JP2015079975A - Element, solar cell, and paste composition for electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an element including a copper-containing electrode in which oxidation of a copper is suppressed at the time of calcination and good ohmic contact is obtained, the electrode being formed on a silicon-containing substrate of the element, and to provide a paste composition for electrodes suitable for arranging the element.SOLUTION: The element includes the silicon-containing substrate and the electrode provided on the substrate, where the electrode is a burned product of the paste composition for the electrodes containing copper-containing particles, glass particles, a solvent and a resin, and has a volume resistivity of 1×10Ω cm or less. Moreover, the paste composition for the electrodes is arranged so as to include phosphorus-containing copper alloy particles, tin-containing particles, the glass particles, the solvent, and the resin and to have a viscosity at 25°C in a range of 80 Pa s to 1000 Pa s. Furthermore, the paste composition for the electrodes is arranged so as to include the phosphorus-containing copper alloy particles, the tin-containing particles, the glass particles, the solvent, and the resin, and to have a solid content concentration in a range of 70 mass% to 98 mass%.

Description

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

  In general, electrodes are formed on the light receiving surface and the back surface of a silicon-based solar cell. In order to efficiently extract the electrical energy converted in the solar cell by the incidence of light to the outside, it is necessary that the volume resistivity of the electrode is sufficiently low and that a good ohmic contact is formed with the Si substrate. is there. In particular, the electrode on the light receiving surface tends to have a small wiring width and a high aspect ratio in order to minimize the amount of incident light loss of sunlight.

  The electrode used for the light-receiving surface of the solar cell is usually formed as follows. That is, a texture (unevenness) is formed on the light-receiving surface side of a p-type silicon substrate, and then a conductive composition is screen-printed on an n-type silicon layer formed by thermally diffusing phosphorus or the like at a high temperature. The light-receiving surface electrode is formed by applying this and baking it at 800 to 900 ° C. in the atmosphere. The conductive composition forming the light-receiving surface electrode includes conductive metal powder, glass particles, various additives, and the like.

As the conductive metal powder, silver powder is generally used. This is because the volume resistivity of the silver particles is as low as 1.6 × 10 ⁻⁶ Ω · cm, the silver particles are self-reduced and sintered under the above firing conditions, and a good ohmic contact is formed with the silicon substrate. In addition, the tab material for electrically connecting the solar cell elements is preferably used in so-called modularization in which the solder material has excellent wettability with respect to the electrode made of silver particles and the solar cell element is sealed with a glass substrate or the like. The reason is that it can be bonded.

  As described above, the conductive composition containing silver particles exhibits excellent characteristics as an electrode of a solar cell. On the other hand, since silver is a noble metal and the bullion itself is expensive, and also from the problem of resources, a proposal of a paste material that replaces the silver-containing conductive composition 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 in the atmosphere, and it is difficult to form an electrode in the above process.

  In order to solve the above-mentioned problems of copper, copper particles that have been given oxidation resistance using various techniques and are not oxidized even by high-temperature firing have been reported (for example, Patent Document 1 and Patent Document 2).

JP 2005-314755 A Japanese Patent Laid-Open No. 2004-217952

  However, even the above copper particles have oxidation resistance up to 300 ° C. and are almost oxidized at a high temperature of 800 to 900 ° C., so that they have not been put into practical use as solar cell electrodes. Furthermore, the additive applied in order to provide oxidation resistance inhibits sintering of the copper particles during firing, and as a result, there is a problem that a low resistance electrode such as silver cannot be obtained.

  Another method for suppressing copper oxidation is a special process in which a conductive composition using copper as a conductive metal powder is fired in an atmosphere of nitrogen or the like.

  However, when the above method is used, an environment completely sealed with the above atmospheric gas is required to completely suppress the oxidation of the copper particles, which is not suitable for mass production of solar cells in terms of process costs.

Another problem for applying copper to solar cell electrodes is ohmic contact with a silicon substrate. That is, even if an electrode made of copper can be formed without being oxidized during high-temperature firing, copper and silicon are in direct contact with each other, thereby causing mutual diffusion of copper and silicon, and copper at the interface between the electrode and the silicon substrate. In some cases, a reactant phase (Cu ₃ Si) composed of silicon and silicon is formed.

The formation of Cu ₃ Si may extend to several μm from the interface of the silicon substrate, and may crack on the Si substrate side. In some cases, the semiconductor performance (pn junction characteristics) of the solar cell is deteriorated by penetrating an n-type silicon layer formed in advance on the silicon substrate. In addition, the formed Cu ₃ Si lifts the electrode made of copper, which may hinder the adhesion with the silicon substrate and cause a decrease in the mechanical strength of the electrode.

  The present invention has been made in view of the above problems, and includes an element in which copper-containing electrodes having good ohmic contact are formed on a substrate containing silicon, the oxidation of copper during firing being suppressed, and the element It aims at providing the paste composition for electrodes suitable for comprising a solar cell and this element.

  The present inventors completed the present invention as a result of intensive studies in order to solve the above problems. That is, the present invention is as follows.

1st aspect of this invention has a board | substrate containing silicon, and the electrode arrange | positioned on the said board | substrate, The said electrode is a paste composition for electrodes containing copper containing particle | grains, glass particle | grains, a solvent, and resin. It is a fired product and an element having a volume resistivity of 1 × 10 ⁻⁴ Ω · cm or less.

  The copper-containing particles are preferably phosphorus-containing copper alloy particles, and the phosphorus content of the phosphorus-containing copper alloy particles is more preferably 6% by mass or more and 8% by mass or less.

  The electrode paste composition preferably further includes tin-containing particles, and the tin-containing particles are at least one selected from tin particles and tin alloy particles having a tin content of 1% by mass or more. More preferred.

  The glass particles preferably have a glass softening point of 650 ° C. or lower and a crystallization start temperature exceeding 650 ° C.

  When the paste composition for an electrode includes phosphorus-containing copper alloy particles and tin-containing particles, the content of the tin-containing particles when the total content of the phosphorus-containing copper alloy particles and the tin-containing particles is 100% by mass. However, it is preferable that they are 5 mass% or more and 70 mass% or less.

  The electrode paste composition preferably further includes silver particles, and the content of the silver particles when the total content of the phosphorus-containing copper alloy particles, the tin-containing particles, and the silver particles is 100% by mass. Is more preferably 0.1% by mass or more and 10% by mass or less, and the total content of the phosphorus-containing copper alloy particles, tin-containing particles and silver particles is 70% by mass or more and 94% by mass or less, and the glass More preferably, the content of the particles 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 electrode preferably includes a Cu-Sn alloy phase and a Sn-PO glass phase, and the Sn-PO glass phase is disposed between the Cu-Sn alloy phase and the silicon-containing substrate. More preferably.

  The element is preferably a solar cell element.

  The 2nd aspect of this invention is a solar cell which has the said element and the tab wire arrange | positioned on the electrode of the said element.

  A third aspect of the present invention is an electrode paste composition containing phosphorus-containing copper alloy particles, tin-containing particles, glass particles, a solvent and a resin, and having a viscosity at 25 ° C. in the range of 80 Pa · s to 1000 Pa · s. is there.

  A fourth aspect of the present invention is an electrode paste composition containing phosphorus-containing copper alloy particles, tin-containing particles, glass particles, a solvent and a resin, and having a solid content in the range of 70% by mass to 98% by mass. .

  According to the present invention, the oxidation of copper during firing is suppressed, and an element in which a copper-containing electrode having a good ohmic contact is formed on a substrate containing silicon, a solar cell having the element, and the element Therefore, a suitable electrode paste composition can be provided.

It is a schematic sectional drawing which shows an example of the silicon type solar cell element concerning this invention. It is a schematic plan view which shows an example of the light-receiving surface of the silicon type solar cell element concerning this invention. It is a schematic plan view which shows an example of the back surface of the silicon type solar cell element concerning this invention. It is a schematic plan view which shows an example of the back surface side electrode structure of the back contact type solar cell element concerning this invention. It is a schematic perspective view which shows an example of AA cross-section structure of the back contact type solar cell element concerning this invention. It is a schematic perspective view which shows an example of AA cross-section structure of the back contact type solar cell element concerning this invention. It is a schematic perspective view which shows an example of AA cross-section structure of the back contact type solar cell element concerning this invention.

In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended action of the process is achieved even when it cannot be clearly distinguished from other processes. .
In the present specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
Further, when referring to the amount of each component in the composition in the present specification, when there are a plurality of substances corresponding to each component in the composition, the plurality of the components present in the composition unless otherwise specified. It means the total amount of substance.

<Element>
The element of the present invention has a substrate containing silicon and an electrode disposed on the substrate, and the electrode is made of an electrode paste composition containing copper-containing particles, glass particles, a solvent and a resin. It is a fired product and has a volume resistivity of 1 × 10 ⁻⁴ Ω · cm or less.
The electrode is a fired product of an electrode paste composition having a specific configuration, so that the volume resistivity is low, oxidation of copper during firing is suppressed, and a copper-containing electrode having a good ohmic contact is made of silicon. An element formed on a substrate including the substrate can be formed.

The electrode has a volume resistivity of 1 × 10 ⁻⁴ Ω · cm or less, more preferably 8 × 10 ⁻⁵ Ω · cm or less, and more preferably 1 × 10 ⁻⁶ Ω · cm to 6 × 10 ⁻ More preferably, it is ⁶ Ω · cm or less.
The volume resistivity of the electrode is measured as follows.
The electrode paste composition of the present invention is applied on a desired substrate and fired under predetermined conditions to obtain a fired product. Subsequently, volume resistivity is measured by the resistivity meter (For example, Mitsubishi Chemical Corporation Loresta-EP MCP-T360 type resistivity meter) about the obtained baked product.

In the present invention, examples of the method of setting the volume resistivity of the electrode in the above range include a method of appropriately selecting the conditions for the firing treatment, and a method of configuring the electrode paste composition to be described later.
In particular, as will be described later as the electrode paste composition, copper-containing particles having oxidation resistance (preferably phosphorus-containing copper alloy particles) are used as the copper-containing particles, and tin-containing particles are combined with the copper-containing particles. The temperature can be lowered, and an electrode having a lower volume resistivity can be formed even if the baking treatment is performed in the presence of oxygen (for example, in the air). Furthermore, a more excellent ohmic contact can be achieved by combining glass particles having a specific structure described later with a low softening point.

The substrate containing silicon is not particularly limited, and examples include a silicon substrate for forming a solar cell, a silicon substrate used for manufacturing a semiconductor device other than a solar cell, and the like, and is a silicon substrate for forming a solar cell. preferable.
Specifically, the element of the present invention can constitute a solar cell element, an electrode wiring and a shield wiring of a plasma display, a ceramic capacitor, an antenna circuit, various sensor circuits, a heat dissipation material for a semiconductor device, and the like.
Among these, it is preferable that the said element is a solar cell element.

For example, the device includes applying an electrode paste composition containing copper-containing particles, glass particles, a solvent, and a resin onto a substrate containing silicon, and baking the resultant to form an electrode on the substrate containing silicon. It can be formed and configured. The details of the electrode paste composition will be described later.
Moreover, the shape of the electrode paste composition provided on the substrate containing silicon is not particularly limited and can be appropriately selected depending on the purpose.

  The method for applying the electrode paste composition onto the substrate containing silicon is not particularly limited. For example, screen printing, an ink jet method, a dispenser method, and the like can be mentioned. From the viewpoint of productivity, application by screen printing is preferable.

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 is possible to ^2g / ^{m 2 ~10g} / m 2 as an electrode paste composition for application amount ^is preferably ^{4g / m 2 ~8g / m 2} .

Moreover, as conditions for baking the electrode paste composition applied on the substrate containing silicon, heat treatment conditions that are usually used in this technical field can be applied.
Generally, the heat treatment temperature (firing temperature) is 800 to 900 ° C., but when using the electrode paste composition described later, heat treatment conditions at a lower temperature can be applied, for example, 450 to 850 ° C. It is possible to form an electrode having good characteristics at the heat treatment temperature.
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.
Moreover, the atmosphere of a baking process is not restrict | limited in particular. It may be in an inert gas atmosphere such as nitrogen or in an atmosphere in which oxygen exists such as in the air. In the present invention, from the viewpoint of productivity, the baking treatment is preferably performed in an air atmosphere.

  Any heat treatment apparatus can be used as long as it can be heated to the above temperature, and examples thereof include an infrared heating furnace and a tunnel furnace. An infrared heating furnace is highly efficient because electric energy is directly input to a heating material in the form of electromagnetic waves and is converted into heat energy, and rapid heating is possible in a short time. Further, since there is no product due to combustion and non-contact heating, it is possible to suppress contamination of the generated electrode. Since the tunnel furnace automatically and continuously conveys the sample from the entrance to the exit and fires it, it can be fired uniformly by dividing the furnace body and controlling the transport speed. From the viewpoint of the power generation performance of the solar battery cell, it is preferable to perform heat treatment with a tunnel furnace.

<Solar cell element and manufacturing method thereof>
The element of the present invention is preferably a solar cell element.
The solar cell element has an electrode formed by firing an electrode paste composition applied on a silicon substrate. Thereby, the solar cell element which has a favorable characteristic is obtained, and it is excellent in productivity of this solar cell element.
In this specification, the solar cell element means one having a silicon substrate on which a pn junction is formed and an electrode formed on the silicon substrate. In addition, the solar cell is a state in which a tab wire is provided on the electrode of the solar cell element, and a plurality of solar cell elements are connected via the tab line as necessary and sealed with a sealing resin or the like. Means things.

Hereinafter, although the specific example of the solar cell element 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.
As schematically shown in FIG. 1, single crystal or polycrystalline silicon is usually used for the semiconductor substrate 1 of the solar cell element. The semiconductor substrate 1 contains boron and constitutes a p-type semiconductor. In order to suppress reflection of sunlight on the light receiving surface side, irregularities (also referred to as texture, not shown) are formed by an etching solution made of NaOH and IPA (isopropyl alcohol). Phosphorus or the like is doped on the light receiving surface side, the n ⁺ diffusion layer 2 is provided with a thickness of the order of submicron, and a pn junction is formed at the boundary with the p-type bulk portion. Further, on the light receiving surface side, an antireflection film 3 such as silicon nitride is provided on the n ⁺ diffusion layer 2 with a film thickness of about 90 nm by PECVD or the like.

Next, a method of forming the light receiving surface electrode 4 provided on the light receiving surface side schematically shown in FIG. 2, and the current collecting electrode 5 and the output extraction electrode 6 formed on the back surface schematically shown in FIG.
The light-receiving surface electrode 4 and the back surface output extraction electrode 6 are formed from the electrode paste composition of the present invention. The back current collecting electrode 5 is formed of an aluminum electrode paste composition containing glass powder. As a first method for forming the light-receiving surface electrode 4, the back surface collecting electrode 5 and the back surface output extraction electrode 6, the paste composition is applied to a desired pattern by screen printing or the like, then dried, and then in the atmosphere. It may be formed by firing at about 450 to 850 ° C. at the same time. 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 4 react with the antireflection layer 3 (fire-through), and the light receiving surface electrode 4 and the n ⁺ The diffusion layer 2 is electrically connected (ohmic contact).
In the present invention, the light-receiving surface electrode 4 is formed using the electrode paste composition, so that copper is suppressed as a conductive metal, and copper oxidation is suppressed. , Formed with good productivity.
Furthermore, in the present invention, it is preferable that the formed electrode includes a Cu—Sn alloy phase and a Sn—P—O glass phase, and the Sn—P—O glass phase includes a Cu—Sn alloy phase and a silicon substrate. (Not shown) is more preferable. As a result, the reaction between copper and the silicon substrate is suppressed, and an electrode having low resistance and excellent adhesion can be formed.

Further, on the back surface side, aluminum in the aluminum electrode paste composition that forms the back surface collecting electrode 5 at the time of firing diffuses to the back surface of the p-type silicon substrate 1 to form the p ⁺ diffusion layer 7. Thus, ohmic contact can be obtained between the p-type silicon substrate 1, the back surface collecting electrode 5, and the back surface output extraction electrode 6.

  As a second method for forming the light-receiving surface electrode 4, the back surface collecting electrode 5 and the back surface output extraction electrode 6, the aluminum electrode paste composition for forming the back surface collecting electrode 5 is first printed, and after drying, the atmosphere After baking at about 750 to 850 ° C. to form the back surface collecting electrode 5, the electrode paste composition of the present invention is printed on the light receiving surface side and the back surface side, and after drying at about 450 to 650 ° C. in the atmosphere. There is a method in which the light receiving surface electrode 4 and the back surface output extraction electrode 6 are formed by baking.

This method is effective in the following cases, for example. That is, when the aluminum electrode paste forming the back surface collecting electrode 5 is fired, at a firing temperature of 650 ° C. or less, depending on the composition of the aluminum paste, the aluminum particles may be sintered and diffused into the p-type silicon substrate 1. In some cases, the amount of the p ⁺ diffusion layer cannot be sufficiently formed due to an insufficient amount. In this state, a sufficient ohmic contact cannot be formed between the p-type silicon substrate 1 on the back surface, the back surface collecting electrode 5 and the back surface output extraction electrode 6, and the power generation performance as a solar cell element may be reduced. Therefore, after forming the back surface collecting electrode 5 at an optimum firing temperature (for example, 750 to 850 ° C.) for the aluminum electrode paste composition, the electrode paste composition of the present invention is printed and dried at a relatively low temperature (450 It is preferable to form the light receiving surface electrode 4 and the back surface output extraction electrode 6 by baking at ˜650 ° C.).

  FIG. 4 is a schematic plan view of a back-side electrode structure common to a so-called back contact solar cell element according to another embodiment of the present invention, and FIG. 4 shows an outline of a solar cell element which is a back contact solar cell element according to another embodiment. The perspective view which shows a structure is shown in FIG.5, FIG6 and FIG.7, respectively. 5, 6, and 7 are perspective views taken along a section AA in FIG. 4.

In the solar cell element having the structure shown in the perspective view of FIG. 5, the p-type silicon substrate 1 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, an n ⁺ diffusion layer 2 by n-type diffusion treatment is formed on the light receiving surface side, and an antireflection film (not shown) is formed on the n ⁺ diffusion layer 2. These are manufactured by the same process as a conventional crystalline Si type solar battery cell.

Next, the electrode paste composition is filled in the previously formed through hole by a printing method or an inkjet method, and the electrode paste composition of the present invention is similarly printed in a grid on the light receiving surface side, A composition layer for forming the through-hole electrode 9 and the light receiving surface collecting electrode 8 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, an n ⁺ diffusion layer 2 and a p ⁺ diffusion layer 7 for preventing carrier recombination are formed on the back surface side. Here, boron (B) or aluminum (Al) is used as an impurity element for forming the p ⁺ diffusion layer 7. The p ⁺ diffusion layer 7 may be formed by, for example, performing a thermal diffusion process using B as a diffusion source in a cell manufacturing process before forming the antireflection film, or when using Al. May be formed by printing and baking an aluminum paste on the opposite surface side in the printing step.

On the back side, as shown in the plan view of FIG. 4, the back electrode 10 and 11 are formed by printing the electrode paste composition on the n ⁺ diffusion layer 2 and the p ⁺ diffusion layer 7 in stripes, respectively. Is done. Here, when the p ⁺ diffusion layer 7 is formed using an aluminum paste, the back electrode may be formed using the electrode paste composition only on the n ⁺ diffusion layer 2 side.

Thereafter, it is dried and fired at about 450 to 850 ° C. in the atmosphere, whereby the light receiving surface collecting electrode 8, the through-hole electrode 9, and the back surface electrodes 10 and 11 are formed. As described above, when an aluminum electrode is used for one of the back electrodes, the aluminum paste is first printed and fired from the viewpoint of aluminum sinterability and ohmic contact between the back electrode and the p ⁺ diffusion layer 7. One of the back electrodes may be formed by, and then the electrode paste composition for electrode, the through-hole electrode 9 and the other of the back electrodes may be formed by printing, filling, and baking the electrode paste composition. .

  Further, the solar cell element having the structure shown in the perspective view of FIG. 6 can be manufactured in the same manner as the solar cell element having the structure shown in the perspective view of FIG. 5 except that the light receiving surface collecting electrode is not formed. it can. That is, in the solar cell element having the structure shown in the perspective view of FIG. 6, the electrode paste composition can be used for the through-hole electrode 9 and the back surface electrodes 10 and 11.

  Further, the solar cell element having the structure shown in the perspective view of FIG. 7 has the structure shown in the perspective view of FIG. 5 except that an n-type silicon substrate is used as the base substrate and no through hole is formed. It can be manufactured in the same manner as the solar cell element. That is, in the solar cell element having the structure shown in the perspective view of FIG. 7, the electrode paste composition can be used for the back electrodes 10 and 11.

<Solar cell>
The solar cell of the present invention includes at least one of the solar cell elements, and is configured by arranging tab wires on the electrodes of the solar cell element. If necessary, the solar cell may be configured by connecting a plurality of solar cell elements via tab wires and further sealing with a sealing material.
The tab wire and the sealing material are not particularly limited, and can be appropriately selected from those usually used in the art.

<Paste composition for electrodes>
The electrode paste composition includes at least one kind of copper-containing particles, at least one kind of glass particles, at least one kind of solvent, and at least one kind of resin, and if necessary, tin-containing particles, It further comprises silver particles and the like.
With such a configuration, oxidation of copper during firing in the atmosphere is suppressed, and an electrode with low resistivity can be formed. Furthermore, formation of a reactant phase between the substrate containing copper and silicon is suppressed, and a good ohmic contact can be formed between the formed electrode and the silicon substrate.

(Phosphorus-containing copper alloy particles)
The electrode paste composition preferably includes at least one phosphorus-containing copper alloy particle as the copper-containing particle. 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 phosphorus-containing copper alloy particles in the electrode paste composition of the present invention, the reductivity of phosphorus to copper oxide is utilized. In addition, an electrode having excellent oxidation resistance and low volume 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.

  As the phosphorus content contained in the phosphorus-containing copper alloy in the present invention, the phosphorus content is preferably 6% by mass or more and 8% by mass or less from the viewpoint of oxidation resistance and low resistivity, and 6.3% by mass. The content is more preferably 7.8% by mass or less and more preferably 6.5% 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 particles is excellent. Moreover, the more outstanding oxidation resistance can be achieved because it is 6 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 Ag, Mn, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Examples include Mo, Ti, Co, Ni, and Au.
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%.

  In the present invention, the phosphorus-containing copper alloy particles may be used singly or in combination of two or more.

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 with the phosphorus containing copper alloy particle | grains in an electrode or the tin containing particle | grains mentioned later becomes large because it is 10 micrometers or less, and a resistivity falls more effectively. The particle size of the phosphorus-containing copper alloy particles is measured by a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300 type).
Further, the shape of the phosphorus-containing copper alloy particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity. Therefore, it is preferably substantially spherical, flat, or plate-shaped.

  The content rate of the phosphorus-containing copper alloy particles in the electrode paste composition is not particularly limited. From the viewpoint of low resistivity, it is preferably 20% by mass to 85% by mass in the electrode paste composition, more preferably 25% by mass to 80% by mass, and more preferably 30% by mass to 75% by mass. More preferably, it is as follows.

The phosphorus-containing copper alloy can be produced by a commonly used method. Also, the phosphorus-containing copper alloy particles can be prepared using a normal method of preparing metal powder using a phosphorus-containing copper alloy prepared so as to have a desired phosphorus content, for example, a water atomization method Can be produced by a conventional method. For details of the water atomization method, the description of Metal Handbook (Maruzen Co., Ltd. Publishing Division) can be referred to.
Specifically, the desired phosphorus-containing copper alloy particles can be produced by dissolving the phosphorus-containing copper alloy, pulverizing this by nozzle spraying, and drying and classifying the obtained powder. Moreover, the phosphorus containing copper alloy particle | grains which have a desired particle diameter can be manufactured by selecting classification conditions suitably.

(Tin-containing particles)
The electrode paste composition preferably further contains at least one tin-containing particle. By including tin-containing particles in addition to copper-containing particles (preferably phosphorus-containing copper alloy particles), an electrode having a low resistivity can be formed in the firing treatment.
This can be considered as follows, for example. When forming an electrode using the paste composition for an electrode containing phosphorus-containing copper alloy particles and tin-containing particles, the phosphorus-containing copper alloy particles and the tin-containing particles react with each other during the firing treatment, and Cu-Sn An electrode composed of an alloy phase and a Sn—PO glass phase is formed. Here, it is considered that the Cu—Sn alloy phase forms a dense bulk body in the electrode and can function as a conductive layer to form an electrode with low resistivity.
Note that the term “dense bulk body” as used herein means that the massive Cu—Sn alloy phases are in close contact with each other to form a three-dimensional continuous structure.

In addition, when an electrode is formed on a substrate containing silicon (hereinafter also simply referred to as “silicon substrate”) using an electrode paste composition containing phosphorus-containing copper alloy particles and tin-containing particles, the adhesion to the silicon substrate is high. An electrode can be formed, and a good ohmic contact between the electrode and the silicon substrate can be achieved.
This can be considered as follows, for example. The phosphorus-containing copper alloy particles and the tin-containing particles react with each other in the firing step to form an electrode composed of a Cu—Sn alloy phase and a Sn—P—O glass phase. Since the Cu—Sn alloy phase is a dense bulk body, this Sn—PO glass phase is formed between the Cu—Sn alloy phase and the silicon substrate. Thereby, it can be considered that the adhesion of the Cu—Sn alloy phase to the silicon substrate is improved. When the Sn—PO glass phase functions as a barrier layer for preventing mutual diffusion between copper and silicon, a good ohmic contact between the electrode formed by baking and the silicon substrate can be achieved. Can think. In other words, the formation of a reaction phase (Cu ₃ Si) formed when an electrode containing copper and silicon are directly contacted and heated is suppressed, and the silicon substrate and the silicon substrate are not degraded without deteriorating semiconductor performance (for example, pn junction characteristics). It is considered that a good ohmic contact can be expressed while maintaining the adhesiveness.

  Such an effect is generally manifested when an electrode is formed using an electrode paste composition containing phosphorus-containing copper alloy particles and tin-containing particles on a substrate containing silicon. There are no particular restrictions on the type of substrate that contains.

  That is, in a preferred embodiment of the present invention, by combining the phosphorus-containing copper alloy particles and the tin-containing particles in the electrode paste composition, first, the reducibility of the phosphorus atoms in the phosphorus-containing copper alloy particles to the copper oxide is utilized. An electrode having excellent oxidation resistance and low volume resistivity is formed. Next, a reaction between the phosphorus-containing copper alloy particles and the tin-containing particles forms a conductive layer composed of a Cu—Sn alloy phase and a Sn—P—O glass phase while keeping the volume resistivity low. And, for example, the Sn—P—O glass phase functions as a barrier layer for preventing the mutual diffusion of copper and silicon, thereby suppressing the formation of a reactant phase between the electrode and the silicon substrate. It can be considered that two characteristic mechanisms that a good ohmic contact with the electrode is formed can be realized simultaneously by the baking treatment.

The tin-containing particles are not particularly limited as long as they contain tin. Among them, at least one selected from tin particles and tin alloy particles is preferable, and at least one selected from tin alloy particles having a tin content of 1% by mass or more is preferable.
The purity of tin in the tin particles is not particularly limited. For example, the purity of the tin particles can be 95% by mass or more, preferably 97% by mass or more, and preferably 99% by mass or more.

  The type of alloy is not particularly limited as long as the tin alloy particles are alloy particles containing tin. Among these, from the viewpoint of the melting point of the tin alloy particles and the reactivity with the phosphorus-containing copper alloy particles, the tin alloy particles preferably have a tin content of 1% by mass or more, and the tin content is 3% by mass. The tin alloy particles are more preferable, and tin alloy particles having a tin content of 5% by mass or more are more preferable.

  Examples of the tin alloy particles include Sn-Ag alloys, Sn-Cu alloys, Sn-Ag-Cu alloys, Sn-Ag-Sb alloys, Sn-Ag-Sb-Zn alloys, Sn-Ag- Cu-Zn alloy, Sn-Ag-Cu-Sb alloy, Sn-Ag-Bi alloy, Sn-Bi alloy, Sn-Ag-Cu-Bi alloy, Sn-Ag-In-Bi alloy, Sn—Sb alloy, Sn—Bi—Cu alloy, Sn—Bi—Cu—Zn alloy, Sn—Bi—Zn alloy, Sn—Bi—Sb—Zn alloy, Sn—Zn alloy, Sn— In-based alloys, Sn-Zn-In-based alloys, Sn-Pb-based alloys, and the like can be given.

Among the tin alloy particles, in particular, Sn-3.5Ag, Sn-0.7Cu, Sn-3.2Ag-0.5Cu, Sn-4Ag-0.5Cu, Sn-2.5Ag-0.8Cu-0 .5Sb, Sn-2Ag-7.5Bi, Sn-3Ag-5Bi, Sn-58Bi, Sn-3.5Ag-3In-0.5Bi, Sn-3Bi-8Zn, Sn-9Zn, Sn-52In, Sn-40Pb Such tin alloy particles have the same or lower melting point as Sn (232 ° C.). Therefore, these tin alloy particles can be suitably used in that they can melt at the initial stage of firing to cover the surface of the phosphorus-containing copper alloy particles and react uniformly with the phosphorus-containing copper alloy particles. . For example, in the case of Sn-AX-BY-CZ, the notation in the tin alloy particle includes A mass% of element X, B mass% of element Y, and C mass% of element Z in the tin alloy particle. Indicates that
In the present invention, these tin-containing particles may be used alone or in combination of two or more.

The tin-containing particles may further contain other atoms that are inevitably mixed. Examples of other atoms inevitably mixed include Ag, Mn, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Al, and Zr. , W, Mo, Ti, Co, Ni, Au, and the like.
Moreover, the content rate of the other atom contained in the said tin containing particle | grain can be 3 mass% or less in the said tin containing particle | grain, for example, 1 mass from the viewpoint of melting | fusing point and the reactivity with phosphorus containing copper alloy particle | grains. % Or less is preferable.

Although there is no restriction | limiting in particular as a particle diameter of the said tin content particle | grains, It is 0.5 micrometer-20 micrometers as a particle diameter (henceforth "D50%" may be abbreviated as "D50%") in case the accumulated weight is 50%. Is preferably 1 μm to 15 μm, more preferably 5 μm to 15 μm. When the thickness is 0.5 μm or more, the oxidation resistance of the tin-containing particles themselves is improved. Moreover, the contact area with the phosphorus containing copper alloy particle in an electrode becomes large because it is 20 micrometers or less, and reaction with phosphorus containing copper alloy particle advances effectively.
The shape of the tin-containing particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity. It is preferably substantially spherical, flat, or plate-shaped.

Moreover, the content rate of the tin-containing particles in the case where the electrode paste composition contains tin-containing particles is not particularly limited. Especially, it is preferable that the content rate of the tin containing particle when the total content rate of the said phosphorus containing copper alloy particle and the said tin containing particle | grain is 100 mass% is 5 mass% or more and 70 mass% or less, 7 mass % To 65% by mass, more preferably 9% to 60% by mass.
By making the content rate of a tin containing particle | grain 5 mass% or more, reaction with phosphorus containing copper alloy particle | grains can be produced more uniformly. Moreover, by setting the tin-containing particles to 70% by mass or less, a sufficient volume of the Cu—Sn alloy phase can be formed, and the volume resistivity of the electrode is further reduced.

(Glass particles)
The electrode paste composition includes at least one kind of glass particles. When the electrode paste composition contains glass particles, the adhesion between the electrode portion and the substrate is improved during firing. Also. In particular, in forming the electrode on the light-receiving surface side of the solar cell, the silicon nitride film as the antireflection film is removed by so-called fire-through during firing, and an ohmic contact between the electrode and the silicon substrate is formed.

  The glass particles are glass particles containing glass having a glass softening point of 650 ° C. or lower and a crystallization start temperature exceeding 650 ° C. from the viewpoint of adhesion to the substrate and reduction in resistivity of the electrode. preferable. 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.

  When the electrode paste composition is used as an electrode on the solar cell light-receiving surface side, the glass particles soften and melt at the electrode formation temperature, oxidize the contacted silicon nitride film, and incorporate the oxidized silicon dioxide. As long as the antireflection film can be removed, glass particles usually used in the technical field can be used without particular limitation.

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.

  In addition, when the electrode paste composition is used as an electrode other than the electrode on the light-receiving surface side of the solar cell, for example, a back surface extraction electrode, a through-hole electrode or a back electrode in a back contact solar cell, the glass softening point is 650 ° C. or lower. Any glass particles containing glass having a crystallization start temperature exceeding 650 ° C. can be used without including components necessary for fire-through such as lead.

As the glass component constituting the glass particles used in the electrode paste composition, silicon dioxide _(SiO 2), phosphorus oxide _{(P 2 O} 5), aluminum oxide _{(Al 2 O} 3), boron oxide _(B 2 _{O 3} ), Vanadium oxide (V ₂ O ₅ ), potassium oxide (K ₂ O), bismuth oxide (Bi ₂ O ₃ ), 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) Niobium oxide _{(Nb 2 O} 5), tantalum oxide _{(Ta 2 O} 5), yttrium oxide _{(Y 2 O} 3), titanium oxide _(TiO 2), germanium oxide _(GeO 2), tellurium oxide _(TeO 2), lutetium oxide (Lu ₂ O ₃ ), antimony oxide (Sb ₂ O ₃ ), copper oxide (CuO), iron oxide (FeO), silver oxide (AgO), and manganese oxide (MnO).

Among these, it is preferable to use at least one selected from SiO ₂ , P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ , V ₂ O ₅ , Bi ₂ O ₃ , ZnO, and PbO. Specifically, as a glass _component, include those containing _{SiO 2, PbO, B 2 O} 3, Bi 2 O 3 and _Al 2 _{O 3.} In the case of such glass particles, the softening point is effectively reduced, and the wettability with the phosphorus-containing copper alloy particles and the silver particles added as necessary is improved. Sintering progresses, and an electrode with low resistivity can be formed.

On the other hand, from the viewpoint of low contact resistivity, glass particles containing phosphorous pentoxide (phosphate glass, P ₂ O ₅ glass particles) are preferable. In addition to diphosphorus pentoxide, divanadium pentoxide is used. and more preferably further comprises glass particles _{(P 2 O 5 -V 2 O} 5 -based glass particles). 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 diphosphorus pentoxide-divanadium pentoxide glass particles (P ₂ O ₅ —V ₂ O ₅ glass particles) are used, the content of divanadium pentoxide is 1% by mass or more in the total mass of the glass. It is preferable that it is 1 mass%-70 mass%.

The particle diameter of the glass particles is not particularly limited, but the particle diameter (D50%) when the integrated weight is 50% is preferably 0.5 μm or more and 10 μm or less, and 0.8 μm or more and 8 μm or less. It is more preferable that When the thickness is 0.5 μm or more, workability at the time of preparing the electrode paste composition is improved. Moreover, when it is 10 μm or less, it can be uniformly dispersed in the electrode paste composition, fire-through can be efficiently generated in the firing step, and adhesion to the silicon substrate is also improved.
Further, the shape of the glass particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity. A spherical shape, a flat shape, or a plate shape is preferable.

  The content of the glass particles is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 8% by mass, based on the total mass of the electrode paste composition. More preferably, the content is from 8% by mass to 8% by mass. By including glass particles in such a content ratio, oxidation resistance, lower electrode resistivity, and lower contact resistance can be achieved more effectively, and the phosphorus-containing copper alloy particles and the tin-containing particles The reaction of can be promoted.

(Solvent and resin)
The electrode paste composition includes 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 can be adjusted to the required liquid physical property according to the application | coating method at the time of providing to a silicon substrate etc.

  There is no restriction | limiting in particular as said solvent. For example, hydrocarbon solvents such as hexane, cyclohexane and toluene; chlorinated hydrocarbon solvents such as dichloroethylene, dichloroethane and dichlorobenzene; cyclics such as tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, 1,3-dioxolane and trioxane Ether solvents; amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide; sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone and cyclohexanone; ethanol; Alcohol compounds such as 2-propanol, 1-butanol, diacetone alcohol; 2,2,4-trimethyl-1,3-pentanediol monoacetate, 2,2,4- Limethyl-1,3-pentanediol monopropiolate, 2,2,4-trimethyl-1,3-pentanediol monobutyrate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, Ester solvents of polyhydric alcohols such as 2,2,4-triethyl-1,3-pentanediol monoacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate; butyl cellosolve, diethylene glycol monobutyl ether, diethylene glycol diethyl ether Ether solvents of dihydric alcohols: α-terpinene, α-terpineol, myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, osimene, ferrand And terpene solvents such as len and mixtures thereof.

The solvent is selected from polyhydric alcohol ester solvents, terpene solvents, and polyhydric alcohol ether solvents from the viewpoints of coatability and printability when forming an electrode paste composition on a silicon substrate. It is preferably at least one, more preferably at least one selected from polyhydric alcohol ester solvents and terpene solvents.
Moreover, 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 methylcellulose, ethylcellulose, carboxymethylcellulose, and nitrocellulose; polyvinyl alcohols; polyvinylpyrrolidones; 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 is preferably at least one selected from cellulosic resins and acrylic resins from the viewpoint of disappearance during firing.
In the present invention, the resins may be used alone or in combination of two or more.

The weight average molecular weight of the resin is not particularly limited. Among these, the weight average molecular weight is preferably from 5,000 to 500,000, and more preferably from 10,000 to 300,000. It can suppress that the viscosity of the paste composition for electrodes increases that the weight average molecular weight of the said resin is 5000 or more. This may be because, for example, the three-dimensional repulsion when adsorbed to phosphorus-containing copper alloy particles and tin-containing particles is insufficient, and the particles aggregate. On the other hand, when the weight average molecular weight of the resin is 500000 or less, aggregation of the resins in the solvent is suppressed, and increase in the viscosity of the electrode paste composition can be suppressed.
In addition, if the weight average molecular weight of the resin is 500,000 or less, it is suppressed that the resin combustion temperature becomes high, and the resin is not completely burned when the electrode paste composition is fired, and remains as a foreign substance. Is suppressed, and the electrode can be configured to have a lower resistance.

In the electrode paste composition, the content of the solvent and the resin can be appropriately selected according to the desired liquid physical 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.

  Further, in the electrode paste composition, from the viewpoint of oxidation resistance and low resistivity of the electrode, the total content of the phosphorus-containing copper alloy particles and the tin-containing particles is 70% by mass or more and 94% by mass or less, and the glass particles Is preferably 0.1% by mass or more and 10% by mass or less, and the total content of the solvent and the resin is preferably 3% by mass or more and 29.9% by mass or less. The total particle content is 74% by mass or more and 88% by mass or less, the glass particle content is 0.5% by mass or more and 8% by mass or less, and the total content of the solvent and the resin is 7% by mass or more. More preferably, the total content of the phosphorus-containing copper alloy particles and the tin-containing particles is 74 mass% or more and 88 mass% or less, and the glass particle content is 1 mass% or more and 8 mass% or less. The total content of solvent and resin It is more preferably 7% by mass or more to 20% by weight.

(Silver particles)
The electrode paste composition preferably further contains silver particles. By containing silver particles, the oxidation resistance is further improved, and the resistivity as an electrode is further reduced. In addition, when the electrode paste composition includes phosphorus-containing copper alloy particles and tin-containing particles, Ag particles are contained in the Sn—PO system glass phase generated by the reaction between the phosphorus-containing copper alloy particles and the tin-containing particles. By precipitating, the ohmic contact property between the Cu—Sn alloy phase in the electrode layer and the silicon substrate is further improved. Furthermore, the effect that the solder connection property at the time of setting it as a solar cell module improves is also acquired.

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.
Moreover, the content rate of the other atom contained in the said silver particle can be 3 mass% or less in a silver particle, for example, and it is 1 mass% or less from a viewpoint of melting | fusing point and the low resistivity of an electrode. preferable.

The particle diameter of the silver particles 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 is 1 μm or more and 7 μm or less. It is more preferable. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, the contact area of the silver particle, phosphorus containing copper alloy particle | grains, and tin containing particle | grains in an electrode becomes large because it is 10 micrometers or less, and resistivity falls more effectively.
Further, the shape of the silver particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, from the viewpoint of oxidation resistance and low resistivity. A spherical shape, a flat shape, or a plate shape is preferable.

  Moreover, as a content rate of the silver particle in the case where the paste composition for an electrode contains silver particles, the silver particles when the total content rate of the phosphorus-containing copper alloy particles, the tin-containing particles, and the silver particles is 100% by mass Is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less.

  Further, the electrode paste composition includes phosphorus-containing copper alloy particles, tin-containing particles and silver particles, from the viewpoint of oxidation resistance, low resistivity of the electrode, and applicability to a silicon substrate, and includes phosphorus-containing copper alloy particles, The total content of tin-containing particles and silver particles is preferably 70% by mass or more and 94% by mass or less, and more preferably 74% by mass or more and 88% by mass or less. When the total content of the phosphorus-containing copper alloy particles, tin-containing particles, and 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 rate of phosphorus containing copper alloy particle | grains, tin containing particle | grains, and silver particle | grains is 94 mass% or less. .

  Furthermore, when the electrode paste composition contains phosphorus-containing copper alloy particles, tin-containing particles and silver particles, from the viewpoint of oxidation resistance and low resistivity of the electrode, the total of phosphorus-containing copper alloy particles, tin-containing particles and silver particles The content is 70% by mass to 94% by mass, the glass particle content is 0.1% by mass to 10% by mass, and the total content of the solvent and the resin is 3% by mass to 29.9%. The total content of phosphorus-containing copper alloy particles, tin-containing particles and silver particles is preferably 74% by mass or more and 88% by mass or less, and the glass particle content is 0.5% by mass or more. More preferably, the total content of the solvent and the resin is 7% by mass or more and 20% by mass or less, and the total content of the phosphorus-containing copper alloy particles, the tin-containing particles, and the silver particles is 74% by mass. % To 88% by mass of glass particles Content is not more than 8 mass% to 1 mass%, it is more preferable that the total content of the solvent and the resin is 20 mass% or less 7 mass% or more.

(flux)
The electrode paste composition may further include at least one flux. By including the flux, the oxide film formed on the surface of the phosphorus-containing copper alloy particles can be removed, and the reduction reaction of the phosphorus-containing copper alloy particles during firing can be promoted. Further, since the melting of the tin-containing particles during firing proceeds, the reaction with the phosphorus-containing copper alloy particles proceeds, and as a result, the oxidation resistance is further improved and the resistivity of the formed electrode is further decreased. 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 it can remove the oxide film formed on the surface of the phosphorus-containing copper alloy particles and promote the melting of the tin-containing particles. Specifically, for example, fatty acids, boric acid compounds, fluorinated compounds, borofluorinated compounds and the like can be mentioned as preferred fluxes.

More specifically, the flux includes lauric acid, myristic acid, palmitic acid, stearic acid, sorbic acid, stearic acid, propionic acid, boron oxide, potassium borate, sodium borate, lithium borate, potassium borofluoride, borofluoride. Sodium fluoride, lithium borofluoride, acidic potassium fluoride, acidic sodium fluoride, acidic lithium fluoride, potassium fluoride, sodium fluoride, lithium fluoride and the like can be mentioned.
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 phosphorus-containing copper alloy particles.
In the present invention, each of these fluxes may be used alone or in combination of two or more.

  In the case where the electrode paste composition of the present invention contains a flux, the flux content is such that the oxidation resistance of the phosphorus-containing copper alloy particles is effectively expressed and the melting of the tin-containing particles is promoted and the electrode material From the viewpoint of reducing the porosity of the part from which the flux has been removed upon completion of firing, it is preferably 0.1% by mass to 5% by mass in the total mass of the electrode paste composition, and 0.3% by mass to 4%. More preferably, it is more preferably 0.5% by mass to 3.5% by mass, particularly preferably 0.7% by mass to 3% by mass, and 1% by mass to 2.5% by mass. It is very preferable that

(Other ingredients)
In addition to the components described above, the electrode paste composition of the present invention can further contain other components that are usually used in the technical field, if necessary. 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. Produced by dispersing and mixing the phosphorus-containing copper alloy particles, the tin-containing particles, the glass particles, the solvent, the resin, and the silver particles contained as required, using a commonly used dispersion / mixing method. be able to.
The dispersion / mixing method is not particularly limited, and can be appropriately selected and applied from commonly used dispersion / mixing methods.

The electrode paste composition contains phosphorus-containing copper alloy particles, tin-containing particles, glass particles, a solvent and a resin, and has a viscosity at 25 ° C. of 20 Pa · s to 1000 Pa · s from the viewpoint of surface coating properties and moldability. The viscosity is preferably in the range, more preferably in the range of 25 Pa · s to 800 Pa · s, and still more preferably in the range of 30 Pa · s to 600 Pa · s.
If the viscosity is less than 20 Pa · s, sagging may occur when the electrode paste is applied, and the desired shape may not be applied. In addition, when it exceeds 1000 Pa · s, the fluidity is insufficient, and clogging of the printing mask occurs when the application is performed by screen printing, or nozzle clogging occurs when the application is performed by inkjet. Thus, it may be difficult to grant.
The viscosity of the electrode paste composition is measured at 25 ° C. using a Brookfield HBT viscometer.

The electrode paste composition includes phosphorus-containing copper alloy particles, tin-containing particles, glass particles, a solvent and a resin, and preferably has a solid content in the range of 70% by mass to 98% by mass. The concentration is more preferably in the range of 75% by mass to 96% by mass, and further preferably in the range of 80% by mass to 95% by mass.
If the solid content concentration is less than 70% by mass, the reaction or sintering of the phosphorus-containing copper alloy and tin-containing particles may be insufficient and the resistivity may increase. Moreover, when it exceeds 98 mass%, the fluidity | liquidity of an electrode paste composition falls or a dispersibility falls, and when a paste composition for electrodes is provided, a nonuniformity may generate | occur | produce.
In addition, solid content concentration of the paste composition for electrodes means the residue which remove | excluded the volatile component from the component which comprises the paste composition for electrodes. Specifically, the measurement is performed on the basis of the residue after the electrode paste composition is left in an environment of 25 ° C. and 1 atm for 10 hours to remove volatile components.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples, and “parts” and “%” are based on mass unless otherwise specified. .

<Example 1>
(A) Preparation of electrode paste composition Phosphorus-containing copper alloy particles containing 7% by mass of phosphorus were prepared by a conventional method, dissolved and powdered by a 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 7% by mass of phosphorus. The phosphorus-containing copper alloy particles had a particle size (D50%) of 5.0 μm and a substantially spherical shape.

3 parts of silicon dioxide (SiO ₂ ), 60 parts of lead oxide (PbO), 18 parts of boron oxide (B ₂ O ₃ ), 5 parts of bismuth oxide (Bi ₂ O ₃ ), 5 parts of aluminum oxide (Al ₂ O ₃ ), A glass composed of 9 parts of zinc oxide (ZnO) (hereinafter sometimes abbreviated as “G01”) was prepared. The obtained glass G01 had a softening point of 420 ° C. and a crystallization temperature of over 650 ° C.
By using the obtained glass G01, glass G01 particles having a particle diameter (D50%) of 2.5 μm were obtained. The shape was substantially spherical.

39.9 parts of the phosphorus-containing copper alloy particles obtained above, 41.5 parts of tin particles (Sn; particle diameter (D50%) 10.0 μm; purity 99.9%), and glass G01 particles 4. 1 part, 14.1 parts of terpineol (Ter) and 0.4 parts of ethyl cellulose (EC) were mixed and stirred in an agate mortar for 20 minutes to prepare an electrode paste composition 1.
The viscosity of the obtained electrode paste composition measured at 25 ° C. using a Brookfield HBT viscometer (manufactured by Tokyo Keiki Co., Ltd.) was 35.3 Pa · s.
The obtained electrode paste composition was allowed to stand in an environment of 25 ° C. and 1 atm for 10 hours to remove volatile components, and the solid content concentration was calculated to be 85.9% by mass.

(B) Fabrication of element A p-type semiconductor substrate having a film thickness of 190 μm having an n ⁺ diffusion layer, a texture, and an antireflection film (silicon nitride film) formed on the light receiving surface was prepared and cut into a size of 125 mm × 125 mm. 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 1.5 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, using a tunnel furnace (manufactured by Noritake Co., Ltd., one-row transport W / B tunnel furnace), a heat treatment (firing) is performed at a firing maximum temperature of 800 ° C. and a holding time of 10 seconds in an air atmosphere to form a desired electrode. A device was fabricated.
When the volume resistivity of the formed electrode was measured by a four-probe, four-terminal method using a Loresta-EP MCP-T360 type resistivity meter manufactured by Mitsubishi Chemical Corporation, it was 1 × 10 ⁻⁴ Ω · cm or less. Met.

DESCRIPTION OF SYMBOLS 1 p-type silicon substrate 2 n ⁺ Diffusion layer 3 Antireflection film 4 Light-receiving surface collection electrode and output extraction electrode 5 Back surface collection electrode 6 Back surface output extraction electrode 7 p ⁺ Diffusion layer 8 Light-receiving surface collection electrode 9 Through Hall electrode 10 Back surface electrode 11 Back surface electrode 12 n-type silicon substrate

Claims (16)

A substrate comprising silicon and an electrode disposed on the substrate;
The electrode is a fired product of an electrode paste composition containing copper-containing particles, glass particles, a solvent, and a resin, and has a volume resistivity of 1 × 10 ⁻⁴ Ω · cm or less.   The element according to claim 1, wherein the copper-containing particles are phosphorus-containing copper alloy particles.   The element according to claim 2, wherein the phosphorus content of the phosphorus-containing copper alloy particles is 6% by mass or more and 8% by mass or less.   The element according to claim 1, wherein the electrode paste composition further includes tin-containing particles.   The element according to claim 4, wherein the tin-containing particles are at least one selected from tin particles and tin alloy particles having a tin content of 1% by mass or more.   The element according to any one of claims 1 to 5, wherein the glass particles have a glass softening point of 650 ° C or lower and a crystallization start temperature exceeding 650 ° C.   The content rate of the said tin content particle | grains when the total content rate of the said phosphorus content copper alloy particle and the said tin content particle is 100 mass% is 5 mass% or more and 70 mass% or less. The device according to any one of the above items.   The device according to claim 1, wherein the electrode paste composition further includes silver particles.   The electrode paste composition has a silver particle content of 0.1% by mass or more and 10% by mass when the total content of the phosphorus-containing copper alloy particles, the tin-containing particles and the silver particles is 100% by mass. The element according to claim 8, which is not more than%.   The electrode paste composition has a total content of the phosphorus-containing copper alloy particles, tin-containing particles and silver particles of 70% by mass to 94% by mass, and the glass particle content of 0.1% by mass. The element according to claim 8 or 9, wherein the content is 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 element according to any one of claims 4 to 10, wherein the electrode includes a Cu-Sn alloy phase and a Sn-PO glass phase.   The device according to claim 11, wherein the Sn—PO glass phase is disposed between the Cu—Sn alloy phase and the silicon-containing substrate.   It is a solar cell element, The element of any one of Claims 1-12.   A solar cell comprising the element according to claim 13 and a tab wire disposed on an electrode of the element.   An electrode paste composition containing phosphorus-containing copper alloy particles, tin-containing particles, glass particles, a solvent and a resin, and having a viscosity at 25 ° C. of 80 Pa · s to 1000 Pa · s.   An electrode paste composition containing phosphorus-containing copper alloy particles, tin-containing particles, glass particles, a solvent, and a resin, and having a solid content concentration in the range of 70% by mass to 98% by mass.