JP2019127404A - Glass, method for producing glass, conductive paste, and solar cell - Google Patents

Abstract

To provide: glass which, in glass used for electrode formation, can form electrodes at a low cost with good production efficiency, the electrodes being capable of securing contacts with a semiconductor substrate by penetrating an insulation film when forming electrodes on a semiconductor substrate of a solar cell or the like via an insulation film; a method for producing glass; a conductive paste which comprises powder of the glass and, when forming the electrodes, can penetrate the insulation film and form electrodes which secure contacts with the semiconductor substrate by penetrating the insulation film at a low cost with good production efficiency; and a solar cell which is improved in reliability and productivity by using the conductive paste.SOLUTION: Provided are: glass comprising, in terms of mol%, 5-60% of PbO, 20-50% of BO, 5-30% of SiO, 3-20% of KO, and 3-20% of CaO; a method for producing glass; a conductive paste comprising glass powder, conductive metal powder, and an organic vehicle; and a solar cell comprising electrodes formed by using the conductive paste.SELECTED DRAWING: Figure 1

Description

  The present invention relates to glass, a method for producing glass, a conductive paste, and a solar cell. In particular, the glass is suitable for forming an electrode for a solar cell, a method for producing glass, a conductive paste using the glass, and the conductive paste. The present invention relates to a solar cell having a negative electrode.

  Conventionally, an electronic device in which a conductive layer serving as an electrode is formed on a semiconductor substrate such as silicon (Si) has been used for various applications. For 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 is dispersed in an organic vehicle is applied on a semiconductor substrate, It forms by baking at the temperature more than the melting point of electroconductive metal powder.

  Thus, when forming an electrode on a semiconductor substrate, an insulating film is formed on the entire surface of the semiconductor substrate on which the electrode is formed, and the patterned electrode partially penetrates the insulating film to form the 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 antireflection film is for reducing the surface reflectance while increasing the visible light transmittance while increasing the light receiving efficiency, and is usually made of an insulating material such as silicon nitride, titanium dioxide, silicon dioxide, or aluminum oxide. Configured Moreover, in solar cells such as PERC (Passivated Emitter and Rear Contact), a passivation film made of the same insulating material as the antireflection film is provided on the entire back surface, and electrodes are partially formed on the semiconductor substrate on the passivation film. 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. The insulating film is removed from the light-receiving surface in a portion corresponding to the electrode pattern, and the insulating film is removed. The electrodes are formed on the In addition, the insulating film is partially removed on the back surface of the PERC solar cell or the like as long as electrical contact is possible, and an electrode is formed on the entire back surface.

  As a method of partially removing the insulating layer, there is a method of physically removing it with a laser or the like. However, since the manufacturing process is increased and the cost of introducing the device is increased, glass powder is included in the electrode formation in recent years. A method is used in which a conductive paste (a paste-like electrode material) is used to penetrate an insulating film through the conductive paste by fire-through. In this method, for example, after an insulating film is provided on the entire surface of the semiconductor substrate, a conductive paste is applied on the insulating film in an appropriate shape and subjected to a baking treatment. As a result, the electrode material is heated and melted, and at the same time, the insulating film in contact with the glass reacts and melts with the glass, so that the electrode penetrates the insulating film and comes into contact with the semiconductor substrate. In a back electrode of a PERC solar cell or the like, a conductive paste that penetrates the insulating film and a conductive paste that does not penetrate the insulating film are used in combination, so that it is formed on the entire back surface and partially penetrates the insulating film and contacts the semiconductor substrate An electrode is obtained.

  As such a conductive paste containing glass powder that penetrates the insulating film by fire-through, for example, Patent Document 1 describes a solar cell electrode paste. In patent document 1, as glass which comprises the said glass powder, it contains Te, Bi, Li, and Zn as an essential main component in a specific ratio, respectively, in terms of oxide, and Mg, Ti, V, Cr, Mn, A lead-free glass containing Fe, Co, Ni, Cu, and W optionally at 5 mol% or less is used.

Also, methods for use as a conductive paste through the insulating film is not described, the glass composition using PbO and B ₂ O ₃ and SiO ₂ and K _{2 O} is known. In Patent Document 2, as the sealing glass, 42.6 mol% of PbO, 33.3 mol% of B ₂ O ₃ , 5.4 mol% of SiO ₂ and 5.2 of K ₂ O in oxide conversion. Glasses containing mol% are described. _The electrode-forming material using glass powder containing B 2 _{O 3} and _{K 2} O, CaO and SiO ₂ are known.

Patent Document 3, in the glass used for the back electrode of the solar cell, a _B 2 _{O 3} 50 mol% in terms of oxide, CaO 9 mol%, glass containing SiO ₂ 9 mol% is described. In Patent Document 4, 30 mol% of B ₂ O ₃ , 10 mol% of K ₂ O, 10 mol% of CaO, and 10 SiO ₂ are calculated as oxides as a novel optical glass suitable for precision mold press molding. Glasses containing mol% are described. Furthermore, with regard to the glass containing PbO, Patent Document 5 contains 59.3 mol% of PbO, 13.4 mol% of SiO ₂ and 22.5 mol% of B ₂ O ₃ as a glass composition for sealing. Glass is described.

Patent No. 5856277 Japanese Patent Application Laid-Open No. 62-270438 JP, 2013-18666, A JP, 2006-327925, A JP-A-4-292438

  The present invention relates to a glass used for forming an electrode, and when forming an electrode on a semiconductor substrate such as a solar cell via an insulating film, an electrode that penetrates the insulating film and can sufficiently ensure contact with the semiconductor substrate is provided. An object of the present invention is to provide glass and a method of manufacturing glass which can be formed efficiently at low cost. The present invention uses a conductive paste containing the glass powder, which can form an electrode penetrating an insulating film at the time of electrode formation and ensuring contact with a semiconductor substrate at low cost and with high production efficiency, and the conductive paste. To provide a solar cell with improved reliability and productivity.

The present invention provides a glass having the following constitution, a method for producing glass, a conductive paste, and a solar cell.
[1] In mol% notation, 5 to 60% of PbO, 20 to 50% of B ₂ O ₃ , 5 to 30% of SiO ₂ , ₃ to 20% of K ₂ O, 3 to 20% of CaO are contained. Glass characterized by having.
[2] The glass according to [1], further containing 3 to 20% of BaO in mol%.
[3] The glass according to [1] or [2], further containing 0 to 10% in total of at least one selected from SrO, Al ₂ O ₃ and MgO in terms of mol%.

[4] In terms of mol%, 35 to 60% of B ₂ O ₃ , 1 to 40% of K ₂ O, 3 to 30% of CaO, 5 to 10% of SiO ₂ and substantially free of PbO A process of mixing a first glass and a second glass containing 20 to 85% of PbO, ₁ to 60% of SiO ₂ and ₃ to 21% of B ₂ O ₃ in terms of mol% Production method.
[5] The method for producing a glass according to [4], wherein the first glass further contains 1 to 25% of BaO in terms of mol%.
[6] The method for producing a glass according to [4] or [5], wherein the first glass further contains 0 to 15% of SrO in terms of mol%.
[7] The glass according to any one of [4] to [6], wherein the second glass further contains 0-10% in total of at least one selected from Al ₂ O ₃ and MgO in mol% notation. Manufacturing method.
[8] The method for producing a glass according to any one of [4] to [7], wherein a mixing ratio of the first glass and the second glass is 20:80 to 80:20 by mass ratio.
[9] The glass according to any one of [4] to [8], wherein the first glass and the second glass are mixed to obtain the glass according to any of [1] to [3]. Manufacturing method.

[10] in terms of mol%, containing 5 to 60% of PbO, 20 to 50% of B ₂ O ₃ , 5 to 30% of SiO ₂ , ₃ to 20% of K ₂ O, and 3 to 20% of CaO A conductive paste containing glass powder, conductive metal powder and an organic vehicle.
[11] In terms of mol%, 35 to 60% of B ₂ O ₃ , 1 to 40% of K ₂ O, 3 to 30% of CaO, 5 to 10% of SiO ₂ and substantially free of PbO A mixture comprising a powder of a first glass, and a powder of a second glass containing 20 to 85% of PbO, ₁ to 60% of SiO ₂ and ₃ to 21% of B ₂ O ₃ in terms of mol% Conductive paste containing an inorganic metal powder and an organic vehicle.
[12] A solar cell comprising an electrode formed using the conductive paste according to [10] or [11].

  In the present invention, in the glass used for electrode formation, when an electrode is formed on a semiconductor substrate such as a solar cell via an insulating film, the electrode that can sufficiently ensure contact with the semiconductor substrate through the insulating film It is possible to provide a glass and a method of manufacturing glass that can form the glass efficiently at low cost. In the present invention, a conductive paste containing the glass powder and capable of forming an electrode penetrating an insulating film at the time of electrode formation and ensuring contact with a semiconductor substrate at low cost and using the conductive paste is used. Thus, it is possible to provide a solar cell with improved reliability and productivity.

It is the figure which showed typically the cross section of an example of the p-type Si substrate double-sided light reception type solar cell by which the electrode formation was carried out using the electrically conductive paste of this invention. It is the figure which showed the electrode pattern formed in the Si substrate used when contacting resistance component Rc [(ohm)] was evaluated. It is a graph (Example 33, Example 51) which shows the relationship between the distance L [cm] between electrodes at the time of calculating | requiring contact resistance component Rc [(ohm)] using the electrode pattern shown in FIG. It is a photograph which shows the evaluation result of insulating film penetration of the electrically conductive paste containing the glass of an Example (Example 33). It is a photograph which shows the evaluation result of the insulating-film penetration of the electrically conductive paste containing the glass of a comparative example (Example 45).

Hereinafter, embodiments of the present invention will be described.
<Glass>
The glass of the present invention is, in terms of mol%, 5 to 60% of PbO, 20 to 50% of B ₂ O ₃ , 5 to 30% of SiO ₂ , ₃ to 20% of K ₂ O, 3 to 20% of CaO It is characterized by including.

The glass of the present invention is, in terms of mol%, 5 to 60% of PbO, 20 to 50% of B ₂ O ₃ , 5 to 30% of SiO ₂ , ₃ to 20% of K ₂ O, 3 to 20% of CaO In the case of forming an electrode by fire through using a conductive paste containing the glass and conductive metal powder through an insulating film on a semiconductor substrate, the glass can be used as an insulating film in the initial process of firing. The penetration further increases the temperature, whereby the glass promotes the penetration of the electrode into the semiconductor substrate, thereby enabling the formation of a highly reliable insulating film penetration electrode having sufficient contact. When the glass of the present invention is used, the insulating film through electrode can be formed at a low cost with higher production efficiency than the method of physically removing the insulating film with a laser or the like.

  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

  Further, in the present specification, substantially not containing means that it is not actively contained, but is allowed to be mixed due to inevitable impurities.

  Hereinafter, the glass of the present invention can exhibit the above-described effects when an electrode is formed by fire-through using a conductive paste containing the glass and conductive metal powder on a semiconductor substrate via an insulating film. In the following description, “when forming an electrode” refers to a case where an electrode is formed by fire-through using a conductive paste containing glass and conductive metal powder on a semiconductor substrate via an insulating film unless otherwise specified. It means the time of electrode formation.

  Hereinafter, each component of the glass of this invention is demonstrated. In the following description, the unit “%” of the content of each component of glass indicates mol% in terms of oxide unless otherwise specified. The same applies to the first glass and the second glass described later.

  In the glass of the present invention, PbO is an essential component that improves the softening fluidity of the glass and has reactivity with the insulating film. In addition, PbO in the glass can easily increase the reactivity with the insulating film by lowering the glass transition point. As a result, the electrode and the semiconductor substrate can be easily reacted with each other to reduce the contact resistance.

  The glass of the present invention contains PbO at a ratio of 5% to 60%. If the PbO content is less than 5%, the glass softening point is increased, so that the fluidity is lowered and the reaction with the insulating film is not sufficient. The content of PbO is preferably 7% or more, more preferably 8% or more. On the other hand, if the content of PbO exceeds 60%, glass can not be obtained due to crystallization. The content of PbO is preferably 55% or less, more preferably 50% or less.

B ₂ O ₃ is an essential component in the glass component of the present invention. B ₂ O ₃ has a function of improving the softening fluidity of the glass and improving the bonding strength with 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 by flowing the glass. Thereby, for example, the semiconductor substrate is a pn junction type Si semiconductor substrate, and glass can form a p ⁺ layer or an n ⁺ layer in contact with the 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 containing as B, and thereby form a better p ⁺ layer it can.

The glass of the present invention contains B ₂ O ₃ at a ratio of 20% to 50%. When the content of B ₂ O ₃ is less than 20%, 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 component for forming a glass network structure, and if it is less than 20%, it cannot be vitrified. The content of B ₂ O ₃ is preferably 22% or more, more preferably 23% or more. On the other hand, if the content of B ₂ O ₃ exceeds 50%, the weather resistance may deteriorate. The content of B ₂ O ₃ is preferably 48% or less, more preferably 45% or less.

In the glass component of the present invention, SiO ₂ is an essential component for increasing the weather resistance. Further, it is possible to stabilize the glass by the inclusion of SiO _2. The content of SiO _{2 in} the glass of the present invention is 5% or more and 30% or less. If the content of SiO ₂ is less than 5%, it is difficult to obtain glass by crystallization, and long-term reliability of characteristics as a solar cell cannot be obtained. The content of SiO ₂ is preferably 6% or more. If the content of SiO ₂ exceeds 30%, the glass transition point will rise, so that the glass cannot flow during sintering. The content of SiO ₂ is preferably 28% or less.

In the glass component of the present invention, K ₂ O is an essential component that improves the softening fluidity of the glass and improves the bonding strength between the semiconductor substrate and the electrode. Further, K ₂ O in the glass can easily move into the semiconductor substrate after passing through the insulating film on the semiconductor substrate. As a result, the contact resistance between the electrode and the semiconductor substrate can be reduced. For example, if the conductive metal is Al, it can help Al particles diffuse well into the Si semiconductor substrate, form a good p ⁺ layer, or make it possible to further enhance the p ⁺ layer performance. Become.

The glass of the present invention contains K ₂ O at a ratio of 3% to 20%. When the content of K ₂ O is less than 3%, the glass softening point is increased, the fluidity is reduced, and the bonding strength between the semiconductor substrate and the electrode is not sufficient. The content of K ₂ O is preferably 4% or more. On the other hand, when the content of K ₂ O exceeds 20%, glass can not be obtained by crystallization. The content of K ₂ O is preferably 19% or less, more preferably 18% or less.

  In the glass component of the present invention, CaO is an essential component that lowers the contact resistance component between the electrode and the semiconductor substrate. CaO can form crystal nuclei when heat is applied as a glass component, and the crystal grains can be grown to complete penetration of the insulating film in the semiconductor substrate. The content of CaO in the glass of the present invention is 3% or more and 20% or less. If the content of CaO is less than 3%, the insulating film cannot be sufficiently penetrated at the time of electrode formation. For example, conversion efficiency in a solar cell may not be increased. The content of CaO is preferably 4% or more. When the content of CaO exceeds 20%, glass can not be obtained due to crystallization. The content of CaO is preferably 19% or less, more preferably 18% or less.

  The glass of the present invention can contain optional components as needed in addition to the above-mentioned essential components. As an optional component which is preferably contained in the glass of the present invention, BaO can be mentioned. When the glass of the present invention contains BaO, the contact resistance component between the electrode and the semiconductor substrate can be further reduced. The content of BaO in the glass is preferably 3% or more and 20% or less. When the content of BaO is less than 3%, the glass transition point is excessively increased, and the contact resistance between the electrode and the semiconductor may be increased. The content of BaO is more preferably 4% or more. If the content of BaO exceeds 20%, there is a possibility that glass can not be obtained due to crystallization. The content of BaO is more preferably 18% or less, still more preferably 15% or less.

The glass of the present invention preferably further contains 0 to 10% in total of at least one selected from SrO, Al ₂ O ₃ and MgO. When the glass of this invention contains these components, glass can be stabilized or a weather resistance can be raised. The total content of SrO, Al ₂ O ₃ and MgO is preferably 0.5% or more. SrO, Al ₂ O ₃ and MgO may not vitrify if the total amount exceeds 10%. The total content of SrO, Al ₂ O ₃ and MgO 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, P ₂ O ₃ , As ₂ O ₅ , Sb ₂ O ₅ , ZnO, Li ₂ O, Na ₂ O, ZrO ₂ , Fe ₂ O ₃ , CuO, Sb ₂ O ₃ , SnO ₂ , MoO ₃ , WO ₃ , MnO, MnO ₂ , CeO ₂ , TiO _{2, and} other various oxide components used for normal glass. These oxide components are used singly or in combination of two or more depending on the purpose. The total content of the other optional components is preferably 5% or less.

  The method for producing the glass of the present invention is not particularly limited. For example, a raw material mixture is prepared so that the glass obtained as described below has the above composition, and heated and melted and solidified by a known method. Further, the glass of the present invention may be obtained by melting and solidifying a mixture obtained by combining the following first glass and second glass so as to have the glass composition of the present invention.

<Glass manufacturing method>
The present invention contains 35 to 60% of B ₂ O ₃ , 1 to 40% of K ₂ O, 3 to 30% of CaO, 5 to 10% of SiO ₂ and substantially contains PbO in mol% notation. Mixing the first glass with the second glass containing 20 to 85% of PbO, ₁ to 60% of SiO ₂ and ₃ to 21% of B ₂ O ₃ in terms of mol%, Provided is a method for producing glass.

According to the production method of the present invention, it is easy to adjust the composition of the glass of the present invention. In the production method of the present invention, the first glass substantially contains 35 to 60% of B ₂ O ₃ , 1 to 40% of K ₂ O, 3 to 30% of CaO, and 5 to 10% of SiO _2. Does not contain PbO. In the present specification, the phrase “not substantially contained” means that the inclusion by inevitable impurities is allowed, although it is not actively contained.

  As described above, PbO is a component having reactivity with the insulating film. In the glass obtained by the manufacturing method of the present invention, the second glass contains PbO and functions mainly because the electrode penetrates the insulating film. The function of facilitating the reaction between the electrode and the semiconductor substrate thereafter is mainly achieved by the first glass.

In the first glass, B ₂ O ₃ is an essential component having a function of improving the softening flowability of the glass obtained using the first glass and the second glass and improving the bonding strength with the semiconductor substrate. is there. In the following description, the obtained glass refers to glass obtained using the first glass and the second glass. Further, B ₂ O ₃ is a component to stabilize the glass obtained.

The content of B ₂ O ₃ in the first glass is 35% or more and 60% or less. From the above viewpoint, the content of B ₂ O ₃ is preferably 38% or more, and more preferably 40% or more. When the content of B ₂ O ₃ exceeds 60%, there is a possibility that the weather resistance of the glass obtained is deteriorated. The content of B ₂ O ₃ is preferably 58% or less, more preferably 55% or less.

In the first glass, K ₂ O is an essential component that improves the softening fluidity of the obtained glass and improves the bonding strength between the semiconductor substrate and the electrode. The content of K ₂ O in the first glass is 1% or more and 40% or less. From the above viewpoint, the content of K ₂ O is preferably 3% or more, more preferably 5% or more. If the content of K ₂ O exceeds 40%, glass cannot be obtained by crystallization. The content of K ₂ O is preferably 35% or less, more preferably 25% or less.

  In the first glass, CaO is an essential component that lowers the contact resistance component between the electrode and the semiconductor substrate in the obtained glass. The content of CaO in the first glass is 3% or more and 30% or less. The content of CaO is preferably 4% or more, more preferably 5% or more from the above viewpoint. When the content of CaO exceeds 20%, crystallization can not be obtained. The content of CaO is preferably 28% or less, more preferably 25% or less.

In the first glass, SiO ₂ is an essential component for increasing the weather resistance of the obtained glass. Further, it is possible to stabilize the glass obtained by the inclusion of SiO _2. The content of SiO ₂ in the first glass is 5% or more and 10% or less. From the above viewpoint, the content of SiO ₂ is preferably 6% or more. If the content of SiO ₂ exceeds 10%, the glass obtained will not be able to flow during sintering because the glass transition point will increase. The content of SiO ₂ is preferably 9% or less.

  The first glass can contain optional components as needed in addition to the above-mentioned essential components. BaO is mentioned as an optional component which it is preferable to contain in 1st glass. When the first glass contains BaO, in the resulting glass, the contact resistance component between the electrode and the semiconductor substrate can be further reduced. The content of BaO in the first glass is preferably 1% or more and 25% or less. The content of BaO is more preferably 3% or more. If the content of BaO exceeds 25%, glass may not be obtained due to crystallization. The content of BaO is more preferably 20% or less.

  The first glass may further contain SrO as an optional component. By containing SrO, fire through property can be provided to the obtained glass. The content of SrO in the first glass is preferably 0% to 15%. The SrO content is more preferably 3% or more. If the content of SrO exceeds 15%, vitrification may not occur. The content of SrO is more preferably 15% or less, still more preferably 10% or less.

In the production method of the present invention, the second glass, a PbO 20 to 85%, the SiO ₂ 1 to _60%, the B 2 _{O 3} containing from 3 to 21%.

  In the second glass, PbO is an essential component that improves the softening fluidity of the glass and has reactivity with the insulating film in the obtained glass. Further, the reactivity with the insulating film can be easily increased by lowering the glass transition point of PbO in the second glass. The content of PbO in the second glass is 20% or more and 85% or less. From the above viewpoint, the content of PbO is preferably 25% or more, and more preferably 30% or more. If the content of PbO exceeds 85%, crystallization can not be obtained. The content of PbO is preferably 83% or less, more preferably 80% or less.

In the second glass, SiO ₂ is an essential component for increasing the weather resistance of the obtained glass. Further, it is possible to stabilize the glass obtained by the inclusion of SiO _2. The content of SiO ₂ in the second glass is 1% or more and 60% or less. The content of SiO ₂ is preferably 2% or more from the above viewpoint. When the content of SiO ₂ exceeds 60%, in the obtained glass, the glass transition point is raised, and the glass can not flow at the time of sintering. The content of SiO ₂ is preferably 58% or less.

In the second glass, B ₂ O ₃ is an essential component having a function of improving the softening fluidity of the obtained glass and improving the bonding strength with the semiconductor substrate. The content of B ₂ O ₃ in the second glass is 3% or more and 21% or less. From the above viewpoint, the content of B ₂ O ₃ is preferably 4% or more. When the content of B ₂ O ₃ exceeds 21%, there is a possibility that the weather resistance of the glass obtained is deteriorated. The content of B ₂ O ₃ is preferably 20% or less.

The second glass can contain optional components as needed in addition to the above-mentioned essential components. An optional component that is preferably contained in the second glass includes at least one selected from Al ₂ O ₃ and MgO. By containing at least one selected from Al ₂ O ₃ and MgO, weather resistance and glass stabilization can be imparted to the obtained glass. The total content of at least one selected from Al ₂ O ₃ and MgO in the second glass is preferably 0% to 10%. The total content of at least one selected from Al ₂ O ₃ and MgO is more preferably 1% or more. If the total content of at least one selected from Al ₂ O ₃ and MgO exceeds 10%, the softening point may be increased or may not be vitrified. The total content of at least one selected from Al ₂ O ₃ and MgO is more preferably 8% or less.

The first glass and the second glass may each contain other optional components other than the above components. As other optional components, specifically, P ₂ O ₃ , As ₂ O ₅ , Sb ₂ O ₅ , ZnO, Li ₂ O, Na ₂ O, ZrO ₂ , Fe ₂ O ₃ , CuO, Sb ₂ O ₃ , SnO ₂ , MoO ₃ , WO ₃ , MnO, MnO ₂ , CeO ₂ , TiO _{2, and} other various oxide components used for normal glass. These oxide components are used singly or in combination of two or more depending on the purpose. The content of other optional components is preferably 5% or less in total in each of the first glass, the second glass, and the obtained glass.

  In the method for producing glass of the present invention, by mixing the first glass and the second glass, the glass obtained can easily react with the insulating film, thereby facilitating the formation of the insulating film through electrode. Further, after that, the function of facilitating the reaction between the electrode and the semiconductor substrate can be achieved, and the contact resistance can be reduced.

  In the production method of the present invention, from the above viewpoint, the mixing ratio of the first glass and the second glass is preferably 20:80 to 80:20, more preferably 22:78 to 78:22 in terms of mass ratio. The mixing ratio of the first glass and the second glass is particularly preferably a mixing ratio at which the glass composition of the obtained glass becomes the glass composition of the present invention.

  In the production method of the present invention, in the step of mixing the first glass and the second glass, in addition to the first glass and the second glass, the other glass other than the first glass and the second glass. May be added and mixed. The other glass may be one kind or two or more kinds. Also in this case, it is preferable that the glass composition in the obtained glass be the glass composition of the present invention. As other glass, the glass which is easy to adjust so that the glass composition in the glass obtained by mixing 1st glass, 2nd glass, and another glass may turn into the glass composition of the said invention is preferable.

  The first glass and the second glass can each be produced, for example, by the method described below. In the glass of the present invention, the same method can be applied when preparing a raw material mixture and heating and melting and solidifying by a known method.

  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 type glass, An oxide, carbonate, etc. can be used. In the obtained glass, the type and ratio of the raw materials are appropriately adjusted so as to be in the above composition range to obtain a raw material composition.

  Next, the raw material mixture is heated by a known method to obtain a melt. 800-1500 degreeC is preferable and, as for the temperature (melting temperature) which heat-melts, 900-1400 degreeC is more preferable. The heating and melting time is preferably 30 to 300 minutes.

  Thereafter, the melt is cooled and solidified to obtain a first glass, a second glass, or 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 first glass, the second glass or 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 this invention and the glass obtained by the manufacturing method of this invention are used suitably for electrode formation on a semiconductor substrate, for example, electrode formation of a solar cell. In particular, the glass of the present invention and the glass obtained by the production method of the present invention penetrate through the insulating film by fire-through using a conductive paste containing the glass and conductive metal powder on the semiconductor substrate via the insulating film. When forming an electrode, an effect can be exhibited well. Furthermore, when the electrode in electrode formation is an aluminum electrode, a remarkable effect can be exhibited. When forming an electrode using the electrically conductive paste containing the glass of this invention or the glass obtained by the manufacturing method of this invention, it is preferable that glass is a powder.

  The glass powder can be obtained by pulverizing the glass produced as described above by a dry pulverization method or a wet pulverization method. In the case of the wet pulverization method, it is preferable to use water as a solvent. The pulverization can be performed using a pulverizer such as a roll mill, a ball mill, or a jet mill. In the production method of the present invention, the mixing of the first glass and the second glass may be performed before the pulverization. However, after the pulverization of each of the first glass and the second glass, the mixing is performed. It is preferable to do. In addition to the first glass and the second glass, the same applies to the case of mixing other glasses.

  The method of mixing the first glass and the second glass is not particularly limited as long as both are uniformly mixed. When mixing the powder of 1st glass and the powder of 2nd glass, the method of mixing for 1 to 2 hours using V mixer etc. is mentioned, for example. In addition, when mix | blending with an electrically conductive paste, you may mix | blend the predetermined quantity of the powder of 1st glass and the powder of 2nd glass as it is, but the powder of 1st glass and the powder of 2nd glass are mixed beforehand. It is preferable to mix the mixed powder mixed. In addition to the first glass and the second glass, the same applies to the case of mixing other glasses.

The powder of the glass of the present invention, the first glass, the second glass, or the glass obtained by the production method of the present invention has 50% particle diameter D ₅₀ of 0.5 μm or more and 10 μm or less based on volume of the powder. Preferably there is. If D ₅₀ of the glass powder is less than 0.5 [mu] m, it may be dispersed when the paste is difficult. Further, when D ₅₀ of the glass powder exceeds 10 [mu] m, since the point where there is no glass around the conductive metal powder occurs, there is a case adhesion between the electrode and the semiconductor substrate is not sufficient. _{D 50} of the glass powder is more preferably not more than 7.0 .mu.m. The adjustment of the particle size of the glass powder can be carried out, for example, by classification after grinding as required.

In addition, in the accumulated particle size curve of particle size distribution measured using a laser diffraction / scattering type particle size distribution measuring device, D ₅₀ described in the present specification is a particle diameter when the integrated amount occupies 50% on a volume basis. Represents.

<Conductive paste>
The electrically conductive paste of this invention contains the glass powder of the said invention or the glass powder obtained by the manufacturing method of this invention, an electroconductive metal powder, and an organic vehicle. Hereinafter, "powder of the glass of the present invention" or "glass powder" means "powder of the glass of the present invention or powder of the glass obtained by the production method of the present invention" unless otherwise noted. "Glass" likewise means "glass according to the invention or glass obtainable by the process according to the invention". The glass powder is preferably a glass powder having a D ₅₀ of 0.5 μm or more and 10 μm or less. More preferred is a powder of glass having a D ₅₀ of 1.0 μm to 5.0 μm.

  As the conductive metal powder contained in the conductive paste of the present invention, a metal powder usually used for an electrode formed on a semiconductor substrate is used without particular limitation. Specific examples of the conductive metal powder include powders such as Al, Ag, Cu, Au, Pd, and Pt. Among these, Al powder is preferable. When the Al powder is used as the conductive metal powder, the glass of the present invention can reduce the electrical resistance between the electrode and the Si substrate by increasing the reactivity with the insulating film and the reactivity with the Si substrate. The effect of is remarkable.

D ₅₀ of the conductive metal powder is preferably 1 to 10 μm from the viewpoint of suppressing aggregation and obtaining uniform dispersibility. D ₅₀ is 1μm or less, worsened dispersibility in the paste, in 10μm or more, the reactivity is lowered.

  For example, the content of the glass powder in the conductive paste is preferably 0.1 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the conductive metal powder. When the content of the glass powder is less than 0.1 parts by mass, fire-through with the insulating film is not sufficient, and the electric resistance of the electrode part may increase. Moreover, there exists a possibility that the adhesiveness of an electrode and a semiconductor substrate may worsen. On the other hand, when the content of the glass powder exceeds 15 parts by mass, the electrical resistance as an electrode may increase due to a decrease in the proportion of the conductive metal powder. 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 10 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 and the solvent in the organic vehicle is not particularly limited, but is selected so that the obtained 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 5% by mass to 30% by mass with respect to the total amount of the conductive paste. When the content of the organic vehicle is less than 5% by mass, the viscosity of the conductive paste increases, so that coating properties such as printing of the conductive paste decrease, 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 the solid content of an electrically conductive paste will become low, and it will become difficult to obtain sufficient coating film thickness.

  In addition to the glass powder, conductive metal powder, and organic vehicle of the present invention, the conductive paste of the present invention is blended with known additives as necessary and within the limits of the object of the present invention. Can.

As such an additive, various inorganic oxides are mentioned, for example. Specific examples of the inorganic oxide include B ₂ O ₃ , 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 at the time of firing of the conductive paste, and thereby have the function of suppressing the occurrence of blisters on the surface of the electrode after firing. The size of the additives consisting of inorganic oxides is not particularly limited, for example, can be suitably used D ₅₀ is 10μm or less.

  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 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 inorganic oxide at the time of electrode formation may be reduced, and the adhesive strength between the electrode and the semiconductor substrate may be reduced. Moreover, in order to obtain a practical blending effect (suppression of electrical resistance between the electrode and the semiconductor substrate), the lower limit value of the content is preferably 3% by mass or more, more preferably 5% by mass or more.

  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 the preparation of the conductive paste, a known method using a rotary mixer equipped with a stirring blade, a crusher, a roll mill, a ball mill or the like can be applied.

  The conductive paste of the present invention is suitable for electrode formation by firing on a semiconductor substrate, particularly for electrode formation performed by fire-through by partially applying the conductive paste on an insulating film provided on the semiconductor substrate. Used. When the conductive paste of the present invention is used, the glass is an insulating film material while suppressing diffusion of oxygen in the glass contained in the conductive paste to the conductive metal powder at the portion where the conductive paste is applied during firing. As a result of the reaction, the insulating film is melted to obtain an electrode which penetrates the insulating film and is sufficiently in contact with the semiconductor substrate.

  The application and baking of the conductive paste on the insulating film can be performed by the same method as the application and baking in electrode formation performed by conventional fire-through. Examples of the coating method include screen printing and dispensing. The firing temperature depends on the type of conductive metal powder contained, the type of glass powder, and the like, but a temperature of about 600 to 1000 ° C. can be exemplified. The baking time is appropriately adjusted depending on the thickness of the insulating film to be penetrated, the semiconductor substrate, and the like. Moreover, you may provide the drying process at about 100-200 degreeC between application | coating and baking of an electrically conductive paste.

  As described above, the conductive paste of the present invention is suitably used for forming electrodes on a semiconductor substrate with an insulating film by fire-through. As an electrode formed using the conductive paste of the present invention, specifically, a product including an electrode baked on a semiconductor substrate, a solar cell, a diode element, a transistor element, a thyristor, and the like can be given. The conductive paste of the present invention is suitable for forming an electrode by fire-through on a semiconductor substrate with an insulating film in the production of a solar cell.

<Solar cell>
The solar cell of the present invention includes an electrode formed using such a conductive paste of the present invention, specifically, an electrode baked on a semiconductor substrate. In the solar cell of the present invention, at least one of the electrodes is an electrode provided so as to partially penetrate the insulating film and be in contact with the semiconductor substrate by fire through using the conductive paste of the present invention. Is preferred.

  As an electrode that penetrates such an insulating film of a solar cell, for example, a semiconductor that partially penetrates an insulating film that is an antireflection film as an electrode of a light receiving surface of a solar cell using a pn junction type semiconductor substrate The electrode provided in the form which contacts a board | substrate is mentioned. Examples of the insulating material constituting the insulating film that is an antireflection film include silicon nitride, titanium dioxide, silicon dioxide, and aluminum oxide. In this case, the light receiving surface may be one side or both sides of the semiconductor substrate, and the semiconductor substrate may be either n-type or p-type. The electrode provided on the light receiving surface of such a solar cell can be formed by fire through using the conductive paste of the present invention.

  In solar cells such as PERC, a passivation film made of the same insulating material as that of the antireflection film is also provided on the entire back surface, and electrodes are formed on the passivation film so as to partially contact the semiconductor substrate. . Such a back electrode of a PERC solar cell is also an electrode that can be formed by fire-through using the conductive paste of the present invention.

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. For example, a back electrode of a PERC solar cell using a p-type Si substrate or an n-type Si substrate is used as an Al electrode provided to partially penetrate the insulating film and contact the semiconductor substrate by fire through. The back electrode of the PERT (Passivated Emitter, Rear Totally diffused) solar cell, 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, back contact type One electrode of a solar cell, etc. are mentioned.

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

  A solar cell 10 shown in FIG. 1 has a p-type Si substrate 1, an insulating film 2A provided on the upper surface thereof, and an insulating film 2B provided on the lower surface, and penetrates a part of the insulating film 2B to form p-type. An Al electrode 4 in contact with the Si substrate, and an Ag electrode 3 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 a concavo-convex structure formed using, for example, a wet etching method so as to reduce the light reflectance. In addition, the upper and lower sides of a drawing do not necessarily show the upper and lower sides at the time of 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 concavo-convex structure is formed.

  The Al electrode 4 and the Ag electrode 3 are formed as follows using an Al electrode forming conductive paste containing glass powder and Al powder, and an Ag electrode forming conductive paste containing glass powder and Ag powder, respectively. Ru. That is, the insulating film 2B and the insulating film 2A provided on both surfaces of the p-type Si substrate 1 exist without gaps on the entire surface before forming the Al electrode 4 and the Ag electrode 3, and form the Al electrode 4 and the Ag electrode 3. Only the portion where the conductive paste is applied is melted when the conductive paste is fired, so that the Al electrode 4 and the Ag electrode 3 penetrating the insulating film 2B and the insulating film 2A and contacting the p-type Si substrate 1 respectively. It is formed.

The Al electrode 4 penetrates the insulating film 2 B, and after reaching the p layer 1 b of the p-type Si substrate 1, Al diffuses from the Al electrode into the p layer 1 b to diffuse Al directly onto the Al electrode. Form layer 5 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 it is particularly preferable to use it as a conductive paste for forming an Al electrode as described above.

  By using the glass powder of the present invention and the conductive paste of the present invention containing Al powder as the Al electrode forming conductive paste, the glass reacts sufficiently with the insulating material constituting the insulating film during electrode formation. The conductive paste for forming the Al electrode penetrates the insulating film, and the Al electrode 4 sufficiently in contact with the p-type Si substrate 1 is obtained.

  Note that the insulating film and the insulating film included in the solar cell are antireflection films, and the insulating materials listed above can be used as the insulating material constituting the film. The antireflective film may be a single layer film or a multilayer film. The conductive paste of the present invention has high permeability to an insulating film having a layer made of silicon nitride and a layer made of aluminum oxide.

  In the solar cell of the present invention, the electrode is formed using a conductive paste that can easily form an electrode that penetrates the insulating film and ensures contact with the semiconductor substrate when forming the electrode containing the glass powder of the present invention. As a result, the solar cell has improved reliability and productivity.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail with reference to an Example, this invention is not limited to an Example. Examples 1 to 11 are preparation examples of the first glass, and examples 12 to 15 are preparation examples of the glass for the comparative example. Examples 21 to 24 are preparation examples of the second glass. Examples 31-44 and 52-54 are examples of glass, and Examples 45-48, 51, and 55 are comparative examples of glass.

[Examples 1 to 24]
A glass powder having the composition and characteristics shown in Tables 1 to 3 was produced as a first glass, a glass for a comparative example, and a second glass used for producing the glasses of Examples and Comparative Examples. That is, the raw material powders are blended and mixed so as to obtain the compositions shown in Tables 1 to 3 and melted for 30 minutes to 1 hour using a platinum crucible in an electric furnace at 1000 to 1300 ° C. to form thin glass The thin glass was dry-pulverized by a ball mill so that D ₅₀ was in a predetermined range (0.5 to 10 μm), and coarse particles were removed with a 150-mesh sieve.

For the glass of Examples 1 to 15, the glass powder obtained by air flow classification is used as a glass powder to remove coarse particles after the above-mentioned dry pulverization in order to make D ₅₀ smaller within the above-mentioned predetermined range. It was.

About the glass of Examples 21-24, in order to make D ₅₀ smaller within the above-mentioned predetermined range, the glass powder from which coarse particles have been removed after the above-mentioned dry pulverization is further obtained by wet pulverization using water in a ball mill. Glass powder was used as glass powder. In order to obtain a predetermined D ₅₀ during the wet pulverization, the balls were made of alumina having a diameter of 5 mm, and D ₅₀ was adjusted by the pulverization 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.

Example obtained above 15, the glass powder examples 21 to 24, as follows, to measure the glass transition point and _{D 50.}

(Glass transition point; indicated by "DTA Tg" in the table.)
The glass transition point was determined by differential thermal analysis (DTA) using the inflection point of the DTA curve indicating the exothermic-endothermic amount.
_{(D 50)}
In the glass powders of Examples 1 to 15 and Examples 21 to 24, 0.02 g of glass powder was mixed with 60 cc of isopropyl alcohol, and dispersed for 1 minute by ultrasonic dispersion. The sample was put into a micro track measuring machine to obtain a value of D ₅₀ which is 50% particle diameter based on volume.

Hereinafter, the glass powder obtained in Example 1 is indicated by the abbreviation “G1”. The same applies to other examples. Tables 1 to 3 show the glass composition, the abbreviation of the obtained glass powder, the glass transition point, and the D ₅₀ measurement results. In Tables 1 to 3, a blank means that the component is not contained. The same applies to Tables 4 to 6 described later.

[Examples 31 to 48, Examples 51 to 55]
Using the first glass powder (G1 to G11), the glass powder (G12 to G15) for the comparative example, and the second glass powder (G21 to G24) obtained above, the compositions are shown in Tables 4 to 6 The glass powder of the example 31-48 shown and the example 51-55 was manufactured. About the glass powder of Examples 31-48, the 1st glass powder shown in Table 4 and Table 5 or the glass powder for comparative examples and the 2nd glass powder were mixed and manufactured by mass ratio 1: 1. About the glass powder of Examples 51-55, 1st glass G3 and 2nd glass G21 were mixed and manufactured in the ratio shown in Table 6. In each case, mixing was carried out for 1 hour with a V-mixer.

(Evaluation)
Using the glass powders of Examples 31 to 48 and Examples 51 to 55, an Al electrode-forming conductive paste was produced, and the insulating film penetration during electrode formation was evaluated. 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 Tables 4-6.

(1) Preparation of Conductive Electrode for Forming Al Electrode A conductive paste for forming an Al electrode containing the glass powder of each of Examples 31 to 48 and Examples 51 to 55 was manufactured by 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 (manufactured by Toyo Aluminum Co., Ltd.), and then kneaded for 10 minutes by a crusher. Then, glass powder was mix | blended in the ratio of 4 mass parts with respect to 100 mass parts of Al powder, and also knead | mixed for 60 minutes with the crusher, and it was set as the electrically conductive paste for Al electrode formation.

(2) Preparation of Al Electrode and Evaluation of Insulating Film Permeability Using the conductive paste for forming Al electrode prepared above, an insulating film (formed of a silicon nitride layer and an aluminum oxide layer) on a semiconductor substrate as follows. An Al electrode was formed via a two-layer film, and the insulating film penetration was evaluated at that time.

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

  Next, the Al electrode-forming conductive paste obtained above is formed on the insulating film as the antireflection film on the light surface (the surface of the p-type Si substrate) by 325 mesh screen printing, as shown in FIG. A square pattern P1 of × 10 mm and an interval of 1 mm from one side of the pattern P1, and four rectangular patterns P2, P3, P4, and P5 of 1 mm × 10 mm in that order are the long sides of the one side. Were applied in a pattern shape arranged so as to be parallel to each other. Thereafter, firing was performed at a peak temperature of 800 ° C. for 100 seconds using an infrared heating belt furnace to form an Al electrode.

(2-1) Penetration evaluation (1)
Contact resistance component between the Al electrode and the p-type Si semiconductor substrate having the Al electrode formed on the p-type layer side via the insulating film (two-layer film consisting of a silicon nitride layer and an aluminum oxide layer) obtained above Rc [Ω] was evaluated. The contact resistance component Rc [Ω] is measured by measuring the electrical resistance by fixing the anode side of the tester to the pattern P1 of FIG. 2 and applying the cathode side of the tester to each position of the patterns P2, P3, P4 and P5 The contact resistance component Rc [Ω] is determined by separating the sheet resistance component Rs [Ω].

  Specifically, as shown in FIG. 3, a graph in which the distance L [cm] between the anode and the cathode is taken on the horizontal axis and the electric resistance R [Ω] is taken on the vertical axis, the patterns P1 and P2 (L = The electric resistance values measured between 0.1 cm), P3 (L = 0.3 cm), P4 (L = 0.5 cm), and P5 (L = 0.7 cm) are plotted. An approximate straight line is obtained from the obtained four plots, and the value of the intercept of the approximate straight line is 2Rc. In FIG. 3, approximate lines obtained when the glass powders of Example 33 and Example 51 are used are indicated by solid lines and broken lines. In Example 33, the intercept value is 5.8 [Ω], and Rc is determined to be 2.9 [Ω]. In Example 51, the value of the intercept is 35 [Ω], and Rc is determined to be 17.5 [Ω]. The smaller the value of Rc [Ω], the better the penetration.

(2-2) Penetration evaluation (2)
Further, the p-type Si semiconductor substrate having the Al electrode formed on the p-type layer side via the insulating film (the two-layer film consisting of the silicon nitride layer and the aluminum oxide layer) obtained above is hydrochloric acid (hydrogen chloride 35-38% aqueous solution) and water were mixed in an aqueous solution mixed at a mass ratio of 1: 1 for 24 hours to remove the Al electrode from the substrate. Thereafter, whether or not the insulating film was removed by an optical microscope (500 times) was evaluated according to the following criteria.

○: The insulating film has been removed.
X: The location where the insulating film is removed can not be confirmed.

  The evaluation results of penetration are shown in Tables 4 to 6. Further, in FIG. 4, after forming the Al electrode as described above using the Al electrode forming conductive paste containing the glass of Example 33 (Example), the p-type of the p-type Si semiconductor substrate from which the Al electrode has been removed. The optical microscope (500 times) photograph of the layer side surface is shown. According to the photograph of FIG. 4, when the Al electrode is formed, the glass of Example 33 reacts with the two-layer film composed of the silicon nitride layer and the aluminum oxide layer constituting the insulating film, and the obtained Al electrode becomes the Si semiconductor substrate. It can be seen that it has reached FIG. 5 shows the p-type layer side of the p-type Si semiconductor substrate from which the Al electrode was formed after the Al electrode was formed as described above using the Al electrode-forming conductive paste containing the glass of Example 45 (Comparative Example). The light microscope (500x) photograph of the surface is shown. According to the photograph of FIG. 5, at the time of forming the Al electrode, the glass of Example 45 has poor reactivity between the silicon nitride layer constituting the insulating film and the two-layer film composed of the aluminum oxide layer. It can be seen that the semiconductor substrate has not been reached.

  As is apparent from Tables 4 to 6 and FIGS. 4 and 5, the glasses of Examples 31 to 44 and 52 to 54 as examples are suitable for forming an Al electrode of a solar cell.

[Evaluation as a solar cell]
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 32, 33, 37 to 40, and 46 to 48 is a solar simulator (WXS-156, manufactured by Wacom Denso Corp.) -10). 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. The results of the conversion efficiency [%] obtained are also shown in Tables 4 and 5. In Tables 4 and 5, “−” was entered in the column for examples where there was no conversion efficiency evaluation result.

  According to the present invention, in glass used for electrode formation, when an electrode is formed on a semiconductor substrate such as a solar cell via an insulating film, sufficient contact with the semiconductor substrate can be ensured through the insulating film. A glass can be obtained which can form electrodes with low cost and with high production efficiency. Further, in the present invention, an electrically conductive paste containing the glass powder and capable of forming an electrode penetrating an insulating film and ensuring contact with a semiconductor substrate at the time of electrode formation at low cost and with high production efficiency, and the electrically conductive paste Can be used to provide a solar cell with improved reliability and productivity.

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.

Claims (12)

In mol% notation,
5-60% of PbO,
20-50% of B ₂ O ₃
5 to 30% of SiO ₂
K ₂ O 3 to 20%
3 to 20% of CaO
Glass characterized by containing.   The glass according to claim 1, further comprising 3 to 20% of BaO in terms of mole percent. Furthermore, mol% notation in SrO, _Al 2 _{O 3} and claim 1 or 2 glass according contains 0-10% of at least one of a total selected from MgO. In mole% notation,
B ₂ O ₃ 35 to 60%
1 to 40% of K ₂ O,
3 to 30% of CaO
A first glass containing 5 to 10% of SiO ₂ and substantially free of PbO;
In mole% notation,
20-85% of PbO,
₁ to 60% of SiO ₂
Comprising the step of mixing the second glass containing B ₂ O ₃ 3~21%, the production method of the glass.   The method for producing glass according to claim 4, wherein the first glass further contains 1 to 25% of BaO in terms of mol%.   The method for producing glass according to claim 4 or 5, wherein the first glass further contains 0 to 15% of SrO in terms of mol%. The second glass The method for producing a glass according to any one of claims 4-6, further containing 0-10% total of at least one selected from _Al 2 _{O 3} and MgO in mol% notation.   The manufacturing method of the glass of any one of Claims 4-7 whose mixing ratio of the said 1st glass and the said 2nd glass is 20: 80-80: 20 by mass ratio.   The method for producing a glass according to any one of claims 4 to 8, wherein the glass according to any one of claims 1 to 3 is obtained by mixing the first glass and the second glass. Powder powder of glass containing 5 to 60% of PbO, 20 to 50% of B ₂ O ₃ , 5 to 30% of SiO ₂ , ₃ to 20% of K ₂ O, and 3 to 20% of CaO in mol% notation And a conductive paste containing conductive metal powder and an organic vehicle. The first containing 35 to 60% of B ₂ O ₃ , 1 to 40% of K ₂ O, 3 to 30% of CaO, 5 to 10% of SiO ₂ and substantially free of PbO in mol% notation A powder of a glass, and a mixture comprising a powder of a second glass containing 20 to 85% of PbO, ₁ to 60% of SiO ₂ and ₃ to 21% of B ₂ O ₃ in terms of mol%,
Conductive paste containing conductive metal powder and organic vehicle.   A solar cell comprising an electrode formed using the conductive paste according to claim 10 or 11.

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