JP5879793B2 - Device manufacturing method and solar cell manufacturing method - Google Patents

Description

The present invention relates to a device manufacturing method and a solar cell manufacturing method .

  In general, a silicon-based 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. give.

  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

  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.

  An object of the present invention is to provide an element in which a low resistivity electrode formed on a substrate containing silicon and a tab line are connected with a low contact resistance, and a solar cell formed using the element. .

Specific means for solving the above problems are as follows.
<1> A substrate containing silicon, an electrode which is disposed on the substrate and is a fired product of an electrode paste composition containing phosphorus-containing copper alloy particles, glass particles, a solvent and a resin, and electrically on the electrode An element having a connected tab wire and having a peel adhesive strength between the electrode and the tab wire of 0.2 N / mm to 2.0 N / mm.

<2> The element according to <1>, wherein the phosphorus content of the phosphorus-containing copper alloy particles is 6% by mass or more and 8% by mass or less.

<3> The element according to <1> or <2>, wherein the electrode paste composition further includes tin-containing particles.

<4> The element according to <3>, 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.

<5> The element according to any one of <1> to <4>, wherein the glass particles have a glass softening point of 600 ° C. or lower and a crystallization start temperature exceeding 600 ° C.

<6> The electrode paste composition has a content of the tin-containing particles of 5% by mass to 70% by mass when the total content of the phosphorus-containing copper alloy particles and the tin-containing particles is 100% by mass. The device according to any one of <3> to <5>, which is the following.

<7> The element according to any one of <1> to <6>, wherein the electrode paste composition further includes silver particles.

<8> The electrode paste composition has a silver particle content of 0.1% 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 <7>, which is 10% by mass or less.

<9> 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 a glass particle content of 0.1. The element according to claim 7 or 8, wherein the content is from 10% by mass to 10% by mass and the total content of the solvent and the resin is from 3% by mass to 29.9% by mass.

<10> The element according to any one of <1> to <9>, wherein the silicon-containing substrate has a pn junction and is used for a solar cell.

<11> A solar cell provided with the element used for the solar cell as described in said <10>, and the sealing material which seals the said element.

  According to the present invention, it is possible to provide an element in which a low resistivity electrode formed on a silicon-containing substrate and a tab wire are connected with a low contact resistance, and a solar cell formed using the element. .

It is a schematic sectional drawing of the solar cell concerning this invention. It is a schematic plan view which shows the light-receiving surface side of the solar cell concerning this invention. It is a schematic plan view which shows the back surface side of the solar cell concerning this invention. (A) It is a schematic perspective view which shows AA cross-section structure of the back contact type solar cell concerning this invention. (B) It is a schematic plan view which shows the back surface side electrode structure of the back contact type solar cell 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 includes a substrate containing silicon, an electrode which is disposed on the substrate and is a fired product of a paste composition for an electrode containing phosphorus-containing copper alloy particles, glass particles, a solvent and a resin, and the electrode. A tab wire electrically connected, and a peel adhesion strength between the electrode and the tab wire is 0.2 N / mm to 2.0 N / mm.
The electrode is a fired product of the electrode paste composition, and the peel adhesive strength between the electrode and the tab wire is within a predetermined range, whereby the electrode having a low resistivity and the tab wire are connected with a low contact resistance.

[substrate]
The substrate is not particularly limited as long as it contains silicon (silicon). Among these, a silicon substrate containing a p-type or n-type impurity is preferable, and a silicon substrate having a pn junction and used for a solar cell is more preferable, and is reflected on a surface on which an electrode is formed. It is more preferable for a solar cell provided with a prevention film.

[Paste composition for electrode]
The electrode paste composition includes phosphorus-containing copper alloy particles, at least one kind of glass particles, at least one kind of solvent, and at least one kind of resin. With such a configuration, oxidation of copper during firing is suppressed, and an electrode with low resistivity can be formed.

(Phosphorus-containing copper alloy particles)
The electrode paste composition includes at least one phosphorus-containing copper alloy particle.
The phosphorus content contained in the phosphorus-containing copper alloy is not particularly limited. From the viewpoint of oxidation resistance and low resistivity, the phosphorus content is preferably 6% by mass or more and 8% by mass or less, more preferably 6.3% by mass or more and 7.8% by mass or less. More preferably, it is 5 mass% or more and 7.5 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 oxidation resistance can be achieved because it is 6 mass% or more.
Furthermore, the phosphorus content contained in the phosphorus-containing copper alloy is 6% by mass or more, so that when the electrode is formed, the adhesiveness with the tab wire is improved, and the peel adhesion strength between the electrode and the tab wire is within a desired range. It can be. This can be considered, for example, because the formation of an oxide film on the electrode surface can be suppressed.

  As a phosphorus-containing copper alloy, a brazing material called phosphorus copper brazing (phosphorus concentration: usually about 7% by mass or less) is known. Phosphor copper brazing is also used as a bonding agent between copper and copper. By using phosphorus-containing copper alloy particles in the electrode paste composition of the present invention, it is possible to form an electrode having excellent oxidation resistance and low resistivity by utilizing the reducibility of phosphorus to copper oxide. 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-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%.

  The phosphorus-containing copper alloy particles may be used alone 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 weight accumulated from the small diameter side is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.4 μm. It is preferably 10 μm to 10 μm, and 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 phosphorus containing copper alloy particles in an electrode 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).

  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.

  As content rate of the said phosphorus containing copper alloy particle contained in the said paste composition for electrodes, 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 mass%-94 From the viewpoint of oxidation resistance and low resistivity, it is preferably 72% by mass to 90% by mass, and more preferably 74% by mass to 88% by mass.

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.

(Glass particles)
The electrode paste composition includes at least one glass particle. When the electrode paste composition contains glass particles, the adhesion between the electrode portion and the substrate is improved during firing. Further , at the electrode formation temperature, the silicon nitride film which is an antireflection film is removed by so-called fire-through, 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.
The glass particles are preferably glass particles containing glass having a glass softening point of 600 ° C. or lower and a crystallization start temperature exceeding 600 ° C. 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.

In general, the glass particles contained in the electrode paste composition are preferably composed of glass containing lead because silicon dioxide can be taken up efficiently. 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.

Examples of the glass component used in the electrode paste composition include silicon dioxide (SiO ₂ ), phosphorus oxide (P ₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ), boron oxide (B ₂ O ₃ ), and oxidation. Vanadium (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 (WO3), molybdenum oxide _(MoO 3), lanthanum oxide _{(La 2 O} 3), niobium oxide Nb2 O5), 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, SiO _{2, PbO,} may preferably be mentioned those containing _{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 lowered and the wettability with phosphorus-containing copper alloy particles and 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%.

  There is no restriction | limiting in particular as a particle diameter of the said glass particle. For example, the particle diameter (hereinafter sometimes abbreviated as “D50%”) when the weight accumulated from the small particle diameter side is 50% is preferably 0.5 μm or more and 10 μm or less, and 0.8 μm or more and 8 μm. The following is more preferable. When the thickness is 0.5 μm or more, workability at the time of preparing the electrode paste composition is improved. Moreover, by being 10 micrometers or less. It can be uniformly dispersed in the electrode paste composition, fire-through can be efficiently generated in the firing step, and adhesion with a substrate containing silicon is also improved.

  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, it is 7 mass% to 7 mass%. By including glass particles in such a range of content, oxidation resistance, lower electrode resistivity, and lower contact resistance can be achieved more effectively.

(Solvent and resin)
The electrode paste composition includes at least one solvent and at least one resin. Thereby, the liquid physical properties (for example, viscosity, surface tension, and aspect ratio of the electrode after firing) of the electrode paste composition of the present invention are required for the liquid physical properties depending on the application method when applying to the silicon substrate. Can be adjusted.

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- Rimechiru 1,3-pentanediol mono-propiolactone ne over preparative, 2,2,4-trimethyl-1,3-pentanediol mono-butyrate, 2,2,4-trimethyl-1,3-pentanediol mono isobutyrate Ester solvents of polyhydric alcohols such as rate, 2,2,4-triethyl-1,3-pentanediol monoacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate; polyhydric alcohols such as butyl cellosolve and diethylene glycol diethyl ether Ether solvents such as α-terpinene, α-terpineol, myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, oximene, ferrandrene, and mixtures thereof Compound may be mentioned.

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.
The solvent may be used alone or in combination of two or more.

  As the resin, any resin that is usually used in the technical field can be used without particular limitation as long as it is a resin that can be thermally decomposed in the firing step. 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 a cellulose-based resin and an acrylic resin, and more preferably at least one selected from a cellulose-based resin, from the viewpoint of disappearance during firing.
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. When the weight average molecular weight of the resin is 5000 or more, an increase in the viscosity of the electrode paste composition can be suppressed. This can be considered to be because, for example, a phenomenon in which the three-dimensional repulsive action when adsorbed on phosphorus-containing copper alloy particles is insufficient and the particles are aggregated is suppressed. On the other hand, when the weight average molecular weight of the resin is 500,000 or less, the phenomenon that the resins are aggregated in the solvent and as a result, the viscosity of the electrode paste composition increases is suppressed. In addition, if the weight average molecular weight of the resin is suppressed to an appropriate size, the resin combustion temperature is prevented from increasing, and the resin is not completely burned when the electrode paste composition is baked, and remains as a foreign substance. Thus, the resistance of the electrode can be reduced.

In the electrode paste composition, the contents 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 shape can be more easily formed. it can.

(Tin-containing particles)
The electrode paste composition preferably includes at least one tin-containing particle. By including tin-containing particles in addition to phosphorus-containing copper alloy particles, an electrode having a low resistivity can be formed in the firing step described later.
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. 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.

When an electrode is formed on a silicon-containing substrate (hereinafter also simply referred to as “silicon substrate”) using an electrode paste composition containing tin-containing particles, an electrode having high adhesion to the silicon substrate may be formed. In addition, 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 the electrode paste composition on a substrate containing silicon, and the type of substrate containing silicon is particularly limited. It is not a thing. As a board | substrate containing silicon, the silicon substrate used for manufacture of the silicon substrate for solar cell formation, semiconductor devices other than a solar cell, etc. can be mentioned, for example.

  That is, by combining the phosphorus-containing copper alloy particles and the tin-containing particles in the electrode paste composition, first utilizing the reducibility of the phosphorus atoms in the phosphorus-containing copper alloy particles to the copper oxide, excellent oxidation resistance, An electrode having a 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 of forming a good ohmic contact with the electrode can be realized simultaneously in the firing step.

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, it is preferably tin alloy particles having a tin content of 1% by mass or more, and the tin content is 3% by mass. The tin alloy particles are more preferably the above, more preferably tin alloy particles having a tin content of 5% by mass or more, and tin alloy particles having a tin content of 10% by mass or more. It is particularly preferred.

  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
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.

The particle diameter of the tin-containing particles is not particularly limited, but the particle diameter when the weight accumulated from the small particle diameter side is 50% (hereinafter sometimes abbreviated as “D50%”) is 0.5 μm. It is preferably ˜20 μm, more preferably 1 μm to 15 μm, and further 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.

Further, the content of tin-containing particles in the electrode paste composition of the present invention 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 weight, more preferably 9% to 60% by weight, and more preferably 9% to 55% by weight from the viewpoint of the peel adhesion strength between the electrode and the tab wire. It is particularly preferred.
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.

(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. Further, the Ag particles are precipitated in the Sn—P—O-based glass phase generated by the reaction between the phosphorus-containing copper alloy particles and the tin-containing particles, so that the Cu—Sn alloy phase and silicon in the electrode layer are deposited. The ohmic contact property between the substrates 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 weight integrated from the small particle diameter side is 50% is preferably 0.4 μm or more and 10 μm or less, preferably 1 μm. More preferably, it is 7 μm or less. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, when it is 10 μm or less, the contact area between metal particles such as silver particles and phosphorus-containing copper alloy particles in the electrode is increased, and the resistivity is more effectively reduced.
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.

  Further, when the electrode paste composition contains silver particles, the silver particle content is silver when the total content of the phosphorus-containing copper alloy particles, the tin-containing particles, and the silver particles is 100% by mass. The particle content 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.

  In addition, in the electrode paste composition of the present invention, from the viewpoint of oxidation resistance, electrode resistivity reduction, and application property to a silicon substrate, the electrode paste composition comprises phosphorus-containing copper alloy particles, tin-containing particles, and The total content of 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. .

  Further, when the electrode paste composition further contains tin-containing particles and silver particles, from the viewpoint of oxidation resistance and low resistivity of the electrode, the total content of phosphorus-containing copper alloy particles, tin-containing particles and silver particles Is 70 mass% or more and 94 mass% or less, the glass particle content is 0.1 mass% or more and 10 mass% or less, and the total content of solvent and resin is 3 mass% or more and 29.9 mass%. The total content of phosphorus-containing copper alloy particles, tin-containing particles and silver particles is preferably 74% by mass to 88% by mass, and the glass particle content is 0.5% by mass to 8% by mass. It is more preferable that 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 or more. Less than 88% by weight of the glass particles Yes ratio 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 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 is not particularly limited as long as it can remove the oxide film formed on the surface of the phosphorus-containing copper alloy particles. Specifically, for example, fatty acids, boric acid compounds, fluorinated compounds, borofluorinated compounds and the like can be mentioned as preferred fluxes.

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

  In addition, the flux content in the electrode paste composition includes the viewpoint of effectively expressing the oxidation resistance of the phosphorus-containing copper alloy particles and the viewpoint of reducing the porosity of the portion where the flux is removed upon completion of firing of the electrode material. From the total mass of the electrode paste composition, it is preferably 0.1% by mass to 5% by mass, more preferably 0.3% by mass to 4% by mass, and 0.5% by mass to It is more preferably 3.5% by mass, particularly preferably 0.7% by mass to 3% by mass, and particularly preferably 1% by mass to 2.5% by mass.

(Other ingredients)
Further, the electrode paste composition may further include other components that are 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 said paste composition for electrodes. The phosphorus-containing copper alloy 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, the electrode paste composition is applied to a region on the silicon substrate where the electrode is to be formed, dried and then baked to form an electrode in a desired region. The method of forming can be mentioned. 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, the electrode for solar cells 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 is applied by screen printing, the electrode paste composition preferably has a viscosity in the range of 20 Pa · s 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 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} .

In addition, as heat treatment conditions (firing conditions) for forming an electrode using the electrode paste composition, heat treatment conditions that are usually used in this technical field can be applied.
Generally, the heat treatment temperature (firing temperature) is 800 ° C. to 900 ° C. However, when the electrode paste composition of the present invention is used, heat treatment conditions at a lower temperature can be applied, for example, 600 ° C. An electrode having good characteristics can be formed at a heat treatment temperature of ˜850 ° 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.

  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.

As a specific example of the method for forming electrodes on the silicon substrate, a method for producing a solar cell element will be described with reference to the drawings, but the present invention is not limited to this.
Cross-sectional views showing examples of typical solar cell elements, and outlines of the light receiving surface and the back surface are shown in FIGS. 1, 2 and 3, respectively.
Usually, single crystal or polycrystalline Si is used for the semiconductor substrate 8 of the solar cell element. This semiconductor substrate 8 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. Phosphorus or the like is doped on the light receiving surface side, an n-type semiconductor diffusion layer 9 is provided with a thickness on the order of submicrons, and a pn junction is formed at the boundary with the p-type bulk portion. Further, on the light receiving surface side, an antireflection layer 10 such as silicon nitride is provided on the diffusion layer 9 by a vapor deposition method or the like with a film thickness of about 100 nm.

Next, the light receiving surface electrode 11 provided on the light receiving surface side, and the current collecting electrode 12 and the output extraction electrode 13 formed on the back surface will be described. The light-receiving surface electrode 11 and the output extraction electrode 13 are formed from the electrode paste composition. Moreover, the current collection electrode 12 is formed from the paste composition for aluminum electrodes containing glass powder.
The light-receiving surface electrode 11 and the output extraction electrode 13 are formed by applying the electrode paste composition to a desired pattern by screen printing or the like and then baking it in the atmosphere at about 600 ° C. to 850 ° C. By using the paste composition for an electrode, 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 11 react with the antireflection layer 10 (fire-through), and the light receiving surface electrode 11 and the diffusion layer are reacted. 9 is electrically connected (ohmic contact).
By forming the light-receiving surface electrode 11 using the electrode paste composition, copper is suppressed while containing copper as a conductive metal, and the light-receiving surface electrode 11 having a low resistivity has good productivity. Formed with.

  On the back surface side, the aluminum in the aluminum electrode paste composition that forms the collecting electrode 12 during firing diffuses to the back surface of the semiconductor substrate 8 to form the electrode component diffusion layer 14, thereby forming the semiconductor substrate 8. Ohmic contact can be obtained between the current collector electrode 12 and the output extraction electrode 13.

FIG. 4A is a perspective view of a light receiving surface and an AA cross-sectional structure which is an example of a solar cell element according to another aspect of the present invention, and FIG. 4B is a plan view of a back side electrode structure. Shown in
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 sides of the light receiving surface and the back surface 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 silicon type solar cell element.

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

On the other hand, a heavily doped layer 5 for preventing carrier recombination is formed on the opposite side (back side) of the light receiving surface. Here, boron (B) or aluminum (Al) is used as an impurity element for forming the high-concentration doped layer 5, and a p ⁺ -type diffusion 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 side, as shown in the plan view of FIG. 4B, the electrode paste composition according to the present invention is printed in stripes on the n-type diffusion layer and the p-type diffusion layer, respectively. By baking, the back electrodes 6 and 7 are 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.

(Tab line)
The element of the present invention has a tab wire electrically connected to an electrode which is a fired product of the paste composition for an electrode formed on a silicon substrate as described above.
The tab line can be appropriately selected from those normally used in the art. For example, a material having a structure in which a conductive material such as a copper wire is covered with solder can be suitably used. The cross-sectional shape of the tab line is not particularly limited, and a rectangular or elliptical shape can be used.

The peel adhesion strength between the electrode and the tab wire in the element is 0.2 N / mm to 2.0 N / mm, but preferably 0.5 N / mm to 2.0 N / mm. When the peel adhesion strength is less than 0.2 N / mm, in the process of manufacturing the element (preferably a solar cell element) after the tab line connection, the manufacturing efficiency may decrease due to the tab line peeling. On the other hand, the tab wire connected to the electrode on the silicon substrate breaks most of the substrate when it is peeled off with a force exceeding 2.0 N / mm, so it is practically difficult to measure a value higher than this. .
In addition, the peeling adhesive strength of a tab wire is obtained by measuring based on JIS-K-6854.

  The connection method of the said tab wire and an electrode will not be restrict | limited especially if a tab wire and an electrode are electrically connected and it can connect so that peeling adhesive strength may be 0.2N / mm-2.0N / mm. Specifically, a solder formed on the tab wire is heated and melted, a method of connecting using CF (Conductive Film), a solder paste, and the like are additionally applied to the electrodes. It can be selected from a method of connecting the tab wire by heating and pressure curing with the tab wire sandwiched.

Of the above, the solder formed on the tab wire is connected by heating and melting, and the connection by solder melting such as the method of connecting the tab wire using a solder paste. In order to reduce a difference in thermal expansion with a conductive material such as a copper wire, it is preferable to connect at a temperature as low as possible. For example, it is more preferable to carry out at a temperature of 180 ° C to 350 ° C.
In addition, the heating method of a tab wire can be suitably selected from the method used normally. Specifically, a method of pressing a soldering iron against the tab wire, a method of automatically performing by a thermocompression bonding machine, and the like can be exemplified.
Moreover, as a crimping | compression-bonding pressure at the time of tab wire heating, it can be 0.1-1.2 MPa, for example, and it is preferable that it is 0.3-1.0 MPa.

  When the tab wire and the electrode are connected using solder, the electrode paste composition constituting the electrode has a phosphorus content of phosphorus-containing copper alloy particles of not less than 6% by mass and not more than 8% by mass. The content of tin-containing particles is preferably 9% by mass or more and 60% by mass or less when the total content of the copper alloy particles and the tin-containing particles is 100% by mass, and the phosphorus content of the phosphorus-containing copper alloy particles When the total content of the phosphorus-containing copper alloy particles and the tin-containing particles is 100% by mass, the content of tin-containing particles is 9 More preferably, it is at least 55% by mass. When the phosphorus content of the phosphorus-containing copper alloy particles and the content of the tin-containing particles are within the above ranges, the desired peel adhesion strength can be easily achieved.

The CF includes, for example, metal particles and a thermosetting resin. CF can be appropriately selected from commercially available ones.
By laminating the tab wire and the electrode via the CF and subjecting it to heat and pressure treatment, the metal particles contained in the CF are aggregated to electrically connect the tab wire and the electrode. At the same time, the desired adhesive strength can be achieved by curing the thermosetting resin.
In this case, the heat and pressure treatment conditions are appropriately selected according to the configuration of the CF. For example, the heating temperature can be 150 ° C. to 220 ° C., the pressure 0.6 MPa to 3.0 MPa, and the heating temperature 160 ° C. to 200 ° C. and the pressure 0.8 MPa to 2.6 MPa are preferable.

  Although the case where the element of the present invention is configured as an element for a solar cell has been described above, the use of the element on which the electrode is formed is not limited to a solar cell, for example, electrode wiring and shield wiring of a plasma display, It can also be suitably used for applications such as ceramic capacitors, antenna circuits, various sensor circuits, and heat dissipation materials for semiconductor devices.

<Solar cell>
The solar cell of the present invention includes at least an element for the solar cell and a sealing material that seals the element, and includes other components as necessary.
The solar cell is arranged on the surface opposite to the light receiving surface of the element for the solar cell, a surface protective material such as glass and light transmissive plastic disposed on the light receiving surface side of the element. It is preferable to include a back surface protective material and a sealing material disposed between the surface protective material and the back surface protective material.
The surface protective material, the back surface protective material, and the sealing material can be used without particular limitation as long as they are used in solar cell manufacturing applications.

  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 Phosphorus-containing copper alloy particles containing 7% by mass of phosphorus were 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 7% by mass of phosphorus. The particle diameter (D50%) of the phosphorus-containing copper alloy particles was 1.5 μm.

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 “G1”) was prepared. The obtained glass G1 had a softening point of 420 ° C. and a crystallization temperature of over 600 ° C.
Using the obtained glass G1, glass particles G1 having a particle diameter (D50%) of 1.7 μm were obtained.

12. Terpineol (isomer mixture) solution containing 85.1 parts of the phosphorus-containing copper alloy particles obtained above, 1.7 parts of glass particles G1, and 3% by mass of ethyl cellulose (EC, weight average molecular weight 190000). Two parts were mixed and stirred for 20 minutes in an agate mortar to prepare electrode paste composition 1.

(B) Fabrication of solar cell element A p-type semiconductor substrate having a film thickness of 190 μm having an n-type semiconductor layer, texture, and 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 is composed of 150 μm wide finger lines and 1.5 mm wide extraction electrodes, and the printing conditions (screen plate mesh, printing speed, printing pressure) are appropriately set so that the thickness of the electrode after firing is 20 μm. It was adjusted. This was placed in an oven heated to 150 ° C. for 15 minutes, and the solvent was removed by evaporation.

Subsequently, the aluminum electrode paste and the electrode paste composition 1 were printed on the back surface by a screen printing method so as to have the shape shown in FIG. 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, using a tunnel furnace (manufactured by Noritake Co., Ltd., single-row transport W / B tunnel furnace), heat treatment (firing) is performed at a firing maximum temperature of 850 ° C. for 10 seconds in an air atmosphere to form a desired electrode. The produced solar cell element 1 was produced.

  Tab wires were connected to the extraction electrodes on the light receiving surface and the back surface of the solar cell element 1 produced above. In addition, the lead wire uses a lead-free solder-plated flat rectangular tab for solar cells, and using a thermocompression bonding apparatus MB-200WH (manufactured by Nikka Equipment & Engineering), heat at a maximum temperature of 240 ° C. for 15 seconds at a pressure of 0.5 MPa. The tab wire was connected by crimping.

In the solar cell element 1 to which the tab wire was connected, a terminal was attached to the tip of the tab wire, and the power generation performance was evaluated by the method described later.
Then, when the 90 degree peel test of the tab wire was conducted based on JIS-K-6854 using a peel tester, the peel adhesive strength of the tab wire was 1.2 N / mm. In addition, EZ-S (made by Shimadzu Corporation) was used for the peel tester.

<Example 2>
In Example 1, the composition of the electrode paste composition was changed as follows. That is, 56.1 parts of phosphorus-containing copper alloy particles (phosphorus content: 7% by mass, D50% is 1.5 μm), tin particles (Sn; particle size (D50%) is 10.0 μm; purity 99.9%) 29.0 parts, 1.7 parts of glass particles G1, and 13.2 parts of a terpineol (isomeric mixture) solution containing 3% by weight of ethylcellulose (EC, weight average molecular weight 190000) are mixed together in an agate mortar. Was stirred for 20 minutes to prepare an electrode paste composition 2.

Except having used the said electrode paste composition 2, the solar cell element 2 was produced similarly to Example 1, and the tab wire was connected.
At this time, the peel adhesion strength of the tab wire was 1.4 N / mm.

<Example 3>
In Example 1, the composition of the electrode paste composition was changed as follows. That is, 45.6 parts of phosphorus-containing copper alloy particles (phosphorus content: 7% by mass, D50% is 1.5 μm), tin particles (Sn; particle size (D50%) is 10.0 μm; purity 99.9%) 35.5 parts, silver particles (Ag; particle size (D50%) 3 μm; purity 99.5%) 4.0 parts, glass G1 particles 1.7 parts, and 3% by weight ethyl cellulose (EC, weight) 13.2 parts of a terpineol (isomer mixture) solution containing an average molecular weight of 190,000) was mixed and stirred for 20 minutes in an agate mortar to prepare an electrode paste composition 3.

Except having used the said electrode paste composition 2, the solar cell element 3 was produced similarly to Example 1, and the tab wire was connected.
At this time, the peel adhesion strength of the tab wire was 1.5 N / mm.

<Examples 4 to 10>
In Example 1, phosphorus content of phosphorus-containing copper alloy particles, particle size (D50%) and content, type and content of tin-containing particles, content of silver particles, type and content of glass particles, 3% Electrode paste compositions 4 to 10 were prepared in the same manner as in Example 1 except that the content of the terpineol solution containing ethylcellulose (EC) was changed as shown in Table 1.
The glass particles G2 are 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), 5 parts of antimony oxide (Sb ₂ O ₃ ). And 5 parts of tungsten oxide (WO ₃ ), and the particle diameter (D50%) was 1.7 μm. The softening point of this glass was 492 ° C., and the crystallization temperature exceeded 600 ° C.

  Then, using the obtained electrode paste compositions 4 to 10 respectively, the desired electrode was prepared in the same manner as in Example 1 except that the heat treatment temperature and treatment time were changed as shown in Table 1. The formed solar cell elements 4 to 10 were respectively produced.

Further, with respect to the produced solar cell elements 4 to 10, tab wires were attached to the extraction electrodes on the light receiving surface and the back surface in the same manner as in Example 1.
At this time, a peel test of the tab wire was performed, and the peel adhesion strength shown in Table 1 was obtained.

<Comparative Example 1>
In the preparation of the electrode paste composition in Example 1, except that the phosphorus-containing copper alloy particles were not used, and only the silver particles were used, and each component was changed so as to have the composition shown in Table 1. In the same manner as in Example 1, an electrode paste composition C1 was prepared.
A solar cell element 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. Further, when a tab wire was attached to the extraction electrode on the light receiving surface and the back surface in the same manner as in Example 1, and a peel test of the tab wire was performed, a peel adhesion strength of 1.7 N / mm was obtained.

<Comparative Example 2>
In Example 1, electrode paste composition C2 was prepared in the same manner as Example 1 except that pure copper containing no phosphorus (phosphorus content was 0%) was changed.
A solar cell element C2 was produced in the same manner as in Example 1 except that the electrode paste composition C5 was used. Further, when tab wires were attached to the extraction electrodes on the light receiving surface and the back surface in the same manner as in Example 1, and a peel test of the tab wires was performed, a peel adhesion strength of 0.1 N / mm was obtained.

<Evaluation>
Evaluation of the produced solar cell element is as follows: 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 2, since the resistivity of the electrode was increased by the oxidation of the copper particles and an oxide film was formed on the electrode surface, the wettability of the solder at the time of connecting the tab wire was significantly reduced, and power was generated. Since power could not be taken out efficiently, evaluation was impossible.

The performance of the solar cell elements produced in Examples 1 to 10 was almost equal to or higher than the measured value of Comparative Example 1.
Further, as a result of measuring diffraction X-rays by the X-ray diffraction method using CuKα rays for the light-receiving surface electrodes of the solar cell element 1 and the solar cell element 7, at least 43.4 ° of diffraction angle (2θ, CuKα rays), 50 The characteristic diffraction peak of copper was shown at .6 ° and 74.2 °. 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 1 and 7 have a phosphorus content of 6% by mass or more and 8% by mass or less. The composition of this part consists of an α-Cu phase and a Cu ₃ P phase from the Cu—P phase diagram. In the initial stage of firing, the α-Cu phase is oxidized and changed to Cu ₂ O. It is considered that this Cu ₂ O is reduced again to α-Cu. In addition, it is thought that the Cu ₃ P phase contained in the phosphorus-containing copper alloy particles or phosphorus derived from this oxide contributes to this reduction reaction.

  Therefore, in the electrode paste composition using the phosphorus-containing copper alloy particles having a phosphorus content of 6% by mass or more and 8% by mass or less, as shown in Examples 1 to 10, the maximum temperature holding time is 10 seconds to Even for 15 seconds, it is considered that the oxidation of copper during firing was suppressed and an electrode having a low resistivity was formed. In addition, since the sintering of the phosphorus-containing copper alloy particles progresses by lengthening the firing time, it is possible to form a denser and lower resistivity electrode, as well as more effective fire-through. The effect that the ohmic contact property with the semiconductor substrate is improved can be obtained.

<Example 11>
Using the electrode paste composition 1 obtained above, a solar cell element 11 having a structure as shown in FIG. 4 was produced. The heat treatment was performed at 850 ° C. for 10 seconds. Tab wires were connected in the same manner as described above for the obtained solar cell elements. When a tab wire peel test was performed, a peel adhesion strength of 1.2 N / mm was obtained.
Moreover, when the power generation performance was evaluated, it was found that good characteristics were exhibited as described above.

DESCRIPTION OF SYMBOLS 1 Cell wafer consisting of p-type silicon substrate 2 Current collecting grid electrode 3 P-type semiconductor layer 4 Through-hole electrode 5 Highly doped layer (p ⁺ type diffusion layer)
6 Back electrode 7 Back electrode 8 p-type silicon substrate 9 n ⁺ type diffusion layer 10 Antireflection film 11 Light receiving surface collecting electrode and output extraction electrode 12 Back surface collecting electrode 13 Back surface output extraction electrode 14 p ⁺ type diffusion layer

Claims (9)

Disposed on a base plate comprising silicon, and fired phosphorous-containing copper alloy particles, glass particles, an electrode paste composition containing a solvent and a resin, comprising the step of forming the electrodes,
Having a tab wire electrically connected on the electrode;
Ri peel strength is 0.2N / mm~2.0N / mm der between the tab wire and the electrode,
The phosphorus content of the phosphorus-containing copper alloy particles is 6% by mass or more and 8% by mass or less,
The electrode paste composition further comprises, a manufacturing method of the element tin-containing particles. The element manufacturing method according to claim 1 , 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 glass particles have a glass softening point of 600 ° C. or lower and a crystallization start temperature of 600 ° C.
The manufacturing method of the element of Claim 1 or Claim 2 exceeding. In the electrode paste composition, the content of the tin-containing particles is 5% by mass to 70% by mass when the total content of the phosphorus-containing copper alloy particles and the tin-containing particles is 100% by mass. The manufacturing method of the element of any one of Claims 1-3. The electrode paste composition, manufacturing method for the device according to any one of claims 1 to 4, further containing 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 method for manufacturing an element according to claim 5, wherein the element is at most%. 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 or more. The element manufacturing method according to claim 5, 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 manufacturing method according to claim 1, wherein the silicon-containing substrate has a pn junction and is used for a solar cell. Preparing a device for use in a solar cell by the method according to claim 8, the method for manufacturing the solar cell and a step of sealing said element.