JP2006278695A - Solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell module capable of effectively correcting a warp of a solar cell element.
SOLUTION: A solar cell module in which a plurality of solar cell elements 2 sealed with fillers 8 and 9 and electrically connected by connecting tabs 3 are arranged between a translucent light receiving surface member 1 and a back surface member 7. is there. In the connection tab 3 for connecting a plurality of solar cell elements 2, the cross-sectional area of the portion connected to the light receiving surface side of one solar cell element is different from the cross-sectional area of the portion connected to the back surface side of the solar cell element. I made it.
[Selection] Figure 7

Description

  The present invention relates to a solar cell module, and more particularly to a solar cell module in which reliability and yield are improved by improving a connection tab for electrically connecting solar cell elements.

  Solar cell elements are often manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate. For this reason, the solar cell element is vulnerable to physical impact, and when the solar cell is installed outdoors, it is necessary to protect it from rain. Moreover, since the electric output generated by two solar cell elements is small, it is necessary to connect a plurality of solar cell elements 2 in series and parallel so that a practical electric output can be taken out. For this reason, a solar cell module is usually formed by connecting a plurality of solar cell elements and enclosing them with a light-transmitting light-receiving surface member and a filler mainly composed of ethylene vinyl acetate copolymer (EVA). ing. 1 and 2 show typical solar cell modules. In FIG. 1, 1 is a translucent light receiving surface member, 2 is a solar cell element, 3 is a connection tab, 4 is a module frame, and 5 is a module frame. An electrically connected solar cell string, 6 is a lateral wiring. Moreover, in FIG. 2, 7 is a back surface member, 8 is a light-receiving surface side filling member, 9 is a back surface side filling member.

  As the translucent light-receiving surface member 1, a substrate made of glass or polycarbonate resin is used. The light-receiving surface side filler 8 and the back surface side filler 9 are made of an ethylene-vinyl acetate copolymer (hereinafter, ethylene-vinyl acetate copolymer is abbreviated as EVA), and have a sheet shape with a thickness of about 0.4 to 1 mm. A form is used. These are fused and integrated with other members by applying heat and pressure under reduced pressure using a laminating apparatus. EVA may contain titanium oxide, a pigment, etc., and may be colored white. In the light-receiving surface side filler 42 according to the present invention, when it is colored, the amount of light incident on the solar cell element 43 tends to decrease and the power generation efficiency tends to decrease. Moreover, although EVA used for the back surface side filler 9 may be composed of a transparent material, in addition to this, titanium oxide, a pigment, or the like is contained in accordance with the installation environment around the solar cell module, thereby coloring it white or the like. Also good.

  The back member 9 is made of a weather-resistant fluorine-based resin sheet sandwiching an aluminum foil so as not to transmit moisture, a polyethylene terephthalate (PET) sheet deposited with alumina or silica, or the like.

  Then, the translucent light-receiving surface member 1, the light-receiving surface side filler 8, the solar cell element 2 connected to the connection tab 3, the back surface side filler 9, and the back surface member 7 are superposed and set in a device called a laminator. They are integrated by applying pressure while heating for about 15 to 60 minutes at a temperature of about 100 to 200 ° C. under a reduced pressure of about 150 Pa. A terminal box (not shown) having a cable for connecting an external circuit is attached to the back surface of the created solar cell panel portion with an adhesive or the like.

Furthermore, the module frame 4 necessary for installing the solar cell module with the required strength and the solar cell module in a building or the like is fitted into the outer periphery of the panel, thereby completing the solar cell module.

  As shown in FIGS. 3 and 4, the solar cell element 2 used in the above-described solar cell module has a bus bar electrode 21 and finger electrodes 22 formed on the light-receiving surface side of the silicon substrate 200 having a PN junction. It was. Moreover, the back surface side electrode 23 was formed in the back surface side. Reference numeral 24 denotes a high concentration impurity doped layer, for example, a P + layer.

  The solar cell element 2 is made of, for example, a single crystal or polycrystalline silicon substrate 20 having a thickness of about 0.3 to 0.4 mm and a size of about 150 mm square. Inside the silicon substrate 20 of the solar cell element 2 is formed a PN junction in which a P layer containing a large amount of P-type impurities such as boron and an N layer containing a large amount of N-type impurities such as phosphorus are in contact. Further, in order to improve the photoelectric conversion efficiency of the solar cell element 2, a highly doped layer 24 containing a high concentration of P-type impurities such as aluminum is formed on almost the entire back surface of the silicon substrate. Further, light receiving surface side electrodes 21 and 22 and a back surface side electrode 23 are formed on the light receiving surface side and the back surface side of the silicon substrate 20. The bus bar electrode 21 of the light receiving surface side electrode and the bus bar electrode 23 of the back surface side electrode are formed of silver paste by a screen printing method or the like, and the protection and connection tabs 3 are attached to the surfaces of these electrodes 21 and 23. In order to make it easier, the entire surface is solder coated.

  In such a solar cell element 2, contraction of the high-concentration P layer on the back surface side occurs, so that the solar cell element 2 warps so that the back surface side contracts and the light receiving surface side extends.

  When the high concentration doped layer 24 on the back surface side of the solar cell element is not formed, the solar cell element 2 is affected by the shrinkage of an antireflection film (not shown) formed on the light receiving surface side of the solar cell element 2. On the other hand, the light receiving surface side may contract and the back surface side may warp so as to extend.

  Moreover, in the solar cell element 2 used for the recent solar cell module, the silicon substrate 20 of the solar cell element 2 tends to become thinner for cost reduction. This warpage is larger because the vertical and horizontal dimensions tend to be larger.

  In the solar cell module, as shown in FIGS. 5 and 6, a plurality of solar cell elements 2 a, 2 b... Are electrically connected by using conductive connection tabs 30. Such a connection tab 3 is usually used by cutting a copper foil having a thickness of about 0.1 to 1.0 mm and a width of about 2 to 8 mm into a predetermined length by solder coating. In addition, in the connection tab of FIG. 6, the cross-sectional area is a uniform cross-sectional area, and in order to distinguish with this invention, the code | symbol 30 is attached | subjected.

For example, the bus bar electrode 21 on the light receiving surface side of the solar cell element 2a and the back electrode 23 of the adjacent solar cell element 2b are soldered to the connection tab 30. Specifically, the connection tab 3 is arranged on the bus bar electrode 21 on the light receiving surface side of the solar cell element 2b, and the connection tab 30 is pressed against the bus bar electrode 21 of the solar cell element 2b with a pin or the like. Both solders are melted by heating, and the bus bar electrode 21 and the connection tab 30 on the light receiving surface side of the solar cell element 2b are soldered. Thereafter, the solar electrode element 2b was inverted, and the other connection tabs 3 were soldered to the electrode 23 on the back side in the same manner. (Refer to the prior art in Patent Document 1)
Japanese Patent Laid-Open No. 11-312820

  In soldering the connection tab 30 to the solar cell element 2 as described above, the conditions (soldering temperature, time, etc.) for soldering the connection tab 30 to the bus bar electrode 21 on the light receiving surface side and the back surface side are described. Since there is a slight difference in the conditions for soldering the connection tab 30 to the electrode, for example, the bus bar electrode 23 on the back surface side, the warpage of the solar cell element 2 may be further increased before and after the connection tab 30 is soldered.

  In particular, in recent solar cell modules, the use of solder that does not substantially contain lead is increasing due to environmental considerations. When using solder that does not substantially contain lead Then, since the soldering temperature increases due to the physical properties of the solder, the degree of warping of the solar cell element 2 is often further increased before and after soldering the connection tab 30 as described above.

  Thus, in addition to the warp due to the shrinkage of the high-concentration impurity doped layer of the solar cell element 2, when the manufacturing process of the solar cell module proceeds in a state where there is a warp generated after the connection tab 30 is attached, for example, the pressure reduction during the process It is considered that cracking of the solar cell element is likely to occur due to a laminate pressed down, etc., and the yield is reduced or cracking is likely to occur, which may cause a decrease in the reliability of the completed solar cell module. .

  This invention is made in view of such a problem, The objective provides the connection tab which corrects the curvature of a solar cell element after attachment of a connection tab, and, thereby, prevents the crack in a solar cell module manufacturing process. It is to improve the reliability of the completed solar cell module.

  The present invention provides a solar cell in which a light receiving surface side of one solar cell element and a back surface side of the other solar cell element are electrically connected by a connection tab between a translucent light receiving surface member and a back surface member. In the solar cell module in which the element group is arranged, the connection tab includes a cross-sectional area of a region connected to the light receiving surface side of one solar cell element and a cross-sectional area of a region connected to the back surface side of the other solar cell element. And are different.

  The solar cell element is a PN-bonded silicon substrate, and a high-concentration impurity doped layer is provided on one main surface side, and the cross-sectional area of the connection tab connected to the one main surface side is the other. It is characterized in that the cross-sectional areas of the connection tabs connected to the main surface are comparatively thin.

A copper material is generally used as the main material of the connection tab. And the thermal expansion coefficient of this copper is 16.7 * 10 < ^-6 >, and is a thermal expansion coefficient larger than the thermal expansion coefficient 2.6 * 10 <^-6> of a silicon substrate. For this reason, when connecting the connection tab to the solar cell element by soldering, the temperature of the solar cell element and the connection tab rises to about 200 to 250 ° C., and when the temperature is cooled to room temperature after the connection tab is attached, this heat Due to the difference in expansion coefficient, warpage occurs so that the surface of the solar cell element to which the connection tab is attached shrinks.

  However, since the connection tabs are attached to both sides of the solar cell element, if the connection tabs on both sides and the soldering conditions are the same, the effects of the connection tabs on both sides cancel each other, and the warpage is the same as before the connection tab was attached. It will be a thing.

  However, for example, in a solar cell element in which the back surface side of the solar cell element is contracted and warped so that the light receiving surface side extends, the cross-sectional area of the connection tab soldered to the light receiving surface side is soldered to the back surface side. If a thicker one than the cross-sectional area is used, the force generated by the contraction of the two connection tabs after tab attachment will be greater for the connection tab soldered to the light-receiving surface side, the pre-rear surface side will shrink, and the light-receiving surface side will This warping is corrected for the state of warping to extend.

  Since the cross-sectional area of the portion connected to the light receiving surface side of the solar cell element of the connection tab and the cross-sectional area of the portion connected to the back side of the solar cell element are thus different, before attaching the connection tab When the solar cell element is warped so as to extend toward the light receiving surface side, or when the light receiving surface side is warped so as to contract, these warpages can be corrected after attaching the tab. It is possible to prevent cracking during the module manufacturing process and improve the reliability of the completed solar cell module.

  Moreover, in this connection tab, when the cross-sectional area of the portion connected to the light-receiving surface side of the solar cell element is thicker than the cross-sectional area of the portion connected to the back surface side of the solar cell element, the back surface side contracts and receives light In a high-efficiency solar cell element in which a high-concentration impurity-doped layer is formed on the back side that is warped so that the surface side extends, warping due to shrinkage of the high-concentration impurity-doped layer can be corrected by attaching a connection tab.

  Hereinafter, the solar cell module of the present invention will be described in detail with reference to the accompanying drawings.

  1-6 is a figure which shows the connection state of a typical solar cell module, the solar cell element which comprises a solar cell module, and also a solar cell element.

  FIG. 1 is a plan view of a solar cell module, FIG. 2 is a partially exploded view illustrating the structure of a panel portion of the solar cell module, FIG. 3 is a cross-sectional view of the solar cell element 2, and FIG. FIG. 5 is a plan view of a state in which, for example, two solar cell elements are connected using a connection tab, and FIG. 6 is a cross section thereof.

  In particular, the solar cell element 2 is made of a monocrystalline or polycrystalline silicon substrate 20. A light receiving surface side electrode and a back surface side electrode are formed on the light receiving surface side and the back surface side of the silicon substrate 20. On this light receiving surface side, a bus bar electrode 21 and finger electrodes 22 are respectively formed by silver paste using a screen printing method or the like. An electrode having a similar structure is also formed on the back side. Note that the back-side electrode 23 is a bus bar electrode, and the finger electrode is not related to the connection tab 3 and is therefore omitted from the detailed description and drawings.

  The surface of the bus bar electrode 21 which is the surface side electrode to which the connection tab 3 is bonded and the surface of the bus bar electrode 23 which is the back side electrode are solder coated over almost the entire surface in order to protect the connection tab 3 and make the connection tab 3 easy to attach. The

  The light receiving surface side finger electrode 22 has a width of about 0.1 to 0.2 mm and is formed in parallel with one side of the solar cell element 2 to collect photogenerated carriers. Similar finger electrodes are formed on the back surface side. Is also formed.

  The light receiving surface side bus bar electrode 21 and the back side bus bar electrode (back side electrode) 23 collect the collected carriers and have a width of about 2 mm for attaching the connection tab 3, so as to intersect the finger electrode 22 vertically. About three are formed.

  The width of the connection tab 3 is equal to or less than the width of the bus bar electrode 21 so that the connection tab 3 itself does not shade the light receiving surface of the solar cell element 2 when soldering to the solar cell element 2. Further, the length of the connection tab 3 is made to overlap almost all of the light receiving surface side bus bar electrode 21 and the back surface electrode 23. When a general 150 mm square solar cell element 2 is used, the connection tab 3 has a width of about 1 to 3 mm, a length of about 200 to 300 mm, and has a strip shape as a whole.

The reason why the connection tab 3 overlaps substantially all of the bus bar electrode 21 and the back electrode 23 on the light receiving surface side is to reduce the resistance component.

  Furthermore, the connection tab 3 according to the present invention is characterized in that the cross-sectional area of the portion connected to the light receiving surface side of the solar cell element 2 and the cross-sectional area of the portion connected to the back surface side of the solar cell element are different.

  FIG. 7 is a cross-sectional view of two solar cell elements connected using the connection tab 3 according to the present invention. As an example, the bus bar electrode 21 on the light receiving surface side of the solar cell elements 2a and 2b is connected to the bus tab electrode 21. It is in a state where the thick cross-sectional areas are connected. FIG. 8 is a cross-sectional view showing the length direction of the connection tab 3 used for connecting the solar cell elements 2 of the present invention. This connection tab 3 has a portion 31 having a thin cross-sectional area and a portion 32 having a thin cross-sectional area.

  The thin portion 32 of the connection tab 3 has a cross-sectional area of, for example, 0.1 to 0.4 mm, and the thick cross-sectional portion 31 has a cross-sectional area of, for example, 0.5 to 0.9 mm. The cross-sectional areas of the thin cross-sectional area 32 and the thick cross-sectional area 31 are the warped state of the solar cell element 2 to be soldered (the solar cell element 2 before the connection tab 3 is soldered), the photocurrent generated, etc. Determine in consideration of

  Moreover, it attaches to the solar cell element 2 so that the boundary portion between the thin cross-sectional area portion 32 and the thick cross-sectional area portion 31 is located in the gap between the solar cell elements connected by the connection tab 3. And good.

  The connection tab 3 is formed by cutting a material such as a copper foil of the thick cross-sectional area 31 into a predetermined length, and mechanically scraping the thin cross-sectional area 32 from one side or both sides, acid, etc. It can be manufactured by etching to a predetermined thickness using. Moreover, in order to make it easy to perform soldering to the bus-bar electrode 21 and the back surface electrode 23 of the solar cell element 2, it is preferable to perform the soldering plating of about 20-70 micrometers to the connection tab 3 on the whole surface.

  FIG. 9 schematically shows a state in which the connection tab 3 according to the present invention is connected to the solar cell element 2 having warpage by soldering. In FIG. 9, 3a and 3b are connection tabs, 32 is a portion with a thin cross-sectional area of the connection tab 3a, 31 is a portion with a large cross-sectional area of the connection tab 3a, and 2 is a solar cell element.

  In this case, a portion 31 having a thick cross-sectional area of the connection tab 3a is attached by soldering to a portion (upper surface in FIG. 9) that is extended by warpage of the solar cell element 2, and contracted by warpage of the solar cell element 2. A portion 32 having a thin cross-sectional area of the connection tab 3b is attached to the portion (the lower surface in FIG. 9) by soldering.

  The temperature of the connection tabs 3a and 3b immediately after being attached to the solar cell element 2 has risen to 200 to 250 ° C. which is the soldering temperature. Thereafter, the connection tabs 3a and 3b are affected by thermal expansion as the temperature is lowered to room temperature. Contracts. Here, the thick portion 31 of the cross-sectional area of the connection tab 3a attached to the portion extending due to the warp of the solar cell element 2 is the disconnection of the connection tab 3b attached to the portion contracting due to the warp of the solar cell element 2. It tends to shrink with a stronger force due to the difference in cross-sectional area than the portion 32 having a small area.

  For this reason, when it sees in the solar cell element 2 whole, the force which curves in the opposite direction to the state of the curvature of the solar cell element 2 before attaching the connection tabs 3a and 3b will work, and the curvature of the solar cell element 2 can be corrected. It becomes possible.

  Thus, the use of the connection tabs 3a and 3b according to the present invention is effective for the solar cell element 2 having the silicon substrate 20 whose one main surface is contracted and warped so as to extend the other main surface.

  As an example of the structure of the solar cell element 2, the same type high-concentration impurity doped layer 24 (FIG. 3) is formed on the silicon substrate 20 having the PN junction for higher efficiency. A solar cell element can be illustrated.

  For example, a high-efficiency solar cell in which a P-type silicon substrate is entirely formed, and a P-type high-concentration impurity doped layer 24 is formed on the back surface side of a silicon substrate formed by forming an N layer on the light-receiving surface side and performing a PN junction. In the element (BSF type solar cell element), the solar cell element 2 is warped due to the shrinkage of the high concentration impurity doped layer 24. That is, the back surface side contracts due to the contraction of the high-concentration impurity doped layer 24 on the back surface side, and the light receiving surface side warps so as to extend. In this case, as shown in FIG. 8, the bus bar electrode 21 on the light receiving surface side is soldered with a portion 31 having a thick cross-sectional area of the connection tab 3 a, and a portion 32 having a thin cross-sectional area of another connection tab 3 b is attached to the back electrode 23. Solder with. That is, soldering is performed on one main surface on the side where warpage extends with a portion 31 having a large cross-sectional area of the connection tab 3a, and soldering is performed on the other main surface with a portion 32 with a thin cross-sectional area of the connection tab 3b. is important.

  Further, an antireflection film (a film that suppresses reflection of light on the short wavelength side with high conversion efficiency of the silicon substrate 20 and enhances absorption efficiency) on the light receiving surface side of the solar cell element 2, particularly on the region where the silicon substrate 20 is exposed. However, the formation of the antireflection film causes warping so that the back surface side of the solar cell element extends and the light receiving surface side contracts. In this case, a portion 31 having a large cross-sectional area of the connection tab 3 is soldered to the extending back surface side, and a portion 32 having a thin cross-sectional area of the connection tab 3 is soldered to the contracting light receiving surface side. good.

  In addition, this invention is not limited to the said embodiment, A change is possible in the range which does not deviate from this invention. For example, solder that coats the connection tab and the electrode of the solar cell element can be applied to lead-free solder in addition to eutectic solder containing lead, etc. I do not care.

It is a top view of a typical solar cell module. It is a partial exploded sectional view of a typical solar cell module. It is sectional drawing which shows the structure of a solar cell element. It is a top view of a solar cell element. It is a top view of the state connected to the several solar cell element with the connection tab. It is sectional drawing of the state connected to the several solar cell element with the connection tab. It is sectional drawing of the state which connected two solar cell elements using the connection tab which concerns on this invention. It is sectional drawing of the connection tab used for the solar cell module of this invention. It is the schematic which showed typically the state which connected the connection tab which concerns on this invention to the solar cell element which the curvature generate | occur | produced.

Explanation of symbols

2, 2a, 2b: Solar cell element 20: Silicon substrate 21: Light receiving surface side electrode (bus bar electrode)
23: Back side electrode 22: Light receiving side electrode (finger electrode)
24: High-concentration impurity doped layers 3, 3a, 3b: Connection tab 32: Thin portion of the connection tab in cross-sectional area 31: thick portion of the connection tab in cross-sectional area

Claims (2)

A solar cell element group in which the light receiving surface side of one solar cell element and the back side of the other solar cell element are electrically connected by a connection tab is disposed between the translucent light receiving surface member and the back surface member. In the solar cell module
The solar cell, wherein the connection tab has a different cross-sectional area of a region connected to the light receiving surface side of one solar cell element and a cross-sectional area of a region connected to the back surface side of the other solar cell element. module. The solar cell element is a PN-bonded silicon substrate, and a high concentration impurity doped layer is provided on one main surface side, and a cross-sectional area of a connection tab connected to the one main surface side is the other main surface. The solar cell module according to claim 1, wherein the cross-sectional areas of the connection tabs connected to the surface are comparatively thin.

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