Solar cell and solar cell manufacturing method

Abstract

Provided is a see-through solar cell having high photoelectric conversion efficiency. A solar cell 1 according to an aspect of the present invention comprises: a semiconductor substrate 10 formed as a flat plate and having a plurality of light-transmitting openings 11 extending therethrough in a thickness direction thereof; a first semiconductor layer 20 stacked on one major surface side of the semiconductor substrate 10; a second semiconductor layer 30 stacked on another major surface side of the semiconductor substrate 10; a first electrode 60 stacked on the first semiconductor layer 20; and a second electrode 70 stacked on the second semiconductor layer 30. The inner circumferential surface of the light-transmitting openings 11 includes a first circumferential surface portion 12 positioned closer to the first semiconductor layer 20, and a second circumferential surface portion 13 positioned closer to the second semiconductor layer 30 and having a surface property different from that of the first circumferential surface portion 12.

Description

[Technical Field]

[0001] The present invention relates to a solar cell and a method for manufacturing a solar cell. [Background technology]

[0002] The use of solar cells as a clean energy source is expanding. Conventional solar cells are not installed near windows or other surfaces to block light. Therefore, see-through solar cells with light-transmitting apertures are also being considered. For example, Patent Document 1 discloses a solar cell in which multiple apertures are formed in a semiconductor substrate, which has a p-type semiconductor film stacked on an n-type semiconductor base material that generates carriers when light is incident, forming a p-n junction for collecting carriers, and finger electrodes are arranged on the light-receiving surface of the semiconductor substrate to avoid the apertures. Patent Document 1 also proposes etching using an electrolyte containing fluoride as a relatively inexpensive method for forming apertures in a semiconductor substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-299672 Summary of the Invention [Problem to be solved by the invention]

[0004] When openings are formed in the semiconductor substrate of a solar cell by etching, carrier recombination occurs on the inner circumferential surface of the opening, which can reduce photoelectric conversion efficiency. In particular, increasing the aperture ratio increases carrier recombination on the inner circumferential surface of the opening, resulting in a significant decrease in photoelectric conversion efficiency. Furthermore, when finger electrodes are arranged to avoid the light-transmitting openings, a region with a relatively large distance to the finger electrodes is formed between the openings aligned parallel to the extension direction of the finger electrodes. When the distance to the finger electrodes is large, carriers excited by light recombine and disappear before being collected by the finger electrodes, resulting in a disadvantage of low photoelectric conversion efficiency. Therefore, an object of the present invention is to provide a see-through solar cell with high photoelectric conversion efficiency and a method for manufacturing the solar cell. [Means for solving the problem]

[0005] A solar cell according to one embodiment of the present invention comprises a semiconductor substrate formed in a plate shape and having a plurality of light-transmitting openings penetrating in the thickness direction, a first semiconductor layer stacked on one main surface side of the semiconductor substrate, a second semiconductor layer stacked on the other main surface side of the semiconductor substrate, a first electrode stacked on the first semiconductor layer, and a second electrode stacked on the second semiconductor layer, wherein the inner surface of the light-transmitting opening has a first peripheral surface portion located on the side of the first semiconductor layer, and a second peripheral surface portion located on the side of the second semiconductor layer and having a surface texture different from that of the first peripheral surface portion.

[0006] In the solar cell described above, the semiconductor substrate may be covered by the first semiconductor layer at the first peripheral surface portion, and the semiconductor substrate may be exposed at the second peripheral surface portion.

[0007] A solar cell manufacturing method according to one embodiment of the present invention includes the steps of: forming an annular groove by irradiating a semiconductor substrate with laser light; and forming an opening in the semiconductor substrate by separating an area inside the annular groove of the semiconductor substrate by etching or fracturing the bottom of the annular groove.

[0008] The above-described solar cell manufacturing method may further include a step of forming a film on the semiconductor substrate between the step of forming the annular groove and the step of forming the opening.

[0009] A solar cell according to another aspect of the present invention comprises a photoelectric converter having a semiconductor substrate and a semiconductor layer stacked on the semiconductor substrate, and having a plurality of light-transmitting openings penetrating from the front to the back, a front electrode stacked on the front surface of the photoelectric converter, and a back electrode stacked on the back surface of the photoelectric converter, wherein the front electrode has a plurality of surrounding portions that individually surround the plurality of light-transmitting openings.

[0010] In the solar cell described above, the surrounding portion may be polygonal.

[0011] In the solar cell described above, the length of each side of the surrounding portion may be constant.

[0012] In the solar cell described above, the minimum value of the distance between each side of the surrounding portion and the light-transmitting opening may be 50% or more of the maximum value.

[0013] In the solar cell described above, the distance between each side of the surrounding portion and the light-transmitting opening may be 20% or more and 150% or less of the diameter of the light-transmitting opening.

[0014] In the solar cell described above, the surface electrode may be made up of a plurality of electrode wires arranged parallel to each other and at equal intervals, and may have three sets of electrode wire groups that intersect with each other at different angles.

[0015] In the solar cell described above, the surrounding portions may be hexagonal in shape, with vertices in contact with each other, and define a triangular space therebetween that does not include the light-transmitting opening.

[0016] In the solar cell described above, the area inside the plurality of surrounding portions may be two to five times the area outside the plurality of surrounding portions.

[0017] In the solar cell described above, the rear electrode may have a plurality of surrounding portions that surround the plurality of light-transmitting openings, respectively. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a see-through solar cell with high photoelectric conversion efficiency and a method for manufacturing the solar cell. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a partial plan view of a solar cell according to an embodiment of the present invention. [Figure 2] 2 is a partial cross-sectional view of the solar cell of FIG. 1 taken along the line XX. [Figure 3] 1 is a flowchart showing the steps of a solar cell manufacturing method according to one embodiment of the present invention. [Figure 4] 4 is a partial cross-sectional view illustrating one step of the solar cell manufacturing method of FIG. 3. FIG. [Figure 5] 5 is a partial cross-sectional view illustrating a step subsequent to that of FIG. 4 in the method of manufacturing the solar cell of FIG. [Figure 6] 6 is a partial cross-sectional view illustrating a step subsequent to that of FIG. 5 in the method of manufacturing the solar cell of FIG. [Figure 7] 7 is a partial cross-sectional view illustrating a step subsequent to that of FIG. 6 in the method of manufacturing the solar cell of FIG. [Figure 8] 8 is a partial cross-sectional view illustrating a step subsequent to that of FIG. 7 in the method of manufacturing the solar cell of FIG. [Figure 9] 9 is a partial cross-sectional view illustrating a step subsequent to that of FIG. 8 in the method of manufacturing the solar cell of FIG. 3. FIG. [Figure 10] 10 is a partial plan view illustrating the process of FIG. 9. FIG. [Figure 11] FIG. 4 is a schematic plan view of a solar cell according to a second embodiment of the present invention. [Figure 12] 12 is a schematic cross-sectional view of the solar cell of FIG. 11 taken along line YY. [Figure 13] FIG. 10 is a schematic plan view of a solar cell according to a third embodiment of the present invention. [Figure 14]FIG. 10 is a schematic plan view of a solar cell according to a fourth embodiment of the present invention. [Figure 15] FIG. 10 is a schematic plan view of a solar cell according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings. The same or equivalent parts in each drawing will be designated by the same reference numerals. For simplification, illustrations and reference numerals of components may be omitted. In such cases, other drawings should be referred to. The shapes and dimensions of various components in the drawings have been adjusted for clarity.

[0021] Fig. 1 is a partial plan view of a solar cell 1 according to a first embodiment of the present invention. Fig. 2 is a partial cross-sectional view of the solar cell. The solar cell 1 includes a semiconductor substrate 10 formed in a plate shape, a first semiconductor layer 20 laminated on one main surface side (light-receiving surface side) of the semiconductor substrate 10, a second semiconductor layer 30 laminated on the other main surface side of the semiconductor substrate 10, a first passivation layer 40 interposed between the semiconductor substrate 10 and the first semiconductor layer 20, a second passivation layer 50 interposed between the semiconductor substrate 10 and the second semiconductor layer 30, a first electrode 60 laminated on the first semiconductor layer 20, and a second electrode 70 laminated on the second semiconductor layer 30.

[0022] The semiconductor substrate 10 functions as a photoelectric conversion substrate that absorbs incident light and generates photocarriers (electrons and holes). The semiconductor substrate 10 may have a pyramidal fine uneven structure called a texture structure in order to improve the incidence of light on the light-receiving surface.

[0023] The semiconductor substrate 10 can be formed of a crystalline silicon material such as single crystal silicon or polycrystalline silicon. The semiconductor substrate 10 may also be formed of other semiconductor materials such as gallium arsenide (GaAs). The semiconductor substrate 10 can be, for example, an n-type semiconductor substrate in which a crystalline silicon material is doped with an n-type dopant. An example of an n-type dopant is phosphorus (P). By using crystalline silicon as the material for the semiconductor substrate 10, dark current is relatively small, and a relatively high output (stable output regardless of illuminance) can be obtained even when the intensity of incident light is low.

[0024] The semiconductor substrate 10 has a plurality of light-transmitting openings 11 penetrating through it in the thickness direction. The light-transmitting openings 11 allow light to pass through and reach the back side (the side opposite the light-receiving surface) of the solar cell 1. The shape of the light-transmitting openings 11 in a plan view is typically circular, but may be any shape such as elliptical or polygonal.

[0025] The light-transmitting openings 11 are preferably formed so as to be dispersed over substantially the entire semiconductor substrate 10 in order to admit light evenly, but may not be provided, for example, in the peripheral portion of the semiconductor substrate 10 or in a strip-shaped region that crosses the semiconductor substrate 10 in order to ensure the strength of the semiconductor substrate 10. The light-transmitting openings 11 are preferably arranged regularly in order to admit light more evenly and to improve the aesthetic appearance.

[0026] The area ratio of the light-transmitting openings 11 in the semiconductor substrate 10, i.e., the aperture ratio of the semiconductor substrate 10, can be, for example, 3% to 50%, and preferably 5% to 30%, which allows sufficient light to pass through the solar cell 1 and enables relatively large electric power to be obtained.

[0027] The average diameter (equivalent circle diameter) of the light-transmitting opening 11 can be, for example, 1 mm to 10 mm, preferably 2 mm to 8 mm, which allows sufficient light to be let in while increasing the photoelectric conversion efficiency of the solar cell 1.

[0028] The inner peripheral surface of the light-transmitting opening 11 has a first peripheral surface portion 12 located on the side of the first semiconductor layer 20, and a second peripheral surface portion 13 located on the side of the second semiconductor layer 30 and having a surface texture different from that of the first peripheral surface portion 12. Note that the "surface texture" includes fine irregularities, the surface layer structure, and the altered state of the material of the semiconductor substrate 10, such as oxidation.

[0029] In this embodiment, the first peripheral surface portion 12 of the light-transmitting opening 11 is, for example, a laser-processed surface, and may have an oxide or the like on the inner peripheral surface of the semiconductor substrate 10. In addition, in the first peripheral surface portion 12, the semiconductor substrate 10 is covered with the first passivation layer 40 and the first semiconductor layer 20. On the other hand, in the second peripheral surface portion 13, the semiconductor substrate 10 is exposed.

[0030] Because the semiconductor substrate 10 is covered by the first passivation layer 40 and the first semiconductor layer 20, the first peripheral surface portion 12 suppresses recombination of carriers generated inside the semiconductor substrate 10, thereby improving the photoelectric conversion efficiency of the solar cell 1. Furthermore, because the light-transmitting opening 11 has the second peripheral surface portion 13 that exposes the semiconductor substrate 10, it is possible to reliably insulate the first semiconductor layer 20 from the second semiconductor layer 30. In other words, because the inner peripheral surface of the light-transmitting opening 11 has the first peripheral surface portion 12 that suppresses carrier recombination and the second peripheral surface portion 13 that prevents short circuits, the solar cell 1 has high photoelectric conversion efficiency.

[0031] The lower limit of the area ratio of the first circumferential surface portion 12 on the inner circumferential surface of the light-transmitting opening 11 is preferably 50%, more preferably 60%. On the other hand, the upper limit of the area ratio of the first circumferential surface portion 12 on the inner circumferential surface of the light-transmitting opening 11 is preferably 95%, more preferably 90%. By setting the area ratio of the first circumferential surface portion 12 on the inner circumferential surface of the light-transmitting opening 11 to be equal to or greater than the lower limit, the effect of suppressing carrier recombination can be increased. Furthermore, by setting the area ratio of the first circumferential surface portion 12 on the inner circumferential surface of the light-transmitting opening 11 to be equal to or less than the upper limit, no particular processing precision is required to reliably prevent short circuits.

[0032] The first semiconductor layer 20 and the second semiconductor layer 30 collect charges of opposite polarities by attracting carriers of opposite polarities from inside the semiconductor substrate 10. Specifically, when the semiconductor substrate 10 is n-type, the first semiconductor layer 20 may be formed from a p-type semiconductor, and the second semiconductor layer 30 may be formed from an n-type semiconductor.

[0033] The first semiconductor layer 20 and the second semiconductor layer 30 can be formed of, for example, an amorphous silicon material containing a dopant that imparts a desired conductivity type. An example of a p-type dopant is boron (B), and an example of an n-type dopant is phosphorus (P), as described above.

[0034] The first semiconductor layer 20 extends on the inner circumferential surface of the light-transmitting opening 11 and covers the inner circumferential surface of the semiconductor substrate 10 at the first circumferential surface portion 12 .

[0035] The first passivation layer 40 and the second passivation layer 50 improve the photoelectric conversion efficiency of the solar cell 1 by suppressing recombination on the surface of the semiconductor substrate 10 of carriers generated inside the semiconductor substrate 10. The first passivation layer 40 and the second passivation layer 50 can be intrinsic semiconductor layers made of amorphous silicon.

[0036] The first passivation layer 40 extends along the inner circumferential surface of the light-transmitting opening 11 and covers the inner circumferential surface of the semiconductor substrate 10 at the first circumferential surface portion 12 .

[0037] The first electrode 60 and the second electrode 70 extract, as electric charges, carriers attracted by the first semiconductor layer 20 and the second semiconductor layer 30. The first electrode 60 and the second electrode 70 are formed from a conductive material, and are preferably mainly made of a metal with low electrical resistance. As a specific example, the first electrode 60 and the second electrode 70 can be formed from a metal, silver paste, or the like.

[0038] The first electrode 60 on the light-receiving surface side is preferably formed in the shape of multiple lines to reduce the area so that light can be incident on the semiconductor substrate 10. The first electrode 60 may also be formed in a mesh shape to reduce the area where the carrier travels a long distance. On the other hand, the second electrode 70 may be formed in the same shape as the first electrode 60, but may be provided on substantially the entire area except for the light-transmitting opening 11 to reduce the carrier travel distance to the second electrode 70 and the electrical resistance within the second electrode 70.

[0039] As described above, the solar cell 1 can achieve high photoelectric conversion efficiency by having the inner surface of the light-transmitting opening 11 have a first peripheral surface portion 12 that suppresses carrier recombination and a second peripheral surface portion 13 that prevents short circuits.

[0040] The solar cell 1 can be manufactured by one embodiment of a solar cell manufacturing method according to the present invention. As shown in Figure 3, the solar cell manufacturing method of this embodiment includes an annular groove forming step (step S1), a passivation layer forming step (step S2), a first semiconductor layer forming step (step S3), a second semiconductor layer forming step (step S4), a first electrode forming step (step S5), a second electrode forming step (step S6), and a light-transmitting opening forming step (step S7).

[0041] In the annular groove forming process of step S1, laser light is irradiated onto one surface of the semiconductor substrate 10 to form an annular groove G corresponding to the outer diameter of the light-transmitting opening 11, as shown in FIG. 4 . Ultimately, the outer inner peripheral surface of the annular groove G becomes the first peripheral surface portion 12. Therefore, the planar shape of the annular groove G is an endless loop corresponding to the outer shape of the light-transmitting opening 11, and is not limited to a circle. The depth of the annular groove G is determined according to the height of the first peripheral surface portion 12. Films are formed on the inner surface of the annular groove G in the passivation layer forming process and the first semiconductor layer forming process. Therefore, the width of the annular groove G is set to a width that allows film formation gas to be supplied to the deepest part of the annular groove G.

[0042] 5, in the passivation layer deposition process of step S2, materials for forming the first passivation layer 40 and the second passivation layer 50 are deposited on both sides of the semiconductor substrate 10 and the inner surface of the annular groove G. The first passivation layer 40 and the second passivation layer 50 can be formed by a deposition technique such as CVD or PVD. This passivation layer deposition process may be performed in two stages, one on each side of the semiconductor substrate 10.

[0043] 6, in the first semiconductor layer deposition process of step S3, a material for forming the first semiconductor layer 20 is deposited on the light-receiving main surface of the semiconductor substrate 10 and on the surface of the first passivation layer 40 on the inner surface of the annular groove G. Like the first passivation layer 40 and the second passivation layer 50, the first semiconductor layer 20 can also be formed by a deposition technique such as CVD or PVD.

[0044] 7, in the second semiconductor layer deposition process of step S4, a material for forming the second semiconductor layer 30 is deposited on the surface of the second passivation layer 50 on the main surface opposite the light-receiving surface of the semiconductor substrate 10. The second semiconductor layer 30 can also be formed by a deposition technique such as CVD or PVD.

[0045] In the first electrode formation process of step S5, as shown in FIG. 8, the first electrode 60 is formed by, for example, printing and baking a conductive paste, laminating a metal layer, and etching the metal layer using a resist pattern.

[0046] 9, in the second electrode formation process of step S6, the second electrode 70 is formed by a method such as printing and firing a conductive paste, laminating a metal layer, and etching the metal layer using a resist pattern. The firing or etching in the second electrode formation process may be performed simultaneously with the firing or etching in the first electrode formation process.

[0047] In this way, by forming a film on the semiconductor substrate 10 in which the annular groove G is formed, an intermediate product is obtained in which the semiconductor substrate 10, the first semiconductor layer 20, the second semiconductor layer 30, the first passivation layer 40, and the second passivation layer 50 are present even in the part that will become the light-transmitting opening 11 of the solar cell 1 (the annular groove G and its interior), as shown in Figures 9 and 10.

[0048] In the light-transmitting opening forming step S7, the bottom of the annular groove G is etched or fractured to separate the region inside the annular groove G of the semiconductor substrate 10, thereby forming the light-transmitting opening 11. This results in the solar cell 1 shown in FIG.

[0049] When etching the bottom of the annular groove G, the area inside the annular groove G can be separated by forming a resist pattern that covers the entire surface of the first semiconductor layer 20 and a resist pattern that opens at least the portion of the area of ​​the second semiconductor layer 30 where the translucent opening 11 is formed, the portion corresponding to the annular groove G.

[0050] When the bottom of the annular groove G is fractured, a jig having a protrusion is pressed against the portion corresponding to the inside of the annular groove G, whereby the region inside the annular groove G can be separated.

[0051] In this way, by forming light-transmitting opening 11 in two separate steps, the annular groove forming step and the light-transmitting opening forming step, light-transmitting opening 11 has first circumferential surface portion 12 and second circumferential surface portion 13 with different surface properties. In particular, by including a step of forming a film on semiconductor substrate 10 between the annular groove forming step and the light-transmitting opening forming step, first circumferential surface portion 12 that suppresses carrier recombination and second circumferential surface portion 13 that prevents short circuits can be reliably formed, making it relatively easy to manufacture solar cell 1 with high photoelectric conversion efficiency.

[0052] Second Embodiment Fig. 11 is a schematic plan view of a solar cell 101 according to a first embodiment of the present invention. Fig. 12 is a schematic cross-sectional view of the solar cell 101. The solar cell 101 includes a plate-shaped photoelectric converter 110, a front surface electrode 120 laminated on the front surface of the photoelectric converter 110, and a back surface electrode 130 laminated on the back surface of the photoelectric converter 110. In this specification, the surface on which light is incident when the solar cell 101 is in use is referred to as the front surface, and the opposite side is referred to as the back surface.

[0053] The photoelectric converter 110 has a semiconductor substrate 111, a first semiconductor layer 112 stacked on the front surface of the semiconductor substrate 111, and a second semiconductor layer 113 stacked on the back surface of the semiconductor substrate 111. Although not shown, the photoelectric converter 110 may have further components such as a passivation layer and an anti-reflection layer. The photoelectric converter 110 also has a plurality of light-transmitting openings 114 penetrating from the front to the back.

[0054] The semiconductor substrate 111 functions as a photoelectric conversion substrate that absorbs incident light from the light-receiving surface side and generates photocarriers (electrons and holes). The semiconductor substrate 111 may have a pyramidal fine uneven structure called a texture structure in order to improve the incidence of light on its surface.

[0055] The semiconductor substrate 111 can be formed of a crystalline silicon material such as single crystal silicon or polycrystalline silicon. It may also be formed of other semiconductor materials such as gallium arsenide (GaAs). The semiconductor substrate 111 can be, for example, an n-type semiconductor substrate in which a crystalline silicon material is doped with an n-type dopant. An example of an n-type dopant is phosphorus (P). By using crystalline silicon as the material for the semiconductor substrate 111, dark current is relatively small, and a relatively high output (stable output regardless of illuminance) can be obtained even when the intensity of incident light is low.

[0056] The first semiconductor layer 112 and the second semiconductor layer 113 collect charges of opposite polarities by attracting carriers of opposite polarities from inside the semiconductor substrate 111. Specifically, when the semiconductor substrate 111 is n-type, the first semiconductor layer 112 may be formed from a p-type semiconductor, and the second semiconductor layer 113 may be formed from an n-type semiconductor.

[0057] The first semiconductor layer 112 and the second semiconductor layer 113 can be formed of, for example, an amorphous silicon material containing a dopant that imparts a desired conductivity type. An example of a p-type dopant is boron (B), and an example of an n-type dopant is the aforementioned phosphorus (P). The first semiconductor layer 112 and the second semiconductor layer 113 can each be stacked on the semiconductor substrate 111 by a film formation technique such as CVD or PVD.

[0058] The light-transmitting opening 114 allows light to pass through and reach the back side of the solar cell 101. The light-transmitting opening 114 can be formed by any method, such as laser processing or etching. The shape of the light-transmitting opening 114 in a plan view, i.e., its cross-sectional shape, is typically circular, but it can be any shape, such as an ellipse or a polygon.

[0059] The light-transmitting openings 114 are preferably formed dispersedly over substantially the entire photoelectric conversion body 110, but the strength of the photoelectric conversion body 110 may be ensured by, for example, not providing light-transmitting openings 114 in the peripheral portion of the photoelectric conversion body 110 or in a strip-shaped region that crosses the photoelectric conversion body 110. The light-transmitting openings 114 are preferably arranged regularly to allow for uniform lighting and to improve the aesthetic appearance. In the example shown in the figure, the multiple light-transmitting openings 114 are arranged in a hexagonal pattern so that six light-transmitting openings 114 are adjacent to one light-transmitting opening 114 at equal intervals and distances in the circumferential direction, but the light-transmitting openings 114 may also be formed in a square pattern in which the light-transmitting openings 114 are lined up vertically and horizontally, for example.

[0060] The area ratio of the light-transmitting openings 114 in the photoelectric converter 110, i.e., the aperture ratio of the photoelectric converter 110, can be, for example, 3% to 50%, and preferably 5% to 30%, which allows sufficient light to pass through the solar cell 101 and enables relatively large electric power to be obtained.

[0061] The average diameter (equivalent circle diameter) of the light-transmitting opening 114 can be, for example, 1 mm or more and 10 mm or less, and preferably 2 mm or more and 8 mm or less. This allows sufficient light to be let in while increasing the photoelectric conversion efficiency in the area of ​​the solar cell 101 other than the light-transmitting opening 114.

[0062] The surface electrode 120 extracts carriers attracted by the first semiconductor layer 112 as charges. The surface electrode 120 is formed from a conductive material, and is preferably formed from a metal with low electrical resistance. Specifically, the surface electrode 120 can be formed by etching a metal layer laminated on the photoelectric converter 110, printing a conductive paste such as silver paste on the photoelectric converter 110, and baking the paste. The surface electrode 120 may also have a multilayer structure.

[0063] The surface electrode 120 preferably has a small area so that light can be incident on the photoelectric converter 110, but is preferably provided over the entire photoelectric converter 110 in order to improve photoelectric conversion efficiency by reducing the travel distance of carriers within the photoelectric converter 110. For this reason, the surface electrode 120 is preferably formed in a mesh pattern over the entire surface of the photoelectric converter 110.

[0064] The surface electrode 120 has a plurality of surrounding portions 121 (hexagonal portions surrounded by two-chain lines) that individually surround a plurality of light-transmitting openings 114. In the surface electrode 120, the plurality of surrounding portions 121 are connected to one another. For this reason, the surface electrode 120 may have a connection portion that connects the plurality of surrounding portions 121, or the surrounding portions 121 may be formed so that they contact each other at corners as shown in the figure, or adjacent surrounding portions 121 may share a portion thereof.

[0065] The surface electrode 120 has a plurality of surrounding portions 121 that individually surround the light-transmitting openings 114 and are connected to each other, and is not divided by the light-transmitting openings 114, so that charges can be collected from the entire photoelectric conversion body 110.

[0066] The surrounding portion 121 is preferably formed from electrode wires 122 having a substantially constant width in order to reduce the area and electrical resistance.

[0067] The surrounding portion 121 is preferably polygonal so that the pattern of the surface electrode 120 can be simplified and arranged efficiently. Furthermore, in order to equalize the current flowing through the surface electrode 120, it is more preferable that the length of each side of the surrounding portion 121 is constant, that is, the surrounding portion 121 is polygonal with all sides of equal length. In particular, when the light-transmitting opening 114 is circular, forming the surrounding portion 121 into a regular polygonal shape can effectively suppress variations in the movement distance of carriers and prevent bias in the current flowing through the surface electrode 120.

[0068] It is preferable that each side of the surrounding portion 121 be arranged so that the distance (shortest distance) from the light-transmitting opening 114 is approximately equal. Specifically, it is preferable that the minimum value of the distance from the light-transmitting opening 114 to each side of the surrounding portion 121 is 50% or more of the maximum value, and more preferably 55% or more. This makes it possible to prevent the movement distance of the carrier from becoming locally large. By making the center of gravity of the surrounding portion 121 approximately coincident with the center of gravity of the light-transmitting opening 114, it is possible to equalize the distance from the light-transmitting opening 114 to each side of the surrounding portion 121.

[0069] The surface electrode 120 of this embodiment is composed of a plurality of electrode wires 122 arranged parallel to one another at equal intervals, and has three sets of electrode wire groups 123, 124, and 125 that intersect at different angles. By configuring the surface electrode 120 using three sets of electrode wire groups 123, 124, and 125 in this way, the pattern of the surface electrode 120 can be simplified. Furthermore, by configuring the surface electrode 120 using a plurality of electrode wires 122 that extend linearly, the effective length of the electrical path can be made relatively short. By reducing the width of such electrode wires 122, the area through which light enters the photoelectric converter 110 can be increased.

[0070] In particular, in this embodiment, the angles of the electrode wire groups 123, 124, and 125 are varied every 60°, and the intersection positions of the three sets of electrode wire groups 123, 124, and 125 are shifted evenly so as not to intersect at a single point, thereby forming a regular hexagonal surrounding portion 121. That is, in the surface electrode 120 of this embodiment, the surrounding portions 121 are regular hexagonal in shape, with their vertices touching each other, and triangular residual spaces not including the light-transmitting openings 114 are defined between the multiple surrounding portions 121. The surface electrode 120 having such a configuration does not form a region where the carrier travel distance is long, and therefore the photoelectric conversion efficiency per effective area (area excluding the light-transmitting openings 114) of the photoelectric converter 110 can be improved.

[0071] The total area inside the multiple surrounding portions 121 is preferably 2.0 to 5.0 times, and more preferably 2.5 to 4.0 times, the total area of ​​the remaining space outside the multiple surrounding portions. This makes it easy to reduce the maximum movement distance of carriers, and therefore easy to improve the photoelectric conversion efficiency of the solar cell 101.

[0072] The distance between each side of the surrounding portion 121 and the light-transmitting opening 114 is preferably 20% to 150% of the diameter of the light-transmitting opening 114, and more preferably 30% to 125%. This ensures good light transmission while improving the photoelectric conversion efficiency of the solar cell 101.

[0073] The area of ​​the front surface electrode 120 in plan view is preferably 1% to 50% of the area of ​​the semiconductor substrate 111 excluding the light-transmitting opening 114, and more preferably 2% to 40%. This ensures that the area of ​​the semiconductor substrate 111 that contributes to photoelectric conversion can be sufficiently secured while efficiently collecting carriers.

[0074] The back electrode 130 extracts, as charges, the carriers attracted by the second semiconductor layer 113. The back electrode 130 can be formed from the same material as the front electrode 120. Like the front electrode 120, the back electrode 130 may be formed in a mesh shape having a plurality of surrounding portions that individually surround a plurality of light-transmitting openings 114. However, since the back electrode 130 does not need to transmit light except for the light-transmitting openings 114, it may be laminated over the entire back surface of the photoelectric conversion body 110.

[0075] As described above, the solar cell 101 according to this embodiment is a see-through solar cell that can admit light to the back surface by having multiple light-transmitting openings 114. In addition, the front surface electrode 120 of the solar cell 101 has multiple surrounding portions 121 that individually surround the light-transmitting openings 114, and therefore the solar cell 101 does not have an area where the carriers travel a long distance, resulting in high photoelectric conversion efficiency.

[0076] <Third embodiment> 13 is a schematic plan view of a solar cell 101A according to a second embodiment of the present invention. In the following embodiments, the same components as those in the previously described embodiments are designated by the same reference numerals, and redundant explanations may be omitted.

[0077] The solar cell 101A comprises a plate-shaped photoelectric converter 110 having a plurality of light-transmitting openings 114 penetrating from the front to the back, a front electrode 120A stacked on the front surface of the photoelectric converter 110, and a back electrode (not shown) stacked on the back surface of the photoelectric converter 110.

[0078] The surface electrode 120A has a plurality of regular hexagonal surrounding portions 121A that individually surround the plurality of light-transmitting openings 114. Each of the surrounding portions 121A shares a side with an adjacent surrounding portion 121A. This configuration allows the surface electrode 120A to be appropriately arranged, especially when the area ratio of the light-transmitting openings 114 is increased.

[0079] The surface electrode 120A has a plurality of regular hexagonal surrounding portions 121A that individually surround the plurality of light-transmitting openings 114. Each of the surrounding portions 121A shares a side with an adjacent surrounding portion 121A. This configuration allows the surface electrode 120A to be appropriately arranged, especially when the area ratio of the light-transmitting openings 114 is increased.

[0080] <Fourth embodiment> 14 is a schematic plan view of a solar cell 101B according to a third embodiment of the present invention. The solar cell 101B includes a plate-shaped photoelectric converter 110B having a plurality of light-transmitting openings 114B that are elliptical in plan view and penetrate the solar cell 101B from the front to the back, a front electrode 120B stacked on the front surface of the photoelectric converter 110B, and a back electrode (not shown) stacked on the back surface of the photoelectric converter 110B.

[0081] The surface electrode 120B has a plurality of diamond-shaped surrounding portions 121B that individually surround a plurality of light-transmitting openings 114B. Each of the surrounding portions 121B shares a side with an adjacent surrounding portion 121B. In this way, by forming the surrounding portions 121B that surround the elliptical light-transmitting openings 114B in a diamond shape in a plan view, the maximum movement distance of carriers can be reduced.

[0082] Fifth Embodiment 15 is a schematic plan view of a solar cell 101C according to a fourth embodiment of the present invention. The solar cell 101C includes a plate-like photoelectric converter 110C having a plurality of light-transmitting openings 114C that are triangular in plan view and penetrate the solar cell 101C from the front to the back, a front electrode 120C stacked on the front surface of the photoelectric converter 110C, and a back electrode (not shown) stacked on the back surface of the photoelectric converter 110C.

[0083] The surface electrode 120B has a plurality of triangular surrounding portions 121C that individually surround the plurality of light-transmitting openings 114C. The surrounding portions 121C are connected to each other at their vertices, and triangular residual spaces that do not include the light-transmitting openings 114C are defined between the surrounding portions 121C.

[0084] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications and variations are possible. The solar cell according to the present invention may include additional components, such as an anti-reflection film. As a specific example, additional conductive layers may be provided to connect the first electrode and the first semiconductor layer, and the second electrode and the second semiconductor layer. Furthermore, the passivation layer may be omitted from the solar cell according to the present invention.

[0085] In the solar cell according to the present invention, the first and second peripheral surfaces of the light-transmitting opening may have different surface textures resulting from differences in processing steps, and therefore the semiconductor substrate may be entirely exposed at the inner peripheral surface of the light-transmitting opening.

[0086] In the solar cell according to the present invention, at least the first peripheral surface of the semiconductor substrate may be covered only with a passivation layer, in which case the passivation layer may be made of an insulating silicon oxide film, silicon nitride film, or the like.

[0087] In the above-described embodiment, the first circumferential surface portion is located on the light-receiving surface side, but in the solar cell according to the invention, the second circumferential surface portion may be located on the light-receiving surface side.

[0088] In the solar cell manufacturing method according to the present invention, the annular groove may be formed after the first semiconductor layer and the second semiconductor layer are formed. In this case, a resist material is laminated on the entire surface of the first semiconductor layer, and then the annular groove is formed by irradiating the first semiconductor layer with laser light, thereby simultaneously patterning the resist material. Furthermore, a passivation layer may be formed after the annular groove is formed or after the light-transmitting opening is formed, and an electrode penetrating the passivation layer may be formed, for example, by printing and firing a conductive paste.

[0089] Furthermore, when connecting multiple solar cells in a row, the width of the electrode wires along the outer edges adjacent to other solar cells may be increased so that these electrode wires can be used as bus bars for collecting charge from the other electrode wires and outputting it to the outside. The surface electrode may also have a separate bus bar, and one electrode wire group may be arranged to connect perpendicularly to the bus bar, with the electrode wires of this electrode wire group being thicker than the other electrode wires. This reduces the electrical resistance from the point where the surface electrode collects charge from the photoelectric converter to the bus bar, thereby improving the photoelectric conversion efficiency of the entire solar cell. [Explanation of symbols]

[0090] 1 solar cell 10. Semiconductor substrate 11 Translucent aperture 12 First circumferential part 13 Second circumferential part 20 First semiconductor layer 30 Second semiconductor layer 40 First passivation layer 50 Second passivation layer 60 1st electrode 70 2nd electrode 101, 101A, 101B, 101C solar cell 110, 110B, 110C Photoelectric converter 111 Semiconductor substrate 112 First semiconductor layer 113 Second semiconductor layer 114,14B Transparent aperture 120,120A,120B,120C surface electrode 121,121A,121B,120C Surrounding section 122 Electrode wire 123,124,125 Electrode wire group 130 Back electrode G Annular groove

Claims

1. a semiconductor substrate formed in a plate shape and having a plurality of light-transmitting openings penetrating in a thickness direction; a first semiconductor layer stacked on one main surface side of the semiconductor substrate; a second semiconductor layer stacked on the other main surface side of the semiconductor substrate; a first electrode stacked on the first semiconductor layer; a second electrode stacked on the second semiconductor layer; Equipped with an inner circumferential surface of the light-transmitting opening has a first circumferential surface portion located on the first semiconductor layer side and a second circumferential surface portion located on the second semiconductor layer side and having a surface texture different from that of the first circumferential surface portion; the semiconductor substrate is covered with the first semiconductor layer at the first peripheral surface portion; The solar cell, wherein the semiconductor substrate is exposed at the second peripheral surface portion.

2. a first semiconductor layer stacked on one main surface of the semiconductor substrate; a second semiconductor layer stacked on the other main surface of the semiconductor substrate; a first electrode stacked on the first semiconductor layer; and a second electrode stacked on the second semiconductor layer, wherein an inner circumferential surface of the light-transmitting opening has a first peripheral surface portion located on the first semiconductor layer side and a second peripheral surface portion located on the second semiconductor layer side and having a surface texture different from that of the first peripheral surface portion, and the semiconductor substrate is covered by the first semiconductor layer at the first peripheral surface portion, and the semiconductor substrate is exposed at the second peripheral surface portion, forming an annular groove corresponding to an outer diameter of the light-transmitting opening by irradiating a semiconductor substrate with laser light; forming the first semiconductor layer, the second semiconductor layer, the first electrode, and the second electrode on the semiconductor substrate after the step of forming the annular groove; forming the light-transmitting opening in the semiconductor substrate by separating an inner region of the annular groove of the semiconductor substrate by etching or fracturing a bottom portion of the annular groove after the step of forming a film on the semiconductor substrate; A solar cell manufacturing method comprising:

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