TW201930220A - Glass, glass powder, conductive paste and solar cell sufficiently in contact with the insulating film and the semiconductor substrate so as to make sure of the above being secured by the glass - Google Patents

Abstract

This invention provides a glass, a glass powder containing the glass, a conductive paste containing the glass powder, and solar cells with improved conversion efficiency by using the conductive paste. When an electrode is formed on a semiconductor substrate such as a solar cell via an insulating film, the glass is sufficiently in contact with the insulating film and the semiconductor substrate, and sufficient reliability can be maintained in the same time, and the conversion efficiency of the solar cell can be increased. The glass is characterized by comprising, in terms of mol% relative to oxide, 6% to 30% of V2O5, 15% to 50% of B2O3, 10% to 40% of BaO, 5% to 30% of ZnO, and 0 to 15% of Al2O3. The glass powder comprises the glass and has a D50 of 0.8 to 6.0 [mu]m when a volume-based 50% particle size in the cumulative particle size distribution is set as D50.

Description

Glass, glass powder, conductive paste and solar cells

The invention relates to a glass, a glass powder, a conductive paste, and a solar cell, and more particularly, to a glass, a glass powder, a conductive paste using the glass powder, and a conductive paste using the glass powder. Solar cells with formed electrodes.

Previously, electronic devices in which a conductive layer as an electrode was formed on a semiconductor substrate such as silicon (Si) were used for various purposes. Such a conductive layer as an electrode is formed by dispersing a conductive metal powder such as aluminum (Al), silver (Ag), copper (Cu), and glass powder in an organic vehicle. The material is coated on a semiconductor substrate and calcined at a temperature required for electrode formation.

When an electrode is formed on a semiconductor substrate in this manner, there is a case where an insulating film is formed on the entire surface of the electrode on which the semiconductor substrate is formed, and the patterned electrode partially penetrates the insulating film to contact the semiconductor substrate Way of forming. For example, in a solar cell, an antireflection film is provided on a semiconductor substrate that becomes a light-receiving surface, and electrodes are provided thereon in a pattern. The anti-reflection film is used to reduce the frontal reflectivity and improve the light receiving efficiency while maintaining sufficient visible light transmittance, and is generally composed of insulating materials such as silicon nitride, titanium dioxide, silicon dioxide, and aluminum oxide. Moreover, in solar cells such as PERC (Passivated Emitter and Rear Contact), a passivation film containing the same insulating material as the anti-reflection film is also provided on the entire rear surface, and the electrode A contact gesture is formed on the passivation film.

Here, in the formation of the above-mentioned electrode, it is necessary to form the electrode so as to be in contact with the semiconductor substrate, and remove the portion of the insulating film corresponding to the pattern of the electrode on the light-receiving surface, and form the electrode on the portion of removing the insulating film. In addition, the insulating film is partially removed within a range where electrical contact can be made on the back surface of a PERC solar cell or the like, and an electrode is formed on the entire back surface.

As a method of partially removing the insulating layer, a laser or the like is used to physically remove the electrode, and an electrode is formed on the portion from which the insulating layer has been removed, whereby the electrode is in contact with the semiconductor to operate as a solar cell. In the previous solar cell structure, if the back electrode was directly in contact with a semiconductor substrate such as Si as a whole and an electrode was formed, it would operate as a solar cell through the entire back contact. On the other hand, in the case of a structure such as a PERC solar cell, the area excluding the insulating film is approximately 1 to 3% of the entire back surface, and most of the back electrode is formed on the insulating film.

The above-mentioned technique of forming an electrode on a semiconductor substrate is also applied to electrode formation on a pn-junction semiconductor substrate in a solar cell. As such a conductive paste containing glass powder, for example, Patent Document 1 describes a paste for an electrode of an electronic device. Patent Document 1 discloses a lead-free glass containing vanadium oxide as a main component capable of forming an electrode having excellent durability against corrosive gases and the like, and containing V ₂ O in terms of oxide as a specific glass composition. _5: 26.7 mole%, ZnO: 22.2 mole%, BaO: 17.8 mole%, Sb ₂ O _3: 11.0 mole%, and P ₂ O _5: 22.3 mole%. However, since the glass described in Patent Document 1 does not sufficiently contain B ₂ O ₃ , especially when a back electrode of a solar cell in a p-type semiconductor substrate is formed, boron as a majority carrier cannot be sufficiently diffused into Si. In the substrate, there is a problem that the electrical characteristics are deteriorated.

Patent Document 2 discloses glass as a coating glass which contains V ₂ O ₅ : 4.4 mole%, B ₂ O ₃ : 9.2 mole%, ZnO: 26.5 mole%, and BaO in terms of oxide. : 5.2 mole%, Al ₂ O ₃ : 10.2 mole%, SiO ₂ : 30.6 mole%, MgO: 6.0 mole%, CaO: 7.1 mole%, and SrO: 0.8 mole%. However, if the glass described in Patent Document 2 is used for electrode formation, since the content of V ₂ O _{5 is} low and the content of SiO _{2 is} high, the softening point of the glass is increased, and there is not enough glass for the firing required for electrode formation. The problem of mobility.

In Patent Document 3, as a lead-free glass for a plasma display panel partition wall, there is disclosed a glass containing V ₂ O ₅ : 17.5 mole%, B ₂ O ₃ : 15.2 mole%, and ZnO: 26.0 mole%, BaO: 6.9 mole%, Al ₂ O _3: 5.2 mole%, K ₂ O: 5.6 mole%, CaO: 9.4 mole%, TiO _2: 6.6 mole%, and P ₂ O ₅ : 7.5 mole%. However, if the glass described in Patent Document 3 is used to form an electrode on the back side of a PERC solar cell that cuts off the edge film, the contact resistance component between the electrode and the semiconductor substrate increases due to the low BaO content, and the battery characteristics decrease Problem.

In Patent Document 4, as a lead-free low-melting glass, there is disclosed a glass containing V ₂ O ₅ : 16.3 mol%, B ₂ O ₃ : 18.0 mol%, and ZnO: 34.1 mol% in terms of oxide. , BaO: 13.8 mole%, Al ₂ O _3: 3.6 mole%, TeO _2: 4.0 mole%, TiO _2: 6.0 mole%, and MoO _3: 4.1 mole%. However, if the glass described in Patent Document 4 is used to form an electrode on the back side of a PERC solar cell or the like that cuts off the edge film, the glass and the insulating film are excessive when the electrode is formed because of the high ZnO content and low glass transition point The reaction has a problem that the appearance of the electrode is deteriorated.
[Prior technical literature]
[Patent Literature]

[Patent Document 1] Japanese Patent No. 5754090
[Patent Document 2] Japanese Patent Laid-Open No. 3-126639
[Patent Document 3] Japanese Patent Laid-Open No. 2006-8496
[Patent Document 4] Japanese Patent Laid-Open No. 6-263478

[Problems to be solved by the invention]

Regarding vanadium-based glass used for electrode formation of a solar cell, many techniques have been developed as described in Patent Document 1 to improve the electrode formability. However, the following technologies are under development, especially in solar cells such as PERC. Even if the glass composition or particle size distribution of the glass powder used for electrode formation is adjusted, under current conditions, it can be fully maintained with electrode formation. Reliability, and reduce the resistance between the electrode and the semiconductor substrate, thereby improving the conversion efficiency of the solar cell.

An object of the present invention is to provide a glass which is used for electrode formation. When forming an electrode through an insulating film on a semiconductor substrate such as a solar cell, the following electrode can be formed, which has a good appearance and can sufficiently secure the insulating film. It is in contact with semiconductor substrates, while maintaining sufficient reliability due to water resistance, etc., and the glass can improve the conversion efficiency of solar cells. An object of the present invention is to further provide a glass powder containing the glass, a conductive paste containing the glass powder, and a solar cell having improved conversion efficiency by using the conductive paste.
[Technical means to solve the problem]

The present invention provides glass, glass powder, conductive paste, and solar cells having the following constitutions.
[1] A glass characterized in that it is expressed in mole% in terms of oxides and contains V ₂ O ₅ : 6 to 30%, B ₂ O ₃ : 15 to 50%, BaO: 10 to 40%, and ZnO: 5 to 30% and Al ₂ O ₃ : 0 to 15%.
[2] The glass according to [1], which is expressed in mole% in terms of oxide, and further contains at least one selected from SiO ₂ , SrO, MoO ₃ and WO ₃ in a total of 0 to 10%.
[3] The glass according to [1] or [2], wherein the glass transition temperature is 380 to 550 ° C.
[4] A glass powder comprising the glass according to any one of [1] to [3], and when the 50% particle diameter based on the volume basis in the cumulative particle size distribution is set to D ₅₀ , D ₅₀ is 0.8 to 6.0 μm.
[5] A conductive paste containing the glass powder as described in [4], a conductive metal powder, and an organic vehicle.
[6] A solar cell comprising an electrode formed using a conductive paste as described in [5].
[7] A conductive paste, characterized in that it contains a metal, glass, and an organic vehicle, and the metal contains 63.0 to 97.9% by mass relative to the total mass of the conductive paste, and is selected from Al, Ag At least one of the group consisting of Cu, Au, Pd, and Pt; the glass contains 0.1 to 9.8 parts by mass relative to 100 parts by mass of the metal, expressed in mole% in terms of oxides, and contains V ₂ O ₅ : 6-30%, B ₂ O ₃ : 15-50%, BaO: 10-40%, ZnO: 5-30%, and Al ₂ O ₃ 0-15%; and the organic vehicle is relative to the conductive paste. The total mass contains 2 to 30% by mass.
[8] The conductive paste as described in [7], in which Mohr% expressed in terms of oxides, said glass further contains a total of 0 to 10% of at least 1 selected from SiO ₂ , SrO, MoO ₃ and WO ₃ Species.
[9] The conductive paste according to [7] or [8], wherein the glass transition temperature of the glass is 380 to 550 ° C.
[10] The conductive paste according to any one of [7] to [9], wherein the glass is a D ₅₀ of 0.8 to 6.0 when the 50% particle diameter of the volume basis in the cumulative particle size distribution is set to D ₅₀ μm glass particles.
[11] The conductive paste according to any one of [7] to [10], wherein the metal contains Al.
[12] The conductive paste according to any one of [11] in [7], wherein the organic vehicle is an organic resin adhesive solution obtained by dissolving an organic resin adhesive in a solvent, and the organic resin adhesive Contains: selected from the group consisting of acrylic resin, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, ethoxy cellulose, benzyl cellulose, propyl cellulose, and nitrocellulose At least one type of the acrylic resin is selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, butyl acrylate, and 2-hydroxyethyl acrylate The obtained group is obtained by polymerizing at least one or more species; and the solvent includes a solvent selected from the group consisting of terpineol, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, and propylene glycol diacetic acid. At least one of the group consisting of an ester and methyl ethyl ketone.
[13] A solar cell comprising: a silicon substrate having a solar light receiving surface; a first insulating film provided on the solar light receiving surface side of the silicon substrate; and a second insulating film provided on the silicon substrate A surface of the silicon substrate opposite to the above-mentioned sunlight-receiving surface and having at least one opening; a second electrode that is in contact with the silicon substrate through the opening of the second insulating film; and a first electrode that passes through A part of the first insulating film is in contact with the silicon substrate; and the second electrode includes: a metal containing at least one selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt; and an oxide Molar% in terms of material means that it contains V ₂ O ₅ : 6-30%, B ₂ O ₃ : 15-50%, BaO: 10-40%, ZnO: 5-30%, and Al ₂ O ₃ 0-15. % Of glass.
[14] The solar cell according to [13], wherein the second electrode includes 90 to 99.9% by mass of the metal and 0.1 to 10% by mass of the glass.
[15] The solar cell according to [13] or [14], wherein the metal contained in the second electrode contains at least Al.
[16] The solar cell according to any one of [13] to [15], wherein the first electrode includes a metal containing at least Ag.
[17] The solar cell according to any one of [13] to [16], wherein the first insulating film contains silicon nitride.
[18] The solar cell according to any one of [13] to [17], wherein the second insulating film includes an alumina-containing or abutting surface on the opposite side of the solar light-receiving surface of the silicon substrate. An oxide metal film of silicon oxide, and further comprising a silicon nitride film on the oxide metal film.
[Effect of the invention]

The glass of the present invention and the glass powder containing the glass are used in a conductive paste together with a conductive component, whereby when an edge film is formed on a semiconductor substrate such as a solar cell to form an electrode, it can sufficiently ensure the insulation film. And semiconductor substrate. In addition, the powder is a powder of glass containing boron, which can diffuse the boron contained in the glass into the p-type layer of the semiconductor substrate during the formation of the electrode, thereby forming a good p ⁺ layer, thereby improving the conversion efficiency of the solar cell. .

Furthermore, by using the glass of the present invention for electrode formation with an insulating film on a semiconductor substrate such as a solar cell, it is possible to suppress appearance defects such as electrode peeling or discoloration during electrode formation. In addition, since the formed electrode has water resistance and the like, it can also have high reliability, and can sufficiently cope with a case where a semiconductor such as a solar cell needs to be operated in any environment.

In the present invention, a conductive paste containing the glass powder, which can be used for electrode formation, can improve the conversion efficiency of a solar cell, and a solar cell whose conversion efficiency is improved by using the conductive paste can be provided.

Hereinafter, embodiments of the present invention will be described.
＜ Glass ＞
The glass of the present invention in terms of Moire% indicates that it contains V ₂ O ₅ : 6-30%, B ₂ O ₃ : 15-50%, BaO: 10-40%, ZnO: 5-30%, and Al. ₂ O ₃ : 0 to 15%. In the following description, unless otherwise specified, the expression of "%" in the content of each component of the glass is expressed in mole% in terms of oxide conversion. In this specification, "~" indicating a numerical range includes the upper and lower limits.

The content of each component in the glass of the present invention is analyzed based on the obtained ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy) analysis or the electron beam microanalyzer (EPMA: Electron Probe Micro Analyzer) analysis The result is obtained.

In the glass of the present invention, V ₂ O ₅ is an essential component that improves the softened fluidity of the glass and can obtain contact with an insulating film and a semiconductor substrate in an electrode obtained by using a conductive paste containing the glass. Hereinafter, in the description of the glass components, "conductive paste" means "conductive paste containing the glass of the present invention", and "electrode" means "electrode obtained using the conductive paste containing the glass of the present invention". In addition, the glass transition point is reduced by V ₂ O ₅ in the glass, and the contact between the electrode and the insulating film and the semiconductor substrate can be easily adjusted. As a result, the subsequent reaction between the electrode and the semiconductor substrate can be promoted, the contact resistance can be reduced, and the adhesion between the electrode and the insulating film can be improved.

V ₂ O ₅ can further improve the wettability of the conductive paste with the conductive metal, and can reduce the resistance of the electrode by improving the bonding between the conductive metals. In addition, the formation of an oxide film on the surface of the conductive metal at the time of electrode formation can adjust the weather resistance. The effect is particularly good when the conductive metal is Al.

The glass of the present invention contains V ₂ O _{5 in a} ratio of 6% to 30%. If the content of V ₂ O ₅ is less than 6%, the softening point of the glass will increase and the fluidity will decrease. As a result, the contact between the electrode and the insulating film and the semiconductor substrate, and the combination of conductive metals in the electrode will be insufficient. The content of V ₂ O ₅ is preferably 7% or more, and more preferably 8% or more. On the other hand, when the content of V ₂ O ₅ exceeds 30%, the glass and the insulating film react excessively, the obtained electrode is discolored, and the conductive metal is excessively oxidized to increase the resistance. The content of V ₂ O ₅ is preferably 29% or less, and more preferably 28% or less.

In the glass of the present invention, B ₂ O ₃ is an essential component. B ₂ O ₃ has the function of improving the softening fluidity of glass and improving the contact between the electrode and the insulating film and the semiconductor substrate. B ₂ O ₃ is a component that stabilizes glass.

Furthermore, since B ₂ O ₃ causes glass to flow, direct reaction between the semiconductor substrate and the glass in the conductive paste can be promoted. Thereby, for example, when the semiconductor substrate is a pn junction Si semiconductor substrate, a p ⁺ layer or an n ⁺ layer in contact with the electrode can be formed satisfactorily. For example, when an electrode in contact with the p ⁺ layer is formed, it is possible to promote the diffusion of B in B ₂ O ₃ as a component contained in the glass to the p ⁺ layer, thereby forming a better p ⁺ layer.

The glass of the present invention contains B ₂ O _{3 at a} ratio of 15% to 50%. If the content of B ₂ O ₃ is less than 15%, B cannot be sufficiently diffused into the Si semiconductor substrate when the electrode is formed, and thus, for example, the conversion efficiency in a solar cell may not be improved. Furthermore, B ₂ O ₃ is a component that forms a network structure of glass, and if its content is less than 15%, vitrification cannot be performed. The content of B ₂ O ₃ is preferably 18% or more, and more preferably 20% or more. On the other hand, if the content of B ₂ O ₃ exceeds 50%, the weather resistance deteriorates. The content of B ₂ O ₃ is preferably 48% or less, and more preferably 45% or less.

In the glass of the present invention, BaO is an essential component for reducing the contact resistance between an electrode and a semiconductor substrate. BaO can be used as a glass component or as a modified oxide to stabilize the glass. The content of BaO in the glass of the present invention is 10% or more and 40% or less. If the content of BaO is less than 10%, the contact resistance between the electrode and the semiconductor substrate increases when the electrode is formed, and therefore, for example, the conversion efficiency in a solar cell may not be improved. Moreover, vitrification becomes difficult. The content of BaO is preferably 13% or more, and more preferably 15% or more. When the content of BaO exceeds 40%, glass cannot be obtained due to crystallization. The content of BaO is preferably 35% or less, and more preferably 30% or less.

In the glass of the present invention, ZnO is an essential component. ZnO is a component that can suppress crystallization of glass and improve the reactivity of insulating films on Si substrates such as glass and Si substrates or Si substrates. The glass of the present invention contains ZnO in a ratio of 5% to 30%. If the content of ZnO is less than 5%, the reactivity between the glass and the insulating film on the semiconductor substrate such as the Si substrate or the Si substrate is deteriorated, the bonding strength is weakened, and the resistance between the electrode and the semiconductor substrate is increased. The content of ZnO is preferably 6% or more. When the content of ZnO exceeds 30%, the glass and the insulating film react excessively when the electrode is formed, the appearance of the electrode is deteriorated, and weather resistance such as water resistance is reduced. The content of ZnO is preferably 27% or less.

In the glass of the present invention, Al ₂ O ₃ is a component for improving weather resistance. In addition, by containing Al ₂ O ₃ , the glass can be stabilized. The content of Al ₂ O ₃ in the glass of the present invention is 0% or more and 15% or less. The content of Al ₂ O ₃ is preferably 2% or more, and more preferably 5% or more. When the content of Al ₂ O ₃ exceeds 15%, the glass transition point increases, so that the glass cannot flow during sintering. The content of Al ₂ O ₃ is preferably 13% or less.

The glass of the present invention preferably further contains at least one selected from the group consisting of SiO ₂ , SrO, MoO ₃ and WO ₃ in a total amount of 0 to 10%. When the glass of the present invention contains these components, the glass can be stabilized and the weather resistance can be improved. The content of SiO ₂ , SrO, MoO ₃ and WO ₃ is preferably 0.5% or more in total. If the total of SiO ₂ , SrO, MoO ₃ and WO ₃ exceeds 10%, vitrification may not be performed. The content of SiO ₂ , SrO, MoO ₃ and WO ₃ is preferably 8% or less in total.

The glass of this invention may contain arbitrary components other than these. Specific examples of other optional components include PbO, Bi ₂ O ₃ , P ₂ O ₃ , As ₂ O ₅ , Sb ₂ O ₅ , Li ₂ O, Na ₂ O, K ₂ O, ZrO ₂ , and Fe ₂ O ₃ , CuO, Sb ₂ O ₃ , SnO ₂ , MnO, MnO ₂ , CeO ₂ , TiO ₂ and other oxide components used in ordinary glass.

These other arbitrary components can be used individually by 1 type or in combination of 2 or more types according to the objective. The content of other optional components is preferably 64% or less, more preferably 60% or less, still more preferably 50% or less, and most preferably 40% or less for each component. Furthermore, the total content of other optional components is preferably 50% or less, and more preferably 40% or less.

The glass of the present invention preferably has a glass transition temperature of 380 ° C or higher and 550 ° C or lower. If the glass transition temperature does not reach 380 ° C, the fluidity of the glass during sintering is higher than required. If the fluidity of glass is too high, for example, when it is used in a conductive paste, the conductive component is separated from the glass, and sufficient conductivity cannot be provided in the obtained electrode. In addition, since the glass transition point is low, the glass and the insulating film react excessively when the electrode is formed, and the appearance of the electrode may be deteriorated. If the glass transition temperature exceeds 550 ° C, the glass may not flow sufficiently during sintering, and the characteristics may become unstable. The glass transition temperature is more preferably 390 ° C to 520 ° C.

In the present invention, the glass transition temperature is obtained by using a differential thermal analysis (DTA) device TG8110 manufactured by RIGAKU to measure at a temperature increase rate of 10 ° C./minute to obtain a DTA diagram, 1 turning point.

The manufacturing method of the glass of this invention is not specifically limited. For example, it can manufacture by the method shown below.

First, a raw material mixture is prepared. The raw material is not particularly limited as long as it is a raw material used in the production of general oxide-based glass, and oxides, carbonates, and the like can be used. In the obtained glass, the type and ratio of the raw materials were appropriately adjusted so as to become the above-mentioned composition range as a raw material mixture.

Next, the raw material mixture is heated by a well-known method to obtain a melt. The temperature (melting temperature) for heating and melting is preferably 800 to 1400 ° C, and more preferably 900 to 1300 ° C. The time for heating and melting is preferably 30 to 300 minutes.

Thereafter, the glass of the present invention can be obtained by cooling and solidifying the melt. The cooling method is not particularly limited. A rapid cooling method such as a roller press, a punch, and the addition of a cooling liquid can also be used. The obtained glass is preferably completely amorphous, that is, the degree of crystallinity is 0%. However, as long as the effect of the present invention is not impaired, a crystallized portion may be included.

The glass of the present invention thus obtained may be in any form. For example, it may be a block shape, a plate shape, a thin plate shape (sheet shape), a powder shape, and the like.

The glass of the present invention has a function as a binder and has weather resistance such as water resistance, and is preferably used in a conductive paste. The conductive paste containing the glass of the present invention is preferably used for electrode formation of a solar cell, for example. When the conductive paste contains the glass of the present invention, the glass is preferably a powder.

＜ Glass powder ＞
The glass powder of the present invention contains the glass of the present invention, and D _{50 is} preferably 0.8 μm or more and 6.0 μm or less. The range of D ₅₀ is a particularly preferable range for a conductive paste. When D ₅₀ is 0.8 μm or more, the dispersibility when used as a conductive paste is further improved. In addition, since D ₅₀ is 6.0 μm or less, a portion where glass powder does not exist is not easily generated around the conductive metal powder, and thus the adhesion between the electrode and the semiconductor substrate is further improved. D _{50 is more} preferably 1.0 μm or more. D _{50 is more} preferably 5.0 μm or less.

Further, in this specification, "D _50" indicates a cumulative 50% particle diameter on a volume basis particle size distribution of, specifically, to the use of a laser diffraction scattering type particle size distribution measuring apparatus for measuring the cumulative particle size distribution of The particle size curve indicates the particle size when the cumulative amount accounts for 50% on a volume basis.

The glass powder of the present invention can be obtained by, for example, using a dry pulverization method or a wet pulverization method to pulverize the glass manufactured in the above-mentioned manner to have the above-mentioned specific particle size distribution.

The method for pulverizing the glass to obtain the glass powder of the present invention is preferably a method for dry-pulverizing glass of an appropriate shape and then wet-pulverizing. Dry pulverization and wet pulverization can be performed using a pulverizer such as a roll mill, a ball mill, or a jet mill. The particle size distribution can be adjusted, for example, by adjusting the pulverizer such as the pulverization time in each pulverization or the size of the ball of the ball mill. In the case of the wet pulverization method, it is preferable to use water as a solvent. After the wet pulverization, moisture is removed by drying or the like to obtain a glass powder. In order to adjust the particle diameter of the glass powder, in addition to the pulverization of the glass, classification may be performed as necessary.

＜ Conductive Paste ＞
The glass of the present invention can be applied to a conductive paste as a glass powder, for example. The conductive paste of the present invention contains the glass powder, the conductive metal powder, and the organic vehicle of the present invention.

The conductive metal powder contained in the conductive paste of the present invention is not particularly limited, and metal powder generally used for electrodes formed on a circuit substrate (including a laminated electronic component) such as a semiconductor substrate or an insulating substrate can be used. Specific examples of the conductive metal powder include powders of Al, Ag, Cu, Au, Pd, and Pt. Among them, Al powder is preferred from the viewpoint of productivity. From the viewpoint of suppressing aggregation and obtaining uniform dispersibility, the particle diameter D _{50 of the} conductive metal powder is preferably 0.3 μm or more and 10 μm or less.

The content of the conductive metal powder in the conductive paste is preferably 63.0% by mass or more and 97.9% by mass or less with respect to the total mass of the conductive paste. If the content of the conductive metal powder is less than 63.0% by mass, the conductive metal powder is likely to be excessively sintered, and glass floats or the like. On the other hand, when the content of the conductive metal powder exceeds 97.9% by mass, there is a possibility that glass precipitates cannot cover the surroundings of the conductive metal powder. In addition, there is a possibility that the adhesion between the electrode and a circuit substrate such as a semiconductor substrate or an insulating substrate may deteriorate. The content of the conductive metal powder with respect to the total mass of the conductive paste is more preferably 75.0% by mass or more and 95.0% by mass or less.

The content of the glass powder in the conductive paste is, for example, preferably 0.1 to 10 parts by mass based on 100 parts by mass of the conductive metal powder. If the content of the glass powder is less than 0.1 parts by mass, there is a possibility that glass precipitates cannot cover the area around the conductive metal powder. In addition, there is a possibility that the adhesion between the electrode and a circuit substrate such as a semiconductor substrate or an insulating substrate may deteriorate. On the other hand, when the content of the glass powder exceeds 10 parts by mass, the conductive metal powder tends to be excessively sintered, and glass floats or the like. The content of the glass powder with respect to 100 parts by mass of the conductive metal powder is more preferably 0.5 parts by mass or more and 5 parts by mass or less.

As the organic vehicle contained in the conductive paste, an organic resin adhesive solution obtained by dissolving an organic resin adhesive in a solvent can be used.

As the organic resin binder used in the organic vehicle, for example, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, ethoxy cellulose, benzyl cellulose, propyl cellulose, and nitrocellulose can be used. Cellulose resins such as cellulose, and acrylic monomers such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, butyl acrylate, and 2-hydroxyethyl acrylate Organic resins, such as acrylic resins, obtained by polymerizing one or more of the polymers.

As a solvent used in an organic vehicle, in the case of a cellulose resin, terpineol, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, and propylene glycol diethyl are preferably used. In the case of acrylic resins, methyl ethyl ketone, terpineol, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, and propylene glycol diethyl are preferably used. Solvents such as acid esters.

The ratio of the organic resin binder to the solvent in the organic vehicle is not particularly limited, and is selected in such a manner that the obtained organic resin binder solution becomes a viscosity capable of adjusting the viscosity of the conductive paste. Specifically, the mass ratio represented by the organic resin binder: solvent is preferably approximately 3:97 to 15:85.

The content of the organic vehicle in the conductive paste is preferably 2% by mass or more and 30% by mass or less with respect to the total amount of the conductive paste. If the content of the organic vehicle is less than 2% by mass, coating properties such as printing of the conductive paste are reduced due to an increase in the viscosity of the conductive paste, and it is difficult to form a good conductive layer (electrode). In addition, if the content of the organic vehicle exceeds 30% by mass, the content ratio of the solid content of the conductive paste becomes low, and it is difficult to obtain a sufficient coating film thickness.

As one aspect of the conductive paste of the present invention, the following conductive pastes can be cited. Among them, at least one metal selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt is contained in the conductive paste. The total mass of the material contains 63.0-97.9% by mass; Moore% expressed in terms of oxide contains V ₂ O ₅ : 6-30%, B ₂ O ₃ : 15-50%, BaO: 10-40%, ZnO: 5 to 30% and Al ₂ O ₃ : 0 to 15% of the glass contains 0.1 to 9.8 parts by mass with respect to 100 parts by mass of the metal; and the organic vehicle contains 2 to 30% by mass with respect to the total mass of the conductive paste. The glass in this aspect is the glass of the present invention. With regard to the glass, metal, and organic vehicle contained in the conductive paste of this aspect, the preferred aspects of the composition, kind, form, content, etc. may be the same as described above.

In the conductive paste of the present invention, in addition to the above-mentioned glass powder, conductive metal powder, and organic vehicle, if necessary, well-known additives can be blended within a limit that does not violate the purpose of the present invention.

Examples of such additives include various inorganic oxides. Specific examples of the inorganic oxide include B ₂ O ₃ , ZnO, SiO ₂ , Al ₂ O ₃ , TiO ₂ , MgO, ZrO ₂ , Sb ₂ O ₃ , and composite oxides thereof. These inorganic oxides have the effect of alleviating the sintering of the conductive metal powder during the calcination of the conductive paste, thereby having the effect of adjusting the joint strength after the calcination. The size of the additives including these inorganic oxides is not particularly limited, and for example, those having a D ₅₀ of 10 μm or less can be suitably used.

The content of the inorganic oxide in the conductive paste is appropriately set according to the purpose, and it is preferably 10% by mass or less, more preferably 7% by mass or less with respect to the glass powder. If the content of the inorganic oxide with respect to the glass powder exceeds 10% by mass, the fluidity of the conductive paste at the time of electrode formation may decrease, which may cause a decrease in bonding strength between the electrode and a circuit substrate such as a semiconductor substrate or an insulating substrate. In addition, in order to obtain a practical blending effect (adjustment of the bonding strength after firing), the lower limit of the content is preferably 0.5% by mass, and more preferably 1.0% by mass.

In the conductive paste, well-known additives can also be added to the conductive paste like a defoamer or dispersant. In addition, the organic vehicle and the additives are generally components that disappear during the formation of the electrode. In the preparation of the conductive paste, a well-known method using a rotary mixer or a grinder, a roll mill, a ball mill, or the like having a stirring blade can be applied.

The coating and firing of the conductive paste on a circuit substrate such as a semiconductor substrate or an insulating substrate can be performed by the same method as the coating and firing in the previous electrode formation. Examples of the coating method include screen printing and a dispensing method. The firing temperature is determined by the type and surface state of the conductive metal powder contained, and a temperature of approximately 500 to 1000 ° C can be exemplified. The firing time is appropriately adjusted according to the shape, thickness, etc. of the electrode to be formed. In addition, between the application and firing of the conductive paste, a drying treatment at 80 to 200 ° C. can also be set.

＜ Solar cell ＞
The solar cell of the present invention includes an electrode formed using the conductive paste of the present invention, and specifically includes an electrode baked on a semiconductor substrate. The solar cell of the present invention preferably includes, for example, an electrode formed using the conductive paste of the present invention as a back electrode of a single-sided light-receiving solar cell such as a PERC solar cell. PERC solar cells generally have an anti-reflection film containing an insulating material on the light receiving surface, and an insulating film containing the same insulating material as the anti-reflection film on the entire surface except for a part of the back surface.

The solar cell of the present invention is a PERC solar cell or the like, and preferably includes an electrode formed using the conductive paste of the present invention as an electrode formed on an insulating film provided on the back surface so as to be in contact with a semiconductor substrate portion. If the conductive paste of the present invention is used, when an insulating film is formed on a semiconductor substrate via an insulating film, the following electrode can be obtained, and the contact with the semiconductor substrate from which the insulating film and the insulating layer are removed is sufficiently ensured, and the The electrode has high reliability due to water resistance and the like.

As described above, the conductive paste of the present invention preferably contains Al powder as the conductive metal powder. That is, the conductive paste of the present invention is preferably used for forming an Al electrode. The conductive paste of the present invention is more preferably used in a case where an insulating film is formed on a semiconductor substrate, for example, a part of the insulating film is removed by a laser to become an insulating film having an opening, and then an opening is formed on the insulating film through the opening. The Al electrode is formed so as to be in contact with the semiconductor substrate portion.

Examples of the Al electrode provided on the insulating film having an opening portion in contact with the semiconductor substrate through the opening portion include, for example, a back electrode of a PERC solar cell using a p-type Si substrate, and an electrode using an n-type Si substrate. PERT (Passivated Emitter, Rear Totally diffused), the back electrode of a solar cell, and a double-sided light-receiving solar cell using an n-type Si substrate or a p-type Si substrate are arranged on the p-layer or p ⁺ -layer side Electrode, one of the back-contact solar cells, etc.

As one embodiment of the solar cell of the present invention, a solar cell including a silicon substrate having a solar light receiving surface; a first insulating film provided on the solar light receiving surface side of the silicon substrate; and a second insulation A film provided on a surface on the opposite side of the solar light receiving surface of the silicon substrate and having at least one opening; a second electrode in contact with the silicon substrate portion through the opening of the second insulating film; and a first electrode that Penetrates a part of the first insulating film and contacts the silicon substrate; the second electrode includes: a metal containing at least one selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt; and an oxide equivalent Molar% indicates that V ₂ O ₅ : 6-30%, B ₂ O ₃ : 15-50%, BaO: 10-40%, ZnO: 5-30%, and Al ₂ O ₃ : 0-15%. glass.

In addition, the opening portion of the second insulating film refers to a portion provided so as to penetrate from the surface of the second insulating film to the surface on the opposite side of the sunlight receiving surface of the silicon substrate. In the following description, the term "opening" is used with the same meaning as above.

The shape of the opening is not particularly limited, and may be linear or circular. In the case of a linear shape, the line width is preferably 30 to 100 μm; in the case of a circular shape, the diameter is preferably 30 to 100 μm. The area of the opening is preferably 1 to 3% of the total area of the surface on the opposite side of the solar light receiving surface of the silicon substrate.

The first electrode preferably contains at least one metal from the group consisting of Al, Ag, Cu, Au, Pd, and Pt, and the metal preferably contains at least Ag. The first insulating film contains insulating materials such as silicon nitride, titanium dioxide, silicon oxide, and aluminum oxide, and preferably contains silicon nitride.

The second electrode preferably contains 90 to 99.9% by mass of the metal and 0.1 to 10% by mass of the glass. The glass contained in the second electrode is the glass of the present invention, and the preferred composition is as described above. The metal contained in the second electrode preferably contains at least Al.

The second insulating film is preferably a multilayer film, and is preferably a multilayer film having an oxide metal containing alumina or silicon oxide in contact with a surface on the opposite side of the sunlight receiving surface of the silicon substrate. And a silicon nitride film is further provided on the metal oxide film.

Hereinafter, a case where an electrode of a p-type Si substrate single-sided light-receiving solar cell is formed using the conductive paste of the present invention will be described as an example. FIG. 1 is a cross-sectional view schematically showing an example of a p-type Si substrate single-sided light-receiving solar cell in which an electrode is formed using the conductive paste of the present invention.

The solar cell 10 shown in FIG. 1 includes a p-type Si substrate 1, an insulating film 2A provided on an upper surface thereof, and an insulating film 2B provided with an opening portion 7 provided on a lower surface, and includes a comprehensive structure formed on the insulating film 2B. The Al electrode 4 which is in contact with the p-type Si substrate portion through the opening 7 and the Ag electrode 3 which is in contact with the p-type Si substrate 1 through a part of the insulating film 2A. The upper surface of the p-type Si substrate 1 has, for example, a concavo-convex structure formed using a wet etching method to reduce light reflectance. Moreover, the top and bottom of the drawings do not necessarily indicate top and bottom when used. Moreover, if necessary, both surfaces of the p-type Si substrate may have a concave-convex structure.

The p-type Si substrate 1 is composed of an n ⁺ layer 1a and a p layer 1b in order from top to bottom, an Al electrode 4 is in contact with the p layer 1b, and an Ag electrode 3 is in contact with the n ⁺ layer 1a. Here, the n ⁺ layer 1a may be formed by doping the surface having the uneven structure described above, for example, doped with P, Sb, As, or the like.

The Al electrode 4 and the Ag electrode 3 are formed as follows using a conductive paste for forming an Al electrode containing a glass powder and an Al powder, and a conductive paste for forming an Ag electrode containing a glass powder and an Ag powder, respectively.

That is, the insulating film 2A provided on the upper surface of the p-type Si substrate 1 exists in the entire surface without a gap before the formation of the Ag electrode 3, and only a part of the Ag electrode 3 coated with the above conductive paste is conductive The paste melts during firing, thereby forming an Ag electrode 3 that penetrates the insulating film 2A and contacts the p-type Si substrate 1.

On the other hand, the insulating film 2B is provided on the entire surface of the lower surface of the p-type Si substrate 1 without gaps. Thereafter, in order to form the Al electrode 4, a part of it is physically removed by a laser to have a configuration having an opening 7. The entire surface of the insulating film 2B having the opening 7 is coated with the above-mentioned conductive paste for forming Al electrodes and calcined, thereby forming the Al electrode 4 covering the entire surface of the insulating film 2B and in contact with the semiconductor portion through the opening 7.

When the Al electrode 4 is formed, the conductive paste for forming the Al electrode is in contact with the p layer 1b of the p-type Si substrate 1 through the opening 7 and then melts during firing, whereby Al diffuses from the Al electrode to p In the layer 1b, an Al-Si alloy layer 5 is formed directly above the Al electrode. Further, a BSF (Back Surface Field) layer 6 is formed directly above the Al-Si alloy layer 5 as a p ⁺ layer.

Among the above, the conductive paste of the present invention can be used as a conductive paste for forming an Ag electrode and a conductive paste for forming an Al electrode, but is particularly preferably used as a conductive paste for forming an Al electrode as described above.

As the conductive paste for forming an Al electrode, the powder of glass of the present invention and the conductive paste of the present invention containing Al powder are used, thereby sufficiently securing the electrode, the insulating film, and the semiconductor substrate when forming an electrode through an insulating film. The Al electrode 4 is sufficiently contacted with the p-type Si substrate 1.

In addition, the insulating film included in the solar cell has an anti-reflection function and can suppress recombination of semiconductor carriers. As the insulating material constituting the film, the above-mentioned insulating materials can be used. The insulating film may be a single-layer film or a multilayer film. In particular, when the conductive paste of the present invention is used to form an electrode through an insulating film having a layer containing silicon nitride and a layer containing aluminum oxide or silicon oxide, the contact between the electrode and the insulating film and a partially formed semiconductor substrate can be sufficiently ensured. High solar cell characteristics, and high reliability such as weather resistance.

In the solar cell of the present invention, especially in the PERC solar cell, the insulating film is partially removed on the back surface within a range where electrical contact can be made. When an electrode containing the glass powder of the present invention is formed, the entire insulating film is formed. An electrode structure is formed on the electrode and a part of the insulating film is removed at the same time, so that an electrode structure for ensuring contact with the semiconductor substrate can be formed. By using the conductive paste, the electrode having a good appearance can be formed, and the obtained electrode has weather resistance such as water resistance, thereby providing a solar cell capable of realizing high reliability and high battery characteristics.
[Example]

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples. Examples 1 to 17 are examples, and examples 18 and 19 are comparative examples.

(Examples 1 to 19)
The glass was made into a thin plate glass by the following method, and glass powder was produced from the thin plate glass. The particle size distribution of the glass powder was measured, and the glass transition temperature of the glass was measured using the glass powder.

＜ Manufacture of glass (thin plate glass) ＞
The raw material powder is prepared and mixed so as to have the composition shown in Table 1. It is melted in a crucible in an electric furnace at 900 to 1200 ° C for 30 minutes to 1 hour to form a glass composed of the composition shown in Table 1. Thin sheet glass.

＜ Manufacture of glass powder ＞
In each example, dry pulverization and wet pulverization were combined and the obtained thin plate glass was pulverized in the following manner to adjust the particle size distribution. The particle size distribution of the obtained glass powder was measured, and the glass transition temperature of the glass was measured using the glass powder.

The glass of Examples 1 to 18 was dry-pulverized with a ball mill, the crushing time was adjusted to obtain a specific D ₅₀ , and finally passed through a 150-mesh sieve to produce glass powder.

For the glass of Example 19, in order to further reduce D ₅₀ within the above specific range, after the above dry pulverization, the glass powder with coarse particles removed was further pulverized with water in a ball mill and the obtained glass powder was used as glass powder. In order to obtain a specific D ₅₀ during the wet pulverization, a ball made of alumina having a diameter of 5 mm was used, and the D ₅₀ was adjusted by the pulverization time. After that, the slurry obtained by the wet pulverization was filtered, and after removing most of the water, it was dried at 130 ° C. with a dryer to adjust the water content to produce a glass powder.

＜ Evaluation ＞
For each glass, the glass transition temperature and the D _{50 of the} glass powder were evaluated by the following methods. The results are shown in Table 1 together with the composition. In addition, in the column of each component of the glass composition, the empty column indicates the content "0%".

(Glass transition temperature)
The obtained glass powder was placed in an aluminum pan, and measured using a differential thermal analysis device TG8110 manufactured by RIGAKU Corporation at a temperature increase rate of 10 ° C / min. The first turning point of the DTA line graph obtained by the measurement was taken as the glass transition temperature (shown as "DTA Tg" in Table 1).

(D ₅₀ )
For the glass of Examples 1 to 18, 0.02 g of 60 cc of mixed glass powder of isopropyl alcohol (IPA) was dispersed by ultrasonic dispersion for 1 minute. A Microtrac measuring machine (laser diffraction, scattering type particle size distribution measuring device) was put into a sample to obtain a value of D ₅₀ . Regarding the glass of Example 19, 0.02 g of a glass powder mixed with 60 cc of water was dispersed by ultrasonic dispersion for 1 minute. A sample was put into a Microtrac measuring machine, and a value of D ₅₀ was obtained.

＜ Manufacturing of conductive paste ＞
The conductive paste for forming Al electrodes containing the glass powders of Examples 1 to 19 prepared as described above was prepared by the following method.

First, 90 parts by mass of diethylene glycol monobutyl ether acetate and 10 parts by mass of ethyl cellulose were mixed and stirred at 85 ° C. for 2 hours to prepare an organic vehicle. Next, 21 parts by mass of the organic vehicle obtained in this manner was mixed with 79 parts by mass of Al powder (spray aluminum powder manufactured by Minalco Corporation: # 800F), followed by kneading with a grinder for 10 minutes. Thereafter, a glass powder was prepared at a ratio of 3 parts by mass to 100 parts by mass of the Al powder, and further kneaded with a grinder for 60 minutes to prepare a conductive paste for forming an Al electrode.

＜ Evaluation ＞
After the electrode was formed using the conductive paste for forming an Al electrode, the appearance and water resistance were confirmed and evaluated as a fired film. In this case, the insulating film is composed of two layers including a silicon nitride layer and an aluminum oxide layer. The results are shown in Table 1.

(Production, appearance and evaluation of water resistance of Al electrode)
Using the conductive paste for forming Al electrodes prepared in the above, an Al electrode was formed on a semiconductor substrate through an insulating film (a two-layer film including a silicon nitride layer and an aluminum oxide layer) in the following manner, and an Al electrode was formed on the Al substrate. The appearance and water resistance of the electrodes were evaluated.

A p-type crystalline Si semiconductor substrate cut to a thickness of 160 μm is used. First, in order to clean the cut surface of the substrate, an approximately minute amount of etching treatment is performed on the surface with hydrofluoric acid. Thereafter, a concave-convex structure is formed on the surface of the crystalline Si semiconductor substrate on the light-receiving surface side of the light to reduce the light reflectance by a wet etching method. Next, an n-type layer is formed on the light receiving surface of the semiconductor substrate by diffusion. P is used as an n-type doping element. Next, an insulating film is formed on the back surface (the surface of the p-type Si substrate) with respect to the n-type layer of the semiconductor substrate. As a material of the insulating film, silicon nitride and aluminum oxide are mainly used. After forming an aluminum oxide layer with a thickness of 10 nm by plasma CVD, a silicon nitride layer is formed thereon with a thickness of 120 nm.

Next, the above-mentioned semiconductor substrate was cut into a size of 30 mm × 30 mm square with a microtome, and the conductive paste for forming Al electrodes obtained above was printed on a 200-mesh screen printing on the insulating film on the back side. Coated as a 20 mm x 20 mm square pattern. Thereafter, an infrared light heating belt furnace was used for firing at a peak temperature of 760 ° C. for 100 seconds to form an Al electrode.

(1) Appearance Evaluation The appearance of the Al electrode having a barrier film (a two-layer film including a silicon nitride layer and an aluminum oxide layer) formed on the p-type layer (back surface) side obtained in the above was evaluated. Thereafter, whether or not the Al electrode can be formed was evaluated with the naked eye based on the following criteria.

○: No peeling or discoloration, and an Al electrode was formed.
×: Peeling or discoloration occurred, and the Al electrode was insufficient.

The results of the appearance evaluation are shown in Table 1. In the whole of the glass of Examples 1 to 17, the Al electrode can be bonded to the insulating layer to form a uniform gray color. Regarding the glass of Example 18, the content of V ₂ O ₅ was high and the adhesiveness was good, but part of the glass was discolored to brown, which was a problem in terms of the appearance as a solar cell. The glass of Example 19 was a glass that did not contain V ₂ O ₅ and had good conductivity, but the Al electrode layer was peeled.

(2) Evaluation of water resistance: The semiconductor substrate having the Al electrode formed on the p-type layer (back surface) side with an insulating film formed thereon was immersed in a beaker containing 50 cc of ion-exchanged water for 30 minutes. Heat to 85 ° C in a thermostatic bath. The state of the Al electrode at this time was evaluated based on the following criteria.

○: Even if immersed for 30 minutes, no foaming or discoloration occurred on the Al electrode.
Δ: During the dipping process, a large number of bubbles adhered to the surface of the Al electrode.
×: During the immersion process, the Al electrode reacted violently with ion-exchanged water, thereby foaming and discoloring.

The results of the water resistance evaluation are shown in Table 1. Even if a small amount of air bubbles adhered to the surface of the Al electrode, the glass of Examples 1 to 17 did not undergo severe reaction or discoloration. The glass of Example 18 produced a large number of bubbles on the surface of the Al electrode. The glass of Example 19 reacted violently with ion-exchanged water to foam, and eventually became brown.

In a solar cell, a resin such as ethylene vinyl acetate (EVA) is generally used to seal and obtain a solar cell element obtained by forming an electrode on a semiconductor substrate as described above. Therefore, moisture easily penetrates into the structure. In addition, if the installation environment of the solar cell is taken into consideration, it is inevitable that moisture will penetrate into the interior during use. Therefore, in order to maintain the reliability of the solar cell, the water resistance of the electrode is an indispensable requirement. For example, in an Al electrode, if the water resistance is low, Al reacts with water to become aluminum hydroxide and cannot function as an electrode, and the characteristics as a solar cell are reduced. In the present invention, since the electrode has water resistance as described above, it can be said that the reliability of the solar cell is sufficiently high.

[Table 1]

＜ Manufacture of solar cells ＞
The conductive pastes for forming Al electrodes and the commercially available conductive pastes for forming Ag electrodes obtained by using the glass powders of Examples 14, 17, 17 and 19 described above were applied to the p-type Si semiconductor substrate 1 as described below. An Al electrode 4 is formed on the non-light-receiving surface as a back electrode, and an Ag electrode 3 is formed on the light-receiving surface as a front electrode, so that a solar cell 10 having the structure shown in FIG. 1 is manufactured.

First, an insulating film 2A including a silicon nitride layer and a two-layer film including an aluminum oxide layer and a silicon nitride layer in this order are formed on the light-receiving surface side and the non-light-receiving surface side of the Si semiconductor substrate, respectively. Its insulating film 2B. Furthermore, an opening 7 is formed on the insulating film 2B by a laser at a specific portion. Next, on the entire surface of the non-light-receiving surface side, that is, the surface of the insulating film 2B, and the surface of the semiconductor substrate facing the opening 7 by removing a portion of the insulating film 2B by laser, the above-mentioned Example 14 was applied by screen printing. The conductive paste for forming an Al electrode obtained from the glass powder of Examples 17 and 19 was dried at 120 ° C.

Next, the entire surface of the insulating film 2A of the Si semiconductor substrate 1 was coated linearly with a conductive paste for forming an Ag electrode by screen printing. Thereafter, an infrared light heating belt furnace was used for firing at a peak temperature of 760 ° C. for 100 seconds to form a front Ag electrode 3 and a back Al electrode 4 to complete the solar cell 10. The surface Ag electrode 3 is formed through the insulating film 2A.

(Measurement of conversion efficiency of solar cells)
Using a solar simulator, the conversion efficiency of a solar cell manufactured using the conductive paste for forming an Al electrode containing the glass powder of each of the above examples was measured. Specifically, a solar cell is installed in a solar simulator, and a current-voltage characteristic is measured in accordance with JIS C8912 (1998) based on a reference solar ray of a spectral characteristic of AM1.5G to derive a conversion efficiency of each solar cell. The results of the obtained conversion efficiency are shown in Table 2.

The symbols in Table 2 have the following meanings.
Isc (A): short-circuit current
Voc (mV): open voltage
FF (%): curve factor
Eff (%): Conversion efficiency

[Table 2]

As can be seen from Table 2, when the glass powders of Examples 14 and 17 were used, FF was 80% or more, and conversion efficiency Eff of 20% or more was obtained. As a PERC solar cell, it can fully exhibit its performance. On the other hand, according to Table 2, when the glass powder of Example 19 was used, the Al electrode was peeled after the electrode was formed, and the conversion efficiency of the solar cell could not be measured.

In the case of using the glass powder of Examples 14 and 17, on the basis of maintaining a good appearance, it can maintain a high FF, and an insulating film without an aluminum oxide layer and a silicon nitride layer on the non-light-receiving surface side. Compared with solar cells, PERC solar cells can achieve higher Isc and Voc, and Eff exceeds 20%. In the case of using the glass powder of Example 19 as a comparative example, the PERC solar cell has a poor appearance and cannot obtain long-term reliability. In contrast, when the glass powder of Examples 14 and 17 is used as an example As a PERC solar cell, it has a good appearance and can simultaneously maintain contact with the insulating film and the Si semiconductor substrate in the non-light-receiving surface side, which is excellent in terms of obtaining long-term reliability.

From Tables 1 and 2, it is clear that compared with the glass and glass powders of Examples 18 and 19 as comparative examples, the glass and glass powder of Examples 1 to 17 as examples are suitable for forming electrodes for solar cells.

Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes or modifications can be made without departing from the spirit and scope of the present invention.
This application is based on Japanese Patent Application No. 2018-002487 filed on January 11, 2018, the contents of which are incorporated herein by reference.

1‧‧‧ p-type Si semiconductor substrate

1a‧‧‧n ⁺ floor

1b‧‧‧p layer

2A‧‧‧Insulation film

2B‧‧‧Insulation film

3‧‧‧Ag electrode

4‧‧‧Al electrode

5‧‧‧Al-Si alloy layer

6‧‧‧BSF floor

7‧‧‧ opening

10‧‧‧ solar cell

FIG. 1 is a diagram schematically showing a cross section of an example of a p-type Si substrate single-sided light-receiving solar cell in which an electrode is formed using the conductive paste of the present invention.

Claims (18)

A glass characterized in that it is expressed in mole% in terms of oxides and contains V ₂ O ₅ : 6-30%, B ₂ O ₃ : 15-50%, BaO: 10-40%, and ZnO: 5-30 % And Al ₂ O ₃ : 0 to 15%. For example, the glass of claim 1 is expressed in terms of mole% in terms of oxides, and further contains at least one selected from SiO ₂ , SrO, MoO ₃ and WO ₃ in a total of 0 to 10%. The glass of claim 1 or 2, wherein the glass transition temperature is 380-550 ° C. A glass powder comprising the glass according to any one of claims 1 to 3, and when a 50% particle diameter based on a volume basis in a cumulative particle size distribution is set to D ₅₀ , D ₅₀ is 0.8 to 6.0 μm. A conductive paste containing the glass powder, the conductive metal powder, and the organic vehicle according to claim 4. A solar cell includes an electrode formed using a conductive paste as claimed in claim 5. A conductive paste, characterized in that it contains a metal, glass, and an organic vehicle, and the metal contains 63.0 to 97.9% by mass relative to the total mass of the conductive paste, and is selected from the group consisting of Al, Ag, and Cu At least one of the group consisting of Au, Pd, and Pt; the glass contains 0.1 to 9.8 parts by mass relative to 100 parts by mass of the metal, expressed in mole% in terms of oxides, and contains V ₂ O ₅ : 6 to 30%, B ₂ O ₃ : 15-50%, BaO: 10-40%, ZnO: 5-30%, and Al ₂ O ₃ 0-15%; and the total amount of the organic vehicle relative to the conductive paste Mass contains 2 to 30% by mass. For example, the conductive paste according to claim 7, wherein the mole is expressed in terms of oxides, and the glass further contains at least one selected from SiO ₂ , SrO, MoO ₃ and WO ₃ in a total amount of 0 to 10%. The conductive paste of claim 7 or 8, wherein the glass transition temperature of the glass is 380 to 550 ° C. The conductive paste according to any one of claims 7 to 9, wherein the glass is a glass particle having a D ₅₀ of 0.8 to 6.0 μm when a 50% particle diameter on a volume basis in a cumulative particle size distribution is set to D ₅₀ . The conductive paste according to any one of claims 7 to 10, wherein the metal contains Al. The conductive paste according to any one of claims 7 to 11, wherein the organic vehicle is an organic resin adhesive solution obtained by dissolving an organic resin adhesive in a solvent; The organic resin binder is selected from the group consisting of acrylic resin, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, ethoxy cellulose, benzyl cellulose, propyl cellulose, and nitrocellulose. At least one of the composition group, the acrylic resin is selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, butyl acrylate, and acrylic acid. Obtained by polymerizing at least one species of a group consisting of 2-hydroxyethyl esters; and The solvent contains at least one selected from the group consisting of terpineol, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol diacetate, and methyl ethyl ketone. Species. A solar cell includes: a silicon substrate having a solar light receiving surface; a first insulating film provided on the solar light receiving surface side of the silicon substrate; and a second insulating film provided on the silicon substrate. The surface on the opposite side of the sunlight receiving surface has at least one opening; a second electrode that is in contact with the silicon substrate portion through the opening of the second insulating film; and a first electrode that penetrates the first A part of the insulating film is in contact with the silicon substrate; and the second electrode includes: a metal containing at least one selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt; and an oxide equivalent Molar% indicates that V ₂ O ₅ : 6-30%, B ₂ O ₃ : 15-50%, BaO: 10-40%, ZnO: 5-30%, and Al ₂ O ₃ : 0-15%. glass. The solar cell according to claim 13, wherein the second electrode includes 90 to 99.9% by mass of the metal and 0.1 to 10% by mass of the glass. The solar cell according to claim 13 or 14, wherein the metal contained in the second electrode contains at least Al. The solar cell according to any one of claims 13 to 15, wherein the first electrode includes a metal containing at least Ag. The solar cell according to any one of claims 13 to 16, wherein the first insulating film contains silicon nitride. The solar cell according to any one of claims 13 to 17, wherein the second insulating film includes an oxide metal containing alumina or silicon oxide in contact with a surface on the opposite side of the sunlight receiving surface of the silicon substrate. And a silicon nitride film on the metal oxide film.