JP2014103220A - Solar battery and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar battery including a connection structure of a copper-containing electrode and a wiring member of a solar battery element that has high intensity (favorable adhesiveness) and high reliability, and exhibiting stable power generating properties, and a solar battery module comprising the solar battery.SOLUTION: There is provided a solar battery module comprising: a solar battery including a wiring connection part in which a semiconductor substrate including a pn junction, a conductive layer including a metal part containing copper, a glass part, and a resin part, and a wiring member are stacked in this order, and having an observation cross section in which a plurality of metal parts separated by the resin part when a cross section parallel to a lamination direction of the wiring connection part is observed; and a sealing member configured to seal the solar battery by exposing the solar battery and a part of the wiring member in the solar battery.

Description

  The present invention relates to a solar cell and a solar cell module.

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

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

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

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

  In order to solve the above-mentioned problems of copper, copper particles that have been imparted with oxidation resistance using various methods and are not easily oxidized even when subjected to high-temperature firing have been reported (for example, Patent Document 1 and Patent Document 2). In addition, as a method for suppressing copper oxidation during firing, a method using an electrode paste composition (electrode composition) containing copper-containing particles and glass particles has also been reported (see, for example, Patent Document 3). ).

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

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

  Generally, solder is used for connection between the electrode of the solar cell element and the wiring member (see, for example, Patent Document 4 and Patent Document 5). Solder is widely used because it is excellent in connection reliability such as conductivity and fixing strength, is inexpensive and versatile. In recent years, lead-free solder has also become widespread as a solder used for connection between the electrode of the solar cell element and the wiring member from the environmental viewpoint.

  On the other hand, a connection method that does not use solder has also been proposed. For example, Patent Documents 6 to 8 disclose connection methods using a conductive paste.

JP 2005-314755 A Japanese Patent Laid-Open No. 2004-217952 JP 2011-171272 A JP 2004-204256 A JP-A-2005-050780 JP 2000-286436 A JP 2001-357897 A Japanese Patent No. 3448924

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 accompanying 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. Also, solder tends to have poor wettability with respect to electrodes formed using an electrode composition containing copper-containing particles and glass particles.
Furthermore, as described in Patent Documents 6 to 8, the method of connecting the electrode of the solar cell element and the wiring member using the conductive paste significantly deteriorates the power generation performance with time under high temperature and high humidity conditions. In some cases, sufficient connection reliability is not always obtained.
On the other hand, when the connection between the copper-containing electrode and the wiring member as described in Patent Document 3 is performed with solder or a conductive paste, the adhesion between the copper-containing electrode of the solar cell element and the wiring member tends to be insufficient. there were.

  This invention is made | formed in view of the said subject, The connection of a copper containing electrode and a wiring member is equipped with the structure which has high intensity | strength (good adhesiveness) and high reliability, and also shows the stable electric power generation performance. An object is to provide a solar cell and a solar cell module.

The present invention is as follows.
[1] A wiring connection portion in which a semiconductor substrate having a pn junction, a conductive layer including a metal portion including copper, a glass portion, and a resin portion, and a wiring member are stacked in this order, and the wiring connection portion When the cross section parallel to the laminating direction is observed, the solar cell has an observation cross section in which a plurality of the metal parts separated by the resin part are arranged.
[2] A wiring connection portion in which a semiconductor substrate having a pn junction, a conductive layer including a metal portion including copper, a glass portion, and a resin portion, and a wiring member are stacked in this order, and the wiring connection portion When a cross section parallel to the stacking direction is observed, a solar cell having an observation cross section that satisfies the following formula (I):
La ≧ Lb × 1.1 (I)
In the formula (I), La represents the total length (μm) of La1 to La4 below, and Lb represents the length (μm) of the observation cross section along the direction perpendicular to the stacking direction;
La1: Total length (μm) of the boundary line between the glass part and the resin part in the conductive layer;
La2: the total length (μm) of the boundary line between the metal part and the resin part in the conductive layer,
La3: the sum total of the length (μm) of the boundary line between the glass part and the wiring member in the conductive layer;
La4: The total length (μm) of the boundary line between the metal part and the wiring member in the conductive layer.
[3] The solar cell according to [1] or [2], in which the metal part includes a Cu—Sn—Ni alloy phase and the glass part includes a Sn—PO glass phase.
[4] The solar cell according to [3], wherein the Sn—PO glass phase is disposed between the Cu—Sn—Ni alloy phase and the semiconductor substrate.
[5] In any one of [1] to [4], the conductive layer is a fired product of an electrode composition including phosphorus-containing copper alloy particles, tin-containing particles, glass particles, and a dispersion medium. The solar cell described.
[6] The solar cell according to [5], wherein the electrode composition further includes nickel particles.
[7] The solar cell according to any one of [1] to [6], wherein the resin portion in the conductive layer includes an adhesive.
[8] A solar cell having the solar cell according to any one of [1] to [7] and a sealing material that seals the solar cell by exposing a part of the wiring member in the solar cell. Battery module.

  According to the present invention, the connection between the copper-containing electrode and the wiring member has a structure having high strength (good adhesion) and high reliability, and further includes a solar cell that exhibits stable power generation performance, and a solar cell module. Can be provided.

It is a figure which shows an example of the cross section of the wiring connection part of the silicon solar cell concerning this invention. It is a figure which shows an example of the process of measuring the length of La and Lb in Formula (I) using the observation cross section of the wiring connection part of the silicon solar cell concerning this invention. It is a schematic sectional drawing which shows an example of the silicon 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 silicon 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 silicon 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 silicon solar cell element concerning this invention. It is a schematic plan view which shows an example of the light-receiving surface of the silicon solar cell concerning this invention. It is a schematic plan view which shows an example of the back surface of the silicon solar cell concerning this invention. It is a schematic sectional drawing which shows an example of the structure which connected the two silicon solar cells concerning this invention. It is a figure for demonstrating an example of the manufacturing method of the silicon solar cell module concerning this invention.

The solar cell of the present invention has a wiring connection part in which a semiconductor substrate having a pn junction, a metal part containing copper, a glass part, a conductive layer containing a resin part, and a wiring member are laminated in this order, When a cross section parallel to the stacking direction of the wiring connection portion is observed, the solar cell has an observation cross section in which a plurality of the metal portions separated by the resin portion are arranged.
Moreover, the solar cell of the present invention has a wiring connection portion in which a semiconductor substrate having a pn junction, a conductive layer including a metal part including copper, a glass part, and a resin part, and a wiring member are stacked in this order. When the cross section parallel to the lamination direction of the wiring connection portion is observed, the solar cell has an observation cross section that satisfies the following formula (I).
La ≧ Lb × 1.1 (I)
In the formula (I), La represents the total length (μm) of La1 to La4 below, and Lb represents the length (μm) of the observation cross section along the direction perpendicular to the stacking direction;
La1: Total length (μm) of the boundary line between the glass part and the resin part in the conductive layer;
La2: the total length (μm) of the boundary line between the metal part and the resin part in the conductive layer,
La3: the sum total of the length (μm) of the boundary line between the glass part and the wiring member in the conductive layer;
La4: The total length (μm) of the boundary line between the metal part and the wiring member in the conductive layer.

  That is, in the solar cell of the present invention, when a cross section parallel to the lamination direction of the wiring connection portion is observed, an observation cross section in which a plurality of metal portions separated by a resin portion are arranged, or a glass portion or a metal portion and There is an observation cross section in which the boundary line with the resin portion or the wiring member is longer than the length of the observation cross section. In these observation cross sections, the metal part in contact with the resin part or the glass part, or in some cases, the metal part in contact with the wiring member shows a contour line that is bent and uneven. In the solar cell having such an observation cross section, the connection between the copper-containing electrode formed on the semiconductor substrate and the wiring member has high strength (good adhesion), has a highly reliable structure, and is more stable. Indicates power generation performance.

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. .
Further, in the present specification, “to” indicates a range including numerical values described before and after that as a minimum value and a maximum value, respectively.
Further, in the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. means.
The present invention will be described below.

One form of the solar cell of the present invention includes a wiring connection portion in which a semiconductor substrate having a pn junction, a conductive layer including a metal part including copper, a glass part, and a resin part, and a wiring member are stacked in this order. And a cross section parallel to the stacking direction of the wiring connection portion is observed, there is an observation cross section in which a plurality of the metal portions separated by the resin portion are arranged.
Here, since the plurality of metal portions in the observation cross section are separated by the resin portion, the resin portion enters between the metal portions having the curved contour lines, and as a result, between the resin portion and the metal portion. It is presumed that the strength of the mechanical adhesion of the material increases.

In the observation cross section, each of the plurality of metal parts may be in direct contact with the semiconductor substrate, or a glass part may be interposed between the semiconductor substrate and the metal part.
When the wiring connection portion is observed in a cross section, the plurality of metal portions are observed as a structure separated by the resin portion. On the other hand, when the wiring connection part is captured in three dimensions, the plurality of metal parts shown in the observation cross section and separated by the resin part correspond to a part of the continuous metal parts. For this reason, the observation cross section in which the some metal part separated by the resin part is arrange | positioned should just exist in a part of wiring connection part. The entire conductive layer preferably has a porous body-like shape in which the boundary surface between the resin portion and the metal portion is complicated from the surface side to the inside of the metal portion.

Another embodiment of the solar cell of the present invention is a wiring connection in which a semiconductor substrate having a pn junction, a conductive layer including a metal part including copper, a glass part, and a resin part, and a wiring member are laminated in this order. When a cross section parallel to the stacking direction of the parts is observed, the cross section satisfies the following formula (I).
La ≧ Lb × 1.1 (I)
In formula (I), La represents the total length (μm) of La1 to La4 below, and Lb represents the length (μm) in the surface direction of the observed cross section of the semiconductor substrate;
La1: Total length (μm) of the boundary line between the glass part and the resin part in the conductive layer;
La2: the total length (μm) of the boundary line between the metal part and the resin part in the conductive layer,
La3: the sum total of the length (μm) of the boundary line between the glass part and the wiring member in the conductive layer;
La4: The total length (μm) of the boundary line between the metal part and the wiring member in the conductive layer.

The observation cross section of the solar cell according to the above-described two forms will be described using the observation cross section shown in FIG. 1A.
FIG. 1A shows an observation cross section 100 as an example of the observation cross section of the wiring connection portion of the solar cell according to the present invention. In the observation cross section 100, the conductive layer 108 including the electrode 104 and the resin portion 106 and the wiring member 110 are stacked on the semiconductor substrate 102. The electrode 104 includes a metal part and a glass part, and a metal part or a glass part is arranged on the surface of the electrode 104 (not shown).

In the observation cross section 100, the contour line of the electrode 104 disposed between the semiconductor substrate 102 and the wiring member 110 is irregularly bent to show irregularities. At this time, the resin portion 106 enters between the plurality of electrodes 104, and as a result, the plurality of electrodes 104 are separated by the resin portion 106. Alternatively, the boundary line between the resin portion 106 and the electrode 104 corresponding to the contour line of the electrode 104 and the length of the boundary line between the wiring member 110 and the electrode 104 (see frame C in FIG. 1A), if any. The total length (when there are a plurality of each) is 1.1 times or more longer than the width L of the observation cross section 100.
Such an electrode 104 showing a concavo-convex contour has a higher strength of mechanical adhesion to the wiring member 110. For this reason, the solar cell provided with the wiring connection part which has such an observation cross section is equipped with the structure which has high connection intensity | strength (adhesion) and high connection reliability, and can show the stable electric power generation performance.

  The solar cell of the present invention having the above-mentioned predetermined observation cross section corresponds to, for example, an electrode composition containing phosphorus-containing copper alloy particles, tin-containing particles, glass particles, and a dispersion medium, and the resin portion and an adhesive. And a connection material containing the same. By applying the electrode composition onto the semiconductor substrate and firing, an electrode having the metal part and the glass part is formed, and further, the whole of the metal part is heated and pressed by overlapping the connection material. The conductive part including a glass part and a resin part can be obtained.

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

  The void portion is an open pore as viewed from the surface side of the copper-containing electrode, and may reach the Sn—PO glass phase formed on the semiconductor substrate side. In addition, it is thought that the performance (for example, volume resistivity) as an electrode and the power generation performance of a solar cell element are not lowered by including the void in the copper-containing electrode. During the heat and pressure treatment of the laminate obtained by laminating the copper-containing electrode, the connection material, and the wiring member, the copper-containing electrode having this structure and the wiring member are thermocompression bonded with the connection material including the adhesive interposed therebetween. By doing so, at least a part of the connection material enters the gap portion to form the resin portion, and a solar cell having the above-described observation cross section is obtained. In the obtained solar cell, the connection strength between the copper-containing electrode and the wiring member is improved by a so-called anchor effect in which the copper-containing electrode and the wiring member are dynamically bonded by the resin portion that has entered the gap. .

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

  Further, by using the electrode composition, 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 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 resin part (connection material) is formed between the semiconductor substrate and the wiring member. At this time, the amount (volume) of the resin portion that has entered the gap portion is increased as compared with an electrode having a small gap portion, for example, a silver electrode, and as a result, the resin portion interposed between the electrode and the wiring member is increased. The thickness is significantly reduced. In addition, since the connection material is flow-excluded during the thermocompression bonding of the wiring member, the metal portion and the wiring member are in direct contact with each other in a 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. Furthermore, it is conceivable that conductive components such as metals in the electrode and the wiring member are diffused from the contact portion, so that the contact portion is alloyed and the contact resistance is further reduced.
Hereinafter, the electrode composition and connection material that can be used in the present invention will be described.

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

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

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

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

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

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

When the Sn—PO glass phase functions as a barrier layer for preventing mutual diffusion between copper and silicon, a good ohmic contact between the electrode formed by baking and the silicon substrate can be achieved. Can think. That is, the Sn—P—O glass phase suppresses the formation of a reactant phase (Cu ₃ Si) formed when an electrode containing copper and silicon are heated in direct contact with each other, and semiconductor performance (for example, pn It is considered that good ohmic contact can be expressed while maintaining adhesion to the silicon substrate without deteriorating the bonding characteristics.
Conventionally, ohmic contact with a silicon substrate has been cited as a problem for applying copper to an electrode of a solar electronic device. The formation of Cu ₃ Si may extend to several μm from the interface of the silicon substrate, which may cause cracks on the silicon substrate side and cause performance deterioration of the solar cell element. In addition, the formed Cu ₃ Si lifts the electrode containing copper, 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 electrode composition will be described in detail.
(Phosphorus-containing copper alloy particles)
The electrode composition contains phosphorus-containing copper alloy particles. As a phosphorus-containing copper alloy, a brazing material called phosphorus copper brazing (phosphorus content: about 7% by mass or less) is known. Phosphorus copper brazing is also used as a bonding agent between copper and copper. By using phosphorous-containing copper alloy particles in the electrode composition, it is possible to utilize the reducibility of phosphorous to copper oxide and to prevent acid resistance. It is possible to form an electrode having excellent resistance and low resistivity. Furthermore, the electrode can be fired at a low temperature, and the effect that the process cost can be reduced can be obtained.

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

  Moreover, in the said composition for electrodes, the said phosphorus containing copper alloy particle may be used individually by 1 type or in combination of 2 or more types.

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

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

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

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

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

The tin-containing particles are not particularly limited as long as they contain tin. Among them, at least one selected from tin particles and tin alloy particles is preferable, and at least one selected from tin alloy particles having a tin content of 1% by mass or more is preferable. Moreover, in the said composition for electrodes, these tin-containing particles may be used individually by 1 type, and can also be used in combination of 2 or more type.
The purity of tin in the tin particles is not particularly limited. For example, the purity of the tin particles can be 95% by mass or more, preferably 97% by mass or more, and more preferably 99% by mass or more.

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

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

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

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

Although there is no restriction | limiting in particular as a particle diameter of the said tin containing particle | grain, As D50%, it is preferable that they are 0.5 micrometer-20 micrometers, it is more preferable that they are 1 micrometer-15 micrometers, and it is still more preferable that they are 5 micrometers-15 micrometers. When the thickness is 0.5 μm or more, the oxidation resistance of the tin-containing particles themselves is improved. Moreover, the contact area with the phosphorus containing copper alloy particle | grains and nickel containing particle | grains in an electrode becomes large because it is 20 micrometers or less, and reaction during baking advances effectively. The particle size of the tin-containing particles can be measured with a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
In addition, the shape of the tin-containing particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity. A spherical shape, a flat shape, or a plate shape is preferable.

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

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

The nickel-containing particles are not particularly limited as long as the particles contain nickel. Among these, at least one selected from nickel particles and nickel alloy particles is preferable, and at least one selected from nickel particles and nickel alloy particles having a nickel content of 1% by mass or more is preferable. Moreover, in the said composition for electrodes, nickel containing particle | grains may be used individually by 1 type, or can also be used in combination of 2 or more type.
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.

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

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

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

Although there is no restriction | limiting in particular as a particle diameter of the said nickel containing particle | grain, As D50%, it is preferable that they are 0.5 micrometer-20 micrometers, it is more preferable that they are 1 micrometer-15 micrometers, and it is still more preferable that they are 3 micrometers-15 micrometers. When the thickness is 0.5 μm or more, the oxidation resistance of the nickel-containing particles themselves is improved. Moreover, the contact area with phosphorus containing copper alloy particle | grains and tin containing particle | grains in an electrode becomes large because it is 20 micrometers or less, and reaction with phosphorus containing copper alloy particle | grains and tin containing particle | grains advances effectively. The particle diameter of the nickel-containing particles can be measured with a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
Further, the shape of the nickel-containing particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, etc., but from the viewpoint of oxidation resistance and resistivity, a substantially spherical shape. It is preferably flat, plate-like.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The particle diameter of the glass particles in the electrode composition is not particularly limited, but the particle diameter (D50%) when the integrated volume is 50% is preferably 0.5 μm or more and 10 μm or less. More preferably, it is 8 μm or more and 8 μm or less. When the thickness is 0.5 μm or more, workability at the production of the electrode composition is improved. Moreover, when it is 10 μm or less, it can be uniformly dispersed in the electrode composition, fire-through can be efficiently generated in the firing step, and adhesion to the silicon substrate is further improved. The particle size of the glass particles can be measured with a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
The shape of the glass particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and resistivity, It is preferably a flat shape or a plate shape.

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

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

(Dispersion medium)
The electrode composition contains a dispersion medium. Thereby, the liquid physical property (for example, a viscosity, surface tension) of the said composition for electrodes can be adjusted to the required liquid physical property according to the provision method at the time of providing to a semiconductor substrate etc.
Examples of the dispersion medium include at least one 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 and diacetone alcohol; 2,2,4-trimethyl-1,3-pentanediol monoacetate, 2,2,4-toluene Methyl-1,3-pentanediol monopropiolate, 2,2,4-trimethyl-1,3-pentanediol monobutyrate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, Ester solvents of polyhydric alcohols such as 2,2,4-triethyl-1,3-pentanediol monoacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate; polyhydric alcohols such as butyl cellosolve, diethylene glycol monobutyl ether, diethylene glycol diethyl ether Ether solvents such as α-terpinene, terpineols such as α-terpineol, pinenes such as α-pinene and β-pinene, myrcene, alloocimene, limonene, dipentene, carvone, And terpene solvents such as men and ferrandrene, and mixtures thereof.

The solvent is selected from an ester solvent of a polyhydric alcohol, a terpene solvent, and an ether solvent of a polyhydric alcohol from the viewpoint of imparting characteristics (coatability or printability) when forming the electrode composition on a semiconductor substrate. It is preferably at least one, and more preferably at least one selected from ester solvents of polyhydric alcohols and terpene solvents.
Moreover, in the said composition for electrodes, the said solvent may be used individually by 1 type or in combination of 2 or more types.

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

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

  Moreover, the weight average molecular weight of the resin in the present invention is not particularly limited. The weight average molecular weight is preferably from 5,000 to 500,000, and more preferably from 10,000 to 300,000. It 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, the particles are aggregated due to the steric repulsion when adsorbed on the phosphorus-containing copper alloy particles, tin-containing particles and nickel-containing particles added as necessary. It is thought that it can be made difficult. On the other hand, when the weight average molecular weight of the resin is 500000 or less, aggregation of the resins in the solvent is suppressed, and increase in the viscosity of the electrode composition can be suppressed. In addition, since the weight average molecular weight of the resin is 500,000 or less, it is suppressed that the combustion temperature of the resin becomes high, and the resin is not completely burned and remains as a foreign substance when the electrode composition is baked. Is suppressed, and an electrode having a lower resistivity can be formed.

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

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

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

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

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

  In the electrode composition, the flux content in the case of containing a flux effectively expresses the oxidation resistance of the phosphorus-containing copper alloy particles, and promotes the melting of the tin-containing particles and the firing of the electrode material. From the viewpoint of reducing the porosity of the part where the flux is removed at the completion, the total mass of the electrode composition is preferably 0.1% by mass to 5% by mass, and 0.3% by mass to 4% by mass. More preferably, it is more 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. It is very preferable that

(Other ingredients)
In addition to the components described above, the electrode composition may further include other components that are usually used in the technical field, if necessary. 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 said composition for electrodes. The phosphorus-containing copper alloy particles, the tin-containing particles, the glass particles, and the dispersion medium can be produced by dispersing or mixing them using a commonly used dispersion method or mixing method.
The dispersion method and the mixing method are not particularly limited, and can be appropriately selected and applied from commonly used dispersion methods and mixing methods.

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

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

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

  The conductive adhesive film described in JP 2007-214533 A includes conductive particles, and can exhibit conductivity between silicon substrates via the conductive particles during thermocompression bonding. The connection material used in the present invention is not limited to this composition, and may not contain the conductive particles. That is, when the connection material does not contain conductive particles, the copper-containing electrode and the wiring member can obtain conductivity by directly contacting the connection material at a portion where the connection material is flow-excluded by pressurization.

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

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

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

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

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

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

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

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

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

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

(Conductive particles)
The connection material can further contain conductive particles. By containing the conductive particles, the power generation performance of the solar cell module can be further improved.
The conductive particles are not particularly limited, and examples 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. Moreover, when it contains electroconductive particle, it is preferable that the particle diameter of electroconductive particle is 1 micrometer-50 micrometers, It is more preferable that they are 1 micrometer-30 micrometers, It is still more preferable that they are 1 micrometer-25 micrometers. 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 above-mentioned components, the connection material is made of a modified material such as a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, or conductive particles in order to improve adhesion or wettability. When added, in order to improve the dispersibility, a dispersing agent such as calcium phosphate or calcium carbonate, a chelate material for suppressing silver or copper migration, or the like 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>
Although the wiring member which can be used for this invention is not restrict | limited in particular, The solder-coated copper wire (tab wire) for solar cells can be used suitably. Examples of the solder composition include Sn—Pb, Sn—Pb—Ag, and Sn—Ag—Cu, etc., but considering the influence on the environment, Sn—Ag—Cu containing substantially no lead is included. It is preferable to use a system solder.

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

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

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

[Method for manufacturing solar cell]
Although the manufacturing method of the solar cell concerning this invention is demonstrated, this invention is not limited by this.
The method for manufacturing the solar cell includes a step of applying the electrode composition onto the semiconductor substrate having the pn junction (referred to as an electrode composition applying step), and a semiconductor substrate to which the electrode composition is applied. A step of forming a copper-containing electrode by heat treatment (referred to as an electrode forming step), a step of stacking the connection material and the wiring member in this order on the copper-containing electrode, and obtaining a laminate (referred to as a stacking step); It is preferable to include a step of heating and pressing the laminate (referred to as a heating and pressing 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 this specification, the solar cell element means one having a semiconductor substrate having a pn junction and an electrode formed on the semiconductor substrate.

  In the electrode composition application step, the electrode composition is applied to the 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 the electrode composition is applied 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, it is possible to ^2g / ^{m 2 ~10g} / m 2 as an electrode composition for application amount ^is preferably ^{4g / m 2 ~8g / m 2} .

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

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

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

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

Next, the light receiving surface output extraction electrode 4 and the light receiving surface current collecting electrode 8 provided on the light receiving surface side schematically shown in FIG. 3, and the current collecting electrode 5 and output formed on the back surface schematically shown in FIG. A method for forming the extraction electrode 6 will be described.
The light receiving surface output extraction electrode 4, the light receiving surface current collecting electrode 8, and the back surface output extraction electrode 6 are formed from the electrode composition. The back current collecting electrode 5 is formed of an aluminum electrode composition containing glass powder. As a first method for forming the light receiving surface output extraction electrode 4, the light receiving surface collecting electrode 8, the back surface output extracting electrode 6 and the back surface collecting electrode 5, the electrode composition and the aluminum electrode composition are used. It may be formed by applying a desired pattern by screen printing or the like and then baking and drying at about 750 ° C. to 900 ° C. in the air after drying.

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

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

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

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

  Further, as shown in the plan view of FIG. 4, 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. 4 can be manufactured in the same manner as the solar cell element having the structure shown in FIGS. This can be considered as follows, for example.

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

(Solar cell manufacturing process)
Using the solar cell element obtained as described above, a solar cell including the solar cell element is further obtained by the laminating step and the heat and pressure treatment step. In this invention, 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.
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 resin part (connection material) is interposed between the semiconductor substrate and the wiring member. . The conductive layer includes a structure in which the copper-containing electrode composed of the metal part and the glass part is in contact with the wiring member thereon, and a structure in which a part of the resin part enters the void part of the copper-containing electrode. It is preferable to do. 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 resin part enters the void part of the copper-containing electrode, Adhesion between the containing electrode and the wiring member is improved.

Next, although the specific example of the solar cell of this invention and its manufacturing method are demonstrated, referring FIGS. 6-8, 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.
As shown in FIGS. 6 to 8, the connection material 10 and the wiring member 9 are arranged in this order on the light receiving surface output extraction electrode 4 and the back surface output extraction electrode 6 to obtain a laminate (lamination process). By subjecting the laminated body to heat pressure treatment (thermocompression treatment), the light receiving surface output extraction electrode 4 and the wiring member 9 are pressure bonded, and the back surface output extraction electrode 6 and the wiring member 9 are pressure bonded to form a solar cell. Is done. When connecting a plurality of the solar cells, the wiring member 9 has a light receiving surface output extraction electrode 4 of one solar cell element at one end and a back surface output extraction electrode 6 of another solar cell element at the other end, respectively. 9 may be arranged so as to be connected via 9. In the case of manufacturing a solar cell, a solar cell element in which the light receiving surface output extraction electrode 4 is not formed can be used as shown in FIG.

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

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

[Structure of solar cell]
The solar cell includes a semiconductor substrate, an electrode formed on the semiconductor substrate, and a wiring member disposed on the electrode. The electrode is formed by firing a metal part and a glass part and forming the electrode. And a portion corresponding to the formed gap. The solar cell has a partial structure in which a conductive layer including a metal part, a glass part, and a resin part and a wiring member are stacked on a semiconductor substrate as a wiring connection part.

  As described above, the void portion of the copper-containing electrode is generated irregularly and in an arbitrary shape by firing at the time of electrode formation, and the contour of the metal portion constituting the electrode becomes an uneven shape due to the formation of the void portion. 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 (resin part) that has entered a part corresponding to the gap part is provided between the semiconductor substrate and the wiring member in the wiring connection part. It is formed. In the conductive layer, since the resin portion has intruded between the metal portion and the metal portion (in some cases, the metal portion having the glass portion on the surface) due to the generation of the void portion, the boundary surface between the wiring member and the electrode Irregular irregularities corresponding to the contour of the metal part having an uneven shape are formed. When the solar cell of such a form observes the cross section parallel to the lamination direction of a wiring connection part, a metal part (a glass part when the glass part exists in the surface of a metal part) and a resin part ( When the metal part is in direct contact with the wiring member, the boundary line with the wiring member) is irregularly bent. As a result, the plurality of metal portions are separated by the resin portion, or the relationship between the total length of these boundary lines bent irregularly and the width of the observation cross section satisfies the relationship of the formula (I) .

  In the observation cross section of the wiring connection part, the sum of the boundary lines between the metal part and the glass part (La1 in formula (I)) and the sum of the lengths (μm) of the boundary line between the metal part and the resin part (formula (I ) In La2), the total length (μm) of the boundary line between the glass part and the wiring member (La3 in the formula (I)), and the total length of the boundary line (μm) in the metal part and the wiring member The total boundary line length (μm) (La in Formula (I)) combined with (La4 in Formula (I)), and the length (μm) of the width of the observation cross section (Lb in Formula (I)) Are contrasted.

  In the solar cell of one embodiment of the present invention, in Formula (I), La is 1.1 times or more of Lb, that is, an electrode formed of a metal part and a glass part is in contact with a wiring member through a resin part. The length (La) is 1.1 times or more the width (Lb) of the observation cross section. When La is 1.1 times or more of Lb, the strength of the mechanical adhesion between the wiring member and the electrode is sufficiently obtained, and a solar cell exhibiting a desired high connection strength (adhesion) and high connection reliability is obtained. can get. From the viewpoint of connection strength and connection reliability between the wiring member and the electrode, and stable power generation efficiency, La is preferably 1.2 times or more, and more preferably 1.3 times or more of Lb.

Of the above La1 to La4, the total length La3 of the boundary line where the glass part and the wiring member in the conductive layer are in contact, and the length of the boundary line where the metal part and the wiring member in the conductive layer are in contact When the total La4 exists in the observation cross section, a numerical value indicating the length can be applied to obtain La in the formula (I), and when there is no total La4, “0” is applied to each. That's fine.
That La4 is a numerical value exceeding 0 means that the metal part and the wiring member are in direct contact. This is considered to be obtained by removing the connecting material from between the metal part and the wiring member by heat and pressure treatment. In the part where the metal part of the electrode and the wiring member are in direct contact, since the metal part and the wiring member are in a good connection state, the wiring member and the electrode are electrically connected even if the connection material does not contain conductive particles. It can be connected and is preferable. From the viewpoint of realizing a good connection between the metal part and the wiring member, for example, when the length Lb of the observation cross section is 100 μm, the length of La4 is preferably 5 μm or more, and more preferably 10 μm or more. preferable.

The observation cross section may be any cross section in the laminating direction of the wiring connecting portion in which the conductive layer including the metal part including copper, the glass part, and the resin part, and the wiring member are laminated in this order, and at least the conductive section. It is sufficient that at least a part of each of the layer, the wiring member sandwiching the layer, and the semiconductor substrate is included.
It is preferable that the observation cross section is a cross section in which a part of the wiring member can be observed as a whole and does not include a part other than the wiring connection part. Further, as the observation cross section, a cross section having an extremely small or extremely large resin portion (for example, the area of the resin portion is 2% or less or 98% or more with respect to the area of the conductive layer in the observation cross section) is excluded. Is preferred.

The observation cross section can be obtained by cutting any wiring connection portion in the solar cell by means capable of cutting in the stacking direction of each member. The means capable of cutting each member of the solar cell is not particularly limited, but the observation cross section is a cross section obtained by cutting with a RCO-961 type diamond cutter manufactured by Refine Tech. In addition, since the cut cross section by the cutting machine may remain in the observation cross section after cutting, it is preferable to polish it with abrasive paper or the like to remove surface irregularities of the observation cross section, and then use a buff or the like More preferably, the mirror-polished surface is the observation cross section.
In addition, the observation of the cut surface for obtaining the observation cross section is performed using a scanning electron microscope, preferably, imaging is performed at about 2500 times using a TM-1000 scanning electron microscope manufactured by Hitachi High-Technologies Corporation. Images can be used.

  Further, for example, two sides along a direction parallel to the stacking direction of the semiconductor substrate, conductive layer and wiring member, and two sides along a direction perpendicular to the stacking direction of the semiconductor substrate, conductive layer and wiring member. An enclosed rectangular cross section can be set as the observation cross section. In this observation cross section, the length of the side in the direction parallel to the stacking direction of the semiconductor substrate, the conductive layer, and the wiring member is “height”, and the direction perpendicular to the stacking direction of the semiconductor substrate, the conductive layer, and the wiring member is The length is “width”. The width of the observation cross section is Lb in the formula (I).

  The size of the observation cross section varies depending on the size of the solar cell. For example, the width may be 100 μm to 500 μm, and the height may be any length larger than the thickness of the conductive layer, for example, 50 μm to 500 μm. it can.

The method for measuring the length of each boundary line in the observation cross section is not particularly limited, and may be measured using an image obtained by imaging the observation cross section, and the length of the boundary line in a different region using image processing software. You may ask for it. Examples of the image processing software that can measure the length of each boundary line include Adobe illustrator CS6 (Adobe), Matrox Inspector 8.0 (Matrox), and the like. Hereinafter, the measurement method using Adobe Illustrator CS6 will be described.
When measuring the lengths of La and Lb using the Adobe illustrator CS6, as shown in FIG. 1B, the line segment corresponding to the length of the white line La is traced with the “pencil tool” and the “object tool” is used. Thus, it is possible to measure the length of the white line La. As for the length of the white line Lb, it is possible to measure the length of the white line Lb by drawing a straight line having the same length as the width of the observation section with the “straight line tool” and using the “object tool”. In FIG. 1B, the same reference numerals as those in FIG. 1A are omitted.
There is no particular limitation on the resolution when measuring the length using the image processing software, and there is no problem as long as the resolution can recognize the shape of the electrode to the extent that it can be traced with the “pencil tool”. For example, the length can be measured by magnifying the image to 10,000 to 100,000 times the actual cross section.

In the solar cell according to the present invention, the boundary surface between the resin part and the metal part (the glass part if a glass part is present on the surface of the metal part) that provides good connection strength between the electrode and the wiring member. The irregular uneven state may be specified by the surface roughness of the metal part (a glass part when a glass part is present on the surface of the metal part).
In this case, the arithmetic average roughness Ra of the surface of the metal part 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, a metal part (a glass part is present on the surface of the metal part) formed on a semiconductor substrate using a surface shape measuring instrument (manufactured by Mitutoyo Corporation, trade name: Form Tracer SV-C3000, etc. In some cases, the surface of the glass part) can be obtained by directly measuring the arithmetic average roughness Ra before the wiring member is laminated or after the laminated wiring member and the resin part are removed.

[Solar cell module]
The solar cell module of this invention has the said solar cell and the sealing material which exposed a part of said wiring member in the said solar cell, and sealed the said solar cell.
In addition, in this invention, a solar cell module means what sealed the solar cell provided with the wiring connection part as mentioned above with the sealing material, exposing a part of wiring member in a 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 for environmental resistance, and the gap is filled with a transparent resin and exposed. The thing provided with the wiring member made as an external terminal is included.

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

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

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these embodiment.

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

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

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

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

(B) Preparation of connecting material Acrylic rubber (product name: KS8200H, Hitachi Chemical Co., Ltd.) copolymerized with 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. 125 g of a company-made weight average molecular weight: 850,000) and 50 g of a phenoxy resin (product name: PKHC, Union Carbide, weight average molecular weight: 45,000) are dissolved in 400 g of ethyl acetate, and a 30% by mass solution is obtained. Obtained. Next, 325 g of a liquid epoxy resin (Novacure HX-3941HP, manufactured by Asahi Kasei E-Materials Co., Ltd., epoxy equivalent 185) containing a microcapsule-type latent curing agent is added to this solution and stirred to obtain an adhesive composition. Obtained. 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 is applied onto a polyethylene terephthalate film using an applicator (manufactured by YOSHIMITSU), and dried on a hot plate at a temperature of 70 ° C. for 10 minutes. A connection material 1 of 25 μm was produced. In addition, the film thickness of the connection material was measured using a micrometer (manufactured by Mitsutoyo Corp, ID-C112). The viscosity of the connecting material 1 was 9800 Pa · s when measured under the conditions of 25 ° C. and a frequency of 10 Hz using a shear viscometer (ARES) manufactured by Rheometric.

(C) Production of Solar Cell Element The electrode composition 1 and the connection material 1 obtained in the above (a) and (b) were prepared.
In addition, as a wiring member, a solder-plated rectangular wire for solar cells (product name: SSA-TPS L 0.2 × 1.5 (10), a copper wire having a thickness of 0.2 mm × a width of 1.5 mm, Sn-Ag— A Cu-based lead-free solder and one having a thickness of 10 μm plated on one side, manufactured by Hitachi Cable, Ltd.) were prepared.
Using these, solar cell elements were produced as follows.

First, a p-type silicon substrate having a thickness of 190 μm in which an n ⁺ -type diffusion layer, a texture, and an antireflection film (silicon nitride film) were formed on the light receiving surface was prepared, and three pieces were cut into a size of 125 mm × 125 mm. The electrode composition 1 was printed on the light receiving surface so as to have an electrode pattern as shown in FIG. 3 by using a screen printing method. The electrode pattern is composed of a light receiving surface collecting electrode having a width of 150 μm and a light receiving surface output extraction electrode having a width of 1.5 mm, and the film thickness of each of the light receiving surface collecting electrode and the light receiving surface output extraction electrode after firing is 20 μm. The printing conditions (screen plate mesh, printing speed, printing pressure) were adjusted as appropriate. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.

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

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

  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, manufactured by Nikka Engineering Co., Ltd.), thermocompression bonding was performed under conditions of 180 ° C., 2 MPa, 10 seconds, and the electrode and the wiring member were connected via the connection material 1. Three 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, manufactured by AGC), ethylene vinyl acetate ( EVA), using a back sheet, as shown in FIG. 9, glass (glass plate 11) / EVA (sealing material 12) / solar cell 1 (solar cell 14) / EVA (sealing material 12) / back sheet (Back sheet 13) are laminated in this order, and this laminate is heated to 140 ° C. using a vacuum laminator (device name: LM-50 × 50, manufactured by NP Corp.) so that a part of the wiring member is exposed. Was laminated in a vacuum for 5 minutes to produce a solar cell module 1.

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

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

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

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

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

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

  The electrode composition 8 is composed of 40.9 parts by mass of phosphorus-containing copper alloy particles (phosphorus content is 8% by mass; particle size (D50%) is 5.0 μm) and tin particles (Sn; particle size (D50%)). Is 5.0 μm), 29.8 parts by mass, Ni-6Cu-20Zn particles (particle size (D50% is 5.0 μm)) are 13.6 parts by mass, glass G03 particles are 6.8 parts by mass, diethylene glycol monobutyl ether It was prepared by mixing 19.0 parts by mass of (BC) and 6.0 parts by mass of polyethyl acrylate (EPA) and mixing them using an automatic mortar kneader to form a paste.

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

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

  Next, using a tunnel furnace (manufactured by Noritake Co., Ltd., single-row transport W / B tunnel furnace), heat treatment (firing) is performed at a firing maximum temperature of 650 ° C. and a holding time of 10 seconds in an air atmosphere to form a desired electrode. Three pieces of the solar cell elements 9 were produced. Thereafter, in the same manner as in Example 1, a solar cell 9 and a solar cell module 9 were produced.

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

<Example 11>
In Example 1, a solder-plated rectangular wire for solar cells (product name: SSA-TPS 0.2 × 1.5 (40), thickness 0.2 mm × width 1.5 mm), Sn— The solar cell 11 and the solar cell module 11 were made in the same manner as in Example 1 except that an Ag-Cu-based lead-free solder and a specification having a thickness of 40 [mu] m plated on one side were used. Produced.

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

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

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

<Example 15>
In Example 1, the solar cell 15 and the solar cell module 15 are formed in the same manner as in Example 1 except that the light receiving surface output extraction electrode is not formed and the light receiving surface electrode pattern as shown in FIG. 4 is applied. Produced.

<Example 16>
In Example 14, the solar cell 16 and the solar cell module 16 were formed in the same manner as in Example 14 except that the light receiving surface output extraction electrode was not formed and the light receiving surface electrode pattern as shown in FIG. 4 was applied. Produced.

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

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

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

<Comparative Example 3>
In the production of the solar cell in Example 1, the solar cell was formed in the same manner as in Example 1 except that the following conductive paste was used to connect the light receiving surface output extraction electrode and the back surface output extraction electrode to the wiring member. Battery C3 and solar cell module C3 were produced.
Specifically, 78.0 parts by mass of silver particles (Ag; particle size (D50%) is 3.0 μm; purity 99.8% by mass), 3.5 parts by mass of polyethylene oxythiophene, and 1. 1 of 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, and this is placed at a temperature of 150 ° C. for 15 minutes. The conductive paste was cured by heating, and the solar cell element electrode and the wiring member were connected.

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

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

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

  Next, using the obtained electrode composition C3, a solar cell element C5, a solar cell C5, and a solar cell module C5 were produced in the same manner as in Example 1.

<Evaluation>
(Cross-sectional shape)
For one of the produced solar cells, the portion to which the wiring member is connected (wiring connection portion) is laminated with the solar cell element 1 and the wiring member using an RCO-961 type diamond cutter manufactured by Refine Tech. Cut parallel to the direction. The SEM photograph of the obtained cross section was obtained using SEM (TM-1000 scanning electron microscope manufactured by Hitachi High-Technologies Corporation).
The cross section of the observation was a rectangular shape of 300 μm × 250 μm with the length in the cutting direction as the height and the length in the direction parallel to the cutting direction as the width. Thereby, Lb in the formula (I) was 250 μm. As the observation cross section for measurement, a wiring connection portion having an area ratio of 2% or less or 98% or more was selected.

  In the observation cross section, the total length of the boundary line between the connecting material and the metal part or the glass part was measured using Adobe illuminator CS6. The measurement was performed by enlarging the actual sectional view about 10,000 times. A line segment corresponding to the length of La was traced with a “pencil tool”, and the length of La was measured by using an “object tool”. As for the length of Lb, a straight line having the same length as the width of the observation cross section was drawn with the “straight line tool”, and the length of Lb was measured by using the “object tool”. La / Lb was calculated from the obtained La length and Lb length, and the results are shown in Table 2. If La / Lb ≧ 1.1, it can be said that the formula (I) is satisfied. La / Lb is a value obtained by rounding off the decimal point 2 or less.

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

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

  In the cross-sectional shapes of the solar cells produced in Examples 1 to 17, a plurality of metal parts separated by the resin part are arranged, and all of the cross-sectional shapes based on the formula (I) have La of Lb. 1.1 times or more. Further, the peel strength of the wiring member in these solar cells was higher than the measured value of Comparative Example 1. This is probably because the connecting material (resin portion) efficiently enters the void portion of the copper-containing electrode formed in the present invention, and the mechanical adhesive strength is improved by the anchor effect. On the other hand, for Comparative Example 2, it was found that the peel strength of the wiring member was lower than the measured value of Comparative Example 1. This is considered to be because the formed electrode contained almost no void portion and a sufficient anchor effect by the adhesive was not obtained.

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

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

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

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2n ⁺ Diffusion layer 3 Antireflection film 4 Light reception surface output extraction electrode 5 Back surface collection electrode 6 Back surface output extraction electrode 7 p ⁺ Diffusion layer 8 Light reception surface collection electrode 9 Wiring member 10 Connection material 11 Glass plate 12 Sealing material 13 Back sheet 14 Solar cell 100 Observation cross section 102 Semiconductor substrate 104 Electrode 106 Resin portion 108 Conductive layer 110 Wiring member

Claims (8)

a semiconductor substrate having a pn junction;
A conductive layer including a metal part including copper, a glass part, and a resin part;
A wiring member;
Have wiring connections stacked in this order,
When a cross section parallel to the stacking direction of the wiring connection portion is observed, the solar cell has an observation cross section in which a plurality of the metal portions separated by the resin portion are arranged. a semiconductor substrate having a pn junction;
A conductive layer including a metal part including copper, a glass part, and a resin part;
A wiring member;
Has a wiring connection part laminated in this order, and when a cross section parallel to the lamination direction of the wiring connection part is observed, there is an observation cross section that satisfies the following formula (I):
La ≧ Lb × 1.1 (I)
In formula (I), La represents the total length (μm) of La1 to La4 below, and Lb represents the length (μm) of the observation cross section along the direction perpendicular to the stacking direction;
La1: Total length (μm) of the boundary line between the glass part and the resin part in the conductive layer;
La2: the total length (μm) of the boundary line between the metal part and the resin part in the conductive layer,
La3: the sum total of the length (μm) of the boundary line between the glass part and the wiring member in the conductive layer,
La4: The total length (μm) of the boundary line between the metal part and the wiring member in the conductive layer.   The solar cell according to claim 1, wherein the metal part includes a Cu—Sn—Ni alloy phase, and the glass part includes a Sn—P—O glass phase.   The solar cell according to claim 3, wherein the Sn—P—O glass phase is disposed between the Cu—Sn—Ni alloy phase and the semiconductor substrate.   The conductive layer is a fired product of an electrode composition including phosphorus-containing copper alloy particles, tin-containing particles, glass particles, and a dispersion medium. Solar cells.   The solar cell according to claim 5, wherein the electrode composition further contains nickel particles.   The solar cell according to any one of claims 1 to 6, wherein the resin portion in the conductive layer contains an adhesive. The solar cell according to any one of claims 1 to 7,
A sealing material that exposes a part of the wiring member in the solar cell and seals the solar cell;
A solar cell module.