JP2019119660A - Glass, glass powder, conductive paste and solar battery - Google Patents

Abstract

To provide a glass capable of efficiently securing contact with an insulation film and a semiconductor substrate when an electrode is formed via the insulation film on the semiconductor such as a solar battery, maintaining efficient credibility, and enhancing conversion efficiency of the solar battery, and a glass powder consisting of the glass, a conductive paste containing the glass power, and the solar battery of which conversion efficiency is enhanced by using the conductive paste.SOLUTION: There are provide a glass containing, by mol% in terms of oxide, VOof 6 to 30%, BOof 15 to 50%, BaO of 10 to 40%, ZnO of 5 to 30%, and AlOof 0 to 15%, and a glass powder consisting of the glass and having Dof 0.8 to 6.0 μm, wherein Dis 50% particle diameter based on volume in a cumulative particle size distribution.SELECTED DRAWING: Figure 1

Description

  The present invention relates to glass, glass powder, conductive paste and a solar cell, and in particular, a glass suitable for forming an electrode of a solar cell, a glass powder, a conductive paste using the same, and an electrode formed of the conductive paste. It relates to a solar cell.

  BACKGROUND ART Conventionally, electronic devices in which a conductive layer serving as an electrode is formed on a semiconductor substrate such as silicon (Si) have been used for various applications. In the conductive layer to be the electrode, a conductive paste in which conductive metal powder such as aluminum (Al), silver (Ag), copper (Cu) and glass powder are dispersed in an organic vehicle is applied on a semiconductor substrate It forms by baking at the temperature required for electrode formation.

  Thus, when forming an electrode on a semiconductor substrate, an insulating film is formed in the whole surface in which an electrode of a semiconductor substrate is formed, and a pattern-like electrode partially penetrates an insulating film, and it is a semiconductor substrate. It may be formed to be in contact. For example, in a solar cell, an antireflective film is provided on a semiconductor substrate to be a light receiving surface, and electrodes are provided in a pattern on the semiconductor substrate. The antireflective film is intended to reduce the surface reflectance and enhance the light receiving efficiency while maintaining a sufficient visible light transmittance, and is usually made of an insulating material such as silicon nitride, titanium dioxide, silicon dioxide or aluminum oxide. Configured In addition, in a solar cell such as PERC (Passivated Emitter and Rear Contact), a passivation film made of an insulating material similar to the anti-reflection film is also provided on the back surface, and an electrode is partially formed on the passivation film on the semiconductor substrate. It is formed in the form which contacts.

  Here, in the formation of the electrode, it is essential to form the electrode in contact with the semiconductor substrate, and in the light receiving surface, the portion corresponding to the pattern of the electrode is removed and the portion from which the insulating film is removed The electrodes are formed on the In addition, on the back surface of the PERC solar cell or the like, the insulating film is partially removed to the extent that electrical contact is possible, and an electrode is formed on the entire back surface.

  As a method of partially removing the insulating layer, it is physically removed by a laser or the like, and an electrode is formed in a portion where the insulating layer is removed, whereby the semiconductor comes into contact with the semiconductor and operates as a solar cell . In the conventional solar cell structure, when the back surface electrode is in direct contact with the semiconductor substrate of Si or the like on the entire surface to form an electrode, the entire surface of the back surface operates to operate as a solar cell. On the other hand, in the structure of a PERC solar cell or the like, the area of the portion where the insulating film is removed is about 1 to 3% of the entire back surface, and most of the back surface side electrode is formed on the insulating film.

The above-described technique for forming an electrode on a semiconductor substrate is also applied to the formation of an electrode on a pn junction type semiconductor substrate in a solar cell. As a conductive paste containing such glass powder, for example, Patent Document 1 describes a paste for an electronic device electrode. Patent Document 1 describes a glass containing vanadium oxide as a main component capable of forming an electrode excellent in durability against corrosive gas and the like, and as a specific glass composition, V ₂ O ₅ is 26 in oxide conversion. A lead-free glass containing 7 mol% ZnO, 22.2 mol% ZnO, 17.8 mol% BaO, 11.0 mol% Sb ₂ O ₃ and 22.3 mol% P ₂ O ₅ is disclosed There is. However, the glass described in Patent Document 1 does not sufficiently contain B ₂ O _3, and boron, which is a majority carrier, is sufficiently contained in the Si substrate particularly when the back electrode of the solar cell in the p-type semiconductor substrate is formed. There is a problem that the electrical characteristics deteriorate because the diffusion can not be performed.

In Patent Document 2, as a coating glass, 4.4 mol% of V ₂ O ₅ , 9.2 mol% of B ₂ O ₃ , 26.5 mol% of ZnO and 5.2 of BaO in terms of oxide are calculated. Glass containing 10.2% by mole of Al ₂ O ₃ , 30.6% by mole of SiO ₂ , 6.0% by mole of MgO, 7.1% by mole of CaO and 0.8% by mole of SrO It is disclosed. However, the glass described in Patent Document 2 has a low V ₂ O ₅ content when used in electrode formation, and a high SiO ₂ content, so the glass softening point rises and a sufficient glass at the time of firing necessary for electrode formation There was a problem that did not flow.

In Patent Document 3, as lead-free glass for plasma display panel partitions, 17.5 mol% of V ₂ O ₅ , 15.2 mol% of B ₂ O ₃ , 26.0 mol% of ZnO, BaO in terms of oxide conversion 6.9 mol%, Al ₂ O ₃ 5.2 mol%, K ₂ O 5.6 mol%, CaO 9.4 mol%, TiO ₂ 6.6 mol%, P ₂ O ₅ A glass containing 7.5 mole percent is disclosed. However, the glass described in Patent Document 3 has a low content of BaO when used for forming an electrode on the back side of a PERC solar cell or the like through an insulating film, so that the contact resistance component between the electrode and the semiconductor substrate is increased. There is a problem that the characteristic is lowered.

In Patent Document 4, as lead-free low melting point glass, 16.3 mol% of V ₂ O ₅ , 18.0 mol% of B ₂ O ₃ , 34.1 mol% of ZnO, and 13 BaO in terms of oxides are calculated. Disclosed is a glass containing 8 mol% Al ₂ O ₃ 3.6 mol% TeO ₂ 4.0 mol% TiO ₂ 6.0 mol% TiO ₂ and 4.1 mol% MoO ₃ . However, the glass described in Patent Document 4 has a high ZnO content and a low glass transition point when used to form an electrode on the back side of a PERC solar cell or the like via an insulating film, so the glass is an insulating film when forming the electrode. And there was a problem that the electrode appearance became worse.

Patent No. 5754090 JP-A-3-126639 JP, 2006-8496, A Japanese Patent Application Laid-Open No. 6-263478

  With regard to vanadium-based glasses used for forming electrodes of solar cells, many techniques for improving the formability of the electrodes have been developed as in Patent Document 1. However, particularly in a solar cell such as PERC, even if the composition of the glass of the glass powder used for electrode formation and the particle size distribution of the powder are adjusted, at present, the reliability can be sufficiently maintained along with the electrode formation. In addition, a technology for improving the conversion efficiency of the solar cell by lowering the electrical resistance between the electrode and the semiconductor substrate is under development.

  The present invention relates to a glass used for forming an electrode, which has a good appearance when forming an electrode on a semiconductor substrate such as a solar cell via an insulating film, and ensures sufficient contact with the insulating film and the semiconductor substrate. It is an object of the present invention to provide a glass capable of forming an electrode capable of maintaining sufficient reliability by having water resistance etc. and capable of improving the conversion efficiency of a solar cell. Another object of the present invention is to provide a glass powder comprising the glass, a conductive paste containing the glass powder, and a solar cell with improved conversion efficiency by using the conductive paste.

The present invention provides a glass, a glass powder, a conductive paste and a solar cell of the following configuration.
[1] 6 to 30% of V ₂ O ₅ , 15 to 50% of B ₂ O ₃ , 10 to 40% of BaO, 5 to 30% of ZnO, and Al ₂ O in terms of mol% of oxide conversion A glass comprising 0 to 15% of ₃ .
[2] The glass according to [1], further containing 0 to 10% in total of at least one selected from SiO ₂ , SrO, MoO ₃ and WO _{3 in} terms of mole percentage in terms of oxide.
[3] The glass according to [1] or [2], which has a glass transition temperature of 380 to 550 ° C.
[4] When the 50% particle size based on volume in cumulative particle size distribution is D ₅₀ , D ₅₀ is 0.8 to 6.0 μm and it is made of the glass according to any one of [1] to [3] Glass powder.
[5] A conductive paste comprising the glass powder according to [4], the conductive metal powder, and an organic vehicle.
[6] A solar cell comprising an electrode formed using the conductive paste according to [5].
[7] A conductive paste containing metal, glass, and an organic vehicle, wherein the metal is contained in an amount of 63.0-97.9 mass% with respect to the total mass of the conductive paste, and Al, Ag, Cu, Au And at least one selected from the group consisting of Pd and Pt, wherein the glass is contained in an amount of 0.1 to 9.8 parts by mass with respect to 100 parts by mass of the metal, and in terms of mol% in terms of oxide, 6 to 30% ₂ O ₅ , 15 to 50% B ₂ O ₃ , 10 to 40% BaO, 5 to 30% ZnO, and 0 to 15% Al ₂ O ₃ , the organic vehicle comprising A conductive paste comprising 2 to 30% by mass with respect to the total mass of the conductive paste.
[8] The conductive paste according to [7], wherein the glass further contains 0 to 10% in total of at least one selected from SiO ₂ , SrO, MoO ₃ and WO _{3 in} terms of mole percentage in terms of oxide.
[9] The conductive paste according to [7] or [8], wherein the glass transition temperature of the glass is 380 to 550 ° C.
[10] The glass is a 50% particle diameter on a volume basis when the _{D 50} in a cumulative particle size _{distribution,} one _{D 50} is glass particles 0.8~6.0μm of [7] to [9] Electrically conductive paste described in.
[11] The conductive paste according to any one of [7] to [10], wherein the metal contains Al.
[12] The organic vehicle is an organic resin binder solution in which an organic resin binder is dissolved in a solvent, and the organic resin binder is methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, butyl acrylate, and 2- At least one selected from the group consisting of an acrylic resin obtained by polymerizing one or more selected from the group consisting of hydroxyethyl acrylate, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, oxyethyl cellulose, benzyl cellulose, propyl cellulose, and nitrocellulose And the solvent comprises terpineol, butyl diglycol acetate, ethyl diglycol acetate, propylene glycol diacetate, and Comprising at least one selected from the group consisting of ethyl ketone [7] to [11] a conductive paste according to any one of.
[13] 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 surface of the silicon substrate opposite to the solar light receiving surface A second insulating film provided with at least one opening, a second electrode partially in contact with the silicon substrate via the opening of the second insulating film, and the first electrode A solar cell comprising: a first electrode penetrating a portion of an insulating film and contacting the silicon substrate, wherein the second electrode is made of a group consisting of Al, Ag, Cu, Au, Pd and Pt. 6 to 30% of V ₂ O ₅ , 15 to 50% of B ₂ O ₃ , 10 to 40% of BaO, and 5% of ZnO in terms of mol% of oxide conversion and a metal containing at least one selected a glass containing 30%, and _Al 2 _{O 3} 0 to 15%, Solar cells, characterized in that the Ranaru.
[14] The solar cell according to [13], wherein the second electrode contains 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 contains a metal containing at least Ag.
[17] The solar cell according to any one of [13] to [16], wherein the first insulating film is made of silicon nitride.
[18] A metal oxide film of aluminum oxide or silicon oxide in which the second insulating film is in contact with the surface of the silicon substrate opposite to the solar light receiving surface, and a silicon nitride film on the metal oxide film. The solar cell in any one of [13]-[17] provided with.

  When the glass of the present invention and the glass powder made of the glass are used together with a conductive component in a conductive paste, an insulating film and a semiconductor can be formed when forming an electrode through an insulating film on a semiconductor substrate such as a solar cell. A sufficient contact with the substrate can be secured, and it is a powder of boron-containing glass and can diffuse boron contained in the glass at the time of electrode formation into, for example, the p-type layer of the semiconductor substrate Thus, a good p + layer can be formed, thereby improving the conversion efficiency of the solar cell.

  Furthermore, by using the glass of the present invention for forming an electrode through an insulating film on a semiconductor substrate such as a solar cell, it is possible to suppress the occurrence of appearance defects such as electrode peeling and discoloration during electrode formation. In addition, the formed electrode can be provided with high reliability by having water resistance and the like, and can sufficiently cope with cases where it is necessary to operate a semiconductor such as a solar cell under any environment. .

  In the present invention, by containing the glass powder, a conductive paste capable of improving the conversion efficiency of the solar cell along with the formation of an electrode using the same, and a solar whose conversion efficiency is improved by using the conductive paste It is possible to provide a battery.

It is the figure which showed typically the cross section of an example of the p-type Si substrate single-sided light reception type solar cell in which the electrode was formed using the electrically conductive paste of this invention.

Hereinafter, embodiments of the present invention will be described.
<Glass>
The glass of the present invention is 6 to 30% of V ₂ O ₅ , 15 to 50% of B ₂ O ₃ , 10 to 40% of BaO, 5 to 30% of ZnO, and mol% in terms of oxide. the al ₂ O ₃ containing 0-15%. In the following description, unless otherwise noted, the indication of "%" in the content of each component of glass is the molar percentage indication in terms of oxide. In the present specification, upper and lower limits are included in "-" representing a numerical range.

  The content of each component in the glass of the present invention is a result of inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis or electron probe micro analyzer (EPMA) analysis of the obtained glass. It is obtained from

In the glass of the present invention, V ₂ O ₅ can improve the softening and fluidity of the glass, and in the electrode obtained using the conductive paste containing the glass, the contact with the insulating film and the semiconductor substrate can be obtained. , An essential ingredient. Hereinafter, in the description of the glass component, "conductive paste" is "conductive paste containing the glass of the present invention", "electrode" is "electrode obtained using conductive paste containing the glass of the present invention" Means Further, when V ₂ O ₅ in the glass lowers the glass transition point, the contact with the insulating film of the electrode and the semiconductor substrate can be easily adjusted. As a result, the reaction between the electrode and the semiconductor substrate thereafter can be promoted, the contact resistance can be lowered, and the adhesion between the electrode and the insulating film can be enhanced.

V ₂ O ₅ can further enhance the wettability with the conductive metal in the conductive paste, and can lower the electrical resistance of the electrode by enhancing the bonding between the conductive metals. In addition, the formation of an oxide film on the surface of the conductive metal can be adjusted at the time of electrode formation, and the weather resistance can be adjusted. The effect is particularly high when the conductive metal is Al.

The glass of the present invention contains V ₂ O ₅ in a proportion of 6% to 30%. When the content of V ₂ O ₅ is less than 6%, the glass softening point is increased, the fluidity is reduced, and the contact between the electrode and the insulating film and the semiconductor substrate, and the bonding of conductive metals in the electrode Will not be enough. The content of V ₂ O ₅ is preferably 7% or more, more preferably 8% or more. On the other hand, when the content of V ₂ O ₅ exceeds 30%, the glass reacts too much with the insulating film to discolor the electrode obtained or oxidize the conductive metal excessively, resulting in an increase in electrical resistance. I'm sorry. The content of V ₂ O ₅ is preferably 29% or less, more preferably 28% or less.

B ₂ O ₃ is an essential component in the glass of the present invention. B ₂ O ₃ has a function of improving the softening flowability of glass and improving the contact between the electrode and the insulating film and the semiconductor substrate. _Further, B 2 _{O 3} is a component for stabilizing the glass.

Furthermore, B ₂ O ₃ can promote direct reaction between the semiconductor substrate and the glass in the conductive paste by flowing the glass. Thus, for example, the semiconductor substrate can be a pn junction type Si semiconductor substrate, and glass can form ap ⁺ layer or an n ⁺ layer in contact with an electrode. For example, when forming the electrode in contact with the p ⁺ layer can promote the diffusion of the p ⁺ layer of B ₂ O ₃ is a component that glass contains as B, to form a better p ⁺ layer be able to.

The glass of the present invention contains B ₂ O ₃ in a proportion of 15% to 50%. When the content of B ₂ O ₃ is less than 15%, for example, the conversion efficiency in a solar cell may not be able to be increased because B can not sufficiently diffuse into the Si semiconductor substrate at the time of electrode formation. Furthermore, B ₂ O ₃ is a network structure forming component of glass, and if it is less than 15%, it can not be vitrified. The content of B ₂ O ₃ is preferably 18% or more, more preferably 20% or more. On the other hand, when the content of B ₂ O ₃ exceeds 50%, the weather resistance is deteriorated. The content of B ₂ O ₃ is preferably 48% or less, more preferably 45% or less.

  In the glass of the present invention, BaO is an essential component to lower the contact resistance component between the electrode and the semiconductor substrate. BaO can also be stabilized as a glass component and as a modified oxide. 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 component between the electrode and the semiconductor substrate may increase during the formation of the electrode, so that, for example, the conversion efficiency of the solar cell may not be increased. In addition, vitrification becomes difficult. The content of BaO is preferably 13% or more, more preferably 15% or more. When the content of BaO exceeds 40%, glass can not be obtained due to crystallization. The content of BaO is preferably 35% or less, more preferably 30% or less.

  ZnO is an essential component in the glass of the present invention. ZnO is a component that can suppress the crystallization of glass and improve the reactivity of the glass and the insulating film on the semiconductor substrate such as a Si substrate or the Si substrate. The glass of the present invention contains ZnO at a ratio of 5% to 30%. If the content of ZnO is less than 5%, the reactivity between the glass and the insulating film or the Si substrate on the semiconductor substrate such as the Si substrate is deteriorated, the bonding strength may be weakened, or the electrode and the semiconductor substrate Electrical resistance may increase. The content of ZnO is preferably 6% or more. When the content of ZnO exceeds 30%, the glass reacts too much with the insulating film at the time of electrode formation, and the appearance of the electrode may be deteriorated or the weather resistance such as water resistance may be 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 increasing the weather resistance. Further, it is possible to stabilize the glass by the inclusion of Al ₂ O _3. 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, more preferably 5% or more. If the content of Al ₂ O ₃ exceeds 15%, the glass transition temperature rises, and it becomes impossible to flow the glass at the time of sintering. The content of Al ₂ O ₃ is preferably 13% or less.

The glass of the present invention preferably further contains 0 to 10% in total of at least one selected from SiO ₂ , SrO, MoO ₃ and WO ₃ . When the glass of the present invention contains these components, the glass can be stabilized and weatherability can be improved. The content of SiO ₂ , SrO, MoO ₃ and WO ₃ is preferably 0.5% or more in total. SiO ₂ , SrO, MoO ₃ and WO ₃ may not vitrify if they exceed 10% in total. The total content of SiO ₂ , SrO, MoO ₃ and WO ₃ is more preferably 8% or less.

The glass of the present invention may contain other optional components other than these. As other optional components, specifically, 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 , Fe _{2 O 3, CuO, Sb 2 O} 3, SnO 2, MnO, MnO 2, CeO 2, usually various oxide components used in the glass of the TiO ₂ and the like.

  These other optional components may be used alone or in combination of two or more depending on the purpose. The content of the other optional components is preferably 64% or less, more preferably 60% or less, still more preferably 50% or less, and still more preferably 40% or less. Furthermore, 50% or less is preferable and 40% or less of the total content of other arbitrary components is more preferable.

  The glass of the present invention preferably has a glass transition temperature of 380 ° C. or more and 550 ° C. or less. When the glass transition temperature is less than 380 ° C., the fluidity of the glass becomes higher than necessary during sintering. When the flowability of the glass is too high, for example, when used for a conductive paste, the conductive component and the glass may be separated, and sufficient electrical conductivity may not be provided in the obtained electrode. In addition, since the glass transition point is low, the glass reacts too much with the insulating film at the time of electrode formation, and the electrode appearance is deteriorated. When the glass transition temperature exceeds 550 ° C., the glass can not flow sufficiently during sintering, and the characteristics may be unstable. The glass transition temperature is more preferably 390 ° C. or more and 520 ° C. or less.

  In the present invention, the glass transition temperature is obtained by determining the first inflection point of the DTA chart obtained by measurement at a temperature rising rate of 10 ° C./min with a differential thermal analysis (DTA) apparatus TG8110 manufactured by RIGAKU Co., Ltd. .

  The method for producing the glass of the present invention is not particularly limited. For example, it can manufacture by the method shown below.

  First, prepare the raw material mixture. A raw material will not be specifically limited if it is a raw material used for manufacture of normal oxide glass, An oxide, carbonate, etc. can be used. In the obtained glass, the kind and ratio of the raw materials are appropriately adjusted so as to be in the above composition range to obtain a raw material mixture.

  The feed mixture is then heated in a known manner to obtain a melt. 800-1400 degreeC is preferable and, as for the temperature (melting temperature) which heat-melts, 900-1300 degreeC is more preferable. The heating and melting time is preferably 30 to 300 minutes.

  Thereafter, the melt is cooled and solidified to obtain the glass of the present invention. The cooling method is not particularly limited. It is also possible to employ a method of quenching by a roll-out machine, a press machine, dropping to a cooling liquid or the like. The resulting glass is preferably completely amorphous, ie it has a degree of crystallinity of 0%. However, as long as the effects of the present invention are not impaired, a crystallized portion may be included.

  The glass of the present invention thus obtained may be in any form. For example, block shape, plate shape, thin plate shape (flakes shape), powder shape etc. may be sufficient.

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

<Glass powder>
The glass powder of the present invention comprises the glass of the present invention and preferably has a D ₅₀ of 0.8 μm or more and 6.0 μm or less. Scope of this D ₅₀ is a particularly preferred range for use in the conductive paste. By D ₅₀ is 0.8μm or more, dispersibility when used as a conductive paste is improved. Further, D ₅₀ is that it is less 6.0 .mu.m, for places where there are no glass powder around the conductive metal powder is less likely to occur, adhesion between the electrode and the semiconductor substrate or the like is further improved. In this case, D ₅₀ is more preferably 1.0 μm or more. D ₅₀ is more preferably 5.0 μm or less.

In the present specification, “D ₅₀ ” indicates the volume-based 50% particle size in the cumulative particle size distribution, and specifically, the particle size distribution measured using a laser diffraction / scattering type particle size distribution measuring apparatus In the cumulative particle size curve, it represents the particle size when the integrated amount occupies 50% by volume.

  The glass powder of the present invention can be obtained by grinding the glass produced as described above so as to have the above-mentioned specific particle size distribution by, for example, a dry grinding method or a wet grinding method.

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

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

As the conductive metal powder contained in the conductive paste of the present invention, metal powders generally used for electrodes formed on circuit substrates (including laminated electronic components) such as semiconductor substrates and insulating substrates are used without particular limitation. . Specific examples of the conductive metal powder include powders of Al, Ag, Cu, Au, Pd, Pt and the like, and among these, Al powder is preferable in terms of productivity. Aggregation is suppressed, and the particle diameter of the conductive metal powder from the viewpoint of uniform dispersibility is obtained D ₅₀ is preferably 0.3μm or more 10μm or less.

  The content of the conductive metal powder in the conductive paste is preferably 63.0% by mass to 97.9% by mass with respect to the total mass of the conductive paste. When the content of the conductive metal powder is less than 63.0% by mass, the conductive metal powder is further sintered to easily cause glass floating and the like. On the other hand, if the content of the conductive metal powder exceeds 97.9% by mass, the periphery of the conductive metal powder may not be covered with the glass precipitate. In addition, the adhesion between the electrode and the circuit substrate such as the semiconductor substrate or the insulating substrate may be deteriorated. The content of the conductive metal powder relative to the total mass of the conductive paste is more preferably 75.0% by mass to 95.0% by mass.

  The content of the glass powder in the conductive paste is preferably, for example, 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the conductive metal powder. If the content of the glass powder is less than 0.1 parts by mass, the periphery of the conductive metal powder may not be covered with the glass precipitate. In addition, the adhesion between the electrode and the circuit substrate such as the semiconductor substrate or the insulating substrate may be deteriorated. On the other hand, when the content of the glass powder exceeds 10 parts by mass, the conductive metal powder is further sintered, and the glass floating and the like are easily generated. The content of the glass powder relative 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 binder solution obtained by dissolving an organic resin binder in a solvent can be used.

  Examples of the organic resin binder used for the organic vehicle include cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, oxyethyl cellulose, benzyl cellulose, propyl cellulose, nitrocellulose, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, An organic resin such as an acrylic resin obtained by polymerizing one or more acrylic monomers such as butyl acrylate and 2-hydroxyethyl acrylate is used.

  As solvents used for the organic vehicle, solvents such as terpineol, butyl diglycol acetate, ethyl diglycol acetate, propylene glycol diacetate and the like in the case of a cellulose resin are methyl ethyl ketone, terpineol and butyl diglycol acetate in the case of an acrylic resin. Solvents such as ethyl diglycol acetate and propylene glycol diacetate are preferably used.

  The ratio of the organic resin binder to the solvent in the organic vehicle is not particularly limited, but is selected such that the resulting organic resin binder solution has a viscosity capable of adjusting the viscosity of the conductive paste. Specifically, the weight ratio of organic resin binder to solvent is preferably about 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. When the content of the organic vehicle is less than 2% by mass, the viscosity of the conductive paste is increased, so that the coating property such as printing of the conductive paste is reduced, and it becomes difficult to form a good conductive layer (electrode). Moreover, when content of an organic vehicle exceeds 30 mass%, the content rate of solid content of an electrically conductive paste will become low, and it will become difficult to obtain sufficient application | coating film thickness.

As one aspect of the conductive paste of the present invention, a metal containing at least one selected from the group consisting of Al, Ag, Cu, Au, Pd and Pt is 63.0 to 97.9 mass based on the total mass of the conductive paste. %, And 6 to 30% of V ₂ O ₅ , 15 to 50% of B ₂ O ₃ , 10 to 40% of BaO, 5 to 30% of ZnO, and Al ₂ O _{3 in} terms of mol% of oxide conversion And a conductive paste containing 0.1 to 9.8 parts by mass of a glass containing 0 to 15% with respect to 100 parts by mass of the metal and 2 to 30% by mass of an organic vehicle based on the total mass of the conductive paste. The glass in this aspect is the glass of the present invention. With respect to the glass, metal and organic vehicle contained in the conductive paste of the present embodiment, preferable embodiments such as the composition, type, form, content and the like can be the same as described above.

  In the conductive paste of the present invention, in addition to the above-described glass powder, conductive metal powder, and organic vehicle, known additives can be blended as necessary and within limits not against the object of the present invention. .

As such an additive, various inorganic oxides are mentioned, for example. 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 reducing the sintering of the conductive metal powder when firing the conductive paste, and thereby have the function of adjusting the bonding strength after firing. The size of the additive made of these inorganic oxides is not particularly limited, but, for example, one 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, but is preferably 10% by mass or less, more preferably 7% by mass or less, based on the glass powder. When 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 be reduced, and the adhesion strength between the electrode and the circuit substrate such as a semiconductor substrate or insulating substrate may be reduced. There is. Moreover, in order to obtain a practical blending effect (adjustment of bonding strength after firing), the lower limit value of the content is preferably 0.5% by mass, more preferably 1.0% by mass.

  You may add an additive well-known with a conductive paste to a conductive paste like a defoamer or a dispersing agent. In addition, the said organic vehicle and these additives are components which lose | disappear in the process of electrode formation normally. For preparation of the conductive paste, a known method using a rotary mixer equipped with a stirring blade, a grinder, a roll mill, a ball mill or the like can be applied.

  The application 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 application and firing in the conventional electrode formation. The coating method may, for example, be screen printing or dispensing. Although a calcination temperature is based on the kind of conductive metal powder to contain, a surface state, etc., the temperature of about 500-1000 degreeC can be illustrated. The firing time is appropriately adjusted according to the shape, thickness and the like of the electrode to be formed. Moreover, you may provide the drying process at about 80-200 degreeC between application | coating and baking of an electrically conductive paste.

<Solar cell>
The solar cell of the present invention comprises an electrode formed using such a conductive paste of the present invention, specifically, an electrode baked on a semiconductor substrate. The solar cell of the present invention preferably comprises, 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. The PERC solar cell usually has an antireflection film made of an insulating material on the light receiving surface, and has an insulating film made of the same insulating material as the antireflection film on the entire back surface except for a part.

  The solar cell of the present invention is an electrode formed using the conductive paste of the present invention as an electrode formed in a form in partial contact with the semiconductor substrate on an insulating film provided on the back surface in a PERC solar cell or the like. It is preferable to have. When the conductive paste of the present invention is used, when the electrode is formed on the semiconductor substrate through the insulating film, the insulating film and the electrode from which the insulating layer is removed are sufficiently ensured to be in contact with the semiconductor substrate. By having water resistance and the like, an electrode having high reliability can be obtained.

  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 to form an Al electrode. More preferably, an insulating film is formed on a semiconductor substrate, and a portion of the insulating film is removed by, for example, a laser to form an insulating film having an opening, and then the semiconductor substrate is formed on the insulating film through the opening. The conductive paste of the present invention is used to form an Al electrode in the form of partial contact.

For example, a back electrode of a PERC solar cell using a p-type Si substrate, an n-type Si substrate, as an Al electrode provided on an insulating film having an opening to be in contact with the semiconductor substrate through the opening. The back electrode of a PERT (Passivated Emitter, Rear Totally diffused) solar cell using an electrode, the electrode provided on the p layer or p ⁺ layer side of the double-sided light receiving solar cell using an n-type Si substrate or a p-type Si substrate, One electrode of a contact type solar cell etc. are mentioned.

As one embodiment of the solar cell of the present invention, a silicon substrate having a sunlight receiving surface, a first insulating film provided on the sunlight receiving surface side of the silicon substrate, and a sunlight receiving surface of the silicon substrate are opposite to each other. A second insulating film provided on the side surface, the second insulating film having at least one opening, a second electrode partially contacting the silicon substrate through the opening of the second insulating film, and a first electrode A solar cell comprising a first electrode penetrating part of the insulating film and contacting the silicon substrate, wherein the second electrode is selected from the group consisting of Al, Ag, Cu, Au, Pd and Pt 6 to 30% of V ₂ O ₅ , 15 to 50% of B ₂ O ₃ , 10 to 40% of BaO, and 5 to 30% of ZnO in terms of mol% of oxide conversion, and a metal containing at least one of %, and a glass _Al 2 _{O 3} containing 0-15%, consisting of the sun Pond, and the like.

  Note that the opening of the second insulating film refers to a portion which penetrates from the surface of the second insulating film to the surface of the silicon substrate opposite to the sunlight receiving surface. Also in the following description, the term "opening" is used in the same meaning as described above.

  The shape of the opening is not particularly limited, but may be linear or circular. When the shape is linear, the line width is preferably 30 to 100 μm, and when circular, 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 of the silicon substrate opposite to the solar light receiving surface.

  The first electrode preferably contains a metal containing at least one selected from the group consisting of Al, Ag, Cu, Au, Pd and Pt, and the metal preferably contains at least Ag. The first insulating film is made of, for example, an insulating material such as silicon nitride, titanium dioxide, silicon oxide, or aluminum oxide, and is preferably made of 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 a metal oxide film of aluminum oxide or silicon oxide in contact with the surface of the silicon substrate opposite to the solar light receiving surface, and a nitride film further on the metal oxide film. The configuration of a multilayer film comprising a silicon film is preferred.

  Hereinafter, the case where the electrode of the solar cell of a p-type Si substrate single-sided light reception type is formed with the conductive paste of this invention is demonstrated to an example. FIG. 1 is a view schematically showing a cross section of an example of a p-type Si substrate single-sided light receiving type solar cell having an electrode formed using the conductive paste of the present invention.

  A solar cell 10 shown in FIG. 1 includes a p-type Si substrate 1, an insulating film 2A provided on the upper surface thereof, and an insulating film 2B having an opening 7 provided on the lower surface. An Al electrode 4 is formed and partially in contact with the p-type Si substrate through the opening 7, and an Ag electrode 3 penetrating through a part of the insulating film 2A and contacting the p-type Si substrate 1. The upper surface of the p-type Si substrate 1 has, for example, a concavo-convex structure formed by using a wet etching method to reduce the light reflectance. Note that the upper and lower sides of the drawings do not necessarily indicate the upper and lower sides in use. If necessary, both surfaces of the p-type Si substrate may have a concavo-convex structure.

The p-type Si substrate 1 is composed of an n ⁺ layer 1a and ap layer 1b in order from the top, the Al electrode 4 is in contact with the p layer 1b, and the Ag electrode 3 is in contact with the n ⁺ layer 1a. Here, the n ⁺ layer 1a can be formed by doping, for example, P, Sb, As or the like on the surface on which the above-described concavo-convex structure is formed.

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

  That is, the insulating film 2A provided on the upper surface of the p-type Si substrate 1 is present without gaps on the entire surface before the Ag electrode 3 is formed, and only the portion to which the conductive paste for forming the Ag electrode 3 is applied. By melting the conductive paste at the time of firing, an Ag electrode 3 penetrating the insulating film 2A and contacting the p-type Si substrate 1 is formed.

  On the other hand, after the insulating film 2B is provided on the entire lower surface of the p-type Si substrate 1 without gaps, a part of the insulating film 2B is physically removed by laser to form the Al electrode 4 and has the opening 7 It is supposed to be configured. The above-described conductive paste for forming an Al electrode is applied to the entire surface of the insulating film 2B having the opening 7 and baked to cover the entire surface of the insulating film 2B, and Al partially contacts the semiconductor at the opening 7 An electrode 4 is formed.

When the Al electrode 4 is formed, the conductive paste for forming the Al electrode contacts the p layer 1b of the p-type Si substrate 1 at the opening 7 and is then melted at the time of firing to make Al from the Al electrode into the p layer 1b. It diffuses and an Al-Si alloy layer 5 is formed directly on the Al electrode. Furthermore, BSF (Back Surface Field) layer 6 is obtained immediately above the Al-Si alloy layer 5 as ap ⁺ layer.

  In 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 as described above, it is particularly preferable to use as a conductive paste for forming an Al electrode.

  When forming an electrode through an insulating film by using the powder of the glass of the present invention and the conductive paste of the present invention containing Al powder as a conductive paste for forming an Al electrode, the electrode, the insulating film, and the semiconductor substrate A sufficient contact with the above is ensured, and an Al electrode 4 sufficiently in contact with the p-type Si substrate 1 is obtained.

  In addition, the insulating film which a solar cell has has the function of reflection prevention, and can suppress the recombination of a semiconductor carrier, and can use the insulating material mentioned above as an insulating material which comprises this film. is there. The insulating film may be a single layer film or a multilayer film. The conductive paste of the present invention is an electrode, an insulating film, and a partially formed semiconductor substrate when forming the electrode through an insulating film having a layer of silicon nitride and a layer of aluminum oxide or silicon oxide. The contact with the metal can be sufficiently ensured, and the solar cell can have high solar cell characteristics, and the electrode portion can have high reliability such as high weather resistance.

  In the solar cell of the present invention, in particular, the PERC solar cell, the insulating film is partially removed to the extent that electrical contact is possible on the back surface, and the entire surface of the insulating film is formed when forming the electrode containing the glass powder of the present invention The portion where the insulating film is partially removed at the same time when the electrode is formed can form an electrode structure in which the contact with the semiconductor substrate is secured. By using the conductive paste, the electrode having a good appearance can be formed, and the obtained electrode has a weather resistance such as water resistance, thereby achieving a solar cell capable of achieving high reliability and high battery characteristics. Can be provided.

  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)
Glass was manufactured as thin plate-like glass by the following method, and glass powder was manufactured from thin plate-like glass. While measuring the particle size distribution of glass powder, the glass transition temperature of glass was measured using glass powder.

<Manufacture of glass (thin plate glass)>
Raw material powders are blended and mixed so as to obtain the composition shown in Table 1 and melted for 30 minutes to 1 hour using a crucible in an electric furnace at 900 to 1200 ° C. Molded.

<Manufacture of glass powder>
In each case, the obtained thin glass was combined with dry grinding and wet grinding and ground as follows 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 glasses of Examples 1 to 18 were dry-pulverized by a ball mill, by adjusting the pulverization time to obtain a predetermined D _50, through end 150 mesh sieve to produce a glass powder.

With respect to the glass of Example 19, a glass obtained by wet-pulverizing glass powder from which coarse particles have been removed after the above-mentioned dry-grinding to further reduce D ₅₀ within the above-mentioned predetermined range using water in a ball mill The powder was used as a glass powder. In order to obtain a predetermined D ₅₀ during this wet grinding, the ball was made of alumina with a diameter of 5 mm, and the D ₅₀ was adjusted at the grinding time. Thereafter, the slurry obtained by wet grinding was filtered to remove most of the water, and then dried at 130 ° C. with a drier to adjust the water content to produce a glass powder.

<Evaluation>
It was assessed D ₅₀ of the glass transition temperature and the glass powder in the following manner for a glass of each example. The results are shown in Table 1 together with the composition. In addition, in the column of each component of glass composition, a blank shows content "0%."

(Glass-transition temperature)
The obtained glass powder was put in a pan made of aluminum, and a temperature rising rate was measured at 10 ° C./min with a differential thermal analyzer TG8110 manufactured by Rigaku Corporation. The first inflection point of the DTA chart obtained by the measurement was taken as the glass transition temperature (indicated as "DTA Tg" in Table 1).

(D ₅₀ )
About the glass of Examples 1-18, 0.02 g of glass powder was mixed with 60 cc of isopropyl alcohol (IPA), and was dispersed for 1 minute by ultrasonic dispersion. And the sample placed in a Microtrac measuring device (laser diffraction scattering particle size distribution analyzer), the value obtained D _50. For the glass of Example 19, 0.02 g of glass powder was mixed with 60 cc of water and dispersed by ultrasonic dispersion for 1 minute. And the sample placed in a Microtrac measuring machine, to obtain a value of D _50.

<Production of conductive paste>
The conductive paste for Al electrode formation which contains the glass powder of Examples 1-19 produced above respectively was produced with the following method.

  First, 90 parts by mass of butyl diglycol acetate was mixed with 10 parts by mass of ethyl cellulose and stirred at 85 ° C. for 2 hours to prepare an organic vehicle. Next, 21 parts by mass of the organic vehicle thus obtained was mixed with 79 parts by mass of Al powder (sprayed aluminum powder manufactured by Minalco: # 800F), and the mixture was kneaded for 10 minutes by a grinder. Thereafter, a glass powder was blended in a proportion of 3 parts by mass with respect to 100 parts by mass of the Al powder, and the mixture was further kneaded for 60 minutes by a grinder to obtain a conductive paste for forming an Al electrode.

<Evaluation>
The appearance and water resistance were confirmed as evaluation of a fired film after electrode formation using the conductive paste for Al electrode formation. At this time, the insulating film used was formed of two layers of a silicon nitride layer and an aluminum oxide layer. The results are shown in Table 1.

(Preparation of Al electrode and evaluation of appearance and water resistance)
An Al electrode is formed on a semiconductor substrate through an insulating film (a two-layer film consisting of a silicon nitride layer and an aluminum oxide layer) on a semiconductor substrate using the conductive paste for forming an Al electrode respectively as described below, The appearance and water resistance of the Al electrode were evaluated.

  Using a p-type crystalline Si semiconductor substrate sliced to a thickness of 160 μm, first, in order to clean the sliced surface of the substrate, the surface was etched with a very small amount of hydrofluoric acid. After that, a wet etching method was used on the surface of the crystalline Si semiconductor substrate on the light receiving surface side of light to form a concavo-convex structure that reduces the light reflectance. Next, an n-type layer is formed by diffusion on the light receiving surface of the semiconductor substrate. P was used as a doping element for n-type conversion. Next, an insulating film was 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 were mainly used, and an aluminum oxide layer was formed to a thickness of 10 nm by plasma CVD, and then a silicon nitride layer was formed to a thickness of 120 nm on the upper layer.

  Next, the semiconductor substrate is cut into a square size of 30 mm × 30 mm with a dicer, and the conductive paste for forming an Al electrode obtained above is 20 mm × 20 mm by screen printing on the back surface side insulating film. It apply | coated to 20 mm square pattern shape. Thereafter, firing was performed at a peak temperature of 760 ° C. for 100 seconds using an infrared heating belt furnace to form an Al electrode.

(1) Appearance Evaluation The appearance of the Al electrode formed on the p-type layer (rear surface) side obtained above through an insulating film (a two-layer film consisting of a silicon nitride layer and an aluminum oxide layer) was evaluated. Thereafter, whether or not the electrode could be formed as an Al electrode was visually evaluated according to the following criteria.

;: Al electrode is formed without peeling or discoloration.
X: Peeling or discoloration has occurred, which is insufficient as an Al electrode.

The results of the appearance evaluation are shown in Table 1. In the glass of Examples 1 to 17, the Al electrode was able to be bonded to the insulating layer on the entire surface, and was uniform gray. The glass of Example 18 has a high content of V ₂ O ₅ and is good in terms of adhesion, but turns to brown at a local point, which is a problem in terms of the appearance as a solar cell. The glass of Example 19 is a glass not containing V ₂ O ₅ and although it is good in terms of conductivity, the Al electrode layer is peeled off.

(2) Water resistance evaluation 50 cc of ion-exchanged water obtained by heating the semiconductor substrate having the Al electrode formed on the p-type layer (rear surface) side via the insulating film on the above obtained at 85 ° C. in a thermostatic water tank Soaked in a beaker for 30 minutes. The condition of the Al electrode at that time was evaluated by the following criteria.

;; Al electrode does not foam or discolor even if immersed for 30 minutes.
Δ: A large number of bubbles adhere to the surface of the Al electrode during immersion.
X: During immersion, the Al electrode reacts violently with ion exchange water to foam and discolor.

  The results of the water resistance evaluation are shown in Table 1. The glass of Examples 1 to 17 did not react violently or discolor, although a small amount of bubbles adhered to the surface of the Al electrode. The glass of Example 18 generated many bubbles on the surface of the Al electrode. The glass of Example 19 reacted violently with ion exchange water to foam and eventually turned brown.

  In the solar cell, since the solar battery cell obtained by forming the electrode on the semiconductor substrate as described above is usually sealed with a resin such as ethylene vinyl acetate (EVA), the water content is Is easy to invade. Also, considering the environment in which the solar cell is installed, it is an inevitable event that some moisture intrudes into the interior during use. Therefore, in order to maintain the reliability of the solar cell highly, the water resistance of the electrode is an essential requirement. For example, in the case of an Al electrode, when the water resistance is low, Al reacts with water to become aluminum hydroxide and does not function as an electrode, resulting in deterioration of the characteristics as a solar cell. In the present invention, since the electrode has the water resistance as described above, it can be said that the reliability of the solar cell is sufficiently high.

<Manufacture of solar cells>
Using the conductive paste for Al electrode formation obtained using the glass powder of the above-mentioned Example 14, Example 17 and Example 19 and the commercially available conductive paste for Ag electrode formation, the configuration shown in FIG. 1 is as follows: An Al electrode 4 as a back surface electrode was formed on the non-light receiving surface on the p-type Si semiconductor substrate 1 and an Ag electrode 3 was formed on the light receiving surface as a front surface electrode to manufacture a solar cell 10.

  First, an insulating film 2A comprising a silicon nitride layer and an insulating film comprising a two-layer film of an aluminum oxide layer and a silicon nitride layer sequentially from the non-light receiving surface side of the substrate on the light receiving surface side and the non light receiving surface side of the Si semiconductor substrate. Formed 2B. Furthermore, in the insulating film 2B, the opening 7 was formed at a predetermined position by laser. Next, on the surface of the semiconductor substrate facing the entire surface on the non-light receiving surface side, that is, the surface of the insulating film 2B and the opening 7 where the insulating film 2B is partially removed by the laser The conductive paste for forming an Al electrode obtained using 19 glass powders was applied by screen printing and dried at 120 ° C.

  Next, a conductive paste for Ag electrode formation was applied by screen printing in a line shape over the entire surface of the insulating film 2A of the Si semiconductor substrate 1. Thereafter, firing was performed at a peak temperature of 760 ° C. for 100 seconds using an infrared light heating belt furnace to form a front surface Ag electrode 3 and a back surface Al electrode 4, thereby completing the solar cell 10. The surface Ag electrode 3 was formed to penetrate the insulating film 2A.

(Measurement of solar cell conversion efficiency)
The conversion efficiency of the solar cell manufactured using the conductive paste for Al electrode formation which contains the glass powder of each said example was measured using the solar simulator. Specifically, a solar cell was installed in a solar simulator, and a current-voltage characteristic was measured according to JIS C8912 with a reference solar beam of spectral characteristic AM 1.5 G to derive a conversion efficiency of each solar cell. Table 2 shows the obtained conversion efficiency results.

The symbols in Table 2 have the following meanings.
Short circuit current Voc (mV) in the short circuit state; open circuit voltage FF (%) in the open state; curve factor Eff (%); conversion efficiency

  From Table 2, when using the glass powder of Example 14 and Example 17, FF is 80% or more and it turns out that 20% or more of conversion efficiency Eff was able to be obtained. The performance has been sufficiently demonstrated as a PERC solar cell. On the other hand, when the glass powder of Example 19 was used from Table 2, the Al electrode peeled after electrode formation, and since it was not able to measure the conversion efficiency of a solar cell, it described as "x".

  When the glass powders of Example 14 and Example 17 are used, a high FF can be maintained while maintaining a good appearance, and an insulating film of an aluminum oxide layer and a silicon nitride layer is provided on the non-light receiving surface side. As compared with a solar cell that is not used, high Isc and Voc can be realized as a PERC solar cell, and Eff can exceed 20%. When the glass powder of Example 18 which is a comparative example is used, the glass powder of Example 14 and Example 17 which are Examples is against the appearance as a PERC solar cell being bad and long-term reliability can not be obtained. When used, it is excellent in that it has good appearance as a PERC solar cell, and can simultaneously maintain contact with the insulating film on the non-light receiving surface side and the Si semiconductor substrate, and long-term reliability can be obtained. ing.

  As can be seen from Tables 1 and 2, compared to the glasses and glass powders of Comparative Examples 18 and 19, the glasses and glass powders of Examples 1 to 17 are for forming a solar cell electrode. It is suitable.

DESCRIPTION OF SYMBOLS 10 ... Solar cell, 1 ... p-type Si semiconductor substrate, 1a ... n ⁺ layer, 1b ... p layer, 2A, 2B ... insulation film, 3 ... Ag electrode, 4 ... Al electrode, 5 ... Al-Si alloy layer, 6 ... BSF layer, 7 ... opening.

Claims (18)

In mol% of oxide conversion,
6 to 30% of V ₂ O ₅
15 to 50% of B ₂ O ₃ ,
10 to 40% of BaO,
5 to 30% of ZnO and 0 to 15% of Al ₂ O ₃
Glass characterized by including. The glass according to claim 1, further comprising 0 to 10% in total of at least one selected from SiO ₂ , SrO, MoO ₃ and WO _{3 in} terms of molar percentage in terms of oxide.   The glass according to claim 1 or 2, wherein the glass transition temperature is 380 to 550 ° C. 50% particle diameter based on volume in a cumulative particle size distribution is taken as _{D 50,} glass powder comprising glass according to any one of claims 1 to 3 _{D 50} is 0.8～6.0Myuemu.   A conductive paste comprising the glass powder according to claim 4, a conductive metal powder, and an organic vehicle.   A solar cell comprising an electrode formed using the conductive paste according to claim 5. A conductive paste comprising metal, glass and an organic vehicle,
The metal is contained in an amount of 63.0 to 97.9% by mass based on the total mass of the conductive paste, and includes at least one selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt,
The glass is contained in an amount of 0.1 to 9.8 parts by mass with respect to 100 parts by mass of the metal, and in terms of mol% in terms of oxide, 6 to 30% of V ₂ O ₅ and 15 to 15 of B ₂ O ₃ 50%, 10-40% of BaO, 5-30% of ZnO, and 0-15% of Al ₂ O ₃ ,
A conductive paste comprising 2 to 30% by mass of the organic vehicle based on the total mass of the conductive paste. The conductive paste according to claim 7, wherein the glass further contains 0 to 10% in total of at least one selected from SiO ₂ , SrO, MoO ₃ and WO _{3 in} terms of mole percentage in terms of oxide.   The conductive paste according to claim 7 or 8, wherein the glass transition temperature of the glass is 380 to 550 ° C. The glass is a 50% particle diameter on a volume basis when the _{D 50} in a cumulative particle size _{distribution,} conductivity according to any one of claims 7 to 9 _{D 50} is glass particles 0.8~6.0μm paste.   The conductive paste according to any one of claims 7 to 10, wherein the metal contains Al. The organic vehicle is an organic resin binder solution in which an organic resin binder is dissolved in a solvent,
The organic resin binder is an acrylic resin obtained by polymerizing one or more selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, butyl acrylate, and 2-hydroxyethyl acrylate, and methyl cellulose And at least one selected from the group consisting of ethyl cellulose, carboxymethyl cellulose, oxyethyl cellulose, benzyl cellulose, propyl cellulose and nitrocellulose,
The conductive paste according to any one of claims 7 to 11, wherein the solvent contains at least one selected from the group consisting of terpineol, butyl diglycol acetate, ethyl diglycol acetate, propylene glycol diacetate, and methyl ethyl ketone. A silicon substrate having a sunlight receiving surface;
A first insulating film provided on the solar light receiving surface side of the silicon substrate;
A second insulating film having at least one opening provided on the surface of the silicon substrate opposite to the sunlight receiving surface;
A second electrode partially in contact with the silicon substrate via the opening of the second insulating film;
A first electrode penetrating through a portion of the first insulating film and contacting the silicon substrate;
The second electrode is a metal containing at least one selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt, and 6 to 30 of V ₂ O ₅ in terms of mol% in terms of oxide. A solar cell comprising:%, 15 to 50% B ₂ O ₃ , 10 to 40% BaO, 5 to 30% ZnO, and 0 to 15% Al ₂ O ₃ .   The solar cell according to claim 13, wherein the second electrode contains 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, 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 contains a metal containing at least Ag.   The solar cell according to any one of claims 13 to 16, wherein the first insulating film is made of silicon nitride.   The second insulating film further comprises a metal oxide film of aluminum oxide or silicon oxide in contact with the surface of the silicon substrate opposite to the solar light receiving surface, and a silicon nitride film on the metal oxide film. Item 18. The solar cell according to any one of items 13 to 17.

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