Glass, glass powder, conductive paste, and solar cells

Abstract

To provide a glass that can ensure sufficient contact between an insulation film and a semiconductor substrate when forming an electrode on the semiconductor substrate, such as the solar cell, through the insulation film, and can also improve conversion efficiency of the solar cell, and provide a glass powder composed of the glass, a conductive paste containing the glass powder, and a solar cell that has improved conversion efficiency by use of the conductive paste.SOLUTION: A glass contains, in mass% in terms of oxides, V2O5 of 40% or more and 85% or less, ZnO of 0.1% or more and 20% or less, BaO of 0.1% or more and 30% or less, Al2O3 of 0.1% or more and 20% or less, and B2O3 of 1.0% or more and 60% or less. A glass powder is composed of the glass and has D50 of 0.8-6.0 μm when D50 is a 50% particle size on a volume basis in cumulative size distribution.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to glass, glass powder, conductive paste, and solar cells, and more particularly to glass, glass powder, conductive paste using the same, and solar cells having electrodes formed by the conductive paste, which are suitable for forming electrodes of solar cells. [Background technology]

[0002] 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 in various applications. This conductive layer serving as an electrode is formed by applying a conductive paste, in which conductive metal powders such as aluminum (Al), silver (Ag), and copper (Cu) and glass powder are dispersed in an organic vehicle, onto the semiconductor substrate and firing it at the temperature necessary for electrode formation.

[0003] In this manner, when forming electrodes on a semiconductor substrate, an insulating film may be formed over the entire surface of the semiconductor substrate where the electrodes are formed, and the patterned electrodes may be formed so that they partially penetrate the insulating film and come into contact with the semiconductor substrate.

[0004] For example, in a solar cell, an anti-reflective coating is provided on the semiconductor substrate that serves as the light-receiving surface, and electrodes are arranged in a pattern on top of it. The anti-reflective coating is intended to reduce surface reflectivity while maintaining sufficient visible light transmittance to improve light-receiving efficiency, and is usually composed of insulating materials such as silicon nitride, titanium dioxide, silicon dioxide, or aluminum oxide.

[0005] Furthermore, in solar cells such as PERC (Passivated Emitter and Rear Contact), a passivation film made of the same insulating material as the anti-reflective film is provided on the entire back surface, and electrodes are formed on this passivation film so that they partially contact the semiconductor substrate.

[0006] Electrodes need to be formed in contact with the semiconductor substrate. Therefore, during electrode formation, the insulating film is removed according to the pattern of the electrode to be formed, and the electrode is formed in the area where the insulating film has been removed. One method for removing the insulating layer is to remove it physically using a laser or the like, but this method involves an increase in manufacturing steps and equipment introduction costs. Therefore, in recent years, a method called "fire-through" has been adopted, in which a conductive paste containing conductive metal powder and glass powder, i.e., a paste-like electrode material, is applied to the insulating film and heat-treated to penetrate the insulating film into the conductive paste.

[0007] The above technique for forming electrodes on a semiconductor substrate has also been applied to forming electrodes on pn-junction type semiconductor substrates in solar cells. As an example of such a conductive paste containing glass powder, Patent Document 1 describes a paste for electronic device electrodes.

[0008] Patent Document 1 describes a lead-tellurium-based glass composition, disclosing a glass composition that, for example, contains 44.36% by weight of PbO, 0.49% by weight of B2O3, 0.78% by weight of Li2O, 6.79% by weight of Bi2O3, and 47.58% by weight of TeO2, in terms of oxides.

[0009] Furthermore, as described in Patent Document 2, a conductive paste for the electrodes of a solar cell element may be prepared using a mixed glass frit, which is a mixture of glass frits of different compositions. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2014-49743 [Patent Document 2] Japanese Patent Publication No. 2014-209598 [Overview of the project] [Problems that the invention aims to solve]

[0011] As disclosed in Patent Document 1, for the glass used for forming the electrodes of a solar cell, technologies for improving the formability of the electrodes and the electrical resistance between the electrodes and the semiconductor substrate have been developed.

[0012] However, with the glass described in Patent Document 1, sufficient contact between the electrodes, the insulating film, and the semiconductor substrate cannot be ensured.

[0013] Particularly in solar cells such as PERC, even if the composition of the glass and the particle size distribution of the glass powder used for electrode formation are adjusted, at present, technologies for reducing the electrical resistance between the electrodes and the semiconductor substrate and improving the conversion efficiency of the solar cell are still under development.

[0014] The present invention provides a glass used for electrode formation, which, when mixed with, for example, a lead-based glass and used, can sufficiently ensure contact with the insulating film and the semiconductor substrate when forming an electrode on a semiconductor substrate such as a solar cell via the insulating film, and can improve the conversion efficiency of the solar cell. The present invention further aims to provide a glass obtained by mixing the glass with a lead-based glass, a glass powder composed of the glass, a conductive paste containing the glass powder, and a solar cell with improved conversion efficiency by using the conductive paste.

Means for Solving the Problems

[0015] The inventors of the present invention have found that the above problems can be solved by setting the glass composition within a specific range, and have completed the present invention. The present invention provides a glass, a glass powder, a conductive paste, and a solar cell having the following configurations.

[0016] [1] In terms of mass% representation in terms of oxides, V2O5 is 40% or more and 85% or less, ZnO is 0.1% or more and 20% or less, BaO is 0.1% or more and 30% or less, Al2O3 is 0.1% or more and 20% or less, and B2O3 content: 1.0% to 60% Includes glass. [2] The glass described in [1], which contains 1% or more ZnO, 5% or more BaO, and 1% or more Al2O3, expressed as an oxide-based mass percentage. [3] The glass described in [1] or [2], wherein the total content of V2O5 and B2O3 (V2O5 + B2O3), expressed as an oxide-based mass percentage, is 50% or more and 90% or less. [4] Glass as described in any one of [1] to [3], wherein the total content of BaO, ZnO, and B2O3 (BaO + ZnO + B2O3), expressed as an oxide-based mass percentage, is 15% or more and 55% or less. [5] A glass as described in any one of [1] to [4], wherein the total content of BaO and Al2O3 (BaO + Al2O3), expressed as an oxide-based mass percentage, is 10% or more and 30% or less. [6] A glass according to any one of [1] to [5], wherein, expressed as an oxide-based mass percentage, the ratio (BaO+ZnO+Al2O3) / (V2O5+B2O3) of the total content of BaO, ZnO, and Al2O3 (BaO+ZnO+Al2O3) to the total content of V2O5 and B2O3 (V2O5+B2O3) is 0.1 or more and 1.0 or less. [7] A glass according to any one of [1] to [6], wherein the glass transition temperature is 250°C or higher and 500°C or lower. Glass powder made of glass as described in any one of [8][1] to [7], wherein the 50% particle size on a volume basis in the cumulative particle size distribution is D 50 When that happens, D 50 Glass powder having a particle size of 0.8 μm or more and 6.0 μm or less. [9] Expressed as mass % on an oxide basis, PbO content between 15% and 70% TeO2 between 0% and 50%, V2O5 is between 2% and 25%. ZnO is present in a concentration of 0.05% to 4%. BaO is present in a concentration of 0.1% to 8%. Al2O3 in a concentration of 0.05% to 3% and B2O3 in an amount of 0.05% to 11%. Includes glass.

[10] The glass described in [9], wherein the total content of V2O5 and B2O3 (V2O5 + B2O3), expressed as an oxide-based mass percentage, is 2.05% or more and 22% or less.

[11] The glass described in [9] or

[10] , wherein the total content of BaO, ZnO, and B2O3 (B2O3 + BaO + ZnO), expressed as an oxide-based mass percentage, is 1% or more and 14% or less.

[12] A glass according to any one of [9] to

[11] , wherein the total content of BaO and Al2O3 (BaO + Al2O3), expressed as an oxide-based mass percentage, is 0.5% or more and 8% or less.

[13] Glass as described in any one of [9] to

[12] , wherein the total content of PbO, TeO2, and V2O5 (PbO + TeO2 + V2O5), expressed as an oxide-based mass percentage, is 50% or more and 80% or less.

[14] A glass according to any one of [9] to

[13] , wherein, expressed as an oxide-based mass percentage, the ratio (BaO+ZnO+Al2O3) / (V2O5+B2O3) of the total content of BaO, ZnO, and Al2O3 (BaO+ZnO+Al2O3) to the total content of V2O5 and B2O3 (V2O5+B2O3) is 0.1 or more and 1.0 or less.

[15] A glass as described in any one of [9] to

[14] , wherein the ratio of V2O5 to PbO (V2O5 / PbO) is 0.05 or more and 1.0 or less, expressed as a mass percentage on an oxide basis. Glass powder made of glass as described in any one of

[16] [9]~

[15] , wherein the 50% particle size on a volume basis in the cumulative particle size distribution is D 50 When that happens, D 50 Glass powder having a particle size of 0.8 μm or more and 6.0 μm or less. A glass powder made from any one of the glass described in

[17] , [1] to [7] and [9] to

[15] , or a conductive paste containing the glass powder described in [8] or

[16] , conductive metal powder, and an organic vehicle. A solar cell comprising electrodes formed using the conductive paste described in

[18]

[17] .

[19] 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, A second insulating film having at least one opening is provided on the side of the silicon substrate opposite to the sunlight-receiving surface, A first electrode that penetrates a portion of the first insulating film and contacts the silicon substrate, A second electrode that partially contacts the silicon substrate through the opening of the second insulating film, A solar cell equipped with, The first electrode is a solar cell comprising a metal containing at least one selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt, and a glass containing, in terms of mass percent on an oxide basis, 15% to 70% PbO, 0% to 50% TeO2, 2% to 25% V2O5, 0.05% to 4% ZnO, 0.1% to 8% BaO, 0.05% to 3% Al2O3, and 0.05% to 11% B2O3. [Effects of the Invention]

[0017] The glass and glass powder made from the present invention, when used together with a conductive component in a conductive paste, promote the deposition of conductive metals when forming electrodes on a semiconductor substrate such as a solar cell via an insulating film. This ensures sufficient contact between the insulating film and the semiconductor substrate, thereby improving the conversion efficiency of the solar cell.

[0018] In the present invention, by containing the glass powder, it is possible to provide a conductive paste that can improve the conversion efficiency of a solar cell when electrodes are formed using the same, and a solar cell with improved conversion efficiency by using the conductive paste. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a schematic cross-sectional view of an example of a p-type Si substrate double-sided photodetector solar cell in which electrodes are formed using the conductive paste according to this embodiment. [Figure 2] Figure 2 shows the electrode pattern formed on the Si substrate used to evaluate the contact resistance Rc [Ω]. [Modes for carrying out the invention]

[0020] Embodiments of the present invention will be described below. In the following description, unless otherwise specified, the "%" in the content of each component of glass refers to the mass percentage in terms of oxides. In this specification, the "~" indicating a numerical range includes both upper and lower limits.

[0021] The content of each component in the glass of the present invention is determined from the results of inductively coupled plasma (ICP-AES) analysis or electron probe microanalyzer (EPMA) analysis of the obtained glass.

[0022] In the following description of the glass components, "conductive paste" means "conductive paste containing the glass of the present invention," and "electrode" means "an electrode obtained using the conductive paste containing the glass of the present invention."

[0023] <Glass - First Invention> The following describes the glass of the first invention, which is one embodiment of the present invention. The glass of the first invention contains, in terms of oxide mass percentage, 40% to 85% of V2O5, 0.1% to 20% of ZnO, 0.1% to 30% of BaO, 0.1% to 20% of Al2O3, and 1.0% to 60% of B2O3.

[0024] In the glass of the first invention, V2O5 is an essential component for improving the softening and fluidity of the glass and for obtaining contact between the electrode, the insulating film, and the semiconductor substrate in an electrode obtained using a conductive paste containing the glass.

[0025] To improve the contact between the electrode, the insulating film, and the semiconductor substrate, it is important to promote the deposition of conductive metal at the interface between the electrode, the insulating film, and the semiconductor substrate. In particular, when the conductive metal is Ag, some of the V2O5 becomes V2O3 or V2O4, promoting the deposition of Ag at the interface and easily adjusting the contact between the electrode, the insulating film, and the semiconductor substrate. As a result, the subsequent reaction between the electrode and the semiconductor substrate is promoted, reducing contact resistance and improving the adhesion between the electrode and the insulating film.

[0026] V2O5 further enhances the wettability of conductive metals in conductive pastes, thereby improving the bonding between conductive metals and reducing the electrical resistance of electrodes. It also allows for adjustment of weather resistance by controlling the formation of oxide films on the conductive metal surface during electrode formation. This effect is particularly pronounced when the conductive metal is aluminum (Al).

[0027] The glass of the first invention contains V2O5 in a proportion of 40% to 85%. By having a V2O5 content of 40% or more, conductive metals, particularly Ag, can be sufficiently deposited at the interface between the electrode and the insulating film and semiconductor substrate, improving the contact between the electrode and the insulating film and semiconductor substrate, and ensuring sufficient bonding between the conductive metals in the electrode. The V2O5 content is preferably 44% or more, more preferably 50% or more, and even more preferably 54% or more.

[0028] Furthermore, by limiting the V2O5 content to 85% or less, excessive deposition of conductive metals and a decrease in bonding strength due to excessive reaction between the glass and the insulating film are suppressed. The V2O5 content is preferably 78% or less, more preferably 68% or less, and even more preferably 65% ​​or less.

[0029] In the glass of the first invention, ZnO is an essential component. ZnO is a component that suppresses the crystallization of the glass and improves the reactivity between the glass and the insulating film on a semiconductor substrate such as a Si substrate or the Si substrate itself. The glass of the first invention contains ZnO in a proportion of 0.1% to 20%. By setting the ZnO content to 0.1% or more, the reactivity between the glass and the insulating film on a semiconductor substrate such as a Si substrate or the Si substrate itself is increased, sufficient bonding strength can be obtained, and the increase in electrical resistance between the electrode and the semiconductor substrate can be suppressed. The ZnO content is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more. By setting the ZnO content to 20% or less, excessive reaction between the glass and the insulating film during electrode formation can be suppressed, and electrode bonding strength and weather resistance such as acid resistance can be improved. The ZnO content is preferably 15% or less, more preferably 14% or less, and even more preferably 10% or less.

[0030] In the glass of the first invention, BaO is an essential component for reducing the contact resistance between the electrode and the semiconductor substrate. BaO also functions as a glass component, stabilizing the glass as a modifying oxide. The BaO content in the glass of the first invention is 0.1% to 30%. By having a BaO content of 0.1% or more, the increase in contact resistance between the electrode and the semiconductor substrate during electrode formation can be suppressed, and for example, the conversion efficiency in solar cells can be improved. The BaO content is preferably 5% or more, more preferably 7% or more, and even more preferably 10% or more. By having a BaO content of 30% or less, crystallization of the glass can be suppressed. The BaO content is preferably 27% or less, more preferably 25% or less, and even more preferably 22% or less.

[0031] The glass of the first invention contains Al2O3 in a proportion of 0.1% to 20%. An Al2O3 content of 0.1% or more improves weather resistance and stabilizes the glass. The Al2O3 content is preferably 1% or more, more preferably 1.5% or more, and even more preferably 2% or more. An Al2O3 content of 20% or less suppresses the rise in the glass transition temperature, allowing the glass to flow sufficiently during sintering. The Al2O3 content is preferably 15% or less, more preferably 12% or less, and even more preferably 10% or less.

[0032] As one embodiment of the glass of the first invention, for example, a preferred embodiment is one in which the ZnO content is 1% or more, the BaO content is 5% or more, and the Al2O3 content is 1% or more.

[0033] In the glass of the first invention, B2O3 is an essential component. B2O3 has the function of improving the softening and fluidity of the glass and improving the contact between the electrode, the insulating film, and the semiconductor substrate. In addition, B2O3 is a component that forms the network structure of the glass and is a component that stabilizes the glass.

[0034] The glass of the first invention contains B2O3 in a proportion of 1.0% to 60%. By having a B2O3 content of 1.0% or more, the glass can flow sufficiently during electrode formation, and sufficient contact between the electrode, the insulating film, and the semiconductor substrate can be ensured. The B2O3 content is preferably 1.5% or more, and more preferably 3% or more. Furthermore, by having a B2O3 content of 60% or less, weather resistance can be improved. The B2O3 content is preferably 50% or less, more preferably 35% or less, and even more preferably 25% or less.

[0035] The glass of the first invention preferably has a total content of V2O5 and B2O3 (V2O5 + B2O3) of 50% or more, more preferably 55% or more, and even more preferably 60% or more. By setting (V2O5 + B2O3) to 50% or more, the softening point of the glass is suppressed to prevent a decrease in fluidity, the glass flows sufficiently during cell firing, and sufficient contact between the electrode, insulating film and semiconductor substrate can be ensured. In addition, sufficient bonding between conductive metals in the electrode is achieved. The (V2O5 + B2O3) is preferably 90% or less, more preferably 85% or less, and even more preferably 82% or less. By setting (V2O5 + B2O3) to 90% or less, weather resistance such as acid resistance can be improved.

[0036] The glass of the first invention preferably has a total content of BaO, ZnO, and B2O3 (BaO+ZnO+B2O3) of 15% or more, more preferably 18% or more, and even more preferably 20% or more. By setting (BaO+ZnO+B2O3) to 15% or more, the stability of the glass is improved, and when cellularized, the reactivity with the substrate is increased, suppressing an increase in contact resistance. Preferably, (BaO+ZnO+B2O3) is 55% or less, more preferably 50% or less, and even more preferably 45% or less. By setting (BaO+ZnO+B2O3) to 55% or less, excessive reaction between the glass and the substrate is suppressed, which can worsen the appearance of the electrodes, and weather resistance such as acid resistance can be improved. In other words, by keeping (BaO+ZnO+B2O3) within the above range, it is possible to reduce contact resistance while maintaining weather resistance.

[0037] The glass of the first invention preferably has a total content of BaO and Al2O3 (BaO + Al2O3) of 10% or more, more preferably 13% or more, and even more preferably 15% or more. By having (BaO + Al2O3) of 10% or more, sufficient stability as glass can be ensured. Preferably, (BaO + Al2O3) is 30% or less, more preferably 28% or less, and even more preferably 27% or less. By having (BaO + Al2O3) of 30% or less, a decrease in the fluidity of the glass can be suppressed and sufficient contact between the electrode, the insulating film and the semiconductor substrate can be ensured. That is, if (BaO + Al2O3) is within the above range, sufficient contact can be ensured while maintaining weather resistance.

[0038] The glass of the first invention preferably has a ratio (BaO+ZnO+Al2O3) / (V2O5+B2O3) of 0.1 or more, more preferably 0.2 or more, and even more preferably 0.25 or more, of the total content of BaO, ZnO, and Al2O3 (BaO+ZnO+Al2O3) to the total content of V2O5 and B2O3 (V2O5+B2O3). A ratio of (BaO+ZnO+Al2O3) / (V2O5+B2O3) of 0.1 or more improves the stability of the glass. Furthermore, a ratio of (BaO+ZnO+Al2O3) / (V2O5+B2O3) of 1.0 or less is preferable, more preferably 0.7 or less, and even more preferably 0.6 or less. A ratio of (BaO+ZnO+Al2O3) / (V2O5+B2O3) of 1.0 or less ensures sufficient contact between the electrode, the insulating film, and the semiconductor substrate.

[0039] The glass of the first invention may contain other optional components (hereinafter also referred to as "other components") in addition to the above components, to the extent that they do not impair the purpose of the present invention. Specifically, examples of other components include various oxide components commonly used in glass, such as PbO, P2O3, Sb2O5, Li2O, Na2O, K2O, ZrO2, Fe2O3, CuO, Sb2O3, SnO2, MnO, MnO2, CeO2, TiO2, SiO2, SrO, MoO3, and WO3. Furthermore, it is preferable that the glass of the first invention is substantially free of Bi2O3. Because Bi2O3 is easily reduced, it may be reduced to metallic Bi during melting and precipitate in the glass. If metallic Bi is included in the glass, leakage current may occur in the solar cell, potentially leading to a decrease in conversion efficiency. Substantially free of Bi2O3 means that it is 0.04% or less.

[0040] Other components may be used individually or in combination of two or more, depending on the purpose. The content of each optional component is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and even more preferably 5% or less. Furthermore, the total content of the other components is preferably 20% or less, and more preferably 10% or less.

[0041] The glass of the first invention preferably has a glass transition temperature of 250°C or higher and 500°C or lower. Setting the glass transition temperature to 250°C or higher suppresses excessive fluidity of the glass during sintering. If the fluidity of the glass is too high, for example, when used in a conductive paste, the conductive component and the glass may separate, and the resulting electrode may not provide sufficient electrical conductivity. Furthermore, setting the glass transition temperature to 250°C or higher suppresses excessive reaction of the glass with the insulating film during electrode formation, preventing deterioration of the electrode's appearance. Setting the glass transition temperature to 500°C or lower allows the glass to flow sufficiently during sintering, stabilizing its properties. The glass transition temperature is more preferably 280°C or higher and 450°C or lower, and even more preferably 300°C or higher and 400°C or lower.

[0042] In this invention, the glass transition temperature is obtained by measuring it using a Rigaku differential thermal analysis (DTA) instrument TG8110 at a heating rate of 10°C / min and determining the first inflection point of the DTA chart.

[0043] The method for manufacturing the glass of the first invention is not particularly limited. Specifically, it can be manufactured by the following method, for example.

[0044] First, a raw material mixture is prepared. The raw materials are not particularly limited as long as they are the raw materials used in the manufacture of ordinary oxide-based glass, and oxides, carbonates, etc., can be used. The raw material mixture is prepared by appropriately adjusting the type and proportion of the raw materials so that the resulting glass falls within the above composition range.

[0045] Next, the raw material mixture is heated by a known method to obtain a molten product. The heating and melting temperature (melting temperature) is preferably 1100 to 1600°C, and more preferably 1300 to 1600°C. The heating and melting time is preferably 30 to 300 minutes.

[0046] Subsequently, the molten material is cooled and solidified to obtain the glass of the present invention. The cooling method is not particularly limited. Rapid cooling methods such as using a rollout machine, press machine, or dropping into a cooling liquid can also be employed. The resulting glass is preferably completely amorphous, i.e., has a crystallinity of 0%. However, it may contain crystalline portions as long as it does not impair the effects of the present invention.

[0047] The glass of the first invention obtained in this way may take any form. For example, it may be in the form of a block, a plate, a thin plate (flake), a powder, etc.

[0048] The glass of the first invention has the function of a binder and is preferably used in a conductive paste. A conductive paste containing the glass of the first invention is suitably used, for example, for forming electrodes in solar cells. When the glass of the first invention is included in a conductive paste, the glass is preferably in powder form. Furthermore, when the glass of the first invention is included in a conductive paste, it is preferable to use it together with other glass from the viewpoint of reducing the contact resistance between the electrode and the semiconductor substrate. The other glass is preferably a lead-based glass, and more preferably contains 20% or more PbO, and more preferably 25% or more.

[0049] Furthermore, the other glass is more preferably a lead-tellurium-based glass. Specifically, the other glass contains PbO and TeO2, and the total of PbO and TeO2 (PbO + TeO2) is preferably 40% or more, and more preferably 50% or more.

[0050] <The Glass of the Present Invention - Second Invention> The following describes the glass of the second invention, which is one embodiment of the present invention. One embodiment of the second invention is, for example, a glass in which the glass of the first invention described above is added to a glass containing PbO.

[0051] The content of the glass of the first invention in the glass of the second invention is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of promoting the deposition of conductive metal and lowering contact resistance. Furthermore, the upper limit is usually preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of fire-through properties.

[0052] The glass of the second invention contains PbO at a ratio of 15% to 70% by mass, expressed as an oxide equivalent. It contains TeO2 at a concentration of 0% to 50%, V2O5 at a concentration of 2% to 25%, ZnO at a concentration of 0.05% to 4%, BaO at a concentration of 0.1% to 8%, Al2O3 at a concentration of 0.05% to 3%, and B2O3 at a concentration of 0.05% to 11%.

[0053] The glass of the second invention contains PbO in a proportion of 15% to 70%. By having a PbO content of 15% or more, fire-through is promoted, and sufficient contact between the electrode, the insulating film, and the semiconductor substrate can be ensured. The PbO content is preferably 17% or more, more preferably 20% or more, and even more preferably 22% or more.

[0054] Furthermore, by limiting the PbO content to 70% or less, excessive fire-through can be prevented. The PbO content is preferably 65% ​​or less, more preferably 40% or less, and even more preferably 30% or less.

[0055] The glass of the second invention contains TeO2 in a proportion of 0% to 50%. When TeO2 is included, its content is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more, from the viewpoint of wettability with Ag particles. Furthermore, a TeO2 content of 50% or less ensures sufficient fire-through properties. The TeO2 content is preferably 45% or less, more preferably 40% or less, and even more preferably 35% or less.

[0056] The glass of the second invention contains V2O5 in a proportion of 2% to 25%. By having a V2O5 content of 2% or more, the contact between the electrode, the insulating film, and the semiconductor substrate is improved, and the bonding between conductive metals in the electrode becomes sufficient. The V2O5 content is preferably 3% or more, more preferably 4% or more, and even more preferably 5% or more. By having a V2O5 content of 25% or less, excessive deposition of conductive metal due to excessive reaction between the glass and the insulating film, and a decrease in bonding strength due to excessive reaction between the glass and the insulating film are suppressed. The V2O5 content is preferably 20% or less, more preferably 18% or less, and even more preferably 15% or less.

[0057] The glass of the second invention contains ZnO in a proportion of 0.05% to 4%. By setting the ZnO content to 0.05% or more, the reactivity between the glass and the insulating film on the semiconductor substrate such as the Si substrate is increased, sufficient bonding strength can be obtained, and the increase in electrical resistance between the electrode and the semiconductor substrate can be suppressed. By setting the ZnO content to 4% or less, excessive reaction between the glass and the insulating film during electrode formation can be suppressed, improving bonding strength and weather resistance such as acid resistance. The ZnO content is preferably 3.5% or less, more preferably 3% or less, and even more preferably 2% or less.

[0058] The glass of the second invention contains BaO in a proportion of 0.1% to 8%. By setting the BaO content to 0.1% or more, the increase in contact resistance between the electrode and the semiconductor substrate during electrode formation can be suppressed, and for example, the conversion efficiency in a solar cell can be improved. The BaO content is preferably 0.3% or more, and more preferably 0.5% or more. By setting the BaO content to 8% or less, crystallization of the glass can be suppressed. The BaO content is preferably 6% or less, more preferably 4% or less, and even more preferably 3% or less.

[0059] The glass of the second invention contains Al2O3 in a proportion of 0.05% to 3%. By having an Al2O3 content of 0.05% or more, weather resistance can be improved and the glass can be stabilized. The Al2O3 content is preferably 0.1% or more, more preferably 0.3% or more, and even more preferably 0.5% or more. By having an Al2O3 content of 3% or less, the rise in the glass transition temperature is suppressed and the glass does not become unable to flow during sintering. The Al2O3 content is preferably 2.8% or less, more preferably 2.5% or less, and even more preferably 2% or less.

[0060] The glass of the second invention contains B2O3 in a proportion of 0.05% to 11%. By having a B2O3 content of 0.05% or more, B is easily diffused into the Si semiconductor substrate during electrode formation. The B2O3 content is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.3% or more. Furthermore, by having a B2O3 content of 11% or less, weather resistance can be improved. The B2O3 content is preferably 8% or less, more preferably 6% or less, and even more preferably 5% or less.

[0061] Furthermore, it is preferable that the glass of the second invention is substantially free of Bi2O3. Because Bi2O3 is easily reduced, it may be reduced to metallic Bi during melting and precipitate in the glass. If metallic Bi is present in the glass, leakage current may be generated in the solar cell, potentially leading to a decrease in conversion efficiency. Substantially free of Bi2O3 means that the amount is 0.04% or less.

[0062] The glass of the second invention preferably has a total content of V2O5 and B2O3 (V2O5 + B2O3) of 2.05% or more, more preferably 4% or more, and even more preferably 6% or more. By having (V2O5 + B2O3) of 2.05% or more, the softening point of the glass is suppressed to be raised, preventing a decrease in fluidity, allowing the glass to flow sufficiently during cell firing, and ensuring sufficient contact between the electrode, the insulating film, and the semiconductor substrate. In addition, sufficient bonding between conductive metals is achieved in the electrode. The (V2O5 + B2O3) is preferably 22% or less, more preferably 20% or less, and even more preferably 18% or less. By having (V2O5 + B2O3) of 22% or less, weather resistance such as acid resistance can be improved.

[0063] The glass of the second invention preferably has a total content of BaO, ZnO, and B2O3 (B2O3+BaO+ZnO) of 1% or more, more preferably 2% or more, and even more preferably 3% or more. By setting (B2O3+BaO+ZnO) to 1% or more, the stability of the glass is improved, and when cellularized, the reactivity with the substrate is increased, suppressing an increase in contact resistance. Preferably, (B2O3+BaO+ZnO) is 14% or less, more preferably 12% or less, and even more preferably 10% or less. By setting (BaO+ZnO+B2O3) to 14% or less, excessive reaction between the glass and the substrate is suppressed, which can worsen the appearance of the electrodes, and weather resistance such as acid resistance can be improved. In other words, by keeping (BaO+ZnO+B2O3) within the above range, it is possible to reduce contact resistance while maintaining weather resistance.

[0064] The glass of the second invention preferably has a total content of BaO and Al2O3 (BaO + Al2O3) of 0.5% or more, more preferably 1% or more, and even more preferably 1.5% or more. By having (BaO + Al2O3) of 0.5% or more, sufficient stability as glass can be ensured. Preferably, (BaO + Al2O3) is 8% or less, more preferably 6% or less, and even more preferably 4% or less. By having (BaO + Al2O3) of 8% or less, a decrease in the fluidity of the glass can be suppressed and sufficient contact between the electrode, the insulating film and the semiconductor substrate can be ensured. That is, if (BaO + Al2O3) is within the above range, sufficient contact can be ensured while maintaining weather resistance.

[0065] The glass of the second invention preferably has a total content of PbO, TeO2, and V2O5 (PbO + TeO2 + V2O5) of 50% or more, more preferably 55% or more, and even more preferably 58% or more. Having (PbO + TeO2 + V2O5) of 50% or more ensures sufficient contact between the electrode, the insulating film, and the semiconductor substrate. Having (PbO + TeO2 + V2O5) of 80% or less is preferable, more preferably 70% or less, even more preferably 68% or less, and particularly preferable 65% or less. Having (PbO + TeO2 + V2O5) of 80% or less suppresses excessive reaction of the glass with the substrate, improves the appearance of the electrode, and enhances weather resistance such as acid resistance.

[0066] The glass of the second invention preferably has a ratio (BaO+ZnO+Al2O3) / (V2O5+B2O3) of 0.1 or more, more preferably 0.2 or more, and even more preferably 0.25 or more, of the total content of BaO, ZnO, and Al2O3 (BaO+ZnO+Al2O3) to the total content of V2O5 and B2O3 (V2O5+B2O3). The ratio (BaO+ZnO+Al2O3) / (V2O5+B2O3) is preferably 1.0 or less, more preferably 0.7 or less, and even more preferably 0.6 or less. By having a ratio (BaO+ZnO+Al2O3) / (V2O5+B2O3) of 1.0 or less, crystallization is suppressed and sufficient contact between the electrode, the insulating film, and the semiconductor substrate can be ensured.

[0067] The glass of the second invention preferably has a ratio of V2O5 to PbO (V2O5 / PbO) of 0.05 or more, more preferably 0.1 or more, and even more preferably 0.15 or more. A (V2O5 / PbO) ratio of 0.05 or more allows the reduction effect of V2O3 to be fully exerted, promoting the deposition of conductive components such as Ag and ensuring sufficient contact. A (V2O5 / PbO) ratio of 1.0 or less is preferable, more preferably 0.7 or less, and even more preferably 0.6 or less. A (V2O5 / PbO) ratio of 1.0 or less suppresses excessive outflow of V2O5 glass to the interface, allowing the passivation film to fire through sufficiently.

[0068] The manufacturing method of the glass of the second invention is not particularly limited and can be manufactured in the same manner as the glass of the first invention. Also, as described above, for example, it can be manufactured by adding the glass of the first invention described above to a glass containing PbO.

[0069] The glass of the second invention may be in any form, similar to the glass of the first invention. For example, it may be in the form of a block, a plate, a thin plate (flake-like), a powder, or the like.

[0070] The glass of the second invention has a function as a binder and has weather resistance, and is preferably used in a conductive paste. The conductive paste containing the glass of the second invention is suitably used, for example, for forming an electrode of a solar cell. When the glass of the second invention is contained in the conductive paste, the glass is preferably in powder form.

[0071] <Glass powder> The glass powder of the present invention is composed of the glass of the present invention, and D 50 is preferably 0.8 μm or more and 6.0 μm or less. This D 50 range is a particularly preferable range for use in a conductive paste. When D 50 is 0.8 μm or more, the dispersibility when made into a conductive paste is further improved. Also, when D 50 is 6.0 μm or less, it is difficult for locations where no glass powder exists to occur around the conductive metal powder, so the adhesiveness between the electrode and a semiconductor substrate or the like is further improved. In this case, D 50 is more preferably 1.0 μm or more, and even more preferably 1.2 μm or more. D 50 is more preferably 5.0 μm or less, and even more preferably 3 μm or less.

[0072] In this specification, "D 50 " indicates the volume-based 50% particle size in the cumulative particle size distribution. Specifically, in the cumulative particle size curve of the particle size distribution measured using a laser diffraction / scattering type particle size distribution measuring device, it represents the particle size when the integrated amount occupies 50% based on volume.

[0073] The glass powder of the present invention is obtained by grinding the glass produced as described above, for example, by a dry grinding method or a wet grinding method, to have the specific particle size distribution described above.

[0074] The glass grinding method for obtaining the glass powder of the present invention is preferably a method in which glass of a suitable shape is dry-ground, followed by wet-ground. Dry grinding and wet grinding can be carried out using a grinding machine such as a roll mill, ball mill, or jet mill. The particle size distribution can be adjusted by adjusting the grinding machine, such as the grinding time in each grinding step or the size of the balls in a ball mill. In the case of wet grinding, it is preferable to use water as the solvent. After wet grinding, the water is removed by drying or the like to obtain glass powder. In addition to grinding the glass, classification may be performed as needed to adjust the particle size of the glass powder.

[0075] <Conductive paste> The glass of the present invention can be applied to conductive pastes as glass powder. The conductive paste made from the glass of the present invention contains the glass powder of the present invention, conductive metal powder, and an organic vehicle.

[0076] The conductive metal powder contained in the conductive paste of the present invention is not particularly limited to metal powders commonly used for electrodes formed on circuit boards (including multilayer electronic components) such as semiconductor substrates and insulating substrates. Specifically, examples of conductive metal powders include powders of Ag, Al, Cu, Au, Pd, and Pt, and among these, Ag powder and Al powder are preferred from the viewpoint of productivity. From the viewpoint of suppressing aggregation and obtaining uniform dispersion, the particle size of the conductive metal powder is D 50 However, a particle size of 0.3 μm to 10 μm is preferred, more preferably 0.5 μm to 6 μm, and even more preferably 0.7 μm to 4 μm.

[0077] The content of conductive metal powder in the conductive paste is preferably 63.0% by mass or more and 97.9% by mass or less relative to the total mass of the conductive paste. When the content of conductive metal powder is 63.0% by mass or more, further sintering of the conductive metal powder can be suppressed, and the occurrence of glass delamination and the like can be suppressed. Furthermore, when the content of conductive metal powder is 97.9% by mass or less, it is easier to sufficiently cover the conductive metal powder with glass precipitates. In addition, the adhesion between the electrode and the circuit board such as a semiconductor substrate or an insulating substrate can be improved. The content of conductive metal powder relative to the total mass of the conductive paste is more preferably 75.0% by mass or more and 95.0% by mass or less.

[0078] The glass content in the conductive paste is preferably, for example, 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of conductive metal powder. By having a glass content of 0.1 parts by mass or more, the conductive metal powder can be sufficiently covered with glass precipitates. Furthermore, the adhesion between the electrode and the circuit board such as a semiconductor substrate or an insulating substrate can be improved. In addition, by having a glass powder content of 10 parts by mass or less, further sintering of the conductive metal powder can be suppressed, and the occurrence of glass delamination can be suppressed. The glass powder content per 100 parts by mass of conductive metal powder is more preferably 0.5 parts by mass or more and 5 parts by mass or less.

[0079] Examples of organic vehicles contained in conductive paste include organic resin binder solutions obtained by dissolving organic resin binders in a solvent.

[0080] Examples of organic resin binders used in organic vehicles include cellulosic resins such as methylcellulose, ethylcellulose, carboxymethylcellulose, oxyethylcellulose, benzylcellulose, propylcellulose, and nitrocellulose, and acrylic resins obtained by polymerizing one or more acrylic monomers such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, butyl acrylate, and 2-hydroxyethyl acrylate.

[0081] Suitable solvents for organic vehicles include, for example, terpineol, butyl diglycol acetate, ethyl diglycol acetate, and propylene glycol diacetate in the case of cellulose-based resins. Also, for example, suitable solvents for acrylic resins include methyl ethyl ketone, terpineol, butyl diglycol acetate, ethyl diglycol acetate, and propylene glycol diacetate.

[0082] The ratio of organic resin binder to solvent in the organic vehicle is not particularly limited, but is selected so that the resulting organic resin binder solution has a viscosity that can adjust the viscosity of the conductive paste. Specifically, a mass ratio of organic resin binder to solvent of approximately 3:97 to 15:85 is preferred.

[0083] The content of organic vehicle in the conductive paste is preferably 2% by mass or more and 30% by mass or less of the total amount of conductive paste. By having an organic vehicle content of 2% by mass or more, the increase in viscosity of the conductive paste is suppressed, the applicability of the conductive paste for printing and other applications is improved, and it is easier to form a good conductive layer (electrode). Furthermore, by having an organic vehicle content of 30% by mass or less, the solid content of the conductive paste is prevented from becoming too low, and a sufficient coating film thickness can be obtained.

[0084] One embodiment of the conductive paste of the present invention is a conductive paste containing 63.0 to 97.9% by mass of a metal selected from the group consisting of Ag, Al, Cu, Au, Pd, and Pt, based on the total mass of the conductive paste; 0.1 to 9.8 parts by mass of glass containing, in terms of oxide percentage, 15 to 70% PbO, 0 to 50% TeO2, 2 to 25% V2O5, 0.05 to 4% ZnO, 0.1 to 8% BaO, 0.05 to 3% Al2O3, and 0.05 to 11% B2O3, per 100 parts by mass of the above metal; and 2 to 30% by mass of an organic vehicle based on the total mass of the conductive paste. The glass in this embodiment is the glass of the second invention. Preferred embodiments of the glass, metal, and organic vehicle contained in the conductive paste of this embodiment, such as composition, type, form, and content, can be the same as described above.

[0085] In addition to the glass, conductive metal powder, and organic vehicle described above, the conductive paste of the present invention may contain known additives as needed and to the extent that they do not contradict the purpose of the present invention.

[0086] Examples of such additives include various inorganic oxides. Specifically, examples of inorganic oxides include B2O3, ZnO, SiO2, and Al2O 3、 Examples include TiO2, MgO, ZrO2, and Sb2O3, as well as composite oxides thereof. These inorganic oxides have the effect of mitigating the sintering of conductive metal powder during the firing of conductive paste, thereby adjusting the bonding strength after firing. The size of these inorganic oxide additives is not particularly limited, but for example, D 50 Materials with a size of 10 μm or less can be preferably used.

[0087] The inorganic oxide content in the conductive paste is set appropriately according to the purpose, but is preferably 10% by mass or less, more preferably 7% by mass or less, relative to the glass powder. By having an inorganic oxide content of 10% by mass or less relative to the glass powder, a decrease in the fluidity of the conductive paste during electrode formation is suppressed, and sufficient bonding strength between the electrode and the circuit board such as a semiconductor substrate or insulating substrate can be ensured. Furthermore, in order to obtain a practical formulation effect (adjustment of bonding strength after firing), the lower limit of the above content is preferably 0.5% by mass, more preferably 1.0% by mass.

[0088] The conductive paste may contain additives known to be used in conductive pastes, such as defoamers and dispersants. Note that the above-mentioned organic vehicle and these additives are typically components that disappear during the electrode formation process. For the preparation of the conductive paste, known methods using rotary mixers or grinders equipped with stirring blades, roll mills, ball mills, etc., can be applied.

[0089] The application and firing of conductive paste onto circuit boards such as semiconductor substrates and insulating substrates can be carried out using the same methods as conventional electrode formation. Application methods include screen printing and dispensing. The firing temperature depends on the type of conductive metal powder contained, the surface condition, etc., but generally, temperatures of 500 to 1000°C are typical. The firing time is adjusted appropriately according to the shape and thickness of the electrode to be formed. Furthermore, a drying process at approximately 80 to 200°C may be included between the application and firing of the conductive paste.

[0090] <Solar Cells> The solar cell according to this embodiment includes electrodes formed using the conductive paste described above, specifically electrodes baked onto a semiconductor substrate. In the solar cell according to this embodiment, it is preferable that at least one of the electrodes is provided using the conductive paste in such a manner that it partially penetrates the insulating film by fire-through and contacts the semiconductor substrate.

[0091] Examples of electrodes that penetrate such insulating films in solar cells include electrodes provided on the light-receiving surface of a solar cell using a pn-junction semiconductor substrate, which partially penetrate the insulating film (an anti-reflective film) and make contact with the semiconductor substrate. Examples of insulating materials constituting the insulating film (an anti-reflective film) include silicon nitride, titanium dioxide, silicon dioxide, and aluminum oxide, and the insulating material only needs to consist of one or more layers, but it is preferable that it consists of two layers. 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, but in order to further increase the efficiency of the solar cell, it is preferable that it be double-sided and that the semiconductor substrate be p-type. Such electrodes provided on the light-receiving surface of a solar cell can be formed by fire-through using the conductive paste described above.

[0092] An example of the configuration of a solar cell according to this embodiment will be described below, but the configuration of a solar cell according to this embodiment is not limited to this example.

[0093] The solar cell according to this example comprises a silicon substrate having a light-receiving surface (hereinafter also simply referred to as the "light-receiving surface" or "front surface"), a first insulating film provided on the light-receiving surface of the silicon substrate, a second insulating film having at least one opening provided on the surface of the silicon substrate opposite to the light-receiving surface (hereinafter also simply referred to as the "back surface"), a first electrode that penetrates a part of the first insulating film and contacts the silicon substrate, and a second electrode that partially contacts the silicon substrate through the opening of the second insulating film.

[0094] In this configuration example, the first electrode is an electrode formed by fire-through using the conductive paste according to this embodiment, and preferably includes a metal containing at least one selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt, and the glass according to this embodiment.

[0095] The first electrode preferably contains 90% to 99.9% by mass of the metal and more preferably 0.1% to 10% by mass of the glass composition according to this embodiment. Furthermore, the first electrode preferably contains at least Ag.

[0096] Furthermore, in this configuration example, it is more preferable that the first electrode and the second insulating film comprise a metal oxide film in contact with both sides of the silicon substrate, and a silicon nitride film further on the metal oxide film. The metal oxide film is more preferably made of aluminum oxide or silicon oxide. [Examples]

[0097] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Example 1~ 6. Example 8~ Examples 10, 17-26, and 30-37 are provided. Example 7 is for reference only. Examples 11-16, 27-29, and 38-40 are comparative examples.

[0098] (Examples 1-16) Glass was manufactured as thin glass sheets using the following method, and glass powder was produced from these thin glass sheets. The particle size distribution of the glass powder was measured, and the glass transition temperature of the glass was measured using the glass powder.

[0099] <Manufacturing of glass (thin sheet glass)> The raw material powders were blended and mixed to achieve the composition shown in Table 1, expressed as mass percentage based on oxides. The mixture was then melted in an electric furnace at 900-1600°C using a crucible for 30 minutes to 1 hour to form thin glass sheets with the composition shown in Table 1.

[0100] <Manufacturing of glass powder> In each example, the obtained thin glass sheets were ground using a combination of dry and wet grinding methods as described below to adjust the particle size distribution. The particle size distribution of the resulting glass powder was measured, and the glass transition temperature was also measured using the glass powder.

[0101] The glass powder was dry-ground in a ball mill for 20 hours, and coarse particles were removed using a 150-mesh sieve. Next, the glass powder obtained after dry grinding and removal of coarse particles was processed into D 50 Glass powder with the desired particle size distribution was produced by wet grinding using isopropyl alcohol (IPA) in a ball mill so that the particle size distribution was within a predetermined range. 50 Alumina balls with a diameter of 5 mm were used to obtain the material. The slurry obtained by wet grinding was then filtered and dried in a dryer at 130°C to remove IPA, thereby producing glass powder.

[0102] <Rating> For each example of glass, the glass transition temperature and the D content of the glass powder were determined using the following method. 50 The following was evaluated. The results, along with the composition, are shown in Table 1. In the column for each component of the glass composition, a blank space indicates a content of "0%".

[0103] (Glass transition temperature) The obtained glass powder was packed into an aluminum pan, and the heating rate was measured at 10°C / min using a Rigaku TG8110 differential thermal analyzer. The first inflection point of the DTA chart obtained from the measurement was defined as the glass transition temperature (indicated as "DTA Tg" in Table 1). In Table 1, "NG" indicates that vitrification did not occur and therefore the glass transition temperature could not be measured.

[0104] (D 50 ) 0.02 g of glass powder was mixed with 60 cc of isopropyl alcohol (IPA) and dispersed by ultrasonic dispersion for 1 minute. The sample was placed in a microtrac analyzer (laser diffraction / scattering particle size distribution analyzer) and D 50 The value obtained was obtained.

[0105] The results are shown in Table 1.

[0106] [Table 1]

[0107] As shown in Table 1, Examples 1-4 and 6-10, which are examples, had lower glass transition temperatures compared to Comparative Example 11, and it was found that sufficient glass fluidity was ensured during sintering. Furthermore, Examples 1-10 were compared to Comparative Examples 13-1 5 Compared to D 50 The high value indicates excellent dispersibility when used as a conductive paste.

[0108] (Examples 17-40) The glass powders of Examples 1-12 prepared above were mixed with the glass powders of Examples 13-16, which contain PbO and TeO2, in the proportions shown in Table 2 to obtain the glass powders of Examples 17-28 and 30-37. The glass powders of Examples 29 and 38-40 were prepared in the same manner as in Examples 13 and 14-16. The glass compositions are shown in Table 2.

[0109] <Manufacturing of conductive paste> Conductive pastes for forming Ag electrodes, each containing the glass powders of Examples 17-40, were prepared by the following method.

[0110] First, 5 parts by mass of ethylcellulose and 95 parts by mass of butyl diglycol acetate were mixed and stirred at 85°C for 2 hours to prepare an organic vehicle. Next, 15 parts by mass of the obtained organic vehicle were mixed with 85 parts by mass of Ag powder (DOWA Electronics Co., Ltd., spherical silver powder: AG-4-8F), and then kneaded in a grinder for 10 minutes. After that, the glass powders of Examples 1 to 11 were added in a ratio of 2 parts by mass per 100 parts by mass of the metal powder Ag powder, and further kneaded in a grinder for 90 minutes to obtain a conductive paste for forming Ag electrodes.

[0111] <Rating> (Measurement of contact resistance) Using the conductive pastes for forming Ag electrodes prepared as described above, Ag electrodes were formed on semiconductor substrates via an insulating film (a single film consisting of a silicon nitride layer) as follows, and the penetration of the insulating film (fire-through property) was evaluated.

[0112] The method for measuring contact resistance will be explained with reference to Figures 1 and 2. Figure 1 is a schematic cross-section of an example of a p-type Si substrate double-sided photodetector solar cell in which electrodes are formed using the conductive paste of the present invention. Figure 2 is a diagram showing the electrode pattern formed on the Si substrate used when evaluating the contact resistance Rc [Ω].

[0113] Using a p-type crystalline Si semiconductor substrate sliced ​​to a thickness of 160 μm, the front and back surfaces of the Si semiconductor substrate were first etched with a very small amount of hydrofluoric acid to clean the slice surface. Subsequently, a rough surface structure was formed on the light-receiving surface of the Si semiconductor substrate using a wet etching method to reduce light reflectivity.

[0114] Next, n + The layer was formed by diffusion. P (phosphorus) was used as the doping element for n-type formation. In this way, n + A p-type Si semiconductor substrate having a layer was obtained. Next, the light-receiving surface (n + An anti-reflective coating was formed on the surface of the layer. Silicon nitride was mainly used as the material for the anti-reflective coating, and it was formed to a thickness of 80 nm by plasma CVD. Next, the n of the semiconductor substrate + An insulating film was formed on the back surface (the surface of the p-type Si substrate) of the layer. The insulating film was primarily made of silicon nitride and aluminum oxide. An aluminum oxide layer was formed to a thickness of 10 nm using ALD (Atomic Layer Deposition), and then a silicon nitride layer to a thickness of 80 nm was formed on top of it using plasma CVD.

[0115] Next, the conductive paste for forming Ag electrodes, obtained using the glass powders from Examples 1 to 8, was applied in a line pattern to the light-receiving side of the obtained anti-reflective coating-coated Si semiconductor substrate by screen printing, and then dried at 120°C.

[0116] Next, the surface Ag electrode was formed by firing at a peak temperature of 750°C for 100 seconds using an infrared light heating furnace, completing a single-sided cell for contact resistance measurement. Note that the firing process caused the Ag electrode to penetrate the anti-reflective coating and penetrate the n of the Si semiconductor substrate.+ It was formed in contact with the layer.

[0117] The contact resistance of single-sided cells manufactured using conductive pastes for forming Ag electrodes containing the glass powders described in each of the above examples was measured by the TLM (Transfer Length Method). The n obtained above was + The contact resistance Rc [Ω] between a p-type Si semiconductor substrate having an Ag electrode formed via an insulating film (a single film consisting of a silicon nitride layer) on the layer side and the Ag electrode was evaluated. The contact resistance Rc [Ω] was determined by fixing the anode side of the tester to pattern P1 in Figure 2, and measuring the electrical resistance by applying the cathode side of the tester to each position of patterns P2, P3, P4, and P5. The results are shown in Tables 2 and 3.

[0118] [Table 2]

[0119] [Table 3]

[0120] As shown in Tables 2 and 3, Examples 17-26 and 30-37, which are examples, had lower contact resistance Rc and superior insulating film penetration, i.e., fire-through properties, compared to the comparative examples. From these results, it was found that by using the glass powder of the present invention, the reaction between the electrode and the semiconductor substrate can be promoted, contact resistance can be reduced, and the adhesion between the electrode and the insulating film can be improved.

[0121] As can be seen from Tables 1-3, the glass and glass powders of Examples 1-10, 17-26, and 30-37 are more suitable for forming solar cell electrodes than the glass and glass powders of the comparative examples. [Explanation of symbols]

[0122] 10...solar cell, 1...p-type Si semiconductor substrate, 1a...n +Layer, 1b…p-type layer, 2A, 2B…anti-reflection film, 3…Ag electrode, 4…Al electrode, 5…Al-Si alloy layer, 6…BSF layer, 7…opening.

Claims

1. Expressed as mass percentage in terms of oxides, V ２ O ５ 40% to 85% ZnO in a concentration of 0.1% to 20% BaO is present in a concentration of 0.1% to 30%. Al ２ O ３ and B ２ O ３ 1.0% to 60% Including, V ２ O ５ and B ２ O ３ The total content of (V ２ O ５ + B ２ O ３ ) is 60% or more and 90% or less, glass.

2. Expressed as a mass percentage on an oxide basis, it contains ZnO at 1% or more, BaO at 5% or more, and Al ２ O ３ The glass according to claim 1, comprising 1% or more of the above.

3. Expressed as mass percentage in terms of oxides, BaO, ZnO, and B ２ O ３ Total content of (BaO + ZnO + B ２ O ３ The glass according to claim 1 or 2, wherein the content of ) is 15% or more and 55% or less.

4. Expressed as mass percentage in terms of oxides, BaO and Al ２ O ３ The total content of (BaO + Al ２ O ３ The glass according to any one of claims 1 to 3, wherein the content of ) is 10% or more and 30% or less.

5. Expressed as mass percentage in terms of oxides, BaO, ZnO, and Al ２ O ３ Total content of (BaO + ZnO + Al ２ O ３ ) and V ２ O ５ and B ２ O ３ Total content (V ２ O ５ +B ２ O ３ ) ratio (BaO + ZnO + Al ２ O ３ ) / (V ２ O ５ +B ２ O ３ The glass according to any one of claims 1 to 4, wherein the coefficient of the glass is 0.1 or more and 1.0 or less.

6. A glass according to any one of claims 1 to 5, wherein the glass transition temperature is 250°C or higher and 500°C or lower.

7. A glass powder comprising the glass described in any one of claims 1 to 6, wherein the 50% particle size by volume in the cumulative particle size distribution is D ５０ When that happens, D ５０ Glass powder having a particle size of 0.8 μm or more and 6.0 μm or less.

8. A first glass powder comprising the glass described in claim 1, and having a glass transition temperature of 250°C or more and 500°C or less, PbO and TeO ２ A glass powder composition obtained by mixing a second glass powder containing and Expressed as mass percentage in terms of oxides, PbO is between 15% and 70%. TeO ２ between 0% and 50%, V ２ O ５ between 2% and 25%, ZnO in a concentration of 1% to 4% BaO is present in a concentration of 0.1% to 8%. Al ２ O ３ and B ２ O ３ to 0.05% or more and 11% or less, A glass powder composition.

9. V ２ O ５ and B ２ O ３ Total content (V ２ O ５ +B ２ O ３ The glass powder composition according to claim 8, wherein the amount of ) is 2.05% or more and 22% or less.

10. Expressed as mass percentage in terms of oxides, BaO, ZnO, and B ２ O ３ Total content of (B ２ O ３ The glass powder composition according to claim 8 or 9, wherein the amount of (BaO + ZnO) is 1% or more and 14% or less.

11. Expressed as mass percentage in terms of oxides, BaO and Al ２ O ３ The total content of (BaO + Al ２ O ３ A glass powder composition according to any one of claims 8 to 10, wherein the amount of ) is 0.5% or more and 8% or less.

12. Expressed as mass percentage in terms of oxides, PbO and TeO ２ and V ２ O ５ Total content (PbO + TeO ２ +V ２ O ５ A glass powder composition according to any one of claims 8 to 11, wherein ) is 50% or more and 80% or less.

13. In terms of mass% representation in terms of oxides, BaO, ZnO, and Al ２ O ３ The total content of (BaO + ZnO + Al ２ O ３ ) and V ２ O ５ and B ２ O ３ The total content of (V ２ O ５ + B ２ O ３ ) and the ratio (BaO + ZnO + Al ２ O ３ ) / (V ２ O ５ + B ２ O ３ ) is 0.1 or more and 1.0 or less. The glass powder composition according to any one of claims 8 to 12.

14. V ２ O ５ The ratio of PbO (V ２ O ５ A glass powder composition according to any one of claims 8 to 13, wherein the PbO content is 0.05 or more and 1.0 or less.

15. A glass powder composed of the glass powder composition according to any one of claims 8 to 14, wherein the 50% particle size based on volume in the cumulative particle size distribution is D ５０ When it is set as ５０ the glass powder in which D is 0.8 μm or more and 6.0 μm or less.

16. A glass powder made from glass or a glass powder composition according to any one of claims 1 to 6 and 8 to 14, or a conductive paste containing the glass powder, conductive metal powder, and organic vehicle according to claim 7 or 15.

17. A solar cell comprising electrodes formed using the conductive paste described in claim 16.

18. 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 is provided on the side of the silicon substrate opposite to the sunlight-receiving surface, A first electrode that penetrates a portion of the first insulating film and contacts the silicon substrate, A second electrode that partially contacts the silicon substrate through the opening of the second insulating film, A solar cell equipped with, The first electrode comprises a metal including at least one selected from the group consisting of Al, Ag, Cu, Au, Pd, and Pt, A glass according to any one of claims 1 to 6, and a composition of 15% to 70% PbO and TeO in terms of mass percentage on an oxide basis. ２ 0% to 50%, V ２ O ５ 2% to 25% of ZnO, 0.1% to 8% of BaO, Al ２ O ３ 0.05% to 3% and B ２ O ３ A solar cell containing glass containing 0.05% to 11% of [the substance].

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