JP2010118706A - Solar battery module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a yield from lowering when manufacturing solar batteries. <P>SOLUTION: This solar battery 1 has a connection electrode to which a wiring material 41 is connected on one principal plane, wherein the wiring material 41 is adhered to a connection region ST on one principal plane by a resin adhesive 31, and contact area between the wiring material 41 and the connection electrode per unit length in the connection region ST is larger than area of the connection electrode per unit length except the connection region ST. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solar cell module including a plurality of solar cells connected to each other by connecting connection electrodes formed on the surfaces of adjacent solar cells with a wiring material.

  Solar cells are expected as a new energy source because they can directly convert light from the sun, a clean and inexhaustible energy source, into electricity.

  In using such a solar cell as a power source for a house or a building, since the output per solar cell is as small as several watts, usually by connecting a plurality of solar cells electrically in series or in parallel, It is used as a solar cell module whose output is increased to several hundred watts. 17 and 18 show a part of a conventional solar cell module. FIG. 18 is an enlarged cross-sectional view showing an enlarged part of the cross section taken along the line G-G ′ of FIG. 17 in the vicinity of the wiring member 141.

  As shown in FIG. 17, a plurality of solar cells 101 are electrically connected to each other by soldering to bus bar electrodes 121 printed with a width approximately equal to or larger than the width of the wiring material 141 by the conductive wiring material 141. Connected to. In addition, on the main surface of the solar cell 101, a plurality of thin wire electrodes 111 that collect photogenerated carriers generated by the solar cell 101 are formed. The bus bar electrode 121 collects photogenerated carriers from the thin wire electrode 111. As described above, the bus bar electrode 121 is a connection electrode for electrically connecting the wiring member 141.

  Here, as shown in FIG. 18, the wiring member 141 includes a core member 142 made of a metal such as copper and a conductive layer 143 surrounding the outer periphery of the core member 142. The conductive layer 143 is formed, for example, by solder plating on the surface of the core material 142. In addition, the solar cell 101 is made of EVA or the like between a light-transmitting surface member such as glass or light-transmitting plastic and a back surface member made of a resin film such as a polyethylene terephthalate film, a steel plate, or a glass plate. It is sealed with a light-transmitting filler. And as shown in FIG. 17, as for each adjacent solar cell, the bus-bar electrode 121 provided in the light-receiving surface side of one solar cell, and the back surface electrode of the other solar cell are connected by the wiring material 141. Thus, they are electrically connected to each other (see, for example, Patent Document 1).

  By the way, in order to reduce the cost and resource of the solar cell, it is required to make the solar cell thinner. When the solar cell is thinned, when the wiring member 141 is connected to the bus bar electrode 121 on the solar cell by soldering, the linear expansion coefficient of the wiring member 141 and the solar cell including the silicon substrate is greatly different. When each material is expanded or contracted by heating applied in the operation, warping stress is generated, and the solar cell is cracked or the electrode is peeled off. In particular, as the thickness of the solar cell becomes thinner, this problem becomes more prominent, and the manufacturing yield decreases due to cracking of the solar cell and the like. For this reason, conventionally, it has been difficult to reduce the thickness of the solar cell.

  Also, when the thickness of the wiring member 141 is increased to reduce the contact resistance between the wiring member 141 and the bus bar electrode 121 and increase the output of the solar cell module, there is a problem in the physical properties as well. There was a problem that it was likely to occur.

  Therefore, the applicant of the present application has applied for a method of connecting a wiring material on a solar cell using a resin adhesive (Japanese Patent Application No. 2006-229209). FIG. 19 thru | or FIG. 21 has shown a part of solar cell module which connected the wiring material using this method. FIG. 20 is an enlarged cross-sectional view showing a part of the cross section taken along the line H-H ′ of FIG. 19 in the vicinity of the wiring member 241. FIG. 21 is an enlarged cross-sectional view illustrating a part of a cross section taken along line I-I ′ of FIG. 19.

  As shown in FIG. 19, the plurality of solar cells 201 includes a plurality of thin wire electrodes 211 formed on the main surface. As shown in FIG. 20, the wiring member 241 includes a core member 242 made of a metal such as copper, and a conductive layer 243 that surrounds the outer periphery of the core member 242. The conductive layer 243 is formed, for example, by solder plating on the core member 242. As shown in FIG. 21, the wiring member 241 is connected to the main surface of the solar cell 201 by the resin adhesive 231. Further, as shown in FIG. 21, the wiring material 241 and the fine wire electrode 211 are electrically connected by embedding the tip of the fine wire electrode 211 in the conductive layer 243. Therefore, the thin wire electrode 211 is a connection electrode for electrically connecting the wiring member 241 as described above.

  In addition, the solar cell 201 includes a translucent surface member such as glass or translucent plastic, a resin film such as a PET (polyethylene terephthalate) film, a laminated film of a resin film and a metal film, a steel plate or a stainless steel plate. And a back surface member made of, for example, EVA, and the like and sealed with a filler having translucency such as EVA.

  In this method, since the resin adhesive is used for the connection of the wiring member 241, the temperature at the time of bonding can be reduced as compared with the connection using solder. For this reason, since the influence resulting from the above-mentioned thermal expansion can be reduced, it becomes possible to make the thickness of a solar cell thin compared with the past.

JP 2002-359388 A

  However, in the method of connecting the wiring member 241 to the main surface of the solar cell 201 with a resin adhesive, it is necessary to pressurize the wiring member 241 in the direction of the solar cell 201 in order to embed the tip of the thin wire electrode 211 in the conductive layer 243. is there. At this time, if the pressure of the pressurization is too strong, the tip of the thin wire electrode 211 comes into contact with the core member 242 as shown in FIGS. Therefore, as a result of the pressurized pressure being directly transmitted to the surface of the solar cell 201 through the thin wire electrode 211, the solar cell 201 may be cracked or chipped. For this reason, conventionally, the optimum range of pressure during pressurization is narrowed, and productivity cannot be greatly improved.

  Then, an object of this invention is to provide the solar cell module which can improve productivity and can make the thickness of a solar cell small.

A feature of the present invention is a solar cell module having a plurality of solar cells electrically connected to each other by a wiring material, and the solar cell has a connection electrode to which the wiring material is connected on one main surface. The wiring material is bonded to the connection area of the one main surface with a resin adhesive,
The contact area between the wiring member per unit length and the connection electrode in the connection region is larger than the area of the connection electrode per unit length other than the connection region.

  Further, the wiring material has a conductive layer on a surface thereof, and the connection electrode is in contact with the conductive layer. The connection electrode penetrates into the conductive layer and comes into contact with the conductive layer.

  Further, the resin adhesive contains conductive or insulating fine particles.

  ADVANTAGE OF THE INVENTION According to this invention, productivity can be improved and the solar cell module which can make the thickness of a solar cell small can be provided.

It is a top view of the solar cell module concerning a 1st embodiment of the present invention. It is A-A 'sectional drawing of FIG. It is an enlarged view of FIG. It is A-A 'expanded sectional drawing of FIG. It is B-B 'sectional drawing of the solar cell module which concerns on 3rd Embodiment of this invention. (A) is a figure which shows the pattern of the thin wire | line electrode in the solar cell module which concerns on 4th Embodiment of this invention, (b) is an enlarged view of the branch part (the 1). (A) is a figure which shows the pattern of the thin wire | line electrode in the solar cell module which concerns on 4th Embodiment of this invention, (b) is an enlarged view of the branch part (the 2). (A) is a figure which shows the pattern of the fine wire electrode in the solar cell module which concerns on 4th Embodiment of this invention, (b) is an enlarged view of the branch part (the 3). It is a top view of the solar cell module which concerns on 5th Embodiment of this invention. It is a figure which shows the pattern of the thin wire | line electrode and bus-bar electrode in the solar cell module which concerns on 5th Embodiment of this invention. FIG. 10 is an enlarged cross-sectional view taken along the line C-C ′ of FIG. 9. FIG. 10 is an enlarged cross-sectional view taken along the line D-D ′ of FIG. 9. It is a top view of the solar cell module which concerns on 6th Embodiment of this invention. It is the E-E 'cross-sectional enlarged view of FIG. FIG. 14 is an enlarged cross-sectional view taken along the line F-F ′ of FIG. 13. It is sectional drawing which shows the A-A 'cross section of the solar cell module which concerns on the other modification of this invention. It is a top view of the conventional solar cell module 100. FIG. FIG. 18 is an enlarged cross-sectional view taken along the line G-G ′ of FIG. 17. It is a top view of the conventional solar cell module 200. FIG. FIG. 20 is an enlarged cross-sectional view taken along the line H-H ′ of FIG. 19. FIG. 20 is an enlarged cross-sectional view taken along the line I-I ′ of FIG. 19.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

In the following description, a thin wire electrode or a bus bar electrode will be described as an example of a “connection electrode”.
[First Embodiment]
(Solar cell module)
The solar cell module according to the first embodiment of the present invention will be described with reference to FIGS. The solar cell module according to the embodiment of the present invention includes a so-called bus bar-less solar cell. Therefore, the connection electrode in the present embodiment is a thin wire electrode.

  FIG. 1 is a plan view of the solar cell 1 in the solar cell module, FIG. 2 shows a cross section taken along the line AA ′ of FIG. 1, and FIG. 3 shows the wiring member 41 of FIG. FIG. 4 is an enlarged view of the connection area ST (only on the light receiving surface side) of the AA ′ cross section.

  The solar cell 1 according to the present embodiment is formed of a crystalline semiconductor wafer such as a single crystal silicon wafer or a polycrystalline silicon wafer having a thickness of about 0.1 to 0.2 mm, for example, and has a substantially square shape with one side of, for example, 125 mm. Have. The solar cell 1 includes an n-type semiconductor region and a p-type semiconductor region, and a semiconductor junction is formed at the interface between the n-type semiconductor region and the p-type semiconductor region. The n-type and p-type semiconductor regions may be composed of a crystalline semiconductor or an amorphous semiconductor. In addition, a structure in which a substantially intrinsic amorphous silicon layer is sandwiched between a single crystal silicon substrate and an amorphous silicon layer, defects at the interface are reduced, and characteristics of the heterojunction interface are improved, so-called It may be a solar cell having a HIT structure.

  A light receiving surface electrode is formed on the light receiving surface side surface of the solar cell 1 (hereinafter referred to as “light receiving surface”). This light-receiving surface electrode does not include a bus bar electrode, and consists only of a plurality of thin wire electrodes 11 formed in parallel to each other. The thin wire electrode 11 has, for example, an electrode width of 50 to 150 μm, a pitch of 1 mm, and an electrode thickness of 10 to 50 μm, and is formed, for example, about 50 over the entire light receiving surface of the solar cell 1. Such a light-receiving surface electrode can be formed, for example, by screen-printing silver paste and curing it at a temperature of a few hundred degrees.

  Similarly, a back electrode is provided on the back surface (hereinafter referred to as “back surface”) provided on the opposite side of the light receiving surface of the solar cell 1. This back electrode is also composed of a plurality of thin wire electrodes (not shown) formed in parallel to each other. The thin line electrodes provided on the back surface have, for example, an electrode width of 50 to 150 μm, a pitch of 2 mm, and an electrode thickness of 10 to 50 μm, and are formed, for example, about 100 over almost the entire back surface of the solar cell 1. Such a back electrode can be formed, for example, by screen-printing silver paste and curing at a temperature of a few hundred degrees. Here, a bus bar electrode may be provided on the back surface of the solar cell 1. The bus bar electrode can be formed with a width of 300 μm and a thickness of 30 μm, for example. In the present embodiment, the light receiving surface and the back surface of the solar cell 1 are the main surfaces of the solar cell 1, respectively.

  Moreover, since it is not necessary to consider the reduction | decrease of a light-receiving area in the back surface of the solar cell 1, many fine wire electrodes can be formed rather than a light-receiving surface electrode. By increasing the number of thin wire electrodes, it is possible to reduce resistance loss on the back surface side.

  A wiring member 41 is pressure-bonded to the thin wire electrodes on the light receiving surface side and the back surface side in the connection region ST (within the dotted line shown in FIG. 3). The connection part 11a to which the wiring material 41 is connected among the thin wire electrodes 11 is located in the connection region ST as shown in FIG. As shown in FIG. 4, the connecting portion 11 a is a portion of the thin wire electrode 11 that is recessed into the conductive layer 43. The thickness α of the connection portion 11 a is smaller than the thickness β of the conductive layer 43.

  As the adhesive layer 31, a resin adhesive can be used. As the adhesive layer 31, for example, a material containing an epoxy resin as a main component and blended with a crosslinking accelerator that rapidly accelerates crosslinking by heating at 180 ° C. and completes curing in about 15 seconds can be used. The thickness of the adhesive layer 31 is 0.01 to 0.05 mm, and the width is preferably equal to the wiring material 41 or smaller than the conductor thickness in consideration of shielding of incident light. In the present embodiment, as the adhesive layer 31, a resin adhesive formed into a belt-like film sheet having a width of 1.5 mm and a thickness of 0.02 mm is used.

  The wiring member 41 includes a core member 42 made of a metal such as copper and a conductive layer 43 surrounding the outer periphery of the core member 42. The conductive layer 43 is formed by, for example, tin plating the surface of the core material 42. The wiring member 41 is formed in a plate shape having a width of 1.0 mm to 2.0 mm and a thickness of 0.1 mm to 0.3 mm, for example. In this embodiment, tin is used as the material of the conductive layer 43 that coats the wiring material 41. However, the thin wire electrode 11 is a conductive material that is softer than the thin wire electrode 11 and at a temperature at which the adhesive layer 31 is cured. It is desirable to use a material that softens to such an extent that it can be embedded. The conductive layer 43 is not limited to tin, and soft conductive metals including eutectic solder with a lowered melting point can be used.

  Further, when the adhesive layer 31 is a resin adhesive, the mechanical strength of the solar cell module can be improved by containing fine particles. Here, the fine particles have a particle size of 2 to 30 μm, and preferably have an average particle size of about 10 μm. The fine particles may be conductive or insulative. However, when conductive particles are used, nickel, gold-coated nickel, or plastic coated with a conductive metal (for example, , Gold-coated plastic) can be used alone or in combination. By mixing these fine particles, the stress resistance of the solar cell can be enhanced without impairing the original adhesive force of the resin. Different kinds of fine particles mixed in the resin can increase the resistance to compression, expansion and contraction, for example, by adding an aggregate or iron to cement, and the same effect can be obtained. The long-term reliability can be further improved.

  In order to confirm that the problem of the solar cell 1 is alleviated, solar cell modules in which the thickness of the thin wire electrode 11 from the main surface of the solar cell 1 was changed were produced, and the yield was evaluated.

  In the solar cell of the example, the wafer thickness is 100 μm, the width of the light receiving surface electrode (thin wire electrode 11) and the back electrode is 100 μm, the pitch between the electrodes is 2 mm, and the thickness of the thin wire electrode 11 from the main surface of the solar cell is 30 μm (Example) 1), 20 μm (Example 2), and 15 μm (Example 3). The wiring member 41 had a width of 2.0 mm when the conductive layer 43 was coated, the core material 42 had a thickness of 150 μm, and the conductive layer 43 (SnAgCu plating) formed therearound had a thickness of 25 μm.

  Moreover, the solar cell shown in FIG. 19 thru | or FIG. 21 was created as a solar cell of the comparative example 1. FIG. The solar cell 201 of Comparative Example 1 was fabricated with a wafer thickness of 100 μm, a width of the light receiving surface electrode (thin wire electrode 211) and the back surface electrode of 100 μm, a pitch between electrodes of 2 mm, and an electrode thickness of 40 μm. Similarly to the embodiment, the wiring member 241 has a width of 2.0 mm when coated with the conductive layer 243, the thickness of the core member 242 is 150 μm, and the conductive layer 243 (SnAgCu plating) formed therearound. The thickness was 25 μm.

  As for the pressure bonding conditions, Examples 1 to 3 and Comparative Example 1 were pressure bonded for 20 seconds at a pressure of 2 Mpa with a hot plate heated to 180 ° C. About the solar cell 1 of Examples 1-3 after crimping | bonding, sectional drawing of the connection area | region ST is shown in FIG. 4, and sectional drawing of the solar cell 201 of the comparative example 1 is shown in FIG.

  For the calculation of yield, 1000 solar cells were produced for the samples of Examples 1 to 3 and Comparative Example 1, respectively, and evaluated by “EL emission intensity distribution”. When a current of 2 A is passed through the solar cell, infrared light emission near 1000 nm is observed. Using an EL light emission measuring device composed of an imaging device capable of capturing this invisible light emission and software for imaging, a solar cell to which a wiring material is crimped is observed. Since the crack part generated at the time of pressure bonding does not emit light, a crack that cannot be visually recognized is detected. When a crack was found at one location in one solar cell, the yield was calculated as NG. Moreover, the conversion efficiency was measured. The results are shown in Table 1. In addition, the conversion efficiency in the same table is an average value of the non-defective products.

  Under the current crimping conditions, in Comparative Example 1, the thin wire electrode 211 is in contact with the core member 242 as shown in FIG. Therefore, the stress on the solar cell 201 under the thin wire electrode 211 is concentrated, and the solar cell 201 is cracked. The yield of Comparative Example 1 was 80%.

  On the other hand, under the current crimping conditions, in the solar cell modules of Examples 1 to 3, the thin wire electrode 11 (connection portion 11a) does not contact the core member 42 as shown in FIG. Therefore, the crack of the solar cell 1 could be reduced. Moreover, the solar cell modules of Examples 1 to 3 were able to improve the yield while suppressing the decrease in power generation efficiency to 1.1% or less.

  Moreover, the samples of Examples 2 and 3 were able to obtain a higher yield than the sample of Example 1. This is because the thickness of the thin wire electrode from the main surface of the solar cell (20 μm in Example 2, 10 μm in Example 3) is smaller than the thickness (25 μm) of the conductive layer 43 formed around the core material 42. This is because it is possible to suppress the direct contact between the thin wire electrode 11 and the core member 42 regardless of the conditions at the time of crimping the wiring member 41.

  In the present embodiment, it has been described that the resin adhesive is mainly composed of an epoxy resin. However, it is desirable that the resin adhesive can be bonded at a temperature lower than that of solder bonding, preferably 200 ° C. or less, and that curing is completed in about 20 seconds so as not to significantly impair productivity. For example, in addition to acrylic resins that have a low curing temperature and can contribute to the reduction of thermal stress, thermosetting resin adhesives such as polyurethane with high flexibility, thermoplastic adhesives such as EVA resins and synthetic rubbers, It is also possible to use a two-component reaction adhesive that is bonded by mixing a curing agent with an epoxy resin, an acrylic resin, or a urethane resin as a main component that enables bonding at a low temperature.

(Function and effect)
As shown in FIG. 4, in the solar cells of Examples 1 to 3, the thickness α of the connection portion 11 a of the thin wire electrode 11 with the wiring member 41 is smaller than the thickness β of the conductive layer 43. In other words, in the solar cells of Examples 1 to 3, the conductive layer 43 is interposed between the apex of the connection portion 11 a and the surface of the core member 42.

  On the other hand, as shown in FIG. 21, in the solar cell of Comparative Example 1, the thickness of the connection portion of the thin wire electrode 211 with the wiring member 241 is equal to the thickness of the conductive layer 243. In other words, in the solar cell of Comparative Example 1, the apex of the thin wire electrode 211 and the surface of the core member 242 are in contact with each other.

  Thus, in the solar cell module according to the first embodiment, the thickness α of the connection portion 11a of the thin wire electrode 11 with the wiring member 41 is smaller than the thickness β of the conductive layer 43, so that the thin wire electrode 11 becomes a conductive layer. The core material 42 is not brought into contact with the thickness of 43 or more. Therefore, since the stress to the solar cell 1 generated by pressing the thin wire electrode 11 against the core material 42 harder than the conductive layer 43 is relieved, problems such as cracking of the solar cell can be suppressed. As a result, the mechanical strength of the solar cell 1 is increased. In addition, this makes it possible to suppress a decrease in yield during manufacturing. In addition, although the samples of Examples 1 to 3 according to the first embodiment have a substantially reduced cross-sectional area of the thin wire electrode 11 compared to the sample of Comparative Example 1, the output characteristics are almost inferior. Therefore, it can be considered that the effect of suppressing the decrease in yield is more dominant.

  Further, in the solar cell in which the apex of the thin wire electrode 211 is in contact with the surface of the core member 242 as in Comparative Example 1, there is a possibility that a minute crack is generated in the semiconductor layer under the contact portion. When a solar cell having such minute cracks is used for a long period of time, the cracks expand with the passage of time, or moisture may enter the cracks, which may degrade the solar cell characteristics.

  In general, the expansion coefficient of the core member 242 is larger than the expansion coefficient of the solar cell 201. For this reason, stress is applied to the solar cell 201 due to repeated expansion and contraction of the core member 242 due to a temperature difference between day and night or a temperature difference between seasons. This stress is transmitted directly to the thin wire electrode 211 and also to the semiconductor layer. As a result, there is a possibility that defects such as minute cracks may occur in the solar cell 201. Therefore, in the solar cell 201 of the comparative example 1, as described above, the solar cell characteristics may deteriorate with long-time use, and the output of the solar cell module may decrease.

  On the other hand, in the solar cells 1 of Examples 1 to 3, the conductive layer 43 is interposed between the apex of the thin wire electrode 11 and the surface of the core member 42. For this reason, compared with the solar cell 201 of the comparative example 1, the possibility that a micro crack will arise at the time of manufacture in the solar cell 1 of Examples 1 to 3 is reduced. Further, the stress applied to the solar cell 1 due to repeated expansion and contraction of the core member 42 is alleviated by the conductive layer 43. As a result, in the solar cell 1 of Examples 1 to 3, it is possible to suppress the deterioration of the solar cell characteristics associated with long-term use compared to the solar cell 201 of Comparative Example 1. Therefore, according to the solar cell 1 of Examples 1 to 3, it is possible to provide a solar cell module that can maintain a high output even after a long time has elapsed.

Note that the thickness of the thin wire electrode 11 from the main surface of the solar cell is preferably smaller than the thickness of the conductive layer 43. Thereby, irrespective of the crimping conditions of the wiring member 41, the thickness α of the connecting portion 11a of the thin wire electrode 11 with the wiring member 41 can be made smaller than the thickness β of the conductive layer 43. In other words, the conductive layer 43 can be interposed between the apex of the thin wire electrode 11 and the surface of the core member 42. Therefore, it is possible to more reliably suppress the above-described problems that occur when the core member 42 is pressed against the thin wire electrode 11. As a result, it is possible to provide a solar cell module that can effectively improve the yield during manufacturing and can maintain a high output even after a long time has elapsed.
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. In the following, differences between the first embodiment and the second embodiment described above will be mainly described.

  In the second embodiment, the thickness from the main surface of the solar cell 1 to the apex of the thin wire electrode 11 is fixed, and the thickness of the conductive layer 43 is increased. This is an example of a solar cell module in which the thickness from the main surface of the solar cell 1 to the apex of the thin wire electrode 11 is relatively smaller than the thickness of the conductive layer 43.

  In order to confirm that the problem of the solar cell 1 is alleviated, the thickness from the main surface of the solar cell 1 to the apex of the thin wire electrode 11 is fixed at 30 μm and the conductive layer 43 under the same conditions as in the first embodiment. The thickness of the solar cell was changed to 20 μm (referred to as Comparative Example 2), 25 μm (Example 1), 30 μm (referred to as Example 4), 35 μm (referred to as Example 5), and 40 μm (referred to as Example 6). A module was produced. The production yield of each such solar cell module was evaluated. The yield was evaluated by “EL emission intensity distribution” as in the first embodiment. The results are shown in Table 2.

  As shown in Table 2, in Examples 4 to 6, the yield exceeded 90%, and an improvement was observed. This is because the thickness from the main surface of the solar cell 1 to the apex of the thin wire electrode 11 is fixed and the thickness of the conductive layer 43 is increased so that the thickness from the main surface of the solar cell 1 to the apex of the thin wire electrode 11 is increased. This is because the thickness of the conductive layer 43 is larger than the thickness of the thin wire electrode 11 (here, fixed to 30 μm) because the thickness is smaller than the thickness of the soft conductor.

  As shown in Table 2, in Examples 1 and 4 to 6, the yield was improved as compared with Comparative Example 2. This is because the thickness α of the connecting portion 11a of the thin wire electrode 11 to the wiring member 41 is smaller than the thickness β of the conductive layer 43 as shown in FIG. This is because the core material 42 was not touched by being sunk more than the thickness of the layer 43.

  In addition, the samples of Examples 5 and 6 were able to obtain a higher yield than the samples of Examples 1 and 4. This is because, in the samples of Examples 5 and 6, the thickness of the thin wire electrode from the main surface of the solar cell (30 μm) is the thickness of the conductive layer 43 formed around the core material 42 (35 μm in Example 5). This is because it is possible to suppress the direct contact between the thin wire electrode 11 and the core material 42 regardless of the conditions when the wiring material 41 is crimped.

(Function and effect)
As described above, in the solar cell module according to the second embodiment, the thickness from the main surface of the solar cell 1 to the top of the thin wire electrode 11 is fixed, and the thickness of the conductive layer 43 is increased, so that the thin wire is formed from the main surface. Even when the thickness up to the top of the electrode 11 is smaller than the thickness of the conductive layer 43, the same effect as the solar cell module according to the first embodiment can be obtained. That is, the stress to the solar cell 1 generated by pressing the thin wire electrode 11 against the core material 42 that is harder than the conductive layer 43 can be relaxed, and problems such as cracking of the solar cell can be suppressed. As a result, the mechanical strength of the solar cell 1 is increased. In addition, this makes it possible to suppress a decrease in yield during manufacturing.

  In Examples 1 and 4 to 6, the conductive layer 43 is interposed between the apex of the thin wire electrode 11 and the surface of the core member 42. For this reason, in Examples 1 and 4-6, the possibility that a micro crack will arise at the time of manufacture is reduced compared with the solar cell of the comparative example 2. Further, the stress applied to the solar cell 1 due to repeated expansion and contraction of the core member 42 is alleviated by the conductive layer 43. As a result, in Examples 1 and 4 to 6, it is possible to suppress a decrease in solar cell characteristics associated with long-term use compared to Comparative Example 2. Therefore, according to Examples 1 and 4 to 6, it is possible to provide a solar cell module that can maintain a high output even after a long time has elapsed.

In addition, when the layer thickness of the conductive layer 43 exceeds 40 μm, the flatness deteriorates when formed on the solar cell 1. Therefore, in Example 6, it is considered that the yield slightly decreased.
[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to the drawings. In the following, differences between the first embodiment and the second embodiment described above will be mainly described. In addition, since the planar external appearance of the solar cell module according to the third embodiment is the same as that of the solar cell module according to the first or second embodiment, it will be described with reference to FIGS. To do.

  In the third embodiment, a groove is formed in the thin wire electrode 11 in the connection region ST. That is, the portion in the connection region ST of the thin wire electrode is formed lower than the other portions. In other words, the portion of the fine wire electrode 11 other than the connection region ST is formed higher than the portion in the connection region ST. FIG. 5 shows the state of the cross section after the pressure bonding. FIG. 5 shows a cross section taken along the line B-B ′ of FIG. 1 (the state of the cross section on the thin wire electrode 11).

  For example, the fine wire electrode 11 is applied to the entire fine wire electrode by the first screen printing, and the second and subsequent times are the same as those applied to the first time using a screen in which only the position corresponding to the connection region ST is masked. It can be formed by printing a silver paste and adjusting the thickness appropriately. After the application is completed, it can be formed by curing at a temperature of hundreds of degrees. Thus, the solar cell module was produced on the same conditions as 1st Embodiment except forming a groove part in the thin wire electrode 11 in the connection area | region ST.

  In this embodiment, while fixing the thickness from the main surface of the solar cell 1 in the portion of the thin wire electrode in the connection region ST to 15 μm, the main portion of the solar cell 1 in the portion of the thin wire electrode 11 other than the connection region ST. The thickness from the surface was changed to 15 μm (Example 7), 20 μm (Example 8), 30 μm (Example 9), and 40 μm (Example 10). Table 3 shows the conversion efficiency obtained in the same manner as in the first embodiment.

  As shown in Table 3, it can be seen that the conversion efficiency increases as the portion of the thin wire electrode 11 other than the connection region ST is increased.

(Function and effect)
As described above, in the solar cell module according to the third embodiment, the thickness of the portion of the thin wire electrode 11 in the connection region ST from the main surface of the solar cell is smaller than that of the conductive layer 43. Therefore, the portion of the thin wire electrode 11 that is recessed into the conductive layer 43 (connection portion) is made thinner than the thickness of the conductive layer 43. For this reason, the apex of the thin wire electrode 11 does not contact the core material 42, and it is possible to suppress problems such as cracking of the solar cell caused by the core material 42 harder than the conductive layer 43 being pressed against the thin wire electrode 11. Can do.

Further, the thickness of the portion of the thin wire electrode 11 other than the connection region ST from the main surface of the solar cell 1 is made larger than the thickness of the portion of the thin wire electrode 11 in the connection region ST from the main surface of the solar cell. ing. For this reason, since the cross-sectional area of the thin wire electrode in the region other than the connection region ST, that is, the light receiving region can be increased and the resistance can be reduced, the conversion efficiency can be improved.
[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to the drawings. In the following description, differences from the first to third embodiments will be mainly described.

  In the fourth embodiment, a groove is formed in the thin wire electrode in the connection region ST. Moreover, the width | variety of the part in connection area | region ST among thin wire electrodes is more than the width | variety of the part other than connection area | region ST among thin wire electrodes. Specifically, in the solar cell module according to the fourth embodiment, the portion of the thin wire electrode in the connection region ST branches into a plurality of branch portions. And the area per unit length of the connection part with the conductive layer 43 is larger than the area per unit length of parts other than the connection area | region ST among thin wire electrodes.

  The fine line electrode is applied, for example, by the first screen printing, and the entire fine line electrode having a pattern to be described later is applied, and the second and subsequent times are applied for the first time using a screen in which only the position corresponding to the connection region ST is masked. The same silver paste as above is printed and the thickness is adjusted appropriately. And after completion | finish of application | coating, it can form by making it harden | cure at the temperature of hundreds of ten degrees.

  In the present embodiment, the thickness from the main surface of the solar cell in the connection region ST in the thin wire electrode is 15 μm in common in Examples 11 to 14, and the solar in the portion other than the connection region ST in the thin wire electrode The thickness from the main surface of the battery is 40 μm. Further, the electrode pattern of the portion in the connection region ST of the thin wire electrodes is changed to 1 (Example 11), 2 (Example 12), 3 (Example 13), and 5 (Example 14). A solar cell module was produced respectively. The electrode width of the fine wire electrode was 100 μm, and the thickness of the conductive layer was 20 μm.

  The pattern of the thin wire electrode of the solar cell module according to the fourth embodiment will be described with reference to FIGS. The pattern of the fine wire electrode 13 in Example 12 is shown in FIG. 6, the pattern of the fine wire electrode 15 in Example 13 is shown in FIG. 7, and the pattern of the fine wire electrode 17 in Example 14 is shown in FIG. Moreover, in each figure, (a) shows the top view of the fine wire electrode screen-printed on the solar cell of the solar cell module, (b) shows the figure which expanded connection area ST vicinity.

  In Example 12, two branch portions 13a and 13b were formed in the connection region ST. In Example 13, three branch portions 15a, 15b, and 15c were formed in the connection region ST. In Example 14, five branch portions 17a, 17b, 17c, 17d, and 17e were formed in the connection region ST. The thin wire electrodes 13, 15, and 17 were formed on the solar cell 1 by screen printing with a scale shown in each drawing.

  As described above, a solar cell module was produced under the same conditions as in the first embodiment, except that the portion of the thin wire electrode in the connection region ST was branched into a plurality of branches. Table 4 shows the conversion efficiency obtained in the same manner as in the first embodiment.

  As shown in Table 4, by increasing the number of portions in the connection region ST of the thin wire electrodes, the width ratio of the thin wire electrodes in the connection region ST is doubled, so that the thin wire electrode and the conductive per unit length are increased. It can be seen that the conversion efficiency is increased by the increase in the contact area with the layer.

(Function and effect)
As described above, in the solar cell module according to the fourth embodiment, the portion in the connection region ST of the thin wire electrode is made lower than the other portions and branches into a plurality of branch portions. The total area per unit length in the portion of the thin wire electrode in the connection region ST is equal to or larger than the area per unit length of the portion of the thin wire electrode other than the connection region ST.

  In the present embodiment, the number of thin line electrodes in the connection region ST is increased in order to make the width of the portion in the connection region ST larger than the width of the portion other than the connection region ST. While the number of the portions is one, the width may be increased. Further, the thin wire electrode may have the same thickness in the connection region ST and other regions. Also in this case, since the resistance between the thin wire electrode and the wiring material can be reduced, the conversion efficiency can be improved.

  As described above, by increasing the width of the portion in the connection region ST in the thin wire electrode, the contact area between the thin wire electrode and the conductive layer per unit length is increased. Therefore, the resistance between the thin wire electrode and the wiring material can be lowered, and the conversion efficiency can be improved.

Moreover, the solar cell module which concerns on 4th Embodiment is the conductive layer 43 from the main surface of the solar cell 1 of the part in connection area | region ST among thin wire | line electrodes similarly to the said 1st thru | or 3rd embodiment. Less than the thickness of Therefore, the fine wire electrode does not sink into the thickness of the conductive layer 43 and contact the core material 42. Therefore, it is possible to suppress problems such as cracking of the solar cell caused by pressing the thin wire electrode against the core material 42 that is harder than the conductive layer 43.
[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a plan view of the solar cell module according to the present embodiment. As shown in the figure, a thin wire electrode 11 and a bus bar electrode 20 are formed on the solar cell 1a according to the present embodiment. The connection electrode in this embodiment is the bus bar electrode 20. FIG. 10 shows a printing pattern of the thin wire electrode 11 and the bus bar electrode 20. The thin wire electrode 11 and the bus bar electrode 20 intersect. Specifically, the bus bar electrode 20 is formed along the direction in which the solar cells 1a are arranged in the connection region ST where the wiring member 41 is connected to the solar cells 1a. Accordingly, the wiring member 41 is disposed on the bus bar electrode 20. The bus bar electrode 20 can be formed using the same material as the thin wire electrode 11.

  FIG. 11 shows a CC ′ cross section of FIG. 9. 12 shows an AA ′ cross section of FIG. As shown in FIG. 11, the thickness of the bus bar electrode 20 from the main surface of the solar cell 1 a is smaller than the thickness of the thin wire electrode 11 from the main surface of the solar cell 1. Specifically, the bus bar electrode 20 has the same thickness as the groove portion of the thin wire electrode 11 described in the third embodiment.

  Further, the width of the bus bar electrode 20 is smaller than the width of the conductive layer 43. Accordingly, as shown in FIG. 12, the bus bar electrode 20 is recessed into the conductive layer 43 to form a connection portion 20 a.

  Here, the thickness γ of the connection portion 20 a is smaller than the thickness ε of the conductive layer 43. Further, the thickness of the connection electrode (bus bar electrode 20) from the main surface of the solar cell 1 a is smaller than the thickness of the conductive layer 43. Therefore, the conductive layer 43 is interposed between the apex of the connection portion and the surface of the core member 42.

  Hereinafter, an example of a method for forming the thin wire electrode 11 and the bus bar electrode 20 will be described.

  First, in the first screen printing, the entire thin wire electrode 11 is applied. Subsequently, in the second screen printing, the bus bar electrode 20 is applied with a thickness smaller than that of the thin wire electrode 11 in the connection region ST. The bus bar electrode 20 can be formed with a thickness of 10 to 50 μm from the main surface of the solar cell 1a. Thereafter, they are cured at a temperature of a few hundred degrees.

  By using such a method, 10 solar cell modules according to Example 15 were manufactured with the bus bar electrode 20 having a thickness of 15 μm from the main surface of the solar cell 1 a and the thin wire electrode 11 having a thickness of 40 μm from the main surface of the solar cell 1. did. In addition, ten solar cell modules according to Example 10 were produced. In Example 15, similarly to Example 10, the wiring material 41 having the conductive layer 42 with a thickness of 25 μm was used.

  About Example 10 and Example 15, the temperature cycle test (JIS C8917) was done and the photoelectric conversion efficiency of the solar cell module before and behind a test was compared. In the temperature cycle test, in accordance with JIS standards, changing the temperature from a high temperature (90 ° C.) to a low temperature (−40 ° C.) or from a low temperature to a high temperature was performed as one cycle. The JIS standard specifies that 200 cycles should be performed, but 600 cycles were performed in this test. The photoelectric conversion efficiency before and after the test is shown in the table below. The photoelectric conversion efficiency is a value converted by the light receiving area of one solar cell 1.

After 600 cycles, the photoelectric conversion efficiency of Example 10 decreased by 5.0%. On the other hand, the photoelectric conversion efficiency of Example 15 decreased by 4.1%. Thus, the decrease in the photoelectric conversion efficiency of Example 15 could be suppressed because the bus bar electrode 20 was embedded in the conductive layer 43, so that the area of the connection portion between the connection electrode and the wiring material was increased. This is because electrical bonding is improved.
(Function and effect)
In the solar cell module according to the present embodiment, the bus bar electrode 20 having a thickness smaller than that of the conductive layer 43 is formed in the connection region ST. The thickness γ of the connection portion 20 a between the bus bar electrode 20 and the wiring member 41 is smaller than the thickness ε of the conductive layer 43. Therefore, the conductive layer 43 is interposed between the bus bar electrode 20 and the core member 42. By connecting the connecting portion 20 a into the conductive layer 43, the bus bar electrode 20 and the wiring member 41 are mechanically and electrically connected.

  Therefore, when the wiring member 41 is crimped, the stress due to the crimping can be relaxed by the conductive layer 43. The bus bar electrode 20 is formed along the longitudinal direction of the connection region ST. Therefore, almost the entire bus bar electrode 20 can be used as a connection electrode. As a result, the mechanical and electrical connection between the bus bar electrode 20 and the wiring member 41 can be improved.

In Example 15, the conductive layer 43 is interposed between the apex of the bus bar electrode 20 and the surface of the core member 42. For this reason, in Example 15, possibility that a micro crack will arise at the time of manufacture is reduced. Further, the stress applied to the solar cell 1 a due to repeated expansion and contraction of the core member 42 is alleviated by the conductive layer 43. As a result, in Example 15, it is possible to suppress a decrease in solar cell characteristics associated with long-term use. Therefore, according to Example 15, the solar cell module which can maintain a high output even after a long time can be provided.
[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described with reference to the drawings. FIG. 13 is a plan view of the solar cell module according to the present embodiment. The difference between the present embodiment and the fifth embodiment is that the solar cells 1b are connected to each other by a plurality (five) of wiring members 41. The wiring member 41 is formed in a thin wire (electric wire) shape. However, the cross-sectional shape of the wiring member 41 is not limited to a circle but may be an ellipse or a rectangle.

  14 is a cross-sectional view taken along the line EE ′ of FIG. FIG. 15 is a cross-sectional view taken along the line FF ′ of FIG.

  As shown in FIG. 14, the bus bar electrode 20 is formed along the direction in which the solar cells 1b are arranged. A wiring material 41 is disposed on the bus bar electrode 20. The bus bar electrode 20 can be formed using the same material as the thin wire electrode 11.

  Further, as shown in FIG. 14, the thickness of the bus bar electrode 20 from the main surface of the solar cell 1 b is smaller than the thickness of the thin wire electrode 11 from the main surface of the solar cell 1. Specifically, the bus bar electrode 20 has the same thickness as the groove portion of the thin wire electrode 11 described in the third embodiment.

  Further, the width of the bus bar electrode 20 is smaller than the width of the conductive layer 43. Accordingly, the bus bar electrode 20 is recessed into the conductive layer 43. That is, in this embodiment, the bus bar electrode 20 is a connection electrode with the wiring member 41. Here, the thickness of the bus bar electrode 20 from the main surface of the solar cell 1 b is smaller than the thickness of the conductive layer 43. Therefore, the thickness of the connection portion embedded in the conductive layer 43 in the bus bar electrode 20 is smaller than the thickness of the conductive layer 43. Therefore, the conductive layer 43 is interposed between the bus bar electrode 20 and the surface of the core member 42.

  Hereinafter, an example of a method for forming the thin wire electrode 11 and the bus bar electrode 20 will be described.

First, in the first screen printing, the entire thin wire electrode 11 is applied. Subsequently, in the second screen printing, the bus bar electrode 20 is applied with a thickness smaller than that of the thin wire electrode 11 in the connection region ST. The bus bar electrode 20 can be formed from the main surface of the solar cell 1 with a thickness of 10 to 50 μm. Thereafter, they are cured at a temperature of a few hundred degrees.
(Function and effect)
In the solar cell module according to the present embodiment, the bus bar electrode 20 having a thickness smaller than that of the conductive layer 43 is formed in the connection region ST. The thickness of the connecting portion between the bus bar electrode 20 and the wiring member 41 is smaller than the thickness of the conductive layer 43. Therefore, the conductive layer 43 is interposed between the bus bar electrode 20 and the core member 42. The bus bar electrode 20 is mechanically and electrically connected to the wiring member 41 by sinking into the conductive layer 43.

Therefore, when the wiring member 41 is crimped, the stress due to the crimping can be relaxed by the conductive layer 43. The bus bar electrode 20 is formed along the longitudinal direction of the connection region ST. Therefore, almost the entire bus bar electrode 20 can be used as a connection electrode. As a result, the mechanical and electrical connection between the bus bar electrode 20 and the wiring member 41 can be improved.
(Other changes)
The gist of the present invention is that the thickness of the connection portion of the connection electrode to the wiring material is smaller than the thickness of the soft conductor in the connection region where the wiring material and the connection electrode are connected. Therefore, when a thin wire electrode is used as the connection electrode, a groove portion having substantially the same width as the electrode width of the thin wire electrode is formed on the surface of the solar cell on which the thin wire electrode is formed, and the groove portion bottom surface is formed along the groove width. Fine wire electrodes can also be screen printed.

  Hereinafter, an example in which a groove portion having substantially the same width as the electrode width of the fine wire electrode is formed on the surface of the solar cell on which the fine wire electrode is formed, and the fine wire electrode is formed inside the groove will be described with reference to FIG. In the following, differences from the above-described embodiments will be mainly described. In addition, since the planar external appearance of the solar cell module shown here is not different from the solar cell module of the first or second embodiment, it will be described with reference to FIGS.

  FIG. 16 is an enlarged view of a main part of the A-A ′ cross section in FIG. 1. In a solar cell module according to another embodiment of the present invention, a groove portion 18 for embedding the thin wire electrode 19 is provided on the light receiving surface of the solar cell 1, and the thin wire electrode 19 is embedded in the groove portion 18. A wiring member 41 is pressure-bonded to the fine wire electrode 19 via an adhesive layer 31.

  When it does in this way, the thickness from the solar cell 1 surface of the thin wire | line electrode 19 can be enlarged compared with 1st-3rd embodiment. Therefore, since the resistance of the thin wire electrode 19 can be reduced, the conversion efficiency of the solar cell can be improved.

  Although the present invention has been described with reference to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Solar cell, 11 ... Fine wire electrode, 11a ... Connection part, 13 ... Fine wire electrode, 13a, 13b ... Branch part, 15 ... Fine wire electrode, 15a, 15b, 15c ... Branch part, 17 ... Thin wire electrode, 17a, 17b, 17c, 17d, 17e ... branch 19 ... fine wire electrode, 20 ... busbar electrode, 20a ... connection part, 31 ... adhesive layer, 41 ... wiring material, 42 ... core material, 43 ... conductive layer, 100 ... sun Battery module, 101 ... solar cell, 111 ... fine wire electrode, 121 ... bus bar electrode, 141 ... wiring material, 142 ... core material, 143 ... conductive layer, 200 ... solar cell module, 201 ... solar cell, 211 ... thin wire electrode, 211a ... Connection part, 231 ... Resin adhesive, 241 ... Wiring material, 242 ... Core material, 243 ... Conductive layer, ST ... Connection region

Claims (4)

A solar cell module having a plurality of solar cells electrically connected to each other by a wiring material,
The solar cell has a connection electrode to which the wiring material is connected to one main surface,
The wiring material is bonded to the connection area of the one main surface by a resin adhesive,
The solar cell module, wherein a contact area between the wiring member per unit length in the connection region and the connection electrode is larger than an area of the connection electrode per unit length other than the connection region . The wiring material has a conductive layer on the surface,
The solar cell module according to claim 1, wherein the connection electrode is in contact with the conductive layer.   The solar cell module according to claim 2, wherein the connection electrode is recessed into the conductive layer and is in contact with the conductive layer.   The solar cell module according to claim 1, wherein the resin adhesive includes conductive or insulating fine particles.

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