JP2007173288A - Solar cell, solar cell string and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell wherein warpage caused in the solar cell constituting a solar cell string can be reduced, and to provide a solar cell string and a solar cell module. <P>SOLUTION: A first bus bar electrode on a first main plane of a semiconductor substrate, and a second bus bar electrode on a second main plane of the semiconductor substrate, are arranged at nearly symmetrical positions to each other against the semiconductor substrate; and the length of a first nonconnection section among adjoining first connection sections is larger than that of a second nonconnection section among adjoining second connection sections. In addition, the length of a second nonconnection section among adjoining second connection sections is larger than that of a first nonconnection section among adjoining first connection sections. The solar cell, solar string and solar cell module have such the structure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solar cell, a solar cell string, and a solar cell module, and more particularly to a solar cell, a solar cell string, and a solar cell module that can reduce warpage that occurs in a solar cell that constitutes the solar cell string.

  In recent years, a solar cell that directly converts solar energy into electric energy has been rapidly expected as a next-generation energy source particularly from the viewpoint of global environmental problems. There are various types of solar cells, such as those using compound semiconductors or organic materials, but the mainstream is currently using silicon crystals.

  FIG. 6 shows a schematic cross-sectional view of an example of a conventional solar cell. Here, in the solar cell, the n + layer 11 is formed on the light receiving surface of the p-type silicon substrate 10 made of single crystal silicon or polycrystalline silicon, so that the pn is formed by the p-type silicon substrate 10 and the n + layer 11. A junction is formed, and an antireflection film 12 and a silver electrode 13 are formed on the light receiving surface of the p-type silicon substrate 10, respectively. A p + layer 15 is formed on the back surface of the p-type silicon substrate 10 opposite to the light receiving surface. An aluminum electrode 14 and a silver electrode 16 are formed on the back surface of the p-type silicon substrate 10, respectively.

  FIG. 7 shows a schematic cross-sectional view of an example of a solar cell using single crystal silicon. The p-type silicon substrate 10 made of single crystal silicon has a substantially square shape with one side of 125 mm or 155 mm. First, after removing the slice damage layer remaining on the surface of the p-type silicon substrate 10 sliced by the multi-wire saw, a random texture structure is used in an alkaline solution to reduce the reflectance of the surface of the p-type silicon substrate 10. Form.

  Next, a dopant solution, which is a diffusion source for forming an antireflection film and a pn junction, is applied to the surface of the p-type silicon substrate 10 after the formation of the random texture structure with a coater rotating at a constant height, The n + layer 11 is formed on the surface of the p-type silicon substrate 10 by putting it in a diffusion furnace and performing a heat treatment at a temperature of 800 ° C. to 900 ° C. for 5 to 30 minutes to diffuse n-type impurities on the surface. Form. The surface on the formation side of the n + layer 11 formed in this way is the light receiving surface of the solar cell, and the opposite surface is the back surface of the solar cell.

  That is, an n-type region composed of the n + layer 11 and a p-type region composed of the p-type silicon substrate 10 are formed on the p-type silicon substrate 10, and a pn junction 4 is formed at the interface between the n-type region and the p-type region. Is done. Thereafter, in order to form the silver electrode 13 and the silver electrode 16 for taking out electric power, for example, a silver paste made of silver powder, glass frit, resin and organic solvent is printed by a screen printing method and then baked. That is, the above-described silver paste is printed on the light receiving surface of the p-type silicon substrate 10 in a grid shape and almost entirely on the back surface, and the silver paste printed on each surface of the p-type silicon substrate 10 is applied to the n-type region. In order to make ohmic contact with each of the p-type regions, the silver paste on the light-receiving surface and the back surface of the p-type silicon substrate 10 is fired by fire-through to form the silver electrode 13 and the silver electrode 16, respectively.

  FIGS. 8A to 8I show an example of a method for manufacturing a solar cell using polycrystalline silicon. First, as shown in FIG. 8A, a silicon ingot 17 obtained by recrystallizing a p-type silicon crystal raw material after being melted in a crucible is cut into silicon blocks 18. Next, as shown in FIG. 8B, the silicon block 18 is cut with a wire saw to obtain a p-type silicon substrate 10 made of polycrystalline silicon.

  Next, the damage layer 19 at the time of slicing the p-type silicon substrate 10 shown in FIG. 8C is removed by etching the surface of the p-type silicon substrate 10 with alkali or acid. At this time, if the etching conditions are adjusted, minute irregularities (not shown) can be formed on the surface of the p-type silicon substrate 10. Due to the unevenness, reflection of sunlight incident on the surface of the p-type silicon substrate 10 is reduced, and the conversion efficiency of the solar cell can be increased.

Subsequently, as shown in FIG. 8D, a dopant liquid 20 containing a compound containing phosphorus is applied on one main surface (hereinafter referred to as “first main surface”) of the p-type silicon substrate 10. Then, the p-type silicon substrate 10 after the application of the dopant liquid 20 is heat-treated at a temperature of 800 ° C. to 950 ° C. for 5 to 30 minutes, whereby phosphorus as an n-type dopant diffuses into the first main surface of the p-type silicon substrate 10. Then, as shown in FIG. 8E, the n + layer 11 is formed on the first main surface of the p-type silicon substrate 10. As a method for forming the n + layer 11, there is a method by vapor phase diffusion using P ₂ O ₅ or POCl ₃ besides the method of applying the dopant liquid.

  Next, after the glass layer formed on the first main surface of the p-type silicon substrate 10 at the time of phosphorus diffusion is removed by acid treatment, the first main surface of the p-type silicon substrate 10 is shown in FIG. An antireflection film 12 is formed thereon. Known methods for forming the antireflection film 12 include a method of forming a titanium oxide film using an atmospheric pressure CVD method and a method of forming a silicon nitride film using a plasma CVD method. In addition, when phosphorus is diffused by a method of applying a dopant solution, the n + layer 11 and the antireflection coating 12 are simultaneously formed by using a dopant solution that contains the material of the antireflection coating 12 in addition to phosphorus. It can also be formed. The antireflection film 12 may be formed after the silver electrode is formed.

  Then, as shown in FIG. 8G, an aluminum electrode 14 is formed on the other main surface (hereinafter referred to as “second main surface”) of the p-type silicon substrate 10 and the second of the p-type silicon substrate 10 is formed. A p + layer 15 is formed on the main surface. The aluminum electrode 14 and the p + layer 15 are formed by, for example, printing aluminum paste made of aluminum powder, glass frit, resin and organic solvent by screen printing or the like, and then heat-treating the p-type silicon substrate 10 to melt the aluminum. A p + layer 15 is formed under the aluminum-silicon alloy layer formed by alloying with silicon, and an aluminum electrode 14 is formed on the second main surface of the p-type silicon substrate 10. Further, the difference in dopant concentration between the p-type silicon substrate 10 and the p + layer 15 causes a potential difference (acts as a potential barrier) at the interface between the p-type silicon substrate 10 and the p + layer 15, and the photogenerated carriers are converted into p-type silicon The recombination in the vicinity of the second main surface of the substrate 10 is prevented. This improves both the short circuit current (Isc) and the open circuit voltage (Voc) of the solar cell.

  Thereafter, as shown in FIG. 8H, a silver electrode 16 is formed on the second main surface of the p-type silicon substrate 10. The silver electrode 16 can be obtained, for example, by heat-treating the p-type silicon substrate 10 after printing a silver paste made of silver powder, glass frit, resin and organic solvent by screen printing or the like.

  Then, as shown in FIG. 8 (i), a silver electrode 13 is formed on the first main surface of the p-type silicon substrate 10. The silver electrode 13 is a line of the silver electrode 13 in order to keep the series resistance including the contact resistance with the p-type silicon substrate 10 low and to reduce the formation area of the silver electrode 13 so as not to reduce the amount of incident sunlight. Pattern design such as width, pitch and thickness is important. As a method for forming the silver electrode 13, for example, a silver paste made of silver powder, glass frit, resin and organic solvent is printed on the surface of the antireflection film 12 by screen printing or the like, and then the p-type silicon substrate 10 is heat-treated. As a result, a fire-through method in which silver paste penetrates the antireflection film 12 and allows good electrical contact with the first main surface of the p-type silicon substrate 10 is used in the mass production line.

  As described above, a solar cell using polycrystalline silicon can be manufactured. The surface of the silver electrode 13 and the silver electrode 16 can be coated with solder by immersing the p-type silicon substrate 10 after the formation of the silver electrode 13 and the silver electrode 16 in a molten solder bath. This solder coating may be omitted depending on the process. Further, the solar cell manufactured as described above can be irradiated with simulated sunlight using a solar simulator, and the current-voltage (IV) characteristic of the solar cell can be measured to inspect the IV characteristic.

  In many cases, a plurality of solar cells are connected in series to form a solar cell string, and then the solar cell string is sealed with a sealing material to be sold and used as a solar cell module.

  9A to 9E show an example of a conventional method for manufacturing a solar cell module. First, as shown to Fig.9 (a), the interconnector 31 which is a conductive member is connected on the silver electrode of the 1st main surface of the solar cell 30. FIG.

  Next, as shown in FIG. 9B, the solar cells 30 to which the interconnectors 31 are connected are arranged in a row, and the interconnectors 31 other than the interconnectors 31 that are connected to the silver electrodes on the first main surface of the solar cells 30. The end is connected to the silver electrode on the second main surface of the other solar cell 30 to produce the solar cell string 34.

  Next, as shown in FIG. 9C, the solar cell strings 34 are arranged side by side, and the interconnector 31 protruding from both ends of the solar cell string 34 and the interconnector 31 protruding from both ends of the other solar cell string 34 Are connected in series using the wiring member 33 which is a conductive member, thereby connecting the solar cell strings to each other.

  Subsequently, as shown in FIG. 9 (d), the connected solar cell string 34 is sandwiched between EVA (ethylene vinyl acetate) films 36 as sealing materials, and then between the glass plate 35 and the back film 37. Pinch. Then, when the bubbles that have entered between the EVA films 36 are decompressed and heated, the EVA film 36 is cured and the solar cell string is sealed in the EVA. Thereby, a solar cell module is produced.

  Then, as shown in FIG.9 (e), a solar cell module is arrange | positioned in the aluminum frame 40, and the terminal box 38 provided with the cable 39 is attached to a solar cell module. The solar cell module manufactured as described above is irradiated with simulated sunlight using a solar simulator, and the current-voltage (IV) characteristics of the solar cell are measured to inspect the IV characteristics.

  In FIG. 10, the pattern of the silver electrode 13 formed on the 1st main surface of the p-type silicon substrate 10 used as the light-receiving surface of the conventional solar cell is shown. Here, the silver electrode 13 is composed of one linear first bus bar electrode 13a having a relatively large width and a plurality of relatively small linear finger electrodes 13b extending from the first bus bar electrode 13a. Has been.

  FIG. 11 shows a pattern of the aluminum electrode 14 and the silver electrode 16 formed on the second main surface of the p-type silicon substrate 10 which is the back surface of the conventional solar cell shown in FIG. Here, the aluminum electrode 14 is formed on substantially the entire second main surface of the p-type silicon substrate 10, and the silver electrode 16 is formed only on a part of the second main surface of the p-type silicon substrate 10. And the 2nd bus-bar electrode 23 is comprised from the silver electrode 16 for connecting to an interconnector, and the gap | interval 24 which consists of the aluminum electrode 14 between the silver electrodes 16 adjacent to the longitudinal direction of the silver electrode 16. FIG.

FIG. 12 shows a schematic cross-sectional view of a solar cell string in which solar cells having the light receiving surface shown in FIG. 10 and the back surface shown in FIG. 11 are connected in series. Here, the interconnector 31 fixed and connected to the first bus bar electrode 13a on the light receiving surface of the solar cell by solder or the like is fixed and connected to the silver electrode 16 on the back surface of another adjacent solar cell by solder or the like. ing. In FIG. 12, the description of the n + layer and the p + layer is omitted.
JP 2005-142282 A

As solar power generation systems rapidly spread, it is essential to reduce the manufacturing cost of solar cells. In reducing the manufacturing cost of solar cells, increasing the size and reducing the thickness of a silicon substrate, which is a semiconductor substrate, is a very effective means. However, in the cooling process after the heating process in which the solar cell electrode and the copper interconnector are fixed and connected by solder or the like when the solar cell string is formed with the increase in size and thickness of the silicon substrate, Difference in thermal expansion coefficient between the silicon substrate of the battery and the interconnector (the thermal expansion coefficient of silicon is 3.5 × 10 ⁻⁶ / K, whereas copper is 17.6 × 10 ⁻⁶ / K, which is about 5 times the difference In other words, a large internal stress is generated between the silicon substrate and the interconnector, causing a problem that the solar cell is greatly warped.

This is because, after the solar cell electrode and the interconnector are fixed in the heating step, when the solar cell electrode and the interconnector in a heated state are cooled to room temperature, the interconnector contracts more than the solar cell. A concave warp occurs in the solar cell. The warp generated in the solar cell causes a transport error and a crack in the solar cell in the transport system of the automated solar cell module production line. Further, when the solar cell constituting the solar cell string is warped, it is locally strong in each solar cell constituting the solar cell string in the sealing process by the sealing material for manufacturing the solar cell module. Force is applied, causing cracks in the solar cell.

  For example, Patent Document 1 discloses a method of providing a small cross-sectional area part whose cross-sectional area is locally reduced in an interconnector that connects adjacent solar cells. As described above, when the interconnector and solar cell that have been heated by the heating step are cooled to room temperature, a concave warp occurs in the solar cell. At that time, a force (restoring force) for returning to the original shape is generated in the solar cell, and this restoring force applies tensile stress to the interconnector. According to the method disclosed in Patent Document 1, when a tensile stress is applied to the interconnector, a small cross-sectional area portion that is relatively weak compared to other portions is stretched, and the warpage of the solar cell is reduced. However, further improvements are desired.

  Then, the objective of this invention is providing the solar cell which can reduce the curvature which arises in the solar cell which comprises a solar cell string, a solar cell string, and a solar cell module.

  In the present invention, a first bus bar electrode and a plurality of linear finger electrodes extending from the first bus bar electrode are provided on the first main surface of the semiconductor substrate, and the first main surface of the semiconductor substrate is opposite to the first main surface. A second bus bar electrode is provided on the second main surface, and a plurality of first connection portions for connecting to the interconnector and first non-connection portions not connected to the interconnector are alternately arranged on the first bus bar electrode. The second bus bar electrode is formed by alternately arranging a plurality of second connection parts for connecting to the interconnector and second non-connecting parts not connected to the interconnector. And the second bus bar electrode are disposed at positions that are substantially symmetrical with respect to the semiconductor substrate, and the length of the first non-connection portion located between the adjacent first connection portions is equal to that of the adjacent second connection portion. Longer than the length of the second non-connecting portion located in the first non-connecting portion, or the length of the second non-connecting portion located between the adjacent second connecting portions is located between the adjacent first connecting portions. It is a solar cell characterized by being longer than the length of a connection part.

  Here, in the solar cell of this invention, the 1st bus-bar electrode may have the hollow pattern part by which the periphery of the 1st non-connecting part was surrounded by the 1st bus-bar electrode.

  In the solar cell of the present invention, the width of the first bus bar electrode in the hollow pattern portion may be narrower than the width of the first bus bar electrode in the first connection portion.

  In the solar cell of the present invention, at least one of the first connection portions adjacent to the end portion of the first main surface may be disposed away from the end portion of the first main surface.

  Further, the present invention provides a solar cell string in which a plurality of the above solar cells are connected, and in the adjacent solar cells, the first connection part of one solar cell and the second connection part of the other solar cell are connected to each other. It is the solar cell string connected to the connector.

  In the solar cell string of the present invention, the interconnector may be bent at the end of the solar cell.

  In the solar cell string of the present invention, the interconnector is locally reduced in cross-sectional area of the interconnector at least at one of the location corresponding to the first non-connection portion and the location corresponding to the second non-connection portion. It is preferable to have a small cross-sectional area.

  Further, in the solar cell string of the present invention, the interconnector has a cross-sectional area of the interconnector that is locally reduced at all the locations corresponding to the first non-connecting portion and the location corresponding to the second non-connecting portion. It is preferable to have a small cross-sectional area.

  Further, the present invention provides a solar cell string in which a plurality of the above solar cells are connected, and in the adjacent solar cells, the first connection part of one solar cell and the second connection part of the other solar cell are connected to each other. It is the solar cell string connected to the connector.

  In the solar cell string of the present invention, it is preferable that the interconnector has a small cross-sectional area part in which the cross-sectional area of the interconnector is locally reduced in at least one part corresponding to the hollow pattern part.

  In the solar cell string of the present invention, it is preferable that the interconnector has a small cross-sectional area part in which the cross-sectional area of the interconnector is locally reduced at all the parts corresponding to the hollow pattern part.

  Furthermore, the present invention is a solar cell module in which any one of the above solar cell strings is sealed with a sealing material.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell which can reduce the curvature which arises in the solar cell which comprises a solar cell string, a solar cell string, and a solar cell module can be provided. Moreover, according to this invention, when connecting an interconnector to the solar cell which comprises a solar cell string, the crack and crack which generate | occur | produce in a solar cell can be reduced significantly.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

  In FIG. 1, the typical top view of an example of the light-receiving surface of the solar cell of this invention is shown. Here, on the first main surface of the p-type silicon substrate 10 serving as the light receiving surface of the solar cell of the present invention, a relatively wide linear first bus bar electrode 13a extending in the left-right direction on the paper surface, and the first bus bar. A plurality of narrow linear finger electrodes 13b extending from the electrode 13a in the vertical direction of the paper surface are provided. The first bus bar electrode 13a includes a linear first connecting portion 51 for fixing and connecting to the interconnector, and a first non-connecting portion (first gap) 7 not connected to the interconnector. The one connection portion 51 and the first non-connection portion (first gap) 7 are alternately arranged. In addition, in the first bus bar electrode 13a shown in FIG. 1, three first connection portions 51 are formed, and first non-connection portions (first gaps) are formed between the adjacent first connection portions 51. 7 is formed, and one first non-connecting portion (gap) 42 is formed at the end of the first main surface of the p-type silicon substrate 10. In the present invention, the “end portion” refers to an end portion in a direction in which the first connection portions and the first non-connection portions of the first bus bar electrode are alternately arranged. In the present invention, the “length” means a length in a direction in which the first connection portions and the first non-connection portions of the first bus bar electrode are alternately arranged, and the “width” means The length in the direction orthogonal to the direction in which the first connection portions and the first non-connection portions of the first bus bar electrodes are alternately arranged.

  Here, the first bus bar electrode 13a has a hollow pattern portion in which a first non-connection portion (first gap) 7 which is a gap between adjacent first connection portions 51 is surrounded by the first bus bar electrode 13a. is doing. The width of the first bus bar electrode 13 a in the first connection portion 51 is continuous with a constant width, but the width of the first non-connection portion (first gap) 7 is the width of the first bus bar electrode 13 a in the first connection portion 51. Since it is formed wider than the width, the width of the first bus bar electrode 13 a in the hollow pattern portion is narrower than the width of the first bus bar electrode 13 a in the first connection portion 51. The first connecting portion 51 adjacent to the left end of the first main surface of the p-type silicon substrate 10 is disposed away from the left end of the first main surface of the p-type silicon substrate 10. Has been.

  FIG. 2 shows a schematic plan view of the back surface of the solar cell shown in FIG. In the 2nd main surface of p type silicon substrate 10 used as the back of the solar cell of the present invention, silver electrode 16 as the 2nd connection part for connecting to an interconnector, and the 2nd non-connection part which is not connected to an interconnector (Second gap) 8 are alternately formed, and the second bus bar electrode 23 is formed from the silver electrode 16 and the second non-connection portion (second gap) 8. Here, the second non-connection portion (second gap) 8 is composed of the aluminum electrode 14 between the adjacent silver electrodes 16.

  Further, the silver electrode 16 as the second connection portion on the second main surface of the p-type silicon substrate 10 is mutually connected with respect to the first connection portion 51 on the first main surface of the p-type silicon substrate 10 and the p-type silicon substrate 10. The second non-connecting portion (the second non-connecting portion) is formed between the silver electrodes 16 that are formed in substantially symmetrical positions and are adjacent to each other in the longitudinal direction of the silver electrode 16 on the second main surface of the p-type silicon substrate 10. The first connection portion 51 on the first main surface of the p-type silicon substrate 10 is longer than the length of the gap 8 (that is, the shortest distance between the silver electrodes 16 adjacent in the longitudinal direction of the silver electrode 16). The length of the first non-connection part (first gap) 7 located between the first connection parts 51 adjacent in the longitudinal direction (that is, the first connection adjacent in the longitudinal direction of the first connection part 51) The shortest distance between the portions 51) is longer.

  FIG. 3 shows a schematic cross-sectional view of an example of the solar cell string of the present invention in which the solar cells of the present invention shown in FIGS. 1 and 2 are connected in series. Here, the interconnector in which the first connection part 51 of one solar cell of the solar cells adjacent to each other and the silver electrode 16 that is the second connection part of the other solar cell are each made of one conductive member by soldering or the like. 31 is fixedly connected. Further, the first non-connected portion (gap) 42, the first non-connected portion (first gap) 7 and the second non-connected portion (second gap) 8 of the solar cell are not fixed to the interconnector 31, respectively. Not connected. The interconnector 31 is bent at the end of the solar cell. In FIG. 3, the description of the n + layer and the p + layer is omitted.

  FIG. 4 shows a schematic plan view of an example of an interconnector used in the present invention. Here, the interconnector 31 has a small cross-sectional area portion 41 in which the cross-sectional area of the cross section perpendicular to the longitudinal direction of the interconnector 31 is locally reduced. Here, the interconnector 31 has at least one location corresponding to the first non-connection portion (first gap) 7 shown in FIG. 3 and a location corresponding to the second non-connection portion (second gap) 8, preferably It is preferable to connect so that the small cross-sectional area part 41 is arrange | positioned in all the places. In this case, the small cross-sectional area portion 41 having a relatively small cross-sectional area is not fixed to the solar cell, and the stress can be relieved by stretching freely. Compared with the case where a connector is used, the warpage of the solar cell constituting the solar cell string tends to be further reduced. In the solar cell string of the present invention shown in FIG. 3, each of the small cross-sectional area portions 41 of the interconnector 31 corresponds to the hollow pattern portion (first non-connection portion (first gap) 7) of the light receiving surface of the solar cell. Are arranged at any of the locations corresponding to the second non-connecting portion (second gap) 8.

  In the solar cell string of the present invention having such a configuration, the connection length between the interconnector and the first connection portion of the solar cell can be reduced as compared with the conventional solar cell string shown in FIG. Thus, when the connection length between the interconnector and the first connection portion of the solar cell is reduced, the stress due to the difference in thermal expansion coefficient between the interconnector and the p-type silicon substrate constituting the solar cell can be reduced. it can. Further, since the connecting portion between the interconnector and the solar cell is substantially symmetrical with respect to the p-type silicon substrate on the light receiving surface and the back surface of the solar cell, the difference in thermal expansion coefficient between the interconnector and the p-type silicon substrate of the solar cell. The stress generated due to is substantially equal between the light receiving surface and the back surface of the solar cell. Thereby, in the solar cell string of this invention, equal force acts on a solar cell from each of the light-receiving surface and back surface of a solar cell. Due to these effects, it is possible to reduce the warpage generated in the solar cells constituting the solar cell string.

  Furthermore, in the solar cell string of the present invention, cracks and cracks generated in the solar cell when producing the solar cell string of the present invention can be greatly reduced. Such an effect is that the length of the first non-connection portion (first gap) 7 on the light-receiving surface of the solar cell is longer than the length of the second non-connection portion (second gap) 8 on the back surface of the solar cell. It is thought that it is obtained by becoming.

  FIG. 5 shows a schematic cross-sectional view of another example of the solar cell string of the present invention. Here, in the solar cell string of the present invention shown in FIG. 5, the first non-connecting portion (first non-conductive portion) of the light-receiving surface of the solar cell is longer than the length of the second non-connecting portion (second gap) 8 on the back surface of the solar cell. The gap (7) is characterized by a shorter length. Other explanations are the same as those of the solar cell string of the present invention shown in FIG.

  Even with such a configuration, the connection length between the interconnector and the first connection part of the solar cell is reduced, and the interconnector and the solar cell are reduced as in the solar cell string of the present invention shown in FIG. Of the solar cell light receiving surface and the back surface of the solar cell are substantially symmetrical with respect to the p-type silicon substrate, so that the warpage generated in the solar cell constituting the solar cell string can be reduced and the solar cell of the present invention can be reduced. Cracks and cracks generated in the solar cell when producing the battery string can be greatly reduced.

  The solar cell module of the present invention can be obtained by sealing the solar cell string of the present invention shown in FIG. 3 and FIG. 5 with a sealing material such as EVA by a conventionally known method.

  In addition, although the other description in said embodiment is the same as the description in the column of said background art, it is not limited to the description. For example, in the present invention, a semiconductor substrate other than the p-type silicon substrate may be used, and the p-type and n-type conductivity types described in the background section above may be interchanged. In the present invention, the first connection portion and the second connection portion are not necessarily silver electrodes. In the present invention, the first non-connecting portion does not need to be a gap, and the second non-connecting portion need not be an aluminum electrode.

Example 1
A solar cell having the configuration of the light receiving surface shown in FIG. 1 and the configuration of the back surface shown in FIG. 2 was produced. The width of this solar cell was 156.5 mm, the length was 156.5 mm, and the thickness of the entire solar cell was 120 μm.

  Here, the width of the first connection portion 51 of the light receiving surface shown in FIG. 1 is 3 mm, the length is about 40 mm, and the first non-connection portion (first gap) 7 that is a gap of the hollow pattern portion. The width was 4.4 mm and the length was 9 mm. The width of the first bus bar electrode 13a surrounding the first non-connecting portion (first gap) 7 was 600 μm. The distance between the two first bus bar electrodes 13a was 74 mm. The first bus bar electrode 13a and the finger electrode 13b are made of silver.

  Further, the width of the second connection portion made of the silver electrode 16 on the back surface shown in FIG. 2 is 4 mm, the length is about 40 mm, and the second non-connection made of the aluminum electrode 14 located between the second connection portions. The width of the connecting portion (second gap) 8 was 4 mm and the length was 7 mm. The first connection portion 51 shown in FIG. 1 and the second connection portion shown in FIG. 2 are formed at positions that are substantially symmetrical with respect to the p-type silicon substrate 10, and the first non-connection portion ( The first gap 7 and the second non-connection portion (second gap) 8 shown in FIG. 2 are formed at positions that are substantially symmetrical with respect to the p-type silicon substrate 10. The length of the first non-connection portion (first gap) 7 is longer than the length of the second non-connection portion (second gap) 8.

  Then, two solar cells having the above-described configuration are prepared, and the first connector 51 on the light receiving surface of one solar cell and the second connector on the back surface of the other solar cell are respectively connected to the interconnector shown in FIG. 31 was connected to form a solar cell string of Example 1. The interconnector 31 is bent at the end of the solar cell. Moreover, the interconnector 31 was formed from copper, and the thickness was 200 micrometers. The width of the interconnector 31 was 2.5 mm.

  And while producing the solar cell string of Example 1, while cracking and the incidence rate of a crack which generate | occur | produce in a solar cell at the time of connection of an interconnector were counted, the curvature of the solar cell string of Example 1 after production was measured.

  As a result, when the solar cell string of Example 1 is manufactured, the cracks and the rate of occurrence of cracks that occur in the solar cell when the interconnector is connected are significantly reduced as compared to the case of manufacturing the solar cell string of Comparative Example 1 described later. Was.

  Moreover, the curvature of the solar cell which comprises the solar cell string of Example 1 was reduced significantly compared with the curvature of the solar cell which comprises the solar cell string of the comparative example 1 mentioned later.

(Comparative Example 1)
A solar cell string was produced in the same manner as in Example 1 except that the solar cell string having a schematic cross-sectional view shown in FIG. 13 was formed. And while producing the solar cell string, the occurrence rate of cracks and cracks generated in the solar cell when the interconnector was connected was counted, and the warpage of the solar cell string after production was measured.

  Here, in the solar cell string of Comparative Example 1, as shown in the schematic enlarged cross-sectional view of FIG. 14, the length of the first non-connection portion (first gap) 7 and the second non-connection portion (second gap). The length of 8 is equal to 7 mm.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the present invention, the stress due to the difference in thermal expansion coefficient between the interconnector and the solar cell is relieved. As a result, the warpage occurring in the solar cell constituting the solar cell string is reduced, and the interconnector and the solar cell are reduced. The reliability of connection with the battery is also improved.

  Moreover, according to this invention, since the curvature which arises in the solar cell which comprises a solar cell string is reduced, the conveyance error in the conveyance system of the production line of a solar cell module and the crack of a solar cell are also reduced.

  Furthermore, according to the present invention, cracking of the solar cell in the sealing step for manufacturing the solar cell module can also be reduced, so that the yield and productivity of the solar cell module are improved.

It is a typical top view of an example of the light-receiving surface of the solar cell of this invention. It is a typical top view of the back surface of the solar cell shown in FIG. It is typical sectional drawing of an example of the solar cell string of this invention which connected the solar cell of this invention shown in FIG. 1 and FIG. 2 in series. It is a typical top view of an example of an interconnector used for the present invention. It is typical sectional drawing of another example of the solar cell string of this invention. It is typical sectional drawing of an example of the conventional solar cell. It is typical sectional drawing of an example of the solar cell using a single crystal silicon. It is a figure for illustrating an example of the manufacturing method of the solar cell using a polycrystalline silicon. It is a figure for illustrating an example of the manufacturing method of the conventional solar cell module. It is a typical top view which shows the pattern of the silver electrode formed on the 1st main surface of the p-type silicon substrate used as the light-receiving surface of the conventional solar cell. It is a schematic plan view which shows the pattern of the aluminum electrode and silver electrode which were formed on the 2nd main surface of the p-type silicon substrate used as the back surface of the conventional solar cell shown in FIG. It is typical sectional drawing of the solar cell string which connected the solar cell which has the light-receiving surface shown in FIG. 10, and the back surface shown in FIG. 11 in series. 6 is a schematic cross-sectional view of a solar cell string of Comparative Example 1. FIG. It is a typical expanded sectional view of the solar cell string of the comparative example 1 shown in FIG.

Explanation of symbols

  4 pn junction, 7 first non-connection (first gap), 8 second non-connection (second gap), 10 p-type silicon substrate, 11 n + layer, 12 antireflection film, 13, 16 silver electrode , 13a 1st bus bar electrode, 13b finger electrode, 14 aluminum electrode, 15 p + layer, 17 silicon ingot, 18 silicon block, 20 dopant liquid, 23 second bus bar electrode, 24 gap, 30 solar cell, 31 interconnector, 33 Wiring material, 34 Solar cell string, 35 Glass plate, 36 EVA film, 37 Back film, 38 Terminal box, 39 Cable, 40 Aluminum frame, 41 Small cross-sectional area part, 42 First non-connection part (gap), 51 1st Connection part.

Claims (12)

A first bus bar electrode and a plurality of linear finger electrodes extending from the first bus bar electrode are provided on the first main surface of the semiconductor substrate,
A second bus bar electrode is provided on a second main surface opposite to the first main surface of the semiconductor substrate;
The first bus bar electrode is configured by alternately arranging a plurality of first connection portions for connection to an interconnector and first non-connection portions not connected to the interconnector,
The second bus bar electrode is configured by alternately arranging a plurality of second connection parts for connecting to the interconnector and second non-connecting parts not connected to the interconnector,
The first bus bar electrode and the second bus bar electrode are disposed at positions that are substantially symmetrical with respect to the semiconductor substrate,
The length of the first non-connection portion located between the adjacent first connection portions is longer than or adjacent to the length of the second non-connection portion located between the adjacent second connection portions. The length of the second non-connection portion located between the second connection portions is longer than the length of the first non-connection portion located between the adjacent first connection portions, Solar cell.   2. The solar cell according to claim 1, wherein the first bus bar electrode has a hollow pattern portion in which a peripheral edge of the first non-connection portion is surrounded by the first bus bar electrode.   3. The solar cell according to claim 2, wherein a width of the first bus bar electrode in the hollow pattern portion is narrower than a width of the first bus bar electrode in the first connection portion.   4. The device according to claim 1, wherein at least one of the first connection portions adjacent to the end portion of the first main surface is disposed apart from the end portion of the first main surface. 5. A solar cell according to the above.   A solar cell string in which a plurality of solar cells according to claim 1 are connected, wherein in the adjacent solar cells, the first connection portion of one of the solar cells and the second connection portion of the other solar cell. And a solar cell string connected to the interconnector.   The solar cell string according to claim 5, wherein the interconnector is bent at an end portion of the solar cell.   The interconnector has a small cross-sectional area portion in which the cross-sectional area of the interconnector is locally reduced in at least one position corresponding to the first non-connecting portion and the location corresponding to the second non-connecting portion. The solar cell string according to claim 5 or 6, characterized by comprising:   The interconnector has a small cross-sectional area portion in which the cross-sectional area of the interconnector is locally reduced at all the locations corresponding to the first non-connecting portion and the location corresponding to the second non-connecting portion. The solar cell string according to claim 5 or 6, characterized by comprising: A solar cell string in which a plurality of solar cells according to claim 2 are connected,
In the adjacent solar cells, the solar cell string in which the first connection portion of one of the solar cells and the second connection portion of the other solar cell are connected to an interconnector.   The interconnector has a small cross-sectional area part in which a cross-sectional area of the interconnector is locally reduced in at least one part corresponding to the hollow pattern part. Solar cell string.   The interconnector has a small cross-sectional area part in which the cross-sectional area of the interconnector is locally reduced at all of the parts corresponding to the hollow pattern part. Solar cell string.   A solar cell module, wherein the solar cell string according to claim 5 is sealed with a sealing material.

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