JP6084270B1 - Conductive composition - Google Patents

Abstract

An object of the present invention is to provide a conductive composition capable of forming a high ohmic solar cell by forming an electrode capable of obtaining a good ohmic contact with LDE, for example. The present invention provides a conductive composition for forming an electrode of a solar cell. The conductive composition includes conductive powder, glass frit, silicone resin, an organic binder, and a dispersion medium. Here, the glass frit has a PbO component ratio of 2 mol% or more and 60 mol% or less when converted to oxide. Moreover, a silicone resin is contained in the ratio of 0.005 mass% or more and 0.9 mass% or less with respect to 100 mass% of electroconductive powder. [Selection] Figure 1

Description

  The present invention relates to a conductive composition. More particularly, the present invention relates to a conductive composition that can be used to form a solar cell electrode.

  From the viewpoint of increasing environmental awareness and energy saving in recent years, solar cells are rapidly spreading. Along with this, there is a demand for solar cells with good photoelectric conversion efficiency and high output. As a measure for realizing this requirement, in a solar cell, a passivation film that suppresses recombination and an antireflection film that increases light reception efficiency are provided, and power generated at a pn junction in the substrate is extracted from the electrode with high efficiency. It has been tried.

In manufacturing this solar cell, typically, a phosphorus-containing solution is first applied to the entire light-receiving surface of a silicon substrate to construct an n-Si layer (hereinafter also referred to as an n ⁺ layer) on the substrate surface. Thereafter, for example, an antireflection film is formed as necessary. Then, a conductive composition for forming an electrode is supplied in a desired electrode pattern on the antireflection film and fired. The conductive composition for forming an electrode typically includes a conductive powder, a glass frit, and an organic vehicle. During firing, the glass frit contained in the conductive composition reacts with the antireflection film, and the constituent components of the antireflection film are taken into the glass. As a result, the conductive powder passes through the antireflection film (fire through), and electrical connection (ohmic contact) with the n ⁺ layer of the silicon substrate is realized. As a prior art regarding the conductive composition for electrode formation of such a solar cell, patent document 1-2 is mentioned, for example.

JP 2010-087251 A JP 2012-023095 A JP 2012-508812 A

Here, it is known that the surface recombination speed is reduced by thinning the n ⁺ layer of the silicon substrate, so that the open circuit voltage (Voc) can be improved and the efficiency can be improved. However, in a substrate having a thin n ⁺ layer (Lightly Doped Emitter; LDE), sheet resistance is increased, and ohmic contact with the light-receiving surface electrode by fire-through is realized in the thin n ⁺ layer. There was a problem that was difficult. For this reason, there is a trade-off that the series resistance increases and the output characteristics (for example, fill factor (FF)) are likely to deteriorate.

  The present invention has been made in view of such a situation, and its main object is to form an electrode that can provide a good ohmic contact with, for example, LDE, and to improve the open circuit voltage and the fill factor. It is providing the electroconductive composition which can implement | achieve a battery. Another object of the present invention is to provide a solar cell with improved functions or performance realized by the use of this conductive composition.

The present inventors have so far added a silicone resin (also referred to simply as silicone) to a conductive composition for suitably forming a solar cell electrode, and the amount of SiO ₂ component in the composition. Has been proposed to stably form fine and high aspect ratio electrodes (for example, Japanese Patent Application No. 2015-001855). Realization of an electrode having a high aspect ratio contributes to the realization of a solar cell having a good output characteristic by reducing the line resistance of the light-receiving surface electrode. However, for the conductive composition containing such a silicone resin, apart from the viewpoint of improving the performance of the solar cell due to the shape of the electrode to be formed, from the electrochemical aspect such as realization of better ohmic contact There was room for improvement. As a result of further diligent research by the present inventors, it is possible to form a good ohmic contact with, for example, LDE by suitably combining the composition of the glass frit and the amount of the silicone resin. It has been found that a conductive composition that can be improved can be realized. The present invention has been completed based on such findings.

  That is, the conductive composition which can be used suitably in order to form the electrode of a solar cell is provided by the technique disclosed here. This conductive composition includes a conductive powder, a leaded glass frit, a silicone resin, an organic binder, and a dispersion medium. In the leaded glass frit, the ratio of the PbO component when converted to an oxide is 2 mol% or more and 60 mol% or less. Moreover, the said silicone resin is contained in the ratio of 0.005 mass% or more and 0.9 mass% or less with respect to 100 mass% of said electroconductive powders. Thereby, as described above, for example, a conductive composition capable of forming a good ohmic contact with LDE is provided. Therefore, for example, a high open circuit voltage (Voc) can be realized while maintaining a good fill factor (FF).

  In a preferred embodiment of the conductive composition disclosed herein, the silicone resin has a weight average molecular weight of 1,000 to 150,000. With such a configuration, electrical characteristics such as line resistance of the electrode can be further enhanced as compared with the case where no silicone resin is added.

  In a preferred embodiment of the electrically conductive composition disclosed herein, the silicone resin contains at least one of polydimethylsiloxane and polyether-modified siloxane. With such a configuration, an electrode having good adhesion to the substrate can be formed.

  In a preferred embodiment of the conductive composition disclosed herein, the metal species constituting the conductive powder is any one or two selected from the group consisting of nickel, platinum, palladium, silver, copper, and aluminum. It is characterized by containing more than seed elements. With such a configuration, an electrode having excellent conductivity can be configured.

The conductive composition of the present invention can realize good ohmic contact even with a thin solar cell substrate having an n ⁺ layer, for example. Thereby, surface recombination is suppressed and a high open circuit voltage is realized. In addition, it is possible to reduce the resistance element loss and realize a high fill factor. Therefore, a highly efficient and high output solar cell can be realized.

It is sectional drawing which shows an example of the structure of a solar cell typically. It is a top view which shows typically the pattern of the electrode formed in the light-receiving surface of a solar cell. It is the graph which showed the relationship between the silicone content of the electrically conductive composition concerning one Embodiment, and the open circuit voltage (Voc) of a solar cell. It is the graph which showed the relationship between the silicone content of the electrically conductive composition concerning one Embodiment, and the fill factor (FF) of a solar cell.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that technical matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention are the technical content taught by the present specification and those of ordinary skill in the art. Based on common technical common sense. In the present specification, the notation “A to B” indicating a range means A or more and B or less.

  The conductive composition disclosed herein can typically form an electrode of a solar cell (solar cell element) by firing. That is, the fired product of the conductive composition can constitute a solar cell electrode. The conductive composition is essentially the same as the conventional conductive composition of this type, and includes conductive powder, leaded glass frit, and an organic vehicle component for dispersing these components (described later). Is a mixture of an organic binder and a dispersant), and further includes a silicone resin as an essential component. Hereinafter, each of these components will be described.

As the conductive powder that is the main component of the solid content of the paste, it is possible to consider powders made of various metals or their alloys having desired conductivity and other physical properties according to the application. Examples of the material constituting the conductive powder include gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium ( Ir), metals such as osmium (Os), nickel (Ni) and aluminum (Al) and their alloys, carbonaceous materials such as carbon black, LaSrCoFeO ₃ -based oxides (for example, LaSrCoFeO ₃ ), LaMnO ₃ -based oxides ( Examples thereof include conductive ceramics represented by transition metal perovskite oxides represented by LaSrGaMgO ₃ ), LaFeO ₃ -based oxides (eg LaSrFeO ₃ ), LaCoO ₃ -based oxides (eg LaSrCoO ₃ ), and the like. Among these, particularly preferable are those composed of a simple substance of a noble metal such as platinum, palladium, silver, and alloys thereof (for example, Ag—Pd alloy, Pt—Pd alloy, etc.), nickel, copper, aluminum, and alloys thereof. Can be cited as a material constituting the conductive powder. From the viewpoint of relatively low cost and high electrical conductivity, a powder made of silver and its alloy (hereinafter also simply referred to as “Ag powder”) is particularly preferably used. Hereinafter, although the case where Ag powder is used as a conductive powder is described as an example for the conductive composition of the present invention, the present invention is not limited thereto.

There is no restriction | limiting in particular about the particle size of electroconductive powder, The thing of the various particle size according to a use can be used. Typically, those having an average particle size of 5 μm or less are suitable, and those having an average particle size of 3 μm or less (typically 1 μm to 3 μm, for example, 1.5 μm to 2.5 μm) are preferably used. As the average particle size of the conductive powder, an integrated 50% particle size (D ₅₀ ) in a volume-based particle size distribution measured by a particle size distribution measuring device based on a laser diffraction / scattering method can be adopted. The average particle diameter of the conductive powder in this specification employs a value measured using a laser diffraction / scattering particle size distribution measuring device (LA-920, manufactured by Horiba, Ltd.).

The shape of the particles constituting the conductive powder is not particularly limited. Typically, a spherical shape, a flake shape (flake shape), a conical shape, a rod shape, or the like can be preferably used. Spherical or scaly particles are preferably used for reasons such as easy formation of a fine light-receiving surface electrode with good filling properties. As the conductive powder to be used, for example, a powder having a sharp (narrow) particle size distribution is preferable. Specifically, a conductive powder having a sharp particle size distribution that does not substantially contain particles having a particle diameter of 10 μm or more is preferably used. As this index, the ratio (D ₁₀ ) of the particle size (D ₁₀ ) when the cumulative volume is 10% and the particle size (D ₉₀ ) when the cumulative volume is 90% from the small particle size side in the particle size distribution based on the laser diffraction / scattering method (D ₉₀ ) ₁₀ / _D90 ) can be employed. When all the particle sizes constituting the powder are equal, the value of D ₁₀ / D ₉₀ is 1, and conversely, the value of D ₁₀ / D ₉₀ approaches 0 as the particle size distribution becomes wider. It is preferable to use a powder having a relatively narrow particle size distribution such that the value of D ₁₀ / D ₉₀ is 0.2 or more (for example, 0.2 or more and 0.5 or less).

In another aspect, the conductive powder can be used by mixing two particle groups having different average particle diameters. In this case, for example, the average particle diameter (D ₅₀ ) of the first particle group is in the range of 1.5 μm to 2.5 μm (for example, 2 μm), and the average particle diameter (D ₅₀ ) of the second particle group is 2 μm to The range can be 3 μm (for example, 2.5 μm). At this time, the particle size distribution of each particle group is preferably sharp as described above. Then, for example, mixing is performed so that the first particle group has a ratio of 90% by volume and the second particle group has a ratio of 10% by volume. Thereby, the electroconductive powder with favorable filling property can be prepared.
The conductive composition using the conductive powder having the average particle diameter and the particle shape as described above has a good filling property of the conductive powder and can form a dense electrode. This is advantageous in forming a fine electrode pattern with high shape accuracy.

  In addition, electroconductive powder is not specifically limited by the manufacturing method etc. For example, conductive powder produced by a known wet reduction method, gas phase reaction method, gas reduction method or the like can be classified and used as necessary. Such classification can be performed using, for example, a classification device using a centrifugal separation method.

  Leaded glass frit is a component that can function as an inorganic binder of the above conductive powder, and the bonding between the conductive particles constituting the conductive powder and between the conductive particles and the substrate (object on which the electrode is formed). It works to improve. In addition, when this conductive composition is used for, for example, the formation of a light-receiving surface electrode of a solar cell, the conductive composition penetrates an antireflection film as a lower layer during firing due to the presence of the leaded glass frit. And good adhesion and electrical contact with the substrate can be realized.

Such a leaded glass frit is preferably adjusted to a size equal to or less than that of the conductive powder. The average particle diameter of the leaded glass frit is, for example, preferably 4 μm or less, more preferably about 3 μm or less. The lower limit of the average particle diameter of the leaded glass frit is not particularly limited, but can typically be 0.5 μm or more, and more preferably 1 μm or more. The average particle size of the glass frit in this specification is the cumulative 50% particle size (D ₅₀ ) in the volume-based particle size distribution measured by a particle size distribution measuring apparatus based on the laser diffraction / scattering method, as in the case of the conductive powder. Can be adopted.

  In addition, about the leaded glass frit in this embodiment, what is called leaded glass containing Pb component can be used. By including the Pb component in the glass frit, the open circuit voltage can be increased without reducing the fill factor of the manufactured solar cell, even when the conductive composition includes a silicone resin described later. In addition, in this specification, leaded glass means that the ratio of PbO when converted to oxide is 2 mol% or more (for example, more than 2 mol%). PbO is preferably 5 mol% or more, and more preferably 10 mol% or more. On the other hand, if the amount of PbO in the leaded glass frit is excessively increased, the fill factor rapidly decreases as in the case where PbO is not included. Therefore, the ratio of PbO is less than 70 mol%, for example, 60 mol% or less. The proportion of PbO is more preferably 55 mol% or less, and particularly preferably 50 mol% or less. Details of the contribution of PbO in the leaded glass frit are not clear, but the content of other glass constituent elements is not so much affected, so the correlation between the silicone resin and the leaded glass is high. It is guessed.

  There is no restriction | limiting in particular about the ratio of components other than PbO contained in a leaded glass frit, Glass of various compositions can be used. As an approximate glass composition, for example, a so-called lead glass, a lead lithium glass, a zinc glass, a borate glass, a borosilicate glass, an alkali system, which is referred to as a name commonly expressed by those skilled in the art. It may be glass, tellurium-based glass, lead-tellurium-based glass, glass containing barium oxide, bismuth oxide, or the like. Needless to say, these glasses can contain Pb (however, the amount of Pb is limited as described above) and other arbitrary elements in addition to the main glass constituent elements appearing in the above designation. Examples of such elements include Si, Zn, Ba, Bi, B, Al, Li, Na, K, Rb, Te, Ag, Zr, Sn, Ti, W, Cs, Ge, Ga, In, Ni, and Ca. , Cu, Mg, Sr, Se, Mo, Y, As, La, Nd, Co, Pr, Gd, Sm, Dy, Eu, Ho, Yb, Lu, Ta, V, Fe, Hf, Cr, Cd, Sb , F, Mn, P, Ce and Nb. The leaded glass frit can contain any one or more of these elements in any combination and proportion. Such a leaded glass frit may be, for example, a crystallized glass partially containing crystals in addition to a general amorphous glass. In addition, as long as the PbO component as a whole is adjusted as described above, the leaded glass frit may be a single type of leaded glass frit, or two or more types of leaded glass frit. You may mix and use a frit.

The softening point of the glass constituting the leaded glass frit is not particularly limited, but is preferably about 250 ° C. or higher and 600 ° C. or lower (eg, 300 ° C. or higher and 500 ° C. or lower). Specific examples of the glass whose softening point can be adjusted in the range of 250 ° C. or higher and 600 ° C. or lower include glass containing a combination of the following elements. Pb-B-Si glass, Pb-B-Si-Ti glass, Pb-B-Si-Ti-Bi glass, Pb-B-Si-Al-Zn-P glass, Pb-B-Si- Al-Li-Ti-Zn glass, Pb-B-Si-Al-Li-Ti-P-Te glass, Pb-Si-Li-Bi-Te glass, Pb-Si-Li-Bi-Te- W glass, Pb—Si—Al—Li—Zn—Te glass, Pb—Li—Bi—Te glass, Pb—B glass, Pb—B—Mo glass, Pb—Te glass, Pb— Te-Li glass, Pb-Te-Bi-Li-Zn glass, Pb-Te-Bi-Li-W glass, Pb-Te-Bi-Li-Mg glass, Pb-Te-Bi-Li- Zn-W-based glass, Pb-Te-Bi-Li-Zn-Mg-based gas Pb—Te—Bi—Li—W—Mg glass, Pb—Te—Bi—Li—Zn—W—Mg glass, Pb—Te—Li—Zn glass, B—Si—Zn—Pb glass Glass, B-Si-Zn-Pb-Cu glass, B-Si-Zn-Pb-Sn glass, B-Si-Zn-Pb-Ta glass, B-Si-Zn-Pb-Ta-Ce glass Glass, B-Si-Al-Pb glass, B-Si-Zn-Al-Pb glass, Si-Pb-Li glass, Si-Al-Mg-Pb glass, Si-Li-Zn-Bi- Mg—W—Te—Pb glass, Si—Li—Zn—Bi—Mg—Mo—Te—Pb glass, Si—Li—Zn—Bi—Mg—Cr—Te—Pb glass, Pb—Ge— Zn-Li glass, B-Zn-Pb glass, Pb-P-Z Glass, Pb—P—Al—Zn glass, Pb—P—Si—Al—Zn glass, Pb—P—B—Al—Si—Li glass, Pb—P—B—Al—Mg—F -K-based glass, Pb-V-P based glass, Pb-V-P-Ba -Zn -based glass, Pb-V-P-Na -Zn -based _{glass, Pb-AgI-Ag 2 O} -B-P based glass , Pb—Zn—B—Si—Li-based glass, and the like. The above glass contains at least a plurality of elements connected by hyphens (−), and the total of oxides of the elements based on the composition (oxide conversion composition) when these elements are converted into oxides. Means 70% by mol or more (typically 80% or more, more preferably 90% or more) of the whole.

The following can be mentioned as an example as a more concrete composition of a leaded glass frit.
[Li-containing lead-based glass]
_{0.6~18mol% Li 2 O-20~65mol%} PbO-1~18mol% B 2 O 3 -20~65mol% SiO 2
[Te-containing lead-based glass]
_{1~25mol% PbO-25~80mol% TeO 2} -0.1~30mol% ZnO
When a conductive composition containing a leaded glass frit having such a softening point is used, for example, when forming a light-receiving surface electrode of a solar cell, it exhibits good fire-through characteristics and forms a high-performance electrode. It is preferable to contribute to the above.

Silicone resin is an essential constituent component contained in the conductive composition disclosed herein. By containing this silicone resin, this conductive composition acts on the above lead-containing glass frit at the time of firing, improves fire-through characteristics, suppresses excessive erosion of the Si substrate, and provides good contact. It is thought that it can be formed. Moreover, the silicone resin can maintain the shape of the coating film (unfired electrode) of the conductive composition formed on the Si substrate, for example, from printing to firing stably, and has a finer and higher aspect ratio. An electrode can be formed stably. Moreover, the silicone resin may generate SiO ₂ component in the electrode by firing. This SiO ₂ component is considered to contribute to improving the stability of the system and the binding property between the electrode and the substrate without directly increasing the softening point of the leaded glass frit.
Patent Document 3 discloses that an aluminum ink composition for forming a back surface aluminum electrode of a solar cell contains a silicone-containing inorganic polymer. However, the aluminum electrode is an electrode formed on almost the entire back surface of the silicon substrate, and the function of the silicone-containing inorganic polymer in such a composition is greatly different in that the function required for the light receiving surface electrode is not provided. I can say that.

As this silicone resin, an organic compound containing silicon (Si) can be used without any particular limitation. For example, a high molecular organic compound having a main skeleton based on a siloxane bond (Si—O—Si) is preferably used. it can. Examples of the siloxane compound (polymer) that forms the main skeleton portion include, for example, the carbon number of the alkyl group represented by the general formula: HO [—Si (CH ₃ ) ₂ O—] _n H (n = 1 to 20); It may be a polymer formed by polymerizing 1 to 20 polyalkylsiloxanes or siloxane units and a different silicon-containing monomer. Specific examples include polydialkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane, polyalkylarylsiloxanes, poly (dimethylsiloxane-methylsiloxane), and the like. A particularly suitable polymer constituting the main skeleton can be, for example, polydimethylsiloxane. Moreover, as a silicone resin, the linear silicone which introduce | transduced the alkyl group, the phenyl group, etc. into the dangling hand (side chain, the terminal, or both) in a main skeleton may be sufficient, for example. Alternatively, the silicone resin is a linear modified silicone in which other substituents such as a polyether group, an epoxy group, an amine group, a carboxyl group, an aralkyl group, and a hydroxyl group are introduced into the side chain, terminal, or both of the main skeleton. Alternatively, a linear block copolymer in which polyether is alternately bonded to silicone may be used. For example, polyether-modified siloxane (polyether-modified silicone) can be preferably used as the silicone resin.

  Such a silicone resin is preferable because an electrode having a high aspect ratio can be formed as the weight average molecular weight (hereinafter sometimes simply referred to as “Mw”) increases. However, if Mw exceeds about 150,000, defects such as disconnection of the obtained electrode are caused and resistance is increased, which is not preferable. From such a viewpoint, the Mw of the silicone resin can be, for example, 150,000 or less, preferably 130,000 or less, more preferably 110,000 or less, and particularly preferably 90,000 or less. preferable. The lower limit of Mw is not particularly limited, but can be, for example, 1,000 or more, preferably 3,000 or more, more preferably 5,000 or more, and particularly 10,000 or more, for example 20,000 or more. preferable.

  As the organic vehicle component for dispersing the constituent elements such as the above conductive powder, various kinds of those conventionally used in this type of conductive composition are not particularly limited depending on the desired purpose. Can do. Typically, the vehicle is composed of an organic binder having various compositions and an organic solvent as a dispersion medium. In such an organic vehicle component, all of the organic binder may be dissolved in an organic solvent, or only a part thereof may be dissolved or dispersed (may be a so-called emulsion type organic vehicle).

  Examples of the organic binder include cellulose polymers such as ethyl cellulose and hydroxyethyl cellulose, acrylic resins such as polybutyl methacrylate, polymethyl methacrylate, and polyethyl methacrylate, epoxy resins, phenol resins, alkyd resins, polyvinyl alcohol, polyvinyl butyral, etc. An organic binder based on is preferably used. In particular, a cellulosic polymer (for example, ethyl cellulose) is preferable, and a viscosity characteristic capable of performing particularly good screen printing can be realized.

  A preferable organic solvent constituting the organic vehicle is an organic solvent having a boiling point of about 200 ° C. or higher (typically about 200 ° C. to 260 ° C.). An organic solvent having a boiling point of about 230 ° C. or higher (typically about 230 ° C. to 260 ° C.) is more preferably used. Examples of such organic solvents include ester solvents such as butyl cellosolve acetate and butyl carbitol acetate (BCA: diethylene glycol monobutyl ether acetate), ether solvents such as butyl carbitol (BC: diethylene glycol monobutyl ether), ethylene glycol and diethylene glycol. An organic solvent such as a derivative, toluene, xylene, mineral spirit, terpineol, mentanol, or texanol can be preferably used. Particularly preferred solvent components include butyl carbitol (BC), butyl carbitol acetate (BCA), 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and the like.

  The blending ratio of each constituent component contained in the conductive composition may vary depending on the electrode formation method, typically the printing method, etc., but generally conforms to the conductive composition of the composition conventionally employed. It can be set as a mixture ratio. As an example, for example, the ratio of each component can be determined using the following formulation as a guide.

  That is, the content of the conductive powder in the conductive composition is suitably about 70% by mass or more (typically 70% to 95% by mass) when the entire paste is 100% by mass. More preferably, it is preferably about 80% by mass to 90% by mass, for example, about 88% by mass. Increasing the content of the conductive powder is preferable from the viewpoint of forming a dense electrode pattern with good shape accuracy. On the other hand, if the content is too high, the handleability of the paste and the suitability for various printability may be reduced.

  The leaded glass frit may be contained in the conductive composition at a ratio that is essentially required as an inorganic binder of the conductive powder. From the viewpoint of obtaining good fire-through characteristics, the ratio of the leaded glass frit to the conductive powder is typically 0.1% by mass or more when the conductive powder is 100% by mass. The content is preferably 0.5% by mass or more, more preferably 1% by mass or more. Excessive addition is not preferable because it erodes the Si substrate and increases the resistance of the formed electrode. Therefore, the ratio of the leaded glass frit to the conductive powder can be typically 12% by mass or less, preferably 6% by mass or less, and more preferably 3% by mass or less.

  Silicone resin is preferable because the electrode can be formed with a higher aspect ratio by adding even a very small amount to the conductive powder. For example, when the conductive powder is 100% by mass, the amount of silicone resin added can typically be 0.005% by mass or more, preferably 0.01% by mass or more. It is more preferable to set it as 05 mass% or more, and it is especially preferable to set it as 0.1 mass% or more. Excessive addition is not preferable for increasing the resistance of the formed electrode. Therefore, the addition amount of the silicone resin is typically 1.0% by mass or less, preferably 0.9% by mass or less, when the conductive powder is 100% by mass. It is more preferably 8% by mass or less, and particularly preferably 0.6% by mass or less.

Of the organic vehicle components, the organic binder may be contained in a proportion of about 15% by mass or less, typically about 1% by mass to 10% by mass, when the mass of the conductive powder is 100% by mass. preferable. Particularly preferably, it is contained at a ratio of 2% by mass to 6% by mass with respect to 100% by mass of the conductive powder. In addition, this organic binder may contain the organic binder component which is melt | dissolving in the organic solvent, and the organic binder component which is not melt | dissolving in the organic solvent, for example. When the organic binder component dissolved in the organic solvent and the organic binder component not dissolved are included, the ratio thereof is not particularly limited, but for example, the organic binder component dissolved in the organic solvent is (10% to 10%) can be occupied.
In addition, the content rate as a whole of the organic vehicle is variable in accordance with the properties of the obtained paste. As an approximate guide, when the entire conductive composition is 100% by mass, for example, 5% by mass to 30% by mass. %, Is preferably 5% by mass to 20% by mass, and more preferably 5% by mass to 15% by mass (particularly 7% by mass to 12% by mass).

In addition, the conductive composition disclosed herein can contain various inorganic additives and / or organic additives other than those described above without departing from the object of the present invention. Preferable examples of the inorganic additive, ceramic powder other than the above _(ZnO 2, _Al 2 _{O 3,} etc.), other various fillers and the like. Moreover, as a suitable example of an organic additive, additives, such as surfactant, an antifoamer, antioxidant, a dispersing agent, a viscosity modifier, are mentioned, for example.

In the above conductive composition, a predetermined proportion of silicone resin and a leaded glass frit having a specific lead content are used in combination. The silicone resin can remain as an Si component (for example, SiO ₂ ) in the electrode after the conductive composition is baked. Therefore, when this Si component acts as a resistance component, it becomes a factor that the electrode characteristics deteriorate. However, in the conductive composition disclosed herein, the electrode characteristics (for example, FF in a solar cell) are not reduced by appropriately using a silicone resin and a leaded glass frit in combination. From this, it is considered that the PbO component in the leaded glass frit appropriately suppresses the FF lowering effect due to the Si component. On the other hand, when the conductive composition contains a silicone resin, for example, shape stability during printing by screen printing, gravure printing, offset printing, inkjet printing, or the like is enhanced. Therefore, this conductive composition is particularly suitable as a printing composition for an electrode formed by printing (sometimes referred to as paste, slurry, ink, or the like). In particular, it can be particularly preferably employed when such a general-purpose printing means is used when forming an electrode pattern that requires a fine line and a high aspect ratio.

  Below, the example which forms the comb-shaped electrode pattern containing a fine finger electrode on the light-receiving surface by screen-printing this electroconductive composition among the various electrodes provided in a solar cell (solar cell element), for example The solar cell disclosed here will be described with reference to the drawings. Regarding the solar cell, the configuration other than the configuration of the light receiving surface electrode that characterizes the present invention may be the same as that of the conventional solar cell. Since it does not characterize, detailed description is omitted.

  FIG. 1 and FIG. 2 schematically show an example of a solar cell (cell) 10 that can be preferably manufactured by implementing the present invention, and is made of single crystal, polycrystalline, or amorphous silicon (Si). This is a so-called silicon solar cell 10 in which a wafer is used as the semiconductor substrate 11. A cell 10 shown in FIG. 1 is a general single-sided light receiving solar cell 10. Specifically, this type of solar cell 10 has an n-Si layer 16 formed by impurity doping on the light-receiving surface side of a p-Si layer (p-type crystalline silicon) 18 of a silicon substrate (Si wafer) 11. A pn junction is formed. On the surface of the silicon substrate 11, if necessary, a light-receiving surface formed of an antireflection film 14 made of titanium oxide, silicon nitride or the like formed by CVD or the like, and a conductive composition mainly containing Ag powder or the like. Electrodes 12 and 13 are provided. The antireflection film 14 may also serve as a passivation film, or a passivation film may be provided separately from the antireflection film 14.

On the other hand, the back surface side of the p-Si layer 18 is provided with a back surface aluminum electrode 20 that exhibits a so-called back surface field (BSF) effect, and an external connection electrode 22 that extracts current from the aluminum electrode 20. The aluminum electrode 20 is formed on substantially the entire back surface by printing and baking a conductive composition mainly composed of aluminum powder. During this firing, an Al—Si alloy layer (not shown) is formed, and aluminum is diffused into the p-Si layer 18 to form the p ⁺ layer 24. By forming the p ⁺ layer 24, that is, the BSF layer, the photogenerated carriers are prevented from recombining in the vicinity of the back electrode, and for example, an improvement in short circuit current and open circuit voltage (Voc) is realized. The external connection electrode 22 is typically formed by printing and baking a conductive paste whose conductive powder is Ag powder.

  As shown in FIG. 2, on the light receiving surface 11 </ b> A side of the silicon substrate 11 of the solar cell 10, several light receiving surface electrodes 12 and 13 (for example, about 1 to 3) are arranged in parallel with each other. A bus bar (for connection) electrode 12 and a plurality of (for example, about 60 to 90) striped finger (for current collection) electrodes 13 connected to cross the bus bar electrode 12 are formed. Has been. A large number of finger electrodes 13 are formed to collect photogenerated carriers (holes and electrons) generated by light reception. The bus bar electrode 12 is a connection electrode for collecting carriers collected by the finger electrode 13. The portion where the light receiving surface electrodes 12 and 13 are formed forms a non-light receiving portion (light shielding portion) on the light receiving surface 11A of the solar cell. Therefore, the bus bar electrode 12 and the finger electrode 13 (particularly the large number of finger electrodes 13) provided on the light receiving surface 11A side are made as fine lines as possible to reduce the corresponding non-light receiving portion (light shielding portion). Thus, the light receiving area per unit cell area is enlarged. This can extremely simply improve the output per unit area of the solar cell 10.

Such a solar cell 10 is generally manufactured through the following process.
That is, an appropriate silicon wafer is prepared, and the p-Si layer 18 and the n-Si layer 16 are formed by doping predetermined impurities by a general technique such as a thermal diffusion method or ion plantation. A substrate (semiconductor substrate) 11 is produced. At this time, the n-Si layer 16 can be formed so as to have a high sheet resistance (for example, 80 to 120Ω / □). Next, an antireflection film 14 made of silicon nitride or the like is formed by a technique such as plasma CVD.

  After that, on the back surface 11B side of the silicon substrate 11, a predetermined conductive composition (typically a conductive composition in which the conductive powder is Ag powder) is screen-printed in a predetermined pattern and dried. As a result, a back-side conductor coated product that becomes the back-side external connection electrode 22 (see FIG. 1) after firing is formed. Next, a conductive composition containing aluminum powder as a conductor component is applied (supplied) by a screen printing method or the like on the entire back surface, and dried to form an aluminum film.

  Next, the conductive composition of the present invention is printed on the antireflection film 14 formed on the surface side of the silicon substrate 11 by a predetermined wiring pattern as shown in FIG. Supply). The line width to be printed is not particularly limited, but by adopting the conductive composition of the present invention, the line width is about 70 μm or less (preferably in the range of about 50 μm to 60 μm, more preferably in the range of about 40 μm to 50 μm. ) Finger electrode coating film (printed body) having a finger electrode can be formed. Next, the substrate is dried in an appropriate temperature range (typically 100 ° C. to 200 ° C., for example, about 120 ° C. to 150 ° C.). The contents of a suitable screen printing method will be described later.

In this way, the silicon substrate 11 on which the paste application (dried film-like application) is formed on both sides is subjected to an appropriate baking temperature (for example, using a baking furnace such as a near-infrared high-speed baking furnace) in an air atmosphere. Baking is performed at a peak temperature of 700 ° C. to 900 ° C. By this firing, a fired aluminum electrode 20 is formed together with the light-receiving surface electrodes (typically Ag electrodes) 12 and 13 and the back side external connection electrodes (typically Ag electrodes) 22. At the same time, an Al—Si alloy layer (not shown) is formed, and aluminum diffuses into the p-Si layer 18 to form the p + layer (BSF layer) 24 described above, whereby the solar cell 10 is manufactured.
Instead of simultaneous firing as described above, for example, firing for forming the light receiving surface electrodes (typically Ag electrodes) 12 and 13 on the light receiving surface 11A side, the aluminum electrode 20 on the back surface 11B side, and external connection The firing for forming the electrode 22 may be performed separately.

Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.
(Embodiment 1)
[Preparation of conductive composition]
A conductive composition for electrode formation was prepared by the following procedure. That is, as the conductive powder, spherical silver (Ag) powder having an average particle diameter of 2 μm was used. As the glass frit, lead-free and leaded glass powder (average particle size: 1.5 μm) having the following composition was used.

[Lead-free glass frit]
_{1~25mol% Bi 2 O 3 -25~80mol%} TeO 2 -0.1~30mol% ZnO
[Leaded glass frit]
_{1~25mol% PbO-25~80mol% TeO 2} -0.1~30mol% ZnO
The leaded glass frit is a glass containing 30 mol% of PbO in an oxide conversion composition and zinc (Zn) as a network forming element. Further, the lead-free glass frit is glass that does not contain lead (Pb), and instead uses bismuth (Bi) having a function close to that of lead, and contains zinc (Zn) as a network forming element. All of these glass frits have a softening point in the range of 250 ° C. or more and 600 ° C. or less.

  As the silicone resin, polydimethylsiloxane having a weight average molecular weight Mw of 50,000 was used. Moreover, hydrogenated castor oil was used as the surfactant. As the organic vehicle component, a vehicle in which ethyl cellulose (EC) as an organic binder component was dispersed in texanol as a dispersion medium was used.

  When these materials are 100% by mass of silver powder, the glass frit is constant at 2% by mass, and the silicone resin is 0% by mass, 0.1% by mass, 0.3% by mass, 0.6% by mass. The organic vehicle was blended at 5% by mass, hydrogenated castor oil as a surfactant at 0.80% by mass, and texanol as a dispersion medium at about 1% by mass. As the organic vehicle, a mixture of ethyl cellulose and texanol at a mass ratio of 15:85 was used. And these materials were knead | mixed well using a three roll mill, and the electrically conductive composition of each example was obtained. In the present embodiment, in order to make the printability of the conductive composition of each example uniform, the conductive composition is adjusted so that the viscosity of the conductive composition is 180 to 200 Pa · s (20 rpm, 25 ° C.). A sex composition was prepared.

[Production of test solar cells]
By using the conductive composition obtained above to form a light-receiving surface electrode (that is, a comb-shaped electrode composed of finger electrodes and bus bar electrodes), eight types of solar cells were produced.
Specifically, first, a commercially available p-type single crystal silicon substrate (plate thickness 180 μm) for 156 mm square (6 inch square) is prepared, and the surface (light receiving surface) is mixed acid of hydrofluoric acid and nitric acid. Etching was used to remove the damaged layer and form an uneven texture structure. Next, a phosphorus-containing solution was applied to the texture structure surface, and heat treatment was performed to form an n-Si layer (n ⁺ layer) having a sheet resistance of 90 ± 10 Ω / □ on the light receiving surface of the silicon substrate. Next, a silicon nitride film having a thickness of about 80 nm was formed on the n-Si layer by a plasma CVD (PECVD) method to obtain an antireflection film.

  Next, the back side electrode pattern was formed on the back side of the silicon substrate by using a predetermined silver electrode forming paste, followed by screen printing with a predetermined pattern to be a back side external connection electrode and drying. . Then, an aluminum electrode forming paste was screen-printed on the entire back surface and dried to form an aluminum film.

  Thereafter, using the conductive composition prepared above, an electrode pattern for a light-receiving surface electrode (Ag electrode) was printed on the antireflection film by a screen printing method and dried at 120 ° C. Specifically, as shown in FIG. 2, an electrode pattern comprising three mutually parallel linear busbar electrodes and 90 finger electrodes parallel to each other so as to be orthogonal to the busbar electrodes. It was formed by screen printing. For screen printing, a screen plate having a 360 mesh (wire diameter: 16 μm, emulsion thickness: 15 μm) was used. The finger electrode pattern was adjusted such that the dimensions after firing were about 45 μm in line width and 15 μm to 25 μm in film thickness. The bus bar electrode was set so that the line width after firing was approximately 1.5 mm. Thus, the solar cell for evaluation was produced by baking the board | substrate which printed the electrode pattern on both surfaces in the air atmosphere at the baking temperature of 700-800 degreeC using the near-infrared high-speed baking furnace.

[Evaluation]
About the solar cell produced as mentioned above, the open circuit voltage (Voc) and the fill factor (FF) were measured. Specifically, based on the “crystalline solar cell output measurement method” defined in JIS C8913 from the IV curve obtained for the solar cell of each example using a solar simulator (manufactured by Beger, PSS10). The open circuit voltage (Voc) and fill factor (FF) were calculated. The results are shown in FIG. 3 for the open circuit voltage (Voc) and in FIG. 4 for the fill factor (FF).

  As shown in FIG. 3, by adding a silicone resin to the conductive composition and increasing its content, the open-circuit voltage of a solar cell including an electrode formed from this conductive composition tends to increase. I understood it. It was also confirmed that this tendency was remarkable when a leaded glass frit was used as the glass frit. For conductive compositions using leaded glass frit, even when no silicone resin is contained (0% by mass), a higher open-circuit voltage can be obtained than conductive compositions using lead-free glass frit. It was found that the effect was greatly improved by addition. In addition, although no specific data is shown, such a tendency is greatly different depending on whether the glass frit is leaded or lead-free, but the leaded glass frit is not significantly affected by the ratio of glass components other than lead. It could be confirmed.

  On the other hand, as shown in FIG. 4, the tendency different from the open circuit voltage was observed for the fill factor. That is, it has been found that, for a conductive composition using a lead-free glass frit as a glass frit, the addition of a silicone resin significantly reduces the fill factor. The decrease in the fill factor is about 10% when 0.6 mass% of the silicone resin is added, indicating that it is not at a practical level. On the other hand, for the conductive composition using leaded glass frit, it was found that no significant effect was found on the fill factor even when the silicone resin was added. Although specific data are not shown, this trend is largely unaffected by the proportion of glass components other than lead in both leaded and leadless glass frit, although the glass frit differs greatly depending on whether it is leaded or leadless. I was able to confirm. In addition, it has been confirmed that the above tendency is generally the same when the content of the glass frit in the conductive composition is changed.

(Embodiment 2)
[Preparation of conductive composition]
Subsequently, the lead content in the glass frit was changed, and other conditions were the same as in Embodiment 1 to prepare a conductive composition for electrode formation. No. used in this embodiment. The compositions of 1 to 45 glass frit are shown in Table 1 below.
That is, as shown in Table 1, No. In the glass frit Nos. 1 to 9, Si and B are used as the network forming elements, and 10 to 18 glass frit has P as the network forming element, Glass frit Nos. 19 to 27 have Te as the network-forming element, No. The glass frit of 28 to 36 has V as the network-forming element and No. The glass frit 37 to 45 uses Mo as a network forming element. And content of lead used as a network modification element is changed in the range of 0-70 mol% as PbO. For glass frit (No. 1, 10, 19, 28, 37) with 0 mol% of PbO, bismuth, which is said to exhibit a similar action to lead, is used as a network-forming element instead of lead (Bi ₂ As O ₃ ). No. The content of SiO ₂ in the glass frit 1-9 is about 9~10mol%. All of these glass frits have a softening point in the range of 250 ° C. or more and 600 ° C. or less.

  Further, in the conductive composition, when the silver powder is 100 mass%, the glass frit ratio is constant at 2 mass%, and the silicone resin ratio is 0 mass%, 0.005 mass%, 0.05 mass%. , 0.1% by mass, 0.3% by mass, 0.6% by mass, 0.9% by mass, and 1.2% by mass. Further, 6.7% by mass of ethyl cellulose and 0.80% by mass of hydrogenated castor oil were added, and while kneading well using a three roll mill, about 1% by mass of texanol was added and the viscosity was about 180 to 200 Pa. -It adjusted so that it might become s (20 rpm, 25 degreeC). Thereby, 360 kinds of conductive compositions were prepared.

[Production of test solar cells]
Using the conductive composition thus obtained, a solar cell including a light-receiving surface electrode formed using this conductive composition was produced in the same manner as in Embodiment 1. And the open circuit voltage (Voc) and fill factor (FF) of this solar cell were measured using the solar simulator (The Beger company make, PSS10). The results are shown in Table 1 for the open circuit voltage (Voc) and in Table 2 for the fill factor (FF).

In Table 1, for each conductive composition using a glass frit having a common network forming element, Voc is reduced on the basis of the Voc value when a lead-free glass frit is used and the amount of silicone resin is 0% by mass. In this case, “x” indicates “◯” when Voc increases from 0 to less than 1 mV, and “◎” indicates that Voc increased by 1 mV or more. In this embodiment, there was no example where the result was “x”. Further, the result when the amount of the silicone resin is 0% by mass is not shown.
In Table 2, for each conductive composition, “X” when FF is less than 75%, “◯” when FF is 75% or more and less than 77%, and “◎” when FF is 77% or more. As shown.

  As shown in Table 1, in this embodiment, there was no example in which Voc was lowered by adding a silicone resin to all conductive compositions regardless of the composition of the glass frit. However, for conductive compositions containing lead-free glass frit, Voc did not increase even when silicone resin was added, or the increase was less than 1 mV, whereas conductive compositions containing leaded glass frit It was found that Voc can be increased by 1 mV or more by adding a silicone resin. However, it was found that when the content of the silicone resin was increased to 1.2% by mass, Voc was reduced to the same extent as when the silicone resin amount was not added, and the effect was offset.

  In addition, for conductive compositions containing leaded glass frit, Voc can be increased by 1 mV or more when the PbO content in the glass frit is 2 to 60 mol%, regardless of the detailed composition of the glass frit. I understood. However, it was found that when the PbO content in the glass frit was increased to 70 mol%, Voc was reduced to the same extent when the PbO content was 0 mol%, and the effect was almost lost.

On the other hand, as shown in Table 2, for the FF, the examples using the lead-free glass frit with PbO of 0 mol% (No. 1, 10, 19, 28, 37), regardless of the composition, the silicone resin It was found that the FF showed a low value of less than 75% by adding. Moreover, about the example (No.9,18,27,36,45) which uses the leaded glass frit by which PbO was increased to 70 mol%, regardless of the composition, FF is attained by adding a silicone resin. It turned out that all show a low value of less than 75%.
Furthermore, it was found that the examples in which the addition amount of the silicone resin was 1.2% by mass showed a low value of FF of less than 75% regardless of the composition of the glass frit.
On the other hand, in an example in which a lead-free glass frit having a PbO content of 2 to 60 mol% was used and the addition amount of the silicone resin was less than 1.2% by mass, the FF was 75% or higher in all examples. It was found to show characteristics.

Note that the example using a _PbO-SiO 2 _-B 2 _{O 3} based glass frit containing Si and B a leaded glass in Example 2-8 as a network-forming element, the amount of the silicone resin 1.2 It was found that when the PbO content was less than 50% by mass and less than 50% by mass, the FF was as high as 77% or more. However, it was found that when the content of PbO in the glass frit is as low as 2 mol% or less, a high FF of 77% or more can be obtained when the addition amount of the silicone resin is less than 0.9 mass%. Further, when the content of PbO is 50 mol% or more and less than 60 mol%, when the addition amount of the silicone resin is more than 0.05 mass% (less than 1.2 mass%), a high value of FF of 77% or more is obtained. I found out that

Further, for an example of using a _PbO-P 2 O 5 -ZnO-based glass frit containing P a leaded glass in Example 11 to 17 as a network-forming element, the amount of the silicone resin less than 1.2 wt% As a result, it was found that a high FF of 77% or more can be obtained by setting the PbO content to more than 10 mol% and less than 50 mol%. Further, when the PbO content of the glass frit is 10 mol% or less, the amount of the silicone resin added is suppressed to less than 0.9% by mass. When the PbO content of the glass frit is 5 mol% or less, the silicone resin By suppressing the addition amount to less than 0.3% by mass, when the PbO content of the glass frit is 2 mol% or less, the addition amount of the silicone resin is suppressed to less than 0.005% by mass, and is as high as 77% or more. It was found that FF was obtained. Furthermore, when the content of PbO in the glass frit is 50 mol% or more and less than 60 mol%, the addition amount of the silicone resin is more than 0.05 mass% (less than 1.2 mass%), so that 77% or more It was found that a high FF was obtained.

Further, for an example of using a _PbO-TeO 2 -ZnO based glass frit A leaded glass in Example 20 to 26 containing Te as a network-forming element, the amount of the silicone resin as less than 1.2 wt%, It turned out that 77% or more high FF is obtained by making content of PbO more than 5 mol% and less than 50 mol%. Further, when the content of PbO in the glass frit is 5 mol% or less, the amount of silicone resin added is suppressed to less than 0.9% by mass. When the content of PbO in the glass frit is 2 mol% or less, It was found that by controlling the addition amount to less than 0.3% by mass, a high FF of 77% or more can be obtained. Furthermore, when the content of PbO in the glass frit is 50 mol% or more and less than 60 mol%, the addition amount of the silicone resin is more than 0.05 mass% (less than 1.2 mass%), so that 77% or more It was found that a high FF was obtained.

For the leaded glass of Examples 29 to 35 and using the PbO—V ₂ O ₅ —P ₂ O ₅ glass frit containing V as a network forming element, the addition amount of the silicone resin is 1.2 mass%. It was found that a high FF of 77% or more can be obtained by setting the PbO content to more than 10 mol% and less than 50 mol%. Further, it was found that when the content of PbO in the glass frit is 10 mol% or less, a high FF of 77% or more can be obtained by suppressing the addition amount of the silicone resin to less than 0.6 mass%. Furthermore, when the content of PbO in the glass frit is 50 mol% or more and less than 60 mol%, the addition amount of the silicone resin is more than 0.005 mass% (less than 1.2 mass%), so that 77% or more It was found that a high FF was obtained.

For the leaded glass of Examples 38 to 44 and using the PbO—MoO ₃ —B ₂ O ₃ glass frit containing Mo as a network forming element, the amount of silicone resin added is less than 1.2% by mass. It was found that a high FF of 77% or more can be obtained by setting the PbO content to more than 5 mol% and less than 50 mol%. Further, when the content of PbO in the glass frit is 5 mol% or less, the addition amount of the silicone resin is suppressed to less than 0.3% by mass. When the content is 2 mol% or less, the addition amount of the silicone resin is 0.005% by mass. It was found that by controlling to less than 77%, a high FF of 77% or more can be obtained. Furthermore, when the content of PbO in the glass frit is 50 mol% or more and less than 60 mol%, the addition amount of the silicone resin is more than 0.005 mass% (less than 1.2 mass%), so that 77% or more It was found that a high FF was obtained.

  From the above, when using leaded glass, (1) the amount of silicone resin added is less than 1.2% by mass, and the content of PbO is more than 10 mol% and less than 50 mol%, (2) glass When the PbO content of the frit is less than 20 mol%, the amount of silicone resin added should be suppressed to less than 0.6% by mass. (3) The PbO content of the glass frit exceeds 40 mol% and reaches 60 mol%. If not, the addition amount of the silicone resin is more than 0.05% by mass (less than 1.2% by mass), so that a high FF of 77% or more can be obtained regardless of the composition of the glass frit other than Pb. It can be said that it is definitely obtained.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

10 Solar cell (cell)
11 Substrate (silicon substrate)
11A Light-receiving surface 11B Back surface 12 Bus bar electrode (light-receiving surface electrode)
13 Finger electrode (light-receiving surface electrode)
14 Antireflection film 16 n-Si layer 18 p-Si layer 20 Back surface aluminum electrode 22 Back surface side external connection electrode 24 p ⁺ layer

Claims (7)

A conductive composition for forming an electrode of a solar cell,
Conductive powder;
Leaded glass frit,
Silicone resin,
An organic binder,
A dispersion medium,
The leaded glass frit has a PbO component ratio of 2 mol% or more and 60 mol% or less when converted to an oxide,
The silicone resin has a weight average molecular weight of 1,000 or more and 150,000 or less, and is contained in a proportion of 0.005% by mass or more and 0.9% by mass or less with respect to 100% by mass of the conductive powder .
Wherein the conductive powder is, when the entire conductive composition is 100 mass%, Ru contained in a proportion of 80 wt% to 95 wt% or less, the conductive composition. Metal species constituting the conductive powder is nickel, platinum, palladium, silver, comprising any one or two or more elements selected from the group consisting of copper and aluminum, conductive claim 1 Composition.   The electrically conductive composition according to claim 2, wherein the metal species constituting the electrically conductive powder includes silver.   The conductive composition according to claim 1, wherein the silicone resin includes a linear silicone.   5. The conductive composition according to claim 1, wherein the leaded glass frit is contained at a ratio of 0.1% by mass to 12% by mass with respect to 100% by mass of the conductive powder. .   The said organic binder is a conductive composition of any one of Claims 1-5 contained in the ratio of 1 mass% or more and 15 mass% or less with respect to 100 mass% of said electroconductive powders. The solar cell provided with the baked product of the electroconductive composition of any one of Claims 1-6 as an electrode.

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