JP2009141380A - Solar battery module, and solar battery element structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar battery module, capable of achieving excellent long-period reliability by restricting occurrence of defects such as micro cracks caused by stress. <P>SOLUTION: On the light receiving side and/or the non-light receiving side of a plurality of solar battery elements, bus bar electrodes (4a and 5a) for taking the output to the external are provided, the bus bar electrodes (4a and 5a) of the solar battery elements are connected to each other with an inner lead 8, and they are sealed in filler 10 to provide the solar battery module. The inner lead 8 and the bus bar electrodes (4a and 5a) are connected with solder 6, and the bus bar electrodes (4a and 5a) are composed in such a way that their length direction ends are directly in contact with the filler 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solar cell module, and more particularly to a solar cell module in which solar cell elements having electrodes on a semiconductor substrate are connected by a plurality of inner leads.

  A general structure of a solar cell element is shown in FIGS. FIG. 3A is a diagram showing a cross-sectional structure of the solar cell element X. FIG. FIG. 4 is a diagram showing an example of the electrode shape, where (a) is the light receiving surface side (front surface), and (b) is the non-light receiving surface side (back surface).

  Such a solar cell element X is produced as follows.

First, a p-type semiconductor silicon substrate 1 made of single crystal silicon or polycrystalline silicon having a thickness of about 0.3 to 0.4 mm and a size of about 100 to 150 mm square is prepared. Then, an n-type diffusion layer 1 a is formed on the silicon substrate 1 to form a semiconductor junction 3. Such an n-type diffusion layer 1a is formed by placing the silicon substrate 1 in a diffusion furnace and heating it in phosphorus oxychloride (POCl ₃ ), so that the entire surface portion of the silicon substrate 1 is phosphorous that is an n-type impurity. Atoms can be diffused to form the n-type diffusion layer 1a having a thickness of about 0.2 to 0.5 μm. Thereafter, the diffusion layer portions on the side surface portion and the bottom surface portion are removed.

  On the light receiving surface side of the solar cell element X, for example, an antireflection film 2 made of a silicon nitride film is formed. Such an antireflection film 2 is formed, for example, by a plasma CVD method or the like, and also has a function as a passivation film.

  Then, the front electrode 5 and the back electrode 4 are simultaneously formed by applying a silver paste on the surface of the silicon substrate 1 and applying an aluminum paste and a silver paste on the back surface and baking.

  As shown in FIG. 4A, the back electrode 4 is composed of a back bus bar electrode 4a for extracting output from the back surface and a back current collecting electrode 4b. Further, as shown in FIG. 4B, the surface electrode 5 is composed of a surface bus bar electrode 5a for extracting output from the surface, and a surface finger electrode 5b for current collection provided so as to be orthogonal thereto. The

  The back surface collecting electrode 4b is formed by printing and baking an aluminum paste by a screen printing method. At this time, aluminum diffuses into the silicon substrate 1 to prevent carriers generated on the back surface from recombining. A back surface field layer is formed. Moreover, the back surface bus bar electrode 4a, the front surface bus bar electrode 5a, and the front surface finger electrode 5b are formed by a method of printing and baking a silver paste by a screen printing method. The surface electrode 5 may be formed by etching away a portion corresponding to the electrode of the antireflection film 2 or may be formed directly from above the antireflection film 2 by a technique called fire-through. .

  Also, the electrode portions of these solar cell elements X may be covered with solder to facilitate wiring for taking out the output to the outside, or to maintain the durability of the electrodes. Dip method, jet type, etc. are adopted.

  Since a single solar cell element generates a small electrical output, it is necessary to connect a plurality of solar cell elements in series and parallel so that a practical electrical output can be taken out. As an example of the solar cell module, FIG. 3B shows a solar cell module Y configured by combining the solar cell elements X of FIG.

  As shown in FIG. 3B, the plurality of solar cell elements X are electrically connected by the inner leads 8, and an ethylene vinyl acetate copolymer (EVA) is provided between the translucent panel 9 and the back surface protective material 11. The solar cell module Y is configured by being hermetically sealed with a filler 10 containing, for example, the main component. The output of the solar cell module Y is connected to the terminal box 13 via the output wiring 12. FIG. 3 (c) shows a partially enlarged view of the internal structure of the solar cell module Y of FIG. 3 (b).

  As shown in FIG.3 (c), the front surface bus-bar electrode 5a of the solar cell element X1 and the back surface bus-bar electrode 4a of the adjacent solar cell element X2 are connected by the inner lead 8, and several solar cell elements X are connected. Electrically connected. In general, the inner leads are made of a copper foil having a thickness of about 0.1 to 0.3 mm, and the entire surface is solder-coated. The inner leads 8 and the bus bar electrodes (4a, 5a) of the solar cell element X are used. The solar cell element X and the inner lead 8 are connected by soldering by heating with solder interposed therebetween and by partial or full length or by crimping at a plurality of locations.

JP 2003-69055 A

  As described above, when connecting the inner lead 8 and the bus bar electrodes (4a, 5a) of the solar cell element X using solder, a solder coating is provided on the surface of the bus bar electrodes (4a, 5a) in advance. When heat-welding each other together with the solder coating of the inner lead 8, a solder coating is provided only on the inner lead 8, and the solder of the inner lead 8 is heat-welded directly to the electrode portion using a flux or the like However, in these conventional solar cell elements X or solar cell modules Y, there is a problem that cracks occur in the longitudinal direction of the bus bar electrodes (4a, 5a), that is, in the connection direction with the inner leads 8. there were.

  In view of this problem, the inventors have intensively studied and found the following facts.

  FIG. 7A shows a cross-sectional view taken along the line AA in FIG. 3C, and FIG. 7B shows a simulation of stress applied to the cross section of the electrode in part B of FIG. 7A. Indicates. Note that, in order to make the configuration easy to understand, the cross-sectional view is drawn with exaggerated dimensions of the main part, which is different from the actual size ratio.

  As shown in FIG. 7A, the bus bar electrodes (4a, 5a) are covered with the solder 6 up to the end portions of the bus bar electrodes (4a, 5a) which are output lead-out terminal portions connected to the inner leads 8. It has been broken. At this time, as shown in FIG. 7B, the largest tensile stress is generated in the vicinity of the boundary line between the end of the surface bus bar electrode 5a and the surface of the silicon substrate 1, and the stress tends to concentrate. I understand that.

  Due to this stress, defects such as microcracks are generated in the silicon substrate 1 below the bus bar electrodes (4a, 5a), and in the subsequent process, the microcracks are used as starting points to develop large cracks and cracks. It was found that the output could not be taken out sufficiently and the output was reduced. In particular, since solar cell modules are usually installed outdoors, contraction and expansion due to daily temperature cycles are repeated. Since the stress at this time is weighted and applied to the vicinity of the boundary line between the end of the bus bar electrode (4a, 5a) and the surface of the silicon substrate 1, the solar cell element X is cracked and the long-term reliability is reduced. A problem occurs.

Further, if the electrodes (electrodes mainly composed of silver) are completely covered with the solder 6 even in directions other than the longitudinal direction of the bus bar electrodes (4a, 5a), cracks may occur along the peripheral edge. is there. As a result of investigations by the inventors, the following conclusion was obtained. First, the thermal conductivity at 0 ° C. of silicon of the substrate constituting the solar cell element is 168 W · m ⁻¹ · K ⁻¹ , silver constituting the electrode is 428 W · m ⁻¹ · K ⁻¹ , and aluminum is 236 W ·· m ⁻¹ · K ⁻¹ . The copper constituting the inner lead is 403 W · m ⁻¹ · K ⁻¹ . On the other hand, the thermal conductivity of the solder is only about 50 W · m ⁻¹ · K ^−1, and as a result, even if the solder is heated spotly with hot air or the like, the surface of the substrate is melted until the necessary portion of the solder melts. The silver will heat up on the entire surface. Therefore, it is considered that stress concentration was likely to occur particularly in the peripheral portion of the electrode due to the difference in coefficient of thermal expansion when cooled.

  Further, when the solar cell module is manufactured, the inner lead 8 covered with solder is welded to the electrode. At this time, the inner lead 8 is displaced and soldered to the surface finger electrode 5b connected to the surface bus bar electrode 5a. If the solder is welded, there is a problem that micro cracks and the like are generated more severely due to a stress caused by a difference in thermal expansion between the solder and copper constituting the inner lead 8 or contraction.

  In recent years, attempts have been made to reduce the amount of semiconductor material used by reducing the thickness of the silicon substrate 1 from the viewpoint of cost reduction. If the thickness of the silicon substrate 1 is reduced, it becomes weaker against the impact and stress, and there is a problem that the frequency of occurrence of cracks and cracks increases when stressed by such solder is applied.

  In order to avoid this problem, Patent Document 1 discloses a method in which cracking of the element in the manufacturing process of the solar cell element and the module can be reduced by attaching a reinforcing material to the back surface, the front surface, and the side surface of the solar cell element. Has been. However, according to this method, although the crack at the edge portion of the semiconductor substrate accompanying the thinning of the semiconductor substrate can be suppressed, the stress applied near the boundary line between the bus bar electrode end and the semiconductor substrate surface is reduced. Therefore, the effect of suppressing the occurrence of defects such as microcracks is poor.

  The present invention has been made in view of such conventional problems, and reduces the stress applied to the vicinity of the boundary between the edge portion and the semiconductor substrate along the longitudinal direction of the bus bar electrode of the solar cell element. An object of the present invention is to provide a solar cell module excellent in long-term reliability by suppressing the occurrence of defects such as microcracks.

  Another object of the present invention is to reduce the stress applied to the vicinity of the boundary between the peripheral edge of the silver electrode containing silver as a main component and the semiconductor substrate in the solar cell element, and to generate defects such as microcracks caused by this stress. It is to provide a solar cell module which is suppressed and excellent in long-term reliability.

  In order to achieve the above object, the solar cell module of the present invention is provided with bus bar electrodes for taking out outputs to the outside on the light receiving surface side and / or the non-light receiving surface side of a plurality of solar cell elements. A battery module in which the bus bar electrodes of the battery element are connected to each other with an inner lead and sealed in a filler, the inner lead and the bus bar electrode are connected by solder, and the bus bar electrode is An edge portion along a connection direction with the inner lead is configured to be in direct contact with the filler. Since it did in this way, the edge part along the connection direction with the inner lead which is the end part of the bus bar electrode in the longitudinal direction is covered with the filler instead of being covered with the rigid solder, so that the stress is relieved. Easy to be. Therefore, among the boundary line between the substrate surface of the solar cell element and the bus bar electrode, the tensile stress applied to the vicinity of the edge portion along the connecting direction with the inner lead where the distance is the shortest and the stress is likely to be concentrated can be reduced. Therefore, the generation of defects such as microcracks can be suppressed in the substrate below the bus bar electrode, and cracks and cracks in the subsequent process can be suppressed.

  Further, the solar cell module of the present invention is provided with bus bar electrodes for taking out outputs to the outside on the light receiving surface side and / or the non-light receiving surface side of the plurality of solar cell elements, and the bus bar electrodes of these solar cell elements. A solar cell module comprising an inner lead connected to each other and enclosed in a filler, wherein the inner lead and the bus bar electrode are connected by solder, and the bus bar electrode is connected to the inner lead. An edge portion along the direction is covered with a covering, and the covering is configured to come into contact with the filler. Since it did in this way, the edge part along the connection direction with the inner lead, which is the end part in the longitudinal direction of the bus bar electrode, is filled through a covering such as a solder resist instead of being covered with a rigid solder. Since it is covered with a material, stress is easily relieved. Therefore, among the boundary line between the substrate surface of the solar cell element and the bus bar electrode, the tensile stress applied to the vicinity of the edge portion along the connecting direction with the inner lead where the distance is the shortest and the stress is likely to be concentrated can be reduced. Therefore, the generation of defects such as microcracks can be suppressed in the substrate below the bus bar electrode, and cracks and cracks in the subsequent process can be suppressed. Further, when the inner lead is thermally welded to the bus bar electrode, the edge portion of the bus bar electrode along the connecting direction with the inner lead is covered with this covering, so that the solder flows into the edge portion of the bus bar electrode. There is little fear of covering this edge part.

  Furthermore, the solar cell module of the present invention comprises a plurality of solar cell elements each having a silver electrode mainly composed of silver on the light receiving surface side and / or the non-light receiving surface side, and at least a part of the silver electrode is soldered. A solar cell comprising: an inner lead that is connected and electrically connects the plurality of solar cell elements; and a filler that encloses the plurality of solar cell elements and the inner lead therein. It is a module, Comprising: The peripheral part of the said silver electrode is comprised so that it may contact with the said filler directly. By doing so, instead of the periphery of the silver electrode mainly composed of silver having a high thermal conductivity and being easily affected by the heating at the time of welding with the inner lead being covered with the rigid solder, Since it is covered with a filler, stress is easily relieved. Therefore, since the tensile stress applied to the substrate surface of the solar cell element and the vicinity of the periphery of the silver electrode can be reduced, it is possible to suppress the occurrence of defects such as microcracks in the substrate under the silver electrode, Cracks and cracks can be suppressed. Moreover, it can suppress that a silver electrode peels from the substrate surface.

  The solar cell module of the present invention includes a plurality of solar cell elements each having a silver electrode containing silver as a main component on the light-receiving surface side and / or the non-light-receiving surface side, and at least a part of the silver electrode with solder. A solar cell comprising: an inner lead that is connected and electrically connects the plurality of solar cell elements; and a filler that encloses the plurality of solar cell elements and the inner lead therein. It is a module, Comprising: The peripheral part of the said silver electrode is covered with a coating body, and this coating body is comprised so that it may contact with the said filler. By doing so, the peripheral portion of the silver electrode mainly composed of silver is covered with a filler via a covering such as a solder resist instead of being covered with a highly rigid solder, so that stress is relieved. Cheap. Therefore, since the tensile stress applied to the vicinity of the boundary line between the substrate surface of the solar cell element and the silver electrode can be reduced, it is possible to suppress the occurrence of defects such as microcracks in the substrate under the silver electrode. Cracks and cracks can be suppressed. Moreover, it can suppress that a silver electrode peels from a board | substrate. Furthermore, when the inner lead is heat-welded, the peripheral portion of the silver electrode having good wettability with the solder is covered with this covering, so that the solder may flow into the peripheral portion of the silver electrode and cover the peripheral portion. Less is.

  Furthermore, the solar cell module of the present invention is connected to a plurality of solar cell elements each having a silver electrode mainly composed of silver on the light-receiving surface side and / or the non-light-receiving surface side, and to at least a part of the silver electrode by solder. A solar cell module comprising a plurality of solar cell elements and a filler for enclosing the inner leads therein, wherein the silver electrode is a bus bar electrode for taking out the output to the outside, and And a peripheral portion of the bus bar electrode is configured to be in direct contact with the filler.

  In this way, since it is composed of silver having a high thermal conductivity and there is no highly rigid solder at the periphery of the bus bar electrode that is heated when connected to the inner lead, the substrate surface of the solar cell element and the silver Since the tensile stress applied near the periphery of the electrode can be reduced, it is possible to suppress the occurrence of defects such as microcracks in the substrate under the silver electrode, and to suppress cracks and cracks in subsequent processes. become. Moreover, it can suppress that a silver electrode peels from the substrate surface.

  Further, in the solar cell module according to the present invention, the peripheral portion of the bus bar electrode is covered with the covering, and the covering is configured to come into contact with the filler. In addition to being covered with a cover instead of being covered with high-rigidity solder, the peripheral edge of the bus bar electrode that is heated when connected to the inner lead is reduced by the stress around the bus bar electrode, Reflection of cracks generated in the substrate in the vicinity of the electrode can be suppressed.

  In the above solar cell module, it is desirable that the silver electrode includes a bus bar electrode for taking out an output to the outside, and the inner lead is connected to the bus bar electrode. By doing so, the edge portion of the bus bar electrode, which is a silver electrode mainly composed of silver, is covered with the filler directly instead of being covered with the highly rigid solder, or a solder resist or the like Since it is covered with the filler via the covering, stress is easily relieved. Therefore, the tensile stress applied near the boundary line between the substrate surface of the solar cell element and the edge portion of the bus bar electrode can be reduced, so that the occurrence of defects such as microcracks can be suppressed in the substrate under the bus bar electrode. Thus, cracks and cracks in the subsequent process can be suppressed. Further, when the inner lead is thermally welded to the bus bar electrode, if the edge portion of the bus bar electrode is covered with the covering, the solder is less likely to flow into the edge portion of the bus bar electrode and cover the edge portion.

  Furthermore, in the above-described solar cell module, it is preferable that the bus bar electrode connected to the inner lead is formed by covering at least a part of a central portion with respect to the connecting direction of the inner lead with solder. In this way, solder is present particularly at the center of the electrode, specifically at the point to be thermally welded, and is connected to the inner lead, and the connection reliability is further increased.

  In the above solar cell module, it is preferable that the width of the inner lead is narrower than the width of the bus bar electrode in the connecting direction with the inner lead. In this way, when the inner lead is thermally welded to the bus bar electrode, the solder of the inner lead does not easily flow into the edge portion of the bus bar electrode along the connection direction with the inner lead. Therefore, concentration of stress in the vicinity of the boundary line between the edge portion of the bus bar electrode and the substrate surface can be suppressed, and generation of defects such as microcracks in the substrate under the bus bar electrode can be suppressed.

  The solar cell module may further include a plurality of finger electrodes having at least one end connected to the bus bar electrode, and the finger electrodes and the inner leads are not connected by solder. By doing so, the inner lead and the finger electrode are not connected by solder, so that stress concentration between the finger electrode portion and the substrate surface can be suppressed, and the occurrence of defects such as microcracks can be further suppressed. .

  Further, in the above-described solar cell module, the finger electrode is provided with a covering that covers at least the one end, so that when the inner lead is thermally welded to the bus bar electrode, the connection position of the inner lead is Even if it deviates, one end part of a finger electrode is covered with a covering, and it can prevent that a finger electrode and an inner lead are connected with solder. Therefore, concentration of stress between the finger electrode portion and the substrate surface can be suppressed, and generation of defects such as microcracks can be suppressed.

  In the above-described solar cell module, since the covering is made of a solder resist, the stress is easily relieved, and the covering can be formed extremely easily.

  As described above, the solar cell module of the present invention is provided with the bus bar electrode for taking out the output to the outside on the light receiving surface side and / or the non-light receiving surface side of the plurality of solar cell elements, and these solar cell elements. The bus bar electrodes are connected by inner leads and sealed in a filler, and the inner leads and the bus bar electrodes are connected by solder, and the bus bar electrodes are connected to the inner leads. An edge portion along the connecting direction with the lead is in direct contact with the filler, or the edge portion is covered with a covering, and the covering is configured to come into contact with the filler.

  By doing so, the inner lead is connected among the electrodes mainly composed of silver, and the edge portion along the connection direction of the inner lead of the bus bar electrode that is most affected by the welding and the surface of the semiconductor substrate Since the tensile stress applied to the vicinity of the boundary line can be reduced and the concentration of stress can be suppressed, the occurrence of damage such as microcracks can be suppressed in the semiconductor substrate below the bus bar electrode. Therefore, cracks and cracks in the subsequent process are reduced, and the tensile stress near the boundary between the bus bar electrode edge and the semiconductor substrate surface is relaxed, so that cracking in the vicinity of the electrode due to daily temperature cycle stress can be suppressed. it can.

  The solar cell module of the present invention is connected to a plurality of solar cell elements each having a silver electrode mainly composed of silver on the light-receiving surface side and / or the non-light-receiving surface side, and to at least a part of the silver electrode by solder. A solar cell module comprising: an inner lead that electrically connects the plurality of solar cell elements; and a filler that encloses the plurality of solar cell elements and the inner lead therein. And the peripheral part of the said silver electrode is comprised so that it may contact with the said filler directly. Alternatively, the peripheral portion of the silver electrode is covered with a covering, and the covering is configured to come into contact with the filler.

  By doing so, instead of the periphery of the silver electrode mainly composed of silver having a high thermal conductivity and being easily affected by the heating at the time of welding with the inner lead being covered with the rigid solder, Since it is covered with the filler directly or through a covering such as a solder resist, stress is easily relieved. Therefore, the tensile stress applied to the vicinity of the boundary between the peripheral edge of the silver electrode and the semiconductor substrate surface can be reduced, and the stress concentration can be suppressed. The occurrence of damage can be suppressed. Therefore, cracks and cracks in the post process are also reduced, and tensile stress near the boundary between the peripheral edge of the silver electrode and the semiconductor substrate surface is relaxed, so that cracking in the vicinity of the electrode due to daily temperature cycle stress is suppressed. Can do. Furthermore, when using a cover, when the inner lead is heat-welded, the periphery of the silver electrode with good wettability with the solder is covered with this cover, so that the solder flows into the periphery of the silver electrode. Thus, there is also an advantage that there is little risk of covering the peripheral edge.

  Furthermore, the solar cell module of the present invention is connected to a plurality of solar cell elements each having a silver electrode mainly composed of silver on the light-receiving surface side and / or the non-light-receiving surface side, and to at least a part of the silver electrode by solder. A solar cell module comprising a plurality of solar cell elements and a filler for enclosing the inner leads therein, wherein the silver electrode is a bus bar electrode for taking out the output to the outside; And a peripheral portion of the bus bar electrode is configured to be in direct contact with the filler.

  In this way, since it is composed of silver having a high thermal conductivity and there is no highly rigid solder at the periphery of the bus bar electrode that is heated when connected to the inner lead, the substrate surface of the solar cell element and the silver Since the tensile stress applied near the periphery of the electrode can be reduced, it is possible to suppress the occurrence of defects such as microcracks in the substrate under the silver electrode, and to suppress cracks and cracks in subsequent processes. become. Moreover, it can suppress that a silver electrode peels from the substrate surface.

  Further, the peripheral portion of the bus bar electrode is covered with a covering, and if the covering is configured to come into contact with the filler, it is composed of silver having a high thermal conductivity and is heated when connected to the inner lead. Instead of being covered with a highly rigid solder, the peripheral part of the bus bar electrode is covered with a covering, so that stress around the bus bar electrode is reduced, and reflection of cracks generated on the board in the vicinity of the bus bar electrode is suppressed. Can do. Further, when welding the inner lead, the peripheral edge of the bus bar electrode connected to the inner lead is covered with the covering, so that there is less possibility that the solder flows into the peripheral part of the silver electrode and covers the peripheral part. It also has.

It is sectional drawing in the AA line of FIG.3 (c) in one Embodiment of the solar cell element which concerns on the solar cell module of this invention. It is sectional drawing in the AA line of FIG.3 (c) in another embodiment of the solar cell element which concerns on the solar cell module of this invention. (A) is a figure which shows the structure of the cross section of the solar cell element X, (b) is the solar cell module Y comprised combining the solar cell element X of (a), (c) is (b) It is the elements on larger scale of the internal structure of the solar cell module Y of. It is a figure which shows an example of the electrode shape of the solar cell element X, (a) is a non-light-receiving surface side (back surface), (b) is a light-receiving surface side (front surface). (A), (b) is the fragmentary sectional view seen from the DD direction of FIG.4 (b) at the time of connecting an inner lead to the surface side of a solar cell element, and cut | disconnects a surface finger electrode longitudinally in a longitudinal direction The cross-sectional structure on the surface side is shown. (A), (b) is the elements on larger scale of the C section of FIG.4 (b). (A) is sectional drawing in the AA line of FIG.3 (c) in the general solar cell element X, (b) simulated the stress concerning the cross section of the electrode in the B section of (a). It is a deformation mode diagram and a stress vector diagram. It is a figure which shows another example of the electrode shape of the solar cell element which concerns on the solar cell module of this invention, (a) is a non-light-receiving surface side (back surface), (b) is a light-receiving surface side (front surface). (A), (b) is a fragmentary sectional view of the solar cell element used for the solar cell module which concerns on this invention. It is a figure which shows the other example of the electrode shape of the non-light-receiving surface side (back surface) in the solar cell element which concerns on the solar cell module of this invention. (A), (b) is a figure which shows the example of the electrode shape of the solar cell element which concerns on the solar cell module of this invention.

  Hereinafter, the solar cell module of the present invention will be described in detail with reference to the accompanying drawings. Fig.3 (a) is a figure which shows the structure of the cross section of the solar cell element X concerning the solar cell module of this invention. FIG. 4 is a diagram showing an example of the electrode shape, where (a) is the non-light-receiving surface side (back surface) and (b) is the light-receiving surface side (front surface).

  In FIG. 3A, 1 is a p-type silicon substrate which is a semiconductor substrate, 1a is an n-type diffusion layer, 2 is an antireflection film, 3 is a semiconductor junction, 4a is a backside bus bar electrode, and 4b is for backside current collection. Electrodes 5a indicate surface bus bar electrodes.

Here, the manufacturing process of the solar cell element X will be described. First, a p-type semiconductor silicon substrate 1 made of single crystal silicon, polycrystalline silicon, or the like is prepared. This silicon substrate 1 is a substrate containing about 1 × 10 ¹⁶ to 10 ¹⁸ atoms / cm ³ of one conductivity type semiconductor impurity such as boron (B) and having a specific resistance of about 1.0 to 2.0 Ω · cm. A single crystal silicon substrate is formed by a pulling method or the like, and a polycrystalline silicon substrate is formed by a casting method or the like. The polycrystalline silicon substrate can be mass-produced and is more advantageous than the single crystal silicon substrate in terms of manufacturing cost. An ingot formed by a pulling method or a casting method is sliced to a thickness of about 300 μm and cut into a size of about 10 cm × 10 cm or 15 cm × 15 cm to form a silicon substrate 1.

  Thereafter, in order to clean the cut surface of the substrate, the surface is subjected to a very small amount of etching with hydrofluoric acid or hydrofluoric acid.

Next, the silicon substrate 1 is placed in a diffusion furnace, and heat treatment is performed in a gas containing an impurity element such as phosphorus oxychloride (POCl ₃ ) to diffuse phosphorus atoms in the surface portion of the silicon substrate 1 to form a sheet. An n-type diffusion layer 1a having a resistance of about 30 to 300Ω / □ is formed, and a semiconductor junction 3 is formed.

  Then, the n-type diffusion layer 1a is left only on the surface side of the silicon substrate 1 and other portions are removed, followed by washing with pure water. The removal of the n-type diffusion layer 1a other than the surface side of the silicon substrate 1 is performed by applying a resist film to the surface side of the silicon substrate 1, etching away using a mixed solution of hydrofluoric acid and nitric acid, and then removing the resist film. To do.

Further, an antireflection film 2 is formed on the surface side of the silicon substrate 1. The antireflection film 2 is made of, for example, a silicon nitride film, and is formed by, for example, a plasma CVD method in which a mixed gas of silane (SiH ₄ ) and ammonia (NH ₃ ) is plasmatized by glow discharge decomposition and deposited. The antireflection film 2 is formed so as to have a refractive index of about 1.8 to 2.3 in consideration of a refractive index difference with the silicon substrate 1, and has a thickness of about 500 to 1000 mm. . This silicon nitride film has a passivation effect when formed, and has an effect of improving the electrical characteristics of the solar cell together with an antireflection function.

  Then, the front electrode 5 and the back electrode 4 are simultaneously formed by applying a silver paste on the surface of the silicon substrate 1 and applying an aluminum paste and a silver paste on the back surface and baking.

  As shown in FIG. 4A, the back electrode 4 is composed of a back bus bar electrode 4a for extracting output from the back surface and a back current collecting electrode 4b. Further, as shown in FIG. 4B, the surface electrode 5 is composed of a surface bus bar electrode 5a for extracting output from the surface, and a surface finger electrode 5b for current collection provided so as to be orthogonal thereto. The

  The back surface collecting electrode 4b is made of an aluminum paste in which aluminum powder, an organic vehicle, and glass frit are added in a paste form by adding 10 to 30 parts by weight and 0.1 to 5 parts by weight with respect to 100 parts by weight of aluminum. It is baked by printing by a screen printing method and baking at 600-800 degreeC for about 1 to 30 minutes simultaneously after drying. At this time, a back surface electric field layer is formed which prevents aluminum from diffusing into the silicon substrate 1 and recombination of carriers generated on the back surface.

  Also, the back bus bar electrode 4a, the front bus bar electrode 5a, and the front finger electrode 5b are respectively added with 10 to 30 parts by weight and 0.1 to 5 parts by weight of silver powder, organic vehicle and glass frit with respect to 100 parts by weight of silver. The silver paste thus formed into a paste is printed by, for example, a screen printing method, and baked by simultaneously baking at 600 to 800 ° C. for about 1 to 30 minutes after drying. The surface electrode 5 may be formed by etching away a portion corresponding to the electrode of the antireflection film 2 or may be directly formed on the antireflection film 2 by a technique called fire-through.

  After the back bus bar electrode 4a for output extraction is formed, the back current collecting electrode 4b is formed so as not to cover a part of the back bus bar electrode 4a. The order of forming the backside bus bar electrode 4a and the backside current collecting electrode 4b may be reversed. Further, the back electrode 4 does not have the above-described structure, and may be configured by a bus bar electrode mainly composed of silver and finger electrodes similar to the front electrode 5.

  Since a single solar cell element generates a small electrical output, it is necessary to connect a plurality of solar cell elements in series and parallel so that a practical electrical output can be taken out. As an example of the solar cell module, FIG. 3B shows a solar cell module Y configured by combining the solar cell elements X of FIG.

  As shown in FIG. 3B, the plurality of solar cell elements X are electrically connected by the inner leads 8, and an ethylene vinyl acetate copolymer (EVA) is provided between the translucent panel 9 and the back surface protective material 11. The solar cell module Y is configured by being hermetically sealed with a filler 10 containing, for example, the main component. The output of the solar cell module Y is connected to the terminal box 13 via the output wiring 12. FIG. 3 (c) shows a partially enlarged view of the internal structure of the solar cell module Y of FIG. 3 (b).

  As shown in FIG.3 (c), the front surface bus-bar electrode 5a of the solar cell element X1 and the back surface bus-bar electrode 4a of the adjacent solar cell element X2 are connected by the inner lead 8, and several solar cell elements X are connected. Electrically connected. The inner lead 8 is connected to the entire length of the back surface bus bar electrode 4a and the front surface bus bar electrode 5a, a plurality of locations, or partially by heat welding such as hot air, and the solar cell elements X are connected to each other. As the inner lead 8, for example, a copper foil having a thickness of about 100 to 300 μm, which is coated with a solder of about 20 to 70 μm on the entire surface, is cut into a predetermined length.

  In the present invention, the surface of the bus bar electrodes (4a, 5a) of the solar cell element X is not previously coated with solder, but the solder covered with the inner lead 8 is melted, so that the solar cell element X and the inner It is desirable to connect the lead 8.

  FIG. 1 is a cross-sectional view taken along line AA in FIG. Note that, in order to make the configuration easy to understand, the cross-sectional view is drawn with exaggerated dimensions of the main part, which is different from the actual size ratio.

  As shown in this cross-sectional view, in the present invention, the structure is such that the end portion in the longitudinal direction of the back surface bus bar electrode 4a and / or the front surface bus bar electrode 5a, that is, the edge portion along the connection direction with the inner lead contacts the filler 10. It has become. Conventionally, the edge portions of the bus bar electrodes (4a, 5a) are covered with the highly rigid solder 6, but instead, they are covered with the filler 10, so that the stress is easily relieved. Therefore, the tensile stress applied near the boundary between the edge portion of the bus bar electrode (4a, 5a) and the surface of the silicon substrate 1 can be reduced, and the stress concentration can be suppressed, so that the lower portion of the bus bar electrode (4a, 5a) Generation of defects such as microcracks in the silicon substrate 1 can be suppressed, and cracks and cracks in subsequent processes can be suppressed.

  In addition, since stress due to daily temperature cycles when installed outdoors is less likely to concentrate near the electrode, it can be used in the vicinity of the edge along the connection direction of the inner leads of the bus bar electrodes (4a, 5a) even after long-term use. It is possible to suppress the occurrence of cracks.

  In the present invention, the edge portion region along the connecting direction of the inner lead of the bus bar electrode (4a, 5a) that is in direct contact with the filler includes an edge portion of the electrode and a region that is a predetermined length from the edge portion. included. Specifically, it is desirable that the inner region for the predetermined length includes a portion 50 μm inside from the edge portion of the electrode. Note that, as in the case of an electrode formed using a printing and firing method, the edge portion of the electrode becomes thin, and it may be difficult to clearly determine the boundary between the substrate and the electrode. In such a case, a portion where the main component of the outermost surface is the main component of the material forming the electrode may be regarded as the edge portion within the above range. The upper limit value of the edge portion varies depending on the size of the bus bar electrode and is not uniquely determined, but may be set so that the connection strength between the bus bar electrode and the inner lead is sufficiently obtained. For example, in the case of a bus bar electrode (about 2 mm in width) shown in an example described later, the upper limit may be set to 1/4 of this width (500 μm in the case of 2 mm width).

  The bus bar electrodes (4a, 5a) are preferably covered with the solder 6 at least at a part of the central portion in the connecting direction of the inner leads. For example, the central portion of the bus bar electrodes (4a, 5a) may be covered in advance with solder, or when connected by the inner lead 8, the central portion with the electrode may be welded. In this way, the solder 6 is always present at the center of the bus bar electrodes (4a, 5a) and is connected to the inner lead 8, so that the connection reliability is improved.

  Usually, in order to extract the output to the outside of the electrode part of the solar cell element or maintain the durability of the electrode, it is often the case that the solder is coated in advance by a dip method, a jet type, etc. It is not necessary to coat the electrode part of the solar cell element X of the solar cell module with solder.

  Further, even when the solder is covered, as shown in FIG. 1, the edge portions of the back bus bar electrode 4 a and / or the front bus bar electrode 5 a of the solar cell element X may not be covered with the solder 6. is necessary. As an example of the method, for example, the flux is applied to the central portion of the back surface bus bar electrode 4a and / or the front surface bus bar electrode 5a and the flux is not applied to the end portion, thereby the center of the bus bar electrodes (4a, 5a). The structure of the present invention can be obtained in which the portion is covered with the solder 6 and the end portion is not covered with the solder 6.

  Next, FIG. 2 shows another embodiment according to the present invention. 2 also shows a cross-sectional view taken along the line AA of FIG. In this embodiment, the edge part along the connection direction with the inner lead of the back surface bus bar electrode 4a and / or the front surface bus bar electrode 5a is an example of the covering 7 and the filler 10 with the solder resist interposed therebetween. It is configured to come into contact. In this way, it is in contact with the filler 10 through the covering 7, and as described above, instead of the edge portion of the bus bar electrodes (4 a, 5 a) being covered with the rigid solder 6, Covered with a filler 10. Therefore, stress concentration in the vicinity of the boundary line can be reduced and suppressed, and damage such as microcracks can be suppressed in the silicon substrate 1 below the bus bar electrodes (4a, 5a).

  Such a covering 7 is provided in advance, and then the solder-coated inner leads 8 are thermally welded to the bus bar electrodes (4a, 5a), so that even if the solder 6 flows from the inner leads 8 side, the bus bar electrodes (4a 5a) can be prevented from being covered.

  Also, if the edge of each of the back bus bar electrode 4a and / or the front bus bar electrode 5a of the solar cell element X is coated and cured in advance with the covering 7 applied, the solder is coated by a dipping method, a jet type, etc. The edge part of a bus-bar electrode (4a, 5a) can be made into the structure where the solder 6 does not cover.

  Such a covering 7 is preferably made of a heat-resistant resin because heat is applied in the step of forming the solar cell module. Among them, if a solder resist is used, stress is easily relieved, It is desirable because the covering 7 having a predetermined shape can be formed very easily by printing, photolithography, or the like and has resistance to solder. As the solder resist, for example, an epoxy-based organic curable resin is used, and the organic curable resin includes an ultraviolet curable type and a thermosetting type, and any of them may be used.

  As described above, the solar cell module of the present invention can be realized.

  If the width of the inner lead 8 is made narrower than the width of the rear bus bar electrode 4a and / or the front bus bar electrode 5a, the bus bar electrode is formed when the inner lead 8 is thermally welded to the bus bar electrodes (4a, 5a). The ends of (4a, 5a) can be made hard to be covered with the solder of the inner lead 8.

  Next, a preferable aspect is demonstrated about the solar cell module of this invention.

  The solar cell module of the present invention has a plurality of surface finger electrodes 5b having at least one end connected to the surface bus bar electrode 5a as described in FIG. 4B. It is desirable to prevent 5b and the inner lead 8 from being connected by solder.

  FIG. 5 is a partial cross-sectional view seen from the DD direction of FIG. 4B when the inner lead 8 is connected to the surface side of the solar cell element, and the surface side of the surface finger electrode 5b vertically cut in the longitudinal direction. The inner lead 8 is shifted to the left when viewed from the front of the figure.

  As shown in FIG. 5A, the solder 6 that electrically connects the inner lead 8 and the electrode of the solar cell element exists between the inner lead 8 and the surface bus bar electrode 5a. And the surface finger electrode 5b are not connected by solder. Depending on the positioning accuracy of the device (tab attaching device) for connecting the inner leads 8 with solder, the inner leads 8 may often protrude above the surface finger electrodes 5b as described above. As described above, if the inner lead 8 and the surface finger electrode 5b are not connected to each other by solder, the concentration of stress between the surface finger electrode 5b and the surface of the silicon substrate 1 can be suppressed, and the micro Generation of defects such as cracks can be suppressed.

  Even if the inner lead 8 is covered with solder or solder is attached to the surface finger electrode 5b, the effect of the present invention can be obtained if they are not connected to each other by solder. Specifically, in this region E, the inner lead 8 and the surface finger electrode 5b are simply in contact with each other (without being connected by solder), or separated by a predetermined distance determined by the shape and arrangement state of each member. It has become a state. In the step of hermetically sealing with the filler 10 when the solar cell module is formed, the solar cell module may be separated via the filler 10 such as EVA that has flowed in.

  In order to prevent the inner leads 8 and the surface finger electrodes 5b from being connected to each other by soldering in this way, for example, when a plurality of solar cell elements are melted by the inner leads 8 and soldered together. The flux may be applied to the surface bus bar electrode 5a to be connected in advance and the flux may not be applied to the surface finger electrode 5b. Where the flux is applied, the surface is activated by heating and the oxide film is removed to improve the wettability with the solder. However, in the silver constituting the surface finger electrode 5b, the surface oxide film is removed if there is no flux. It cannot be done and the wettability with solder is bad. Therefore, if the flux is not applied to the surface finger electrode 5b, the configuration of the present invention in which the inner lead 8 and the surface finger electrode 5b are not connected to each other by solder can be easily obtained. . In particular, a so-called solderless solar cell element in which the electrode surface is not coated with solder has a clear effect.

  Further, as shown in FIG. 5B, a covering 14 is provided to cover one end of the surface finger electrode 5b connected to the surface bus bar electrode 5a, and the inner lead 8 and the surface finger electrode 5b are soldered to each other. You may make it obtain the structure of this invention which is not connected.

  FIG. 6 shows a partially enlarged view of a portion C in FIG. As shown in FIG. 6 (a), one end of the surface finger electrode 5b connected to the surface bus bar electrode 5a may be covered with a covering body 14, and as shown in FIG. 6 (b), the covering body 14 is covered. 'May cover the longitudinal end of the front bus bar electrode 5a and the end of the front finger electrode 5b connected to the front bus bar electrode 5a at the same time.

  By providing such a covering 14, even when the inner lead 8 is thermally welded to the surface bus bar electrode 5 a, even if the connection position of the inner lead 8 is shifted as shown in the figure, the surface finger electrode is formed by this covering 14. Since one end of 5b is covered, it is possible to prevent the surface finger electrode 5b and the inner lead 8 from being connected by solder. Therefore, the concentration of stress between the surface finger electrode 5b and the surface of the substrate 1 can be suppressed, and the occurrence of defects such as microcracks can be suppressed.

  The covering 14 is preferably made of a heat-resistant resin because heat is applied in the process of forming the solar cell module. Among them, the surface finger electrode 5b is covered with the solder resist when a solder resist is used. 14 and covered with a filler. As a result, it is desirable because stress is easily relieved, and a covering with a predetermined shape can be formed very easily by printing, photolithography, or the like, and resistance to solder is provided. Further, when forming the covering body 14 'in the shape shown in FIG. 6B, it can be formed simultaneously with the solder resist detailed in the description of FIG. 2, so the number of steps can be reduced and the cost can be reduced. This is also desirable.

  Further, it is desirable that the area where the coverings 14 and 14 'are provided be within a range of 5 mm or less from one end where the surface finger electrode 5b is connected to the surface bus bar electrode 5a. This is because exceeding this range, the effect of blocking the light irradiation region and lowering the conversion efficiency becomes remarkable. As for the lower limit, the range of positioning accuracy of the device (tab attaching device) for connecting the inner leads 8 with solder, that is, the range in which the inner leads 8 may be displaced and be sure to cover with the covering. What is necessary is just to set a lower limit.

  As described above, the finger electrode according to the solar cell module of the present invention described with reference to FIGS. 5 and 6 has been described limited to the front surface side, but silver is mainly used on the back surface side as well as the front surface side electrode. The structure may include a bus bar electrode and a finger electrode as components, and the finger electrode and the inner lead may not be connected by solder in the same manner as the surface side.

  Next, another aspect of the solar cell module of the present invention will be described.

  FIG. 8 is a schematic view showing an example of a solar cell element according to the solar cell module described in claim 3 or claim 4 of the present invention, (a) is an example of the non-light-receiving surface side (back surface), (B) shows an example of the light receiving surface side (surface). 9A and 9B show a cross-sectional structure in a state where the inner leads are connected to the solar cell element shown in FIG. 8 by soldering.

  In the example shown in the drawing, bus bar electrodes 24a and 25a and finger electrodes 25b are formed on the surface of the silicon substrate 21 as silver electrodes mainly composed of silver, and fillers 28 are formed on the peripheral portions 24c and 25c of these silver electrodes. A region that is directly in contact with the filler 28 (see FIG. 9A) or a region that is covered with the filler 28 via a covering 27 such as a solder resist (see FIG. 9B) is formed.

  As shown in the cross-sectional view of FIG. 9, in the present invention, the peripheral portions (24 c, 25 c) of the silver electrodes (24 a, 25 a, 25 b) mainly composed of silver are in contact with the filler 28. Conventionally, for example, as shown in FIG. 7, this region is covered with the highly rigid solder 26, but instead, it is covered with the filler 28, so that the stress is easily relieved. Therefore, the tensile stress applied to the vicinity of the boundary line between the peripheral portions 24c and 25c of the silver electrode and the surface of the silicon substrate 21 can be reduced, and the concentration of stress can be suppressed. Generation of defects can be suppressed, and cracks and cracks in subsequent processes can be suppressed.

  In addition, when installed outdoors, stress due to daily temperature cycles is less likely to concentrate near the edge of the electrode, so that cracking in the vicinity of the silver electrode can be suppressed when used for a long period of time.

  In this way, in order to obtain a structure in which the peripheral portions (24c, 25c) of the silver electrodes (24a, 25a, 25b) are in direct contact with the filler 28, for example, in the central portion of the silver electrodes 24a, 25a, 25b The present invention applies the flux and does not apply the flux to the peripheral portions 24c, 25c, so that the central portions of the silver electrodes 24a, 25a, 25b are covered with solder, and the peripheral portions 24c, 25c are not covered with solder. The structure can be In addition, in order to have a structure in which the peripheral portions (24c, 25c) of the silver electrodes (24a, 25a, 25b) are covered with the covering body 27 in direct contact with the filler 28, the covering body 27, for example, a solder resist or the like is previously used. What is necessary is just to coat | cover solder in the state apply | coated and hardened on this area | region. The covering body 27 is preferably made of a heat-resistant resin because heat is applied in the step of forming the solar cell module. Furthermore, it is desirable to use a solder resist because a covering with a predetermined shape can be formed very easily by printing, photolithography, or the like and has resistance to solder.

  The bus bar electrodes 24a and 25a according to the present embodiment are electrodes connected to the inner lead 30, and are not affected by the shape or number of the electrodes. FIG. 10 is a view showing a modification of the non-light-receiving surface side (back surface) in the solar cell element according to this embodiment. As shown in FIGS. 10A and 10B, the effect of the present invention can be effectively exhibited even with a rectangular dot-shaped busbar electrode. In addition to a rectangle, a shape such as a polygon, an ellipse, or a circle may be used. Further, as shown in FIG. 10 (c), even if the electrode shape is provided with a protruding portion protruding from the line portion and the comb teeth are deformed, the electrode portion connected to the inner lead 30 is regarded as a bus bar electrode. If the peripheral portions 24c and 25c of the bus bar electrodes 24a and 25a are covered with the filler 28 directly or via the covering 27, it can be considered as the configuration of the present invention. For example, in the case of FIG. 10C, if the portion connected to the inner lead 30 is a line portion, the line portion only needs to have the structure of the bus bar electrode according to the present invention, and the inner lead 30 is formed in the protruding portion. If it connects, the protrusion part should just have the structure of the bus-bar electrode which concerns on this invention. Also, the number is not limited to the two (set) shown in the figure, and may be one (set), three (set) or more.

  Note that, in the bus bar electrode according to the present embodiment, the peripheral portions 24c and 25c of the bus bar electrodes 24a and 25a that are in direct contact with the filler include an edge portion of the electrode and an inner region by a predetermined length from the edge portion. included. Specifically, it is desirable that the inner region for the predetermined length includes a portion 50 μm inside from the edge portion of the electrode. Note that, as in the case of an electrode formed using a printing and firing method, the edge portion of the electrode becomes thin, and it may be difficult to clearly determine the boundary between the substrate and the electrode. In such a case, a portion where the main component of the outermost surface is the main component of the material forming the electrode may be regarded as the edge portion within the above range. The upper limit value of the edge portion varies depending on the size of the bus bar electrode and is not uniquely determined, but may be set so that the connection strength between the bus bar electrode and the inner lead is sufficiently obtained. For example, in the case of a bus bar electrode (about 2 mm in width) shown in an example described later, the upper limit may be set to 1/4 of this width (500 μm in the case of 2 mm width).

  The embodiment of the present invention is not limited to the above example, and various modifications can be made without departing from the scope of the present invention.

  For example, in the above description, one end portion of the surface finger electrode 5b is connected to the surface bus bar electrode 5a in a substantially orthogonal manner, but may be connected from an oblique direction without being orthogonal, Further, both end portions of the surface finger electrode 5b may be connected to the surface bus bar electrode 5a to have a closed shape.

  Furthermore, in the above description, the finger electrode is described as the surface finger electrode 5b provided on the light receiving surface side of the solar cell element, but the present invention is not limited to this, and the finger electrode referred to in the present invention is an inner lead and It refers to a current collecting electrode connected to the bus bar electrode to be connected, and may be provided on the non-light receiving surface side. Further, the number and shape of the finger electrodes are not limited to the above description. FIG. 11 shows an example of finger electrodes and bus bar electrodes provided on the light receiving surface side. For example, as shown in FIG. 11 (a), the length of the finger electrodes connected to the two bus bar electrodes may be shorter than the bus bar electrodes, or a plurality of bus bar electrodes as shown in FIG. 11 (b). The shape may be orthogonal to the shape. Further, it may be connected to the bus bar electrode by forming an acute angle or an obtuse angle without being orthogonal to the bus bar electrode. Further, the shape of the finger electrode is not limited to a linear shape, and may be a curved shape.

  In the above description, the solar cell using the p-type silicon substrate has been described. However, when the n-type silicon substrate is used, the effect of the present invention can be obtained by the same process if the polarity in the description is reversed. be able to. Further, in the above description, the case of single junction has been described, but the present invention can be applied even to a multi-junction type formed by laminating a thin film junction layer made of a semiconductor multilayer film on a junction element using a bulk substrate. it can.

  In the above description, the polycrystalline silicon substrate using the casting method is taken as an example. However, the substrate need not be limited to the one based on the casting method, and need not be limited to polycrystalline silicon. Moreover, it is not limited to a semiconductor substrate, A semiconductor thin film may be sufficient. Further, the present invention is not limited to silicon materials and can be applied to general semiconductors. That is, the present invention can also be applied to compound-based and organic-based solar cells.

  Examples of the present invention will be described below.

As shown in FIG. 3A, the damage layer on the surface of the polycrystalline p-type silicon substrate 1 having an outer shape of 15 cm × 15 cm and a resistance of 1.5 Ω · cm was etched and washed with alkali. Next, the silicon substrate 1 is placed in a diffusion furnace and heated in phosphorus oxychloride (POCl ₃ ), thereby bringing phosphorus atoms into the surface of the silicon substrate 1 at a concentration of 1 × 10 ¹⁷ atoms / cm ³ . The n-type diffusion layer 1a was formed by diffusion. A silicon nitride film having a thickness of 850 mm to be the antireflection film 2 was formed thereon by plasma CVD.

  In order to form the back surface collecting electrode 4b on the back surface side of the silicon substrate 1, 20 parts by weight and 3 parts by weight of aluminum powder, an organic vehicle, and glass frit are added to 100 parts by weight of aluminum, respectively, to form a paste. The aluminum paste prepared was applied by screen printing and dried. Then, in order to form the back surface bus bar electrode 4a on the back surface side and the surface electrode 5 (surface bus bar electrode 5a, surface finger electrode 5b) on the front surface side, silver powder, organic vehicle and glass frit are added to 100 parts by weight of silver. Silver paste made into a paste form by adding 20 parts by weight and 3 parts by weight, respectively, was applied by screen printing and dried. Thereafter, baking was performed at 750 ° C. for 15 minutes, and the front bus bar electrode 5a and the back bus bar electrode 4a were each 2 mm in width, and electrodes were simultaneously formed on the front and back surfaces.

  Here, Sample No. 1, a solder resist is printed as a covering 7 on the end portion of the surface bus bar electrode 5a and dried, and the electrode is coated with the solder 6 by a dipping method, and the solar cell element according to the solar cell module of the present invention is applied. Formed. Sample No. No. 2, without using the solder resist coating 7, the entire surface of the electrode was similarly coated by the dipping method to form the conventional solar cell element shown in FIG. The solder used was Sn-3Ag-0.5Cu Pb-free solder.

  Sample No. 3 without using the solder resist covering 7, and applying the solder paste to the central portion of the bus bar electrodes (4 a, 5 a) only in the longitudinal direction using a dispenser, and producing the covering with the solder 6. A solar cell element according to the battery module was produced.

  Furthermore, sample no. Samples in which the electrodes were not covered with the solder 6 as 4 and 5 were also prepared.

  Next, an inner lead 8 made of copper foil having a width of 1.8 mm and a thickness of 200 μm provided with a solder layer having a thickness of about 30 μm is bonded by hot air thermal welding over the entire length of each bus bar electrode (4a, 5a). In addition, the above-described solar cell elements were connected and wired. At this time, sample no. In 3 and 4, only the central part of the inner lead 8 was fixed by thermal welding. Sample No. No. 5 has a width of the inner lead 8 larger than the width of the electrode to be connected to 2.2 mm, and the entire surface is thermally welded to the electrode.

  Thereafter, as shown in FIG. 3B, the solar cell elements connected and wired as described above are used as a filler 10 between EVA (ethylene vinyl) between the translucent panel 9 and the back surface protective material 11. A solar cell module having the cross-sectional structure shown in FIG. 2 was formed by encapsulating with an acetate copolymer.

About these solar cell elements, the breaking strength test by 4-point bending was done, and breaking strength (N) was calculated | required. Moreover, the microcrack generation rate of the solar cell element enclosed in the static load test which applies the pressure of 3000 N / m < ² > in a solar cell module was investigated. The microcrack occurrence rate is examined using a binocular microscope with a magnification of 40 times, and the number of solar cell elements X in which microcracks have occurred with respect to the total number of solar cell elements X of all solar cell modules Y used in the static load test. It is shown as a percentage.

  These results are shown in Table 1.

  Sample No. 1 is a sample of the present invention in which a solder resist coating 7 is interposed between the longitudinal end portion of the surface bus bar electrode 5a and EVA as the filler 10, and the fracture strength is 25 N and the microcrack occurrence rate is 0. %, Confirming the effect of the invention.

    On the other hand, sample No. No. 2 of the present invention is that the ends of all the bus bar electrodes (4a, 5a) are covered with the solder 6 and are not in contact with EVA as the filler 10 directly or via the solder resist covering 7. The sample was out of range. The fracture strength was 15 N and the microcrack occurrence rate was 50%, which was an unsatisfactory result.

  Sample No. 3, the solder 6 is coated only on the central portion of the bus bar electrodes (4 a, 5 a), and the central portion of the inner lead 8 is welded. As a result, the completed solar cell module has an electrode end portion and a filler 10. It is the form which concerns on this invention which contacted directly. In this case, the breaking strength of the solar cell element was 23 N and the microcrack occurrence rate was 0%, confirming the effects of the invention.

  Sample No. 4 is a sample in which the solder 6 is not coated on the bus bar electrodes (4a, 5a), and the solar cell completed as a result of welding the central portion of the inner lead 8 using the solder coated on the inner lead 8 The module has a configuration according to the present invention in which the end of the electrode and the filler 10 are in direct contact. In this case, the breaking strength of the solar cell element was 24 N, and the microcrack occurrence rate was 0%, confirming the effects of the invention.

  Sample No. 5 is a sample in which the solder 6 is not coated on the bus bar electrodes (4a, 5a), but the entire surface was welded with hot air using an inner lead 8 having a width of 2.2 mm larger than the width of the bus bar electrodes (4a, 5a). However, the solder 6 was coated on the end portions of the bus bar electrodes (4a, 5a), and the end portions of the electrodes and the filler 10 did not come into contact with each other. As a result, the fracture strength was 15 N and the microcrack occurrence rate was 40%, which was an unsatisfactory result.

  Thus, according to the present invention, the end of the bus bar electrodes (4a, 5a) is not covered with the solder 6, and is configured to be in contact with the filler 10 directly or via the solder resist covering 7 Confirms that stress concentration near the boundary between the end of the busbar electrode and the substrate surface can be suppressed, which increases the fracture strength and suppresses the occurrence of microcracks in the substrate under the busbar electrode. did.

  The solar cell element shown in FIG. 3A was formed in exactly the same manner as in Example 1. Thereafter, a solder resist is printed and applied in a pattern shown in FIG. 6 (b) to the finger electrode side region from one end where the surface finger electrode 5b is connected to the surface bus bar electrode 5a to a thickness of 1 mm. 14 'was formed. Thereafter, the inner leads 8 in which the solder was coated on the copper foil were thermally welded. At this time, the position of the inner lead 8 was intentionally shifted to cause the inner lead 8 to protrude from the surface bus bar electrode 5a and to intentionally connect them with solder, but the sample provided with the solder resist covering 14 ' Was not connected to each other in any way. Moreover, about the sample which does not provide a coating body, when the flux was apply | coated to the surface finger electrode 5b, it connected mutually. As the solder for the copper foil, Sn-3Ag-0.5Cu Pb-free solder is used.

  The samples thus prepared were evaluated based on the microcrack occurrence rate described in Example 1. The results are shown in Table 2.

  As shown in Table 2, Sample No. 6 and 7 are cases in which the inner lead 8 is not displaced from the surface bus bar electrode 5a, and a solder connection occurs between the inner lead 8 and the surface finger electrode 5b regardless of the presence or absence of the solder resist coating 14 '. No cracks occurred.

  When the inner lead 8 is displaced by 0.3 mm toward the surface finger electrode 5b (sample No. 8 to 10), when the solder resist coating 14 'is provided (sample No. 8), the inner lead 8 There was no solder connection between the surface finger electrode 5b and the surface finger electrode 5b, and no cracks occurred. When there is no solder resist coating 14 ', when a flux is applied to the surface finger electrode 5b to intentionally generate a solder connection with the inner lead 8 (sample No. 9), microcracks The occurrence rate was 30%, but when no flux was applied (sample No. 10), no connection by solder was generated between the inner lead 8 and the surface finger electrode 5b, and no crack was generated.

  When the inner lead 8 is shifted by 0.3 mm toward the surface finger electrode 5b (sample No. 11 to 13), when the solder resist coating 14 'is provided (sample No. 11), the inner lead 8 There was no solder connection between the surface finger electrode 5b and the surface finger electrode 5b, and no cracks occurred. When there is no solder resist coating 14 ', when a flux is applied to the surface finger electrode 5b to intentionally generate a solder connection with the inner lead 8 (sample No. 12), microcracks Although the occurrence rate was 50%, when no flux was applied (sample No. 13), no connection by solder was generated between the inner lead 8 and the surface finger electrode 5b, and no crack was generated.

1: Silicon substrate 1: Substrate 1a: N-type diffusion layer 2: Antireflection film 3: Semiconductor junction 4: Back electrode 4a: Back bus bar electrode 4b: Back current collecting electrode 5: Front electrode 5a: Front bus bar electrode 5b: Surface finger electrode 6: Solder 7: Cover (for example, solder resist)
8: Inner lead 9: Translucent panel 10: Filler 11: Back surface protective material 12: Output wiring 13: Terminal box 14, 14 ': Cover 21: Silicon substrate 24: Back electrode 24a: Bus bar electrode 24b: Collector 24c: Peripheral part 25: Surface electrode 25a: Bus bar electrode 25b: Finger electrode 25c: Peripheral part 26: Solder 27: Covering body 28: Filler X, X1, X2, X3: Solar cell element Y: Solar cell module

Claims (18)

A first solar cell element;
A second solar cell element adjacent to the first solar cell element;
A light-receiving surface and / or a non-light-receiving surface of the first solar cell element, and a bus bar electrode provided on the non-light-receiving surface and / or the light-receiving surface of the second solar cell element;
An inner lead that electrically connects the bus bar electrodes of the first and second solar cell elements;
A solar cell module having a filler encapsulating the inner lead and the bus bar electrode,
The bus bar electrode is
A first region to which the inner lead is connected;
Including a second region that includes an edge portion along a longitudinal direction of the bus bar electrode, and is positioned closer to the edge portion than the first region;
The solar cell module in which the second region is in direct contact with the filler. Further comprising solder interposed between the bus bar electrode and the inner lead,
The solar cell module according to claim 1, wherein the second region is exposed from the solder.   2. The edge portion of the bus bar electrode is located outward from an edge portion of the inner lead located on the same side as the edge portion in a cross section orthogonal to the longitudinal direction. Or the solar cell module of Claim 2.   4. The solar cell module according to claim 1, wherein a width of the inner lead in a direction orthogonal to the longitudinal direction is smaller than a width of the bus bar electrode in a direction orthogonal to the longitudinal direction.   5. The device according to claim 2, further comprising a plurality of finger electrodes having at least one end connected to the bus bar electrode, wherein the finger electrodes and the inner lead are not connected by the solder. The solar cell module according to.   The solar cell module according to claim 5, wherein the finger electrode includes a covering that covers at least the one end.   The solar cell module according to claim 6, wherein the covering is a solder resist.   The solar cell module according to claim 1, wherein the bus bar electrode contains silver as a main component.   The solar cell module according to any one of claims 1 to 8, wherein the filler is made of a polymer. A solar cell element;
A bus bar electrode provided on the light receiving surface and / or the non-light receiving surface of the solar cell element;
An inner lead electrically connected to the bus bar electrode;
An encapsulant for encapsulating the bus bar electrode and the inner lead, and a solar cell element structure,
The bus bar electrode is
A first region connected to the inner lead;
Including a second region that includes an edge portion along a longitudinal direction of the bus bar electrode, and is positioned closer to the edge portion than the first region;
The second region is a solar cell element structure in direct contact with the encapsulant. Further comprising solder interposed between the bus bar electrode and the inner lead,
The solar cell element structure according to claim 10, wherein the second region is exposed from the solder.   11. The edge portion of the bus bar electrode is located outward from an edge portion of the inner lead located on the same side as the edge portion in a cross section orthogonal to the longitudinal direction. Or the solar cell element structure of Claim 11.   13. The solar cell element structure according to claim 10, wherein a width of the inner lead in a direction orthogonal to the longitudinal direction is smaller than a width of the bus bar electrode in a direction orthogonal to the longitudinal direction. body.   14. The device according to claim 11, further comprising a plurality of finger electrodes having at least one end connected to the bus bar electrode, wherein the finger electrodes and the inner leads are not connected by the solder. The solar cell element structure according to 1.   The solar cell element structure according to claim 14, wherein the finger electrode includes a covering that covers at least the one end.   The solar cell element structure according to claim 15, wherein the covering is a solder resist.   The solar cell element structure according to claim 10, wherein the bus bar electrode contains silver as a main component.   The solar cell element structure according to any one of claims 10 to 17, wherein the encapsulant is made of a polymer.

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