HK1197847A - Element and solar cell - Google Patents
Element and solar cell Download PDFInfo
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- HK1197847A HK1197847A HK14111180.1A HK14111180A HK1197847A HK 1197847 A HK1197847 A HK 1197847A HK 14111180 A HK14111180 A HK 14111180A HK 1197847 A HK1197847 A HK 1197847A
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Description
Technical Field
The invention relates to an element and a solar cell.
Background
In general, a solar cell is provided with a surface electrode whose wiring resistance and contact resistance are related to a voltage loss related to conversion efficiency, and the wiring width and shape have an influence on the incident amount of sunlight.
The surface electrode of the solar cell is generally formed in the following manner. That is, a conductive composition is applied by screen printing or the like to 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 semiconductor substrate, and the conductive composition is fired at 800 to 900 ℃. The conductive composition forming the surface electrode contains conductive metal powder, glass particles, various additives, and the like.
As the conductive metal powder, silver powder is generally used, but for various reasons, it has been studied to use metal powder other than silver powder. For example, a conductive composition capable of forming an electrode for a solar cell containing silver and aluminum has been proposed (for example, see japanese patent laid-open publication No. 2006-313744). Further, an electrode-forming composition containing silver-containing metal nanoparticles and metal particles other than silver, such as copper, has been proposed (see, for example, japanese patent application laid-open No. 2008-226816).
Disclosure of Invention
Silver generally used for forming an electrode is a noble metal, and due to resource problems and the high price of the raw material metal itself, it is desired to propose a paste material in place of a silver-containing conductive composition (silver-containing paste). As a promising material to replace silver, copper used for a semiconductor wiring material is exemplified. Copper is abundant in resources, and the cost of the raw material metal is about one percent of that of silver, so that the raw material metal is cheap. However, copper is a material that is easily oxidized at a high temperature of 200 ℃ or higher, and when copper is contained as a conductive metal in the electrode-forming composition described in patent document 2, for example, a special step of firing in a gas atmosphere such as nitrogen gas is required to form an electrode by firing copper.
The invention provides an element having an electrode in which copper oxidation is suppressed during firing and which has a low resistivity, and a solar cell having the element.
<1> an element comprising:
a silicon substrate;
an electrode provided on the silicon substrate, the electrode being a fired product of a paste composition for electrodes, the paste composition containing phosphorus-containing copper alloy particles, glass particles, a solvent, and a resin; and
a solder layer disposed on the electrode and containing flux.
<2> the device as stated in above <1>, wherein the flux contains at least 1 selected from the group consisting of halides, inorganic acids, organic acids, and rosins.
<3> the element according to the above <2>, wherein the halide is at least 1 selected from the group consisting of chloride and bromide.
<4> the element according to the above <2>, wherein the inorganic acid comprises at least 1 selected from the group consisting of hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid and boric acid.
<5> the element as stated in above <2>, wherein the organic acid comprises a carboxylic acid.
<6> the element as stated in above <5>, wherein the carboxylic acid contains at least 1 selected from formic acid, acetic acid and oxalic acid.
<7> the device according to any one of above <2> to <6>, wherein the flux contains 5 mass% or more of rosin.
<8> the device according to any one of above <1> to <7>, wherein the solder layer contains 42 mass% or more of tin.
<9> the element according to any one of above <1> to <8>, which is used for a solar cell in which the silicon substrate has an impurity diffusion layer and forms a pn junction, and the electrode is provided on the impurity diffusion layer.
<10> a solar cell, comprising:
the element for a solar cell according to the above <9 >; and
a pole lug connected to the solder layer of the electrode of the component. According to the present invention, an element having an electrode in which copper oxidation during firing is suppressed and which has a low resistivity can be provided, and a solar cell having the element can be provided.
Drawings
Fig. 1 is a cross-sectional view of a solar cell element of the present invention.
Fig. 2 is a plan view showing a light receiving surface side of the solar cell element of the present invention.
Fig. 3 is a plan view showing the back side of the solar cell element of the present invention.
Fig. 4A is a perspective view showing an AA cross-sectional structure of a back contact type solar cell as an example of the solar cell element of the present invention.
Fig. 4B is a plan view showing a back-side electrode structure of a back-contact solar cell as an example of the solar cell device of the present invention.
Detailed Description
Hereinafter, embodiments of the present invention will be described in detail.
In the present specification, "to" represent ranges including the numerical values recited before and after the range as the minimum value and the maximum value, respectively.
In addition, the term "step" in the present specification is included in the term as long as the initial object of the step can be achieved, unless it is an independent step or it cannot be clearly distinguished from other steps.
In the present specification, the amount of each component in the composition refers to the total amount of a plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition.
< element >
The element of the present invention comprises: the semiconductor device includes a silicon substrate, an electrode provided on the silicon substrate, and a solder layer provided on the electrode. The electrode is a fired product of an electrode paste composition containing phosphorus-containing copper alloy particles, glass particles, a solvent, and a resin. The solder layer contains flux.
The electrode is formed using phosphorus-containing copper alloy particles, and thus an electrode having a low resistivity can be obtained. The reason for this is considered to be that phosphorus contained in the copper alloy particles functions as a reducing agent for the copper oxide, and the oxidation resistance of copper is improved. This presumably suppresses the oxidation of copper, thereby forming an electrode having a low resistivity.
Further, since the solder layer provided on the electrode contains flux, adhesion between the electrode and the solder layer is improved, and contact resistance at the interface between the electrode and the solder layer is reduced. The reason for this is considered that the use of flux can remove the surface oxide film of the solder layer, improve the wettability of the surface, and suppress the reformation of the surface oxide film. Accordingly, it is estimated that the adhesion between the electrode and the solder layer is improved and the contact resistance at the interface between the electrode and the solder layer is reduced.
The method of making the solder layer contain flux is not particularly limited, and examples thereof include: and a method of applying flux to a surface of at least one of the electrode and the solder layer. Then, the electrode is brought into contact with the solder layer and pressed, and heat treatment is further performed, thereby connecting the electrode to the solder layer.
Hereinafter, each constituent member of the element of the present invention will be described.
[ silicon substrate 1
The silicon substrate in the present invention is not particularly limited as long as it is a silicon substrate in a form for forming an electrode using the paste composition for an electrode and forming a solder layer on the electrode. Examples of the silicon substrate include: a silicon substrate having a pn junction for forming a solar cell, a silicon substrate used for manufacturing a semiconductor device other than a solar cell, and the like.
[ electrodes ]
The electrode of the present invention is a fired product of a paste composition for an electrode containing phosphorus-containing copper alloy particles, glass particles, a solvent and a resin. The details of the paste composition for electrode used for electrode formation will be described below.
The paste composition for an electrode of the present invention comprises: at least 1 phosphorus-containing copper alloy particle, at least 1 glass particle, at least 1 solvent, and at least 1 resin. With this configuration, an electrode can be formed which suppresses the formation of an oxide film of copper during firing and has a lower resistivity than when copper particles are used.
(phosphorus-containing copper alloy particles)
The paste composition for an electrode of the present invention contains at least 1 kind of phosphorus-containing copper alloy particles.
The content of phosphorus contained in the phosphorus-containing copper alloy particles is preferably 6 mass% or more and 8 mass% or less, more preferably 6.3 mass% or more and 7.8 mass% or less, and still more preferably 6.5 mass% or more and 7.5 mass% or less, from the viewpoint of oxidation resistance and low resistivity. When the content of phosphorus contained in the phosphorus-containing copper alloy particles is 8 mass% or less, the resistivity of the formed electrode can be further lowered, and the productivity of the phosphorus-containing copper alloy particles is excellent. Further, the phosphorus content in the phosphorus-containing copper alloy particles is 6 mass% or more, and thus more excellent oxidation resistance can be achieved.
As a phosphorus-containing copper alloy used for the above-mentioned phosphorus-containing copper alloy particles, a brazing material called a phosphorus copper brazing filler metal (phosphorus concentration: usually about 7 mass% or less) is known. Phosphor copper solder can also be used as a copper to copper bonding agent. By using the phosphorus-containing copper alloy particles in the paste composition for an electrode of the present invention, an electrode having excellent oxidation resistance and low specific resistance can be formed by utilizing the reducibility of phosphorus to a copper oxide. Moreover, the low-temperature sintering of the electrode can be realized, and the effect of reducing the process cost can be obtained.
The phosphorus-containing copper alloy particles are composed of an alloy containing copper and phosphorus, but may further contain other atoms. As other atoms, there may be mentioned: ag. Mn, Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Mo, Ti, Co, Ni, Au, etc.
The content of other atoms contained in the phosphorus-containing copper alloy particles may be, for example, 3 mass% or less in the phosphorus-containing copper alloy particles, and is preferably 1 mass% or less from the viewpoint of oxidation resistance and low resistivity.
In the present invention, the phosphorus-containing copper alloy particles may be used alone in 1 kind, or may be used in combination in 2 or more kinds.
The particle diameter of the phosphorus-containing copper alloy particles is not particularly limited, and the particle diameter when the cumulative weight is 50% (hereinafter sometimes abbreviated as "D50%") is preferably 0.4 to 10 μm, more preferably 1 to 7 μm. The oxidation resistance can be further effectively improved by making the particle diameter of the phosphorus-containing copper alloy particles 0.4 μm or more. Further, when the particle diameter of the phosphorus-containing copper alloy particles is 10 μm or less, the contact area between the phosphorus-containing copper alloy particles in the electrode becomes large, and the resistivity of the formed electrode is more effectively lowered. The particle diameter of the phosphorus-containing copper alloy particles was measured by a Microtrac particle size distribution measuring apparatus (MT 3300, manufactured by japan electronics corporation).
The shape of the phosphorus-containing copper alloy particles is not particularly limited, and may be any of substantially spherical, flat, massive, plate-like, scaly, and the like. The phosphorus-containing copper alloy particles are preferably substantially spherical, flat or plate-like in shape from the viewpoint of oxidation resistance and low resistivity.
The content of the phosphorus-containing copper alloy particles contained in the paste composition for electrodes of the present invention, or the total content of the phosphorus-containing copper alloy particles and silver particles in the case of containing silver particles described later, may be, for example, 70 to 94% by mass, and is preferably 72 to 90% by mass, and more preferably 74 to 88% by mass, from the viewpoints of oxidation resistance and low resistivity.
The phosphorus-containing copper alloy used for the phosphorus-containing copper alloy particles can be produced by a generally used method. The phosphorus-containing copper alloy particles can be prepared using a phosphorus-containing copper alloy prepared so as to have a desired phosphorus content, can be prepared by a conventional method for preparing metal powder, and can be produced by a conventional method using, for example, a water atomization method. Further, the details of the water atomization method are described in the metal laboratory (department of pill & lten & gt, published services) and the like.
Specifically, for example, a phosphorus-containing copper alloy is melted and powdered by spraying through a nozzle, and the obtained powder is dried and classified, whereby desired phosphorus-containing copper alloy particles can be produced. Further, by appropriately selecting the classification conditions, phosphorus-containing copper alloy particles having a desired particle diameter can be produced.
(glass particles)
The paste composition for electrodes of the present invention contains at least 1 type of glass particles. When the paste composition for an electrode contains glass particles, the adhesion between the electrode portion and the substrate during firing is improved. Further, at the electrode forming temperature, the silicon nitride film as the antireflection film is removed by so-called fire through (fire through), so that ohmic contact between the electrode and the silicon substrate is formed.
The glass particles are not particularly limited as long as they soften and melt at the electrode forming temperature, can oxidize the silicon nitride film in contact therewith, and can infiltrate and oxidize the resulting silica, thereby making it possible to remove the antireflection film.
In the present invention, the glass particles preferably include a glass having a glass softening point of 600 ℃ or less and a crystallization start temperature of more than 600 ℃ from the viewpoints of oxidation resistance and low electrical resistivity of the electrode. The glass softening point is measured by a general method using a thermomechanical analyzer (TMA), and the crystallization start temperature is measured by a general method using a differential thermal-thermogravimetric analyzer (TG-DTA).
In general, the glass particles contained in the electrode composition may contain a lead-containing glass from the viewpoint of efficiently digesting silica. Examples of such lead-containing glasses include those described in japanese patent No. 03050064, and these glasses can be preferably used in the present invention.
In the present invention, it is preferable to use a lead-free glass that does not substantially contain lead in consideration of the influence on the environment. Examples of the lead-free glass include: the lead-free glass described in paragraphs 0024 to 0025 of jp 2006-313744 a and the lead-free glass described in jp 2009-188281 a and the like are preferably selected from these lead-free glasses and applied to the present invention.
The glass components constituting the glass particles used in the paste composition for electrodes of the present invention include: silicon dioxide (SiO)2) Phosphorus oxide (P)2O5) Alumina (Al)2O3) Boron oxide (B)2O3) Vanadium oxide (V)2O5) Potassium oxide (K)2O), bismuth oxide (Bi)2O3) Sodium oxide (Na)2O), lithium oxide (Li)2O), 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)2O3) Niobium oxide (Nb)2O5) Tantalum oxide (Ta)2O5) Yttrium oxide (Y)2O3) Titanium oxide (TiO)2) Germanium oxide (GeO)2) Tellurium oxide (TeO)2) Lutetium oxide (Lu)2O3) Antimony oxide (Sb)2O3) Copper oxide (CuO), iron oxide (FeO), silver oxide (AgO), and manganese oxide (MnO).
Among them, SiO is preferably used2、P2O5、Al2O3、B2O3、V2O5、Bi2O3At least 1 of ZnO, and PbO. Specifically, the glass component may include SiO2、PbO、B2O3、Bi2O3And Al2O3The glass composition of (1). In the case of such glass particles, the softening point is effectively lowered, and the wettability with the phosphorus-containing copper alloy particles and the silver particles added as needed is improved, so that sintering between the particles during firing is promoted, and an electrode having a low specific resistance can be formed.
On the other hand, from the viewpoint of lowering the contact resistivity of the formed electrode, it is preferable thatGlass particles containing phosphorus pentoxide (phosphoric acid glass, P)2O5Glass particles), more preferably glass particles (P) containing vanadium pentoxide in addition to phosphorus pentoxide2O5-V2O5Are glass particles). By further containing vanadium pentoxide, the oxidation resistance is further improved, and the resistivity of the electrode is further lowered. The reason for this is considered that, for example, by further containing vanadium pentoxide, the softening point of the glass is lowered. Using phosphorus pentoxide-vanadium pentoxide glass particles (P)2O5-V2O5Glass particles), the content of vanadium pentoxide is preferably 1% by mass or more, more preferably 1% by mass to 70% by mass, based on the total mass of the glass.
The particle size of the glass particles is not particularly limited, and the particle size when the cumulative weight is 50% (hereinafter may be abbreviated as "D50%"), is preferably 0.5 μm to 10 μm, and more preferably 0.8 μm to 8 μm. By making the particle diameter of the glass particles 0.5 μm or more, the workability in the production of the paste composition for electrodes is improved. Further, by making the particle diameter of the glass particles to be 10 μm or less, the glass particles are easily uniformly dispersed in the paste composition for an electrode, and burn-through can be efficiently caused in the firing step, and the adhesion between the formed electrode and the silicon substrate is also improved.
The content of the glass particles is preferably 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, and still more preferably 1 to 7% by mass, based on the total mass of the paste composition for electrodes. By containing the glass particles in the content ratio within this range, oxidation resistance, low resistivity of the electrode, and low contact resistance can be more effectively achieved.
(solvent and resin)
The paste composition for electrodes of the present invention contains at least 1 kind of solvent and at least 1 kind of resin. Thus, the liquid properties (for example, viscosity, surface tension, etc.) of the paste composition for an electrode of the present invention can be adjusted to desired liquid properties according to the method of application to a silicon substrate.
The solvent is not particularly limited. Examples thereof include: hydrocarbon solvents such as hexane, cyclohexane and toluene; chlorinated hydrocarbon solvents such as dichloroethylene, dichloroethane, dichlorobenzene, etc.; cyclic ether solvents such as tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, 1, 3-dioxolane, trioxane and the like; 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; alcohol compounds such as ethanol, 2-propanol, 1-butanol and diacetone alcohol; ester-based solvents of polyhydric alcohols such as 2, 2, 4-trimethyl-1, 3-pentanediol monoacetate, 2, 4-trimethyl-1, 3-pentanediol monopropionate, 2, 4-trimethyl-1, 3-pentanediol monobutyrate, 2, 4-trimethyl-1, 3-pentanediol monoisobutyrate, 2, 4-triethyl-1, 3-pentanediol monoacetate, ethylene glycol monobutyl ether acetate, and diethylene glycol monobutyl ether acetate; ether solvents of polyhydric alcohols such as butyl cellosolve, diethylene glycol monobutyl ether, and diethylene glycol diethyl ether; terpene-based solvents such as α -terpinene, α -terpineol, myrcene, alloocimene, limonene, dipentene, α -pinene, β -pinene, terpineol, carvone, ocimene, phellandrene, and mixtures of these solvents.
In the present invention, the solvent is preferably at least 1 selected from the group consisting of an ester-based solvent of a polyhydric alcohol, a terpene-based solvent and an ether-based solvent of a polyhydric alcohol, and more preferably at least 1 selected from the group consisting of an ester-based solvent of a polyhydric alcohol and a terpene-based solvent, from the viewpoints of coatability and printability when forming the paste composition for an electrode on a silicon substrate.
In the present invention, 1 kind of the above-mentioned solvent may be used alone, or 2 or more kinds may be used in combination.
The resin is not particularly limited as long as it is thermally decomposable by firing, and a resin generally used in the art can be used. Specifically, there may be mentioned: cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and nitrocellulose; polyvinyl alcohols; polyvinyl pyrrolidones; an acrylic resin; vinyl acetate-acrylate copolymers; butyral resins such as polyvinyl butyral; alkyd resins such as phenol-modified alkyd resins and castor oil fatty acid-modified alkyd resins; an epoxy resin; a phenol resin; rosin ester resins, and the like.
In the present invention, the resin is preferably at least 1 selected from the group consisting of a cellulose resin and an acrylic resin, and more preferably at least 1 selected from the group consisting of a cellulose resin, from the viewpoint of the disappearance thereof upon firing.
In the present invention, the above-mentioned resins may be used alone in 1 kind, or may be used in combination with 2 or more kinds.
In the present invention, the weight average molecular weight of the resin is not particularly limited. The weight average molecular weight of the resin is preferably 5000 to 500000, more preferably 10000 to 300000. When the weight average molecular weight of the resin is 5000 or more, the increase in viscosity of the paste composition for electrodes can be suppressed. The reason for this is considered to be that, for example, when the copper alloy particles are adsorbed to phosphorus-containing copper alloy particles, the steric repulsion is effectively exerted, and the aggregation of the particles is suppressed. On the other hand, when the weight average molecular weight of the resin is 500000 or less, the agglomeration of the resins in the solvent can be suppressed, and as a result, the viscosity of the paste composition for electrodes can be suppressed from increasing. Further, when the weight average molecular weight of the resin is suppressed to an appropriate value, the combustion temperature of the resin can be suppressed from rising, and the resin can be suppressed from remaining as foreign matter without being completely combusted at the time of firing the paste composition for an electrode, so that the resistance of the electrode can be lowered.
In the paste composition for an electrode of the present invention, the content of the solvent and the resin may be appropriately selected depending on the desired liquid properties and the types of the solvent and the resin used.
For example, the content of the resin is preferably 0.01 to 5% by mass, more preferably 0.05 to 4% by mass, even more preferably 0.1 to 3% by mass, and particularly preferably 0.15 to 2.5% by mass, based on the total mass of the paste composition for electrodes.
The total content of the solvent and the resin in the total mass of the paste composition for electrodes is preferably 3 to 29.8 mass%, more preferably 5 to 25 mass%, and still more preferably 7 to 20 mass%.
When the content of the solvent and the resin is within the above range, the paste composition for an electrode can be applied to a silicon substrate with good suitability, and an electrode having a desired width and height can be more easily formed.
(silver ion)
The paste composition for an electrode of the present invention preferably further contains at least 1 kind of silver particles. By containing silver particles, the oxidation resistance is further improved, and the resistivity as an electrode is further lowered. Further, the effect of improving solder connectivity can be obtained when the solar cell module is manufactured. The reason for this is considered as follows, for example.
In general, in the temperature range of 600 to 900 ℃ in the electrode formation temperature range, a small amount of silver in solid solution in copper and a small amount of copper in silver are generated, and a copper-silver solid solution layer (solid solution region) is formed at the interface between copper and silver. Although a solid solution region is not formed when the mixture of the phosphorus-containing copper alloy particles and the silver particles is heated to a high temperature and then slowly cooled to room temperature, it is considered that the solid solution layer at a high temperature covers the surfaces of the silver particles and the phosphorus-containing copper alloy particles as an unbalanced solid solution phase or an eutectic structure of copper and silver since the mixture is cooled from a high temperature region to room temperature for several seconds at the time of forming the electrode. It can be considered that: such a copper-silver solid solution layer contributes to oxidation resistance of the phosphorus-containing copper alloy particles at the electrode forming temperature.
The copper-silver solid solution layer begins to form at a temperature of 300 ℃ to 500 ℃ or higher. Therefore, it is considered that the oxidation resistance of the phosphorus-containing and copper-containing particles can be more effectively improved by using the silver particles in combination with the phosphorus-containing and copper-containing particles exhibiting the peak temperature of the heat generation peak of the maximum area in the differential thermal-thermogravimetric simultaneous measurement at 280 ℃ or more, and the resistivity of the formed electrode can be further lowered.
The silver constituting the above silver particles may contain other atoms which are inevitably mixed. Examples of other atoms inevitably mixed include: sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Mo, Ti, Co, Ni, Au, etc.
The content of other atoms contained in the silver particles may be 3 mass% or less, for example, and is preferably 1 mass% or less from the viewpoint of melting point and reduction in the resistivity of the electrode.
The particle diameter of the silver particles in the present invention is not particularly limited, and the particle diameter (D50%) when the cumulative mass is 50% is preferably 0.4 to 10 μm, and more preferably 1 to 7 μm. The oxidation resistance is further effectively improved by making the particle size of the silver particles 0.4 μm or more. Further, when the particle size of the silver particles is 10 μm or less, the contact area between the silver particles and the metal particles such as phosphorus-containing and copper-containing particles in the electrode becomes large, and the resistivity of the formed electrode is more effectively reduced.
In the paste composition for an electrode of the present invention, the relationship between the particle diameter (D50%) of the phosphorus-containing and copper-containing particles and the particle diameter (D50%) of the silver particles is not particularly limited, but it is preferable that the particle diameter (D50%) of one of the particles is smaller than the particle diameter (D50%) of the other of the particles, and it is more preferable that the ratio of the particle diameter (D50%) of one of the particles to the particle diameter (D50%) of the other of the particles is 1 to 10. Thereby, the resistivity of the electrode is more effectively lowered. This is considered to be caused by the fact that, for example, the contact area between metal particles such as phosphorus-containing copper-containing particles and silver particles in the electrode is increased.
The content of the silver particles in the paste composition for an electrode of the present invention is preferably 8.4 to 85.5% by mass, and more preferably 8.9 to 80.1% by mass, in the paste composition for an electrode, from the viewpoint of oxidation resistance and low electrical resistivity of the electrode.
Further, in the present invention, from the viewpoint of oxidation resistance and low electrical resistivity of the electrode, the content of the phosphorus-containing and copper-containing particles is preferably 9 to 88 mass%, more preferably 17 to 77 mass%, when the total amount of the phosphorus-containing and copper-containing particles and the silver particles is 100 mass%. When the content of the phosphorus-containing and copper-containing particles is 9 mass% or more with respect to the total amount of the phosphorus-containing and copper-containing particles and the silver particles, for example, when the glass particles contain vanadium pentoxide, the reaction between silver and vanadium is suppressed, and the volume resistivity of the electrode is further lowered. In addition, in the hydrofluoric acid aqueous solution treatment of forming a silicon substrate as an electrode for the purpose of improving energy conversion efficiency in the production of a solar cell, the resistance of the electrode material to hydrofluoric acid aqueous solution (the property that the electrode material is not peeled from the silicon substrate by the hydrofluoric acid aqueous solution) is improved. Further, when the content of the phosphorus-containing and copper-containing particles is 88 mass% or less, contact between copper contained in the phosphorus-containing and copper-containing particles and the silicon substrate can be further suppressed, and the contact resistance of the electrode can be further reduced.
In the paste composition for an electrode of the present invention, the total content of the phosphorus-containing and copper-containing particles and the silver particles is preferably 70 to 94% by mass, more preferably 72 to 92% by mass, even more preferably 72 to 90% by mass, and particularly preferably 74 to 88% by mass, from the viewpoints of oxidation resistance, low electrical resistivity of an electrode, and coatability on a silicon substrate.
When the total content of the phosphorus-containing and copper-containing particles and the silver particles is 70 mass% or more, a suitable viscosity can be easily achieved when the paste composition for electrodes is applied. Further, the generation of whitening (white spots) when the paste composition for electrodes is applied can be more effectively suppressed by setting the total content of the phosphorus-containing and copper-containing particles and the silver particles to 94% by mass or less.
In the paste composition for an electrode of the present invention, from the viewpoint of oxidation resistance and low electrical resistivity of an electrode, it is preferable that the total content of the phosphorus-containing copper-containing particles and the silver particles is 70 to 94% by mass, the content of the glass particles is 0.1 to 10% by mass, and the total content of the solvent and the resin is 3 to 29.8% by mass; more preferably, the total content of the phosphorus-containing and copper-containing particles and the silver particles is 74 to 88 mass%, the content of the glass particles is 1 to 7 mass%, and the total content of the solvent and the resin is 7 to 20 mass%.
(phosphorus-containing Compound)
The paste composition for an electrode may further contain at least 1 phosphorus-containing compound. Thereby, the oxidation resistance is more effectively improved, and the resistivity of the electrode is further lowered. Further, the element in the phosphorus-containing compound diffuses as an n-type dopant in the silicon substrate, and the effect of improving the power generation efficiency in the case of producing a solar cell can be obtained.
The phosphorus-containing compound is preferably a compound having a high phosphorus atom content in the molecule and not causing evaporation or decomposition under a temperature condition of about 200 ℃.
Specific examples of the phosphorus-containing compound include: phosphorus inorganic acids such as phosphoric acid, phosphates such as ammonium phosphate, phosphate esters such as alkyl phosphate esters and aryl phosphate esters, cyclic phosphazenes such as hexaphenoxyphosphazene, and derivatives of these compounds.
The phosphorus-containing compound in the present invention is preferably at least 1 selected from phosphoric acid, ammonium phosphate, phosphate ester, and cyclic phosphazene, and more preferably at least 1 selected from phosphate ester and cyclic phosphazene, from the viewpoint of oxidation resistance and low electrical resistivity of the electrode.
The content of the phosphorus-containing compound in the present invention is preferably 0.5 to 10% by mass, and more preferably 1 to 7% by mass, based on the total mass of the paste composition for an electrode, from the viewpoints of oxidation resistance and low electrical resistivity of an electrode.
In the present invention, it is preferable that the phosphorus-containing compound contains 0.5 to 10 mass% of at least 1 selected from the group consisting of phosphoric acid, ammonium phosphate, phosphoric acid ester, and cyclic phosphazene; more preferably, at least 1 kind selected from the group consisting of phosphate esters and cyclic phosphazenes is contained in an amount of 1 to 7 mass% based on the total mass of the paste composition for electrodes.
(other Components)
The paste composition for electrodes of the present invention may further contain, in addition to the above-mentioned components, other components generally used in the art as needed. Examples of other components include: plasticizers, dispersants, surfactants, inorganic binders, metal oxides, ceramics, organometallic compounds, and the like.
The method for producing the paste composition for electrodes of the present invention is not particularly limited. The phosphor-copper-containing particles, the glass particles, the solvent, the resin, and, if necessary, the silver particles can be produced by dispersing and mixing the phosphor-copper-containing particles, the glass particles, the solvent, the resin, and the silver particles by a commonly used dispersing and mixing method.
In the present invention, the flux is preferably applied to the surface of the electrode. The flux used for the electrodes is the same as the flux used for the solder layer described later, and the preferred range is the same. The method of applying the flux to the electrode is also the same as that for applying the flux to the solder layer.
(method of manufacturing electrode)
In the method for producing an electrode using the paste composition for an electrode of the present invention, an electrode can be formed in a desired region by applying the paste composition for an electrode to a region where the electrode is formed, drying the composition, and then firing the dried composition. By using the paste composition for an electrode, an electrode having a low resistivity can be formed even when firing treatment is performed in the presence of oxygen (for example, in the atmosphere).
Specifically, for example, when forming a solar cell electrode using the paste composition for an electrode, the solar cell electrode having a low specific resistance can be formed into a desired shape by applying the paste composition for an electrode onto a silicon substrate so as to have a desired shape, drying the composition, and then firing the dried composition. Further, by using the paste composition for an electrode, an electrode having a low resistivity can be formed even when firing treatment is performed in the presence of oxygen (for example, in the atmosphere).
Examples of the method for applying the paste composition for an electrode to a silicon substrate include screen printing, an ink jet method, a dispenser method, and the like, and application by screen printing is preferable from the viewpoint of productivity.
When the paste composition for an electrode of the present invention is applied by screen printing, it preferably has a viscosity in the range of 80Pa · s to 1000Pa · s. In addition, the viscosity of the paste composition for electrodes can be measured at 25 ℃ using a Brookfield HBT viscometer.
The amount of the paste composition for an electrode to be applied can be appropriately selected depending on the size of the electrode to be formed. For example, the amount of the paste composition for electrodes can be set to 2 g/m2～10g／m2Preferably 4 g/m2～8g／m2。
The heat treatment conditions (firing conditions) for forming an electrode using the paste composition for an electrode of the present invention can be those generally used in the art.
The heat treatment temperature (firing temperature) is usually 800 to 900 ℃, but when the paste composition for an electrode of the present invention is used, heat treatment conditions at a lower temperature can be applied, and an electrode having good characteristics can be formed at a heat treatment temperature of, for example, 600 to 850 ℃.
The heat treatment time may be appropriately selected depending on the heat treatment temperature, and may be, for example, 1 to 20 seconds.
[ solder layer ]
The solder layer of the present invention is provided on the electrode, and connects the electrode to an electrode tab or the like. The solder layer of the present invention contains flux. When the solder layer contains flux, adhesion between the electrode and the solder layer is improved, and contact resistance at the interface between the electrode and the solder layer is reduced.
The type of solder material constituting the solder layer is not particularly limited, and a lead-containing solder material and a lead-free solder material are exemplified. Specifically, examples of the lead-containing solder material include Sn-Pb, Sn-Pb-Bi, and Sn-Pb-Ag. Examples of the lead-free solder material include Sn-Ag-Cu, Sn-Ag, Sn-Sb, Sn-Cu, Bi-Sn, In-Sn and the like.
Among these, from the viewpoint of environmental protection, a lead-free solder material is preferably used, and further, a lead-free solder material containing 32 mass% or more of tin is more preferably used as the lead-free solder material, and a lead-free solder material containing 42 mass% or more of tin is even more preferably used.
The flux in the present invention is not particularly limited as long as it can connect the electrode and the solder layer to each other by removing the surface oxide film of the electrode and the solder layer, and by improving the wettability of the surface and suppressing the re-formation of the surface oxide film. Specifically, for example, at least 1 flux component selected from an inorganic acid, a halide, an organic acid, and rosin is preferably contained.
Examples of the inorganic acid include: hydrobromic acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, sulfuric acid, hydrofluoric acid, and the like, and preferably contains at least 1 selected from hydrobromic acid, hydrochloric acid, nitric acid, phosphoric acid, and boric acid.
The halide preferably contains at least 1 selected from the group consisting of chloride and bromide. Examples of the chloride include: zinc chloride, ammonium chloride, dichloromethane, magnesium chloride, bismuth chloride, barium chloride, tin chloride, silver chloride, potassium chloride, indium chloride, antimony chloride, aluminum chloride, etc., and preferably contains at least 1 selected from zinc chloride and ammonium chloride. Examples of the bromide include: phosphorus bromide, iodine bromide, methylene bromide, germanium bromide, sulfur bromide, ammonium bromide, zinc bromide, etc., and preferably contains at least 1 selected from ammonium bromide and zinc bromide.
Examples of the organic acid include: the carboxylic acid compound, phenol derivative, and sulfonic acid compound are preferably carboxylic acid compounds from the viewpoint of easily removing the surface oxide film of the electrode and the solder layer. Examples of the carboxylic acid compound include: formic acid, acetic acid, oxalic acid, lauric acid, myristic acid, palmitic acid, stearic acid, sorbic acid, stearynoic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, heptadecanoic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid, lactic acid, malic acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, mellitic acid, cinnamic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, pyruvic acid, aconitic acid, amino acids, nitrocarboxylic acids, and the like, and preferably at least 1 selected from formic acid, acetic acid, and oxalic acid. The phenol derivative includes phenol resin, salicylic acid, picric acid, and the like, and preferably contains phenol resin.
In the present invention, these flux components may be used alone in 1 kind, or in combination of 2 or more kinds. When 2 or more kinds are used in combination, preferable combinations include: a combination of rosin and an organic acid, a combination of rosin and an inorganic acid, a combination of rosin and a halide, a combination of an inorganic acid and a halide, a combination of a halide and a halide, and the like, and more preferable combinations include: a combination of rosin and an organic acid, a combination of rosin and an inorganic acid, a combination of rosin and a halide. When the rosin is combined with other flux components as described above, the rosin is contained in an amount of preferably 5 to 40 mass%, more preferably 10 to 30 mass%, and still more preferably 12 to 20 mass% of the total flux components.
The flux may contain a solvent from the viewpoint of workability when applying the flux to the electrode and the solder layer. The solvent is preferably selected appropriately according to the kind of the flux components such as inorganic acid, halide, organic acid, rosin, and the like.
Examples of the solvent include: water; ether acetate solvents such as ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, butyl carbitol acetate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, diethylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol n-butyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, dipropylene glycol methyl ether acetate, and dipropylene glycol ethyl ether acetate; terpene solvents such as α -terpinene, α -terpineol, myrcene, alloocimene, limonene, dipentene, α -pinene, β -pinene, terpineol, carvone, ocimene, and phellandrene; alcohol solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, tert-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonanol, n-decanol, sec-dodecyl alcohol, trimethylnonanol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, phenol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 1, 2-propylene glycol, 1, 3-butylene glycol, diethylene glycol, dipropylene glycol, glycerol, triethylene glycol, tripropylene glycol, and the like; ketone solvents such as acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-isopropyl ketone, methyl-n-butyl ketone, methyl-isobutyl ketone, methyl-n-amyl ketone, methyl-n-hexyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2, 4-pentanedione, acetonylacetone, γ -butyrolactone, and γ -valerolactone; diethyl ether, methyl ethyl ether, methyl n-propyl ether, diisopropyl ether, tetrahydrofuran, methyl tetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl mono-n-propyl ether, diethylene glycol methyl mono-n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di-n-butyl ether, diethylene glycol methyl mono-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl mono-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene glycol methyl mono-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl mono-n-butyl ether, diethylene glycol methyl mono-n-, Diethylene glycol di-n-butyl ether, tetraethylene glycol methyl-mono-n-hexyl ether, tetraethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl ether, dipropylene glycol methyl-mono-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-mono-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl ether, tripropylene glycol methyl-mono-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-mono-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl-mono-n-butyl ether, dipropylene glycol di-n-butyl ether, tetrapropylene glycol methyl-mono-n-hexyl ether, propylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol, Ether solvents such as tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methyl pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-butyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, ethylene glycol diacetate, methoxytriethylene glycol acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl acetate, benzyl acetate, cyclohexyl acetate, n-butyl acetate, nonyl acetate, methyl acetoacetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ester solvents such as ethyl lactate, n-butyl lactate, and n-pentyl lactate; aprotic polar solvents such as acetonitrile, N-methylpyrrolidone, N-ethylpyrrolidone, N-propylpyrrolidone, N-butylpyrrolidone, N-hexylpyrrolidone, N-cyclohexylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, and dimethylsulfoxide; glycol monoether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriethylene glycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, and the like. These solvents may be used alone in 1 kind, or in combination of 2 or more kinds.
When rosin is used as a flux component in the flux, glycerin, ethylene glycol, isopropyl alcohol, etc. are preferably used as a solvent, when the inorganic acid is used as a flux component, water, butyl carbitol acetate, etc. are preferably used, when the halide is used as a flux component, water, terpineol, etc. are preferably used, and when an organic acid is used as a flux component, glycerin, ethylene glycol, isopropyl alcohol, etc. are preferably used.
The flux may further contain other components. Examples of the other component include esters of the above-mentioned carboxylic acid compounds. Specific examples of the ester of the carboxylic acid compound include: ethyl acetate, trimethyl borate, methyl butyrate, methyl salicylate, ethyl formate, ethyl butyrate, ethyl hexanoate, amyl acetate, isoamyl acetate, amyl valerate, amyl butyrate, octyl acetate, and the like, and preferably at least 1 selected from ethyl acetate and trimethyl borate.
The content of the flux component in the flux is preferably appropriately adjusted. For example, when the flux component is rosin, the flux preferably contains 5 mass% or more of rosin, and more preferably contains 10 mass% or more of rosin, from the viewpoint of easily removing the oxide film on the surface of the electrode and the solder layer. The upper limit is not particularly limited, but is preferably 40% by mass or less, more preferably 30% by mass or less, from the viewpoint of coatability.
When the flux component is an inorganic acid, a halide, or an organic acid, the flux component in the flux is preferably contained in an amount of 1 to 15 mass%, more preferably 2 to 10 mass%, from the viewpoint of easily removing the surface oxide film of the electrode and the solder layer.
The method of making the solder layer contain the flux is not particularly limited. In order to improve the adhesion between the electrode and the solder layer, it is preferable that flux be present at least on the surface of the solder layer. Examples of the method for producing such a solder layer include: and a method of applying flux to a surface of at least one of the electrode and the solder layer.
The method of making the solder layer contain flux is not particularly limited, and examples thereof include: and a method of applying flux to a surface of at least one of the electrode and the solder layer. When the flux is applied, a liquid containing the flux component and the solvent may be applied, and the solvent may be applied first and then the liquid containing the flux component and the solvent may be applied next. When the electrode has water absorption, it is also preferable to apply a liquid containing the flux component and the solvent after applying the solvent, from the viewpoint that the flux component does not intrude into the electrode and the oxide film on the surface of the electrode can be effectively removed.
Even when flux is applied to the surface of the electrode but not to the surface of the solder layer, the electrode and the solder layer are brought into contact with each other and heat treatment is performed, whereby the solder layer can be made to contain flux. When the amount of flux applied to the surface of the electrode is small, it is preferable to apply flux to the surface of the solder layer in advance.
The method and amount of the flux to be applied are not particularly limited, and manual application using cotton wool or the like, or automatic application using an applicator attached to a bonding apparatus described later, or the like, may be applied.
The electrode prepared as described above is brought into contact with the solder layer, pressed, and then heat-treated, whereby the electrode and the solder layer can be connected.
The pressing pressure when the electrode and the solder in contact with the electrode are heat-treated is usually about 2MPa, but in the present invention, 1.5MPa or less is used to improve the wettability between the electrode and the solder layer. By reducing the pressing pressure when the electrode and the solder layer are heat-treated, the yield reduction caused by the breakage of the silicon substrate during pressing can be prevented.
The heat treatment temperature at the time of contact may be appropriately selected depending on the flux and the solder material, and for example, the temperatures of the electrode and the solder layer may be set to 125 to 350 ℃.
The pressing time may be appropriately selected according to the type of flux, the solder material, and the heat treatment temperature, and may be set to 2 seconds to 120 seconds, for example.
As the heat treatment apparatus, there can be applied: a heat treatment machine using a manual operation such as a hot plate, a hot air blower, a soldering iron, and an oven, or an automatic heat treatment machine using a device such as a pulse heat bonding device, a heat pressure bonding device, and an ultrasonic bonding device.
As a treatment after the heat treatment of the electrode and the solder in contact with the electrode, cleaning for removing the flux may be performed. When a flux containing a large amount of halide and having a fear of corrosion due to the residue is used, it is preferable to carefully remove the halide by ultrasonic cleaning or the like.
< use >
The use of the element of the present invention is not particularly limited, and the element can be used as a solar cell element, an electroluminescent light-emitting element, or the like.
< solar cell element >
In the solar cell device of the present invention, the substrate in the device has an impurity diffusion layer, the electrode is formed on the impurity diffusion layer, and then a solder layer containing flux is formed on the electrode. Thus, a solar cell element having good characteristics can be obtained, and the productivity of the solar cell is excellent.
In the present specification, the solar cell element refers to a solar cell element including a silicon substrate having a pn junction formed thereon and an electrode formed on the silicon substrate. The solar cell is a solar cell in which a tab wire is provided on an electrode of a solar cell element, and a plurality of solar cell elements are connected via the tab wire as necessary.
Specific examples of the solar cell of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.
Fig. 1, 2, and 3 show a cross-sectional view, a schematic view of a light-receiving surface, and a schematic view of a rear surface of a representative solar cell element.
Generally, single crystal Si, polycrystalline Si, or the like is used for the semiconductor substrate 130 of the solar cell element. The semiconductor substrate 130 contains boron or the like, and constitutes a p-type semiconductor. The light receiving surface side is formed with irregularities (texture, not shown) by etching in order to suppress reflection of sunlight. As shown in fig. 1, the light-receiving surface side of the semiconductor substrate 130 is doped with phosphorus or the like, a diffusion layer 131 of an n-type semiconductor is provided at a thickness of the order of submicron, and a pn junction portion is formed at the boundary with the p-type body portion. Further, an antireflection layer 132 made of silicon nitride or the like is provided on the diffusion layer 131 on the light receiving surface side in a thickness of about 100nm by vapor deposition or the like.
Next, the light-receiving surface electrode 133 provided on the light-receiving surface side, and the collector electrode 134 and the output extraction electrode 135 formed on the back surface will be described. The light-receiving surface electrode 133 and the output extraction electrode 135 are formed from the above-described paste composition for electrodes. The collector electrode 134 is formed of an aluminum electrode paste composition containing glass powder. These electrodes are formed by applying the paste composition to a desired pattern by screen printing or the like, drying the applied pattern, and then firing the dried pattern at about 600 to 850 ℃.
At this time, on the light receiving surface side, the glass particles contained in the above-described paste composition for an electrode forming the light receiving surface electrode 133 react with (burn through) the antireflection layer 132, thereby electrically connecting (ohmic contact) the light receiving surface electrode 133 and the diffusion layer 131.
In the present invention, by forming the light-receiving surface electrode 133 using the paste composition for an electrode, the light-receiving surface electrode 133 having a low resistivity can be formed with excellent productivity by suppressing oxidation of copper while containing copper as a conductive metal.
When a solder layer (not shown) containing flux is provided on the outer surface of the light-receiving-surface electrode 133, the adhesion between the light-receiving-surface electrode 133 and the solder layer is improved, and the contact resistance at the interface between the light-receiving-surface electrode 133 and the solder layer is reduced.
On the back surface side, aluminum in the aluminum electrode paste composition forming collector electrode 134 during firing diffuses to the back surface of semiconductor substrate 130 to form electrode component diffusion layer 136, whereby ohmic contact can be obtained between semiconductor substrate 130, collector electrode 134, and output extraction electrode 135.
Fig. 4 is a view showing a back contact type solar cell element which is an example of a solar cell element according to another embodiment of the present invention, fig. 4A is a perspective view showing a light receiving surface and an AA cross-sectional structure, and fig. 4B is a plan view showing a back surface side electrode structure.
As shown in fig. 4A, in a cell wafer 1 including a silicon substrate of a p-type semiconductor, a through hole penetrating both the light receiving surface side and the back surface side is formed by laser drilling, etching, or the like. Further, a texture (not shown) for improving light incidence efficiency is formed on the light receiving surface side. An n-type semiconductor layer 3 by n-type diffusion treatment is formed on the light receiving surface side, and an antireflection film (not shown) is formed on the n-type semiconductor layer 3. These layers are produced by the same steps as those of conventional crystalline Si-type solar cell elements.
Next, the paste composition for an electrode of the present invention is filled into the inside of the through hole formed in advance by a printing method or an ink-jet method, and the paste composition for an electrode of the present invention is printed in a grid pattern on the light-receiving surface side in the same manner, thereby forming a composition layer in which the through hole electrode 4 and the grid electrode 2 for current collection are formed.
Here, the paste used for filling and printing is preferably a paste having a composition most suitable for each process, such as viscosity, and may be filled and printed at once by a paste having the same composition.
On the other hand, a high-concentration doped layer 5 for preventing recombination of carriers is formed on the opposite side (back side) of the light-receiving surface. Here, as the impurity element for forming the high-concentration doped layer 5, boron (B) or aluminum (a1) is used to form p+And (3) a layer. The high-concentration doped layer 5 can be formed by, for example, performing a thermal diffusion treatment using B as a diffusion source in the device manufacturing step before the formation of the antireflection film, or by printing an Al paste on the opposite surface side in the printing step when Al is used.
Then, the paste composition for an electrode is fired at 650 to 850 ℃, filled and printed on the antireflection film formed on the inside of the through hole and the light receiving surface side, and ohmic contact with the lower n-type layer is achieved by the firing effect.
On the opposite surface side, as shown in the plan view of fig. 4B, the paste composition for an electrode of the present invention is printed in stripes on the n-side and p-side, respectively, and fired to form a back electrode 6 and a back electrode 7.
In the present invention, by forming the back electrode 6 and the back electrode 7 using the paste composition for electrodes, the back electrode 6 and the back electrode 7 having low resistivity are formed with excellent productivity by containing copper as a conductive metal and suppressing oxidation of copper. When a solder layer (not shown) containing flux is provided on the outer surfaces of the rear electrodes 6 and 7, the adhesion between the rear electrodes 6 and 7 and the solder layer is improved, and the contact resistance at the interface between the rear electrodes 6 and 7 and the solder layer is reduced.
The electrode paste composition for a solar cell of the present invention is not limited to the above-described applications of the solar cell electrode, and can be suitably used for applications such as electrode wiring and shield wiring of a plasma display, a ceramic capacitor, an antenna circuit, various sensor circuits, and a heat dissipating material of a semiconductor device.
< solar cell >
The solar cell of the present invention includes at least 1 of the solar cell elements, and is configured by disposing a tab wire on an electrode of the solar cell element. Since the solder layer containing flux is provided on the surface of the electrode, the adhesion between the electrode and the solder layer is improved, and the contact resistance at the interface between the electrode and the solder layer is reduced, so that a solar cell having excellent cell performance can be obtained.
The solar cell may be configured by further connecting a plurality of solar cell elements via tab wires as necessary, and further sealing the solar cell elements with a sealing material. The above-mentioned lug wire and sealing member are not particularly limited, and may be appropriately selected from those generally used in the art.
The following shows examples of embodiments included in the present invention.
(1) An element, comprising: a silicon substrate; an electrode provided on the silicon substrate, the electrode being a fired product of a paste composition for an electrode containing phosphorus-containing copper alloy particles, glass particles, a solvent, and a resin; and a solder layer provided on the electrode and containing flux.
(2) The device according to (1), wherein the flux contains at least 1 selected from the group consisting of a halide, an inorganic acid, an organic acid, and rosin.
(3) The element according to the above (2), wherein the halide is at least 1 selected from the group consisting of chloride and bromide.
(4) The element according to the above (2), wherein the inorganic acid contains at least 1 selected from the group consisting of hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid and boric acid.
(5) The element according to the above (2), wherein the organic acid contains a carboxylic acid.
(6) The element according to (5), wherein the carboxylic acid contains at least 1 selected from the group consisting of formic acid, acetic acid and oxalic acid.
(7) The element according to any one of (2) to (6) above, wherein the flux contains 5% by mass or more of rosin.
(8) The device according to any one of (1) to (7) above, wherein the solder layer contains 42 mass% or more of tin.
(9) The element according to any one of (1) to (8) above, wherein the flux comprises: a combination of rosin and an organic acid, a combination of rosin and an inorganic acid, a combination of rosin and a halide, a combination of an inorganic acid and a halide, or a combination of a halide and a halide.
(10) The device according to any one of (1) to (8), wherein the flux contains at least 1 selected from rosin, glycerin, ethylene glycol, and isopropyl alcohol.
(11) The device according to any one of the above (1) to (8), wherein the flux contains at least 1 selected from the group consisting of an inorganic acid, water and butyl carbitol acetate.
(12) The device according to any one of (1) to (8) above, wherein the flux contains at least 1 of a halide, water and terpineol.
(13) The device according to any one of (1) to (8) above, wherein the flux contains at least 1 selected from the group consisting of an organic acid, glycerin, ethylene glycol, and isopropyl alcohol.
(14) The element according to any one of (2) to (13) above, wherein the flux further contains a carboxylic acid ester.
(15) The element according to the above (14), wherein the above carboxylic acid ester is at least 1 selected from the group consisting of ethyl acetate, trimethyl borate, methyl butyrate, methyl salicylate, ethyl formate, ethyl butyrate, ethyl hexanoate, pentyl acetate, isopentyl acetate, pentyl valerate, pentyl butyrate and octyl acetate.
(16) The element according to any one of (1) to (15) above, wherein a content of phosphorus contained in the phosphorus-containing copper alloy particles is 6 mass% or more and 8 mass% or less.
(17) The element according to any one of (1) to (16) above, wherein the weight average molecular weight of the resin is 5000 or more and 500000 or more.
(18) The element according to any one of (1) to (17) above, wherein the paste composition for an electrode further contains silver particles.
(19) The element according to (18), wherein a content of the silver particles in the paste composition for electrodes is 8.4 to 85.5% by mass.
(20) The element according to the above (18) or (19), wherein a relationship between the particle diameter (D50%) of the phosphorus-containing and copper-containing particles and the particle diameter (D50%) of the silver particles is such that a ratio of one particle diameter to the other particle diameter satisfies 1 to 10.
(21) The element according to any one of (18) to (20) above, wherein a content of the phosphorus-containing and copper-containing particles is 9 to 88% by mass, assuming that a total amount of the phosphorus-containing and copper-containing particles and the silver particles is 100% by mass.
(22) The element according to any one of the above (1) to (21), which is used for a solar cell comprising: and a solar cell in which the silicon substrate has an impurity diffusion layer and a pn junction is formed, and the electrode is provided on the impurity diffusion layer.
(23) A solar cell, comprising: the element for a solar cell according to (22) above; and a tab wire connected to the solder layer of the electrode of the element.
(24) A method for manufacturing an element according to any one of the above (1) to (23), comprising: applying the flux to a surface of at least one of the electrode and the solder layer; and a step of bringing the electrode into contact with the solder layer on the surface coated with the flux and performing a heating treatment.
(25) The method for producing a device according to item (24), wherein a pressing pressure at the time of bringing the electrode into contact with the solder layer and performing the heat treatment is 1.5MPa or less.
(26) The method for manufacturing a device according to the above (24) or (25), wherein a solvent is applied before the above flux is applied.
(27) A solder flux, comprising: at least 1 flux component selected from the group consisting of halides, inorganic acids, organic acids, and rosins; at least 1 solvent selected from water, ether acetate solvent, terpene solvent, alcohol solvent, ketone solvent, ether solvent, ester solvent, aprotic polar solvent and glycol monoether solvent; and is applied between an electrode and a solder layer, the electrode containing a fired product of a paste composition for electrodes containing phosphorus-containing copper alloy particles, glass particles, a solvent and a resin.
(28) The flux of (27), wherein the flux components include: a combination of rosin and an organic acid, a combination of rosin and an inorganic acid, a combination of rosin and a halide, a combination of an inorganic acid and a halide, or a combination of a halide and a halide.
(29) The flux according to any one of (27) and (28), wherein the flux component contains rosin, and the solvent contains at least 1 selected from the group consisting of glycerol, ethylene glycol, and isopropyl alcohol.
(30) The flux according to the above (27) or (28), wherein the flux component contains an inorganic acid, and the solvent contains at least 1 selected from the group consisting of water and butyl carbitol acetate.
(31) The device according to (27) or (28), wherein the flux component contains a halide, and the solvent contains at least 1 selected from the group consisting of water and terpineol.
(32) The device according to (27) or (28), wherein the flux component includes an organic acid, and the solvent includes at least 1 selected from the group consisting of glycerin, ethylene glycol, and isopropyl alcohol.
(33) The flux according to any one of (27) to (32) above, further comprising a carboxylic acid ester.
(34) The flux of (33) above, wherein the carboxylate is at least 1 selected from the group consisting of ethyl acetate, trimethyl borate, methyl butyrate, methyl salicylate, ethyl formate, ethyl butyrate, ethyl hexanoate, amyl acetate, isoamyl acetate, amyl valerate, amyl butyrate and octyl acetate.
In addition, the entire disclosure in japanese patent application 2011-.
All documents, patent applications, and technical standards described in the present specification are incorporated by reference into the present specification to the same extent as if each document, patent application, and technical standard was specifically and individually described.
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(s)" and "%" are based on mass.
< example 1>
(a) Preparation of paste composition for electrode
Phosphorus-containing copper alloy particles containing 7 mass% of phosphorus were prepared according to a conventional method, and were melted and powdered by a water atomization method, and then dried and classified. The classified powders were mixed, and subjected to deoxidation and dehydration treatment to prepare phosphorus-containing copper alloy particles (hereinafter, sometimes abbreviated as "Cu 7P") containing 7 mass% of phosphorus. The particle diameter (D50%) of the phosphorus-containing copper alloy particles was 5 μm.
Preparation of a silica-containing (SiO)2)3 parts of lead oxide (PbO)60 parts of boron oxide (B)2O3)18 portions of bismuth oxide (Bi)2O3)5 parts of aluminum oxide (Al)2O3)5 parts and 9 parts of zinc oxide (ZnO) (hereinafter sometimes abbreviated as "G1"). The softening point of the glass G1 thus obtained was 420 ℃ and the crystallization temperature was more than 600 ℃.
Using the glass G1 thus obtained, glass particles having a particle diameter (D50%) of 1.1 μm were obtained.
85.1 parts of the phosphorus-containing copper alloy particles Cu7P obtained above, 1.7 parts of glass particles G1, and 13.2 parts of a terpineol (isomeric mixture) solution containing 3 mass% of ethyl cellulose (EC, weight average molecular weight 190000) were mixed and stirred in an agate mortar for 20 minutes to prepare a paste composition for an electrode Cu7PG 1.
(b) Production of solar cell element
A p-type semiconductor substrate having a thickness of 190 μm and an n-type semiconductor layer, a texture, and an antireflection film (silicon nitride film) formed on a light receiving surface thereof was prepared and cut into a size of 125mm × 125 mm. On the light-receiving surface thereof, a paste composition for a silver electrode (conductor paste Solamet159A, manufactured by dupont) was printed by screen printing so as to form an electrode pattern as shown in fig. 2. The electrode pattern was composed of finger lines 150 μm wide and bus bars 1.1mm wide, and the printing conditions (screen mesh, printing speed, and impression) were appropriately adjusted so that the thickness after firing became about 5 μm. This was put into an oven heated to 150 ℃ and left for 15 minutes, and the solvent was removed by evaporation.
Next, similarly, an aluminum electrode Paste (solarcelsaste (a1) perbsf Al Paste) was printed on the entire rear surface except for the portion where the output extraction electrode was formed, as shown in fig. 3, by screen printing. Printing conditions were appropriately adjusted so that the fired film thickness became 40 μm. This was put into an oven heated to 150 ℃ and left for 15 minutes, and the solvent was removed by evaporation.
Next, a heat treatment (firing) was performed at 850 ℃ for 2 seconds in an infrared high-speed heating furnace in an atmospheric environment, and a light-receiving surface electrode and a current collecting electrode were obtained.
Next, the obtained paste composition for an electrode Cu7PG1 was printed on the back surface by a screen printing method so as to form an electrode pattern shown in the output extraction electrode of fig. 3. The electrode pattern was composed of busbars 4mm wide, and printing conditions (screen mesh, printing speed, and impression) were appropriately adjusted so that the thickness after firing was 15 μm. This was put into an oven heated to 150 ℃ and left for 15 minutes, and the solvent was removed by evaporation.
Next, heat treatment (firing) was performed in an infrared high-speed heating furnace at 600 ℃ for 10 seconds in an atmospheric environment, and an output extraction electrode was obtained.
Next, an appropriate amount of a hydrochloric acid aqueous solution (hydrochloric acid concentration 2%) containing 5% of zinc chloride and 5% of ammonium chloride was applied to the output extraction electrode obtained as described above as a flux by a brush, and a copper wire (generally referred to as an ear wire) solder-coated with solder sn96.5ag3cu0.5 (hereinafter, the solder is denoted by a jis z3282 symbol) was placed thereon. The flux is not particularly applied to the solder, but is wetted by the flux when placed on the output extraction electrode.
Next, the semiconductor substrate with the solder-coated tab wire placed thereon was placed on a hot plate and heated to 250 ℃. The pressing load of the lug wire was adjusted to about 1.0MPa in terms of unit area.
Then, the solar cell element 1 on which the electrode connected to the solder is formed is manufactured by cooling.
< example 2>
A solar cell element 2 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 1 except that in example 1, the flux was changed from an aqueous hydrochloric acid solution containing 5% of zinc chloride and 5% of ammonium chloride to butyl carbitol acetate containing 10% of hydrobromic acid (hereinafter, sometimes abbreviated as "BCA").
< example 3>
A solar cell element 3 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 1, except that in example 1, the aqueous solution of hydrochloric acid containing 5% of zinc chloride and 5% of ammonium chloride was changed to the aqueous solution containing 5% of hydrochloric acid as a flux.
< example 4>
A solar cell element 4 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 1, except that in example 1, the aqueous solution of hydrochloric acid containing 5% of zinc chloride and 5% of ammonium chloride was changed to an aqueous solution containing 5% of zinc chloride and 5% of hydrochloric acid as a flux.
< example 5>
A solar cell element 5 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 1, except that in example 1, the flux was changed from a hydrochloric acid aqueous solution containing 5% of zinc chloride and 5% of ammonium chloride to terpineol containing 5% of zinc chloride and 2% of ammonium chloride.
< example 6>
A solar cell element 6 on which an electrode to be connected to a solder was formed was produced in the same manner as in example 1 except that in example 1, a hydrochloric acid aqueous solution containing 5% of zinc chloride and 5% of ammonium chloride was changed to isopropyl alcohol (hereinafter, sometimes abbreviated as IPA) containing 3% of oxalic acid and 6% of a phenol resin as a flux.
< example 7>
A solar cell element 7 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 1, except that in example 1, the amount of the flux was changed from the aqueous hydrochloric acid solution containing 5% of zinc chloride and 5% of ammonium chloride to glycerin containing 2% of acetic acid.
< example 8>
A solar cell element 8 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 1, except that in example 1, the amount of the aqueous hydrochloric acid solution containing 5% of zinc chloride and 5% of ammonium chloride was changed to IPA containing 30% of rosin and 5% of ethyl acetate as a flux.
< example 9>
In example 8, a solar cell element 9 on which a desired electrode to be connected to solder was formed was produced in the same manner as in example 8 except that IPA containing 30% of rosin and 5% of ethyl acetate was changed to IPA containing 12% of rosin and 3% of oxalic acid as a flux.
< example 10>
In example 8, a solar cell element 10 on which a desired electrode to be connected to solder was formed was produced in the same manner as in example 8 except that IPA containing 30% of rosin and 5% of ethyl acetate was changed to ethylene glycol containing 25% of rosin and 1% of formic acid as a flux.
< example 11 >
In example 8, a solar cell element 11 on which a desired electrode to be connected to solder was formed was produced in the same manner as in example 8 except that IPA containing 30% of rosin and 5% of ethyl acetate was changed to IPA containing 20% of rosin and 2% of acetic acid as a flux.
< example 12 >
A solar cell element 12 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 1 except that in example 1, a glycerin solution (hydrochloric acid concentration 2%) containing hydrochloric acid of 5% zinc chloride and 2% ammonium chloride was used as a flux instead of a hydrochloric acid aqueous solution of 5% zinc chloride and 5% ammonium chloride.
< example 13 >
In example 11, a solar cell element 13 on which a desired electrode to be connected to solder was formed was produced in the same manner as in example 11 except that the heat treatment temperature of the paste composition for an electrode Cu7PG1 was changed from 600 ℃ to 550 ℃ and IPA containing 20% of rosin and 2% of acetic acid was changed to glycerin containing 20% of rosin and 2% of acetic acid as a flux.
< example 14 >
In example 13, a solar cell element 14 on which a desired electrode to be connected to solder was formed was produced in the same manner as in example 13 except that the heat treatment temperature of the paste for an electrode and the composition Cu7PG1 was changed from 550 ℃ to 650 ℃.
< example 15 >
In example 13, a solar cell element 15 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 13 except that phosphorus-containing copper alloy particles (Cu6P) containing 6 mass% of phosphorus were used instead of the phosphorus-containing copper alloy particles Cu7PG1 containing 7 mass% of phosphorus, and the heat treatment temperature of the paste composition for an electrode was changed from 550 ℃ to 580 ℃.
< example 16>
In example 13, a solar cell element 16 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 13 except that phosphorus-containing copper alloy particles (Cu8P) containing 8 mass% of phosphorus were used instead of the phosphorus-containing copper alloy particles Cu7PG1 containing 7 mass% of phosphorus, and the heat treatment temperature of the paste for an electrode and the composition was changed from 550 ℃ to 620 ℃.
< example 17>
In example 13, a solar cell element 17 on which a desired electrode to be connected with solder was formed was produced in the same manner as in example 13 except that the paste composition for electrode Cu7PG2 using glass particles (G2) adjusted as described below was used in place of the glass particles G1 and the heat treatment temperature of the paste composition for electrode and the composition was changed from 550 ℃ to 600 ℃.
The glass particles G2 contain vanadium oxide (V)2O5)45 parts of phosphorus oxide (P)2O5)24.2 parts, 20.8 parts of barium oxide (BaO), and antimony oxide (Sb)2O3)5 parts of tungsten oxide (WO)3)5 parts, the particle diameter (D50%) is 1.7 μm. The glass has a softening point of 492 ℃ and a crystallization temperature of 600 ℃ or higher.
< example 18>
In example 17, a solar cell element 18 on which a desired electrode to be connected with solder was formed was produced in the same manner as in example 17 except that the paste composition for electrode Cu7PG11 in which glass particles G2 were replaced with glass particles (G11) adjusted as described below was used in example 17.
The glass particles G11 contain silicon dioxide (SiO)2)3 parts of lead oxide (PbO)60 parts of boron oxide (B)2O3)18 portions of bismuth oxide (Bi)2O3)5 parts of alumina (A1)2O3)5 parts of zinc oxide (ZnO) and 9 parts of zinc oxide (ZnO), wherein the particle size (D50%) is 1.7 mu m. The glass has a softening point of 420 ℃ and a crystallization temperature of 600 ℃ or higher.
< example 19>
A solar cell element 19 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 13, except that the heat treatment temperature of the paste composition for an electrode was changed from 550 ℃ to 600 ℃ in example 13.
< example 20>
A solar cell element 20 on which a desired electrode to be connected to solder was formed was produced in the same manner as in example 19, except that the temperature of the electrode in the flux application was changed from room temperature to 150 ℃.
< example 21>
In example 19, a solar cell element 21 on which an electrode to be connected to solder was formed as desired was produced in the same manner as in example 19 except that only glycerin was first applied and then glycerin containing 20 parts of rosin and 2 parts of acetic acid was applied when the flux was applied.
< example 22>
In example 19, a solar cell element 22 on which an electrode to be connected to solder was formed was produced in the same manner as in example 19 except that the semiconductor substrate on which the solder-coated tab wire was placed on a hot plate and heated to 250 ℃ with a pressing load applied to the tab wire, and a constant temperature treatment time of 10 minutes was added at 150 ℃.
< example 23>
In example 19, a solar cell element 23 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 19 except that the solder used for coating the copper wire was changed from sn96.5ag3cu0.5 to Sn95Ag 5.
< example 24>
In example 19, a solar cell element 24 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 19 except that the solder used for coating the copper wire was changed from sn96.5ag3cu0.5 to Sn95Sb 5.
< example 25>
In example 19, a solar cell element 25 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 19 except that the solder used for coating the copper wire was changed from sn96.5ag3cu0.5 to Sn97Cu 3.
< example 26>
In example 19, a solar cell element 26 on which a desired electrode to be connected to a solder was formed was produced in the same manner as in example 19 except that the solder used for coating the copper wire was changed from sn96.5ag3cu0.5 to Bi58Sn 42.
< example 27>
A solar cell element 27 on which a desired electrode to be connected to a solder was formed was produced In the same manner as In example 19, except that In example 19, the solder used for coating the copper wire was changed from sn96.5ag3cu0.5 to In52Sn 48.
< example 28>
In example 2, a solar cell element 28 on which a desired electrode connected to solder was formed was produced in the same manner as in example 2 except that the solder used for coating the copper wire was changed from sn96.5ag3cu0.5 to Sn63Pb 37.
< example 29>
In example 2, a solar cell element 29 on which a desired electrode connected to solder was formed was produced in the same manner as in example 2 except that the solder used for coating the copper wire was changed from sn96.5ag3cu0.5 to Sn50Pb 50.
< example 30>
In example 2, a solar cell element 30 on which a desired electrode to be connected to solder was formed was produced in the same manner as in example 2 except that the solder used for coating the copper wire was changed from sn96.5ag3cu0.5 to Sn62Pb36Ag 2.
< comparative example 1>
In example 1, a solar cell element C1 was produced in the same manner as in example 1, except that the composition for forming the output extraction electrode 135 was changed from the composition containing the phosphorus-containing copper alloy particles Cu7P to silver particles (Ag), and the hydrochloric acid aqueous solution containing 5 parts of zinc chloride and 5 parts of ammonium chloride was changed from IPA containing 20 parts of rosin as a flux, and the heat treatment temperature of the paste composition for electrodes was changed from 600 ℃ to 800 ℃.
< comparative example 2>
A solar cell element C2 was produced in the same manner as in example 1, except that the aqueous hydrochloric acid solution containing 5 parts of zinc chloride and 5 parts of ammonium chloride was changed to glycerin as the flux in example 1.
[ Table 1]
< evaluation >
The solar cell elements thus produced were evaluated by combining WXS-155S-10, manufactured by Wacom electric corporation, as a simulated sunlight, and a measuring apparatus I-V CURVE TRACER MP-160 (manufactured by EKO INSTRUMENT) as a current-voltage (I-V) evaluation measuring INSTRUMENT. Table 2 shows the measured values of the solar cell as relative values with the measured value of comparative example 1C being 100.0. Furthermore, Eff (conversion efficiency), FF (fill factor), Voc (open circuit voltage) and Jsc (short circuit current) which are the power generation performance of the solar cell were measured according to JIS-C-8912, JIS-C-8913 and JIS-C-8914, respectively.
In comparative example 2, the output extraction electrode could not be connected to the tab line, and therefore, the evaluation was impossible.
[ Table 2]
The performance of the solar cell devices fabricated in examples 1 to 30 was substantially equal to or greater than the performance of the solar cell device fabricated in comparative example 1.
< example 31>
Using the paste composition for an electrode Cu7PG1 obtained above, a solar cell element 31 having a structure shown in fig. 4A and 4B was produced in the same manner as in example 1.
The obtained solar cell element was evaluated in the same manner as described above, and as a result, it was found that the solar cell element exhibited favorable characteristics as described above.
Description of the reference numerals
A battery wafer comprising a p-type silicon substrate
Grid electrode for current collection
N-type semiconductor layer
A via electrode
A high concentration doped layer
Back electrode
Back electrode
130
A diffusion layer
132
Light receiving surface electrode
134.. collector electrode
135
136. electrode composition diffusion layer
Claims (10)
1. An element, comprising:
a silicon substrate;
an electrode provided on the silicon substrate, the electrode being a fired product of a paste composition for electrodes, the paste composition containing phosphorus-containing copper alloy particles, glass particles, a solvent, and a resin; and
a solder layer disposed on the electrode and containing flux.
2. The component of claim 1, wherein the flux comprises at least 1 selected from the group consisting of halides, inorganic acids, organic acids, and rosins.
3. The element according to claim 2, wherein the halide is at least 1 selected from the group consisting of chloride and bromide.
4. The element according to claim 2, wherein the inorganic acid comprises at least 1 selected from hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, and boric acid.
5. The element of claim 2 wherein the organic acid comprises a carboxylic acid.
6. The element of claim 5, wherein the carboxylic acid comprises at least 1 selected from formic acid, acetic acid, and oxalic acid.
7. The element according to any one of claims 2 to 6, wherein the flux contains 5 mass% or more of rosin.
8. The element according to any one of claims 1 to 7, wherein the solder layer contains 42 mass% or more of tin.
9. The element according to any one of claims 1 to 8, which is used for a solar cell in which the silicon substrate has an impurity diffusion layer and forms a pn junction, and the electrode is provided on the impurity diffusion layer.
10. A solar cell, comprising:
the element for a solar cell according to claim 9; and
a pole lug connected to the solder layer of the electrode of the component.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2011-162598 | 2011-07-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| HK1197847A true HK1197847A (en) | 2015-02-18 |
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