a content ratio of the glass particles is 0.1 mass% to 12 mass%.
The electrode connection set according to any one of claims 1 to 12, 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 13, wherein the connection material further contains conductive particles.
The electrode connection set according to any one of claims 1 to 14, wherein the electrode composition further contains a dispersion medium.
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 15.
The method for manufacturing a solar cell according to claim 16, wherein the heat treatment is performed at 450 ° C to 900 ° C.
A solar cell obtained by the method for manufacturing a solar cell according to claim 16 or claim 17.
A solar cell obtained by the method for manufacturing a solar cell according to claim 16 or 17,
A sealing material sealing the solar cell;
A solar cell module.