JP2007149871A - Interconnect, method of connecting interconnect, solar cell string, method of manufacturing solar cell string, and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interconnect capable of reducing the warpage of a solar battery, improving reliability after connection and reducing loss of electronic output of the interconnecter, and to provide a connection method thereof, a solar cell string, a method of manufacturing the solar cell string and a solar cell module. <P>SOLUTION: The interconnect for electrically connecting electrodes of adjacent solar cells with each other is provided with a conductive member and has connecting portions to be connected to electrodes of the solar cell on its both ends, wherein the surface of the conductive member on at least the connection portion is covered with a first solder layer, and the surface of the first solder layer is covered with a second solder layer having a melting point different from that of the first solder layer. The connection method thereof, the solar cell string including the interconnect, the method of manufacturing the solar cell string and the solar cell module including the solar cell string are also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an interconnector, an interconnector connection method, a solar cell string, a solar cell string manufacturing method, and a solar cell module.

  In recent years, a solar power generation system that generates power by converting solar energy into electric energy has been rapidly expected as a next-generation energy source particularly from the viewpoint of global environmental problems. As solar power generation systems spread rapidly, it is indispensable to reduce the manufacturing cost of solar cells. To reduce the manufacturing cost, it is very effective to increase the size and thickness of the silicon wafer as the substrate. It is.

  However, as silicon wafers become larger and thinner, the interconnector (conductive member for electrically connecting adjacent solar cells) that has been used in the past and solar cell electrodes are connected to the solar wafer. When manufacturing a battery string, in a heating process for connecting the interconnector and the electrode of the solar battery cell, thermal expansion between the silicon wafer as the substrate of the solar battery cell and copper as the conductive member of the interconnector Due to the coefficient difference, there arises a problem that the solar battery cell is greatly warped when the temperature is lowered to room temperature.

  Further, the warpage generated in the solar battery cell causes a transport error and a cell crack in the transport system of the automated module manufacturing line. Moreover, in the solar battery string in which a plurality of solar battery cells are electrically connected by an interconnector, if each solar battery cell is warped, in the resin sealing process of the solar battery string at the time of manufacturing the solar battery module, A strong force is locally applied to each solar battery cell constituting the solar battery string, causing cracks in the solar battery cell.

  In order to cope with such a problem, a method is disclosed in which an interconnector is formed by a twisted line, and this interconnector is connected at two points on both ends of an electrode of a solar battery cell (see, for example, Patent Document 1). According to this method, since the interconnector expands and contracts in the direction of turning, the expansion and contraction in the direction parallel to the surface of the substrate of the solar cell (longitudinal direction of the interconnector) is reduced, and the solar cell after connection of the interconnector Can reduce the warpage.

In addition, in order to reduce the difference in thermal expansion coefficient between the interconnector and the solar battery cell, a method using a clad material of copper and a material having a low thermal expansion coefficient for the interconnector is also known.
Japanese Patent Laid-Open No. 11-251613

  However, in the above method of forming the interconnector with a twisted line, there is a portion where the interconnector is not fixed to the electrode of the solar battery cell, so that the solar battery is subjected to the thermal cycle received by the solar battery module after completion of the solar battery module. When the resin that seals the string softens and flows, there is a possibility that the interconnector may come off from an unfixed portion or may be disconnected in some cases, so that there is a problem of lack of long-term reliability.

  Moreover, in the method of using a clad material of copper and a material having a small coefficient of thermal expansion as described above, the resistance value becomes large as compared with an interconnector made only of copper, and there is a problem of loss of electrical output in the interconnector. is there.

  The object of the present invention is to reduce the warpage of the solar battery cell after connection with the solar battery cell, to improve the reliability after connection, and to reduce the loss of electrical output in the interconnector. PROBLEM TO BE SOLVED: To provide an interconnector that can be connected, a method for connecting the interconnector, a solar cell string in which solar cells are connected using the interconnector, a method for manufacturing the solar cell string, and a solar cell module including the solar cell string It is in.

  The present invention is an interconnector for electrically connecting electrodes of adjacent solar battery cells, the interconnector includes a conductive member, and the interconnector is connected to connect to solar battery electrodes at both ends thereof. Interconnector wherein at least the surface of the conductive member in the connecting portion is covered with a first solder layer, and the surface of the first solder layer is covered with a second solder layer having a melting point different from that of the first solder layer It is. Here, in the interconnector of the present invention, the first solder layer only needs to be coated at least on the surface of the conductive member that contacts the electrode of the solar battery cell, and on the surface of the conductive member that does not contact the electrode of the solar battery cell. It may be coated or uncoated.

  In the interconnector of the present invention, the melting point of the second solder layer is preferably lower than the melting point of the first solder layer.

  In the interconnector of the present invention, the first solder layer may be made of Sn—Ag—Cu, and the second solder layer may be made of Sn—Zn—Bi.

  In the interconnector of the present invention, the first solder layer may be formed by being pressed onto the surface of the conductive member, and the second solder layer may be formed by being pressed onto the surface of the first solder layer.

  In the interconnector of the present invention, the first solder layer may be formed by dipping on the surface of the conductive member, and the second solder layer may be formed by dipping on the surface of the first solder layer.

  In addition, the present invention is a method for connecting any of the above interconnectors to an electrode of a solar battery cell, wherein the interconnector is connected to the electrode of the solar battery cell at a temperature equal to or higher than the melting point of the first solder layer. This is the connection method.

  Further, the present invention is a solar cell string in which electrodes of adjacent solar cells are electrically connected by any of the above interconnectors.

  Moreover, in the solar cell string of this invention, it is preferable that each surface of a photovoltaic cell is a square or a rectangle whose length of each side is 155 mm or more, respectively.

  Moreover, in the solar cell string of this invention, it is preferable that each thickness of a photovoltaic cell is 300 micrometers or less.

  Further, the present invention is a method for producing any one of the above-described solar cell strings, wherein at least one selected from the group consisting of a heater heating, a lamp heating and a reflow method, and an electrode of the solar cell and an interconnector It is a manufacturing method of the solar cell string which electrically connects with the connection part.

  Furthermore, the present invention includes any one of the above solar cell strings, a sealing material that seals the solar cell strings, and a pair of external terminals that extend from the solar cell string to the outside via the sealing material. A solar cell module.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to reduce the curvature of the photovoltaic cell after a connection with a photovoltaic cell, the reliability after a connection can be improved, and also the loss of the electrical output in an interconnector is also reduced. PROBLEM TO BE SOLVED: To provide an interconnector that can be connected, a method for connecting the interconnector, a solar cell string in which solar cells are connected using the interconnector, a method for manufacturing the solar cell string, and a solar cell module including the solar cell string Can do.

  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 a preferable example of the solar cell string of this invention containing the interconnector of this invention is shown. As shown in FIG. 1, the interconnector 1 of the present invention includes an electrode (not shown) on the light receiving surface side of one solar cell 9 of two adjacent solar cells 9 and the back surface of the other solar cell 9. The interconnector 1 has a connection portion 5 for electrically connecting these electrodes (not shown) of the solar battery cell 9 to each other. Yes.

  FIG. 2 shows a schematic cross-sectional view of the interconnector 1 shown in FIG. Here, the interconnector 1 includes an elongated conductive member 6, the surface of the conductive member 6 is covered with a first solder layer 7, and the surface of the first solder layer 7 is covered with a second solder layer 8. Yes.

  As shown in the schematic side view of FIG. 3, the interconnector 1 of the present invention presses the connecting portion 5 of the interconnector 1 against the electrode (not shown) of the solar battery cell 9 in the direction of the arrow shown in FIG. 3. By heating in a state, it is connected to the electrode of the solar battery cell 9.

  An example of the state after connecting the interconnector 1 of this invention to the electrode of the photovoltaic cell 9 is shown in the schematic cross-sectional view of FIG. As shown in FIG. 2, the interconnector 1 before connection is covered with a first solder layer 7 and a second solder layer 8 sequentially from the side closer to the conductive member 6. When the interconnector 1 of the present invention is connected, the second solder layer 8 having a low melting point near the solar battery cell 9 is first melted, and the second solder layer 8 in the molten state becomes the solar battery cell 9. Most of the electrodes (not shown) will be covered. Then, by raising the heating temperature to a temperature equal to or higher than the melting point of the first solder layer 7, the first solder layer 7 having a high melting point near the conductive member 6 is melted and the electrode of the solar battery cell 9 (not shown). Part). Thereafter, when the heating is stopped and the heating temperature is lowered, first, the first solder layer 7 having a high melting point is solidified first, and then the second solder layer 8 having a low melting point is solidified.

  Thus, since the interconnector 1 of the present invention is only partially connected to the electrode of the solar battery cell 9 and the interconnector 1 even when the first solder layer 7 having a high melting point is solidified, the heating temperature is low. Even if the conductive member 6 contracts as it decreases, the stress associated with the contraction of the conductive member 6 can be relieved by the molten second solder layer 8. In addition, after the interconnector 1 is connected to the electrode of the solar battery cell 9 by being cooled to a temperature below the melting point of the second solder layer 8 and solidifying the first solder layer 7 and the second solder layer 8, Even when the solar battery cell 9 is exposed to a high temperature environment and the second solder layer 8 is melted, the interconnector 1 is fixed to the electrode of the solar battery cell 9 by the first solder layer 7, so that the interconnector 1 is disconnected. Hateful.

  That is, when the interconnector and the solar battery cells that have been in a heated state at the time of connecting the conventional interconnector are cooled to room temperature, as shown in the schematic side view of FIG. Due to the difference in thermal expansion coefficient between them, the interconnector 10 contracts more greatly than the solar battery cell 9, so that a concave warpage occurs in the solar battery cell 9. At this time, a force (restoring force) for returning to the original shape is generated in the solar battery cell 9, and this restoring force exerts a tensile stress on the interconnector 10 in the direction of the arrow shown in FIG. give.

  Further, since the coefficient of thermal expansion is proportional to the temperature, the warpage of the solar battery cell 9 increases as the temperature difference between heating and cooling increases. When the configuration of the conventional interconnector 10 is configured such that only the first solder layer having a high melting point is coated on the surface of the conductive member, the heating temperature at the time of connecting the interconnector 10 and the solar battery cell 9 is increased. Therefore, the temperature difference between heating and cooling increases, and the warpage of the solar battery cell 9 increases.

  On the other hand, when the configuration of the conventional interconnector 10 is a configuration in which only the second solder layer having a low melting point is coated on the surface of the conductive member, when the solar battery cell 9 is exposed to a high temperature environment, the second state is reached. The solder layer is melted and the interconnector 10 is detached from the electrode of the solar battery cell 9.

  However, in the interconnector of the present invention, as described above, the surface of the conductive member has a structure in which the first solder layer having a high melting point and the second solder layer having a low melting point are sequentially coated. Cell warpage can be reduced, reliability is improved because it is difficult to be detached from the solar battery cell even after connection with the solar battery cell, and a cladding material made of a material having a low thermal expansion coefficient is used. Since it is not necessary, the loss of electrical output in the interconnector can also be reduced.

  In the present invention, the solar battery cell includes those formed using an elemental semiconductor such as amorphous, polycrystalline, or single crystal silicon, or a compound semiconductor such as GaAs.

  Moreover, in this invention, it is preferable that a conductive member consists of a conductor formed in strip | belt shape, such as foil shape or plate shape, for example, and it is preferable to consist of a conductor formed in plate shape especially. When the conductive member is made of a conductor formed in a plate shape, the contact area between the interconnector of the present invention and the solar battery cell is increased, and there is a tendency that stable and reliable connection can be achieved.

  In the present invention, when the conductive member has a strip shape, the width of the conductive member is 0.5 mm or more and 5.0 mm in consideration of the strength of the interconnector of the present invention and the irradiation area of sunlight on the solar battery cell. Or less, more preferably 0.5 mm or more and 3.0 mm or less, and particularly preferably about 2.5 mm.

  Further, in the present invention, when the conductive member has a strip shape, the thickness of the conductive member takes into account the electrical resistance of the interconnector of the present invention and the stress applied to the solar cells by the interconnector of the present invention due to temperature changes. It is preferably 0.05 mm or more and 0.5 mm or less, more preferably 0.05 mm or more and 0.3 mm or less, and particularly preferably about 0.2 mm.

  In the present invention, one end or both ends of the conductive member may be branched into a plurality. For example, when one of the adjacent solar cells has a plurality of electrodes on the light receiving surface side and the other has one electrode on the back surface side, an interface made of a conductive member having one end branched into a plurality of electrodes. It is preferable to use a connector from the viewpoint of reducing electrical resistance.

  In the present invention, the conductive member includes various metals or alloys, and the conductive member includes, for example, metals such as gold, silver, copper, platinum, aluminum, nickel, titanium, or alloys thereof. In particular, it is preferable to use copper as the conductive member. When copper is used as the conductive member, the cross-sectional area of the interconnector of the present invention tends to be reduced because of its high conductivity.

  In the present invention, the first solder layer and the second solder layer are sequentially coated on the surface of the conductive member. As the coating method, for example, the conductive material is conductive in the molten first solder layer having a high melting point. The first solder layer is dipped and solidified on the surface of the conductive member by passing the member, and then the conductive member coated with the first solder layer is passed through the second solder layer in a molten state having a low melting point. There is a method of dipping the second solder layer on the surface of the first solder layer and solidifying it.

  In the present invention, as another method of covering the first solder layer and the second solder layer, for example, the first solder layer is formed on the surface of the conductive member in a state where the first solder layer having a high melting point is solidified. The first solder layer is pressure-bonded to the surface of the conductive member by solidifying after being heated while being pressed to melt a part of the first solder layer, and then the second solder layer having a low melting point is solidified. A method in which the second solder layer is pressed against the surface of the first solder layer by heating while pressing the second solder layer against the surface of the first solder layer in a state to melt a part of the second solder layer Is mentioned.

  Further, the interconnector of the present invention is formed by electrically connecting the electrodes of adjacent solar battery cells by the interconnector of the present invention. Each surface of the solar battery cell constituting the interconnector of the present invention is It is preferable that each side is a square or a rectangle having a length of 155 mm or more. Moreover, it is preferable that each thickness of the photovoltaic cell which comprises the interconnector of this invention is 300 micrometers or less.

  That is, as the solar cell becomes larger and thinner, the problem of warpage of the solar cell becomes more prominent, but each side has a surface that is a square or a rectangle whose length is 155 mm or more. When solar cells or solar cells each having a thickness of 300 μm or less are used, in particular, each side has a square or rectangular surface with a length of 155 mm or more and a thickness of 300 μm or less. This is because when a solar battery cell is used, warpage that occurs during connection with the interconnector is effectively reduced, and productivity is improved.

  Further, the method of manufacturing the solar cell string of the present invention electrically connects the electrode of the solar cell and the connecting portion of the interconnector by at least one selected from the group consisting of heater heating, lamp heating, and reflow method. How to connect. According to such a manufacturing method, the electrode of the solar battery cell and the connecting portion of the interconnector are connected by any one of heater heating, lamp heating, and reflow methods, so that the entire surface of the electrode of the solar battery cell is obtained. The connecting portion of the interconnector is connected over the entire length, and the long-term reliability of the completed solar cell string is improved.

  The solar cell module of the present invention includes a pair of solar cell strings of the present invention, a sealing material that seals the solar cell string of the present invention, and a pair extending from the solar cell string of the present invention to the outside through the sealing material. It is a solar cell module provided with.

  Thus, in the solar cell module of the present invention, the environmental resistance of the solar cell string of the present invention is enhanced by sealing the solar cell string of the present invention with the sealing material. As the sealing material, for example, an ethylene-vinyl acetate copolymer can be used. The solar cell module of the present invention further includes a surface protective layer made of glass or polycarbonate on the light receiving surface side, further includes a back film made of acrylic resin on the back surface side, and further includes a frame made of aluminum around the periphery. Also good.

  Moreover, the solar cell module of the present invention can be a solar cell module of various forms such as a roof tile integrated module, a slate roof tile integrated module, or a daylighting module.

Example 1
First, a ternary alloy of Sn (tin), Ag (silver), and Cu (copper) is formed on the entire surface of a conductive member made of plate-like copper having a length of 290 mm, a width of 2 mm, and a thickness of 0.2 mm by dipping. As a first solder layer, Sn—Ag—Cu having a melting point of about 218 ° C. was coated with a thickness of 0.02 mm. Next, after solidification of the first solder layer, the melting point, which is a ternary alloy of Sn (tin), Zn (zinc), and Bi (bismuth), is about 187 ° C. over the entire surface of the first solder layer by dipping. Sn—Zn—Bi was coated as a second solder layer with a thickness of 0.02 mm. This produced the interconnector of Example 1.

  Then, the electrode of the solar battery cell having a square surface with a side length of 150 mm and a thickness of 200 μm is formed by reflowing the interconnector of Example 1 using a reflow furnace at 240 ° C. The electrode of the photovoltaic cell and the connection part of the interconnector of Example 1 were electrically connected.

  Subsequently, as shown in the schematic side view of FIG. 6, the solar cell 9 after the connection of the interconnector 1 of Example 1 is placed on the surface of the flat table 60, and the amount of warpage shown in FIG. 6 is measured. did. The result is shown in the column of warpage in Table 1.

  Further, whether the interconnector 1 was removed when the interconnector 1 was lifted upward while the interconnector 1 of Example 1 shown in FIG. 6 was heated to 200 ° C. was also evaluated. The results are shown in the evaluation column of Table 1. In addition, (circle) evaluation in the column of evaluation of Table 1 means that the interconnector 1 did not come off from the solar battery cell 9, and evaluation of x in the column of evaluation in Table 1 indicates that the interconnector 1 is a solar battery cell. It means that it was out of 9.

(Comparative Example 1)
The entire surface of the conductive member made of copper having the same shape and size as in Example 1 is formed by Sn-Ag-Cu having a melting point of about 218 ° C., which is a ternary alloy of Sn, Ag, and Cu, by dipping. Only one solder layer was coated with a thickness of 0.04 mm to produce an interconnector of Comparative Example 1.

  And about the interconnector of the comparative example 1, it carried out similarly to Example 1, and measured the amount of curvature, and evaluated disconnection of the interconnector. These results are shown in Table 1, respectively.

(Comparative Example 2)
The entire surface of the conductive member made of copper having the same shape and size as in Example 1 is formed by Sn-Zn-Bi having a melting point of about 187 ° C., which is a ternary alloy of Sn, Zn, and Bi, by dipping. Only the two solder layers were coated with a thickness of 0.04 mm to produce an interconnector of Comparative Example 2.

  And about the interconnector of the comparative example 2, it carried out similarly to Example 1, and measured the amount of curvature, and evaluated disconnection of the interconnector. These results are shown in Table 1, respectively.

  As shown in Table 1, the amount of warping when the interconnector of Comparative Example 2 in which only the second solder layer having a low melting point was coated was the smallest, and the comparative example in which only the first solder layer having a high melting point was coated. The amount of warping when connecting one interconnector was the largest, and the amount of warping when connecting the interconnector of Example 1 in which both the first solder layer and the second solder layer were coated was in the middle. .

  However, as shown in Table 1, when the interconnector of Comparative Example 2 was connected, the interconnector was disconnected in the evaluation of disconnection of the interconnector, but when the interconnector of Example 1 was connected, In the evaluation of disconnection of the interconnector, the interconnector did not disconnect.

  From the above results, when the interconnector of Example 1 in which both the first solder layer and the second solder layer are coated is connected, the amount of warpage can be reduced, and the interconnector after the interconnector is connected It was found that reliability can be improved.

(Example 2)
In FIG. 7, the typical side view of an example of the solar cell string of this invention is shown. Here, the solar cell string 51 has a configuration in which electrodes (not shown) of adjacent solar cells 9 are electrically connected by the interconnector 1 of the first embodiment. In the solar cell string 51 having such a configuration, the electrodes of the solar cells 9 are electrically connected to each other by the interconnector 1 of the first embodiment, so that the amount of warpage of the solar cells 9 is reduced. In addition, the reliability after connection of the interconnector 1 can be improved.

(Example 3)
In FIG. 8, typical sectional drawing of an example of the solar cell module of this invention is shown. Here, in the solar cell module 52, the solar cell string 51 in which the electrodes (not shown) of the adjacent solar cells 9 are electrically connected by the interconnector 1 of the first embodiment is sealed with the sealing material 53. A pair of external terminals 55 and 56 extend from the solar cell string 51 to the outside via the sealing material 53.

  Further, a surface protective layer 57 made of glass is provided on the light receiving surface side of the sealing material 53 that seals the solar cell string 51, and the back surface side of the sealing material 53 is made of acrylic resin. A back film 59 is installed. Further, a frame 61 made of aluminum is provided around these members.

  In the solar cell module 52 having such a configuration, the solar cell string 51 in which the electrodes of the solar cells 9 are electrically connected by the interconnector 1 of Example 1 is used. Since the amount of warpage of the cell 9 can be reduced, the crack of the solar battery cell 9 in the sealing process by the sealing material 53 can be reduced, and the reliability after the connection of the interconnector 1 is improved. be able to.

  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.

It is a schematic top view of a preferable example of a solar cell string including the interconnector of the present invention. It is typical sectional drawing of the interconnector shown in FIG. It is a typical side view illustrating an example of the method of electrically connecting the interconnector of this invention to the electrode of a photovoltaic cell. It is typical sectional drawing which shows an example after connecting the interconnector of this invention to the electrode of the photovoltaic cell. It is a typical side view of an example of the photovoltaic cell which the curvature produced after the connection of the interconnector. It is a typical side view illustrating the method to measure the curvature amount of the photovoltaic cell after the connection of an interconnector. It is a typical side view of an example of the solar cell string of this invention. It is typical sectional drawing of an example of the solar cell module of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,10 Interconnector, 5 connection part, 6 Conductive member, 7 1st solder layer, 8 2nd solder layer, 9 Solar cell, 51 Solar cell string, 52 Solar cell module, 53 Sealing material, 55,56 External Terminal, 57 Surface protective layer, 59 Back film, 60 units, 61 frames.

Claims (11)

  An interconnector for electrically connecting electrodes of adjacent solar battery cells, wherein the interconnector includes a conductive member, and the interconnector has connection portions for connecting to solar cell electrodes at both ends thereof. And at least the surface of the conductive member in the connection portion is covered with a first solder layer, and the surface of the first solder layer is covered with a second solder layer having a melting point different from that of the first solder layer. An interconnector characterized by that.   The interconnector according to claim 1, wherein the melting point of the second solder layer is lower than the melting point of the first solder layer.   The interconnector according to claim 1, wherein the first solder layer is made of Sn—Ag—Cu, and the second solder layer is made of Sn—Zn—Bi.   The first solder layer is formed by pressure bonding to the surface of the conductive member, and the second solder layer is formed by pressure bonding to the surface of the first solder layer. The interconnector according to any one of 1 to 3.   The first solder layer is formed by dipping on the surface of the conductive member, and the second solder layer is formed by dipping on the surface of the first solder layer. The interconnector according to any one of 1 to 3.   It is a method of connecting the interconnector in any one of Claim 1 to the electrode of a photovoltaic cell, Comprising: The said interconnector is connected to the electrode of a photovoltaic cell at the temperature more than melting | fusing point of the said 1st solder layer. A method for connecting an interconnector.   The solar cell string which the electrodes of adjacent photovoltaic cells are electrically connected by the interconnector according to any one of claims 1 to 5.   8. The solar cell string according to claim 7, wherein each surface of the solar cell has a square shape or a rectangular shape whose length of each side is 155 mm or more.   9. The solar cell string according to claim 7, wherein each of the solar cells has a thickness of 300 μm or less.   A method for producing a solar cell string according to any one of claims 7 to 9, wherein at least one selected from the group consisting of heater heating, lamp heating, and reflow method is used to connect the electrode of the solar cell and the interface. A method for manufacturing a solar cell string, wherein the connector connecting portion is electrically connected.   The solar cell string according to any one of claims 7 to 9, a sealing material that seals the solar cell string, and a pair of external terminals that extend from the solar cell string to the outside through the sealing material. A solar cell module provided.

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