WO2011090211A1 - Paste composition for electrode, and solar cell - Google Patents

Abstract

Disclosed are: a paste composition for an electrode, which rarely undergoes the oxidation of copper contained therein during burning and enables the production of an electrode having low resistivity; and a solar cell equipped with an electrode produced using the paste composition. Specifically disclosed are: a paste composition for an electrode, which comprises metal particles mainly composed of copper, a phosphorus-containing compound, glass particles, a solvent and a resin; and a solar cell equipped with an electrode produced by burning the paste composition.

Description

Electrode paste composition and solar cell

The present invention relates to an electrode paste composition and a solar cell.

Generally, a solar cell is provided with a surface electrode, and the wiring resistance and contact resistance of this surface electrode are related to voltage loss related to conversion efficiency, and the wiring width and shape affect the amount of incident sunlight ( (See, for example, Yasuhiro Sasakawa, “Solar Power Generation: Latest Technologies and Systems”, CMC Publishing Company, 2001, p. 26-27).

The surface electrode of a solar cell is usually formed as follows. That is, a conductive composition is applied by screen printing or the like on an n-type semiconductor layer formed by thermally diffusing phosphorus or the like at a high temperature on the light-receiving surface side of a p-type silicon substrate, and this is applied to 800 to 900 A surface electrode is formed by baking at ° C. The conductive composition forming the surface electrode includes conductive metal powder, glass particles, various additives, and the like.

As the conductive metal powder, silver powder is generally used. However, use of metal powders other than silver powder has been studied for various reasons. For example, a conductive composition capable of forming a solar cell electrode containing silver and aluminum is disclosed (see, for example, JP-A-2006-313744). Also disclosed is an electrode-forming composition containing metal nanoparticles containing silver and metal particles other than silver (see, for example, JP-A-2008-226816).

In general, silver used for electrode formation is a noble metal, and due to the problem of resources, and the metal itself is expensive, a proposal of a paste material to replace the silver-containing conductive composition (silver-containing paste) is desired. . A promising material that can replace silver is copper that is applied to semiconductor wiring materials. Copper is abundant in terms of resources, and the cost of bullion is as low as about 1/100 of silver. However, copper is a material that is easily oxidized at a high temperature of 200 ° C. or higher. For example, in the electrode forming composition described in Japanese Patent Application Laid-Open No. 2008-226816, when copper is contained as a conductive metal, this is fired. In order to form an electrode, a special process of firing in an atmosphere of nitrogen or the like was necessary.

The present invention provides a paste composition for an electrode capable of forming an electrode having low resistivity with suppressed oxidation of copper during firing, and a solar cell having an electrode formed using the paste composition for electrode. The task is to do.

1st aspect of this invention is the paste composition for electrodes containing the metal particle | grains which have copper as a main component, a phosphorus containing compound, a glass particle, a solvent, and resin. The phosphorus-containing compound is preferably at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene.
Moreover, it is preferable that the paste composition for electrodes further contains silver particles.

A second aspect of the present invention is a solar cell having an electrode formed by firing the paste composition for an electrode applied on a silicon substrate.

ADVANTAGE OF THE INVENTION According to this invention, the oxidation of copper at the time of baking is suppressed, the paste composition for electrodes which can form an electrode with low resistivity, and the solar cell which has an electrode formed using this paste composition for electrodes Can be provided.

It is sectional drawing of the solar cell concerning this invention. It is a top view which shows the light-receiving surface side of the solar cell concerning this invention. It is a top view which shows the back surface side of the solar cell concerning this invention. (A) It is a perspective view which shows the AA cross-section structure of the cell back contact type solar cell concerning this invention. (B) It is a top view which shows the back surface side electrode structure of the cell back contact type solar cell concerning this invention.

In this specification, “to” indicates a range including the numerical values described before and after the minimum and maximum values, respectively.

<Paste composition for electrodes>
The electrode paste composition of the present invention comprises at least one metal particle mainly composed of copper, at least one phosphorus-containing compound, at least one glass particle, at least one solvent, and a resin. And at least one kind.
With such a configuration, oxidation of copper during firing is suppressed, and an electrode with low resistivity can be formed.

(Metal particles)
The metal particles containing copper as a main component in the present invention (hereinafter sometimes referred to as “copper-containing particles”) mean metal particles in which the content of the copper component in one metal particle is 50% by mass or more.
The metal particles containing copper as a main component impart oxidation resistance to copper and copper even when the metal particles are substantially made of copper and may contain other atoms within a range not impairing the effects of the present invention. The metal particle containing a component may be sufficient.

Examples of other atoms in the metal particles substantially composed of copper include, for example, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Mo, Ti, Co, Ni, Au, etc. can be mentioned. Among these, Al is preferably contained from the viewpoint of adjusting characteristics such as oxidation resistance and melting point.
Moreover, the content rate of the other atom contained in the said copper containing particle | grain can be 3 mass% or less in the said copper containing particle | grain, for example, and it is 1 mass% or less from a viewpoint of oxidation resistance and a low resistivity. Preferably there is.

The metal particles containing copper and a component that imparts oxidation resistance to copper preferably have a peak temperature of an exothermic peak exhibiting a maximum area in differential thermal-thermogravimetric simultaneous measurement (TG-DTA) of 280 ° C. or higher. The temperature is preferably 280 to 800 ° C, more preferably 350 to 750 ° C.
By using metal particles mainly composed of copper to which such oxidation resistance is imparted, oxidation of metallic copper during firing is suppressed and a low resistivity electrode can be formed. The differential heat-thermogravimetric simultaneous measurement is performed in a normal atmosphere using a differential heat-thermogravimetric analyzer (TG / DTA-6200, manufactured by SII Nano Technology, Inc.), for example, measurement temperature range: room temperature Up to 1000 ° C., heating rate: 40 ° C./min, air flow rate: 200 ml / min.

Specific examples of metal particles mainly composed of copper having a peak temperature of an exothermic peak showing a maximum area in the differential thermal-thermogravimetric simultaneous measurement (TG-DTA) of 280 ° C. or more include, for example, phosphorus-containing copper alloy particles , Silver-coated copper particles, and surface treatment with at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. Copper particles can be mentioned, and at least one selected from these is preferably used. The copper-containing particles may be used alone or in combination of two or more.

The particle diameter of the copper-containing particles is not particularly limited, but the particle diameter when the accumulated weight is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.4 μm to 10 μm. Is preferably 1 μm to 7 μm. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the copper containing particles in an electrode becomes large because it is 10 micrometers or less, and a resistivity falls more effectively. The particle size of the copper-containing particles is measured with a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
Further, the shape of the copper-containing particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity, It is preferably substantially spherical, flat, or plate-shaped.

The content of the copper-containing particles contained in the electrode paste composition of the present invention, and the total content of the copper-containing particles and the silver particles in the case of containing silver particles described later are, for example, 70 to 94% by mass. In view of oxidation resistance and low resistivity, it is preferably 72 to 90% by mass, more preferably 74 to 88% by mass.
In the present invention, conductive particles other than the copper-containing particles may be used in combination.

-Phosphorus-containing copper alloy particles-
As a phosphorus-containing copper alloy, a brazing material called phosphorus copper brazing (phosphorus concentration: about 7% by mass or less) is known. Phosphorus copper brazing is also used as a bonding agent between copper and copper, but by using phosphorous-containing copper alloy particles as copper-containing particles contained in the electrode paste composition of the present invention, oxidation resistance is improved. An electrode having excellent and low resistivity can be formed. Further, the electrode can be fired at a low temperature, and the effect that the process cost can be reduced can be obtained.

The phosphorus content contained in the phosphorus-containing copper alloy in the present invention is preferably such that the peak temperature of the exothermic peak showing the maximum area in the differential thermal-thermogravimetric simultaneous measurement is 280 ° C. or higher. Specifically, it can be 0.01% by mass or more in the total mass of the phosphorus-containing copper alloy particles. In the present invention, from the viewpoint of oxidation resistance and low resistivity, the phosphorus content is preferably 0.01 to 8% by mass, more preferably 0.5 to 7.8% by mass. More preferably, it is 7.5% by mass.
When the phosphorus content contained in the phosphorus-containing copper alloy is 8% by mass or less, a lower resistivity can be achieved, and the productivity of the phosphorus-containing copper alloy is excellent. Moreover, the more outstanding oxidation resistance can be achieved because it is 0.01 mass% or more.

The phosphorus-containing copper alloy particles are an alloy containing copper and phosphorus, but may further contain other atoms. Examples of other atoms include Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Mo, Ti, Co, Ni, Au, etc. can be mentioned. Among these, Al is preferably contained from the viewpoint of adjusting characteristics such as oxidation resistance and melting point.
Moreover, the content rate of the other atom contained in the said phosphorus containing copper alloy particle can be 2 mass% or less in the said phosphorus containing copper alloy particle, for example, from a viewpoint of oxidation resistance and a low resistivity, it is 1 It is preferable that it is below mass%.

The particle diameter of the phosphorus-containing copper alloy particles is not particularly limited, but the particle diameter when the accumulated weight is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.4 μm to 10 μm. It is preferably 1 μm to 7 μm. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the phosphorus containing copper alloy particles in an electrode becomes large because it is 10 micrometers or less, and a resistivity falls more effectively.
The shape of the phosphorus-containing copper alloy particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, but from the viewpoint of oxidation resistance and low resistivity. Therefore, it is preferably substantially spherical, flat, or plate-shaped.

The phosphorus-containing copper alloy can be produced by a commonly used method. Also, the phosphorus-containing copper alloy particles can be prepared using a normal method of preparing metal powder using a phosphorus-containing copper alloy prepared so as to have a desired phosphorus content, for example, a water atomization method Can be produced by a conventional method. The water atomization method is described in Metal Handbook (Maruzen Publishing Division).
Specifically, for example, after phosphorus-containing copper alloy is dissolved and powdered by nozzle spray, the obtained powder is dried and classified, whereby desired phosphorus-containing copper alloy particles can be produced. Moreover, the phosphorus containing copper alloy particle | grains which have a desired particle diameter can be manufactured by selecting classification conditions suitably.

The content of the phosphorus-containing copper alloy particles contained in the electrode paste composition of the present invention can be, for example, 70 to 94% by mass, and from the viewpoint of oxidation resistance and low resistivity, 72 to 90%. The content is preferably mass%, more preferably 74 to 88 mass%.
In the present invention, the phosphorus-containing copper alloy particles may be used singly or in combination of two or more. Furthermore, it may be used in combination with copper-containing particles other than phosphor copper alloy particles, the peak temperature of the exothermic peak showing the maximum area being 280 ° C. or higher.

Furthermore, in the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, phosphorus-containing copper alloy particles having a phosphorus content of 0.01 to 8% by mass are contained in the electrode paste composition in an amount of 70 to 94% by mass. The phosphorus-containing copper alloy particles having a phosphorus content of 1 to 7.5% by mass are preferably included in the electrode paste composition in an amount of 74 to 88% by mass.
In the present invention, conductive particles other than the phosphorus-containing copper alloy particles may be used in combination.

-Silver-coated copper particles-
As the silver-coated copper particles in the present invention, it is sufficient that at least a part of the surface of the copper particles is coated with silver. By using silver-coated copper particles as the copper-containing particles contained in the electrode paste composition of the present invention, an electrode having excellent oxidation resistance and low resistivity can be formed. Furthermore, since the copper particles are coated with silver, the interface resistance between the silver-coated copper particles and the silver particles is reduced, and an electrode with a lower resistivity can be formed. Furthermore, when water is mixed in the electrode paste composition, the use of silver-coated copper particles can suppress the oxidation of copper at room temperature and can improve the pot life.

As the silver coating amount (silver content) in the silver-coated copper particles, the coating amount (silver content) such that the peak temperature of the exothermic peak showing the maximum area in the differential thermal-thermogravimetric simultaneous measurement is 280 ° C. or more. It is preferable that Specifically, it can be 1% by mass or more based on the total mass of the silver-coated copper particles, and 1 to 88% by mass based on the total mass of the silver-coated copper particles from the viewpoint of oxidation resistance and low resistivity of the electrode. Preferably, it is 3 to 80% by mass, more preferably 5 to 75% by mass.

The particle diameter of the silver-coated copper particles is not particularly limited, but the particle diameter when the accumulated weight is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.4 μm to 10 μm. It is preferably 1 μm to 7 μm. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the silver covering copper particle in an electrode becomes large because it is 10 micrometers or less, and a resistivity falls more effectively.
Further, the shape of the silver-coated copper particles is not particularly limited and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity. It is preferably substantially spherical, flat or plate-like.

The copper constituting the silver-coated copper particles may contain other atoms as long as the effects of the present invention are not impaired. Examples of other atoms include Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Mo, Ti, Co, Ni, Au, etc. can be mentioned. Among these, Al is preferably contained from the viewpoint of adjusting characteristics such as oxidation resistance and melting point.
Moreover, the content rate of the other atom contained in the said silver covering copper particle can be 3 mass% or less in the said silver covering copper particle, for example, and 1 mass% from a viewpoint of oxidation resistance and a low resistivity. The following is preferable.

Moreover, it is also preferable that the silver-coated copper particles are those in which the above-described phosphorus-containing copper alloy is silver-coated. As a result, the oxidation resistance is further improved, and the resistivity of the formed electrode is further reduced.
About the detail of the phosphorus containing copper alloy in a silver covering copper particle, it is synonymous with the above-mentioned phosphorus containing copper alloy, and its preferable aspect is also the same.

The method for preparing the silver-coated copper particles is not particularly limited as long as at least a part of the surface of the copper particles (preferably phosphorus-containing copper alloy particles) can be coated with silver. For example, it can be prepared as follows. That is, copper powder (or phosphorus-containing copper alloy powder) is dispersed in an acidic solution such as sulfuric acid, hydrochloric acid, and phosphoric acid, and a chelating agent is added to the copper powder dispersion to prepare a copper powder slurry. By adding a silver ion solution to the obtained copper powder slurry, a silver layer can be formed on the surface of the copper powder by a substitution reaction to prepare silver-coated copper particles.
Although there is no restriction | limiting in particular as said chelating agent, For example, ethylenediaminetetraacetic acid salt, triethylenediamine, diethylenetriaminepentaacetic acid, iminodiacetic acid, etc. can be used. Moreover, as a silver ion solution, a silver nitrate solution etc. can be used, for example.

The content of the silver-coated copper particles contained in the paste composition for an electrode of the present invention, and the total content of silver-coated copper particles and silver particles in the case of containing silver particles described later are, for example, 70 to 94% by mass. In view of oxidation resistance and low resistivity, it is preferably 72 to 90% by mass, more preferably 74 to 88% by mass.
In the present invention, the silver-coated copper particles may be used singly or in combination of two or more. Moreover, you may use in combination with the copper containing particle | grains whose peak temperature in the exothermic peak which shows the largest areas other than silver covering copper particle is 280 degreeC or more.

In the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, the silver-coated copper particles having a silver content of 1 to 88% by mass in the total mass of the silver-coated copper particles are contained in the electrode paste composition. 70 to 94% by mass (the total content of silver-coated copper particles and silver particles in the case of containing silver particles described later) is preferably included, and the silver-coated copper particles having a silver content of 5 to 75% by mass, More preferably, the electrode paste composition contains 74 to 88 mass% (the total content of silver-coated copper particles and silver particles when silver particles described later are included).
Furthermore, 70 to 94% by mass of silver-coated phosphorus-containing copper alloy particles having a silver content of 1 to 88% by mass and a phosphorus content of 0.01 to 8% by mass in the electrode paste composition (described later). In the case where the silver particles to be included are included, it is preferable to include silver-coated phosphorus-containing copper alloy particles and silver particles), the silver content is 5 to 75% by mass, and the phosphorus content is 1 to 7.5. 74 to 88% by mass (total content of silver-coated phosphorus-containing copper alloy particles and silver particles in the case of containing silver particles described later) in the electrode paste composition is silver-coated phosphorus-containing copper alloy particles of mass% It is more preferable.
In the present invention, conductive particles other than the silver-coated copper particles may be used in combination.

-Surface treated copper particles-
The copper-containing particles in the present invention are a group consisting of a triazole compound, a saturated fatty acid, an unsaturated fatty acid, an inorganic metal compound salt, an organic metal compound salt, a polyaniline resin, and a metal alkoxide (hereinafter sometimes referred to as “surface treatment agent”). It is also preferable that the copper particles are surface-treated with at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, and inorganic metal compound salts. More preferably, it is a copper particle.
Forming an electrode with excellent oxidation resistance and low resistivity by using copper particles surface-treated with at least one surface treatment agent as the copper-containing particles contained in the electrode paste composition of the present invention Can do. Further, when moisture is mixed in the electrode paste composition, the use of the surface-treated copper particles can suppress the oxidation of copper at room temperature and can improve the pot life.
In the present invention, the surface treatment agents may be used singly or in combination of two or more.

In the present invention, the surface-treated copper particles are at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. Although it has been treated, other surface treatment agents may be used in combination as required.

Examples of the triazole compound in the surface treatment agent include benzotriazole and triazole. Examples of the saturated fatty acid in the surface treatment agent include enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, stearic acid, nonadecanoic acid, arachic acid, Examples include behenic acid. Examples of the unsaturated fatty acid in the surface treatment agent include acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, elaidic acid, cetreic acid, brassic acid, erucic acid, sorbic acid, and linoleic acid. Linolenic acid, arachidonic acid and the like.
Examples of the inorganic metal compound salt in the surface treatment agent include sodium silicate, sodium stannate, tin sulfate, zinc sulfate, sodium zincate, zirconium nitrate, sodium zirconate, zirconium chloride, titanium sulfate, and titanium chloride. And potassium oxalate titanate. Examples of the organometallic compound salt in the surface treatment agent include lead stearate, lead acetate, p-cumylphenyl derivative of tetraalkoxyzirconium, and p-cumylphenyl derivative of tetraalkoxytitanium. Examples of the metal alkoxide in the surface treatment agent include titanium alkoxide, zirconium alkoxide, lead alkoxide, silicon alkoxide, tin alkoxide, and indium alkoxide.

Examples of other surface treatment agents include dodecylbenzene sulfonic acid.
When stearic acid or lead stearate is used as the surface treatment agent, the oxidation resistance is further improved and the resistivity is improved by using at least one of stearic acid and lead stearate and lead acetate as the surface treatment agent. Lower electrodes can be formed.

In the surface-treated copper particles in the present invention, it is sufficient that at least a part of the surface of the copper particles is coated with at least one of the surface treatment agents. The content of the surface treating agent contained in the surface-treated copper particles is preferably such that the peak temperature of the exothermic peak showing the maximum area in the differential thermal-thermogravimetric simultaneous measurement is 280 ° C. or higher. . Specifically, it can be 0.01% by mass or more in the total mass of the surface-treated copper particles, and from the viewpoint of oxidation resistance and low resistivity of the electrode, in the total mass of the surface-treated copper particles The amount is preferably 0.01 to 10% by mass, and more preferably 0.05 to 8% by mass in the total mass of the surface-treated copper particles.

The copper constituting the surface-treated copper particles may contain other atoms as long as the effects of the present invention are not impaired. Examples of other atoms include Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Mo, Ti, Co, Ni, Au, etc. can be mentioned. Among these, Al is preferably contained from the viewpoint of adjusting characteristics such as oxidation resistance and melting point.
Moreover, the content rate of the other atom contained in the said surface-treated copper particle can be 3 mass% or less in the said surface-treated copper particle, for example from a viewpoint of oxidation resistance and a low resistivity. It is preferable that it is 1 mass% or less.

The surface-treated copper particles are also preferably those obtained by surface-treating the above-described phosphorus-containing copper alloy. As a result, the oxidation resistance is further improved, and the resistivity of the formed electrode is further reduced.
About the detail of the phosphorus containing alloy in the surface-treated copper particle, it is synonymous with the above-mentioned phosphorus containing alloy, and a preferable aspect is also the same.

The particle diameter of the surface-treated copper particles is not particularly limited, but the particle diameter when the accumulated weight is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.4 μm to The thickness is preferably 10 μm, more preferably 1 μm to 7 μm. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the said surface-treated copper particle in an electrode becomes large because it is 10 micrometers or less, and a resistivity falls more effectively.
Further, the shape of the surface-treated copper particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, etc., but from the viewpoint of oxidation resistance and low resistivity. Therefore, it is preferably substantially spherical, flat, or plate-shaped.

The surface treatment method for copper particles using a surface treatment agent can be appropriately selected according to the surface treatment agent to be used. For example, by preparing a surface treatment solution in which the surface treatment agent is dissolved in a solvent capable of dissolving the surface treatment agent, and immersing and drying the copper particles in this, at least a part of the surface of the copper particles is coated with the surface treatment agent. Can be coated.

The solvent capable of dissolving the surface treatment agent can be appropriately selected according to the surface treatment agent. For example, water, alcohol solvents such as methanol, ethanol, isopropanol, glycol solvents such as ethylene glycol monoethyl ether, carbitol solvents such as diethylene glycol monobutyl ether, carbitol acetate solvents such as diethylene glycol monoethyl ether acetate, etc. Can be mentioned.
Specifically, for example, when benzotriazole, triazole, or dodecylbenzene sulfonic acid is used as the surface treatment agent, a surface treatment solution can be prepared using an alcohol solvent to treat the copper particles.
When stearic acid or lead stearate is used as the surface treatment agent, a surface treatment solution can be prepared using an alcohol solvent.

The concentration of the surface treatment agent in the surface treatment solution can be appropriately selected according to the type of surface treatment agent to be used and the desired surface treatment amount. For example, it can be 1 to 90% by mass, and preferably 2 to 85% by mass.

The content of the surface-treated copper particles contained in the electrode paste composition of the present invention, and the total content of the surface-treated copper particles and silver particles in the case of containing silver particles described later are, for example, 70 From the viewpoint of oxidation resistance and low resistivity, it is preferably 72 to 90% by mass, and more preferably 74 to 88% by mass.
In the present invention, the surface-treated copper particles may be used singly or in combination of two or more. Moreover, you may use in combination with the copper containing particle | grains whose peak temperature in the exothermic peak which shows the largest areas other than the surface-treated copper particle is 280 degreeC or more.

In the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, it is selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. The copper particles surface-treated so that at least one kind contained in an amount of 0.01 to 10% by mass was contained in the electrode paste composition in an amount of 70 to 94% by mass (in the case where silver particles described later were included, the surface treatment was performed). (Total content of copper particles and silver particles) is preferably included so that at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, and inorganic metal compound salts is contained in an amount of 0.1 to 8% by mass. 4 to 88% by mass of the surface-treated copper particles in the electrode paste composition (in the case of containing silver particles described later, the total content of the surface-treated copper particles and silver particles) ) It is more preferable to include.
Further, the surface contains 0.01 to 10% by mass of at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. The surface-treated phosphorus-containing copper alloy particles having a phosphorus content of 8% by mass or less were treated with 70 to 94% by mass (surface-treated phosphorus in the case of containing silver particles described later) in the electrode paste composition. The total content of the copper alloy particles and silver particles contained) is preferably 0.1 to 8% by mass of at least one selected from the group consisting of triazole compounds, saturated fatty acids, unsaturated fatty acids, and inorganic metal compound salts. Surface-treated phosphorus-containing copper alloy particles having a phosphorus content of 1 to 7.5% by mass in the paste composition for an electrode. To 88% by weight (total content of the surface-treated phosphorous-containing copper alloy particles and the silver particles may include silver particles to be described later) more preferably contains.
In the present invention, conductive particles other than the surface-treated copper particles may be used in combination.

(Phosphorus-containing compound)
The electrode paste composition of the present invention contains at least one phosphorus-containing compound. Thereby, the oxidation resistance is effectively improved and the resistivity of the formed electrode is lowered. Furthermore, in the case of a crystalline silicon solar cell, it is possible to dope P into the Si under the electrode by diffusion at the time of sintering the electrode, and the effect that the characteristics of the n-type layer of Si can be maintained.
The phosphorus-containing compound is a compound having a large phosphorus atom content in the molecule from the viewpoint of oxidation resistance and low resistivity of the electrode, and does not cause evaporation or decomposition under a temperature condition of about 200 ° C. Preferably there is.

Specific examples of the phosphorus-containing compound include phosphorous inorganic acids such as phosphoric acid, phosphates such as ammonium phosphate, phosphoric acid esters such as alkyl phosphates and aryl aryl esters, and cyclic phosphazenes such as hexaphenoxyphosphazene. As well as their derivatives.
The phosphorus-containing compound in the present invention is preferably at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene, from the viewpoint of oxidation resistance and low electrode resistivity. More preferably, it is at least one selected from the group consisting of ammonium phosphate, phosphate ester, and cyclic phosphazene.

The content of the phosphorus-containing compound in the present invention is preferably 0.5 to 10% by mass in the total mass of the electrode paste composition from the viewpoints of oxidation resistance and low electrode resistivity. More preferably, it is ˜7% by mass.
Furthermore, in the present invention, at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene is used as the phosphorus-containing compound in an amount of 0.5 to 10 in the total mass of the electrode paste composition. It is preferable to contain at least 1 mass%, and more preferably at least one selected from the group consisting of ammonium phosphate, phosphate ester and cyclic phosphazene is contained in the total mass of the electrode paste composition.

(Glass particles)
The electrode paste composition of the present invention contains at least one kind of glass particles. When the electrode paste composition contains glass particles, the silicon nitride film as the antireflection film is removed by so-called fire-through at the electrode formation temperature, and an ohmic contact between the electrode and the silicon substrate is formed.

The glass particles are usually used in the technical field as long as they can soften and melt at the electrode formation temperature, oxidize the contacted silicon nitride film, and take the oxidized silicon dioxide to remove the antireflection film. The glass particles used can be used without particular limitation.
In the present invention, glass particles containing glass having a glass softening point of 600 ° C. or lower and a crystallization start temperature exceeding 600 ° C. are preferable from the viewpoint of oxidation resistance and low resistivity of the electrode. The glass softening point is measured by a usual method using a thermomechanical analyzer (TMA), and the crystallization start temperature is measured using a differential heat-thermogravimetric analyzer (TG-DTA). Measured by method.

Generally, the glass particles contained in the electrode paste composition are composed of glass containing lead because silicon dioxide can be taken up efficiently. Examples of such lead-containing glass include those described in Japanese Patent No. 03050064, and these can also be suitably used in the present invention.
In the present invention, it is preferable to use lead-free glass that does not substantially contain lead in consideration of the influence on the environment. Examples of the lead-free glass include lead-free glass described in paragraphs 0024 to 0025 of JP-A-2006-313744 and lead-free glass described in JP-A-2009-188281. It is also preferable that the lead-free glass is appropriately selected and applied to the present invention.

The content of the glass particles is preferably 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, based on the total mass of the electrode paste composition, and 1 to 7% by mass. % Is more preferable. By including glass particles with a content in such a range, oxidation resistance, low resistivity of the electrode, and low contact resistance can be achieved more effectively.

In the present invention, the glass particles preferably include 0.1 to 10% by weight of glass particles made of lead-free glass, and are made of lead-free glass having a V ₂ O ₅ content of 1% by weight or more. More preferably, it contains 0.5 to 8% by mass of glass particles, and more preferably 1 to 7% by mass of glass particles made of lead-free glass having a V ₂ O ₅ content of 1% by mass or more.

(Solvent and resin)
The electrode paste composition of the present invention contains at least one solvent and at least one resin. Thereby, the liquid physical property (for example, a viscosity, surface tension, etc.) of the paste composition for electrodes of this invention can be adjusted to the required liquid physical property according to the provision method at the time of providing to a silicon substrate.

The solvent is not particularly limited. For example, hydrocarbon solvents such as hexane, cyclohexane and toluene; chlorinated hydrocarbon solvents such as dichloroethylene, dichloroethane and dichlorobenzene; cyclics such as tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, 1,3-dioxolane and trioxane Ether solvents; amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide; sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone and cyclohexanone; ethanol; Alcohol compounds such as 2-propanol, 1-butanol and diacetone alcohol; 2,2,4-trimethyl-1,3-pentanediol monoacetate, 2,2,4- Limethyl-1,3-pentanediol monopropiolate, 2,2,4-trimethyl-1,3-pentanediol monobutyrate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, Ester solvents of polyhydric alcohols such as 2,2,4-triethyl-1,3-pentanediol monoacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate; ethers of polyhydric alcohols such as butyl cellosolve and diethylene glycol diethyl ether Terpene solvents such as α-terpinene, α-terpineol, myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, oximene, ferrandrene, and the like A mixture is mentioned.

As the solvent in the present invention, from the viewpoints of coatability and printability when the electrode paste composition is formed on a silicon substrate, a polyhydric alcohol ester solvent, a terpene solvent, a polyhydric alcohol ether solvent. It is preferably at least one selected, and more preferably at least one selected from an ester solvent of a polyhydric alcohol and a terpene solvent.
In this invention, the said solvent may be used individually by 1 type or in combination of 2 or more types.

In addition, as the resin, any resin that is usually used in the technical field can be used as long as it can be thermally decomposed by firing. Specifically, for example, cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and nitrocellulose; polyvinyl alcohols; polyvinyl pyrrolidones; acrylic resins; vinyl acetate-acrylic acid ester copolymers; butyral resins such as polyvinyl butyral; phenol Examples thereof include alkyd resins such as modified alkyd resins and castor oil fatty acid modified alkyd resins; epoxy resins; phenol resins; rosin ester resins.

The resin in the present invention is preferably at least one selected from a cellulose resin and an acrylic resin, and more preferably at least one selected from a cellulose resin, from the viewpoint of disappearance during firing. .
In this invention, the said resin may be used individually by 1 type or in combination of 2 or more types.

In the electrode paste composition of the present invention, the content of the solvent and the resin can be appropriately selected according to the desired liquid properties and the type of solvent and resin used. For example, the total content of the solvent and the resin is preferably 5% by mass or more and 28% by mass or less, more preferably 5% by mass or more and 25% by mass or less, based on the total mass of the electrode paste composition. More preferably, it is 7 mass% or more and 20 mass% or less.
When the total content of the solvent and the resin is within the above range, the application suitability when applying the electrode paste composition to the silicon substrate is improved, and an electrode having a desired width and height is more easily formed. can do.

(Silver particles)
The electrode paste composition of the present invention preferably further contains at least one silver particle. By containing silver particles, the oxidation resistance is further improved, and the resistivity as an electrode is further reduced. Furthermore, the effect that the solder connection property at the time of setting it as a solar cell module improves is also acquired. This can be considered as follows, for example.

In general, in a temperature range of 600 ° C. to 900 ° C., which is an electrode formation temperature range, a small amount of silver is dissolved in copper and a small amount of copper is dissolved in silver, and copper is formed at the interface between copper and silver. -A silver solid solution layer (solid solution region) is formed. When a mixture of copper-containing particles and silver particles is heated to a high temperature and then slowly cooled to room temperature, it is considered that a solid solution region does not occur, but at the time of electrode formation, it is cooled from the high temperature region to room temperature in a few seconds. It is thought that the solid solution layer in FIG. 4 covers the surface of the silver particles and the copper-containing particles as a non-equilibrium solid solution phase or a eutectic structure of copper and silver. Such a copper-silver solid solution layer can be considered to contribute to the oxidation resistance of the copper-containing particles at the electrode formation temperature.

Also, the copper-silver solid solution layer starts to be formed at a temperature of 300 ° C. to 500 ° C. or higher. Therefore, by using silver particles together with copper-containing particles having a peak temperature of an exothermic peak showing a maximum area in simultaneous differential heat-thermogravimetric measurement of 280 ° C. or more, the oxidation resistance of the copper-containing particles can be more effectively improved. It can be considered that the resistivity of the formed electrode is further reduced.

The silver constituting the silver particles may contain other atoms inevitably mixed. As other atoms inevitably mixed, for example, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W , Mo, Ti, Co, Ni, Au, and the like.

The particle diameter of the silver particles in the present invention is not particularly limited, but the particle diameter (D50%) when the accumulated weight is 50% is preferably 0.4 μm or more and 10 μm or less, and 1 μm or more and 7 μm or less. It is more preferable that When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of metal particles, such as a silver particle and copper containing particle | grains in an electrode, becomes large because it is 10 micrometers or less, and resistivity falls more effectively.

In the electrode paste composition of the present invention, the relationship between the particle diameter of the copper-containing particles (D50%) and the particle diameter of the silver particles (D50%) is not particularly limited, but either one of the particle diameters (D50 %) Is smaller than the other particle size (D50%), and the ratio of the other particle size to any one particle size is more preferably 1 to 10. Thereby, the resistivity of an electrode falls more effectively. This can be attributed to, for example, an increase in contact area between metal particles such as copper-containing particles and silver particles in the electrode.

The silver particle content in the electrode paste composition of the present invention is 8.4 to 85.5% by mass in the electrode paste composition from the viewpoint of oxidation resistance and low electrode resistivity. It is preferably 8.9 to 80.1% by mass.
Furthermore, in the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, the content of the copper-containing particles is 9 to 88% by mass when the total amount of the copper-containing particles and the silver particles is 100% by mass. Preferably, it is 17 to 77% by mass. When the content of the copper-containing particles is 9% by mass or more, for example, when the glass particles contain divanadium pentoxide, the reaction between silver and vanadium is suppressed, and the volume resistance of the electrode is further reduced. Moreover, it is suppressed that the content rate of a front copper containing particle | grain is 88 mass% or less, and the copper contained in a copper containing particle | grain contacts a silicon substrate, and the contact resistance of an electrode falls more.

Moreover, in the electrode paste composition of the present invention, the total content of the copper-containing particles and the silver particles is 70% by mass or more and 94 from the viewpoint of oxidation resistance, low resistivity of the electrode, and applicability to a silicon substrate. It is preferably no greater than mass%, and more preferably no less than 74 mass% and no greater than 88 mass%. When the total content of the copper-containing particles and the silver particles is 70% by mass or more, a suitable viscosity can be easily achieved when the electrode paste composition is applied. Moreover, generation | occurrence | production of the blurring at the time of providing the paste composition for electrodes can be suppressed more effectively because the total content of the said copper containing particle | grains and the said silver particle is 94 mass% or less.

Further, in the electrode paste composition of the present invention, from the viewpoint of oxidation resistance and low resistivity of the electrode, the total content of the copper-containing particles and the silver particles is 70% by mass or more and 94% by mass or less, The glass particle content is 0.1% by mass or more and 10% by mass or less, and the total content of the solvent, the resin, and the phosphorus-containing compound is 3% by mass or more and 29.9% by mass or less. Preferably, the total content of the copper-containing particles and the silver particles is 72% by mass or more and 90% by mass or less, and the content of the glass particles is 0.5% by mass or more and 8% by mass or less, and the solvent More preferably, the total content of the resin and the phosphorus-containing compound is 5% by mass or more and 25% by mass or less, and the total content of the copper-containing particles and the silver particles is 74% by mass or more and 88% by mass or less. And said Content of lath grains is not more than 7 mass% to 1 mass%, the solvent, it is more preferable that the total content of the resin and the phosphorus-containing compound is not more than 20 wt% 7 wt% or more.

(flux)
The electrode paste composition may further include at least one flux. By containing the flux, the oxidation resistance is further improved, and the resistivity of the formed electrode is further reduced. Furthermore, the effect that the diffusion of copper to the silicon substrate can be suppressed is also obtained.

The flux in the present invention is not particularly limited as long as the oxide film formed on the surface of the copper-containing particles can be removed. Specifically, for example, fatty acids, boric acid compounds, fluorinated compounds, borofluorinated compounds and the like can be mentioned as preferred fluxes.

More specifically, lauric acid, myristic acid, palmitic acid, stearic acid, sorbic acid, stearic acid, boron oxide, potassium borate, sodium borate, lithium borate, potassium borofluoride, sodium borofluoride, borofluoride Examples include lithium, acidic potassium fluoride, acidic sodium fluoride, acidic lithium fluoride, potassium fluoride, sodium fluoride, and lithium fluoride.
Among these, potassium borate and potassium borofluoride are particularly preferable fluxes from the viewpoints of heat resistance at the time of firing the electrode material (characteristic that the flux does not volatilize at a low temperature during firing) and supplementing the oxidation resistance of the copper-containing particles.
In the present invention, each of these fluxes may be used alone or in combination of two or more.

Moreover, as content of the flux in the paste composition for electrodes of the present invention, the viewpoint of effectively expressing the oxidation resistance of the copper-containing particles and the viewpoint of reducing the porosity of the part where the flux is removed when the electrode material is completely fired. Therefore, the total amount of the electrode paste composition is preferably 0.1 to 5% by mass, more preferably 0.3 to 4% by mass, and 0.5 to 3.5% by mass. More preferably, it is 0.7 to 3% by mass, particularly preferably 1 to 2.5% by mass.

(Other ingredients)
Furthermore, the electrode paste composition of the present invention can further contain other components usually used in the technical field, if necessary, in addition to the components described above. Examples of other components include a plasticizer, a dispersant, a surfactant, an inorganic binder, a metal oxide, a ceramic, and an organometallic compound.

There is no particular limitation on the method for producing the electrode paste composition of the present invention. The copper-containing particles, glass particles, solvent, resin, and silver particles contained as necessary can be produced by dispersing and mixing them using a commonly used dispersion and mixing method.

<Method for Producing Electrode Using Electrode Paste Composition>
As a method for producing an electrode using the electrode paste composition of the present invention, the electrode paste composition is applied to a region where an electrode is to be formed, and after drying, the electrode is formed in a desired region by firing. be able to. By using the paste composition for an electrode, an electrode having a low resistivity can be formed even when a baking treatment is performed in the presence of oxygen (for example, in the air).
Specifically, for example, when a solar cell electrode is formed using the electrode paste composition, the electrode paste composition is applied on a silicon substrate so as to have a desired shape, and dried and fired. Thereby, a solar cell electrode with low resistivity can be formed in a desired shape. Further, by using the electrode paste composition, an electrode having a low resistivity can be formed even when a baking treatment is performed in the presence of oxygen (for example, in the air).
Examples of the method for applying the electrode paste composition onto the silicon substrate include screen printing, an inkjet method, a dispenser method, and the like. From the viewpoint of productivity, application by screen printing is preferable.

When the electrode paste composition of the present invention is applied by screen printing, it preferably has a viscosity in the range of 80 to 1000 Pa · s. The viscosity of the electrode paste composition is measured at 25 ° C. using a Brookfield HBT viscometer.

The application amount of the electrode paste composition can be appropriately selected according to the size of the electrode to be formed. For example, the applied amount of the electrode paste composition can be 2 to 10 g / m ^2, and preferably 4 to 8 g / m ² .

In addition, as heat treatment conditions (firing conditions) when forming an electrode using the electrode paste composition of the present invention, heat treatment conditions usually used in the technical field can be applied.
Generally, the heat treatment temperature (firing temperature) is 800 to 900 ° C. However, when the electrode paste composition of the present invention is used, heat treatment conditions at a lower temperature can be applied, for example, 600 to 850. An electrode having good characteristics can be formed at a heat treatment temperature of ° C.
The heat treatment time can be appropriately selected according to the heat treatment temperature and the like, and can be, for example, 1 second to 20 seconds.

<Solar cell>
The solar cell of this invention has the electrode formed by baking the said paste composition for electrodes provided on the silicon substrate. Thereby, the solar cell which has a favorable characteristic is obtained, and it is excellent in the productivity of this solar cell.

Hereinafter, although the specific example of the solar cell of this invention is demonstrated, referring drawings, this invention is not limited to this.
A sectional view showing an example of a typical solar cell element, and outlines of a light receiving surface and a back surface are shown in FIGS.
Usually, single crystal or polycrystalline Si is used for the semiconductor substrate 130 of the solar cell element. The semiconductor substrate 130 contains boron or the like and constitutes a p-type semiconductor. On the light receiving surface side, unevenness (texture, not shown) is formed by etching in order to suppress reflection of sunlight. The light receiving surface is doped with phosphorus or the like, an n-type semiconductor diffusion layer 131 is provided with a thickness of the order of submicrons, and a pn junction is formed at the boundary with the p-type bulk portion. Further, on the light receiving surface side, an antireflection layer 132 such as silicon nitride is provided on the diffusion layer 131 with a film thickness of about 100 nm by vapor deposition or the like.

Next, the light receiving surface electrode 133 provided on the light receiving surface side, and the current collecting electrode 134 and the output extraction electrode 135 formed on the back surface will be described. The light-receiving surface electrode 133 and the output extraction electrode 135 are formed from the electrode paste composition. The collecting electrode 134 is formed from an aluminum electrode paste composition containing glass powder. These electrodes are formed by applying the paste composition to a desired pattern by screen printing or the like, and then baking the paste composition at about 600 to 850 ° C. in the atmosphere.
In the present invention, by using the electrode paste composition, an electrode having excellent resistivity and contact resistivity can be formed even when fired at a relatively low temperature.

At that time, on the light receiving surface side, the glass particles contained in the electrode paste composition forming the light receiving surface electrode 133 react with the antireflection layer 132 (fire-through), and the light receiving surface electrode 133 and the diffusion layer are reacted. 131 is electrically connected (ohmic contact).
In the present invention, the light-receiving surface electrode 133 is formed using the electrode paste composition, so that copper is suppressed as a conductive metal, and the oxidation of copper is suppressed. , Formed with good productivity.

On the back surface side, aluminum in the aluminum electrode paste composition that forms the collecting electrode 134 during firing diffuses to the back surface of the semiconductor substrate 130 to form the electrode component diffusion layer 136, thereby forming the semiconductor substrate 130. Ohmic contact can be obtained between the current collector electrode 134 and the output extraction electrode 135.

FIG. 4 shows a perspective view (a) of a light receiving surface and an AA cross-sectional structure as an example of a solar cell element according to another aspect of the present invention, and a plan view (b) of a back surface side electrode structure.
As shown in the perspective view of FIG. 4A, the cell wafer 1 made of a p-type semiconductor silicon substrate is formed with through holes penetrating both the light receiving surface side and the back surface side by laser drilling or etching. . Further, a texture (not shown) for improving the light incident efficiency is formed on the light receiving surface side. Further, on the light receiving surface side, an n-type semiconductor layer 3 by n-type diffusion treatment and an antireflection film (not shown) are formed on the n-type semiconductor layer 3. These are manufactured by the same process as a conventional crystalline Si type solar battery cell.

Next, the electrode paste composition of the present invention is filled into the previously formed through-holes by a printing method or an ink jet method, and the electrode paste composition of the present invention is also formed in a grid on the light receiving surface side. The composition layer which is printed and forms the through-hole electrode 4 and the current collecting grid electrode 2 is formed.
Here, in the paste used for filling and printing, it is desirable to use a paste having an optimum composition for each process including viscosity, but filling and printing may be performed collectively with the paste having the same composition. .

On the other hand, a heavily doped layer 5 for preventing carrier recombination is formed on the opposite side (back side) of the light receiving surface. Here, boron (B) or aluminum (Al) is used as an impurity element for forming the high-concentration doped layer 5, and a p ⁺ layer is formed. The high-concentration doped layer 5 may be formed by performing a thermal diffusion process using, for example, B as a diffusion source in a cell manufacturing process before forming the antireflection film, or when using Al. May be formed by printing an Al paste on the opposite surface side in the printing step.

Thereafter, the electrode paste composition fired at 650 to 850 ° C., filled in and printed on the antireflection film formed in the through hole and on the light receiving surface side, has a lower n-type layer due to the fire through effect. Ohmic contact is achieved.

Also on the opposite surface side, as shown in the plan view of FIG. 4 (b), the electrode paste composition according to the present invention, respectively n-side printing in stripes on the p-side both by firing, back surface electrode 6, 7 is formed.

In the present invention, the through-hole electrode 4, the current collecting grid electrode 2, the back electrode 6 and the back electrode 7 are formed by using the electrode paste composition, so as to contain copper as a conductive metal, Copper oxidation is suppressed, and the low resistivity through-hole electrode 4, current collecting grid electrode 2, back electrode 6 and back electrode 7 are formed with excellent productivity.
The electrode paste composition of the present invention is not limited to the use of the solar cell electrode as described above. For example, electrode wiring and shield wiring of a plasma display, ceramic capacitor, antenna circuit, various sensor circuits, It can also be suitably used for applications such as heat dissipation materials for semiconductor devices.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

<Example 1>
(A) Preparation of electrode paste composition 32 parts of vanadium oxide (V ₂ O ₅ ), 26 parts of phosphorus oxide (P ₂ O ₅ ), 10 parts of barium oxide (BaO), 8 parts of manganese oxide (MnO ₂ ), oxidation Glass composed of 1 part of sodium (Na ₂ O), 3 parts of potassium oxide (K ₂ O), 10 parts of zinc oxide (ZnO) and 10 parts of tungsten oxide (WO ₃ ) (hereinafter abbreviated as “P19”). Prepared). The glass had a softening point of 447 ° C. and a crystallization temperature of over 600 ° C.
Glass particles having a particle diameter (D50%) of 1.7 μm were obtained using the obtained glass P19.

85.1 parts of copper particles (particle diameter (D50%) 1.5 μm, purity 99.9%, manufactured by Mitsui Mining & Smelting Co., Ltd.), 1.7 parts of glass particles (P19), 4% ethyl cellulose (EC) A butyl carbitol acetate (BCA) solution containing 13.2 parts and 3 parts of phosphoric acid (hereinafter sometimes abbreviated as “P1”) as a phosphorus-containing compound are mixed and mixed in an agate mortar for 20 minutes. The mixture was stirred to prepare electrode paste composition 1.

(B) Production of Solar Cell A p-type semiconductor substrate having a film thickness of 190 μm having an n-type semiconductor layer, a texture and an antireflection film (silicon nitride film) formed on the light receiving surface is prepared and cut into a size of 125 mm × 125 mm It was. Using the screen printing method on the light receiving surface, the electrode paste composition 1 obtained above was printed so as to have an electrode pattern as shown in FIG. The electrode pattern was composed of a finger line with a width of 150 μm and a bus bar with a width of 1.1 mm, and the printing conditions (screen plate mesh, printing speed, printing pressure) were appropriately adjusted so that the film thickness after firing was 20 μm. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.

Subsequently, an aluminum electrode paste was similarly printed on the back surface by screen printing. The printing conditions were appropriately adjusted so that the film thickness after firing was 40 μm. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.
Subsequently, heat treatment (baking) was performed at 850 ° C. for 2 seconds in an infrared rapid heating furnace in an air atmosphere to produce a solar battery cell 1 on which a desired electrode was formed.

<Example 2>
In Example 1, the solar cell 2 on which the desired electrode was formed was obtained in the same manner as in Example 1 except that the temperature of the heat treatment (firing) at the time of electrode formation was changed to 650 ° C. instead of 850 ° C. Produced.

<Examples 3 to 5>
In Example 2, instead of phosphoric acid (P1) as a phosphorus-containing compound, ammonium phosphate (hereinafter sometimes abbreviated as “P2”), triphenyl phosphate (hereinafter referred to as “P3”) as shown in Table 1 Electrode paste compositions 3 to 5 were prepared in the same manner as in Example 2 except that hexaphenoxyphosphazene (hereinafter sometimes abbreviated as “P4”) was used. .
Next, solar cells 3 to 5 on which desired electrodes were formed were produced in the same manner as in Example 2 except that the obtained electrode paste compositions 3 to 5 were used, respectively.

<Example 6>
Using the electrode paste composition 5 obtained above, a solar battery cell 6 having a structure as shown in FIG. 4 was produced. The heat treatment was performed at 650 ° C. for 10 seconds.

<Example 7>
As the electrode paste composition further containing silver particles, 42.9 parts of the 82.1 parts of the copper-containing particles in the electrode paste composition 5 used in Example 5 were replaced with silver particles. Product 7 was prepared.
Solar cell 7 was produced using electrode paste composition 7.

<Comparative Example 1>
The electrode paste composition of Example 1 was prepared in the same manner as in Example 1 except that each component was changed to the composition shown in Table 1 without using a phosphorus-containing compound. Composition C1 was prepared.
Using the electrode paste composition C1, a solar battery cell C1 was produced in the same manner as in Example 1.

<Comparative Example 2>
The electrode paste composition of Example 1 was prepared in the same manner as in Example 1 except that each component was changed to the composition shown in Table 1 without using a phosphorus-containing compound. Composition C2 was prepared.
A solar battery cell C2 was produced in the same manner as in Example 1 except that the electrode paste composition C2 was used and the heat treatment was performed at 650 ° C. for 10 seconds.

<Comparative Example 3>
The electrode paste composition of Example 1 was prepared in the same manner as in Example 1 except that each component was changed to the composition shown in Table 1 without using a phosphorus-containing compound. Composition C1 was prepared. A solar cell C3 was produced in the same manner as in Example 1 except that the heat treatment was performed at 650 ° C. for 10 seconds.

<Evaluation>
Evaluation of the produced solar cell was performed by using WXS-155S-10 manufactured by Wacom Denso Co., Ltd. as pseudo-sunlight, and IV CURVE TRACER MP-160 (manufactured by EKO INSTRUMENT Co., Ltd.) as a current-voltage (IV) evaluation measuring instrument. ) Was combined with the measuring device. Eff (conversion efficiency), FF (fill factor), Voc (open-circuit voltage) and Jsc (short-circuit current) indicating the power generation performance as a solar cell are JIS-C-8912, JIS-C-8913 and JIS-C-, respectively. It is obtained by performing measurement according to 8914. The obtained measured values are converted into relative values with the measured value of Comparative Example 2 as 100.0, and are shown in Table 2.

From the above, by using the electrode paste composition of the present invention, it was possible to form an electrode having a low resistivity even when metal particles mainly composed of copper were used as the conductive metal of the electrode. Good power generation performance was exhibited even at a general processing temperature of 850 ° C., but good power generation performance was also exhibited at a processing temperature of 650 ° C., which is a lower temperature region.

The disclosures of Japanese Application 2010-013513 and Japanese Application 2010-222201 are incorporated herein by reference in their entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

130 Semiconductor substrate 131 Diffusion layer 132 Antireflection layer 133 Light receiving surface electrode 134 Current collecting electrode 135 Output extraction electrode 136 Electrode component diffusion layer 1 Cell wafer made of p-type silicon substrate 2 Current collecting grid electrode 3 N-type semiconductor layer 4 Through-hole electrode 5 Highly doped layer 6 Back electrode 7 Back electrode

Claims (4)

An electrode paste composition comprising metal particles mainly composed of copper, phosphorus-containing compounds, glass particles, a solvent, and a resin. The electrode paste composition according to claim 1, wherein the phosphorus-containing compound is at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene. The electrode paste composition according to claim 1 or 2, further comprising silver particles. A solar cell having an electrode formed by firing the electrode paste composition according to any one of claims 1 to 3 applied on a silicon substrate.

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