Solar cell and method for producing solar cell

Abstract

Provided is a solar cell (1) that is in the form of a short strip, that comprises a first bus bar electrode (41) and a plurality of first finger electrodes (31), and that is used to form a solar cell string via shingling connection in which adjacent solar cells (1) are connected in a manner facing each other in the Z-axis direction at the position of the first bus bar electrode (41). The first bus bar electrode (41) has a first overlap part (411) that overlaps with the ends of the plurality of first finger electrodes (31) and a first non-overlap part (412) that is positioned toward the opposite direction from the direction in which the plurality of first finger electrodes (31) extend and that does not overlap with the ends of the plurality of first finger electrodes (31). The first overlap part (411) protrudes further from the cell surface than the first non-overlap part (412).

Description

Solar battery cell and method for manufacturing solar battery cell Cross-reference to Related Applications

[0001] The present application claims priority based on Japanese Patent Application No. 2025-049342, which is incorporated herein by reference.

[0002] The present invention relates to a solar battery cell having a busbar electrode and a plurality of finger electrodes, and particularly to a solar battery cell that forms a solar battery string by shingling connection in which adjacent solar battery cells are connected oppositely at the position of the busbar electrode, and a method for manufacturing the solar battery cell.

[0003] Conventionally, when modularizing double-sided electrode type solar battery cells, a shingling connection method is known that directly connects solar battery cells in series electrically and physically by overlapping parts of the solar battery cells with each other without using conductive connecting wires (for example, Japanese Unexamined Patent Application Publication No. 2019-212882). Since the solar battery module adopting this shingling connection method can mount more solar battery cells in a limited mounting area, it can increase the light-receiving area for photoelectric conversion per module installation area, and high output is expected.

[0004] Japanese Unexamined Patent Application Publication No. 2019-212882

[0005] However, in the shingling connection method, since the busbar electrodes of adjacent solar battery cells are connected to each other, the connection area is limited in terms of area, and there is room for improvement in the connection strength between the solar battery cells.

[0006] Accordingly, an object of the present invention is to provide a solar battery cell capable of increasing connection strength and a method for manufacturing the solar battery cell.

[0007] The solar cell of the present invention is a solar cell that forms a solar cell string by a single ring connection in which adjacent strip-shaped solar cell cells, each having a busbar electrode and a plurality of finger electrodes, are connected facing each other at the position of the busbar electrode, wherein the busbar electrode has an overlapping portion that overlaps the ends of the plurality of finger electrodes and a non-overlapping portion that is located in the opposite direction to the direction in which the plurality of finger electrodes extend and does not overlap the ends of the plurality of finger electrodes, and the overlapping portion protrudes from the cell surface more than the non-overlapping portion.

[0008] Furthermore, the busbar electrode is characterized by having a first busbar electrode provided at one end of the strip-shaped width direction on one of the front and back surfaces of the solar cell, and a second busbar electrode provided at the other end of the strip-shaped width direction on the other surface of the solar cell.

[0009] Furthermore, a method for manufacturing a solar cell string by connecting the solar cells facing each other at the position of the busbar electrode, characterized by performing a first step of forming the plurality of finger electrodes, and a second step of forming the busbar electrode having an overlapping portion that overlaps the ends of the plurality of finger electrodes and a non-overlapping portion that is located in the opposite direction to the direction in which the plurality of finger electrodes extend and does not overlap the ends of the plurality of finger electrodes, wherein the overlapping portion protrudes from the cell surface more than the non-overlapping portion.

[0010] Figure 1 is a schematic perspective view showing a solar cell string according to one embodiment of the present invention. Figure 2 is a longitudinal cross-sectional view of the connection portion of the solar cells. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. Figure 4a is a diagram showing the manufacturing procedure of the solar cell string. Figure 4b is a diagram showing the manufacturing procedure of the solar cell string. Figure 4c is a diagram showing the manufacturing procedure of the solar cell string. Figure 4d is a diagram showing the manufacturing procedure of the solar cell string.

[0011] Embodiments of the present invention will be described below with reference to the drawings. In the following description, "solar cell" refers to the individual plate-shaped parts that constitute a "solar string," which is a unit of a solar cell module. In the drawings, the same or corresponding parts are denoted by the same reference numerals and the description will not be repeated. Furthermore, although the following description assumes that the solar cell module is a single-sided light-receiving type, the present invention is also applicable to double-sided light-receiving types.

[0012] The solar cell 1 will be described with reference to Figures 1 to 3. Figure 1 is a schematic perspective view showing a solar cell string 100 according to one embodiment of the present invention. Figure 2 is a longitudinal cross-sectional view of the connection portion of the solar cell 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. As shown in Figure 1, the solar cell string 100 is made up of multiple solar cells 1 connected in a single ring. This single ring connection is a series connection in which multiple solar cells 1 formed in a strip shape are arranged sequentially so as to lay roofing boards, with the busbar electrodes provided on the long sides of the solar cells 1 facing each other overlapping. As shown in Figures 1 to 3, the solar cell 1 has a substrate 2, finger electrodes 3, busbar electrodes 4, and an adhesive portion 5.

[0013] The substrate 2 is, for example, a strip-shaped member. The substrate 2 is formed, for example, by thinly slicing a cylindrical silicon single crystal ingot in the transverse direction. Since the cross-sectional shape of this silicon single crystal ingot is circular, if the maximum area of ​​the cross-section is to be utilized, the substrate 2 will be octagonal in shape with chamfered corners. However, the shape of the substrate 2 is not limited to this, and may be a roughly rectangular shape such as a square or rectangle. The substrate 2 in this embodiment is made of silicon. However, it is not limited to this, and various semiconductor materials can be used. The substrate 2 also has a light-receiving surface 21 as the main surface, and a back surface 22 located on the back side of the light-receiving surface 21. For ease of understanding, transparent conductive layers and the like provided on the surfaces of the light-receiving surface 21 and the back surface 22 are omitted from the illustration. In the following description, the short side direction of the solar cell 1 is defined as the X-axis direction of the Cartesian coordinate system, the long side direction of the solar cell 1 is defined as the Y-axis direction of the Cartesian coordinate system, and the opposing direction of solar cells 1 facing each other is defined as the Z-axis direction of the Cartesian coordinate system. Furthermore, in a Cartesian coordinate system, the side closer to the origin is described as "one axial side," and the side further from the origin is described as "the other axial side."

[0014] The finger electrode 3 is a pattern electrode provided on the surface of the substrate 2. The finger electrode 3 extends substantially linearly along the X-axis direction of the substrate 2. The finger electrode 3 has a first finger electrode 31 and a second finger electrode 32.

[0015] The first finger electrode 31 is provided on the light-receiving surface 21. For example, a plurality of first finger electrodes 31 are provided. These plurality of first finger electrodes 31 are arranged at equal intervals and parallel to each other in the Y-axis direction, and each extends from one end to the other end in the X-axis direction of the substrate 2. In this embodiment, as shown in Figure 3, the first finger electrode 31 and the second finger electrode 32 are formed at the same position in the Y-axis direction, but they may be formed at offset positions.

[0016] The second finger electrodes 32 are provided on the back surface 22. For example, a plurality of second finger electrodes 32 are provided. These plurality of second finger electrodes 32 are arranged at equal intervals and parallel to each other in the Y-axis direction, and each extends from one end to the other end in the X-axis direction of the substrate 2.

[0017] The busbar electrode 4 is a pattern electrode provided on the surface of the substrate 2 such that a portion of it overlaps with the finger electrode 3. The busbar electrode 4 extends substantially in a straight line along the Y-axis direction of the substrate 2. In this embodiment, the width of the busbar electrode 4 (dimension in the X-axis direction) is greater than the width of the finger electrode 3 (dimension in the Y-axis direction).

[0018] The first busbar electrode 41 is a pattern electrode provided on the light-receiving surface 21. The first busbar electrode 41 is positioned at one end of the substrate 2 in the X-axis direction and overlaps with one end of the plurality of first finger electrodes 31 in the X-axis direction. The first busbar electrode 41 extends from one end of the substrate 2 in the Y-axis direction to the other end. The first busbar electrode 41 has a first overlapping portion 411 and a first non-overlapping portion 412.

[0019] The first overlapping portion 411 corresponds to the portion that overlaps with one end of the plurality of first finger electrodes 31. The first overlapping portion 411 is located on the other side (upper side) of the first finger electrode 31 in the Z-axis direction and on the other side of the first busbar electrode 41 in the X-axis direction. The first overlapping portion 411 protrudes further in the Z-axis direction than the first non-overlapping portion 412. Because the first busbar electrode 41 has thickness, the first overlapping portion 411 is also formed in the area where the first finger electrode 31 and the first busbar electrode 41 overlap in a plan view. The second overlapping portion 421 is similar.

[0020] The first non-overlapping portion 412 corresponds to the portion that does not overlap one end of the plurality of first finger electrodes 31. The first non-overlapping portion 412 is located on one side in the X-axis direction, which is opposite to the direction in which the plurality of first finger electrodes 31 extend. In other words, the first non-overlapping portion 412 is located on one side of the first finger electrodes 31 in the X-axis direction. Note that even the other side portion of the first busbar electrode 41 in the X-axis direction is included in the first non-overlapping portion 412 if it is the portion between adjacent first finger electrodes 31, as it does not overlap with the first finger electrodes 31.

[0021] The second busbar electrode 42 is a pattern electrode provided on the back surface 22. The second busbar electrode 42 is positioned at the other end of the substrate 2 in the X-axis direction and overlaps with the other end of the plurality of first finger electrodes 31 in the X-axis direction. The second busbar electrode 42 extends from one end to the other end of the substrate 2 in the Y-axis direction. The second busbar electrode 42 has a second overlapping portion 421 and a second non-overlapping portion 422.

[0022] The second overlapping portion 421 corresponds to the portion that overlaps with the other end of the plurality of first finger electrodes 31. The second overlapping portion 421 is located on one side (lower side) in the Z-axis direction of the second finger electrode 32 and on one side in the X-axis direction of the second busbar electrode 42. The second overlapping portion 421 protrudes more than the second non-overlapping portion 422 on one side in the Z-axis direction.

[0023] The second non-overlapping portion 422 corresponds to the portion that does not overlap with the other end of the plurality of first finger electrodes 31. The second non-overlapping portion 422 is located on the other side in the X-axis direction, which is opposite to the direction in which the plurality of first finger electrodes 31 extend. In other words, the first non-overlapping portion 412 is located on the other side in the X-axis direction of the second busbar electrode 42. Note that even if it is a portion of the second busbar electrode 42 in the X-axis direction, the portion corresponding to the space between adjacent second finger electrodes 32 is included in the first non-overlapping portion 412 because it does not overlap with the second finger electrodes 32.

[0024] The finger electrodes 3 and busbar electrodes 4 are formed by firing a conductive paste containing conductive particles, a thermosetting resin, a solvent, etc. Examples of conductive particles include silver, copper, aluminum, nickel, tin, bismuth, zinc, gallium, carbon, and mixtures thereof, while examples of thermosetting resins include epoxy resins, phenolic resins, and acrylic resins.

[0025] The adhesive portion 5 adheres the first busbar electrode 41 and the second busbar electrode 42. The adhesive portion 5 can be made of, for example, a conductive adhesive paste. Such a conductive adhesive paste is a paste-like adhesive in which conductive particles such as silver particles are dispersed in a thermosetting adhesive resin material such as epoxy resin, acrylic resin, or urethane resin.

[0026] Next, the manufacturing method of the solar cell string 100 will be described with reference to Figures 4a to 4d. Figures 4a to 4d are diagrams showing the manufacturing procedure of the solar cell string 100. The manufacturing method of the solar cell string 100 includes a substrate formation step, a first electrode formation step, a second electrode formation step, a cell division step, and a connection step.

[0027] As shown in Figure 4a, the substrate formation process is a process of preparing the substrate 2. The substrate 2 is a silicon substrate made of a semiconductor wafer (not shown) on which a silicon-based thin film and a transparent conductive layer are formed. The silicon-based thin film is formed, for example, by plasma CVD.

[0028] Following the substrate formation process, the first electrode formation process is performed. As shown in Figure 4b, the first electrode formation process involves applying conductive paste to the surface of the substrate 2 to form a plurality of finger electrodes 3. Specifically, a plurality of first finger electrodes 31 are formed on the surface that will become the light-receiving surface 21 (hereinafter sometimes simply referred to as the "light-receiving surface 21"), and a plurality of second finger electrodes 32 are formed on the surface that will become the back surface 22 (hereinafter sometimes simply referred to as the "back surface 22"). The conductive paste is applied by a printing method. For this reason, a printing plate (not shown) is used in the first electrode formation process. The printing plate is placed on the surface of the substrate 2, and conductive paste is applied to the substrate 2 through the openings in the printing plate. The printing plate is provided with a plurality of openings in shapes corresponding to the finger electrodes 3, that is, elongated openings that extend parallel to each other. The type of this printing plate is not particularly limited. The first electrode formation process corresponds to, for example, the "first process".

[0029] Following the first electrode formation step, a second electrode formation step is performed. As shown in Figure 4c, the second electrode formation step involves applying a conductive paste to the ends of a plurality of finger electrodes 3 formed on the surface of the substrate 2 to form a busbar electrode 4. Specifically, on the light-receiving surface 21, a first overlapping portion 411 is formed that overlaps with one end of the plurality of first finger electrodes 31 in the X-axis direction, and a first non-overlapping portion 412 is formed that is located on one side of the first finger electrodes 31 in the X-axis direction and does not overlap with the end of the plurality of first finger electrodes 31 in the X-axis direction. The first overlapping portion 411 protrudes to the other side in the Z-axis direction from the first non-overlapping portion 412. Furthermore, on the back surface 22, a second overlapping portion 421 is formed that overlaps the ends of the multiple second finger electrodes 32 on the other side in the X-axis direction, and a second non-overlapping portion 422 is formed that is located on the other side in the X-axis direction of the multiple second finger electrodes 32 and does not overlap the ends of the multiple second finger electrodes 32 on the other side in the X-axis direction. The second overlapping portion 421 protrudes to one side in the Z-axis direction more than the second non-overlapping portion 422. The manufacturing of the solar cell 1 is completed upon completion of the second electrode formation process. The second electrode formation process corresponds to, for example, "second step".

[0030] Following the second electrode formation process, a cell division process is performed. Strip-shaped solar cell cells 1 are cut along the busbar electrodes 4. This forms the solar cell cells 1.

[0031] Following the cell splitting process, a connection process is performed. As shown in Figure 4d, the connection process forms a solar cell string 100 by single-ring connection, where adjacent solar cells 1 are connected facing each other at the busbar electrode 4. Specifically, conductive adhesive paste 5 is applied to at least one (both in Figure 4d) of the surface of the first busbar electrode 41 of one of the adjacent solar cells 1 and the surface of the second busbar electrode 42 of the other adjacent solar cell 1, and then the first busbar electrode 41 and the second busbar electrode 42 are positioned facing each other. Although not clear from the figures, when viewed from the Y-axis direction, the end of the first finger electrode 31 on one side in the X-axis direction and the end of the second finger electrode 32 on the other side in the X-axis direction of each of the opposing solar cells 1 are separated in the X-axis direction. Also, each first finger electrode 31 is positioned between the second finger electrodes 32 in the Y-axis direction (see Figure 3). The first busbar electrode 41 and the second busbar electrode 42 are positioned opposite each other so that their Z-axis tips are in contact, and then the conductive adhesive paste 5 is cured. By repeating this process, a solar cell string 100 is formed by connecting solar cells 1 in a single ring.

[0032] As described above, according to the configuration of this embodiment, the first overlapping portion 411 protrudes more than the first non-overlapping portion 412 to the other side in the Z-axis direction, which is the opposing direction of the solar cell 1, and the second overlapping portion 421 protrudes more than the second non-overlapping portion 422 from the cell surface, that is, it protrudes to one side in the Z-axis direction, which is the opposing direction of the solar cell 1. Therefore, the first overlapping portion 411 of one of the opposing busbar electrodes 4 and the second non-overlapping portion 422 of the other can be combined and connected. By connecting them in this way, in addition to the conventional adhesion between the busbar electrodes 4, the convex first overlapping portion 411 and the concave second non-overlapping portion 422 physically interlock, allowing the solar cells 1 to be firmly connected to each other. Moreover, compared to the case where the flat surfaces of the opposing busbar electrodes 4 are in contact, the presence of irregularities increases the surface area that contributes to adhesion. Therefore, the connection strength can be increased.

[0033] The busbar electrode 4 includes a first busbar electrode 41 provided at one end in the X-axis direction corresponding to one side in the width direction of the strip-shaped light-receiving surface 21 of the solar cell 1, and a second busbar electrode 42 provided at the other end in the X-axis direction corresponding to the other side in the width direction of the strip-shaped light-receiving surface 22 of the solar cell 1. With this configuration, the first overlapping portion 411 and the first non-overlapping portion 412 of the first busbar electrode 41 of one of the adjacent solar cell 1 interlock with the second overlapping portion 421 and the second non-overlapping portion 422 of the second busbar electrode 42 of the other adjacent solar cell 1. This increases the contact area compared to a flat connection surface, improving the connection strength of all connection points of adjacent solar cell 1 that perform single-ring connection.

[0034] Furthermore, the present invention relates to a method for manufacturing a solar cell 1 to form a solar cell string 100 by connecting solar cell 1s facing each other at the position of the first busbar electrode 41, comprising: a first step of forming a plurality of first finger electrodes 31; a second step of forming a first busbar electrode 41 having a first overlapping portion 411 that overlaps the ends of the plurality of first finger electrodes 31, and a first non-overlapping portion 412 located on one side in the X-axis direction opposite to the direction in which the plurality of first finger electrodes 31 extend, and not overlapping the ends of the plurality of first finger electrodes 31, wherein the first overlapping portion 411 protrudes to the other side in the Z-axis direction than the first non-overlapping portion 412. With this configuration, the first overlapping portion 411 of one of the opposing busbar electrodes 4 and the second non-overlapping portion 422 of the other interlock, allowing the solar cell 1s to be firmly connected to each other, thus increasing the connection strength. Furthermore, since the first finger electrode 31, which has a smaller width dimension than the first busbar electrode 41, overlaps the end of the first finger electrode 31 when the solar cell 1 is connected facing each other at the position of the first busbar electrode 41, peeling of the first finger electrode 31 can be suppressed, and a decrease in work efficiency can be suppressed.

[0035] Embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit of the invention. The drawings sometimes schematically show the components in order to facilitate understanding. The number of each component shown in the drawings may differ from the actual number due to the convenience of drawing creation. Furthermore, the components shown in the above embodiments are examples and are not particularly limiting, and various modifications are possible without substantially departing from the effects of the present invention.

[0036] For example, in this embodiment, the end of the first finger electrode 31 on one side in the X-axis direction and the end of the second finger electrode 32 on the other side in the X-axis direction were arranged spaced apart in the X-axis direction as shown in Figure 4d, but the disclosure is not limited thereto. The end of the first finger electrode 31 on one side in the X-axis direction and the end of the second finger electrode 32 on the other side in the X-axis direction may be arranged to overlap in the X-axis direction. In this case, the end of the first finger electrode 31 on the other side in the Z-axis direction is configured to be located on one side in the Z-axis direction than the end of the second finger electrode 32 on one side in the Z-axis direction. Alternatively, the first finger electrode 31 may be configured to be located between the second finger electrodes 32.

[0037] Furthermore, while this embodiment discloses an example of a conductive paste for forming the finger electrode 3 and the busbar electrode 4, the disclosure is not limited thereto. At a minimum, the polymerized portion 411 (421) of the busbar electrode 4 should protrude more from the cell surface than the non-polymerized portion 412 (422), and the composition of the conductive paste for forming the finger electrode 3 and the busbar electrode 4 may be different, provided that viscosity sufficient to form irregularities is ensured.

[0038] Furthermore, although this embodiment involves forming the busbar electrode 4 after forming the finger electrode 3, the disclosure is not limited to this. The finger electrode 3 may be formed after forming the busbar electrode 4.

[0039] Furthermore, regarding the surface roughness of the electrodes, the surface roughness of the busbar electrode 4 may be made rougher than that of the finger electrode 3. This makes it easier to hold the conductive adhesive paste between the busbar electrodes 4, and further improves the adhesive strength between the solar cells 1.

[0040] The configuration and operation of the above embodiment are summarized below. The solar cell of the present invention in the above embodiment is a solar cell that forms a solar cell string by a single ring connection in which adjacent strip-shaped solar cells having a busbar electrode and a plurality of finger electrodes are connected facing each other at the position of the busbar electrode, wherein the busbar electrode has an overlapping portion that overlaps the ends of the plurality of finger electrodes and a non-overlapping portion that is located in the opposite direction to the direction in which the plurality of finger electrodes extend and does not overlap the ends of the plurality of finger electrodes, and the overlapping portion protrudes from the cell surface more than the non-overlapping portion.

[0041] According to the present invention, since the polymerized portion protrudes from the cell surface more than the non-polymerized portion, the polymerized portion of one of the opposing busbar electrodes can be combined and connected to the non-polymerized portion of the other. By connecting them in this way, the relatively convex polymerized portion and the relatively concave non-polymerized portion cause interlocking between the opposing busbar electrodes, enabling a strong connection between the solar cells. Therefore, the connection strength can be increased.

[0042] Furthermore, the busbar electrode is characterized by having a first busbar electrode provided on one end of the strip-shaped width direction of one of the front and back surfaces of the solar cell, and a second busbar electrode provided on the other end of the strip-shaped width direction of the other surface of the solar cell.

[0043] According to the above configuration, the overlapping and non-overlapping portions of the first busbar electrode interlock with the overlapping and non-overlapping portions of the second busbar electrode, thereby increasing the contact area compared to a flat connection surface and improving the connection strength of all connection points of adjacent solar cells performing single-ring connection.

[0044] Further, there is provided a method for manufacturing a solar cell that forms a solar cell string by connecting the solar cells to face each other at the positions of the bus bar electrodes, the method comprising: performing a first step of forming the plurality of finger electrodes; and a second step of forming the bus bar electrode that has an overlapping portion overlapping ends of the plurality of finger electrodes and a non-overlapping portion located in a direction opposite to an extending direction of the plurality of finger electrodes and not overlapping the ends of the plurality of finger electrodes, wherein the overlapping portion protrudes more from the cell surface than the non-overlapping portion.

[0045] According to the above configuration, the relatively convex overlapping portion and the relatively concave non-overlapping portion engage with each other to allow firm connection between the solar cells, so that the connection strength can be increased.

[0046] According to the present invention, the connection strength between solar cells can be increased.

[0047] 1...solar cell, 2...substrate, 3...finger electrode, 4...bus bar electrode, 5...adhesive portion (conductive adhesive paste), 21...light-receiving surface, 22...back surface, 31...first finger electrode, 32...second finger electrode, 100...solar cell string, 411...first overlapping portion, 412...first non-overlapping portion, 421...second overlapping portion, 422...second non-overlapping portion

Claims

1. A solar cell that forms a solar cell string by a single ring connection in which adjacent strip-shaped solar cell cells, each having a busbar electrode and a plurality of finger electrodes, are connected facing each other at the position of the busbar electrode, wherein the busbar electrode has an overlapping portion that overlaps the ends of the plurality of finger electrodes, and a non-overlapping portion that is located in the opposite direction to the direction in which the plurality of finger electrodes extend and does not overlap the ends of the plurality of finger electrodes, and the overlapping portion protrudes from the cell surface more than the non-overlapping portion.

2. The solar cell according to claim 1, wherein the busbar electrode comprises: a first busbar electrode provided on one end of the strip-shaped width direction of one of the front and back surfaces of the solar cell; and a second busbar electrode provided on the other end of the strip-shaped width direction of the other surface of the solar cell.

3. A method for manufacturing a solar cell string by connecting solar cell cells according to claim 1 or claim 2 facing each other at the position of the busbar electrode, comprising: a first step of forming a plurality of finger electrodes; and a second step of forming a busbar electrode having an overlapping portion that overlaps the ends of the plurality of finger electrodes and a non-overlapping portion located in the opposite direction to the direction in which the plurality of finger electrodes extend and not overlapping the ends of the plurality of finger electrodes, wherein the overlapping portion protrudes from the cell surface more than the non-overlapping portion.

Images