TWI693723B - Solar cell element - Google Patents

Abstract

The solar cell element includes a semiconductor substrate, a passivation layer, a protective layer, and an electrode layer. The passivation layer is located on the first surface of the semiconductor substrate. The protective layer is located above the passivation layer. The electrode layer is located above the protective layer and contains glass components. The protective layer has a plurality of convex portions on the surface on the electrode layer side. The plurality of convex portions each have a concave portion on the electrode layer side. The glass component is located in the internal space of the concave portion.

Description

Solar cell element

The invention relates to a solar cell element.

Solar cell elements include PERC (Passivated Emitter and Rear Cell) type solar cell elements (for example, refer to the description of Japanese Patent Laid-Open No. 2013-4944). In the solar cell element, the passivation layer is located on the back of the semiconductor substrate. Furthermore, the collector electrode on the back side is located on the passivation layer or on the protective layer on the passivation layer.

The invention discloses a solar cell element.

One aspect of the solar cell element includes a semiconductor substrate, a passivation layer, a protective layer, and an electrode layer. The passivation layer is located on the first surface of the semiconductor substrate. The protective layer is located on the passivation layer. The electrode layer is located on the protective layer and contains a glass component. The protective layer has a plurality of convex portions on the surface on the electrode layer side. The plurality of convex portions each have a concave portion on the electrode layer side. The glass component is located in the internal space of the concave portion.

When manufacturing a PERC type solar cell element, for example, a passivation layer, a protective layer, and a back electrode are sequentially formed on the back surface of a semiconductor substrate as described. The protective layer is composed of, for example, an oxide film containing silicon oxide or the like, a nitride film containing silicon nitride or the like, or a film formed by laminating an oxide film and a nitride film. The protective layer is formed by, for example, a wet process or a dry process. For the wet process, for example, a coating method such as coating and drying of an insulating paste containing a silicone resin is applied. The dry process uses, for example, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD (plasma-assisted chemical vapor deposition)), or sputtering.

However, in order to improve the photoelectric conversion efficiency in the solar cell element, for example, there is a case where a fine uneven structure (organization structure) is formed on the front surface side of the semiconductor substrate to reduce the reflection of the irradiated light. In this case, the semiconductor substrate is subjected to wet etching using, for example, an alkaline aqueous solution such as sodium hydroxide or an acidic aqueous solution such as nitrofluoric acid to form a structure. In this case, not only the front surface of the semiconductor substrate but also all surfaces including the back surface can form a structure.

In this way, if irregularities such as a structure structure exist on the back surface of the semiconductor substrate, irregularities are likely to occur on the surfaces of the passivation layer and the protective layer formed on the back surface of the semiconductor substrate. Here, for example, there is a case where by applying a paste (also called a metal paste) containing metal powder mainly containing aluminum, a glass component, and an organic medium on the protective layer, and baking the metal paste, and The collector electrode on the back side is formed. In this case, due to the existence of irregularities in the surface of the protective layer, the distribution of the components of the metal paste is likely to be deviated. Therefore, the adhesion strength of the collector electrode to the protective layer tends to become uneven. Thereby, there is a concern that the collector electrode may partially peel off on the protective layer. Specifically, for example, a glass component having fluidity and an organic medium easily flow from the convex portion of the protective layer to the lower portion of the protective layer, such as through the metal powder, on the concave portion of the protective layer in the direction of gravity . Therefore, there is a concern that the current collector electrode may partially peel off on the convex portion of the protective layer. Furthermore, if the collector electrode is peeled off from the protective layer, the collector electrode is peeled off on the back side of the solar cell element, and there is a concern that the current collection efficiency on the back side of the solar cell element may decrease. As a result, there is a concern that the photoelectric conversion efficiency in the solar cell element will decrease.

Therefore, in order to reduce the partial peeling of the collector electrode on the protective layer, for example, it may be considered to increase the content rate of the glass component in the metal paste. However, if the content of the glass component in the metal paste increases, the firing of the protective layer caused by the metal paste (baking through) is likely to occur during the firing of the metal paste. Therefore, there is a concern that the photoelectric conversion efficiency in the solar cell element may decrease due to the reduction in the passivation effect on the back side of the solar cell element.

In addition, regarding the above-mentioned aspects, for example, in order to prevent the burning-through of the protective layer caused by the metal paste from occurring, it may be considered to increase the thickness of the protective layer. However, if the thickness of the protective layer becomes larger, the stress between the semiconductor substrate and the protective layer during expansion of the metal paste and the use of the solar cell element due to expansion and contraction due to temperature changes tends to increase. As a result, there is a concern that the protective layer may peel off from the back side of the semiconductor substrate. Also, for example, if the stress generated between the semiconductor substrate and the protective layer due to the expansion and contraction of the protective layer accompanying temperature changes becomes larger, there is an increase in the warpage of the solar cell element, and cracks occur in the solar cell element Or rupture fears. As a result, there is a concern that the photoelectric conversion efficiency in the solar cell element will decrease.

Therefore, the inventors of the present invention have created a technology that can improve the photoelectric conversion efficiency for the PERC type solar cell element.

In this regard, various embodiments will be described below based on the drawings. In the drawings, parts having the same configuration and function are marked with the same symbols, and repeated description is omitted in the following description. Schema is a model representative. In Fig. 1 to Fig. 6(a), Fig. 7, Fig. 9 to Fig. 17(c), the right-handed XYZ coordinate system is marked. In the XYZ coordinate system, the long-side direction of the first output extraction electrode 7a is set to +Y direction, and the short-side direction of the first output extraction electrode 7a is set to +X direction, and the +X direction and +Y direction The normal direction of the front surface 10fs in the solar cell element 10 in which the two are orthogonal is set to the +Z direction.

<1. First Embodiment> <1-1. Schematic configuration of solar cell element> The schematic configuration of the solar cell element 10 of the first embodiment will be described based on FIGS. 1 to 3. In FIG. 3, for the sake of convenience, the organization structure intentionally formed on the second surface 1fs of the semiconductor substrate 1 is depicted in a larger size. On the other hand, in FIG. 3, the structure formed on the first surface 1bs of the semiconductor substrate 1 is omitted to conform to the actual size. The solar cell element 10 of the first embodiment is a PERC type solar cell element.

As shown in FIGS. 1 to 3, the solar cell element 10 mainly includes a light-receiving surface (also referred to as a front surface) 10fs, and a surface (also referred to as a back surface) 10bs located on the opposite side of the front surface. In the examples of FIGS. 1 to 3, the front surface 10fs faces the +Z direction, and the back surface 10bs faces the -Z direction.

The solar cell element 10 includes, for example, a semiconductor substrate 1, a passivation layer 4, an anti-reflection layer 5, a protective layer 6, a front electrode 7, and a back electrode 8.

The semiconductor substrate 1 has a first surface 1bs, a second surface 1fs, and a third surface 1ss. The first surface 1bs is located on the back surface 10bs side. The second surface 1fs is located on the front surface 10fs side. In other words, the first surface 1bs and the second surface 1fs are arranged in mutually opposite directions. The third surface 1ss is positioned in a state where the first surface 1bs and the second surface 1fs are connected. In other words, the third surface 1ss is an end surface in a state that constitutes the outer periphery of the semiconductor substrate 1. In the examples of FIGS. 1 to 3, the first surface 1bs is oriented in the -Z direction. The second surface 1fs is facing the +Z direction. The semiconductor substrate 1 has a flat plate shape having a thickness along the +Z direction. Therefore, the first surface 1bs and the second surface 1fs are respectively in a state of constituting the plate surface of the semiconductor substrate 1 along the XY plane.

In addition, the semiconductor substrate 1 has a first semiconductor layer 2 and a second semiconductor layer 3. The first semiconductor layer 2 is made of a semiconductor having the first conductivity type. The second semiconductor layer 3 is formed of a semiconductor having a second conductivity type opposite to the first conductivity type. The first semiconductor layer 2 is located on the portion of the semiconductor substrate 1 on the side of the first surface 1bs. The second semiconductor layer 3 is located on the surface layer portion on the second surface 1fs side of the semiconductor substrate 1. In the example of FIG. 3, the second semiconductor layer 3 is located on the first semiconductor layer 2.

Here, for example, assume that the semiconductor substrate 1 is a silicon substrate. In this case, a polycrystalline or single-crystalline silicon substrate is used as the silicon substrate. The silicon substrate is, for example, a thin substrate having a thickness of 250 μm or less or 150 μm or less. In addition, the silicon substrate has a rectangular outer edge shape in a plan view, for example. If the semiconductor substrate 1 having such a shape is used, when a plurality of solar cell elements 10 are arranged to manufacture a solar cell module, the gap between the solar cell elements 10 can be reduced.

Also, for example, in the case where the first conductivity type is p-type and the second conductivity type is n-type, the p-type silicon substrate may contain impurities such as boron or calcium as dopants in the crystal of polycrystalline or single-crystal silicon, for example Elements. In this case, by diffusing impurities such as phosphorus as a dopant into the surface layer portion on the second surface 1fs side of the p-type silicon substrate, the n-type second semiconductor layer 3 can be generated. At this time, the semiconductor substrate 1 in which the p-type first semiconductor layer 2 and the n-type second semiconductor layer 3 are stacked can be formed. Accordingly, the semiconductor substrate 1 has a pn junction portion located at the interface between the first semiconductor layer 2 and the second semiconductor layer 3.

As shown in FIG. 3, the second surface 1fs of the semiconductor substrate 1 may also have a fine uneven structure (organization structure) for reducing the reflection of the irradiated light, for example. At this time, the height of the convex portion of the organizational structure is set to about 0.1 μm to 10 μm, for example. The distance between the vertices of adjacent convex portions is set to about 0.1 μm to 20 μm, for example. In the structure, for example, the concave portion may be substantially spherical, and the convex portion may be pyramidal. The "height of the convex portion" mentioned above is, for example, in FIG. 3, a straight line passing through the bottom surface of the concave portion is used as a reference line, and in a direction perpendicular to the reference line (here +Z direction), from the reference line to the convex The distance to the apex.

Furthermore, the semiconductor substrate 1 has a third semiconductor layer 2bs. The third semiconductor layer 2bs is located on the surface layer portion on the first surface 1bs side of the semiconductor substrate 1. The conductivity type of the third semiconductor layer 2bs is set to be the same as the conductivity type of the first semiconductor layer 2 (p-type in this embodiment). Furthermore, the concentration of the dopant contained in the third semiconductor layer 2bs is higher than the concentration of the dopant contained in the first semiconductor layer 2. The third semiconductor layer 2bs forms an internal electric field on the first surface 1bs side of the semiconductor substrate 1. As a result, in the vicinity of the first surface 1bs of the semiconductor substrate 1, the recombination of minority carriers generated by the photoelectric conversion corresponding to the irradiation of light in the semiconductor substrate 1 can be reduced. As a result, the decrease in the photoelectric conversion efficiency in the solar cell element 10 is unlikely to occur. The third semiconductor layer 2bs can be formed, for example, by diffusing dopant elements such as aluminum to the surface layer portion on the first surface 1bs side of the semiconductor substrate 1. At this time, the concentration of the dopant element contained in the first semiconductor layer 2 may be set to about 5×10 ¹⁵ atoms/cm ³ to 1×10 ¹⁷ atoms/cm ³ , and the doping contained in the third semiconductor layer 2bs The concentration of the impurity element is set to about 1×10 ¹⁸ atoms/cm ³ to 5×10 ²¹ atoms/cm ³ . The third semiconductor layer 2bs exists in the contact portion of the second current collector electrode 8b and the semiconductor substrate 1 described below.

The passivation layer 4 is located on at least the first surface 1bs of the semiconductor substrate 1. The passivation layer 4 can reduce the recombination of minority carriers generated by the photoelectric conversion corresponding to the irradiation of light in the semiconductor substrate 1. As the material of the passivation layer 4, for example, one or more materials selected from alumina, zirconia, hafnium oxide, silicon oxide, silicon nitride, and silicon oxynitride are used. The passivation layer 4 is, for example, a state composed of one layer or two or more layers including mutually different materials. In this case, the passivation layer 4 can be formed by, for example, the CVD method or the atomic layer deposition (Atomic Layer Deposition: ALD) method. Here, it is assumed that the passivation layer 4 contains aluminum oxide. In this case, the alumina has a fixed negative charge. Therefore, due to the field effect, the minority carriers (electrons in this case) generated on the first surface 1bs side of the semiconductor substrate 1 are far from the interface between the p-type first semiconductor layer 2 and the passivation layer 4 (first surface 1bs ). This can reduce the recombination of minority carriers in the vicinity of the first surface 1bs in the semiconductor substrate 1. Therefore, the photoelectric conversion efficiency of the solar cell element 10 can be improved. The thickness of the passivation layer 4 is set to about 3 nm to 100 nm, for example. The passivation layer 4 may be located on the second surface 1fs of the semiconductor substrate 1, for example. In addition, the passivation layer 4 may be located on the third surface 1ss which is an end surface connecting the second surface 1fs of the semiconductor substrate 1 and the first surface 1bs, for example.

The anti-reflection layer 5 can reduce the reflectance of light irradiated to the front surface 10fs of the solar cell element 10. As the material of the anti-reflection layer 5, for example, silicon oxide, aluminum oxide, silicon nitride, or the like is used. The refractive index and thickness of the anti-reflection layer 5 can be appropriately set to achieve the conditions of low reflectance (also referred to as low-reflection conditions) for light in the wavelength range that is absorbed by the semiconductor substrate 1 in sunlight and can contribute to power generation ) Value. For example, it may be considered that the refractive index of the anti-reflection layer 5 is set to about 1.8 to 2.5, and the thickness of the anti-reflection layer 5 is set to about 20 nm to 120 nm.

The protective layer 6 is located on the passivation layer 4 on the first surface 1bs of the semiconductor substrate 1. The protective layer 6 can protect the passivation layer 4. As the material of the protective layer 6, for example, one or more materials selected from silicon oxide, silicon nitride, silicon oxynitride, and the like are used. The protective layer 6 is located on the passivation layer 4 in a state with a desired pattern. The protective layer 6 has a gap penetrating the protective layer 6 in the thickness direction (here, +Z direction). The gap may be, for example, a hole portion formed with a through hole closed along the first surface 1bs, or may be slit-shaped in a state where at least a part of the first surface 1bs is opened. The hole part. For example, as shown in FIG. 2, it is assumed that the protective layer 6 has a plurality of holes CH1 when the protective layer 6 is seen through from the back 10 bs side. Here, when the protective layer 6 is seen through from the back surface 10bs side, each hole CH1 may be in the form of a dot (dot) or a strip (line). The diameter or width of the hole portion CH1 is set to about 10 μm to 500 μm, for example. The distance between the hole portions CH1 is set to about 0.3 mm to 3 mm, for example. The distance between the holes CH1 is set to, for example, the distance between the centers of the adjacent holes CH1 when the protective layer 6 is seen through from the back 10bs side. In the example of FIG. 2, there are 110 holes CH1. However, the combination of the size, shape, and number of each hole CH1 can be adjusted as appropriate. Therefore, the number of hole portions CH1 may be, for example, one or more.

However, the protective layer 6 has a desired pattern by a spraying method, a coating method, a screen printing method, or the like on the passivation layer 4 formed on the first surface 1bs of the semiconductor substrate 1, for example It is formed by applying an insulating paste and then drying it. The protective layer 6 may be formed directly on the passivation layer 4 or on the anti-reflection layer 5, for example, on the third surface 1ss of the semiconductor substrate 1. At this time, the presence of the protective layer 6 can reduce the leakage current in the solar cell element 10.

Here, for example, when the following second collector electrode 8b is formed on the protective layer 6, a metal paste (also referred to as a first metal) containing a metal powder containing aluminum as a main component, a glass component, and an organic medium Paste) is applied on the protective layer 6 in a desired shape and fired. The main component means the component having the largest (high) ratio (also called content ratio) contained in the contained component. At this time, the first metal paste directly coated on the passivation layer 4 causes the passivation layer 4 to burn through (fire through) in the hole CH1 of the protective layer 6, and the second collector electrode 8b is directly connected to the semiconductor substrate 1 1bs on the first side. As a result, the passivation layer 4 and the protective layer 6 are in a state with a plurality of holes CH1, and the plurality of holes CH1 are positioned in a state of penetrating the passivation layer 4 and the protective layer 6, respectively. In this case, for example, the third semiconductor layer 2bs is formed by diffusing aluminum contained in the first metal paste located in the plurality of hole portions CH1 into the surface layer portion of the first surface 1bs of the semiconductor substrate 1. Also, for example, if the thickness of the protective layer 6 is sufficiently larger than the thickness of the passivation layer 4, the portion of the passivation layer 4 that is covered by the protective layer 6 will not cause the first metal paste to passivate the layer 4. Burn through. As a result, in the solar cell element 10, the passivation layer 4 can be present on the first surface 1bs of the semiconductor substrate 1 in a pattern corresponding to the desired pattern of the protective layer 6.

The thickness of the protective layer 6 is set to about 0.5 μm to 10 μm, for example. The thickness of the protective layer 6 is appropriately set according to the composition of the following insulating paste for forming the protective layer 6, the shape of the first surface 1bs of the semiconductor substrate 1, and the firing conditions at the time of forming the second collector electrode 8b, etc. .

The front electrode 7 is located on the second surface 1fs side of the semiconductor substrate 1. As shown in FIGS. 1 and 3, the front electrode 7 has a first output extraction electrode 7a and a plurality of linear first collector electrodes 7b.

The first output extraction electrode 7a can extract the carrier obtained by the photoelectric conversion corresponding to the irradiation of light in the semiconductor substrate 1 to the outside of the solar cell element 10. As the first output extraction electrode 7a, a bus bar electrode having, for example, an elongated rectangular shape when viewed from the front surface 10fs is used. The length (also referred to as the width) of the first output extraction electrode 7a in the short-side direction is set to about 0.3 mm to 2.5 mm, for example. At least a part of the first output extraction electrode 7a is in a state of being electrically connected to the first collector electrode 7b in a crossing state.

The first collector electrode 7b can collect carriers in the semiconductor substrate 1 obtained by photoelectric conversion corresponding to the irradiation of light. Each first collector electrode 7b is, for example, a linear electrode having a width of approximately 20 μm to 200 μm. In other words, the width of each first collector electrode 7b is smaller than the width of the first output extraction electrode 7a. The plurality of first collector electrodes 7b are positioned in a state where they are arranged at intervals of about 1 mm to 3 mm, for example. The thickness of the front electrode 7 is set to about 3 μm to 30 μm, for example. Such a front electrode 7 can be applied to a desired shape by applying a metal paste (also referred to as a second metal paste) containing metal particles containing silver as a main component by screen printing or the like, and then applying the second The metal paste is formed by firing. In addition, for example, by positioning the auxiliary electrode 7c having the same shape as the first collector electrode 7b along the edges present on the side of the +X direction and the side of the -X direction of the semiconductor substrate 1, respectively, The first collector electrodes 7b are electrically connected to each other.

The back electrode 8 is located on the first surface 1bs side of the semiconductor substrate 1. As shown in FIGS. 2 and 3, the back electrode 8 has a second output extraction electrode 8 a and a second collector electrode 8 b.

The second output extraction electrode 8a is located on the first surface 1bs side of the semiconductor substrate 1. The second output extraction electrode 8a is an electrode for extracting carriers obtained by photoelectric conversion in the solar cell element 10 to the outside of the solar cell element 10. The thickness of the second output extraction electrode 8a is set to about 3 μm to 20 μm, for example. The width of the second output extraction electrode 8a is set to about 1.3 mm to 7 mm, for example. In the case where the second output extraction electrode 8a contains silver as the main component, the second output extraction electrode 8a can, for example, use screen printing or the like to convert the metal containing silver as the main component to the metal powder, glass component, and organic medium. After the paste (also referred to as the third metal paste) is applied to a desired shape, the third metal paste is fired to form.

The second collector electrode 8b is located on the protective layer 6 on the first surface 1bs side of the semiconductor substrate 1. The second collector electrode 8b is in a state of being electrically connected to the semiconductor substrate 1. Specifically, the second collector electrode 8b has an electrode layer 8bl and a connection portion 8bc. The electrode layer 8bl is a layered portion above the protective layer 6. The connection portion 8bc is located in a portion of the plurality of hole portions CH1 respectively positioned in a state of penetrating the passivation layer 4 and the protective layer 6 while electrically connecting the electrode layer 8bl and the first surface 1bs of the semiconductor substrate 1 respectively.

The second collector electrode 8b can collect carriers obtained by photoelectric conversion corresponding to the irradiation of light in the semiconductor substrate 1 on the first surface 1bs side of the semiconductor substrate 1. The second collector electrode 8b is positioned to be electrically connected to at least a part of the second output extraction electrode 8a. The thickness of the electrode layer 8bl in the second collector electrode 8b is, for example, about 15 μm to 50 μm. When the second collector electrode 8b contains aluminum as a main component, the second collector electrode 8b can be formed, for example, by coating the first metal paste into a desired shape and then baking the first metal paste .

Furthermore, for example, the second collector electrode 8b may have the same shape as the first collector electrode 7b on the first surface 1bs of the solar cell element 10 and be positioned in a state of being connected to the second output extraction electrode 8a. With this structure, light incident on the back surface 10bs of the solar cell element 10 can also be used for photoelectric conversion in the solar cell element 10. With this, for example, the output in the solar cell element 10 can be increased. The light incident on the back surface 10bs can be generated by reflection of sunlight on the ground or the like, for example.

<1-2. Structure on the back side of the solar cell element> The structure on the back side 10bs side of the solar cell element 10 of the first embodiment will be described based on FIGS. 4(a) and 4(b). Here, for example, after removing the back electrode 8 of the solar cell element 10 by etching using hydrochloric acid or the like, the surface shape of the protective layer 6 can be observed with an optical microscope or a scanning electron microscope (SEM: Scanning Electron Microscope). Also, for example, the solar cell element 10 may be cut, and by etching using hydrochloric acid or the like, the portion of the cut surface of the solar cell element 10 that has deformation and scratches due to the cutting is removed, and then SEM or the like Observe the cross section of the protective layer 6.

As shown in FIG. 4(a), for example, the protective layer 6 has a plurality of convex portions 6p located on the surface of the second collector electrode 8b on the electrode layer 8bl side. In other words, for example, the surface of the plurality of convex portions 6p located on the side of the protective layer 6 opposite to the passivation layer 4 is the surface on the opposite side. Here, the surface of the protective layer 6 on the side opposite to the passivation layer 4 is the surface on the side of the protective layer 6 where the electrode layer 8b1 is located. In the first embodiment, the protective layer 6 has a plurality of convex portions 6p and non-convex portions 6ap located on the electrode layer 8bl side of the second collector electrode 8b. The non-convex portion 6ap is a portion of the surface of the protective layer 6 on the side of the electrode layer 8bl except for the plurality of convex portions 6p. In other words, the surface of the protective layer 6 on the electrode layer 8bl side has a concave-convex structure including convex portions 6p and non-convex portions 6ap. In the example of FIG. 4(a), each convex portion 6p is positioned with the non-convex portion 6ap as a reference to protrude in the -Z direction.

Also, for example, in the aspect as shown in FIG. 5(a), the protective layer 6 may have a convex portion 6p located on the surface of the second collector electrode 8b on the electrode layer 8bl side, and the convex shape The non-convex portion 6ap other than the portion 6p. In other words, for example, the convex portion 6p and the non-convex portion 6ap are located on the opposite side of the surface of the protective layer 6 on the side where the passivation layer 4 is located. In the example of FIG. 5(a), each convex portion 6p is positioned with the non-convex portion 6ap as a reference to protrude in the -Z direction.

The uneven structure on the surface of the protective layer 6 may be derived from the uneven structure 1rg of the first surface 1bs of the semiconductor substrate 1, for example. In the examples of FIGS. 4(a) and 5(a), the first surface 1bs of the semiconductor substrate 1 has a portion (also referred to as a concave portion) 1r positioned in a state of being recessed in the +Z direction, and -Z A portion (also called a convex portion) 1p positioned in a state where the direction protrudes. The concavo-convex structure 1rg is in a state in which it has the concave portions 1r and the convex portions 1p. Therefore, for example, by forming the passivation layer 4 and the protective layer 6 with a small thickness sequentially on the concave-convex structure 1rg according to the description, the semiconductor layer can be formed on the surface of the protective layer 6 to be the object of forming the electrode layer 8bl The uneven structure corresponding to the uneven structure 1rg of the substrate 1.

In the first embodiment, in the semiconductor substrate 1, as described above, the above-mentioned fine particles are formed on the 1fs side of the second surface by wet etching using an alkaline aqueous solution such as sodium hydroxide or an acidic aqueous solution such as nitrofluoric acid. Concavo-convex structure (organizational structure). For example, when the uneven structure is formed on the second surface 1fs side, the uneven structure 1rg may also be formed on the first surface 1bs side of the semiconductor substrate 1.

As shown in FIGS. 4(b) and 5(b), each of the plurality of convex portions 6p in the protective layer 6 has one or more concaves on the electrode layer 8bl side of the second collector electrode 8b 6pr. Thereby, the convex portion 6p has a plurality of concave portions 6pr. In FIG. 4(b), six concave portions 6pr located on the convex portion 6p are depicted. In FIG. 5(b), seven concave portions 6pr located on the convex portion 6p are depicted. Such a concave portion 6pr can include, for example, a region where the organic filler is used when forming the protective layer 6 and the organic filler is thermally decomposed when the insulating paste is dried, and the organic filler disappears Formed by the traces.

A part of the electrode layer 8bl of the second collector electrode 8b is located in the internal space SC1 of the concave portion 6pr. In other words, the component (also referred to as an electrode component) in the state of constituting the electrode layer 8bl of the second collector electrode 8b is located in the internal space SC1 of the concave portion 6pr. The electrode component contains at least a glass component. This glass component can be derived from the glass component contained in the first metal paste used when forming the second collector electrode 8b, for example.

Furthermore, for example, if it is assumed that the content of the glass component contained in the first metal paste to be coated on the protective layer 6 when forming the second collector electrode 8b is reduced, the difference between the protective layer 6 and the second collector electrode 8b The adhesion is reduced. For example, as described below, four types of experimental solar cell elements 110 (see FIGS. 6(a) and 6(b)) were prepared as samples, and experiments were conducted on the adhesion of the second collector electrode 108b to the protective layer 106 . As a result, it was confirmed that as the content of the glass component contained in the first metal paste decreases, the adhesion of the second collector electrode 108b to the protective layer 106 decreases.

When fabricating four types of experimental solar cell elements 110, first, a polycrystalline silicon substrate having a rectangular front and back sides of about 156 mm and a thickness of about 200 μm is prepared. On the back side of the polysilicon substrate, a passivation layer of about 50 nm is formed by the ALD method, and a protective layer 106 is formed on the passivation layer. At this time, on the passivation layer, an insulating paste containing a silicone resin, an organic solvent, and a plurality of inorganic fillers is applied by a coating method, and dried at about 270°C to form a layer with a thickness of about 1 μm The thickness of the protective layer 106. Next, a first metal paste containing a metal powder containing aluminum (Al) as a main component, a glass component, and an organic medium is applied to substantially the entire surface on the protective layer 106 by screen printing. Here, four types of first metal pastes of 4 grades with a content ratio of glass components of 2% by mass, 3.5% by mass, 4% by mass, and 5% by mass are used. Furthermore, a third metal paste containing a metal powder containing silver as a main component, an organic medium, and a glass frit is applied by a screen printing method to become a pattern of the second output extraction electrode 108a. Then, by firing the first metal paste and the third metal paste under the condition that the maximum temperature is about 740° C. and the heating time is set to about 1 minute (min), the second output extraction electrode 108 a and the second output extraction electrode 108 a are formed. The back electrode 108 of the second collector electrode 108b. By this, four kinds of samples of the experimental solar cell element 110 were produced.

Then, as shown in FIG. 6(a), for each of the four samples of the experimental solar cell element 110, while heating, the resin of ethylene-vinyl acetate copolymer (EVA) was attached to episode 2 The area Aa0 on the electric electrode 108b surrounded by the two-dot chain line. Then, an experiment was conducted to confirm whether the second collector electrode 108b was peeled from the protective layer 106 by peeling the EVA resin from the second collector electrode 108b. At this time, as shown in FIG. 6(b), the content rate of the glass component in the first metal paste used in the preparation of the samples of the four types of experimental solar cell elements 110 is 4% by mass and 5% by mass In the sample, it was confirmed that the second collector electrode 108b was not peeled off from the protective layer 106. On the other hand, it was confirmed that if the content rate of the glass component in the first metal paste used in the production is 3.5% by mass and 2% by mass, the second collector electrode 108b will peel off from the protective layer 106. From this experiment result, it was confirmed that if the content of the glass component contained in the first metal paste decreases, the adhesion of the second collector electrode 108b to the protective layer 106 decreases. From this, it can be seen that if the content of the glass component in the first metal paste becomes higher, the adhesion between the protective layer 106 and the metal particles in the second collector electrode 108b becomes higher due to the presence of the glass component.

On the other hand, in the solar cell element 10 of the first embodiment, the convex portion 6p existing on the surface of the protective layer 6 has the concave portion 6pr. Therefore, for example, when the first metal paste is applied on the protective layer 6 to form the second collector electrode 8b, even if there is an uneven structure on the surface of the protective layer 6, the glass component in the first metal paste will enter into the presence The concave portion 6pr of the convex portion 6p. Therefore, for example, when forming the structure shown in FIGS. 4(a) and 5(a), the first metal paste located on the convex portion 6p contains a fluid component such as a glass component and an organic medium It becomes difficult to flow out in the direction along the direction of gravity (+Z direction in the example of FIGS. 4(a) and 5(a)). Accordingly, in the first metal paste located on the convex portion 6p, the content of the glass component is not easily reduced. As a result, when the second collector electrode 8b is formed, the distribution of the components of the first metal paste applied on the protective layer 6 is unlikely to vary. At this time, for example, the adhesion of the second collector electrode 8b on the protective layer 6 is unlikely to vary. Then, when the first metal paste is fired, by the presence of the glass component in the concave portion 6pr, the adhesion between the protective layer 6 in the convex portion 6p and the metal particles in the second collector electrode 8b can be improved . Also, for example, a part of the second collector electrode 8b enters the concave portion 6pr of the protective layer 6, so that the so-called anchor effect can be generated. Thereby, the adhesion of the second collector electrode 8b to the protective layer 6 can be improved. As a result, for example, peeling of the second collector electrode 8b from the protective layer 6 is less likely to occur. Therefore, the photoelectric conversion efficiency in the PERC type solar cell element 10 can be improved.

Here, for example, when the protective layer 6 is seen through from the electrode layer 8bl side of the second collector electrode 8b, the diameter of the concave portion 6pr existing on the surface of the protective layer 6 is set to, for example, 0.1 μm to 10 μm about. In this case, for example, the glass component in the molten state in the first metal paste during the firing of the first metal paste can easily enter the concave portion 6pr. As a result, the adhesion of the second collector electrode 8b to the protective layer 6 can be improved.

Here, for example, the depth of the concave portion 6pr existing on the surface of the second collector electrode 8b on the electrode layer 8bl side of the protective layer 6 is, for example, about 0.1 μm to 1 μm. Here, for example, if the depth of the concave portion 6pr is smaller than the height of the convex portion 6p, when the second collector electrode 8b is formed, the distribution of the components of the first metal paste applied on the protective layer 6 is not likely to vary . As a result, for example, the adhesion of the second collector electrode 8b on the protective layer 6 is unlikely to vary. Also, here, for example, if the thickness (also referred to as the minimum film thickness) of the protective layer 6 at the portion where the concave portion 6pr exists in the protective layer 6 is about 0.5 μm or more, the passivation layer can be secured by the protective layer 6 4 features.

However, here, as shown in FIG. 4(b) and FIG. 5(b), for example, the distance between adjacent concave portions 6pr among the plurality of concave portions 6pr existing in the convex portion 6p (also This is referred to as the first distance). As the first distance D1, for example, the distance between the centers of the adjacent concave portions 6pr is used. The first distance D1 may be, for example, the average distance between the centers of adjacent concave portions 6pr, or the distance between adjacent concave portions 6pr (also referred to as the separation distance), or The average distance between adjacent concave parts 6pr. As shown in FIGS. 4(a) and 5(a), for example, the distance (also referred to as the second distance) between adjacent convex portions 6p among the plurality of convex portions 6p is D2. As the second distance D2, for example, the distance between the centers or tops of adjacent convex portions 6p is used. The second distance D2 may be, for example, the average value of the distance between the centers or tops of adjacent convex portions 6p, or may be the distance between adjacent convex portions 6p, or may be adjacent convexities The average value of the distance between the 6p portions. Further, as shown in FIGS. 2 and 3, for example, the distance (also referred to as a third distance) between adjacent connection portions 8bc among the plurality of connection portions 8bc existing in the plurality of hole portions CH1 is D3. As the third distance D3, for example, the distance between the centers of adjacent connecting portions 8bc is used. The third distance D3 may be, for example, the average distance between the centers of the adjacent connecting portions 8bc, the distance between the adjacent connecting portions 8bc, or the distance between the adjacent connecting portions 8bc Of the average. In this case, for example, if the first distance D1 is shorter than the second distance D2 and the third distance D3, the adhesion of the second collector electrode 8b to the protective layer 6 can be sufficiently improved. As a result, for example, peeling of the second collector electrode 8b from the protective layer 6 is less likely to occur. Therefore, the photoelectric conversion efficiency in the PERC type solar cell element 10 can be improved. Furthermore, here, for example, adjacent concave portions 6pr may be connected to each other. In this case, the adhesion of the second collector electrode 8b to the protective layer 6 can be further improved. As a result, for example, the second collector electrode 8b is less likely to peel off from the protective layer 6.

Also, here, for example, when looking down on the surface of the electrode layer 8bl side of the protective layer 6, the ratio of the concave portion 6pr in the area per unit area of the convex portion 6p is set to 5% to 40 At about %, it becomes easy to improve the adhesion of the second collector electrode 8b to the protective layer 6. Here, for example, after removing the back electrode 8 of the solar cell element 10 by etching with hydrochloric acid or the like, the surface of the protective layer 6 on the electrode layer 8bl side is observed by SEM, and the electrode layer 8bl of the protective layer 6 is viewed from above Side face. The unit area is set in the range of 10 μm ² to 20 μm ² , for example.

Here, for example, as shown in FIGS. 4( b) and 7, the non-convex portion 6ap of the protective layer 6 may have one or more concave portions 6pr like the convex portion 6p. Thereby, for example, a plurality of concave portions 6pr can be present over a wide range of the portion of the second collector electrode 8b on the electrode layer 8bl side of the protective layer 6. Furthermore, for example, the electrode component containing the glass component in the state of constituting the electrode layer 8bl of the second collector electrode 8b is also located in the internal space SC1 of the concave portion 6pr of the non-convex portion 6ap. With this configuration, when the second collector electrode 8b is formed, the distribution of the components of the first metal paste applied on the protective layer 6 is unlikely to vary. Thus, for example, on the back surface 10bs side of the solar cell element 10, the distribution of the adhesiveness between the protective layer 6 and the second collector electrode 8b is less likely to vary. As a result, for example, peeling of the second collector electrode 8b from the protective layer 6 is less likely to occur. Therefore, the photoelectric conversion efficiency in the PERC type solar cell element 10 can be improved.

<1-3. Insulating paste> In the first embodiment, for example, in order to form the protective layer 6, two types of insulating paste are used. The two types of insulating paste include a first insulating paste and a second insulating paste.

Each of the first insulating paste and the second insulating paste includes, for example, a silicone resin, an organic solvent, and a plurality of fillers. The siloxane resin is a siloxane compound having a Si-O-Si bond (siloxane bond). Specifically, as the siloxane resin, for example, a low-molecular-weight resin having a molecular weight of 10,000 or less produced by polycondensation of alkoxysilane, silazane, or the like is hydrolyzed.

Here, the plurality of fillers in the first insulating paste include fillers whose main component is an inorganic material (also referred to as inorganic fillers). The plurality of fillers in the second insulating paste include fillers whose main component is an organic material (also called organic fillers). The plurality of fillers in the second insulating paste may also contain inorganic fillers.

<1-4. Manufacturing of insulating paste> <1-4-1. Manufacturing of first insulating paste> The first insulating paste can be manufactured as follows.

First, a mixed solution is prepared by mixing the precursor of the silicone resin, water, organic solvent, catalyst, and filler.

As the precursor of the siloxane resin, for example, a silane compound having a Si-O bond or a silazane compound having a Si-N bond can be used. These compounds have the property of being hydrolyzed (also known as hydrolyzability). In addition, the precursor of the silicone resin undergoes polycondensation by hydrolysis to become a silicone resin.

The silane compound is represented by the following general formula 1.

(R1) _n Si(OR2) _(4-n) (Formula 1).

N in the general formula 1 is, for example, any integer of 0, 1, 2, and 3. In addition, R1 and R2 in the general formula 1 represent the following hydrocarbon groups, that is, alkyl (-C _m H _2m+1 ) or phenyl such as methyl (-CH ₃ ) and ethyl (-C ₂ H ₅ ) (-C ₆ H ₅ ) etc. Here, m is a natural number.

Here, the silane compound includes, for example, a silane compound having at least R1 having an alkyl group (also referred to as an alkyl-based silane compound). Specifically, examples of the alkyl silane compound include methyltrimethoxysilane (CH ₃ -Si-(OCH ₃ ) ₃ ) and dimethyldimethoxysilane ((CH ₃ ) ₂ -Si -(OCH ₃ ) ₂ ), triethoxymethyl silane (CH ₃ -Si-(OC ₂ H ₅ ) ₃ ), diethoxy dimethyl silane ((CH ₃ ) ₂ -Si-(OC ₂ H ₅ ) ₂ ), trimethoxypropyl silane ((CH ₃ O) ₃ -Si-(CH ₂ ) ₂ CH ₃ ), triethoxypropyl silane ((C ₂ H ₅ O) ₃ -Si- (CH ₂ ) ₂ CH ₃ ), hexyltrimethoxysilane ((CH ₃ O) ₃ -Si-(CH ₂ ) ₅ CH ₃ ), triethoxyhexylsilane ((C ₂ H ₅ O) ₃ -Si -(CH ₂ ) ₅ CH ₃ ), triethoxyoctyl silane ((C ₂ H ₅ O) ₃ -Si-(CH ₂ ) ₇ CH ₃ ) and decyl trimethoxy silane ((CH ₃ O) ₃ -Si-(CH ₂ ) ₉ CH ₃ ) and so on.

Here, for example, if the alkyl group is a methyl group, an ethyl group, or a propyl group, when the precursor of the silicone resin is hydrolyzed, alcohol as a by-product with a small carbon number and a volatile by-product may be formed. By this, it becomes easy to remove by-products in the following steps. As a result, for example, when the protective layer 6 is formed, pores due to evaporation of by-products are less likely to be generated, whereby the protective layer 6 becomes dense, and the barrier property of the protective layer 6 can be improved.

Here, for example, in the case where the silicone resin precursor has a phenyl group, it may be a by-product produced by hydrolysis and polycondensation of the phenyl group when the silicone resin precursor is hydrolyzed and condensed Used under the condition of the removed silicone resin. By this, for example, the change in the viscosity of the insulating paste due to the hydrolysis and polycondensation reaction of the silicone resin is reduced, and it becomes easy to stabilize the viscosity of the insulating paste. Also, for example, if the silicone resin, the organic solvent, and the filler are mixed to produce an insulating paste in a state where the by-products have been removed, the amount of by-products contained in the insulating paste decreases. Therefore, if such an insulating paste is generated, in the case of applying the insulating paste by a screen printing method, for example, the emulsion of the screen-making plate can be reduced from being dissolved by-products. As a result, the size of the pattern of the screen-making becomes difficult to change.

The silane compound includes, for example, a silane compound in which R1 and R2 have both a phenyl group and an alkyl group. Examples of such silane compounds include trimethoxyphenyl silane (C ₆ H ₅ -Si-(OCH ₃ ) ₃ ) and dimethoxydiphenyl silane ((C ₆ H ₅ ) ₂ -Si- (OCH ₃ ) ₂ ), methoxytriphenylsilane ((C ₆ H ₅ ) ₃ -Si-OCH ₃ ), triethoxyphenylsilane (C ₆ H ₅ -Si-(OC ₂ H ₅ ) ₃ ), diethoxydiphenylsilane ((C ₆ H ₅ ) ₂ -Si-(OC ₂ H ₅ ) ₂ ), triethoxysilane ((C ₆ H ₅ ) ₃ -Si-OC ₂ H ₅ ), triisopropoxyphenylsilane (C ₆ H ₅ -Si-(OCH(CH ₃ ) ₂ ) ₃ ), diisopropoxydiphenylsilane ((C ₆ H ₅ ) _2- Si-(OCH(CH ₃ ) ₂ ) ₂ ) and isopropyloxytriphenylsilane ((C ₆ H ₅ ) ₃ -Si-OCH(CH ₃ ) ₂ ), etc.

Among these silane compounds, for example, if a silane compound containing two or more OR bonds is used, the number of siloxane bonds (Si-O-Si bonds) generated by polycondensation after hydrolysis of the silane compounds can be obtained increase. Thereby, the network structure of the siloxane bond in the silicon oxide forming the protective layer 6 can be increased. As a result, the barrier property of the protective layer 6 can be improved.

In addition, the silazane compound may be any of an inorganic silazane compound and an organic silazane compound. Here, examples of the inorganic silazane compound include polysilazane (-(H ₂ SiNH)-). Examples of organic silazane compounds include hexamethyldisilazane ((CH ₃ ) ₃ -Si-NH-Si-(CH ₃ ) ₃ ) and tetramethylcyclodisilazane ((CH ₃ ) ₂ -Si-(NH) ₂ -Si-(CH ₃ ) ₂ ) and tetraphenylcyclodisilazane ((C ₆ H ₅ ) ₂ -Si-(NH) ₂ -Si-(C ₆ H ₅ ) ₂ ) etc.

Water is a liquid used to hydrolyze the precursor of silicone resin. For example, pure water is used as water. For example, Si-OH bond and HO-CH ₃ (methanol) are generated by the reaction of water with respect to the Si-OCH ₃ bond of the silane compound.

The organic solvent is a solvent used to generate a paste containing a silicone resin from a precursor of the silicone resin. In addition, the organic solvent can mix the silicone resin precursor with water. As the organic solvent, for example, diethylene glycol monobutyl ether, methyl cellosolve, ethyl cellosolve, ethyl alcohol, 2-(4-methylcyclohex-3-enyl)propane-2 -Alcohol or 2-propanol, etc. Here, any one of these organic solvents and an organic solvent in which two or more organic solvents are mixed may be used.

The catalyst can control the reaction rate when the precursor of the silicone resin undergoes hydrolysis and polycondensation. For example, the Si-OR bond (for example, R is an alkyl group) included in the precursor of the silicone resin can be hydrolyzed and polycondensed, and the Si-O-Si bond and H generated by more than two Si-OH can be adjusted ₂ The speed of O (water) reaction. As the catalyst, for example, one or more inorganic acids or one or more organic acids among hydrochloric acid, nitric acid, sulfuric acid, boric acid, phosphoric acid, hydrofluoric acid, and acetic acid can be used. In addition, as the catalyst, for example, one or more types of inorganic salt groups or one or more types of organic salt groups among ammonia, sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, and pyridine can also be used. Furthermore, the catalyst may be, for example, a combination of an inorganic acid and an organic acid, or a combination of an inorganic salt group and an organic salt group.

The filler is, for example, an inorganic filler containing silicon oxide, aluminum oxide or titanium oxide.

Regarding the mixing ratio of the materials to be mixed here, for example, it is adjusted in such a way that in the mixed solution after mixing all the materials, the concentration of the precursor of the silicone resin becomes 7 to 60% by mass, The concentration of water becomes 5 mass% to 40 mass% (also 10 mass% to 20 mass%), the concentration of catalyst becomes 1 ppm to 1000 ppm, the concentration of organic solvent becomes 5 mass% to 50 mass%, inorganic filler The concentration becomes 3% by mass to 30% by mass. As long as it is such a mixing ratio, for example, a silicone resin produced by hydrolysis and polycondensation of a precursor of a silicone resin may be contained in an insulating paste at an appropriate concentration. In addition, for example, an excessive increase in viscosity due to gelation is unlikely to occur in the insulating paste.

When the materials are mixed in this way, the silicone resin precursor reacts with water, and the hydrolysis of the silicone resin precursor begins. In addition, the precursor of the hydrolyzed silicone resin undergoes polycondensation, and the production of silicone resin begins.

Next, the mixed solution is stirred. Here, the mixed solution is stirred using, for example, a rotary mixer or a stirrer. If the mixed solution is stirred, the hydrolysis of the precursor of the silicone resin proceeds further. In addition, the precursor of the hydrolyzed silicone resin undergoes polycondensation and continues to produce the silicone resin. For example, in the case of stirring using a rotary mixer, the number of revolutions of the rotating roller using the rotary mixer is set to about 400 rpm to 600 rpm, and the stirring time is set to the stirring conditions of about 30 minutes to 90 minutes. If such stirring conditions are adopted, the silicone resin precursor, water, catalyst, and organic solvent can be uniformly mixed. In addition, when the mixed solution is stirred, for example, if the mixed solution is heated, the hydrolysis and polycondensation of the precursor of the siloxane resin easily proceed. With this, for example, it is possible to shorten the stirring time and improve productivity, and the viscosity of the mixed solution becomes easy to stabilize.

Next, the first insulating paste can be manufactured by evaporating water and catalyst from the mixed solution. Here, for example, in the case of applying the first insulating paste by the screen printing method, in order to prevent the emulsion of the screen from melting and change in size, by-products and organic solvents are also volatilized. The by-products include, for example, organic components such as alcohol produced by the reaction of the silicone resin precursor and water.

Here, for example, using a hot plate or a drying furnace, etc., under a condition where the processing temperature is about room temperature to about 90°C (also about 50°C to about 90°C) and the processing time is about 10 minutes to 600 minutes After that, the mixed solution is processed. If the treatment temperature is within the above temperature range, by-products can be removed. In addition, in the above temperature range, organic components as by-products are easily volatilized, and therefore, it is possible to shorten the processing time and improve productivity. Here, for example, if it is under reduced pressure, the organic component as a by-product is easily volatilized. As a result, it is possible to shorten the processing time and improve productivity. Also, for example, here, the precursor of the siloxane resin that remains unhydrolyzed when the mixed solution is stirred may be further hydrolyzed.

<1-4-2. Manufacturing of the second insulating paste> For the manufacturing method of the second insulating paste, for example, in the above-mentioned manufacturing method of the first insulating paste, an organic filler may be added to the mixed solution to replace all inorganic Filler or a part of inorganic filler. Here, for example, in order not to easily dissolve the organic filler due to the by-products and organic solvent in the mixed solution, the organic filler may be added to the mixed solution after the by-products and organic solvent in the mixed solution are volatilized, And stir the mixed solution.

Here, as the organic filler, for example, a material that is contained below the temperature at which the second insulating paste is dried when the protective layer 6 is formed and that thermally decomposes is used as a main component. The temperature at which the organic filler thermally decomposes is, for example, 300°C or lower. Examples of such materials include acrylic materials. The average particle size of the organic filler is, for example, about 1 μm or less. Also, here, for example, if 5 parts by mass to 20 parts by mass of an organic filler is added to 100 parts by mass of the mixed solution, the viscosity of the mixed solution and the concave portion 6pr formed in the protective layer 6 can be easily adjusted Of the number.

<1-5. Manufacturing method of solar cell element> An example of a manufacturing method of the solar cell element 10 will be described based on FIGS. 8(a) to 8(f).

First, the step of preparing the semiconductor substrate 1 (also referred to as the first step) is performed. The semiconductor substrate 1 has a first surface 1bs and a second surface 1fs facing in a direction opposite to the first surface 1bs.

Here, for example, first, the semiconductor substrate 1 is prepared as shown in FIG. 8(a). The semiconductor substrate 1 can be formed using an existing CZ (Czochralski, Czochralski) method or a casting method, for example. Here, an example of using a p-type polycrystalline silicon ingot produced by a casting method will be described. The ingot is sliced to a thickness of, for example, 250 μm or less to produce a semiconductor substrate 1. Here, for example, if the surface of the semiconductor substrate 1 is etched with a very small amount of an aqueous solution of sodium hydroxide, potassium hydroxide, hydrofluoric acid, or nitrofluoric acid, the cut surface of the semiconductor substrate 1 can be removed. Mechanically damaged layers and contaminated layers. At this time, for example, a part of the above-mentioned structure may be formed on the second surface 1fs of the semiconductor substrate 1, and at least a part of the uneven structure 1rg may also be formed on the first surface 1bs of the semiconductor substrate 1.

Next, as shown in FIG. 8(b), a structure is formed on the second surface 1fs of the semiconductor substrate 1. The structure can be formed by wet etching using an alkaline aqueous solution such as sodium hydroxide or an acid aqueous solution such as nitrofluoric acid, or dry etching using a reactive ion etching (Reactive Ion Etching: RIE) method. At this time, for example, at least a part of the uneven structure 1rg may be formed on the first surface 1bs of the semiconductor substrate 1.

Next, as shown in FIG. 8(c), a second semiconductor layer 3 as an n-type semiconductor region is formed on the surface layer portion on the second surface 1fs side of the semiconductor substrate 1 having a structure. The second semiconductor layer 3 can be, for example, a coating thermal diffusion method in which phosphorous pentoxide (P ₂ O ₅ ) in a paste form is applied to the surface of the semiconductor substrate 1 and thermally diffuses phosphorus, or in a gas form. Phosphorus oxychloride (POCl ₃ ) is formed as a diffusion source by gas phase thermal diffusion method and the like. The second semiconductor layer 3 is formed, for example, to have a depth of about 0.1 μm to 2 μm and a sheet resistance value of about 40 Ω/□ to 200 Ω/□.

For example, in the gas-phase thermal diffusion method, first, in an environment having a diffusion gas mainly containing POCl ₃ and the like, the semiconductor substrate 1 is subjected to a heat treatment at a temperature of about 600°C to 800°C for about 5 to 30 minutes, On the surface of the semiconductor substrate 1, phosphor glass is formed. Thereafter, the semiconductor substrate 1 is subjected to a heat treatment for about 10 to 40 minutes in an environment of inert gas such as argon or nitrogen at a relatively high temperature of about 800°C to 900°C. As a result, phosphorus diffuses from the phosphor glass to the semiconductor substrate 1, and the second semiconductor layer 3 is formed on the surface layer portion on the second surface 1fs side of the semiconductor substrate 1.

Here, when the second semiconductor layer 3 is formed, the second semiconductor layer may also be formed on the first surface 1bs side. In this case, the second semiconductor layer formed on the first surface 1bs side is removed by etching. For example, the second semiconductor layer formed on the first surface 1bs side can be removed by immersing the portion of the semiconductor substrate 1 on the first surface 1bs side with an aqueous solution of nitrofluoric acid. With this, the region having the p-type conductivity type can be exposed on the first surface 1bs of the semiconductor substrate 1. Thereafter, the phosphor glass attached to the second surface 1fs side of the semiconductor substrate 1 when the second semiconductor layer 3 is formed is removed by etching. In this way, if the second semiconductor layer formed on the first surface 1bs side is removed by etching with phosphor glass remaining on the second surface 1fs side, the second semiconductor layer on the second surface 1fs side can be reduced 3 Removal and damage. At this time, the second semiconductor layer formed on the third surface 1ss of the semiconductor substrate 1 may be removed together.

In addition, for example, a diffusion mask may be formed in advance on the first surface 1bs side of the semiconductor substrate 1, and the second semiconductor layer 3 may be formed by a vapor phase thermal diffusion method or the like, and then the diffusion mask may be removed. In this case, the second semiconductor layer is not formed on the first surface 1bs side, so there is no need to remove the second semiconductor layer on the first surface 1bs side.

Through the above processing, it is possible to prepare a second semiconductor layer 3 as an n-type semiconductor layer located on the second surface 1fs side, having an organization structure on the second surface 1fs, and having an uneven structure 1rg on the first surface 1bs including the first semiconductor Layer 2 of the semiconductor substrate 1.

Next, the step of forming the passivation layer 4 (also referred to as the second step) is performed. In the first embodiment, the passivation layer 4 is formed on at least the first surface 1bs of the semiconductor substrate 1.

Here, for example, as shown in FIG. 8(d), a passivation layer 4 mainly containing aluminum oxide is formed on the first surface 1bs of the first semiconductor layer 2 and on the second surface 1fs of the second semiconductor layer 3 . In addition, an anti-reflection layer 5 is formed on the passivation layer 4. The anti-reflection layer 5 is composed of, for example, a silicon nitride film or the like.

The passivation layer 4 can be formed by, for example, the CVD method or the ALD method. According to the ALD method, for example, the passivation layer 4 can be formed on the entire periphery of the semiconductor substrate 1 including the third surface 1ss. In the step of forming the passivation layer 4 by the ALD method, first, the semiconductor substrate 1 up to the stage where the second semiconductor layer 3 is formed is placed in the chamber of the film forming apparatus. Then, in a state where the semiconductor substrate 1 is heated to a temperature region of about 100° C. to 250° C., the following steps A to D are repeatedly performed a plurality of times to form a passivation layer 4 mainly containing alumina. With this, the passivation layer 4 having a desired thickness is formed.

[Step A] Aluminum raw materials such as trimethylaluminum (TMA) used to form alumina are supplied onto the semiconductor substrate 1 together with a carrier gas such as Ar gas or nitrogen gas. As a result, the aluminum raw material is absorbed around the entire semiconductor substrate 1. The time for supplying TMA is set to, for example, about 15 milliseconds (m seconds: msec) to about 3000 milliseconds. Here, at the beginning of step A, the surface of the semiconductor substrate 1 may also be terminated with OH groups. In other words, the surface of the semiconductor substrate 1 may also have a Si-O-H structure. This structure can be formed, for example, by processing the semiconductor substrate 1 with dilute hydrofluoric acid and then washing with pure water.

[Step B] The aluminum material in the chamber is removed by purging the chamber of the film forming apparatus with nitrogen. Furthermore, the aluminum raw materials that are physically adsorbed and chemisorbed within the aluminum raw materials of the semiconductor substrate 1 except for the components that are chemically adsorbed at the atomic layer level are removed. The time for purifying the chamber with nitrogen gas is set to, for example, about 1 second (sec) to several tens of seconds.

[Step C] By supplying an oxidizing agent such as water or ozone gas into the chamber of the film forming apparatus, the alkyl group contained in TMA is removed and substituted with an OH group. Thereby, an atomic layer of aluminum oxide is formed on the semiconductor substrate 1. The time during which the oxidant is supplied into the chamber is set to, for example, about 750 ms to 1100 ms. In addition, for example, if hydrogen gas is supplied into the chamber together with the oxidant, the aluminum oxide is more likely to contain hydrogen atoms.

[Step D] By purging the chamber of the film forming apparatus with nitrogen, the oxidant in the chamber is removed. At this time, for example, an oxidizing agent that does not contribute to the reaction when forming atomic layer grade alumina on the semiconductor substrate 1 is removed. Here, the time for purifying the chamber with nitrogen is set to, for example, 1 second or more to about several tens of seconds.

Afterwards, an aluminum oxide layer with a desired film thickness is formed by repeatedly performing a series of steps in accordance with the description, step A, step B, step C, and step D in sequence.

The anti-reflection layer 5 is formed using, for example, a PECVD method or a sputtering method. In the case of using the PECVD method, the semiconductor substrate 1 is heated to a temperature higher than that in the film formation of the anti-reflection layer 5 in advance. Thereafter, a mixed gas of silane (SiH ₄ ) and ammonia (NH ₃ ) is diluted with nitrogen (N ₂ ), and the reaction pressure is set to about 50 Pa to 200 Pa, and it is obtained by plasma decomposition by glow discharge decomposition It is deposited on the heated semiconductor substrate 1. Thus, the anti-reflection layer 5 is formed on the semiconductor substrate 1. At this time, the film formation temperature is set to about 350°C to 650°C. The prior heating temperature of the semiconductor substrate 1 is higher than the film forming temperature by about 50°C. In addition, as the frequency of the high-frequency power source required for glow discharge, a frequency of about 10 kHz to 500 kHz is used. In addition, the flow rate of the gas is appropriately determined according to the size of the reaction chamber and the like. For example, the flow rate of the gas is set to a range of about 150 milliliters (ml)/minute (sccm) to 6000 milliliters/minute (sccm). At this time, the value (B/A) obtained by dividing the flow rate B of the ammonia gas by the flow rate A of the silane gas is set in the range of 0.5 to 15.

Next, the step of forming the protective layer 6 (also referred to as the third step) is performed. In the first embodiment, at least on the first surface 1bs side of the semiconductor substrate 1, the protective layer 6 is formed by applying a solution on the passivation layer 4 to form a pattern including the holes CH1 and drying the solution. At this time, the protective layer 6 having a plurality of concave portions 6pr can be formed by using, for example, the first insulating paste and the second insulating paste as solutions.

Such a protective layer 6 can be formed by the following processing, for example. Here, first, the first insulating paste is applied on the passivation layer 4. Next, a second insulating paste is applied on the layer of the first insulating paste applied on the passivation layer 4. Next, apply the first insulating paste and the second insulating paste after application, using a hot plate or a drying furnace, etc., at a maximum temperature of about 200°C to 350°C and a heating time of 1 minute to 10 minutes Dry under left and right conditions. At this time, as shown in FIG. 9, a first protective layer region 6a derived from the first insulating paste and a second protective layer region derived from the second insulating paste located on the first protective layer region 6a are formed 6b的保护层6. Here, the organic filler contained in the second insulating paste is thermally decomposed by heat treatment during drying. With this, the portion where the organic filler disappears by thermal decomposition becomes a concave portion 6pr, and a protective layer 6 having a plurality of concave portions 6pr on the surface is formed.

In addition, such a protective layer 6 can also be formed by the following processing, for example. Here, first, the first insulating paste is applied on the passivation layer 4. Next, a second insulating paste is applied on the layer of the first insulating paste applied on the passivation layer 4. Next, using the first insulating paste and the second insulating paste after application, using a hot plate or a drying furnace, etc., the organic filler contained in the second insulating paste does not undergo thermal decomposition at a relatively low temperature (for example, 100°C Left and right) to dry. Next, an organic solvent is used to dissolve the organic filler on the surface of the second insulating paste after drying. Next, a drying process using a hot plate or a drying furnace to evaporate the organic solvent is performed. Thereby, the protective layer 6 having a plurality of concave portions 6pr on the surface is formed.

Here, for example, using a spray method, a coating method, or a screen printing method is equivalent to applying at least a part of the passivation layer 4 with the first insulating paste and the second insulating paste in a desired pattern. Thereby, for example, as shown in FIG. 8(e), a protective layer 6 is formed on at least a part of the passivation layer 4.

Next, a step of forming an electrode including the front electrode 7 and the back electrode 8 (also referred to as a fourth step) is performed. Here, for example, the rear electrode 8 is formed by arranging the electrode forming material on the protective layer 6 and the hole CH1 and heating the electrode forming material. The back electrode 8 formed at this time includes a second output extraction electrode 8a and a second collector electrode 8b. The second collector electrode 8b includes an electrode layer 8bl and a connection portion 8bc.

Here, for example, as shown in FIG. 8(f), the front electrode 7 and the back electrode 8 are formed.

The front electrode 7 is produced using, for example, a second metal paste (also referred to as a silver paste) containing metal powder containing silver as a main component, an organic medium, and glass frit. First, a second metal paste is applied on the second surface 1fs side of the semiconductor substrate 1. In the first embodiment, a second metal paste is applied on the anti-reflection layer 5 formed on the passivation layer 4 on the second surface 1fs. Here, the application of the second metal paste can be realized by screen printing or the like, for example. Then, after the application of the second metal paste, the solvent in the second metal paste may be evaporated and dried at a specific temperature. If the second metal paste is applied by screen printing, for example, the first output extraction electrode 7a, the first collector electrode 7b, and the auxiliary electrode 7c included in the front electrode 7 can be formed in one step. Thereafter, for example, the front surface is formed by firing the second metal paste under the condition that the maximum temperature in the baking furnace is set to 600°C to 850°C and the heating time is set to about tens of seconds to tens of minutes. Electrode 7.

The second output extraction electrode 8a included in the back electrode 8 is produced using, for example, a third metal paste (also referred to as silver paste) containing metal powder containing silver as a main component, an organic medium, and glass frit. As a method of applying the third metal paste to the semiconductor substrate 1, for example, a screen printing method or the like can be used. After the application of the third metal paste, the solvent in the third metal paste can be evaporated and dried at a specific temperature. Thereafter, by baking the third metal paste on the semiconductor substrate by setting the maximum temperature in the baking furnace at 600°C to 850°C and the heating time at about tens of seconds to tens of minutes A second output extraction electrode 8a is formed on the first surface 1bs side of 1.

The second collector electrode 8b included in the back electrode 8 is produced using, for example, a first metal paste (Al paste) containing metal powder containing aluminum as a main component, an organic medium, and glass frit. First, the first metal paste is applied to the first surface 1bs side of the semiconductor substrate 1 in contact with a part of the previously applied third metal paste. In the first embodiment, the first metal paste is applied on the protective layer 6 formed on the passivation layer 4 formed on the first surface 1bs and in the hole CH1. In this case, the first metal paste may be applied to substantially the entire surface of the first surface 1bs side of the semiconductor substrate 1 except for a portion where the second output extraction electrode 8a is to be formed. Here, the application of the first metal paste can be realized by screen printing, for example. At this time, the first metal paste also enters the internal space SC1 of the plurality of concave portions 6pr of the protective layer 6.

Here, after the application of the first metal paste, the solvent in the first metal paste may be evaporated and dried at a specific temperature. Thereafter, for example, by firing the first metal paste under the condition that the maximum temperature in the baking furnace is set to 600°C to 850°C and the heating time is set to about tens of seconds to tens of minutes, the semiconductor substrate The second collector electrode 8b is formed on the first surface 1bs side of 1. At this time, the electrode component including the glass of the second collector electrode 8b enters the internal space SC1 of the plurality of concave portions 6pr of the protective layer 6. In addition, at this time, in the hole portion CH1, the first metal paste burns the passivation layer 4 through firing, and is electrically connected to the first semiconductor layer 2. With this, the second collector electrode 8b is formed. At this time, along with the formation of the second collector electrode 8b, the third semiconductor layer 2bs is also formed. However, at this time, the first metal paste on the protective layer 6 is blocked by the protective layer 6. Therefore, when firing the first metal paste, the adverse effects caused by the firing hardly affect the passivation layer 4 blocked by the protective layer 6.

In this way, the back electrode 8 can be formed. Therefore, in the first embodiment, the first metal paste and the third metal paste are used as the electrode forming materials for forming the back electrode 8. Here, for example, the second output extraction electrode 8a may be formed after the second collector electrode 8b is formed. For example, even if the second output extraction electrode 8a is in direct contact with the semiconductor substrate 1, a passivation layer 4 or the like may be present between the second output extraction electrode 8a and the semiconductor substrate 1 without directly contacting the semiconductor substrate 1. In addition, the second output extraction electrode 8 a may be formed on the protective layer 6. In addition, the front electrode 7 and the back electrode 8 may be formed by applying respective metal pastes and firing them simultaneously. With this, the productivity of the solar cell element 10 can be improved. In addition, in this case, the thermal history applied to the semiconductor substrate 1 decreases, so that the output characteristics of the solar cell element 10 can be improved.

<1-6. Summary of the first embodiment> In the solar cell element 10 of the first embodiment, for example, the electrode component containing the glass component in the state of constituting the electrode layer 8bl of the second collector electrode 8b is present The concave portion 6pr of the convex portion 6p of the protective layer 6. With this structure, for example, when the first metal paste is applied on the protective layer 6 to form the second collector electrode 8b, even if there is an uneven structure on the surface of the protective layer 6, the glass component in the first metal paste, etc. It enters the concave portion 6pr existing in the convex portion 6p. Therefore, for example, in the first metal paste located on the convex portion 6p, a fluid component including a glass component and an organic medium is unlikely to flow out to a lower portion in the direction of gravity. Accordingly, in the first metal paste located on the convex portion 6p, the content of the glass component is not easily reduced. As a result, when the second collector electrode 8b is formed, the distribution of the components of the first metal paste applied on the protective layer 6 is unlikely to vary. At this time, for example, the adhesion of the second collector electrode 8b on the protective layer 6 is unlikely to vary. Furthermore, due to the presence of the glass component in the concave portion 6pr, the adhesion between the protective layer 6 in the convex portion 6p and the metal particles in the second collector electrode 8b can be improved. In addition, for example, when a part of the second collector electrode 8b enters the concave portion 6pr of the protective layer 6, a so-called anchor effect can be generated. Thereby, the adhesion of the second collector electrode 8b to the protective layer 6 can be improved. As a result, for example, peeling of the second collector electrode 8b from the protective layer 6 is less likely to occur. Therefore, the photoelectric conversion efficiency in the PERC type solar cell element 10 can be improved.

<2. Other Embodiments> The present invention is not limited to the above-mentioned first embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

<2-1. Second Embodiment> In the above-mentioned first embodiment, for example, as shown in FIG. 10(a) and FIG. 10(b), the protective layer 6 may have a plurality of layers inside the protective layer 6 6vd of each gap. Here, the diameter of the gap 6vd is d4. In this case, for example, a configuration in which the diameter d4 is shorter than the second distance D2 between the adjacent convex portions 6p and the third distance D3 between the adjacent connecting portions 8bc may be considered. Specifically, as the void portion 6vd, for example, a minute void portion having an internal space with a diameter d4 of about 0.1 μm to 1 μm is used. Also, here, for example, if the thickness (minimum film thickness) of the protective layer 6 other than the void portion 6vd is about 0.5 μm or more in the portion where the concave portion 6pr and the void portion 6vd are located in the protective layer 6, it can be ensured The protective layer 6 is used to protect the function of the passivation layer 4.

However, for example, when the protective layer 6 is formed and when the solar cell element 10 is used, the protective layer 6 may expand or contract in response to temperature changes, and contraction may occur corresponding to the polycondensation reaction of the protective layer 6. At this time, stress may be generated between the protective layer 6 and the layer adjacent to the protective layer 6 (also referred to as an adjacent layer). In contrast, for example, if a plurality of voids 6vd are located inside the protective layer 6, the stress generated between the protective layer 6 and the adjacent layer in a state adjacent to the protective layer 6 can pass through the protective layer 6 The plurality of gaps 6vd are relaxed. As a result, peeling is unlikely to occur between the protective layer 6 and the adjacent layer in a state adjacent to the protective layer 6. As a result, the photoelectric conversion efficiency in the PERC type solar cell element 10 can be improved.

In addition, here, for example, the distance (also referred to as a fourth distance) between adjacent ones of the plurality of voids 6vd is set to D4. As the fourth distance D4, for example, the distance between the centers of adjacent gaps 6vd is used. The fourth distance D4 may be, for example, the average value of the distances between the centers of adjacent gaps 6vd, the distance between adjacent gaps 6vd, or the distance between adjacent gaps 6vd Of the average. In this case, for example, a configuration in which the fourth distance D4 is shorter than the second distance D2 between the adjacent convex portions 6p and the third distance D3 between the adjacent connecting portions 8bc may be considered. At this time, for example, the density of the plurality of voids 6vd in the protective layer 6 is high to some extent. By this, for example, the stress generated between the protective layer 6 and the adjacent layer in a state adjacent to the protective layer 6 is easily relieved by the plurality of voids 6vd in the protective layer 6. Therefore, it is easy to improve the photoelectric conversion efficiency in the PERC type solar cell element 10.

The protective layer 6 having a plurality of voids 6vd inside can be formed by the following treatment, for example.

Here, first, the first insulating paste is applied on the passivation layer 4. Next, a second insulating paste is applied on the layer of the first insulating paste applied on the passivation layer 4. Next, the first insulating paste is applied on the layer of the second insulating paste applied on the layer of the first insulating paste. Next, a second insulating paste is applied on the layer of the first insulating paste applied on the layer of the second insulating paste. Then, the layer of the first insulating paste, the layer of the second insulating paste, the layer of the first insulating paste, and the layer of the second insulating paste are dried using a hot plate, a drying furnace, or the like. At this time, as a drying condition, a maximum temperature of about 200° C. to 350° C., and a heating time of about 1 minute to 10 minutes, at which the organic filler contained in the second insulating paste is thermally decomposed, are used. At this time, as shown in FIG. 11, a first protective layer region 6 a, a second protective layer region 6 b, a third protective layer region 6 c, and a fourth protective layer region are formed on the passivation layer 4 in the order described. 6d state positioning protective layer 6. Here, the first protective layer region 6a and the third protective layer region 6c are formed by drying the first insulating paste. The second protective layer region 6b and the fourth protective layer region 6d are formed by drying the second insulating paste. Then, at this time, the organic filler contained in the second insulating paste is thermally decomposed by the heat treatment at the time of drying. Thereby, in the second protective layer region 6b, a plurality of void portions 6vd are formed due to the disappearance of the organic filler, and on the surface of the fourth protective layer region 6d, a plurality of concave portions 6pr are formed due to the disappearance of the organic filler . As a result, it is possible to form the protective layer 6 having a plurality of concave portions 6pr on the surface and a plurality of void portions 6vd inside.

Here, for example, a layer obtained by containing an organic binder in the first insulating paste may be applied instead of the layer of the second insulating paste used to form the second protective layer region 6b in FIG. 11. In this case, for example, a plurality of voids 6vd can be generated by evaporating a part of the organic binder present in the organic binder of the layer of the first insulating paste when the first insulating paste is dried. Here, instead of forming at least one of the fourth protective layer region 6d in FIG. 11 and the second protective layer region 6b in FIG. 9, a layer obtained by containing an organic binder in the first insulating paste may be applied The second layer of insulating paste. In this case, for example, a plurality of concave portions 6pr can be generated by evaporating a part of the organic binder present in the organic binder of the layer of the first insulating paste when the first insulating paste is dried.

<2-2. Third Embodiment> In each of the above embodiments, for example, as shown in FIG. 12, when the protective layer 6 is seen through from the electrode layer 8bl side of the second collector electrode 8b, the protective layer 6 The concave portion 6pr may have a first area Ar1 and a second area Ar2 that differ in number per unit area. Here, the first region Ar1 is located on the outer peripheral portion OP1 side of the solar cell element 10. The second area Ar2 is located on the central portion CP1 side of the solar cell element 10. The unit area is set to about 100 mm ² to 400 mm ² , for example. Moreover, the number of unit areas per unit area of the concave portion 6pr existing in the first region Ar1 may be greater than the number of unit units area of the concave portion 6pr existing in the second region Ar2. With such a configuration, for example, on the back surface 10bs side of the solar cell element 10, the adhesion between the protective layer 6 and the second collector electrode 8b becomes higher on the outer peripheral portion OP1 side than on the central portion CP1 side. high.

The protective layer 6 having such a first region Ar1 and a second region Ar2 can be processed by, for example, applying the second insulating paste on the layer of the first insulating paste applied on the passivation layer 4 as follows form. First, the second insulating paste is applied to the area corresponding to the first area Ar1. Next, the second insulating paste having a lower content of the organic filler than the applied second insulating paste is applied to the region corresponding to the second region Ar2. Also, for example, in such a process, a second insulating paste may be applied on the layer of the first insulating paste applied on the passivation layer 4 and the first insulating paste and the second insulating paste may be dried Thereafter, the second insulating paste is applied on the layer of the first insulating paste applied on the layer of the second insulating paste. Thereby, the protective layer 6 having the plurality of voids 6vd and having the first region Ar1 and the second region Ar2 can be formed.

However, for example, as shown in FIGS. 13 and 14, a plurality of solar cell elements 10 can be used in the form of a solar cell module 100 that is electrically connected in series by a wiring material Tb and arranged in a plane Status positioning. In the solar cell module 100, a part (also called a photoelectric conversion part) 103 including a plurality of solar cell elements 10 is covered with a sealing material 102 and is located between the first protection member 101 and the first protection member 101 positioned in a state opposed to each other The gap of the second protection member 104. Here, the solar cell module 100 mainly has a light-receiving surface (also referred to as a front surface) 100fs, and a surface (also referred to as a back surface) 100bs located on the opposite side to the front surface 100fs. Furthermore, in the solar cell module 100, the plate-shaped second protective member 104 having translucency is located on the front surface 100fs side, and the plate-shaped or sheet-shaped first protective member 101 is located on the back surface 100bs side. Moreover, the sealing material 102 located in the gap between the first protection member 101 and the second protection member 104 includes: a first sealing material 102b located on the back 100bs side; and a second sealing material 102u located on the front surface 100fs side.

For example, as shown in FIG. 15, the solar cell module 100 can be laminated with the first protection member 101, the first sheet SH1, the photoelectric conversion portion 103, the second sheet SH2, and the second protection in order according to the description. The laminated body of the member 104 is manufactured by laminating and integrating. The first sheet SH1 is a sheet material that becomes the raw material of the first sealing material 102b, and the second sheet SH2 is a sheet material that becomes the raw material of the second sealing material 102u. Here, when laminating the laminate, the thickness of the sealing material 102 is large between the plurality of solar cell elements 10. Therefore, between the plurality of solar cell elements 10, the expansion and contraction of the sealing material 102 become larger. Thereby, when laminating, for example, on the back surface 10bs side of the solar cell element 10, a large stress can be applied to the area of the back surface 10bs along the outer peripheral portion OP1. On the other hand, on the back surface 10bs side of the solar cell element 10 of the third embodiment, the protective layer 6 and the second set are located on the first area Ar1 on the outer peripheral portion OP1 side compared to the second area Ar2 on the central portion CP1 side The electrical electrode 8b has higher adhesion. Therefore, for example, when performing the lamination process of the laminate, the second collector electrode 8b is not easily peeled off from the protective layer 6.

<2-3. Others> In the above embodiments and various modifications, for example, the second output extraction electrode 8a on the protective layer 6 may be an electrode layer containing a glass component. In this case, the glass component of the second output extraction electrode 8a may be located in the inner space of the concave portion 6pr of the protective layer 6. With this, by improving the adhesion of the second output extraction electrode 8a to the protective layer 6, the photoelectric conversion efficiency in the solar cell element 10 can also be improved.

In the above embodiments and various modifications, when looking down on the surface of the protective layer 6 on the electrode layer 8bl side, the ratio of the concave portion 6pr to the area per unit area of the convex portion 6p is not Limited to about 5% to 40%. The ratio can be easily increased by, for example, appropriately setting the content of the glass component and the type of the glass component in the second collector electrode 8b or the first metal paste used to form the second collector electrode 8b. The adhesion of the second collector electrode 8b to the protective layer 6. In other words, for example, the ratio may be appropriately set to include a range of different ratios of some or all of the range of about 5% to 40%, or a range of ratios different from about 5% to 40%.

In the above embodiments and various modifications, for example, as shown in FIG. 16(a), the passivation layer 4 is located on the first surface 1bs to the third surface 1ss, and the protective layer 6 is located on the first surface 1bs On the passivation layer 4 on the outer edge portion Ed1, it is not limited to this. For example, as shown in FIG. 16(b), the passivation layer 4 and the protection may not be present on the first surface 1bs along the outer edge Ed1 of the first surface 1bs (also referred to as the outer edge region) Ao1 Layer 6 and anti-reflection layer 5. In other words, the passivation layer 4 and the anti-reflection layer 5 on the third surface 1ss and the passivation layer 4 and the protective layer 6 on the first surface 1bs may be separated on the outer peripheral area Ao1. At this time, it may be considered that the outer edge region Ao1 is located in the range from the outer edge portion Ed1 to the distance L1 in the first surface 1bs. The distance L1 can be set to about 0.5 mm to 2 mm, for example. In the case of adopting such a configuration, for example, as shown in FIG. 16(b), the second collector electrode 8b does not exist on the outer edge area Ao1 of the first surface 1bs, or as shown in FIG. 16(c) As shown, the second collector electrode 8b is present on at least a part of the outer edge region Ao1 of the first surface 1bs. In addition, here, for example, as shown in FIGS. 17(a) to 17(c), a portion on the third surface 1ss to the side of the outer edge Ed1 in the outer edge area Ao1 of the first surface 1bs Above, there is the passivation layer 4 and the anti-reflection film 5. At this time, it may be considered that the passivation layer 4 and the anti-reflection film 5 are located in the range from the outer edge portion Ed1 to the distance L2 on the outer edge area Ao1. The distance L2 can be set to about 0.1 mm to 1 mm, for example. In the case of adopting such a configuration, for example, as shown in FIGS. 17(a) and 17(b), the passivation may be performed on the outer edge area Ao1 from the third surface 1ss to the first surface 1bs. Compared with the layer 4, the antireflection layer 5 exists closer to the central portion of the first surface 1bs. Also, for example, as shown in FIG. 17( c ), both the passivation layer 4 and the anti-reflection film 5 may be present on the outer edge region Ao1 from the outer edge portion Ed1 to the distance L2. Furthermore, in the example shown in FIG. 17(c), as shown in FIG. 16(c) or FIG. 17(b), there may also be a first part on at least a part of the outer edge region Ao1 of the first surface 1bs 2 Collector electrode 8b.

Of course, all or part of each of the above-described embodiments and various modifications may be combined within an appropriate and non-contradictory range.

1‧‧‧Semiconductor substrate 1bs‧‧‧First surface 1fs‧‧‧Second surface 1p‧‧‧Convex portion 1r‧‧‧Concave portion 1rg‧‧‧Concave-convex structure 1ss‧‧‧3rd surface 2‧‧‧First Semiconductor layer 2bs‧‧‧third semiconductor layer 3‧‧‧second semiconductor layer 4‧‧‧passivation layer 5‧‧‧anti-reflection layer 6‧‧‧protection layer 6a‧‧‧1st protection layer area 6b‧‧‧ 2nd protective layer region 6c‧‧‧3rd protective layer region 6d‧‧‧4th protective layer region 6ap‧‧‧non-convex part 6p Section 7‧‧‧ Front electrode 7a‧‧‧First output extraction electrode 7b‧‧‧First collector electrode 7c‧‧‧Auxiliary electrode 8‧‧‧Back electrode 8a‧‧‧Second output extraction electrode 8b‧‧‧ 2nd collector electrode 8bc‧‧‧connecting part 8bl‧‧‧electrode layer 10‧‧‧solar cell element 10bs‧‧‧back 10fs‧‧‧front surface 100bs‧‧‧back 100fs‧‧‧front surface 101‧‧‧ First protection member 102‧‧‧Sealing material 102b‧‧‧First sealing material 102u‧‧‧Second sealing material 103‧‧‧Photoelectric conversion unit 104‧‧‧Second protection member 106‧‧‧‧Protection layer 108‧‧ ‧Back electrode 108a‧‧‧Second output extraction electrode 108b‧‧‧Second collector electrode 110‧‧‧Solar cell element Aa0‧‧‧Ao1‧‧‧Outer edge area Ar1‧‧‧First area Ar2‧‧ ‧The second area CH1‧‧‧Hole CP1‧‧‧Central part D1‧‧‧First distance D2‧‧‧Second distance D3‧‧‧The third distance D4‧‧‧The fourth distance d4‧‧‧Diameter Ed1 ‧‧‧Outer edge part L1‧‧‧L2‧‧‧Distance OP1‧‧‧Outer part P1‧‧‧Part P11‧‧‧Part P12‧‧‧Part P16‧‧‧Part SC1‧‧‧Internal space SH1‧ ‧‧1st sheet SH2‧‧‧2nd sheet X‧‧‧direction Y‧‧‧direction Z‧‧‧direction

FIG. 1 is a plan view showing the appearance of the front surface side of an example of the solar cell element of the first embodiment. 2 is a plan view showing the appearance of the back side of an example of the solar cell element of the first embodiment. FIG. 3 is a diagram showing an example of a virtual cut surface of the solar cell element taken along line III-III of FIGS. 1 and 2. FIG. 4(a) is an enlarged view showing an example of a virtual cut face of part P1 in FIG. 3. FIG. FIG. 4(b) is an enlarged view showing an example of a virtual cut face of part P11 of FIG. 4(a). FIG. 5(a) is an enlarged view showing an example of a virtual cut face of part P1 in FIG. 3. FIG. FIG. 5(b) is an enlarged view showing an example of a virtual cut face of part P11 in FIG. 5(a). FIG. 6(a) is a diagram for explaining the conditions of a peel test performed on a solar cell element of a reference example. FIG. 6(b) is a graph showing the results of a peel test performed on a solar cell element of a reference example. FIG. 7 is an enlarged view showing an example of a virtual cut face of part P12 of FIG. 5(a). 8(a) to 8(f) are diagrams each showing an example of an imaginary cut-off face corresponding to the imaginary cut-off face of FIG. 3 in a state in the middle of manufacturing the solar cell element of the first embodiment. . 9 is a diagram for explaining an example of the structure of the protective layer in the first embodiment. FIG. 10(a) is an enlarged view showing an example of a virtual cut surface portion of a portion corresponding to the portion P11 of FIG. 4(a) in the solar cell element of the second embodiment. FIG. 10(b) is an enlarged view showing an example of a virtual cut surface portion of the solar cell element of the second embodiment corresponding to the portion P11 of FIG. 5(a). FIG. 11 is a diagram for explaining an example of the structure of the protective layer in the second embodiment. 12 is a plan view showing the appearance of the back side of an example of the solar cell element of the third embodiment. Fig. 13 is a plan view showing the appearance of the front surface side of an example of the solar cell module of the third embodiment. 14 is a diagram showing an example of a virtual cut surface of the solar cell element along the line XIV-XIV in FIG. 13. 15 is a diagram showing an example of a virtual cut face corresponding to the virtual cut face of FIG. 14 in a state in the middle of manufacturing the solar cell module of the third embodiment. FIG. 16(a) is an enlarged view showing an example of a virtual cut face of part P16 in FIG. 3. FIG. FIG. 16(b) is an enlarged view showing a first example of a hypothetical cut-off part of a part corresponding to part P16 of FIG. 3 in a solar cell element of a modified example. FIG. 16(c) is an enlarged view showing a second example of the virtual cut-off face portion of the portion corresponding to the portion P16 of FIG. 3 in the solar cell element of a modified example. FIG. 17(a) is an enlarged view showing a first example of an imaginary cut-off portion of a portion corresponding to the portion P16 of FIG. 3 in a solar cell element of another modification. FIG. 17(b) is an enlarged view showing a second example of a virtual cut-off portion of a portion corresponding to the portion P16 of FIG. 3 in the solar cell element of another modification. FIG. 17(c) is an enlarged view showing a third example of the virtual cut surface of the portion corresponding to the portion P16 of FIG. 3 in the solar cell element of another modification.

5‧‧‧Anti-reflection layer

7‧‧‧Front electrode

7a‧‧‧The first output extraction electrode

7b‧‧‧First collector electrode

7c‧‧‧Auxiliary electrode

10‧‧‧Solar battery element

10fs‧‧‧Front surface

X‧‧‧ direction

Y‧‧‧ direction

Z‧‧‧ direction

Claims (7)

A solar cell element comprising: a semiconductor substrate; a passivation layer on the first surface of the semiconductor substrate; a protective layer on the passivation layer; and an electrode layer on the protective layer, including A glass component; and the protective layer has a plurality of convex portions on the surface of the electrode layer side, and the plurality of convex portions respectively have concave portions for the glass component in the internal space on the electrode layer side. The solar cell element according to claim 1, wherein the passivation layer and the protective layer have a plurality of holes positioned in a state of penetrating the passivation layer and the protective layer, and the solar cell element includes: a plurality of connection portions, which Located in the plurality of hole portions; and the plurality of concave portions; and the first of the concave portions adjacent to each other in the plurality of concave portions in the state of electrically connecting the electrode layer and the semiconductor substrate The distance is shorter than the second distance between adjacent ones of the plurality of convex portions and the third distance between adjacent ones of the plurality of connecting portions. The solar cell element according to claim 1, wherein The protective layer is located on the surface of the electrode layer side, and has non-convex portions different from the plurality of convex portions, and the non-convex portions have concave portions on the electrode layer side for the glass component to be located in the internal space thereof . The solar cell element according to claim 2, wherein the protective layer is located on the surface of the electrode layer side, and has non-convex portions different from the plurality of convex portions, and the non-convex portions have respective The glass component is located in the concave part of its internal space. The solar cell element according to any one of claims 1 to 4, wherein the protective layer has a third position on the outer peripheral side of the solar cell element when the protective layer and the semiconductor substrate are seen through from the electrode layer side in plan view 1 area, and a second area located on the central portion side of the solar cell element; and the number of unit areas per unit area of the concave portion existing in the first area is greater than the concave portion existing in the second area The above number per unit area. The solar cell element according to any one of claims 1 to 4, wherein the protective layer has a plurality of voids inside the protective layer. The solar cell element according to claim 5, wherein the protective layer has a plurality of voids inside the protective layer.

Images