JP2016066618A - Paste composition for electrode and solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paste composition for an electrode capable of forming an electrode which suppresses oxidization of copper while firing and has low resistivity; and a solar cell having the electrode formed using the paste composition for the electrode.SOLUTION: A paste composition for an electrode is structured so as to include copper-containing particles having a peak temperature of 280°C or higher for an exothermic peak showing a maximum area in differential heat/thermogravimetry simultaneous measurement; glass particles; a solvent; and a resin. A solar cell has the electrode formed using the paste composition for the electrode.SELECTED DRAWING: None

Description

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

  Generally, a crystalline silicon solar cell is provided with a surface electrode. The wiring resistance and contact resistance of the surface electrode are related to voltage loss related to conversion efficiency, and the wiring width and shape affect the amount of incident sunlight. (For example, refer nonpatent literature 1).

  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 onto 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 (for example, see Patent Document 1). Moreover, the composition for electrode formation containing the metal nanoparticle containing silver and metal particles other than silver is disclosed (for example, refer patent document 2).

JP 2006-313744 A JP 2008-226816 A

Akihiro Tsujikawa, “Latest Photovoltaic Power Generation Technology and System”, CMC Publishing Company, 2001, p26-27

  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 composition for forming an electrode described in Patent Document 2, when copper is contained as a conductive metal, this is baked to form an electrode. Therefore, a special process of baking in an atmosphere of nitrogen or the like is necessary.

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

  The first aspect of the present invention is a copper-containing particle having a peak temperature of an exothermic peak showing a maximum area in differential thermal-thermogravimetric simultaneous measurement (TG-DTA), glass particles, a solvent, and a resin. And an electrode paste composition.

  The copper-containing particles include phosphorus-containing copper alloy particles, silver-coated copper particles, and triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. It is preferably at least one selected from copper particles that have been surface-treated with at least one selected from the group.

The glass particles preferably have a glass softening point of 600 ° C. or lower and a crystallization start temperature of more than 600 ° C., and a diphosphorus pentoxide-divanadium pentoxide (P ₂ O ₅ —V ₂ O ₅ ) system. More preferably, glass is included.

  The electrode paste composition preferably further includes silver particles, and the content of the copper-containing particles is 9% by mass to 88% by mass when the total amount of the copper-containing particles and the silver particles is 100% by mass. The following is more preferable. The total content of the copper-containing particles and the silver particles is 70% by mass or more and 94% by mass or less, and the content of the glass particles is 0.1% by mass or more and 10% by mass or less, and the solvent and The total content of the resin is more preferably 3% by mass or more and 29.9% by mass or less.

  The electrode paste composition preferably further includes a phosphorus-containing compound, and the phosphorus-containing compound is at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene. Is more preferable.

  A second aspect of the present invention is an electrode paste composition containing phosphorus-containing copper alloy particles, glass particles, a solvent, and a resin.

The glass particles preferably have a glass softening point of 600 ° C. or lower and a crystallization start temperature of more than 600 ° C., and a diphosphorus pentoxide-divanadium pentoxide (P ₂ O ₅ —V ₂ O ₅ ) system. More preferably, glass is included.

  The electrode paste composition preferably further includes silver particles, and the content of the copper-containing particles is 9% by mass to 88% by mass when the total amount of the copper-containing particles and the silver particles is 100% by mass. The following is more preferable. The total content of the copper-containing particles and the silver particles is 70% by mass or more and 94% by mass or less, and the content of the glass particles is 0.1% by mass or more and 10% by mass or less, and the solvent and The total content of the resin is more preferably 3% by mass or more and 29.9% by mass or less.

  The electrode paste composition preferably further includes a phosphorus-containing compound, and the phosphorus-containing compound is at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene. Is more preferable.

  A third aspect of the present invention is an electrode paste composition containing silver-coated copper particles, glass particles, a solvent, and a resin.

  The glass particles preferably have a glass softening point of 600 ° C. or lower and a crystallization start temperature of 600 ° C. or higher, and more preferably contain diphosphorus pentoxide-bivanadium pentoxide glass.

  The electrode paste composition preferably further includes silver particles, and the content of the copper-containing particles is 9% by mass to 88% by mass when the total amount of the copper-containing particles and the silver particles is 100% by mass. The following is more preferable. The total content of the copper-containing particles and the silver particles is 70% by mass or more and 94% by mass or less, and the content of the glass particles is 0.1% by mass or more and 10% by mass or less, and the solvent and The total content of the resin is more preferably 3% by mass or more and 29.9% by mass or less.

  The electrode paste composition preferably further includes a phosphorus-containing compound, and the phosphorus-containing compound is at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene. Is more preferable.

  In the fourth aspect of the present invention, the surface treatment was performed 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. An electrode paste composition comprising copper particles, glass particles, a solvent, and a resin.

  The glass particles preferably have a glass softening point of 600 ° C. or lower and a crystallization start temperature of 600 ° C. or higher, and more preferably contain diphosphorus pentoxide-bivanadium pentoxide glass.

  The electrode paste composition preferably further includes silver particles, and the content of the copper-containing particles is 9% by mass to 88% by mass when the total amount of the copper-containing particles and the silver particles is 100% by mass. The following is more preferable. The total content of the copper-containing particles and the silver particles is 70% by mass or more and 94% by mass or less, and the content of the glass particles is 0.1% by mass or more and 10% by mass or less, and the solvent and The total content of the resin is more preferably 3% by mass or more and 29.9% by mass or less.

  The electrode paste composition preferably further includes a phosphorus-containing compound, and the phosphorus-containing compound is at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene. Is more preferable.

  The 5th aspect of this invention is a solar cell which has an electrode formed by baking the said paste composition for electrodes provided on the 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. It is a figure which shows an example of the differential thermal-thermogravimetric simultaneous measurement (TG-DTA) of the phosphorus containing copper alloy particle | grains in this invention.

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

<Paste composition for electrodes>
The electrode paste composition of the present invention comprises at least one copper-containing particle having a peak temperature of an exothermic peak having a maximum area of 280 ° C. or more in simultaneous differential thermal-thermogravimetric measurement, at least one glass particle, It contains at least one solvent and at least one resin.
With such a configuration, oxidation of copper during firing is suppressed, and an electrode with low resistivity can be formed.

(Copper-containing particles)
In the copper-containing particles of the present invention, the peak temperature of the exothermic peak showing the maximum area in differential thermal-thermogravimetric simultaneous measurement (TG-DTA) is 280 ° C. or higher. By using such copper-containing particles imparted with oxidation resistance, oxidation of metallic copper during firing is suppressed, and an electrode with low resistivity can be formed. In addition, simultaneous measurement of differential heat-thermogravimetry is performed in a normal atmosphere using a measurement device: differential heat-thermogravimetric analyzer (manufactured by SII Nanotechnology, TG / DTA-6200), for example, measurement temperature Range: room temperature to 1000 ° C., temperature rising rate: 40 ° C./min, atmospheric flow rate: 200 ml / min.
In general, when differential thermal-thermogravimetric simultaneous measurement is performed on pure copper (metallic copper), the peak temperature at the exothermic peak showing the maximum area is around 200 ° C., but in the copper-containing particles used in the present invention, the peak temperature is 280. ℃ or more. Furthermore, in the present invention, from the viewpoint of low resistivity as an electrode, the peak temperature is preferably 280 to 800 ° C, more preferably 290 to 750 ° C, and further preferably 350 to 750 ° C. preferable.

Copper-containing particles having a peak temperature of 280 ° C. or higher at the exothermic peak showing the maximum area can be constituted by imparting oxidation resistance to the copper particles.
Specifically, for example, phosphorus-containing copper alloy particles, silver-coated copper particles, and triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. The copper particle surface-treated by at least 1 sort (s) chosen from a group can be mentioned, It is preferable to use at least 1 sort (s) chosen from these. The copper-containing particles may be used alone or in combination of two or more.

Although there is no restriction | limiting in particular as a particle diameter of the said copper containing particle | grains, It is 0.4 micrometer-10 micrometers as a particle diameter (henceforth "D50%" may be abbreviated as "D50%") when the accumulated weight is 50% Is preferable, and it is more preferable that it is 1 micrometer-7 micrometers. 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 diameter of the copper-containing particles is measured by a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
Moreover, there is no restriction | limiting in particular as a shape of the said copper containing particle | grains, Any of substantially spherical shape, flat shape, block shape, plate shape, scale shape, etc. may be sufficient. The shape of the copper-containing particles is preferably substantially spherical, flat, or plate-like from the viewpoint of oxidation resistance and low resistivity.

As a content rate of the said copper containing particle | grains contained in the paste composition for electrodes of this invention, and the total content rate of the copper containing particle | grains and silver particle in the case of containing the silver particle mentioned later, it shall be 70-94 mass%, for example. In view 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, 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 not limited as long as the peak temperature of the exothermic peak showing the maximum area is 280 ° C. or higher in simultaneous differential heat-thermogravimetric measurement. 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% by mass or more and 8% by mass or less, and 0.5% by mass or more and 7.8% by mass or less. More preferably, the content is 1% by mass or more and 7.5% by mass or less.
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 acid 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 3 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 preferable that the thickness is 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.
Moreover, there is no restriction | limiting in particular as a shape of the said phosphorus containing copper alloy particle, Any of substantially spherical shape, flat shape, block shape, plate shape, scale shape, etc. may be sufficient. The shape of the phosphorus-containing copper alloy particles is preferably substantially spherical, flat, or plate-like from the viewpoint of oxidation resistance and low resistivity.

The phosphorous 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. Details of the water atomization method are described in Metal Handbook (Maruzen Co., Ltd. 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.

As a content rate of the said phosphorus containing copper alloy particle contained in the paste composition for electrodes of this invention, and the total content rate of the phosphorus containing copper alloy particle and silver particle in the case of containing the silver particle mentioned later, for example, 70-94 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 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.

Further, 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% by mass or more and 8% by mass or less are contained in the electrode paste composition. It is preferable to contain -94 mass%, and it is more preferable to contain 74-88 mass% of phosphorus containing copper alloy particles whose phosphorus content rate is 1-7.5 mass% in the paste composition for electrodes.
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 differential thermal-thermogravimetric simultaneous measurement is 280 ° C. or more. It is preferable that Specifically, it can be 1% by mass or more in the total mass of the silver-coated copper particles. Among these, the silver coating amount is preferably 1 to 88% by mass and more preferably 3 to 80% by mass in the total mass of the silver-coated copper particles from the viewpoint of oxidation resistance and the low resistivity of the electrode. Preferably, it is 5-75 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. The thickness 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.
Moreover, there is no restriction | limiting in particular as a shape of the said silver covering copper particle, Any of substantially spherical shape, flat shape, block shape, plate shape, scale shape, etc. may be sufficient. The shape of the silver-coated copper particles is preferably substantially spherical, flat or plate-like from the viewpoint of oxidation resistance and low resistivity.

The copper constituting the silver-coated copper particles may 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 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, for example, 70 to 94% by mass From the viewpoint of oxidation resistance and low resistivity, the content is preferably 72 to 90% by mass, and 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 other than silver covering copper particle | grains, Comprising: The peak temperature in the exothermic peak which shows the maximum area 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 (when silver particles described later are included, the total content of silver-coated copper particles and silver particles) is preferably included, and the silver-coated copper particles having a silver content of 5% to 75% by mass Is more preferably included in the electrode paste composition in an amount of 74 to 88% by mass (the total content of silver-coated copper particles and silver particles when silver particles described later are included).
Further, the 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 are 70 to 94% by mass (described later). In the case of containing silver particles, 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. The silver-coated phosphorus-containing copper alloy particles having a mass% of 74 to 88% by mass in the electrode paste composition (when silver particles described later are included, the total content of the silver-coated phosphorus-containing copper alloy particles and silver particles ) 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 have been 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, p-cumylphenyl derivative of tetraalkoxytitanium, and the like. 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.
Further, 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 kind of the surface treatment agent. 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 based on the total mass of the surface-treated copper particles. Among them, the content of the surface treatment agent is preferably 0.01 to 10% by mass in the total mass of the copper particles from the viewpoint of oxidation resistance and low resistivity of the electrode, and 0.05 to 8% by mass. More preferably.

Copper constituting the surface-treated copper particles may 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 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 copper alloy in the surface-treated copper particle, it is synonymous with the above-mentioned phosphorus containing copper 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.
Moreover, there is no restriction | limiting in particular as a shape of the said surface-treated copper particle, Any of substantially spherical shape, flat shape, block shape, plate shape, scale shape, etc. may be sufficient. The surface-treated copper particles preferably have a substantially spherical shape, a flat shape, or a plate shape from the viewpoint of oxidation resistance and low resistivity.

  The surface treatment method of the copper particles using the 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 used and the desired surface treatment amount. For example, it can be 1-90 mass%, and it is preferable that it is 2-85 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 It can be -94 mass%, and it is preferable that it is 72-90 mass% from a viewpoint of oxidation resistance and a low resistivity, and it is more preferable that it is 74-88 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 other than the surface-treated copper particle | grains, Comprising: The peak temperature in the exothermic peak which shows the maximum area 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. In the electrode paste composition, 70 to 94% by mass of copper particles surface-treated so that at least one kind contained is contained in an amount of 0.01 to 10% by mass. (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 0.05 to 8% by mass. The surface-treated copper particles are 74 to 88% by mass 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 includes 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 not more than 8% by mass were treated with 70 to 94% by mass in the electrode paste composition (in the case of containing silver particles described later, the surface treatment was performed). The total content of phosphorus-containing copper alloy particles and silver particles) is preferably included, and 0.05 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 is included. Surface-treated phosphorus-containing copper alloy particles having a phosphorus content of 1 to 7.5% by mass or less in the paste composition for electrodes. 74-88 wt% (when containing silver particles to be described later, the total content of the surface-treated phosphorous-containing copper alloy particles and the silver particles) more preferably contains.
In the present invention, conductive particles other than the surface-treated copper particles may be used in combination.

(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 normal method using a thermomechanical analyzer (TMA), and the crystallization start temperature is measured using a differential thermal-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 efficiently taken up. Examples of such glass containing lead 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 paragraph numbers 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 glass particles are preferably made of glass containing diphosphorus pentoxide (phosphate glass, P ₂ O ₅ glass) from the viewpoint of low contact resistivity. In addition to diphosphorus pentoxide, divanadium pentoxide. it is more preferably made further comprising glass _{(P 2 O 5 -V 2 O} 5 -based glass). By further containing divanadium pentoxide, the oxidation resistance is further improved, and the resistivity of the electrode is further reduced. This can be attributed to, for example, that the softening point of the glass is lowered by further containing divanadium pentoxide.

When the glass particles are made of diphosphorus pentoxide-divanadium pentoxide glass (P ₂ O ₅ —V ₂ O ₅ glass), the content of divanadium pentoxide is 1 in the total mass of the glass. The content is preferably at least mass%, more preferably from 1 to 70 mass%.

The diphosphorus pentoxide-divanadium pentoxide glass may further contain other components as required. As other components, barium oxide (BaO), manganese dioxide (MnO ₂ ), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), zirconium dioxide (ZrO ₂ ), tungsten trioxide (WO ₃ ), oxidation Examples include tellurium (TeO), molybdenum trioxide (MoO ₃ ), and diantimony trioxide (Sb ₂ O ₃ ). By further including other components, silicon dioxide derived from silicon nitride can be incorporated more efficiently. Further, the softening / dissolution temperature can be further reduced. Furthermore, reaction with copper containing particle | grains and the silver particle contained as needed can be suppressed.

It is also preferable that the glass particles are glass particles not containing divanadium pentoxide. By not containing divanadium pentoxide, rapid softening of the glass particles when the electrode paste composition is heated can be suppressed, and a more homogeneous electrode can be formed.
Examples of the glass component material constituting the glass particles not containing divanadium pentoxide include silicon dioxide (SiO ₂ ), phosphorus oxide (P ₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ), and boron oxide (B ₂ O _3). ), Potassium oxide (K ₂ O), sodium oxide (Na ₂ O), lithium oxide (Li ₂ O), barium oxide (BaO), strontium oxide (SrO), calcium oxide (CaO), magnesium oxide (MgO), Beryllium oxide (BeO), zinc oxide (ZnO), lead oxide (PbO), cadmium oxide (CdO), tin oxide (SnO), zirconium oxide (ZrO ₂ ), tungsten oxide (WO ₃ ), molybdenum oxide (MoO ₃ ) , lanthanum oxide _{(La 2 O} 3), an acid value of niobium _{(Nb 2 O} 5), tantalum oxide _{(Ta 2 O} 5), Of yttrium _{(Y 2 O} 3), titanium oxide _(TiO 2), germanium oxide (GeO2), and the like tellurium oxide (TeO ₂₎ and _(Lu 2 _{O 3)} can be mentioned. Of _{these, SiO 2, P 2 O 5} , Al 2 O 3, B 2 O 3, K 2 O, Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, it is preferable to use at least one selected from ZrO _2, WO _3, and MoO _3, at least one selected from _{SiO 2, P 2 O 5,} Al 2 O 3, B 2 O 3, ZnO, and PbO More preferably, seeds are used.

  As a content rate of the said glass particle, it is preferable that it is 0.1-10 mass% in the total mass of the paste composition for electrodes, It is more preferable that it is 0.5-8 mass%, 1-7 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, as glass _particles, in P _{2 O} 5 _{-V 2} O glass particles preferably contain 0.1 to 10 wt% of _{five glass,} the content of V 2 _{O 5} is 1 mass% or more more preferably include some _P 2 _O 5 _-V 0.5 to 8 wt% glass particles consisting of 2 _{O 5} based _{glass, P} 2 _O 5 -V content of V 2 _{O 5} is at least 1 mass% More preferably, it contains 1 to 7% by mass of glass particles made of ₂ O ₅ glass.
As the glass _{particles, SiO 2, Al 2 O 3} , B 2 O 3, K 2 O, Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO 2 , WO _3, and it also preferably contains 0.1 to 10 wt% glass particles consisting of at least one selected from _{MoO 3, SiO 2, Al 2} O 3, B 2 O 3, ZnO, and from PbO More preferably, it contains 1 to 7% by mass of at least one selected glass particle.

(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.

  There is no restriction | limiting in particular as said solvent. For example, hydrocarbon solvents such as hexane, cyclohexane and toluene; chlorinated hydrocarbon agents 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-toluene Methyl-1,3-pentanediol monopropiolate, 2,2,4-trimethyl-1,3-pentanediol monobutyrate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, Ester solvents of polyhydric alcohols such as 2,2,4-triethyl-1,3-pentanediol monoacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate; 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, and ferrandolene, and mixtures thereof Things.

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

  As the resin, any resin that is usually used in the technical field can be used without particular limitation 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 cellulosic resins and acrylic resins, and more preferably at least one selected from cellulosic resins, from the viewpoint of disappearance during firing. preferable.
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 3% by mass or more and 29.9% by mass or less, and more preferably 5% by mass or more and 25% by mass or less based on the total mass of the electrode paste composition. 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 forming 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 covers the surface of silver particles and 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.

  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 differential thermal-thermogravimetric simultaneous 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 which comprises the said silver particle may contain the other atom mixed unavoidable. 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 preferably smaller than the other particle diameter (D50%), and the ratio of the other particle diameter to any one particle diameter 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 the contact area between metal particles such as copper-containing particles and silver particles in the electrode.

Moreover, as content rate of the silver particle in the paste composition for electrodes of this invention, it is 8.4-85.5 mass% in an electrode paste composition from a viewpoint of oxidation resistance and the low resistivity of an electrode. Is preferable, and it is more preferable that it is 8.9-80.1 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. It is preferable to become 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. In addition, in the hydrofluoric acid aqueous solution treatment of the electrode-formed silicon substrate for the purpose of improving the energy conversion efficiency of a solar cell, the electrode material is resistant to hydrofluoric acid (the property that the electrode material does not peel off from the silicon substrate by the hydrofluoric acid aqueous solution). Will improve.
Moreover, it becomes more suppressed that the content rate of the said copper containing particle | grain becomes 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 preferable that it is mass% or less, and it is more preferable that it is 74 mass% or more and 88 mass% or less. 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 glaze 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.

  Furthermore, 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, Preferably, the glass particle content is 0.1% by mass or more and 10% by mass or less, and the total content of the solvent and the resin is 3% by mass or more and 29.9% by mass or less. The total content of the particles and the silver particles is 74 mass% or more and 88 mass% or less, the content of the glass particles is 0.5 mass% or more and 8 mass% or less, and the total content of the solvent and the resin The content is more preferably 7% by mass or more and 20% 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 the content of the glass particles is 1% to 7% by mass It is more preferable that the total content of the solvent and the resin is not more than 20 wt% 7 wt% or more.

(Phosphorus-containing compound)
The electrode paste composition preferably further includes at least one phosphorus-containing compound. Thereby, oxidation resistance improves more effectively and the resistivity of an electrode falls more. Furthermore, in the silicon substrate, the element in the phosphorus-containing compound diffuses as an n-type dopant, and the effect that the power generation efficiency is further improved when a solar cell is obtained.
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 phosphorus-based inorganic acids such as phosphoric acid, phosphates such as ammonium phosphate, phosphate esters such as phosphate alkyl esters and aryl phosphate 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 phosphate esters and cyclic phosphazenes.

As content of the said phosphorus containing compound in this invention, it is preferable that it is 0.5-10 mass% in the total mass of the paste composition for electrodes from a viewpoint of oxidation resistance and the low resistivity of an electrode. More preferably, it is -7 mass%.
Further, 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 1 mass%, and it is more preferable to contain 1-7 mass% of at least 1 sort (s) chosen from the group which consists of phosphate ester and cyclic phosphazene in the total mass of the paste composition for electrodes.

  Further, when the electrode paste composition of the present invention contains a phosphorus-containing compound, the total content of the copper-containing particles and the silver particles is from 70% by mass to 94% by mass from the viewpoint of oxidation resistance and low resistivity of the electrode. It is below, Comprising: The content rate of the said glass particle is 0.1 mass% or more and 10 mass% or less, Comprising: The total content rate of the said solvent, the said resin, and the said phosphorus containing compound is 3 mass% or more and 29.9 mass%. The total content of the copper-containing particles and the silver particles is preferably 74% by mass or more and 88% by mass or less, and the content of the glass particles is 0.5% by mass or more and 8% by mass or less. The total content of the solvent, the resin and the phosphorus-containing compound is more preferably 7% by mass or more and 20% by mass or less, and the total content of the copper-containing particles and the silver particles is 74% by mass or more. 88% by mass or less, Serial content of the glass particles 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 20 mass% or less 7 mass% 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 adhesiveness of an electrode material and a silicon substrate improves is also acquired.

  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, valmitic acid, stearic acid, sorbic acid, threarolic acid, boron oxide, potassium borate, sodium borate, lithium borate, potassium borofluoride, sodium borofluoride, lithium borofluoride , Acidic potassium fluoride, sodium acidic fluoride, acidic lithium fluoride, potassium fluoride, sodium fluoride, lithium fluoride and the like.
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 low temperatures 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. From the total mass of the electrode paste composition, it 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 particularly preferably 0.7 to 3% by mass, and 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 restriction | limiting in particular as a manufacturing method of the paste composition for electrodes of this 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 ink jet 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, it can be set as 2-10 g / m < ² > as a paste composition application amount for electrodes, and it is preferable that it is 4-8 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 (baking temperature) is 800 to 900 ° C., but 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 or the like, and can be set to, 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 side is doped with phosphorus or the like, an n-type semiconductor diffusion layer 131 is provided with a thickness of submicron order, 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 heavily 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.

  On the opposite surface side, as shown in the plan view of FIG. 4 (b), the electrode paste composition according to the present invention is printed on the stripes on both the n side and the p side, respectively, and fired, whereby the back 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 using the electrode paste composition, so that copper is contained 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.

  EXAMPLES The present invention will be specifically described below with reference to examples, but 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 A phosphorus-containing copper alloy containing 1% by mass of phosphorus was prepared, dissolved and powdered by the water atomization method, and then dried and classified. The classified powders were blended and subjected to deoxygenation / dehydration treatment to produce phosphorus-containing copper alloy particles containing 1% by mass of phosphorus. The particle diameter (D50%) of the phosphorus-containing copper alloy particles was 1.5 μm.
In addition, differential thermal-thermogravimetric simultaneous measurement (TG-DTA) is performed in a normal atmosphere using a measuring device: differential thermal-thermogravimetric analyzer (TG / DTA-6200, manufactured by SII Nanotechnology). Measurement temperature range: room temperature to 1000 ° C., heating rate: 40 ° C./min, atmospheric flow rate: 200 ml / min. Exotherm showing maximum area in differential thermal-thermogravimetric simultaneous measurement (TG-DTA) The peak temperature of the peak was 292 ° C.

32 parts of vanadium oxide (V ₂ O ₅ ), 26 parts of phosphorus oxide (P ₂ O ₅ ), 10 parts of barium oxide (BaO), 10 parts of tungsten oxide (WO ₃ ), 1 part of sodium oxide (Na ₂ O), oxidation A glass composed of 3 parts of potassium (K ₂ O), 10 parts of zinc oxide (ZnO), and 8 parts of manganese oxide (ZnO) (hereinafter sometimes abbreviated as “G19”) was prepared. The obtained glass G19 had a softening point of 447 ° C. and a crystallization temperature of over 600 ° C.
By using the obtained glass G19, glass particles having a particle diameter (D50%) of 1.7 μm were obtained.

  39.2 parts of the phosphorus-containing copper alloy particles obtained above, 45.9 parts of silver particles (particle diameter (D50%) 3 μm, high-purity chemical product manufactured by Aldrich), 1.7 parts of glass particles, and 13.2 parts of a butyl carbitol acetate (BCA) solution containing 4% ethyl cellulose (EC) was mixed and stirred for 20 minutes in an agate mortar 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 750 ° C. instead of 850 ° C. Produced.

<Examples 3 to 15 and Examples 43 to 46>
In Example 1, the phosphorus content of the phosphorus-containing copper alloy particles, the particle diameter (D50%) and the content, the particle diameter of the silver particles (D50%) and the content, the type and content of the glass particles, 4% Except that the content of butyl carbitol acetate (BCA) solution containing ethyl cellulose (EC) and the type and content of phosphorus-containing compounds contained as necessary were changed as shown in Table 1. In the same manner as in Example 1, electrode paste compositions 3 to 15 and electrode paste compositions 43 to 46 were prepared.
The glass particles (AY1) are composed of 45 parts of vanadium oxide (V ₂ O ₅ ), 24.2 parts of phosphorus oxide (P ₂ O ₅ ), 20.8 parts of barium oxide (BaO), and antimony oxide (Sb ₂ O _3). ) 5 parts and 5 parts of tungsten oxide (WO ₃ ), and the particle diameter (D50%) was 1.7 μm. The glass had a softening point of 492 ° C. and a crystallization temperature of over 600 ° C.
Glass particles (D10) are composed of 64 parts of lead oxide (PbO), 11 parts of boron oxide (B ₂ O ₃ ), 5 parts of aluminum oxide (Al ₂ O ₃ ), 10 parts of silicon dioxide (SiO ₂ ), zinc oxide ( It consisted of 10 parts of ZnO) and the particle size (D50%) was 2.3 μm. The glass had a softening point of 440 ° C. and a crystallization temperature of over 600 ° C.
Furthermore, triphenyl phosphate was used as the phosphate ester, and hexaphenoxyphosphazene was used as the cyclic phosphazene.

  Next, Examples were used except that the obtained electrode paste compositions 3 to 15 and electrode paste compositions 43 to 46 were used, respectively, and the heat treatment temperature and treatment time were changed as shown in Table 1. In the same manner as in Example 1, solar cells 3 to 15 and solar cells 43 to 46 on which desired electrodes were formed were produced.

<Comparative Example 1>
For electrode preparation in the same manner as in Example 1, except that the phosphorus-containing copper alloy particles were not used in the preparation of the electrode paste composition in Example 1 and each component was changed to the composition shown in Table 1. Paste composition C1 was prepared.
A solar cell C1 was produced in the same manner as in Example 1 except that the electrode paste composition C1 containing no phosphorus-containing copper alloy particles was used.

<Comparative Example 2>
In Comparative Example 1, a solar cell C2 was produced in the same manner as in Comparative Example 1, except that the temperature of the heat treatment (firing) at the time of electrode formation was changed to 750 ° C. instead of 850 ° C.

<Comparative Example 3>
An electrode paste composition C3 was prepared in the same manner as in Example 1 except that in Example 1, pure copper not containing phosphorus (phosphorus content was 0%) was changed.
A solar cell C3 was produced in the same manner as in Example 1 except that the electrode paste composition C3 was used.

<Evaluation>
Evaluation of the produced solar cell is WXS-155S-10 manufactured by Wacom Denso Co., Ltd. as pseudo-sunlight, and I-V CURVE TRACER MP-160 (manufactured by EKO INSTRUMENT, Inc.) 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 1 as 100.0, and are shown in Table 2.
In Comparative Example 3, the resistivity of the electrode increased due to the oxidation of the copper particles, and evaluation was impossible.

The performances of the solar cells produced in Examples 1 to 15 and Examples 43 to 46 were almost the same as the measured values of Comparative Example 1. In particular, the solar cells 44 to 46 formed electrodes without using silver particles, but exhibited high power generation performance.
Further, as a result of measuring diffraction X-rays by X-ray diffractometry using CuKα rays as the light-receiving surface electrode, it was found that the diffraction angles (2θ, CuKα rays) were at least 43.4 °, 50.6 °, 74.2 ° and copper The characteristic diffraction peak was shown. The following principle can be cited as the reason why copper is detected from the light receiving surface electrode. First, the phosphorus-containing copper alloy particles in the electrode paste compositions 44 to 46 have a phosphorus content of 7% by mass. This composition consists of a Cu phase and a Cu ₃ P phase from a Cu—P phase diagram. In the initial stage of firing, the Cu phase is oxidized and changed to CuO. It is considered that this CuO and Cu ₃ P react to form a Cu phase.

Among the obtained phosphorus-containing copper alloy particles, a phosphorus-containing copper particle having a phosphorus content of 7% by mass and a particle diameter (D50%) of 5.0 μm is subjected to a differential thermal-thermogravimetric analyzer in a normal atmosphere. (TG / DTA-6200, manufactured by SII NanoTechnology Inc.), measurement temperature range: room temperature to 1000 ° C., temperature rising rate: 40 ° C./min, atmospheric flow rate: 200 ml / min, differential heat -Simultaneous thermogravimetric measurement (TG-DTA) was performed. The results are shown in FIG.
FIG. 5 shows that in this phosphorus-containing copper alloy particle, the peak temperature of the exothermic peak showing the maximum area is 420 ° C.

<Example 16>
Using the electrode paste composition 1 obtained above, a solar cell 16 having a structure as shown in FIG. 4 was produced. The heat treatment was performed at 750 ° C. for 10 seconds.
When the obtained solar battery cell was evaluated in the same manner as described above, it was found that the same characteristics as described above were exhibited.

<Example 17>
(A) Preparation of electrode paste composition Silver-coated copper particles prepared by the method described in JP-A-14-100191 (manufactured by Hitachi Chemical Co., Ltd., silver coating amount 20 mass%, particle diameter 5.8 μm) 85.1 parts, 1.7 parts of glass particles, and 13.2 parts of a butyl carbitol acetate (BCA) solution containing 4% ethyl cellulose (EC) are mixed together and stirred for 20 minutes in an agate mortar. An electrode paste composition 17 was prepared.

(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 17 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 17 on which a desired electrode was formed.

<Examples 18 to 25>
In Example 17, the silver coating amount and content of the silver-coated copper particles, the particle diameter (D50%) of the silver particles used as necessary, and the content, the type and content of the glass particles, and 4% Electrode paste compositions 18 to 25 were prepared in the same manner as in Example 17 except that the content of the butyl carbitol acetate (BCA) solution containing ethyl cellulose (EC) was changed as shown in Table 3.
As the silver particles, high-purity chemicals manufactured by Aldrich with a particle size (D50%) of 1 μm or 3 μm were used.

  Next, using the obtained electrode paste compositions 18 to 25, a desired electrode was formed in the same manner as in Example 17 except that the temperature and time of the heat treatment were changed as shown in Table 3. The produced solar battery cells 18 to 25 were produced.

<Comparative Example 4>
The electrode paste was prepared in the same manner as in Example 17 except that the silver-coated copper particles were not used in the preparation of the electrode paste composition in Example 17 and each component was changed to the composition shown in Table 3. Composition C4 was prepared.
A solar cell C4 was produced in the same manner as in Example 17 except that the electrode paste composition C4 containing no silver-coated copper particles was used.

<Comparative Example 5>
In Comparative Example 4, a solar cell C5 was produced in the same manner as in Comparative Example 4 except that the temperature of the heat treatment (firing) at the time of electrode formation was changed to 750 ° C. instead of 850 ° C.

<Comparative Example 6>
The electrode paste was prepared in the same manner as in Example 17 except that the silver-coated copper particles were not used in the preparation of the electrode paste composition in Example 17 and each component was changed to the composition shown in Table 3. Composition C6 was prepared.
A solar cell C6 was produced in the same manner as in Example 17 except that the electrode paste composition C6 was used.

<Evaluation>
Evaluation of the produced solar cell is WXS-155S-10 manufactured by Wacom Denso Co., Ltd. as pseudo-sunlight, and I-V CURVE TRACER MP-160 (manufactured by EKO INSTRUMENT, Inc.) 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 4 as 100.0, and are shown in Table 4.
In Comparative Example 6, the resistivity of the electrode increased due to the oxidation of the copper particles, and evaluation was impossible.

<Example 26>
Using the electrode paste composition 19 obtained above, a solar battery cell 26 having a structure as shown in FIG. 4 was produced. The heat treatment was performed at 750 ° C. for 10 seconds.
When the obtained solar battery cell was evaluated in the same manner as described above, it was found that the same characteristics as described above were exhibited.

<Example 27>
(A) Preparation of electrode paste composition Benzotriazole (BTA) as a surface treatment agent was dissolved in a solvent ethanol to prepare a 50% surface treatment solution. Copper powder (Fukuda Metal Foil Powder Co., Ltd., purity 99.9%, particle diameter 5 μm) was immersed in this for 50 minutes, and then dried to prepare surface-treated copper particles. The content of the surface treatment agent in the surface-treated copper particles was 1% in the total mass of the surface-treated copper particles. The particle diameter (D50%) was 5 μm.

  39.2 parts of the surface-treated copper particles obtained above, 45.9 parts of silver particles (particle diameter (D50%) 3 μm, high-purity chemical product manufactured by Aldrich), 1.7 parts of glass particles, Then, 13.2 parts of a butyl carbitol acetate (BCA) solution containing 4% ethylcellulose (EC) was mixed and stirred in an agate mortar for 20 minutes to prepare an electrode paste composition 27.

(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 27 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, a 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 27 on which a desired electrode was formed.

<Examples 28 to 41>
In Example 27, the type and content of the surface treatment agent for the surface-treated copper particles, the content of silver particles, the type and content of glass particles, butyl carbitol acetate (BCA) containing 4% ethyl cellulose (EC) ) Electrode paste composition 28 in the same manner as in Example 41 except that the content of the solution and the type and content of the phosphorus-containing compound contained as necessary were changed as shown in Table 5. ~ 41 were prepared.

  Next, using the obtained electrode paste compositions 28 to 41, the desired electrode was formed in the same manner as in Example 27, except that the temperature and time of the heat treatment were changed as shown in Table 5. The produced solar battery cells 28 to 41 were produced.

<Comparative Example 7>
The electrode was prepared in the same manner as in Example 27 except that each component was changed to the composition shown in Table 5 without using the surface-treated copper particles in the preparation of the electrode paste composition in Example 27. Paste composition C7 was prepared.
A solar cell C7 was produced in the same manner as in Example 27 except that the electrode paste composition C7 containing no surface-treated copper particles was used.

<Comparative Example 8>
In Comparative Example 7, a solar cell C8 was produced in the same manner as in Comparative Example 7, except that the temperature of the heat treatment (firing) at the time of electrode formation was changed to 750 ° C. instead of 850 ° C.

<Comparative Example 9>
In Example 27, except that the surface treatment amount of the surface-treated copper particles was changed to 0.0001% where the peak temperature of the exothermic peak showing the maximum area in differential thermal-thermogravimetric simultaneous measurement was 230 ° C. In the same manner as in Example 27, an electrode paste composition C9 was prepared.
A solar cell C9 was produced in the same manner as in Example 27 except that the electrode paste composition C9 was used.

<Evaluation>
Evaluation of the produced solar cell is WXS-155S-10 manufactured by Wacom Denso Co., Ltd. as pseudo-sunlight, and I-V CURVE TRACER MP-160 (manufactured by EKO INSTRUMENT, Inc.) 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 were converted into relative values with the measured value of Comparative Example 7 as 100.0, and are shown in Table 6.
In Comparative Example 9, the resistivity of the electrode increased due to oxidation of the copper-containing particles, and evaluation was impossible.

<Example 42>
Using the electrode paste composition 27 obtained above, a solar battery cell 42 having a structure as shown in FIG. 4 was produced. The heat treatment was performed at 750 ° C. for 10 seconds.
When the obtained solar battery cell was evaluated in the same manner as described above, it was found that the same characteristics as described above were exhibited.

  From the above, by using the electrode paste composition of the present invention, even if copper is used as the conductive metal of the electrode, an electrode with low resistivity can be formed, and a solar cell exhibiting excellent characteristics can be configured. I understand that. Moreover, it turns out that the performance equivalent to or more than the conventional electrode paste composition using silver was shown also in the processing temperature (baking temperature) of 750 degreeC and 850 degreeC.

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 (13)

  The paste composition for electrodes containing the copper containing particle | grains whose peak temperature of the exothermic peak which shows the maximum area in a differential thermal-thermogravimetric simultaneous measurement is 280 degreeC or more, glass particle | grains, a solvent, and resin.   The copper-containing particles include phosphorus-containing copper alloy particles, silver-coated copper particles, and triazole compounds, saturated fatty acids, unsaturated fatty acids, inorganic metal compound salts, organometallic compound salts, polyaniline resins, and metal alkoxides. The electrode paste composition according to claim 1, which is at least one selected from copper particles surface-treated with at least one selected from the group.   3. The electrode paste composition according to claim 1, wherein the glass particles have a glass softening point of 600 ° C. or lower and a crystallization start temperature exceeding 600 ° C. 3.   The electrode paste composition according to any one of claims 1 to 3, wherein the glass particles include diphosphorus pentoxide-divanadium pentoxide glass.   The paste composition for electrodes according to any one of claims 1 to 4, further comprising silver particles.   The paste composition for an electrode according to claim 5, wherein the content of the copper-containing particles is 9% by mass or more and 88% by mass when the total amount of the copper-containing particles and the silver particles is 100% by mass.   The total content of the copper-containing particles and the silver particles is 70% by mass or more and 94% by mass or less, and the content of the glass particles is 0.1% by mass or more and 10% by mass or less. The paste composition for an electrode according to claim 5 or 6, wherein the total resin content is 3% by mass or more and 29.9% by mass or less.   The electrode paste composition according to any one of claims 1 to 7, further comprising a phosphorus-containing compound.   The electrode paste composition according to claim 8, wherein the phosphorus-containing compound is at least one selected from the group consisting of phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene.   An electrode paste composition containing phosphorus-containing copper alloy particles, glass particles, a solvent, and a resin.   A paste composition for an electrode comprising copper particles coated with silver, glass particles, a solvent, and a resin.   Copper particles surface-treated 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, glass particles, and solvents And a paste composition for an electrode comprising a resin.   The solar cell which has an electrode formed by baking the paste composition for electrodes of any one of Claims 1-12 given on the silicon substrate.