JP2013073890A - Conductive composition, solar cell, and solar cell module - Google Patents

Abstract

The present invention provides a conductive composition having good solder adhesiveness and realizing low cost.
The conductive particles (A), the solder powder (B), and the solvent (C) are contained, and 25 to 100% by mass of the conductive particles (A) is the silver-coated metal powder (a). The conductive composition whose content of the said solder powder (B) is 1-100 mass parts with respect to 100 mass parts of said conductive particles (A).
[Selection figure] None

Description

  The present invention relates to a conductive composition, a solar battery cell, and a solar battery module.

Conventionally, various conductive compositions have been used as materials that are baked to form electrodes and the like.
For example, Patent Document 1 states that “a metal material (A) having an electrical resistivity of 20 × 10 ⁻⁶ Ω · cm or less, a fatty acid silver salt (B) having one or more hydroxyl groups, and a boiling point of 200 ° C. or less. A secondary fatty acid silver salt (C) obtained by using a secondary fatty acid and a conductive composition containing the secondary fatty acid silver salt (C) "is disclosed ([Claim 1]). ] Is used ([Example] [0071]).

  Patent Document 2 discloses that “in a silver simple substance and a silver compound containing silver powder (A), silver oxide (B), and an organic solvent (D), and the silver powder (A) is contained in the composition. "Conductive composition of 50% by mass or more" has been proposed ([Claim 1]), which includes silver carboxylate as an optional component, and other additives such as glass frit and metallic additives. Aspects are described ([Claim 2] [0030] [0033] [0034] and the like).

JP 2010-92684 A JP 2011-35062 A

The conductive composition containing silver powder has a problem of high cost while having high performance such as excellent conductivity after firing, and high cost.
The inventors of the present invention have studied to reduce the cost of the conductive composition, and instead of using silver powder or a part of silver powder, silver coated metal powder such as silver coated nickel powder is used to reduce the cost. It was clarified that can be realized.

  However, when a conductive composition containing such silver-coated nickel powder is baked to form an electrode or the like, the nickel portion exposed from the gaps in the silver coat is oxidized during baking, and the adhesion to the solder The present inventors have revealed that the property (solder adhesion) is inferior.

  Then, an object of this invention is to provide the electrically conductive composition by which cost reduction was implement | achieved, having favorable solder adhesiveness.

As a result of intensive investigations to achieve the above object, the present inventor, as a result of blending a predetermined amount of solder powder into a conductive composition containing silver-coated metal powder such as silver-coated nickel powder, Was found to be satisfactory, and the present invention was completed.
That is, the present invention provides the following (1) to (7).

  (1) Containing conductive particles (A), solder powder (B), solvent (C), 25 to 100% by mass of the conductive particles (A) is silver-coated metal powder (a), and The conductive composition whose content of solder powder (B) is 1-100 mass parts with respect to 100 mass parts of said electroconductive particle (A).

  (2) The conductive composition according to (1), wherein the solder powder (B) has an average particle size of 1 to 10 μm.

  (3) The electrically conductive composition as described in said (1) or (2) whose average particle diameter of the said silver coat metal powder (a) is 1.5-20 micrometers.

  (4) In any one of the above (1) to (3), the silver-coated metal powder (a) is a silver-coated nickel powder having a silver coat of 5 to 30 parts by mass relative to 100 parts by mass of the nickel powder. The electroconductive composition as described.

  (5) Furthermore, the electroconductivity in any one of said (1)-(4) containing 1-100 mass parts organic acid silver salt (D) with respect to 100 mass parts of said electroconductive particles (A). Sex composition.

  (6) A light-receiving surface-side surface electrode, a semiconductor substrate, and a back electrode are provided, and the surface electrode and / or the back electrode uses the conductive composition according to any one of (1) to (5). A solar battery cell formed.

  (7) A solar cell module in which the solar cells according to (6) are joined in series using an interconnector whose surface is coated with solder.

  ADVANTAGE OF THE INVENTION According to this invention, the electrically conductive composition by which cost reduction was implement | achieved while having favorable solder adhesiveness can be provided.

It is a schematic cross section of a photovoltaic cell. It is the model top view seen from the surface electrode side of the photovoltaic cell, and the model bottom view seen from the back electrode side. It is the model perspective view of a solar cell module, and the expanded sectional view of a junction part.

[Conductive composition]
The conductive composition of the present invention contains (1) conductive particles (A), solder powder (B), and a solvent (C), and 25 to 100% by mass of the conductive particles (A) is silver-coated. It is a conductive composition which is a metal powder (a) and the content of the solder powder (B) is 1 to 100 parts by mass with respect to 100 parts by mass of the conductive particles (A).
Hereinafter, each component which the electrically conductive composition of this invention contains is demonstrated in detail.

[Conductive particles (A)]
The electroconductive particle (A) which the electroconductive composition of this invention contains will not be specifically limited if the 25-100 mass% is silver coat metal powder (a). Therefore, first, the silver-coated metal powder (a) will be described.

<Silver-coated metal powder (a)>
The silver-coated metal powder (a) is not particularly limited as long as at least a part of the surface of the metal powder is coated with silver. Here, as said metal powder, nickel powder, copper powder, aluminum powder, magnesium powder etc. are mentioned, for example, Nickel powder is preferable from the reason that it is hard to oxidize at the time of baking.

  In the silver-coated metal powder (a), the amount of silver coating the surface of the metal powder such as nickel powder (silver coat amount) is 5 to 30 parts by mass with respect to 100 parts by mass of the metal powder from the viewpoint of conductivity. It is preferable that it is 20-30 parts by mass.

  The silver-coated metal powder (a) is preferably one in which silver is not unevenly distributed and is uniformly distributed over the entire surface, rather than one in which silver is unevenly distributed on a part of the surface. Thereby, it becomes a silver coat metal powder with uniform conductivity. Further, the coated silver may adhere to the surface of the metal powder in the form of a dot or mesh.

  The average particle size of the silver-coated metal powder (a) is preferably 1.5 to 20 μm because the conductive composition of the present invention has excellent printability, and has a small specific surface area and is difficult to be oxidized during firing. For the reason, it is more preferably 5 to 20 μm.

In addition, in this specification, an average particle diameter means the average value of a particle diameter, and means the 50% volume cumulative diameter (D50) measured using the laser diffraction type particle size distribution measuring apparatus. In addition, when the cross section is an ellipse, the particle diameter used as the basis for calculating the average value means an average value obtained by dividing the total value of the major axis and the minor axis by 2, and when it is a regular circle, it means the diameter. .
The spherical shape refers to the shape of particles having a major axis / minor axis ratio of 2 or less.

<Silver powder>
The conductive composition of the present invention preferably contains no silver powder from the viewpoint of cost reduction, but may contain silver powder as the conductive particles (A) from the viewpoint of conductivity and the like. That is, in this case, the conductive particles (A) other than the silver-coated metal powder (a) described above are silver powder.

As the silver powder contained in the conductive composition of the present invention, the average particle diameter is preferably 0.5 to 10 μm, more preferably 0.7 to 5 μm, because the printability is improved. 1 to 3 μm is more preferable.
In addition, it is more preferable to use spherical silver powder because an electrode having a smaller volume resistivity can be formed and a photovoltaic cell with higher photoelectric conversion efficiency can be produced.
As such silver powder, commercially available products can be used. Specific examples thereof include AgC-102 (shape: spherical, average particle size: 1.5 μm, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.), AgC-103 ( Shape: spherical, average particle size: 1.5 μm, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., AG4-8F (shape: spherical, average particle size: 2.2 μm, manufactured by DOWA Electronics), AG2-1C (shape: spherical) , Average particle size: 1.0 μm, manufactured by DOWA Electronics Co., Ltd., AG3-11F (shape: spherical, average particle size: 1.4 μm, manufactured by DOWA Electronics Co., Ltd.), AgC-2011 (shape: flake shape, average particle size: 2-10 μm, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.), AgC-301K (shape: flake shape, average particle size: 3-10 μm, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.), and the like.

[Solder powder (B)]
The conductive composition of the present invention is fired later to form an electrode or the like, but at this time, a metal part such as nickel exposed from the gap of the silver coat is oxidized during firing, and is adhered to the solder. (Solder adhesion) may be inferior.
However, the conductive composition of the present invention contains 1 to 100 parts by mass of solder powder (B) with respect to 100 parts by mass of the conductive particles (A) described above, thereby suppressing deterioration of solder adhesion. Can be good.

The solder powder (B) contained in the conductive composition of the present invention is not particularly limited, and particles made of a conventionally known solder alloy can be used.
Specific examples of the solder powder (B) include tin (Sn) -lead (Pb), Sn—Ag (silver), Sn—Cu (copper), Sn—Ag—In (indium), Sn— Examples thereof include particles made of an alloy such as an Ag—Bi (bismuth) -based or Sn—Ag—Cu-based alloy. These may be used alone or in combination of two or more.
Among these, from the viewpoint of environmental protection, it is preferable to use particles made of an alloy containing no lead (lead-free) as the solder powder (B).

  The average particle size of the solder powder (B) is preferably 1 to 10 μm, and more preferably 1 to 5 μm, because it is excellent in dispersibility and printability.

  Content of solder powder (B) is not specifically limited, For example, although 1-100 mass parts is mentioned with respect to 100 mass parts of electroconductive particle (A), electroconductivity is maintained and solder adhesiveness is mentioned. Is preferably 5 to 50 parts by mass, more preferably 5 to 20 parts by mass with respect to 100 parts by mass of the conductive particles (A).

[Solvent (C)]
Although it does not specifically limit as a solvent (C) which the electrically conductive composition of this invention contains, It is preferable that it is an organic solvent whose boiling point is 200 degreeC or more. Specific examples of the organic solvent having a boiling point of 200 ° C. or more include, for example, butyl carbitol, methyl ethyl ketone, isophorone, α-terpineol, triethylene glycol, and the like. May be used in combination.
The amount of the solvent (C) is preferably 2 to 20 parts by weight, more preferably 5 to 15 parts by weight with respect to 100 parts by weight of the conductive particles (A) described above.

[Organic acid silver salt (D)]
The conductive composition of the present invention may further contain an organic acid silver salt (D).
The conductive composition of the present invention contains the solder powder (B), but when the content of the solder powder (B) increases, the volume resistivity of the electrode formed by subsequent firing is increased. It may be inferior (volume resistivity increases).
However, since the conductive composition of the present invention further contains the organic acid silver salt (D), it is possible to suppress the deterioration of the volume resistivity and obtain a good volume resistivity in the electrode.

The organic acid silver salt (D) is not particularly limited as long as it is a silver salt of an organic carboxylic acid (fatty acid). For example, the fatty acid described in paragraphs [0063] to [0068] of JP-A-2008-198595 Metal salts (particularly tertiary fatty acid silver salts), fatty acid silver salts described in paragraph [0030] of Japanese Patent No. 4482930, hydroxyl groups described in paragraphs [0029] to [0045] of JP 2010-92684 A Fatty acid silver salt having one or more, secondary fatty acid silver salt described in paragraphs [0046] to [0056] of the same publication, and carvone described in JP-A-2011-35062 [0022] to [0026] Acid silver or the like can be used.
Among these, since the printability is improved, an electrode with a small volume resistivity can be formed, and a solar cell with higher photoelectric conversion efficiency can be produced, a fatty acid silver salt having 18 or less carbon atoms ( D1), a fatty acid silver salt (D2) having at least one carboxy silver base (—COOAg) and a hydroxyl group (—OH), and a carboxy silver base (—COOAg) without a hydroxyl group (—OH). It is preferable to use at least one fatty acid silver salt selected from the group consisting of two or more polycarboxylic acid silver salts (D3).

  Here, as said fatty-acid silver salt (D2), the compound represented by either of following formula (I)-(III) is mentioned, for example.

In formula (I), n represents an integer of 0 to 2, R ¹ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ² represents an alkylene group having 1 to 6 carbon atoms. When n is 0 or 1, the plurality of R ² may be the same or different from each other. When n is 2, the plurality of R ¹ may be the same or different.
In formula (II), R ¹ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and a plurality of R ¹ may be the same or different.
In formula (III), R ¹ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ³ represents an alkylene group having 1 to 6 carbon atoms. The plurality of R ¹ may be the same or different.

  Moreover, as said polycarboxylic acid silver salt (D3), although it is a compound represented, for example by following formula (IV) is mentioned.

In the formula (IV), m represents an integer of 2 to 6, R ⁴ represents an m-valent saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms, and an m-valent unsaturated aliphatic group having 2 to 12 carbon atoms. It represents a hydrocarbon group, an m-valent alicyclic hydrocarbon group having 3 to 12 carbon atoms, or an m-valent aromatic hydrocarbon group having 6 to 12 carbon atoms. When the carbon number of R ⁴ is p, m ≦ 2p + 2.

Specific examples of the fatty acid silver salt (D1) include 2-methylpropanoic acid silver salt (also known as silver isobutyrate) and 2-methylbutanoic acid silver salt.
Specific examples of the fatty acid silver salt (D2) include 2-hydroxyisobutyric acid silver salt and 2,2-bis (hydroxymethyl) -n-butyric acid silver salt.
Specific examples of the polycarboxylic acid silver salt (D3) include 1,3,5-pentanetricarboxylic acid silver salt and 1,2,3,4-butanetetracarboxylic acid silver salt. Is done.

  In the conductive composition of the present invention, the content of the organic acid silver salt (D) is preferably 1 to 100 parts by mass, more preferably 5 to 100 parts by mass with respect to 100 parts by mass of the conductive particles (A). 5-40 mass parts is more preferable.

〔resin〕
From the viewpoint of printability, the conductive composition of the present invention may contain a resin as necessary.
Specific examples of the resin include ethyl cellulose resin, nitrocellulose resin, alkyd resin, acrylic resin, styrene resin, phenol resin and the like, and these may be used alone or in combination of two or more. May be. Among these, it is preferable to use ethyl cellulose resin from the viewpoint of thermal decomposability.
The resin may be dissolved in a solvent, and specific examples of the solvent include α-terpineol, butyl carbitol, butyl carbitol acetate, diacetone alcohol, and methyl isobutyl ketone. These may be used alone or in combination of two or more.
It is preferable that content of the said resin is 0-20 mass parts with respect to 100 mass parts of electroconductive particle (A), and it is more preferable that it is 10-20 mass parts.

[Glass frit]
The conductive composition of the present invention may contain glass frit as necessary.
The glass frit is not particularly limited and may be lead-free or lead-free, and examples thereof include lead borosilicate glass frit.
The shape of the glass frit is not particularly limited, and may be spherical or crushed powder. The average particle diameter (D50) of the spherical glass frit is preferably 0.1 to 20 μm, and more preferably 1 to 10 μm. Furthermore, it is preferable to use a glass frit having a sharp particle size distribution from which particles of 15 μm or more are removed.
The content of the glass frit is preferably 0.5 to 5 parts by mass and more preferably 2 to 5 parts by mass with respect to 100 parts by mass of the conductive particles (A).

  The manufacturing method of the electroconductive composition of this invention is not specifically limited, For example, the method of mixing the essential component mentioned above and arbitrary components using a ball mill etc. is mentioned.

[Solar cells]
Next, the solar battery cell of the present invention will be described.
The solar battery cell of the present invention comprises a surface electrode on the light-receiving surface side, a semiconductor substrate, and a back electrode, and the surface electrode and / or the back electrode is formed using the conductive composition of the present invention. It is a cell.

  The conductive composition of the present invention can also be applied to the formation of the back electrode of an all back electrode type (so-called back contact type) solar cell.

  Below, the structure of the photovoltaic cell of this invention is demonstrated using FIG. 1 and FIG. In FIG. 1, the solar cell of the present invention will be described by taking a crystalline silicon solar cell as an example. However, the present invention is not limited to this. For example, a thin-film amorphous silicon solar cell, a hybrid type (HIT) It may be a solar cell or the like.

As shown in FIG. 1, a solar cell 10 of the present invention includes a surface electrode 1 (finger electrode 1a) on the light receiving surface side, a pn junction silicon substrate 4 in which an n layer 3 and a p layer 5 are joined (hereinafter referred to as these). In addition, it is also referred to as “crystalline silicon substrate 7”) and a back electrode 6 (full surface electrode 6a). 1 is a schematic cross-sectional view taken along the line II of FIG.
Moreover, as shown in FIG. 1, it is preferable that the photovoltaic cell 10 of this invention comprises the anti-reflective film 2 in which the pyramid-like texture was formed for the reflectance reduction.

As shown in FIG. 2A, the solar battery cell 10 of the present invention includes a finger electrode 1a and a bus bar electrode 1b as the surface electrode 1 on the light receiving surface side.
Moreover, as shown in FIG. 2B and FIG. 1, the solar battery cell 10 of the present invention includes a full-surface electrode 6 a and a connecting portion 6 b as the back electrode 6.

[Front electrode / Back electrode]
As long as at least one of the front electrode and the back electrode included in the solar battery cell of the present invention is formed using the conductive composition of the present invention, the arrangement (pitch), shape, height, width of the electrode Etc. are not particularly limited.
Here, in the embodiment shown in FIGS. 1 and 2, at least the surface electrode 1 having the finger electrodes 1a and the bus bar electrodes 1b is formed using the conductive composition of the present invention.
On the other hand, the back electrode 6 may be formed using the conductive composition of the present invention, but it is preferable to form the entire surface electrode 6a with an aluminum electrode and the connection portion 6b with a silver electrode.

[Antireflection film]
The antireflection film that the solar battery cell of the present invention may have is a film (film thickness: about 0.05 to 0.1 μm) formed on a portion of the light receiving surface where the surface electrode is not formed. For example, a silicon oxide film, a silicon nitride film, a titanium oxide film, or a laminated film thereof.

[Crystal silicon substrate]
The crystalline silicon substrate included in the solar battery cell of the present invention is not particularly limited, and a known silicon substrate (plate thickness: about 100 to 450 μm) for forming a solar battery can be used. Any polycrystalline silicon substrate may be used.

The crystalline silicon substrate has a pn junction, which means that a second conductivity type light-receiving surface impurity diffusion region is formed on the surface side of the first conductivity type semiconductor substrate. When the first conductivity type is n-type, the second conductivity type is p-type. When the first conductivity type is p-type, the second conductivity type is n-type.
Here, examples of the impurity imparting p-type include boron and aluminum, and examples of the impurity imparting n-type include phosphorus and arsenic.

Although the manufacturing method of the photovoltaic cell of the present invention is not particularly limited, a wiring forming step of forming the wiring by applying the conductive composition of the present invention on a silicon substrate, and heat treating the obtained wiring to form an electrode (surface A heat treatment step of forming an electrode and / or a back electrode).
In addition, when the photovoltaic cell of this invention comprises an antireflection layer, an antireflection film can be formed by well-known methods, such as a plasma CVD method.
Below, a wiring formation process and a heat treatment process are explained in full detail.

<Wiring formation process>
The wiring formation step is a step of forming a wiring by applying the conductive composition of the present invention on a silicon substrate.
Here, specific examples of the coating method include inkjet, screen printing, gravure printing, offset printing, letterpress printing, and the like.

<Heat treatment process>
The heat treatment step is a step of obtaining a conductive wiring (electrode) by heat-treating the wiring obtained in the wiring forming step.
Here, although the said heat processing is not specifically limited, It is preferable that it is the process heated (baking) for several seconds-several tens of minutes at the temperature of 700-800 degreeC. When the temperature and time are within this range, even when an antireflection film is formed on the silicon substrate, the electrode can be easily formed by the fire-through method.

[Solar cell module]
The solar cell module of the present invention is a solar cell module in which the solar cells of the present invention are joined in series using an interconnector whose surface is coated with solder.
Below, the structure of the solar cell module of this invention is demonstrated using FIG.

As shown in FIG. 3, the solar cell module 20 of the present invention is obtained by joining solar cells 10 in series using an interconnector 8 in which the surface of a metal ribbon 8b is covered with solder 8a.
Here, specifically, for example, copper or aluminum ribbon coated with a conductive adhesive can be suitably used as the metal ribbon.
3, the bus bar electrode 1b of the front surface electrode 1 and the solder 8a of the interconnector 8 are in close contact with each other, and the connecting portion 6b of the back electrode 6 and the solder of the interconnector 8 are in contact with each other. 8a is in close contact.

  In the solar cell module of the present invention, the bus bar electrode (and the connection portion of the back electrode) is formed using the conductive composition of the present invention, so that the adhesiveness of the interconnector with the solder becomes good and easily Can be modularized.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.

(Examples 1-6, Comparative Examples 1-3)
First, the components shown in Table 1 below were added to a ball mill so as to have the composition ratio shown in Table 1 below, and these were mixed to prepare a conductive composition.

<Volume resistivity>
A coating film was formed by coating the prepared conductive composition on a silicon substrate (single crystal silicon wafer, LS-25TVA, 156 mm × 156 mm × 200 μm, manufactured by Shin-Etsu Chemical Co., Ltd. (hereinafter the same)) by screen printing.
After forming the coating film, heat treatment was performed at 780 ° C. for 60 seconds to form a conductive coating film (silver film), and then the volume resistivity of the coating film was measured using a resistivity meter (Lorestar GP, manufactured by Mitsubishi Chemical Corporation). Measurement was performed by a four-probe method. The results are shown in Table 1 below.

<Solder adhesion>
A silicon substrate was prepared, and an aluminum paste was applied to the entire back surface by screen printing and dried.
Next, each of the prepared conductive compositions was applied to the surface of the silicon substrate by screen printing to form a predetermined wiring pattern of finger electrodes and a predetermined wiring pattern of bus bar electrodes.
After wiring was formed by screen printing, a sample of a solar battery cell in which conductive wiring (finger electrodes and bus bar electrodes) was formed by baking for 60 seconds in a baking furnace at a peak temperature of 740 ° C. was produced.
A solder ribbon (composition: Sn-3Ag-0.5Cu) was mounted on the bus bar electrode of the solar cell sample produced using a soldering iron.
Thereafter, according to JIS K6850: 1999, a tensile shear test was performed at a tensile speed of 50 mm / min, and the load at break (MPa) was measured.
When the load at break is 5 MPa or more, it is evaluated as “◎” as being extremely excellent in solder adhesion, and when the load at break is 1 MPa or more, it is regarded as being excellent in solder adhesion. When the load at break was less than 1 MPa, it was evaluated as “x” as being inferior in solder adhesion. The results are shown in Table 1 below.

<Screen printability>
The prepared conductive composition was applied on a silicon substrate by screen printing to form a wiring (line width: 70 μm, length: 5 cm).
Wiring before drying (firing) formed by screen printing was observed with an optical microscope.
If none of the disconnection, meandering, blemishes, and mesh marks were confirmed, the printability was evaluated as “Good”, and if any were confirmed, the printability was inferior. It was evaluated. The results are shown in Table 1 below.

<Cost>
When at least a part of the conductive particles used for the preparation of the conductive composition is a silver-coated nickel powder or the like that is not silver powder, it is evaluated as “◯” because of low cost, and all of the conductive particles are silver powder. In this case, it was evaluated as “x” because of high cost. The results are shown in Table 1 below.

The following were used for each component in Table 1.
Silver powder: AgC-103 (shape: spherical, average particle size: 1.5 μm, manufactured by Fukuda Metal Foil Powder Industry)
Silver coated nickel powder (1.5 μm) (shape: spherical, average particle size: 1.5 μm, silver coated amount: 20 mass%, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.)
Silver coated nickel powder (5 μm) (shape: spherical, average particle size: 5 μm, silver coated amount: 20% by mass, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.)
Silver coated nickel powder (25 μm) (shape: spherical, average particle size: 25 μm, silver coated amount: 20% by mass, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.)
Solder powder: ST-3 (Sn96.5 / Ag3 / Cu0.5, shape: spherical, average particle size: 3 μm, manufactured by Mitsui Mining & Smelting Co., Ltd.)

Solvent: α-terpineol Glass frit: ST-01 (lead borosilicate glass frit, manufactured by Central Glass Co., Ltd.)
-Vehicle: EC-100FTP (ethyl cellulose resin solid content: 9%, manufactured by Nisshin Kasei Co., Ltd.)
-Organic acid silver salt: Silver salt of isobutyric acid prepared as follows First, 50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 38 g of isobutyric acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of methyl ethyl ketone (MEK) were put into a ball mill. The reaction was allowed to stir at room temperature for 24 hours. Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare white silver isobutyrate.

As is clear from the results shown in Table 1, Examples 1 to 6 were excellent in low cost and excellent in solder adhesion.
Moreover, when Example 3 and Example 4 are contrasted, Example 3 using silver coat nickel powder (5 μm) is superior to Example 4 using silver coat nickel powder (25 μm). It was.
Further, when Example 5 and Example 6 were compared, Example 6 containing silver isobutyrate obtained better volume resistivity than Example 5 containing no isobutyric acid.
On the other hand, the comparative example 1 which uses only silver powder as electroconductive particle was high cost. Further, Comparative Examples 2 and 3 do not correspond to the conductive composition of the present invention because they do not contain solder powder, but both of them were inferior in solder adhesion.

DESCRIPTION OF SYMBOLS 1 Front electrode 1a Finger electrode 1b Bus bar electrode 2 Antireflection film 3 N layer 4 Pn junction silicon substrate 5 P layer 6 Back electrode 6a Whole surface electrode (aluminum electrode)
6b Connection part (silver electrode)
7 Crystalline silicon substrate 8 Interconnector 8a Solder 8b Metal ribbon 10 Solar cell 20 Solar cell module

Claims (7)

Contains conductive particles (A), solder powder (B), solvent (C),
25-100 mass% of the conductive particles (A) is silver-coated metal powder (a),
The conductive composition whose content of the said solder powder (B) is 1-100 mass parts with respect to 100 mass parts of said conductive particles (A).   The conductive composition according to claim 1, wherein the solder powder (B) has an average particle diameter of 1 to 10 μm.   The electrically conductive composition of Claim 1 or 2 whose average particle diameter of the said silver coat metal powder (a) is 1.5-20 micrometers.   The electrically conductive composition in any one of Claims 1-3 whose said silver coat metal powder (a) is silver coat nickel powder which has 5-30 mass parts silver coat with respect to 100 mass parts of nickel powder. .   Furthermore, the electroconductive composition in any one of Claims 1-4 containing 1-100 mass parts organic acid silver salt (D) with respect to 100 mass parts of said electroconductive particles (A). It comprises a surface electrode on the light receiving surface side, a semiconductor substrate and a back electrode,
The photovoltaic cell in which the said surface electrode and / or the said back surface electrode are formed using the electrically conductive composition in any one of Claims 1-5.   The solar cell module which joined the solar cell of Claim 6 in series using the interconnector by which the surface was coat | covered with the solder.