KR20160021178A - Electrically conductive composition and solar cell - Google Patents

Abstract

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 cell using the same as a current collector electrode. The conductive composition of the present invention is a conductive composition having a copper component (A), a fatty acid silver salt (B) and a thermosetting resin (C), wherein the difference between the thermal decomposition peak temperature of the fatty acid silver salt (B) ° C and the content of the fatty acid silver salt (B) is 20 to 100 parts by mass relative to 100 parts by mass of the copper (A) in terms of the amount of silver produced from the fatty acid silver salt (B).

Description

ELECTRICALLY CONDUCTIVE COMPOSITION AND SOLAR CELL [0002]

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

BACKGROUND ART Conventionally, conductive particles such as silver particles are coated with a binder containing a thermoplastic resin (e.g., acrylic resin, vinyl acetate resin or the like), a thermosetting resin (such as epoxy resin or unsaturated polyester resin) A conductive paste (conductive composition) obtained by adding a conductive paste, a curing agent, a catalyst and the like to a predetermined pattern on a substrate (for example, a silicon substrate or an epoxy resin substrate) Thereby forming a solar cell or a printed wiring board.

For example, Patent Document 1 discloses a method in which a film formed by applying the ink paste to a glass substrate surface-treated with an epoxy silane in a fine metal particle ink paste containing metal fine particles and a dispersion medium, and then baking at 180 캜 for 10 minutes A metal fine particle ink paste having a thickness of 10 탆 and an electric conductivity of 10 ⁴ S / cm or more is disclosed (claim 1), and a "fatty acid silver salt" is contained as an organometallic compound (claim 2) (Claim 8)), and "silver and / or copper fine particles" as the metal fine particles (claim 11).

The applicant of the present invention has proposed in Patent Document 2 that a conductive composition containing a silver salt (A), a fatty acid silver salt (B), a resin (C) and a solvent (D), wherein the fatty acid silver salt (B) A conductive composition having one base (-COOAg) and further having one or two hydroxyl groups (-OH), wherein the content of silver oxide is 10 parts by mass or less based on 100 parts by mass of the solvent (D). " ([Claim 1]).

Japanese Patent Application Laid-Open No. 2008-198595 Japanese Patent Application Laid-Open No. 2002-023095

However, when 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 component of the conductive composition described in Patent Document 2 is changed to copper, at least a part of the surface of the copper particles It has been found that the volume resistivity of the electrode or wiring (hereinafter also referred to as " electrode or the like ") formed depending on the use environment may be increased due to oxidation.

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

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies to solve the above problems and found that a conductive composition containing copper powder, a fatty acid silver salt and a thermosetting resin is characterized in that the difference between the thermal decomposition peak temperature and the thermal decomposition initiation temperature is 40 DEG C or higher By using a specific amount of fatty acid silver salt to be formed, the inventors have accomplished the present invention by finding that the volume resistivity of an electrode or the like to be formed is lowered.

That is, the inventors of the present invention have found out that the above problems can be solved by the following constitution.

 (1) A conductive composition having copper (A), a fatty acid silver salt (B) and a thermosetting resin (C)

Wherein the difference between the thermal decomposition peak temperature of the fatty acid silver salt (B) and the thermal decomposition starting temperature is 40 占 폚 or higher,

Wherein the content of the fatty acid silver salt (B) is 20 to 100 parts by mass relative to 100 parts by mass of the copper component (A) in terms of the amount of silver produced from the fatty acid silver salt (B).

(2) The conductive composition according to item (1), wherein the content of the thermosetting resin (C) is 1 to 50 parts by mass relative to 100 parts by mass of the copper component (A).

(3) A solar cell using the conductive composition according to the above (1) or (2) as a current collector electrode.

(4) The solar cell as described in (3) above, wherein a transparent conductive layer is provided as a ground layer (underlying layer) of the current collector.

(5) A solar cell module using the solar cell as described in (3) or (4) above.

As described 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 cell using the same as a current collector electrode.

In addition, by using the conductive composition of the present invention, it is possible to form an electrode having a low volume resistivity even if it is fired at a low temperature to a middle temperature (less than 450 DEG C), particularly at a low temperature (about 150 to 350 DEG C) (In particular, the second-favorable sun, which will be described later) can be alleviated.

Further, by using the conductive composition of the present invention, it is possible to easily make circuits such as electronic circuits and antennas on a material having low heat resistance such as a PET film as well as a material having high heat resistance such as indium tin oxide (ITO) It is also very useful because it can be produced in a short time.

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

[Conductive composition]

The conductive composition of the present invention is a conductive composition having a copper component (A), a fatty acid silver salt (B) and a thermosetting resin (C).

When the epoxy resin is used as the thermosetting resin (C), the conductive composition of the present invention may contain a curing agent (D).

In addition, the conductive composition of the present invention may contain a solvent (E), if necessary, from the viewpoint of printability and the like as described later.

In the present invention, by using a specific amount of the fatty acid silver salt (B) in which the difference between the thermal decomposition peak temperature and the thermal decomposition starting temperature is 40 占 폚 or higher, a conductive composition capable of forming an electrode or the like having a low volume resistivity can be obtained.

This is not clear in detail, but is estimated to be approximately 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 initiation temperature of not lower than 40 DEG C, silver is generated from the fatty acid silver salt in a wide temperature range and the silver is efficiently coated on the surface of the copper particle It is considered that the oxidation of the surface of the copper particles could be suppressed.

On the other hand, when a fatty acid silver salt having a difference between the thermal decomposition peak temperature and the thermal decomposition initiation temperature is less than 40 ° C is used, silver is generated instantaneously, so that the surface of the copper particle can not be covered locally, It is considered to be insufficient. This is also presumed from the results shown in Comparative Examples to be described later.

The curing agent (D) and the solvent (E), which may contain the copper component (A), the fatty acid silver salt (B) and the thermosetting resin (C), and if desired, will be described in detail below.

<Copper powder (A)>

The copper component (A) used in the conductive composition of the present invention is not particularly limited, and those conventionally known conductive pastes may be used.

The copper particles (A) preferably have an average particle size of 1.0 to 20 탆, more preferably 2.0 to 10 탆, for the reason that the printing property becomes good and an electrode or the like having a smaller volume resistivity can be formed .

Here, the average particle diameter refers to an average value of the particle diameters, and refers to a 50% volume cumulative diameter (D50) calculated by using a laser diffraction / scattering type particle size distribution measuring apparatus and calculating the number of particle diameter references. The average particle diameter of the copper powder is an average value obtained by dividing the total value of the major and minor diameters by 2 when the cross section of the copper powder is elliptical. .

In the present invention, a commercial product can be used as such a copper powder (A), and specific examples thereof include Cu-HWQ (average particle size: 3.0 m, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) , FCC-TBX (average particle diameter: 5.05 m, Fukuda Kinko Co., Ltd.), and the like.

&Lt; Fatty silver salt (B) &gt;

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 starting temperature is 40 DEG C or higher.

Here, the thermal decomposition peak temperature refers to the DTA curve when measured in a temperature range from room temperature to 300 ° C at a heating rate of 5 ° C / min in air using a simultaneous differential thermal and thermogravimeter (TG-DTA) It refers to the exothermic peak temperature that appears.

The thermal decomposition initiation temperature was measured in a temperature range from room temperature to 300 deg. C at a temperature raising rate of 5 deg. C / min in air using a simultaneous differential thermal & simultaneous thermogravimeter (TG-DTA) Is the temperature at which it was made.

By using such a fatty acid silver salt (B), the generation of silver derived from the reduction of the fatty acid silver salt (B) takes place in a wide temperature range as described above, and the surface of the copper component (A) .

It is preferable that the difference between the thermal decomposition peak temperature and the thermal decomposition starting temperature is 100 ° C or higher, and more preferably 100-130 ° C because the fatty acid silver salt (B) can form an electrode or the like having a low volume resistivity after the anti- Lt; 0 &gt; C. This is considered to be because the surface of the copper powder (A) can be coated more efficiently by the 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 initiation temperature in the silver salt of the organic carboxylic acid is not lower than 40 ° C, and for example, in Japanese Unexamined Patent Application Publication No. 2008-198595 The fatty acid metal salts (particularly tertiary fatty acid silver salts) described in the paragraphs [0063] to [0068] and the fatty acids described in the paragraph [0030] of Japanese Patent Publication No. 4482930 can be obtained by the method described in Japanese Patent Application Laid- And secondary fatty acid silver salts described in the paragraphs [0056] to [0056].

Specific examples of the fatty acid silver salt (B) include stearic acid silver salt, n-butyric acid silver salt, 2-ethylhexanoic acid silver salt, 2-methylpropanoic acid silver salt (aka: isobutyrate 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-1,2-dicarboxylic acid silver salt, .

Incidentally, the thermal decomposition starting temperature and the 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 parts by mass with respect to 100 parts by mass of the copper component (A) in terms of the amount of silver produced from the fatty acid silver salt (B) More preferably 40 to 100 parts by mass.

&Lt; Thermosetting resin (C) &gt;

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, and a urethane resin. Even if one of them is used alone Two or more kinds may be used in combination.

Of these, an epoxy resin is preferable because of its strong adhesion to the silicon substrate and high heat and humidity resistance.

(Epoxy resin)

The epoxy resin as a representative example of the thermosetting resin (C) is not particularly limited as long as it is a resin comprising a compound having two or more oxirane rings (epoxy groups) in a molecule, and generally has an epoxy equivalent of 90 to 2000.

As such an epoxy resin, conventionally known epoxy resins can be used.

Specifically, for example, an epoxy compound having a bisphenyl group such as a bisphenol A type, a bisphenol F type, a brominated bisphenol A type, a hydrogenated bisphenol A type, a bisphenol S type, a bisphenol AF type, , Bifunctional glycidyl ether type epoxy resins such as polyalkylene glycol type, alkylene glycol type epoxy compounds, epoxy compounds having a naphthalene ring, and epoxy compounds having a fluorene group;

Polyhydric glycidyl ether type epoxy resins such as phenol novolac type, orthocresol novolak type, tris hydroxyphenyl methane type and tetraphenylol ethane type;

Glycidyl ester-based epoxy resins of synthetic fatty acids such as dimer acid;

N, N, N ', N'-tetraglycidyldiaminodiphenylmethane (TGDDM), tetraglycidyldiaminodiphenylsulfone (TGDDS), tetraglycidyl- Aminophenol, N, N-diglycidyl aniline, tetraglycidyl-1,3-bisaminomethylcyclohexane (TG1, 3-BAC), triglycidyl Glycidylamine-based epoxy resins such as sidyl isocyanurate (TGIC);

An epoxy compound having a tricyclo [5,2,1,0 ^2,6 ] decane ring, specifically, for example, a cresol or a phenol such as dicyclopentadiene and metacresol is polymerized and epichlorohydrin An epoxy compound obtained by a known production method of reacting a dodecylamine with a dodecylamine;

Alicyclic epoxy resins; An epoxy resin having a sulfur atom in an epoxy resin main chain (main chain) typified by Flop 10 made by Toray Thiokol Co., Ltd; A urethane-modified epoxy resin having a urethane bond; Rubber-modified epoxy resins containing polybutadiene, liquid polyacrylonitrile-butadiene rubber or acrylonitrile butadiene rubber (NBR), and the like.

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 preferably 1.0 to 50 parts by mass with respect to 100 parts by mass of the copper component (A) because the volume resistivity of the electrode or the like to be formed becomes lower. More preferably 2 to 25 parts by mass.

&Lt; Curing agent (D) &gt;

When an epoxy resin is used as the thermosetting resin (C), the conductive composition of the present invention preferably contains a curing agent (D) comprising a complex of boron trifluoride and an amine compound.

Examples of complexes between boron trifluoride and an amine compound include complexes of boron trifluoride with aliphatic amines (aliphatic primary amines, aliphatic secondary amines, aliphatic tertiary amines), complexes of boron trifluoride with alicyclic amines , Complexes of boron trifluoride with aromatic amines, complexes of boron trifluoride with heterocyclic amines, 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).

Specific examples of the aliphatic primary amine include methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, n-hexylamine, 2-ethylhexylamine, laurylamine, and the like. Specific examples of the aliphatic secondary amine include dimethylamine, diethylamine, methylethylamine, methylpropylamine, di-isopropylamine, di-n-propylamine, ethylpropylamine, di- butylamine, diisopropylamine, diisobutylamine, dipropylamine, 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 and the like. Examples of the aromatic amine include benzylamine and the like. Specific examples of the alicyclic heterocyclic amine include pyrrolidine, piperidine, pipecoline, 3-piperolin, 4-piperolin, lupetidine ), 2,6-lutetidine, 3,5-lupetidine, piperazine, homopiperazine, N-methylpiperazine, N-ethylpiperazine, N-propylpiperazine, N- Aminopropylpiperazine, N-aminopropylpiperazine, N-aminopropylpiperazine, morpholine, N-acetylpiperazine, N-acetylpiperazine, N- aminopropyl-2-piperolin, N-aminopropyl-4-piperolin, 1,4-bis (aminopropyl) piperazine, N-aminopropylmorpholine, N- Triethylenediamine, 2-methyltriethylenediamine, and the like. Specific examples of the aromatic heterocyclic amine include pyridine, pyrrole, imidazole, pyridazine, pyrimidine, quinoline, triazine, tetrazine, tetrazine, isoquinoline, quinazoline, naphthyridine, pteridine, acridine, phenazine, and the like.

The curing agent (D) is preferably a complex selected from the group consisting of boron trifluoride piperidine, boron trifluoride ethylamine and boron trifluoride triethanol amine for the reason that the volume resistivity of the electrode or the like to be formed becomes lower .

The content of the curing agent (D) is preferably from 1 to 15 parts by mass, more preferably from 1 to 10 parts by mass, based on 100 parts by mass of the epoxy resin, because the volume resistivity of the electrode or the like to be formed becomes lower .

&Lt; Solvent (E) &gt;

The conductive composition of the present invention preferably contains the solvent (E) from the viewpoint of workability such as printability.

The solvent (E) is not particularly limited as long as it can coat the conductive composition of the present invention on a substrate. Specific examples thereof include butyl carbitol, methyl ethyl ketone, isophorone, These may be used singly or in combination of two or more.

<Additives>

The conductive composition of the present invention may contain an additive such as a reducing agent if necessary.

Specific examples of the reducing agent include ethylene glycol and the like.

<Method for producing conductive composition>

The method for producing the conductive composition of the present invention is not particularly limited and the method for producing the conductive composition of the present invention is not particularly limited and the curing agent (D), the curing agent (B) and the thermosetting resin (C) A method in which the solvent (E) and additives are mixed by a roll, a kneader, an extruder, a universal stirrer, or the like.

[Solar cell]

The solar cell of the present invention is a solar cell using the above-described conductive composition of the present invention as a current collector electrode.

&Lt; First Preferred Embodiment of Solar Cell &gt;

As a first preferred embodiment of the solar cell of the present invention, there is provided a surface electrode on the light-receiving surface side, a semiconductor substrate and a back electrode, wherein the surface electrode and / or the back electrode are formed by using the conductive composition of the present invention And the like.

Hereinafter, a first preferred embodiment of the solar cell of the present invention will be described with reference to Fig.

1, the solar cell 1 includes a surface electrode 4 on the light-receiving surface side, a pn junction silicon substrate 7 formed by bonding the p-layer 5 and the n-layer 2, And a back electrode (6).

1, the photovoltaic cell 1 is provided with an antireflection film 3, for example, by etching the surface of the wafer to form a pyramid-shaped texture in order to reduce the reflectance. .

Hereinafter, the above-mentioned surface electrode, back electrode, silicon substrate and the above-mentioned antireflection film provided in the first embodiment of the solar cell of the present invention and the antireflection film provided therewith will be described in detail.

(Surface electrode / back electrode)

The arrangement (pitch), shape, height, width and the like of the electrodes are not particularly limited as long as either one of the surface electrode and the back electrode is formed using the conductive composition of the present invention. Incidentally, although the height of the electrode is usually designed to be several to several tens of micrometers, the ratio (height / width) of the height and width of the cross section of the electrode formed using the conductive composition of the present invention (hereinafter referred to as "aspect ratio" ) Can be largely adjusted (for example, about 0.4 or more).

As shown in Fig. 1, a plurality of surface electrodes and back electrodes are usually provided. For example, only a part of a plurality of surface electrodes may be formed of the conductive composition of the present invention. And a part of the plurality of backside 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 mu m) formed on a portion where the surface electrode of the light-receiving surface is not formed. For example, a silicon oxide film, a silicon nitride film, a titanium oxide film, .

Further, the silicon substrate has a pn junction, which means that the light-receiving surface impurity diffusion region of the second conductivity type is formed on the surface side of the semiconductor substrate of the first conductivity type. Incidentally, when the first conductivity type is n-type, the second conductivity type is p-type, and when the first conductivity type is p-type, the second conductivity type is n-type.

Examples of impurities imparting p-type conductivity include boron and aluminum, and examples of impurities imparting n-type conductivity include phosphorus and arsenic.

(Silicon substrate)

The silicon substrate is not particularly limited, and a well-known silicon substrate (plate thickness: about 80 to 450 mu m) for forming a solar cell can be used, and any silicon substrate of single crystal or polycrystalline may be used.

In the first aspect of the solar cell of the present invention, since the surface electrode and / or the back electrode are formed using the conductive composition of the present invention, the aspect ratio of the electrode can be easily increased , The electromotive force generated by light reception can be efficiently extracted as a current.

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

&Lt; Manufacturing method of solar cell (No. 1 solar cell) &gt;

The method for manufacturing the solar cell (the first embodiment) is not particularly limited. However, it is also possible to form a wiring by forming the wiring by forming the wiring by applying the conductive composition of the present invention onto the silicon substrate, Electrode and / or back electrode) on the surface of the substrate.

Incidentally, when the solar battery cell is provided with the antireflection layer, the antireflection film can be formed by a known method such as the plasma CVD method.

Hereinafter, the wiring forming step and the heat treatment step will be described in detail.

(Wiring forming step)

The wiring forming step is a step of forming a wiring by applying the conductive composition of the present invention onto a silicon substrate.

Specific examples of the application method include inkjet, screen printing, gravure printing, offset printing, and engraving printing.

(Heat treatment process)

The heat treatment step is a step of forming a conductive wiring (electrode) by heat-treating a coating film formed in the wiring formation step.

By conducting the heat treatment of the wiring, the electrode is formed by connecting the surface of the copper foil A while covering the silver dissolving from the fatty acid silver salt (B).

The heat treatment is not particularly limited, but is preferably a treatment for heating (firing) at a relatively low temperature of 150 to 350 占 폚 for several seconds to several tens minutes. When the temperature and the time are within this range, the electrode can be easily formed even when the antireflection film is formed on the silicon substrate.

Further, in the first embodiment of the solar cell of the present invention, since the conductive composition of the present invention is used, good heat treatment (firing) can be performed even at a relatively low temperature of 150 to 350 캜.

In the present invention, since the wiring formed in the wiring formation step can form an electrode even when irradiated with ultraviolet rays or infrared rays, the heat treatment step may be performed by irradiation with ultraviolet rays or infrared rays.

&Lt; Second Preferred Embodiment of Solar Cell &gt;

As a second preferred embodiment of the solar cell of the present invention, an amorphous silicon layer and a transparent conductive layer (for example, TCO) are provided on and under the n-type single crystal silicon substrate as a center, , A solar cell (for example, a hetero junction solar cell) in which a collector electrode is formed on the transparent conductive layer using the conductive composition of the present invention as described above. The solar cell (the second solar cell) is a solar cell in which single crystal silicon and amorphous silicon are hybridized, and exhibits high conversion efficiency.

A second preferred embodiment of the solar cell of the present invention will now be described with reference to Fig.

2, the solar cell 100 includes i-type amorphous silicon layers 12a and 12b, and a p-type amorphous silicon layer (not shown) on the upper and lower sides of the n-type single crystal silicon substrate 11, 13a and an n-type amorphous silicon layer 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 impurity imparting n-type conductivity. The impurities imparting n-type are as described above.

The i-type amorphous silicon layer is an amorphous silicon layer which is not doped.

The p-type amorphous silicon is an amorphous silicon layer doped with an impurity imparting p-type conductivity. The impurity imparting p-type is as described above.

The n-type amorphous silicon is an amorphous silicon layer doped with an impurity imparting n-type conductivity. The impurities imparting n-type are as described above.

The current-collecting electrode is a current-collecting electrode formed using the above-described conductive composition of the present invention. The specific embodiment of the current collecting electrode is the same as the above-described surface electrode or back electrode.

(Transparent conductive layer)

Specific examples of the material of the transparent conductive layer include a single metal oxide such as zinc oxide, tin oxide, indium oxide and titanium oxide, a metal oxide such as indium tin oxide (ITO), zinc oxide indium oxide, cadmium tin oxide, , Doped 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.

&Lt; Manufacturing method of solar cell (second solar cell) &gt;

The manufacturing method of the solar cell (second embodiment) is not particularly limited, but can be manufactured by the method described in Japanese Patent Application Laid-Open No. 2010-34162, for example.

Specifically, the i-type amorphous silicon layer 12a is formed on the main surface of one side of the n-type single crystal silicon substrate 11 by plasma enhanced chemical vapor deposition (PECVD) 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 principal 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 a sputtering method or the like.

Next, current collecting electrodes 15a and 15b are formed by applying the conductive composition of the present invention on the formed transparent conductive layers 14a and 14b to form wiring, and further heat-treating the formed wiring.

The method of forming the wiring is the same as the method described in the wiring forming step of the solar cell (the first preferred embodiment) described above.

The method of heat-treating the wiring is the same as that described in the heat treatment step of the solar cell (the first preferred embodiment) described above, but the heat treatment temperature (baking temperature) is preferably 150 to 200 ° C.

Example

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

(Examples 1 to 17 and Comparative Examples 1 to 6)

And the copper powders and the like shown in Table 2 below were mixed so as to have the composition ratios (parts by mass) shown in the following Table 2, and these were mixed to prepare a conductive composition.

&Lt; Volume resistivity (resistivity) &gt;

Each of the conductive compositions thus prepared was applied by screen printing on an ITO-deposited glass substrate as a TCO to form a 25 mm x 25 mm tightly painted test pattern. And dried in an oven at 200 DEG C for 30 minutes to prepare a conductive film.

The volume resistivity of each of the conductive films thus produced was measured immediately after the preparation (initial) and after 85 hours at 85 ° C and at a humidity of 500 hours (after the resistance to moisture-humidity heat) by using a resistivity meter (Loresta GP, Mitsubishi Kagaku Co., (Manufactured by Mitsubishi Chemical Co., Ltd.). The results are shown in Table 2 below.

&Lt; Adhesion &gt;

The adhesion of each formed conductive film to the substrate was evaluated by a checkerboard peeling test. The results are shown in Table 2 below.

Specifically, 100 pieces (10 x 10) of 1 mm checkerboard eyes were made on the substrate provided with each conductive film thus obtained, the cellophane adhesive tape was completely adhered on the checkerboard eye, and after 10 times of bending the inside of the finger, Was held momentarily at a right angle to the electroconductive film, and the number of the remaining checkerboards without peeling completely was examined. It is most preferable that the number of checkered eyes remaining without being completely peeled off is 100, that is, not peeled off at all.

The following components were used for each component in Table 2.

Copper powder: Cu-HWQ (shape: spherical, average particle diameter: 3.0 탆, Fukuda Kinkozu Hakuhun Kogyo Co., Ltd.)

· 2-methylpropanoic acid silver salt:

38 g of 2-methylpropanoic acid (manufactured by Kanto Chemical Co., Ltd.) and 300 g of methyl ethyl ketone (MEK) were put into a ball mill, and the mixture was stirred at room temperature At room temperature for 24 hours.

Then, MEK was removed by suction filtration, and the obtained powder was dried to prepare 2-methylpropanoic acid silver salt.

· 2-ethylbutyric acid silver salt:

50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 50.13 g of 2-ethylbutyric acid (Kanto Kagaku Co.) and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Thereafter, MEK was removed by suction filtration, and the obtained powder was dried to prepare 2-ethylbutyric acid silver salt.

· Neodecanoic acid silver salt:

50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 74.3 g of neodecanoic acid (manufactured by Toyo Gosei Co., Ltd.) and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Thereafter, MEK was removed by suction filtration, and the obtained powder was dried to prepare neodecanoic acid silver salt.

· 2-ethylhexanoic acid silver salt:

50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 49.27 g of 2-ethylhexanoic acid (Kanto Chemical), and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Thereafter, MEK was removed by suction filtration, and the obtained powder was dried to prepare 2-ethylhexanoic acid silver salt.

· Silver stearate:

, 50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 123 g of stearic acid (Kanto Kagaku), and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Thereafter, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver stearate.

1,2,3,4-butanetetracarboxylic acid silver salt:

First, 50 g of silver oxide (Toyokakakuko Chemical Co., Ltd.), 25.29 g of 1,2,3,4-butanetetracarboxylic acid (manufactured by Shin-Nippon Rika Co., Ltd.) and 300 g of MEK were put into a ball mill, Followed by stirring for 24 hours.

Then, 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 (Toyokagakuko Chemical Co., Ltd.), 28.5 g of glutaric acid (Kanto Kagaku Co.), and 300 g of MEK were put into a ball mill and reacted by stirring at room temperature for 24 hours.

Then, MEK was removed by suction filtration, and the obtained powder was dried to prepare glutaric acid silver salt.

N-naphthoic acid silver salt:

50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 38.01 g of n-butyric acid (Kanto Kagaku Co.) and 300 g of MEK were put into a ball mill and reacted at room temperature for 24 hours with stirring.

Then, MEK was removed by suction filtration, and the obtained powder was dried to prepare n-butyric acid silver salt.

· Silver salt laurate:

40 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 68 g of lauric acid (Kanto Kagaku Co.) and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Then, MEK was removed by suction filtration, and the obtained powder was dried to prepare lauric acid silver salt.

4-Cyclohexene-1,2-dicarboxylic acid silver salt:

Cyclohexene-1,2-dicarboxylic acid (Shin-Nippon Rika Chemical Co., Ltd.) and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Thereafter, MEK was removed by suction filtration, and the obtained powder was dried to prepare 4-cyclohexene-1,2-dicarboxylic acid silver salt.

Azelaic silver salt:

50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 40.60 g of Azela (Kanto Kagaku), and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Then, 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:

64 g of 2,2-bis (hydroxymethyl) -n-butyric acid (manufactured by TOKYO KASEI CHEMICAL CO., LTD.) And 300 g of MEK were put into a ball mill, and stirred at room temperature for 24 hours Lt; / RTI &gt;

Then, MEK was removed by suction filtration, and the obtained powder was dried to prepare 2,2-bis (hydroxymethyl) -n-naphtaline silver salt.

· 2-hydroxyisobutylic acid silver salt:

50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 45 g of 2-hydroxyisobutyric acid (manufactured by Tokyo Kasei Co., Ltd.) and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Then, MEK was removed by suction filtration, and the obtained powder was dried to prepare 2-hydroxyisobutylic acid silver salt.

· Glycolic acid silver salt:

, 50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 16.40 g of glycolic acid (Kanto Kagaku Co.) and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Thereafter, MEK was removed by suction filtration, and the obtained powder was dried to prepare glycolic acid silver salt.

· Hydroxy diacid silver salt:

, 50 g of silver oxide (Toyokagakuko Chemical Co., Ltd.), 25.48 g of hydroxypivalic acid (Kanto Chemical), and 300 g of MEK were put into a ball mill and stirred at room temperature for 24 hours.

Then, MEK was removed by suction filtration, and the obtained powder was dried to prepare hydroxyvalerate silver halide.

· Malonic acid silver salt:

50 g of silver oxide (Toyokakakuko Chemical 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.

Thereafter, MEK was removed by suction filtration, and the obtained powder was dried to prepare silver malonic acid silver salt.

Thermosetting resin: bisphenol A type epoxy resin (EP-4100E, manufactured by ADEKA)

Thermosetting resin: Bisphenol F type epoxy resin (EP-4901E, manufactured by ADPCASHA)

Thermosetting resin: urethane-modified epoxy resin (EPU-1395, manufactured by Adeka)

Curing agent: boron trifluoride ethylamine (manufactured by STELLACHEMIFA CORPORATION)

Solvent: terpineol

From the results shown in Table 2, the conductive compositions of Comparative Examples 1 to 6 prepared using the fatty acid silver salt having a difference between the thermal decomposition peak temperature and the thermal decomposition initiation temperature of less than 40 占 폚 had a volume resistivity after two- .

Further, it was found that the conductive composition of Comparative Example 2, in which the content of the fatty acid silver salt was large, also had poor adhesiveness.

On the contrary, it was found that the conductive composition prepared by using the fatty acid silver salt having a difference between the thermal decomposition peak temperature and the thermal decomposition initiation temperature of 40 占 폚 or higher had a low volume resistivity after the heat and moisture resistance test and was also excellent in adhesion with the substrate Examples 1 to 17).

In particular, from the comparison of Examples 1 to 13, it was found that the volume resistivity after the resistance to moisture heat test can be lowered when the difference between the thermal decomposition peak temperature and the thermal decomposition starting temperature is 100 ° C or more.

From the comparison of Examples 8, 14 and 15, it is understood that when the content of the thermosetting resin (C) is 1.0 to 50 parts by mass relative to 100 parts by mass of the copper component (A), the volume resistivity .

1, 100: solar cell
2: n layer
3: antireflection film
4: surface electrode
5: p layer
6: back electrode
7: silicon substrate
11: n-type single crystal silicon substrate
12a and 12b: an i-type amorphous silicon layer
13a: a p-type amorphous silicon layer
13b: an n-type amorphous silicon layer
14a and 14b: a transparent conductive layer
15a and 15b: current collecting electrodes

Claims (5)

A conductive composition having a copper component (A), a fatty acid silver salt (B) and a thermosetting resin (C)
Wherein the difference between the thermal decomposition peak temperature of the fatty acid silver salt (B) and the thermal decomposition starting temperature is 40 占 폚 or higher,
Wherein the content of the fatty acid silver salt (B) is 20 to 100 parts by mass relative to 100 parts by mass of the copper component (A) in terms of the amount of silver produced from the fatty acid silver salt (B). The method according to claim 1,
Wherein the content of the thermosetting resin (C) is 1 to 50 parts by mass relative to 100 parts by mass of the copper component (A). A solar cell using the conductive composition according to claim 1 or 2 as a current collector electrode. The method of claim 3,
And a transparent conductive layer as a base layer (underlying layer) of the current collector electrode. A solar cell module using the solar cell according to claim 3 or 4.

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