WO2014203897A1

WO2014203897A1 - Electrically conductive composition and solar cell

Info

Publication number: WO2014203897A1
Application number: PCT/JP2014/066041
Authority: WO
Inventors: 奈央佐藤; 石川　和憲
Original assignee: 横浜ゴム株式会社
Priority date: 2013-06-19
Filing date: 2014-06-17
Publication date: 2014-12-24
Also published as: KR20160021178A; JPWO2014203897A1; TW201516093A

Abstract

The objective of the present invention is to provide: an electrically conductive composition that is able to form an electrode or the like having a low volume resistivity; and a solar cell that uses same in a collecting electrode. The electrically conductive composition has a copper powder (A), a fatty acid silver salt (B), and a thermosetting resin (C), wherein the difference between the pyrolysis start temperature and the pyrolysis peak temperature of the fatty acid silver salt (B) is at least 40°C, and the fatty acid silver salt (B) content is 20-100 parts by mass for every 100 parts by mass of the copper powder (A) when converted from the fatty acid silver salt (B) to the amount of generated silver.

Description

Conductive composition and solar battery cell

The present invention relates to a conductive composition and a solar battery cell using the same as a collecting electrode.

Conventionally, conductive particles such as silver particles, binders made of thermoplastic resin (eg, acrylic resin, vinyl acetate resin, etc.) or thermosetting resin (eg, epoxy resin, unsaturated polyester resin, etc.), organic solvent, curing A conductive paste (conductive composition) obtained by adding and mixing an agent, a catalyst, etc., is printed on a substrate (for example, a silicon substrate, an epoxy resin substrate, etc.) in a predetermined pattern, and these are heated. There are known methods for forming electrodes and wiring and manufacturing solar cells and printed wiring boards.

For example, in Patent Document 1, “in a metal fine particle ink paste containing metal fine particles and a dispersion medium, the ink paste is applied to a glass substrate surface-treated with epoxy silane, and then baked at 180 ° C. for 10 minutes. The fine metal particle ink paste in which the electric conductivity of the formed thin film having a thickness of 10 μm is 10 ⁴ S / cm or more ”is described ([Claim 1]), and includes“ fatty acid silver salt ”as an organometallic compound. ([Claim 2], [Claim 6], [Claim 8]) and “silver and / or copper fine particles” are used as the metal fine particles ([Claim 11]).

In addition, by the present applicant, in Patent Document 2, “a conductive composition containing silver powder (A), a fatty acid silver salt (B), a resin (C), and a solvent (D), The fatty acid silver salt (B) is a compound having one carboxy silver base (—COOAg) and one or two hydroxyl groups (—OH), and the content of silver oxide is the solvent (D) A conductive composition that is 10 parts by mass or less with respect to 100 parts by mass has been proposed ([Claim 1]).

JP 2008-198595 A JP 2012-023095 A

However, when the copper fine particles are employed as the metal fine particles in the metal fine particle ink paste described in Patent Document 1, or when the silver powder of the conductive composition described in Patent Document 2 is changed to copper powder, the copper particles It has been clarified that the volume resistivity of formed electrodes and wirings (hereinafter also referred to as “electrodes”) may be increased depending on the usage environment due to oxidation of at least a part of the surface of the electrode. .

Therefore, an object of the present invention is to provide a conductive composition capable of forming an electrode or the like having a low volume resistivity and a solar battery cell using the same as a collecting electrode.

As a result of intensive studies to solve the above problems, the present inventors have found that in a conductive composition containing copper powder, a fatty acid silver salt and a thermosetting resin, there is a difference between the thermal decomposition peak temperature and the thermal decomposition start temperature. By using a specific amount of fatty acid silver salt at 40 ° C. or higher, it was found that the volume resistivity of the formed electrode or the like was lowered, and the present invention was completed.
That is, the present inventors have found that the above problem can be solved by the following configuration.

(1) A conductive composition comprising copper powder (A), a fatty acid silver salt (B), and a thermosetting resin (C),
The difference between the thermal decomposition peak temperature of the fatty acid silver salt (B) and the thermal decomposition start temperature is 40 ° C. or higher,
The content of the fatty acid silver salt (B) is 20 to 100 parts by mass with respect to 100 parts by mass of the copper powder (A) in terms of the amount of silver produced from the fatty acid silver salt (B). Conductive composition.
(2) The conductive composition according to (1), wherein the content of the thermosetting resin (C) is 1 to 50 parts by mass with respect to 100 parts by mass of the copper powder (A).

(3) A solar battery cell using the conductive composition according to (1) or (2) above as a collecting electrode.
(4) The solar battery cell according to (3), wherein a transparent conductive layer is provided as a base layer of the current collecting electrode.
(5) A solar cell module using the solar cell according to (3) or (4).

As shown below, according to the present invention, it is possible to provide a conductive composition capable of forming an electrode or the like having a low volume resistivity, and a solar battery cell using the same as a collecting electrode.
Further, by using the conductive composition of the present invention, an electrode having a low volume resistivity can be formed even when firing at a low temperature to a medium temperature (less than 450 ° C.), particularly at a low temperature (about 150 to 350 ° C.). Therefore, the solar cell (especially the second preferred embodiment described later) has an effect of reducing damage caused by heat, which is very useful.
Furthermore, if the conductive composition of the present invention is used, an electronic circuit, an antenna, etc. not only on a material having high heat resistance such as indium tin oxide (ITO) or silicon but also on a material having low heat resistance such as PET film. This circuit is very useful because it can be manufactured easily and in a short time.

FIG. 1 is a cross-sectional view showing a first preferred embodiment of a solar battery cell. FIG. 2 is a cross-sectional view showing a second preferred embodiment of the solar battery cell.

[Conductive composition]
The conductive composition of the present invention is a conductive composition having copper powder (A), a fatty acid silver salt (B), and a thermosetting resin (C).
Moreover, the electrically conductive composition of this invention may contain a hardening | curing agent (D), when an epoxy resin is used as a thermosetting resin (C).
Moreover, the electrically conductive composition of this invention may contain the solvent (E) as needed from viewpoints of printability etc. so that it may mention later.

In the present invention, by using a specific amount of the fatty acid silver salt (B) having a difference between the thermal decomposition peak temperature and the thermal decomposition starting temperature of 40 ° C. or higher, an electrode having a low volume resistivity can be formed. Composition.
This is not clear in detail, but is estimated to be as follows.
That is, by using the fatty acid silver salt (B) having a difference between the thermal decomposition peak temperature and the thermal decomposition starting temperature of 40 ° C. or more, silver is produced from the fatty acid silver salt in a wide temperature range, and the silver is the surface of the copper particles. It is considered that the surface oxidation of the copper particles could be suppressed by efficiently covering the surface.
On the other hand, when a fatty acid silver salt having a difference between the pyrolysis peak temperature and the pyrolysis start temperature of less than 40 ° C. is used, silver is instantly formed, and therefore the surface of the copper particles can be coated only locally. It was not possible to suppress the oxidation. This is also inferred from the results shown in the comparative examples described later.

Hereinafter, the copper powder (A), the fatty acid silver salt (B), the thermosetting resin (C), and the curing agent (D) and the solvent (E) which may be optionally contained will be described in detail.

<Copper powder (A)>
The copper powder (A) used in the conductive composition of the present invention is not particularly limited, and those blended with conventionally known conductive pastes can be used.

The copper powder (A) preferably has an average particle diameter of 1.0 to 20 μm because it has good printability and can form an electrode having a smaller volume resistivity. It is more preferably 0 to 10 μm.
Here, the average particle diameter means an average value of the particle diameters, and is measured by using a laser diffraction / scattering type particle size distribution measuring apparatus, and the 50% volume cumulative diameter (D50) calculated using the particle diameter standard as the number is used. Say. In addition, when the cross-section of the copper powder is elliptical, the particle diameter that is the basis for calculating the average value is the average value obtained by dividing the total value of the major axis and the minor axis by 2, and when it is a perfect circle, Refers to the diameter.

In the present invention, a commercially available product can be used as such copper powder (A). Specific examples thereof include Cu-HWQ (average particle size: 3.0 μm, manufactured by Fukuda Metal Foil Powder Co., Ltd.), FCC. -TBX (average particle size: 5.05 μm, manufactured by Fukuda Metal Foil Powder Co., Ltd.)

<Fatty acid silver salt (B)>
The fatty acid silver salt (B) used in the conductive composition of the present invention is a fatty acid silver salt in which the difference between the thermal decomposition peak temperature and the thermal decomposition start temperature is 40 ° C. or higher.
Here, the pyrolysis peak temperature is a value measured in the temperature range from room temperature to 300 ° C. in the air at a temperature rising rate of 5 ° C./min using a differential thermal-thermogravimetric simultaneous measurement device (TG-DTA). The exothermic peak temperature appearing in the DTA curve.
The pyrolysis start temperature is measured in the temperature range from room temperature to 300 ° C. in the air at a temperature rising rate of 5 ° C./min using a differential thermal-thermogravimetric simultaneous measurement device (TG-DTA). The temperature when the decrease starts.
By using such a fatty acid silver salt (B), as described above, the production of silver derived from the reduction of the fatty acid silver salt (B) occurs in a wide temperature range, and the surface of the copper powder (A) described above is obtained. It is thought that it can coat | cover efficiently.
In addition, the fatty acid silver salt (B) has a difference between the thermal decomposition peak temperature and the thermal decomposition starting temperature of 100 ° C. or more because it can form an electrode having a low volume resistivity after the wet heat test. The temperature is preferably 100 to 130 ° C. This is presumably because the surface of the copper powder (A) could be more efficiently coated with silver derived from the reduction of the fatty acid silver salt (B).

The fatty acid silver salt (B) is not particularly limited as long as the difference between the thermal decomposition peak temperature and the thermal decomposition start temperature is 40 ° C. or higher among the silver salts of organic carboxylic acids. For example, JP-A-2008-198595 Fatty acid metal salts (particularly tertiary fatty acid silver salts) described in paragraphs [0063] to [0068] of the gazette, fatty acid silver described in paragraph [0030] of Japanese Patent No. 4482930, JP 2010-92684 A Secondary fatty acid silver salts described in the paragraphs [0046] to [0056] of the above can be used.

Specific examples of the fatty acid silver salt (B) include, for example, silver stearate, silver n-butyrate, silver 2-ethylhexanoate, silver 2-methylpropanoate (also known as silver isobutyrate) ), Lauric acid silver salt, 2-ethylbutyric acid silver salt, neodecanoic acid silver salt, glutaric acid silver salt, azelaic acid silver salt, 1,2,3,4-butanetetracarboxylic acid silver salt, 4-cyclohexene-1, Examples include 2-dicarboxylic acid silver salt.
In addition, the thermal decomposition start temperature and thermal decomposition peak temperature of these specific examples are as shown in Table 1 below.

In the present invention, the content of the fatty acid silver salt (B) is 20 to 100 with respect to 100 parts by mass of the copper powder (A) in terms of the amount of silver produced from the fatty acid silver salt (B). Parts by mass, preferably 30 to 100 parts by mass, and more preferably 40 to 100 parts by mass.

<Thermosetting resin (C)>
The thermosetting resin (C) used in the conductive composition of the present invention is not particularly limited, and specific examples thereof include an epoxy resin, a polyester resin, a silicone resin, a urethane resin, and the like. You may use, and may use 2 or more types together.
Among these, an epoxy resin is preferable because it has a strong adhesion to a silicon substrate and high heat and humidity resistance.

(Epoxy resin)
The epoxy resin as a suitable example of the thermosetting resin (C) is not particularly limited as long as it is a resin composed of a compound having two or more oxirane rings (epoxy groups) in one molecule. The equivalent is 90-2000.
A conventionally well-known epoxy resin can be used as such an epoxy resin.
Specifically, for example, epoxy compounds having a bisphenyl group such as bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AF type, biphenyl type, and polyalkylene Bifunctional glycidyl ether type epoxy resins such as glycol type, alkylene glycol type epoxy compounds, epoxy compounds having a naphthalene ring, and epoxy compounds having a fluorene group;
Polyfunctional glycidyl ether type epoxy resins such as phenol novolac type, orthocresol novolak type, trishydroxyphenylmethane type, tetraphenylolethane type;
Glycidyl ester epoxy resins of synthetic fatty acids such as dimer acid;
N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane (TGDDM), tetraglycidyldiaminodiphenylsulfone (TGDDS), tetraglycidyl-m-xylylenediamine (TGMXDA), triglycidyl-p-aminophenol, triglycidyl- Glycidylamine epoxy resins such as m-aminophenol, N, N-diglycidylaniline, tetraglycidyl 1,3-bisaminomethylcyclohexane (TG1,3-BAC), triglycidyl isocyanurate (TGIC);
Tricyclo [5,2,1,0 ^2,6] epoxy compound having a decane ring, specifically, for example, after polymerizing the cresols or phenols such as dicyclopentadiene and cresol are reacted with epichlorohydrin Epoxy compounds obtainable by known production methods;
An alicyclic epoxy resin; an epoxy resin represented by Toray Rethiokol's Flep 10 epoxy resin having a sulfur atom in the main chain; a urethane-modified epoxy resin having a urethane bond; polybutadiene, liquid polyacrylonitrile-butadiene rubber or acrylonitrile butadiene rubber Examples thereof include a rubber-modified epoxy resin containing (NBR).

These epoxy resins may be used alone or in combination of two or more.
Of these, bisphenol A type epoxy resins and bisphenol F type epoxy resins are preferable from the viewpoints of curability, heat resistance, durability, and cost.

In the present invention, the content of the thermosetting resin (C) is 1.0 to 100 parts by mass with respect to 100 parts by mass of the copper powder (A) because the volume resistivity of the formed electrode or the like is lower. The amount is preferably 50 parts by mass, more preferably 2 to 25 parts by mass.

<Curing agent (D)>
When using an epoxy resin as the thermosetting resin (C), the conductive composition of the present invention preferably contains a curing agent (D) composed of a complex of boron trifluoride and an amine compound.
As a complex of boron trifluoride and an amine compound, a complex of boron trifluoride and an aliphatic amine (aliphatic primary amine, aliphatic secondary amine, aliphatic tertiary amine), trifluoride Examples thereof include a complex of boron and an alicyclic amine, a complex of boron trifluoride and an aromatic amine, a complex of boron trifluoride and a heterocyclic amine, and the like. The heterocyclic amine may be an alicyclic heterocyclic amine (hereinafter also referred to as an alicyclic heterocyclic amine) or an aromatic heterocyclic amine (hereinafter also referred to as an aromatic heterocyclic amine). Also good.
Specific examples of the aliphatic primary amine include methylamine, ethylamine, n-propylamine, iso-propylamine, n-butylamine, iso-butylamine, sec-butylamine, n-hexylamine, n-octylamine, 2 -Ethylhexylamine, laurylamine and the like. Specific examples of the aliphatic secondary amine include dimethylamine, diethylamine, methylethylamine, methylpropylamine, di-iso-propylamine, di-n-propylamine, ethylpropylamine, di-n-butylamine, di- Examples include iso-butylamine, dipropenylamine, chlorobutylpropylamine, di (chlorobutyl) amine, di (bromoethyl) amine and the like. Specific examples of the aliphatic tertiary amine include trimethylamine, triethylamine, tributylamine, triethanolamine and the like. Specific examples of the alicyclic amine include cyclohexylamine. Examples of aromatic amines include benzylamine. Specific examples of the alicyclic heterocyclic amine include pyrrolidine, piperidine, 2-pipecoline, 3-pipecoline, 4-pipecoline, 2,4-lupetidine, 2,6-lupetidine, 3,5-lupetidine, piperazine, and homopiperazine. N-methylpiperazine, N-ethylpiperazine, N-propylpiperazine, N-methylhomopiperazine, N-acetylpiperazine, 1- (chlorophenyl) piperazine, N-aminoethylpiperidine, N-aminopropylpiperidine, N-aminoethyl Piperazine, N-aminopropylpiperazine, morpholine, N-aminoethylmorpholine, N-aminopropylmorpholine, N-aminopropyl-2-pipecholine, N-aminopropyl-4-pipecholine, 1,4-bis (aminopropyl) piperazine , Triethylenediamine , 2-methyl-triethylene Chie diamine and the like. Specific examples of the aromatic heterocyclic amine include pyridine, pyrrole, imidazole, pyridazine, pyrimidine, quinoline, triazine, tetrazine, isoquinoline, quinazoline, naphthyridine, pteridine, acridine, phenazine and the like.

The curing agent (D) is selected from the group consisting of boron trifluoride piperidine, boron trifluoride ethylamine, and boron trifluoride triethanolamine because the volume resistivity of the formed electrode or the like is lower. A complex is preferred.

The content of the curing agent (D) is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the epoxy resin, because the volume resistivity of the formed electrode or the like becomes lower. It is more preferable that it is 10 mass parts.

<Solvent (E)>
The conductive composition of the present invention preferably contains a solvent (E) from the viewpoint of workability such as printability.
The solvent (E) is not particularly limited as long as it can apply the conductive composition of the present invention onto a substrate. Specific examples thereof include butyl carbitol, methyl ethyl ketone, isophorone, α-terpineol. These may be used, and these may be used alone or in combination of two or more.

<Additives>
The electrically conductive composition of this invention may contain additives, such as a reducing agent, as needed.
Specific examples of the reducing agent include ethylene glycols.

<Method for producing conductive composition>
The manufacturing method of the electrically conductive composition of this invention is not specifically limited, The said copper powder (A), the said fatty acid silver salt (B), the said thermosetting resin (C), and the said hardening | curing agent which may be contained if desired. (D), the method of mixing the said solvent (E), an additive, etc. with a roll, a kneader, an extruder, a universal stirrer etc. is mentioned.

[Solar cells]
The solar battery cell of the present invention is a solar battery cell using the above-described conductive composition of the present invention as a collecting electrode.

<First preferred embodiment of solar cell>
As a 1st suitable aspect of the photovoltaic cell of this invention, it comprises the surface electrode by the side of a light-receiving surface, a semiconductor substrate, and a back electrode, The said surface electrode and / or the said back electrode are the electroconductivity of this invention mentioned above. A solar battery cell formed using the composition can be mentioned.
Below, the 1st suitable aspect of the photovoltaic cell of this invention is demonstrated using FIG.

As shown in FIG. 1, the solar cell 1 includes a surface electrode 4 on the light receiving surface side, a pn junction silicon substrate 7 in which a p layer 5 and an n layer 2 are joined, and a back electrode 6.
As shown in FIG. 1, the solar battery cell 1 is preferably provided with an antireflection film 3, for example, by etching the wafer surface to form a pyramidal texture in order to reduce reflectivity.
Below, the said surface electrode, back surface electrode, silicon substrate which the 1st suitable aspect of the photovoltaic cell of this invention comprises, and the said antireflection film which may be equipped are explained in full detail.

(Front electrode / Back electrode)
As long as any one or both of the front electrode and the back electrode are formed using the conductive composition of the present invention, the arrangement (pitch), shape, height, width and the like of the electrode are not particularly limited. The height of the electrode is usually designed to be several to several tens of μm, but the ratio of the height and width of the cross section of the electrode formed using the conductive composition of the present invention (height / width) (below) , “Aspect ratio”) can be adjusted to a large value (for example, about 0.4 or more).
Here, as shown in FIG. 1, the front surface electrode and the back surface electrode usually have a plurality, but, for example, only a part of the plurality of surface electrodes is formed of the conductive composition of the present invention. Alternatively, part of the plurality of front surface electrodes and part of the plurality of back surface electrodes may be formed of the conductive composition of the present invention.

(Antireflection film)
The antireflection film 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 It is comprised from a film | membrane, these laminated films, etc.

The 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.

(Silicon substrate)
The silicon substrate is not particularly limited, and a known silicon substrate (plate thickness: about 80 to 450 μm) for forming a solar cell can be used, and either a monocrystalline or polycrystalline silicon substrate can be used. Good.

In the first preferred embodiment of the solar battery cell of the present invention, the solar battery cell has a large electrode aspect ratio because the surface electrode and / or the back electrode is formed using the conductive composition of the present invention. The electromotive force generated by light reception can be efficiently taken out as a current.

In addition, since the conductive composition of the present invention described above can also be applied to the formation of the back electrode of an all-back electrode type (so-called back contact type) solar cell, it can also be applied to an all-back electrode type solar cell. Can do.

<The manufacturing method of a photovoltaic cell (1st suitable aspect)>
Although the manufacturing method of the said photovoltaic cell (1st suitable aspect) is not specifically limited, The wiring formation process which apply | coats the electrically conductive composition of this invention on a silicon substrate, and forms wiring, and the formed wiring And a heat treatment step of forming an electrode (front electrode and / or back electrode) by heat treatment.
In the case where the solar battery cell includes an antireflection layer, the antireflection film can be formed by a known method 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 forming a conductive wiring (electrode) by heat-treating the coating film formed in the wiring forming step.
By heat-treating the wiring, when the silver decomposed from the fatty acid silver salt (B) melts, the wiring is connected while covering the surface of the copper powder (A), thereby forming an electrode.

The heat treatment is not particularly limited, but is preferably a treatment in which heating (firing) is performed at a relatively low temperature of 150 to 350 ° C. for several seconds to several tens of minutes. When the temperature and time are within this range, an electrode can be easily formed even when an antireflection film is formed on a silicon substrate.
Further, in the first preferred embodiment of the solar battery cell of the present invention, since the conductive composition of the present invention is used, good heat treatment (firing) can be achieved even at a relatively low temperature of 150 to 350 ° C. ) Can be applied.
In the present invention, since the wiring formed in the wiring formation step can form electrodes even by irradiation with ultraviolet rays or infrared rays, the heat treatment step may be performed by irradiation with ultraviolet rays or infrared rays.

<The 2nd suitable aspect of a photovoltaic cell>
As a second preferred embodiment of the solar battery cell of the present invention, an amorphous silicon layer and a transparent conductive layer (for example, TCO) are provided above and below an n-type single crystal silicon substrate, and the transparent conductive layer is disposed below. Examples of the base layer include a solar cell (for example, a heterojunction solar cell) cell in which a collecting electrode is formed on the transparent conductive layer using the conductive composition of the present invention described above. The solar battery cell (second preferred embodiment) is a solar battery cell in which single crystal silicon and amorphous silicon are hybridized and exhibits high conversion efficiency.
Below, the 2nd suitable aspect of the photovoltaic cell of this invention is demonstrated using FIG.

As shown in FIG. 2, the solar battery cell 100 has an n-type single crystal silicon substrate 11 as a center, i-type amorphous silicon layers 12 a and 12 b, and p-type amorphous silicon layers 13 a and n-type amorphous silicon layers above and below it. 13b, transparent conductive layers 14a and 14b, and current collecting electrodes 15a and 15b formed using the above-described conductive composition of the present invention.

The n-type single crystal silicon substrate is a single crystal silicon layer doped with an n-type impurity. Impurities that give n-type are as described above.
The i-type amorphous silicon layer is an undoped amorphous silicon layer.
The p-type amorphous silicon is an amorphous silicon layer doped with an impurity imparting p-type. Impurities that give p-type are as described above.
The n-type amorphous silicon is an amorphous silicon layer doped with an n-type impurity. Impurities that give n-type are as described above.
The said collector electrode is a collector electrode formed using the electrically conductive composition of this invention mentioned above. A specific aspect of the current collecting electrode is the same as that of the front surface electrode or the back surface electrode described above.

(Transparent conductive layer)
Specific examples of the material for the transparent conductive layer include single metal oxides such as zinc oxide, tin oxide, indium oxide, and titanium oxide, indium tin oxide (ITO), indium zinc oxide, indium titanium oxide, tin cadmium oxide, Various metal oxides such as gallium-doped zinc oxide, aluminum-doped zinc oxide, boron-doped zinc oxide, titanium-doped zinc oxide, titanium-doped indium oxide, zirconium-doped indium oxide, and fluorine-doped tin oxide. Can be mentioned.

<The manufacturing method of a photovoltaic cell (2nd suitable aspect)>
The method for producing the solar battery cell (second preferred embodiment) is not particularly limited, and can be produced by, for example, the method described in JP 2010-34162 A.
Specifically, the i-type amorphous silicon layer 12a is formed on one main surface of the n-type single crystal silicon substrate 11 by a PECVD (plasma enhanced chemical vapor deposition) method or the like. Further, a p-type amorphous silicon layer 13a is formed on the formed i-type amorphous silicon layer 12a by PECVD or the like.
Next, an i-type amorphous silicon layer 12b is formed on the other main surface of the n-type single crystal silicon substrate 11 by PECVD or the like. Further, an n-type amorphous silicon layer 13b is formed on the formed i-type amorphous silicon layer 12b by PECVD or the like.
Next, transparent conductive layers 14a and 14b such as ITO are formed on the p-type amorphous silicon layer 13a and the n-type amorphous silicon layer 13b by sputtering or the like.
Next, the conductive composition of the present invention is applied on the formed transparent conductive layers 14a and 14b to form wirings, and the formed wirings are heat-treated to form current collecting electrodes 15a and 15b.
The method for forming the wiring is the same as the method described in the wiring formation step of the above-described solar battery cell (first preferred embodiment).
The method of heat-treating the wiring is the same as the method described in the heat treatment step of the above-described solar battery cell (first preferred embodiment), but the heat treatment temperature (firing temperature) is preferably 150 to 200 ° C.

Hereinafter, the conductive composition of the present invention will be described in detail using examples. However, the present invention is not limited to this.

(Examples 1 to 17, Comparative Examples 1 to 6)
The copper powder etc. which are shown in the following 2nd table | surface were mix | blended so that it might become a composition ratio (mass part) shown in the following 2nd table | surface, and the electroconductive composition was prepared by mixing these.

<Volume resistivity (specific resistance)>
Each prepared electrically conductive composition was apply | coated by screen printing on the ITO vapor deposition glass substrate which is TCO, and the test pattern which is a solid coating of 25 mm x 25 mm was formed. It dried for 30 minutes at 200 degreeC in oven, and produced the electroconductive film.
About each produced conductive film, the volume resistivity immediately after production (initial stage) and after leaving it to stand at 85 ° C. and 85% humidity for 500 hours (after the moist heat resistance test) was measured with a resistivity meter (Lorestar GP, Mitsubishi Chemical Corporation). Measured by a 4-terminal 4-probe method using The results are shown in Table 2 below.

<Adhesion>
The evaluation of the adhesion of each formed conductive film to the substrate was performed by a grid peel test. The results are shown in Table 2 below.
Specifically, on each of the obtained substrates with conductive coating, 100 1 mm bases (10 × 10) were made, and cellophane adhesive tape was completely attached on the bases and rubbed 10 times with the belly of the finger. After that, one end of the tape was momentarily pulled apart while keeping one end of the tape at right angles to the conductive film, and the number of base meshes remaining without being completely peeled was examined. It is most preferable that the number of base meshes remaining without being completely peeled is 100, that is, those having not peeled off at all.

The following were used for each component in Table 2.
Copper powder: Cu-HWQ (shape: spherical, average particle size: 3.0 μm, manufactured by Fukuda Metal Foil Powder Industry)

・ Silver salt of 2-methylpropanoate:
50 g of silver oxide (manufactured by Toyo Kagaku Kogyo Co., Ltd.), 38 g of 2-methylpropanoic acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of methyl ethyl ketone (MEK) were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver 2-methylpropanoate.

・ 2-ethylbutyric acid silver salt:
50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 50.13 g of 2-ethylbutyric acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver 2-ethylbutyrate.

・ Neodecanoic acid silver salt:
50 g of silver oxide (manufactured by Toyo Kagaku Kogyo Co., Ltd.), 74.3 g of neodecanoic acid (manufactured by Toyo Gosei Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Next, MEK was removed by suction filtration, and the obtained powder was dried to prepare a silver neodecanoate.

・ 2-ethylhexanoic acid silver salt:
50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 49.27 g of 2-ethylhexanoic acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver 2-ethylhexanoate.

-Silver stearate:
50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 123 g of stearic acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare a silver stearate salt.

・ 1,2,3,4-Butanetetracarboxylic acid silver salt:
First, 50 g of silver oxide (manufactured by Toyo Kagaku Kogyo Co., Ltd.), 25.29 g of 1,2,3,4-butanetetracarboxylic acid (manufactured by Shin Nippon Chemical Co., Ltd.) and 300 g of MEK are put into a ball mill and stirred at room temperature for 24 hours. Was reacted.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare 1,2,3,4-butanetetracarboxylic acid silver salt.

・ Glutaric acid silver salt:
50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 28.5 g of glutaric acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver glutarate.

N-butyric acid silver salt:
50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 38.01 g of n-butyric acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Next, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver n-butyrate.

Silver laurate salt 40 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 68 g of lauric acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver laurate.

・ 4-cyclohexene-1,2-dicarboxylic acid silver salt:
50 g of silver oxide (manufactured by Toyo Kagaku Kogyo Co., Ltd.), 36.67 g of 4-cyclohexene-1,2-dicarboxylic acid (manufactured by Shin Nippon Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours. .
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver 4-cyclohexene-1,2-dicarboxylate.

・ Azelaic acid silver salt:
50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 40.60 g of azelaic acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were put into a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare azelaic acid silver salt.

2,2-bis (hydroxymethyl) -n-butyric acid silver salt:
50 g of silver oxide (manufactured by Toyo Kagaku Kogyo Co., Ltd.), 64 g of 2,2-bis (hydroxymethyl) -n-butyric acid (manufactured by Tokyo Chemical Industry Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours. .
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare 2,2-bis (hydroxymethyl) -n-butyric acid silver salt.

・ 2-hydroxyisobutyric acid silver salt:
50 g of silver oxide (manufactured by Toyo Kagaku Kogyo Co., Ltd.), 45 g of 2-hydroxyisobutyric acid (manufactured by Tokyo Chemical Industry Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver 2-hydroxyisobutyrate.

・ Silver glycolate:
50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 16.40 g of glycolic acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Next, MEK was removed by suction filtration, and the resulting powder was dried to prepare silver glycolate.

・ Hydroxypivalic acid silver salt:
50 g of silver oxide (manufactured by Toyo Chemical Co., Ltd.), 25.48 g of hydroxypivalic acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of MEK were placed in a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the resulting powder was dried to prepare a hydroxypivalic acid silver salt.

Malonic acid silver salt:
50 g of silver oxide (manufactured by Toyo Kagaku Kogyo Co., Ltd.), 11 g of malonic acid and 300 g of MEK were put into a ball mill and reacted by stirring at room temperature for 24 hours.
Subsequently, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver malonate.

Thermosetting resin: bisphenol A type epoxy resin (EP-4100E, manufactured by ADEKA)
Thermosetting resin: bisphenol F type epoxy resin (EP-4901E, manufactured by ADEKA)
-Thermosetting resin: Urethane-modified epoxy resin (EPU-1395, manufactured by ADEKA)
・ Curing agent: Boron trifluoride ethylamine (manufactured by Stella Chemifa)
・ Solvent: Terpinel

From the results shown in Table 2, the conductive compositions of Comparative Examples 1 to 6 prepared using a fatty acid silver salt having a difference between the thermal decomposition peak temperature and the thermal decomposition starting temperature of less than 40 ° C. It was found that the volume resistivity was increased by two orders of magnitude.
Moreover, it turned out that the electroconductive composition of the comparative example 2 with much content of fatty acid silver salt is also inferior in adhesiveness.
On the other hand, the conductive composition prepared using a fatty acid silver salt having a difference between the thermal decomposition peak temperature and the thermal decomposition starting temperature of 40 ° C. or higher has a low volume resistivity after the wet heat resistance test, It was also found that the adhesiveness was excellent (Examples 1 to 17).
In particular, the comparison between Examples 1 to 13 reveals that the volume resistivity after the wet heat resistance test can be further reduced when the difference between the thermal decomposition peak temperature and the thermal decomposition start temperature is 100 ° C. or more.
Further, from the comparison with Examples 8, 14 and 15, when the content of the thermosetting resin (C) is 1.0 to 50 parts by mass with respect to 100 parts by mass of the copper powder (A), the formed electrode It has been found that the volume resistivity of etc. becomes lower.

DESCRIPTION OF SYMBOLS 1,100 Solar cell 2 N layer 3 Anti-reflective film 4 Front surface electrode 5 P layer 6 Back surface electrode 7 Silicon substrate 11 N-type single

crystal silicon substrate

12a, 12b i-type amorphous silicon layer 13a p-type amorphous silicon layer 13b n-type amorphous Silicon layer 14a, 14b Transparent conductive layer 15a, 15b Current collecting electrode

Claims

A conductive composition comprising copper powder (A), a fatty acid silver salt (B), and a thermosetting resin (C),
The difference between the thermal decomposition peak temperature of the fatty acid silver salt (B) and the thermal decomposition start temperature is 40 ° C. or higher,
The content of the fatty acid silver salt (B) is 20 to 100 parts by mass with respect to 100 parts by mass of the copper powder (A) in terms of the amount of silver produced from the fatty acid silver salt (B). Conductive composition.
The conductive composition according to claim 1, wherein the content of the thermosetting resin (C) is 1 to 50 parts by mass with respect to 100 parts by mass of the copper powder (A).
A solar cell using the conductive composition according to claim 1 or 2 as a collecting electrode.
The solar cell according to claim 3, further comprising a transparent conductive layer as a base layer of the current collecting electrode.
A solar battery module using the solar battery cell according to claim 3 or 4.