JP2007287749A - Solar cell with interconnector, solar cell string, and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell with interconnector, whose warp that occurs in a solar cell can be reduced, and to provide a solar cell string and a solar cell module. <P>SOLUTION: A bus bar electrode and a finger electrode extended from the bus bar electrode are formed on a first main face of a semiconductor substrate. In the solar cell with interconnector, an interconnector is connected to the bus bar electrode. In the solar cell with interconnector, the interconnector has a small cross section part in which a section vertical to a longitudinal direction of the interonnector becomes locally small, and the interconnector is connected to the bus bar electrode in a part except for the small cross section part of the interconnector. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solar cell with an interconnector, a solar cell string, and a solar cell module.

  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. 9 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, thereby forming a pn junction between the p-type silicon substrate 10 and the n + layer 11. An antireflection film 12 and a silver electrode 13 are respectively formed on the light receiving surface of the silicon substrate 10. 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. Here, the silver electrode 13 on the light receiving surface of the p-type silicon substrate 10 includes a bus bar electrode for connection to the interconnector and a finger electrode extending from the bus bar electrode. Moreover, the silver electrode 16 on the back surface of the p-type silicon substrate 10 serves as a back surface electrode for connection to the interconnector.

  FIGS. 10A to 10I show an example of a conventional method for manufacturing a solar cell. First, as shown in FIG. 10A, 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. 10B, the p-type silicon substrate 10 is obtained by cutting the silicon block 18 with a wire saw.

  Next, the damaged layer 19 at the time of slicing the p-type silicon substrate 10 shown in FIG. 10C 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. 10D, 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. 10E, 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. 10G, 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. 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. 10 (h), 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. 10 (i), the 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, the solar cell having the configuration shown in FIG. 9 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 and sold and used as a solar cell module.

  11A to 11E show an example of a conventional method for manufacturing a solar cell module. First, as shown in FIG. 11A, an interconnector 31 that is a conductive member is connected to the silver electrode on the first main surface of the solar cell manufactured as described above, and the solar cell with an interconnector is connected. 30 is produced.

  Next, as shown in FIG.11 (b), the other end of the interconnector 31 which has arranged the solar cells 30 with an interconnector in a line, and is connected to the silver electrode of the 1st main surface of the solar cell 30 with an interconnector. Is connected to the silver electrode on the second main surface of the solar cell 30 with another interconnector to produce a solar cell string 34.

  Next, as shown in FIG. 11C, the solar cell strings are arranged side by side, and the interconnector 31 protruding from both ends of the solar cell string and the interconnector 31 protruding from both ends of the other solar cell strings are electrically conductive. The solar cell strings are connected to each other by connecting in series using the wiring member 33 as a member.

  Subsequently, as shown in FIG. 11 (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.11 (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.
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, with the increase in size and thickness of the silicon substrate, when forming a solar cell with an interconnector, after the heating process of fixing and connecting the bus bar electrode on the light receiving surface of the solar cell and the interconnector made of copper with solder or the like In the cooling process, the difference in thermal expansion coefficient between the silicon substrate of the solar cell and the interconnector (the thermal expansion coefficient of silicon is 3.5 × 10 ⁻⁶ / K, whereas copper is 17.6 × 10 ⁻⁶ / K) There is a problem that the solar cell is warped.

  This is because, in the above heating step, after fixing the solar cell and the interconnector, when the solar cell and the interconnector in a heated state are cooled to room temperature, the interconnector contracts more than the solar cell. It is thought that the concave warpage occurred in the battery. 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. In addition, when warpage occurs in the solar cell constituting the solar cell with an interconnector, the solar cell is locally localized in the solar cell string forming step or the sealing step with a sealing material for manufacturing the solar cell module. Strong force is applied, causing the solar cell to crack.

  Therefore, 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 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 extended to form a solar cell with an interconnector. Although it is possible to reduce the warpage of the solar cell, further improvements are desired.

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

  The present invention is a solar cell with an interconnector comprising a busbar electrode and a finger electrode extending from the busbar electrode on a first main surface of a semiconductor substrate, wherein the interconnector is connected to the busbar electrode. Has a small cross-sectional area where the cross-section perpendicular to the longitudinal direction of the interconnector is locally small, and the interconnector is connected to the bus bar electrode at a place other than the small cross-sectional area of the interconnector It is a solar cell with an interconnector.

  According to another aspect of the invention, a bus bar electrode and a finger electrode extending from the bus bar electrode are provided on the first main surface of the semiconductor substrate, and the second main surface opposite to the first main surface of the semiconductor substrate is provided. In the electrode, the connecting part for connecting to the interconnector and the non-connecting part not connected to the interconnector are alternately arranged, and the solar cell with the interconnector in which the interconnector is connected to the connecting part, The interconnector is a solar cell with an interconnector in which the cross section perpendicular to the longitudinal direction of the interconnector has a small cross-sectional area that is locally small, and the small cross-sectional area is arranged in a non-connection portion. is there.

  According to another aspect of the present invention, there is provided a solar cell string in which a plurality of solar cells each including a bus bar electrode and finger electrodes extending from the bus bar electrode are connected to each other by an interconnector on a first main surface of a semiconductor substrate. The connector has a small cross-sectional area where the cross-section perpendicular to the longitudinal direction of the interconnector is locally small, and the interconnector is connected to the bus bar electrode at a place other than the small cross-sectional area of the interconnector. Is a solar cell string.

  Here, in the solar cell string of the present invention, in the electrode on the second main surface opposite to the first main surface of the semiconductor substrate of the solar cell, a connection portion for connecting to the interconnector, and the interconnector Non-connected non-connecting portions are alternately arranged, and the interconnector is connected to the connecting portion at a place other than the small cross-sectional area portion of the interconnector, and the small cross-sectional area portion is arranged in the non-connecting portion. It is preferable.

  Furthermore, this invention is a solar cell module containing said solar cell string.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell with an interconnector which can reduce the curvature which arises in a solar cell, a solar cell string, and a solar cell module can be provided.

  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.

  FIG. 1 shows a schematic plan view of a preferred example of an electrode structure on the light-receiving surface side that is the first main surface of the semiconductor substrate of the solar cell used in the present invention. As shown in FIG. 1, the silver electrode 13 on the light receiving surface of the semiconductor substrate of the solar cell has a relatively large continuous straight bus bar electrode 13a extending in the left-right direction of the paper surface and the vertical direction of the paper surface from the bus bar electrode 13a. And a plurality of linear finger electrodes 13b having a relatively small width.

  FIG. 2 shows a schematic plan view of a preferable example of the electrode structure on the back surface side which is the second main surface of the semiconductor substrate of the solar cell used in the present invention. As shown in FIG. 2, the electrode on the back surface of the semiconductor substrate of the solar cell is formed on the substantially entire back surface of the semiconductor substrate by the aluminum electrode 14, and the silver electrode 16 is formed only on a part of the back surface of the semiconductor substrate. ing.

  Here, the silver electrode 16 becomes a connection part for fixing and connecting to the interconnector, and the aluminum electrode 14 positioned between the silver electrodes 16 becomes a non-connection part 14a not connected to the interconnector. And the back electrode 60 is formed from the silver electrode 16 as a connection part, and the non-connection part 14a, and the silver electrode 16 as a connection part and the non-connection part 14a are alternately formed along the longitudinal direction of the back electrode 60. It is arranged. The second main surface of the semiconductor substrate is a main surface opposite to the first main surface of the semiconductor substrate.

  In FIG. 3, the typical top view of a preferable example of the interconnector used for this invention is shown. Here, the interconnector 31 has a plurality of small cross-sectional area portions 41 in which the cross-sectional area of the cross section perpendicular to the longitudinal direction of the interconnector 31 is locally small. In addition, a non-small cross-sectional area portion 61 having a cross-sectional area perpendicular to the longitudinal direction of the interconnector 31 larger than that of the small cross-sectional area portion 41 is located between the small cross-sectional area portions 41. In the present invention, the interconnector is a member having conductivity, and if it has a small cross-sectional area portion in which the cross-sectional area of the cross section perpendicular to the longitudinal direction is locally small, its shape The material is not particularly limited.

  In FIG. 4, the typical top view of the electrode structure of the light-receiving surface side of a preferable example of the solar cell with an interconnector of this invention is shown. As shown in FIG. 4, in the solar cell with an interconnector of the present invention, the interconnector 31 shown in FIG. 3 is fixed to the bus bar electrode 13a on the light receiving surface that is the first main surface of the semiconductor substrate of the solar cell shown in FIG. And connected. Here, the solar cell with an interconnector according to the present invention is characterized in that the interconnector 31 is connected to the bus bar electrode 13a at a place other than the small cross-sectional area 41 of the interconnector 31 (non-small cross-sectional area 61). Yes.

  In FIG. 5, the typical top view of the electrode structure of the back surface side of another preferable example of the solar cell with an interconnector of this invention is shown. As shown in FIG. 5, the solar cell with an interconnector according to the present invention has the interconnector shown in FIG. 3 on the silver electrode 16 serving as a connecting portion on the back surface that is the second main surface of the semiconductor substrate of the solar cell shown in FIG. 2. 31 is fixed and connected. Here, the solar cell with an interconnector according to the present invention is characterized in that the small cross-sectional area 41 of the interconnector 31 is disposed in the non-connecting portion 14a.

  Thus, in the solar cell with an interconnector of the present invention, the small cross-sectional area 41 having a relatively low strength compared to other parts of the interconnector 31 is not fixed and is in a free state. The warpage of the solar cell can be reduced by the small cross-sectional area portion 41 being freely deformed to relieve the stress.

  In manufacturing the solar cell with an interconnector of the present invention, the interconnector 31 and the bus bar electrode 13a or the silver electrode 16 of the solar cell may be heated to be fixed by soldering or the like. By not heating the small cross-sectional area portion 41, the small cross-sectional area portion 41 of the interconnector 31 can be made free without being fixed.

  In the above description, the structure in which the interconnector 31 is connected to either the bus bar electrode 13a on the light-receiving surface of the solar cell or the silver electrode 16 on the back surface is described. However, in the solar cell with an interconnector of the present invention, The interconnector 31 may be connected to both the bus bar electrode 13a on the light receiving surface of the solar cell and the silver electrode 16 on the back surface.

  In FIG. 6, typical sectional drawing of a preferable example of the solar cell string of this invention is shown. 7 shows a schematic plan view of the electrode structure on the light receiving surface side of the solar cell string of the present invention shown in FIG. 6, and FIG. 8 shows the back side of the solar cell string of the present invention shown in FIG. A schematic plan view of an electrode structure is shown.

  Here, in the solar cell string of the present invention, a solar cell 80 including a bus bar electrode 13a and a finger electrode extending from the bus bar electrode 13a on the first main surface of a p-type silicon substrate 10 as a semiconductor substrate. 81 is connected by an interconnector. And the interconnector 31 is connected to the bus-bar electrode 13a in places other than the small cross-sectional area 41 of the interconnector 31 (non-small cross-sectional area 61).

  Thus, in the solar cell string of this invention, since the small cross-sectional area part 41 whose intensity | strength is comparatively weak compared with the other part of the interconnector 31, it is in a free state without being fixed, The small The warpage of the solar cell can be reduced by the cross-sectional area portion 41 being freely deformed to relieve the stress.

  Further, in the solar cell string of the present invention, for example, as shown in FIG. 8, the back surface on the second main surface opposite to the first main surface of at least one of the semiconductor substrate 10 of the solar cell 80 and the solar cell 81. In the electrode 60, the silver electrode 16 as a connecting portion for connecting to the interconnector 31 and the non-connecting portion 14 a that is the aluminum electrode 14 that is not connected to the interconnector 31 are alternately arranged. The interconnector 31 is connected to the silver electrode 16 as the connecting portion at a place other than the small cross-sectional area portion 41 (non-small cross-sectional area portion 61), and the small cross-sectional area portion 41 of the interconnector 31 is disposed in the non-connecting portion 14a. Preferably it is. In this case, not only the first main surface of the semiconductor substrate 10 but also the second main surface, the small cross-sectional area 41 of the interconnector 31 is not fixed and is in a free state. When the portion 41 is freely deformed to relieve the stress, the warpage of the solar cell tends to be further reduced.

  The solar cell module of the present invention including the solar cell string of the present invention can be obtained by sealing the solar cell string of the present invention with a sealing material such as EVA by a conventionally known method.

  In the above description, the case where the small cross-sectional area portions 41 of the interconnector 31 are arranged in all the non-connecting portions 14a has been described. It is not necessary to arrange the area portion 41, and it is sufficient that the small cross-sectional area portion 41 is arranged at least at a part of the non-connecting portion 14a.

  Moreover, in this invention, at least one part of places other than the small cross-sectional area part 41 of the interconnector 31 should just be connected with the bus-bar electrode 13a and / or the silver electrode 16 of a solar cell.

  The description other than the above is the same as the description in the background art section above, but is not limited to the description. For example, in the present invention, a semiconductor substrate other than a p-type silicon substrate may be used, and p-type and n-type conductivity types may be interchanged. In the present invention, the bus bar electrode and finger electrode on the light receiving surface and the connecting portion on the back surface do not necessarily need to be silver electrodes, and the non-connecting portion does not need to be made of an aluminum electrode.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. 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.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell with an interconnector which can reduce the curvature which arises in a solar cell, a solar cell string, and a solar cell module can be provided.

It is a typical top view of a preferable example of the electrode structure by the side of the light-receiving surface used as the 1st main surface of the semiconductor substrate of the solar cell used for this invention. It is a typical top view of a preferable example of the electrode structure of the back surface side used as the 2nd main surface of the semiconductor substrate of the solar cell used for this invention. It is a typical top view of a desirable example of an interconnector used for the present invention. It is a typical top view of the electrode structure by the side of the light-receiving surface of a preferable example of the solar cell with an interconnector of this invention. It is a typical top view of the electrode structure of the back surface side of another preferable example of the solar cell with an interconnector of this invention. It is typical sectional drawing of a preferable example of the solar cell string of this invention. It is a typical top view of the electrode structure by the side of the light-receiving surface of the solar cell string of this invention shown in FIG. It is a typical top view of the electrode structure of the back surface side of the solar cell string of this invention shown in FIG. It is typical sectional drawing of an example of the conventional solar cell. It is a figure which shows an example of the manufacturing method of the conventional solar cell. It is a figure which shows an example of the manufacturing method of the conventional solar cell module.

Explanation of symbols

10 p-type silicon substrate, 11 n + layer, 12 antireflection film, 13, 16 silver electrode, 1
3a bus bar electrode, 13b finger electrode, 14 aluminum electrode, 14a non-connecting portion, 15 p + layer, 17 silicon ingot, 18 silicon block, 20 dopant solution, 30, 80, 81 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, 60 back electrode, 61 non-small cross-sectional area.

Claims (5)

On a first main surface of a semiconductor substrate, a bus bar electrode, and a finger electrode extending from the bus bar electrode, a solar cell with an interconnector, wherein an interconnector is connected to the bus bar electrode,
The interconnector has a small cross-sectional area portion in which a cross section perpendicular to the longitudinal direction of the interconnector is locally small,
The interconnector-attached solar cell, wherein the interconnector is connected to the bus bar electrode at a location other than the small cross-sectional area of the interconnector. A bus bar electrode and a finger electrode extending from the bus bar electrode are provided on the first main surface of the semiconductor substrate,
In the electrode on the second main surface opposite to the first main surface of the semiconductor substrate, connection portions for connecting to the interconnector and non-connection portions not connected to the interconnector are alternately arranged. And an interconnector-connected solar cell in which an interconnector is connected to the connecting portion,
The interconnector has a small cross-sectional area portion in which a cross section perpendicular to the longitudinal direction of the interconnector is locally small,
The solar cell with an interconnector, wherein the small cross-sectional area portion is disposed in the non-connecting portion. A solar cell string in which a plurality of solar cells including a bus bar electrode and finger electrodes extending from the bus bar electrode are connected by an interconnector on a first main surface of a semiconductor substrate,
The interconnector has a small cross-sectional area portion in which a cross section perpendicular to the longitudinal direction of the interconnector is locally small,
The solar cell string, wherein the interconnector is connected to the bus bar electrode at a place other than the small cross-sectional area portion of the interconnector. In the electrode on the second main surface opposite to the first main surface of the semiconductor substrate of the solar cell, connection portions for connecting to the interconnector and non-connecting portions not connected to the interconnector are alternately arranged. Are arranged in
The interconnector is connected to the connecting portion at a place other than the small cross-sectional area portion of the interconnector, and the small cross-sectional area portion is arranged at the non-connecting portion. The solar cell string described in 1.   The solar cell module containing the solar cell string of Claim 3 or 4.

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