JP2006013173A - Solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a solar cell module with high efficiency by avoiding an influence of an increase in the resistance of a collector even when the area of a solar cell element is increased. <P>SOLUTION: A main tab 9a electrically connects a front-side main electrode 7a of a solar cell element X1 and a back-side main electrode 6 of a solar cell element X2 which is adjacent to the solar cell element X1 to each other. A sub-tab 9b is provided so that it is shorter than the main tab 9a and smaller in number, and electrically connects the remaining front-side main electrode 7a of the solar cell elements X1 where main tabs 9a are not connected and the remaining back-side main electrode 6 of the solar cell elements X2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solar cell module in which solar cell elements are arranged at predetermined intervals, and an output and a tab (lead wire) for taking out the output from the solar cell elements and electrically connecting the solar cell elements to each other. ).

  A solar cell converts incident light energy into electrical energy. Major solar cells are classified into crystalline, amorphous, and compound types depending on the type of materials used. Of these, most of the crystalline silicon solar cells currently on the market are in the market. This crystalline silicon solar cell is further classified into a single crystal type and a polycrystalline type. Single-crystal silicon solar cells have the advantage that the substrate quality is good and the efficiency can be easily increased, but the substrate is expensive to manufacture. On the other hand, the polycrystalline silicon solar cell has the advantage that it can be manufactured at a low cost although it has the disadvantage that it is difficult to increase the efficiency because the quality of the substrate is inferior. In recent years, conversion efficiency of about 18% has been achieved at the research level due to the improvement of the quality of the polycrystalline silicon substrate and the advancement of cell technology.

  On the other hand, mass-produced polycrystalline silicon solar cells have been distributed in the market because of their low cost. However, in recent years, demand has increased further as environmental issues have been addressed, resulting in higher conversion efficiency at lower costs. Is now required.

The general structure of the solar cell element described in Patent Document 1 is shown in FIG. 8A is a diagram showing a cross-sectional structure, FIG. 8B is a diagram viewed from the front surface (light receiving surface), and FIG. 8C is a diagram viewed from the back surface (non-light receiving surface). 101 is, for example, a p-type silicon semiconductor substrate, 102 is a reverse conductivity diffusion region in which phosphorus atoms and the like are diffused at a high concentration on the surface side of the semiconductor substrate 101, and a pn junction is formed with the semiconductor substrate 101, and 103 is a nitride It is an antireflection film made of a silicon film, a silicon oxide film, or the like. Further, a front side electrode 107 including a front side main electrode 107a and a front side collector electrode 107b is provided on the front side of the semiconductor substrate 101, and a p ⁺ region containing a large amount of p-type semiconductor impurities such as aluminum is provided on the back side. The back surface electric field area | region 104, the back side collector electrode 105 which consists of aluminum, and the back side main electrode 106 which has silver as a main component are provided.

  As shown in FIG. 8B, the front side electrode 107 forms a thin front side collecting electrode 107b from the front side main electrode 107a in order to efficiently pick up current from the surface of the solar cell element. Since it is advantageous to make the electrical resistance of the front side collector electrode 107b as small as possible, the front side main electrode 107a and the front side collector electrode 107b are generally formed in a lattice form at right angles. And these are formed by baking after apply | coating silver paste etc. by the screen-printing method. Further, the front side electrode 107 is formed by etching away a portion corresponding to the electrode of the antireflection film 103 and forming the front side electrode 107 in this portion, or by baking the front side electrode 107 directly from above the antireflection film 103. May form.

As shown in FIG. 8C, the non-light-receiving surface side is coated with a metal paste containing aluminum powder by a screen printing method or the like and then baked at 700 to 800 ° C. Aluminum is diffused therein to form a back surface electric field region 104 which is a p ⁺ region containing a large amount of p-type semiconductor impurities. The back surface electric field region 104 has an effect of preventing the generated carriers from recombining at the non-light receiving surface.

  The back surface electric field region 104 is often formed on substantially the entire back surface of the semiconductor substrate 1, and at the same time, the back surface collecting electrode 105 mainly composed of aluminum or the like that has not diffused into silicon is formed. It is often left on the light receiving surface and used as a part of the back electrode. Although it is necessary to connect a tab to the non-light-receiving surface, an electrode formed by firing this aluminum paste is very fragile, and it is difficult to obtain a sufficient adhesion strength even when connected. Therefore, usually, there is a method of forming a back side main electrode 106 by printing and baking a metal paste containing, for example, silver powder, which has better solder wettability than aluminum on the non-light-receiving surface, and connecting a tab to this portion. It is done.

  The surfaces of the front-side electrode 107 and the back-side main electrode 106 mainly composed of silver produced as described above may be coated with solder in order to prevent silver oxidation and improve connectivity. Many.

  By the back surface electric field region 104 described above, carriers generated in the solar cell element can be efficiently collected by the electric field effect (BSF effect), and the conversion efficiency of the solar cell element can be improved.

  In general, since one solar cell element generates a small electrical output, it is necessary to connect a plurality of solar cell elements in series and parallel to form a solar cell module so that a practical electrical output can be taken out. As an example of the solar cell module, FIG. 7 shows a general solar cell module configured by combining solar cell elements X.

  As shown in FIG. 7, a front electrode of a certain solar cell element and a back electrode of an adjacent solar cell element are soldered and electrically connected by a tab 9 made of, for example, copper foil. Then, the solar cell module is hermetically sealed with a filler 11 mainly composed of ethylene vinyl acetate copolymer (EVA) or the like between the translucent panel 10 made of glass or the like and the back surface protective material 12. It is composed. The output of the solar cell module is connected to the terminal box 14 via the output wiring 13. The terminal box is further connected to an external load.

FIG. 9 is a diagram showing a state where two solar cell elements X are connected by the tab 9. FIG. 9 is a view of two adjacent solar cell elements X arranged side by side, as viewed from the back side. FIG. 9A is before tab connection, and FIG. 9B is after tab connection. For the sake of explanation, the left side solar cell element X is in a state where the front side main electrode 107a can be seen through the solar cell element X, and the front side collecting electrode 107b and the back side electrode are omitted. As shown in the figure, the front-side main electrode 107a of one solar cell element and the back-side main electrode 106 of the other solar cell element are solder-connected by a tab 9 so as to be covered. Thus, the front side main electrode 107 a and the back side main electrode 106 are both linear and are connected to each other by the tab 9.
JP-A-8-274356

  Most electrodes of solar cell elements currently on the market are formed by screen printing and firing for cost reasons. For example, in the case of a solar cell element having a size of 10 cm × 10 cm as an electrode by screen printing, it usually has two main electrodes. In the case of the light-receiving surface side, as shown in FIG. 8B, a plurality of front-side collector electrodes 107b that intersect with the two front-side main electrodes 107a substantially at right angles are provided so as to cover the entire surface of the solar cell element. Yes.

  In recent years, the demand for cost reduction has increased, and an increase in the area of solar cell elements has been studied. The reason is that if the area is increased, the current value of the output of the solar cell that can be produced when the same number is produced can be increased. However, when the area of the solar cell element is increased, the length of the collector electrode is increased and the electric resistance is increased.

  Further, in order to improve the efficiency of the solar cell element, it is advantageous to make the collector electrodes formed on the light receiving surface side as thin as possible in order to reduce the loss of incident light. However, if the collector electrode is made thinner, the electrical resistance increases. However, in the case of electrode formation by screen printing, it is difficult to increase the thickness of the electrode to compensate for the increased electrical resistance.

  Thus, in order to improve the efficiency of the solar cell module, when the area of the solar cell element is increased or the collector electrode is thinned, the resistance of the collector electrode increases and the characteristics deteriorate. There is a technical limit to reducing the resistance. Therefore, in a normal solar cell element, a compromise has been found between the area of the solar cell element and the width of the collector electrode so that the resistance of the collector electrode does not greatly deteriorate the characteristics of the element. It has been decided.

  In order to avoid the influence of the increase in resistance of the collector electrode, the inventor has studied a method of reducing the resistance by reducing the distance between the collector electrodes by increasing the number of main electrodes. However, if the number of main electrodes is increased, it takes much time to form solar cell modules by connecting solar cell elements with tabs, and further increases the amount of material used, which increases costs. There was a problem.

  In view of the above, an object of the present invention is to provide a solar cell module that suppresses the labor and cost of connection when connecting solar cell elements having an increased number of main electrodes.

  A solar cell module according to claim 1 of the present invention is a plurality of solar cell elements having a light receiving surface and a non-light receiving surface, arranged at a predetermined interval, and provided on the light receiving surface side. A front-side electrode including a front-side collector electrode for collecting the output and three or more linear front-side main electrodes for connecting the front-side collector electrode and extracting output to the outside, and a current provided on the non-light-receiving surface side A plurality of solar cell elements, and a plurality of solar cell elements, each including a plurality of solar cell elements, and a plurality of solar cell elements each including a back side collector electrode and a plurality of back side main electrodes connected to the back side collector electrode for extracting output to the outside. A front-side main electrode of the first solar cell element selected from the battery elements and a back-side main electrode of the second solar cell element selected from the plurality of solar cell elements and adjacent to the first solar cell element, respectively A plurality of main tabs for electrical connection; The remaining front side main electrode of the solar cell element and the back side electrode of the second solar cell element are electrically connected, and the sub tab is shorter and less in number than the main tab. Yes. That is, as a tab for connecting solar cell elements, a main tab and a sub tab having a shorter length than this main tab are used in combination, and the main tab connects the front main electrode and the back main electrode. The sub tab connects the front side main electrode and the back side electrode (the back side main electrode and / or the back side collecting electrode). In this way, the main tab is responsible for most of the role for electrically connecting the solar cell elements to each other, and the auxiliary tab is used in an auxiliary manner so that the number of sub tabs is smaller than that of the main tab. There is almost no adverse effect on the electrical connection between the battery elements. In addition, since the effect of such sub tabs is small even if the length is shortened, the labor of connection can be greatly reduced, and the amount of tab material used can be reduced, resulting in cost reduction. .

  The solar cell module according to claim 2 of the present invention is the solar cell module according to claim 1, wherein the back side collector electrode is provided on substantially the entire surface of the second solar cell element on the non-light-receiving surface side, The length of the junction where the main tab of the second solar cell element is connected to the back side main electrode is larger than the length of the junction where the sub tab is connected to the back side electrode of the second solar cell element. I am doing so. Since the back-side collector electrode is provided on substantially the entire surface on the non-light-receiving surface side, the back-side electrode (the back-side collector electrode and the back-side main electrode to which the back-side collector electrode is connected) has low resistance at any location. Therefore, if the junction length to which the plurality of main tabs and the back side main electrode of the solar cell element having such a low resistance are connected is increased, the solar cell elements are electrically connected to each other. It is possible to further reinforce the action of giving the main tab most of the role. And for the sub tabs that are less than the main tab, the effect of reducing the length of the joint connected to the back electrode of the solar cell element is small, so the labor of connection is saved and the amount of tab material used is reduced. The cost reduction effect can be further enhanced.

  A solar cell module according to a third aspect of the present invention is the solar cell module according to the first or second aspect, wherein the plurality of main tabs and the sub-tabs are provided at locations other than the light receiving surface of the first solar cell element. The tab is electrically connected. Therefore, since the connection resistance by the tab can be lowered without hindering the incidence of light on the solar cell element, high efficiency can be obtained.

The solar cell module according to claim 4 of the present invention is the solar cell module according to any one of claims 1 to 3, wherein in any solar cell element constituting the plurality of solar cell elements, The number of the front-side main electrodes is n _1, and the light receiving surface of the solar cell element is divided into 2n ₁ parts so that the whole is 1, and the front main electrode is provided at a position that satisfies the formula (1).
m ₁ / 2n ₁ (1) (m ₁ : 1 to 2n ₁ −1 all odd numbers)
Furthermore, the solar cell module according to claim 5 of the present invention is the solar cell module according to claim 4, wherein the number of the back main electrodes is n ₂ (where n ₁ > n ₂ ). The non-light-receiving surface of the element is divided into 2n ₂ parts, and when it is defined as 1 as a whole, it is provided at a position satisfying the expression (2) and in substantially the same direction as the front side main electrode.
m ₂ / 2n ₂ (2) (m ₂ : all odd numbers of 1 to 2n ₂ −1)
Since the front and back main electrodes are provided at positions satisfying these relationships, the sizes of the regions formed on both sides of each linear main electrode can be made substantially uniform. These regions are regions where collector electrodes connected to the respective main electrodes are provided. Therefore, it is possible to collect current in a balanced manner from the collector electrode provided in a region having approximately the same size to each main electrode.

  The solar cell module according to claim 6 of the present invention is the solar cell module according to any one of claims 1 to 4, wherein the back side electrode of the second solar cell element connected to the sub tab. Is the backside main electrode. Thus, since the subtab is connected to the backside main electrode to which the backside collector electrode is connected, it is possible to sufficiently collect and flow current to the subtab.

  A solar cell module according to claim 7 of the present invention is the solar cell module according to claim 6, wherein any solar cell element constituting the plurality of solar cell elements is substantially perpendicular to the light receiving surface. Therefore, when the solar cell element is considered to be transparent and viewed from the top, the front main electrode provided on the light receiving surface side and the back main electrode provided on the non-light receiving surface side are substantially the same. It is made visible in the same direction. This means that regardless of the solar cell element, the front side main electrode and the back side main electrode are provided at the same distance in the same direction at positions that are substantially plane-symmetric on the front and back sides of the solar cell element. It becomes extremely easy to connect the battery elements by tabs.

  The solar cell module according to claim 8 of the present invention is the solar cell module according to claim 6 or claim 7, wherein the front side main electrode and the back side main electrode are both three, and the outer two The plurality of main tabs are connected to each other, and the sub tab is connected to the central one. This configuration is the most basic configuration of the present invention, and the effects of the present invention can be sufficiently obtained with a simple configuration. In particular, since the main tab is two outside and the sub tab is one in the center, when the adjacent solar cell elements are electrically connected to each other by these tabs, there is little current bias and the connection is uniform. It will be excellent.

  The solar cell module according to claim 9 of the present invention is the solar cell module according to any one of claims 1 to 5, wherein the back side electrode of the second solar cell element connected to the sub tab. Is the backside collector electrode. Since the sub-tab and the back-side collector electrode are directly connected in this way, the back-side main electrode provided on the non-light-receiving surface side is equal to the number of main tabs, and the back-side main electrode is reduced by the number of sub-tabs. Can do.

  The solar cell module according to claim 10 of the present invention is the solar cell module according to claim 9, wherein the front side main electrode is three and the back side main electrode is two, and the outer side of the front side main electrode is outside. The plurality of main tabs were connected to two, and the sub tab was connected to one center of the front side main electrode. This configuration is the most basic configuration of the present invention, and the effects of the present invention can be sufficiently obtained with a simple configuration. In particular, since the main tab is two outside and the sub tab is one in the center, when the adjacent solar cell elements are electrically connected to each other by these tabs, there is little current bias and the connection is uniform. It will be excellent.

  In the solar cell module of the present invention, as a tab for connecting solar cell elements, a main tab and a sub tab having a shorter length and a smaller number than the main tab are used in combination. The back side main electrodes are connected to each other, and the sub tab connects the front side main electrode and the back side electrode (the back side main electrode and / or the back side collecting electrode). In this way, the main tab is responsible for most of the role for electrically connecting the solar cell elements to each other, and the auxiliary tab is used in an auxiliary manner so that the number of sub tabs is smaller than that of the main tab. There is almost no adverse effect on the electrical connection between the battery elements. In addition, since the effect of such sub tabs is small even if the length is shortened, the labor of connection can be greatly reduced, and the amount of tab material used can be reduced, resulting in cost reduction. .

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 6 is a diagram showing a solar cell element that can be used in the solar cell module of the present invention, where (a) is a cross-sectional structure thereof, FIG. 6 (b) is a view seen from the front surface, and FIG. It is the figure seen from.

In the figure, 1 is a semiconductor substrate of p-type silicon, for example, 2 is a reverse conductivity type diffusion region in which phosphorus atoms and the like are diffused at a high concentration on the surface side of the semiconductor substrate 1 and a pn junction is formed with the semiconductor substrate 1, Reference numeral 3 denotes an antireflection film made of a silicon nitride film or a silicon oxide film. Furthermore, a front side electrode 7 is provided on the front side of the semiconductor substrate 1, and a back side electric field region 4 which is a p ⁺ region containing a large amount of p-type semiconductor impurities such as aluminum on the back side, and a back side collecting electrode made of aluminum. 5. A back side main electrode 6 mainly composed of silver is provided.

  The semiconductor substrate 1 is a single crystal or polycrystalline silicon substrate, and includes a light receiving surface (front surface) which is one main surface and a non-light receiving surface (back surface) which is another main surface. This substrate may be either p-type or n-type. In the case of single crystal silicon, it is formed by a pulling method or the like, and in the case of polycrystalline silicon, it is formed by a casting method or the like. Polycrystalline silicon can be mass-produced and is extremely advantageous over single-crystal silicon in terms of manufacturing cost. An ingot formed by a pulling method or a casting method is cut into a size of about 15 cm × 15 cm and sliced to a thickness of about 300 μm to form a silicon substrate. In addition, the following description is given by an example using a p-type polycrystalline silicon substrate 1 doped with boron, which is easily available and has established a manufacturing method as a solar cell.

  On the surface side of the silicon substrate 1, a reverse conductivity type diffusion region 2 in which a semiconductor impurity having a conductivity type opposite to that of the silicon substrate 1, such as phosphorus, is diffused at a high concentration is formed. A pn junction is formed between them. Further, an antireflection film 3 and a front electrode 7 are provided on the surface side of the silicon substrate 1.

  On the back surface side of the silicon substrate 1, a back surface field region 4 is formed in which a semiconductor impurity having the same conductivity type as the impurity (boron) of the silicon substrate 1 exhibiting p-type, for example, aluminum, is diffused at a high concentration. 6 is provided.

  As shown in FIG. 6B, the front-side electrode 7 is generally formed in a lattice shape, and is formed by applying a silver paste or the like by screen printing or the like and then baking. Further, the front side electrode 7 is formed by etching away a portion corresponding to the electrode of the antireflection film 3 and forming the front side electrode 7 in this portion, or by baking the front side electrode 7 directly from above the antireflection film 3. May form.

As shown in FIG. 6 (c), the back side is coated with a metal paste containing aluminum powder by a screen printing method or the like and then baked at 700 to 800 ° C., so that the silicon of the silicon semiconductor substrate 1 is made of aluminum. Is diffused to form a back surface electric field region 4 which is a p ⁺ region containing a large amount of p-type semiconductor impurities. This forms an electric field for improving the collection efficiency of carriers generated inside the substrate by light irradiation, and has an effect of preventing the generated carriers from recombining on the back surface. And the carrier generated in the solar cell element can be efficiently collected by the electric field effect (BSF effect), the conversion efficiency of the solar cell element can be improved, and the sensitivity on the long wavelength side is also improved. The difference in sensitivity varies depending on the parameters of the solar cell element such as the thickness of the substrate and the doping concentration.

  The back surface electric field region 4 is preferably formed on substantially the entire back surface of the semiconductor substrate 1, and at the same time as this is formed, a back side collecting electrode 5 mainly composed of silicon and unreacted aluminum is left on the back surface. Often used. In this case, the back side main electrode 6 is formed by printing and baking a metal paste containing, for example, silver powder, which has better solder wettability than aluminum forming the back side collecting electrode 5, and is used for connection to a tab 9 described later.

  In addition, the aluminum sometimes causes warping of the substrate due to shrinkage during firing. In that case, it is possible to leave only the back surface electric field region 4 formed by removing aluminum. However, in this case, the back side collector electrode 5 and the back side main electrode 6 are also formed of silver paste.

  Note that the surface of the front-side electrode 7 and the back-side main electrode 6 mainly composed of silver thus produced may be coated with solder in order to prevent silver oxidation and improve connectivity. Many.

  Also, since the electrical output generated by a single solar cell element is usually small, it is necessary to configure a solar cell module by connecting multiple solar cell elements in series and parallel so that a practical electrical output can be taken out. is there. This is combined according to the intended use of the load of the solar cell, and is formed into a module by sealing the solar cell element with resin, glass or the like in order to protect it from breakage.

  An example of the solar cell module of the present invention will be described with reference to FIG. Although this figure is used in the description of a conventional general solar cell module, the present invention is characterized by the structure of the electrode portion and the tab of the solar cell element, so that the structure of the solar cell module is particularly changed. There is no.

  As shown in FIG. 7, a plurality of solar cell elements are arranged at a predetermined interval. And the front side electrode of one solar cell element and the back side electrode of the adjacent solar cell element are soldered by a tab 9 made of, for example, copper foil, and are electrically connected in series and parallel. The tab 9 is usually an electrode in which a copper foil having a thickness of about 0.1 mm to about 0.3 mm and a width of about 2 mm is coated with solder, cut into a predetermined length, and the solder is melted with hot air or the like. Connect with.

  The solar cell element group connected in this way is a filler 11 mainly composed of an ethylene vinyl acetate copolymer (EVA) or the like between the translucent panel made of glass or the like and the back surface protective material 12. The solar cell module is configured by being hermetically sealed. The output of the solar cell module is connected to the terminal box 14 via the output wiring 13. The terminal box 14 is further connected to an external load (not shown).

  The solar cell module and the solar cell element of the present invention have the above-described structure. Hereinafter, the structure of the electrode and the tab of the solar cell module according to the present invention will be described in more detail.

  FIG. 1 is a schematic diagram showing an example in which solar cell elements in a solar cell module according to the present invention are connected by a tab according to the present invention. FIG. 1 is a diagram in which adjacent solar cell elements X1 (first solar cell elements) and solar cell elements X2 (second solar cell elements) selected from the solar cell module of the present invention are arranged and viewed from the back side. 1 (a) is before the tab connection, and FIG. 1 (b) is after the tab connection. FIG. 1C is a cross-sectional structure diagram viewed from the Aa direction in FIG. For the sake of explanation, the left side solar cell element X1 is in a state in which the front side main electrode 7a can be seen through the solar cell element, and the front side collecting electrode 7b and the back side electrode are omitted, but both the solar cell elements X1 and X2 The electrode shapes on the front surface side and the back surface side are the same as those shown in FIGS. 6B and 6C.

  As shown in FIG. 1A, in this example, three front side main electrodes 7a are provided as the front side electrodes 7 on the light receiving surface side of the solar cell element X1 shown on the left side. On the non-light-receiving surface side of the solar cell element X2 shown on the right side, three back side main electrodes 6 are provided as back side electrodes, and a back side collecting electrode 5 for collecting current is provided on substantially the entire surface. Both the front side main electrode 7a and the back side main electrode 6 are linear, and the output of the solar cell element collected by each collector electrode can be taken out.

  FIG. 1B and FIG. 1C show a state after the tab connection. As shown in the figure, the tab 9 according to the present invention includes a main tab 9a and a sub tab 9b. The main tab 9a is adjacent to the front main electrode 7a of the solar cell element X1 and the solar cell element X1. The back side main electrode 6 of the solar cell element X2 is electrically connected to each other. Further, the sub tab 9b is provided so that the length is shorter and the number of the sub tab 9b is smaller than that of the main tab 9a, and the remaining front main electrode 7a of the solar cell element X1 to which the main tab 9a is not connected, and the solar cell element The remaining back main electrode 6 of X2 is electrically connected.

  In this way, the main tab 9a is responsible for most of the role for electrically connecting the solar cell elements, and the sub tab 9b is used in an auxiliary manner so that the number of the sub tabs 9b is smaller than that of the main tab 9a. Therefore, the electrical connection between the solar cell elements is hardly adversely affected. In addition, since the effect of the sub tab 9b is small even if the length is shortened, it is possible to save the labor of connection by the shortened amount, and to reduce the amount of the tab material used. It will also reduce.

  As described above, a tab in which copper foil is coated with solder is generally used, but since this copper foil can be easily increased in thickness and can reduce the resistance of the module, Reducing the number of tabs is advantageous for cost reduction.

  In the example shown in this figure, there are two main tabs 9a and one sub tab 9b, but this configuration is the most basic configuration of the present invention, and the effects of the present invention can be achieved with a simple configuration. You can get enough. In particular, the main tab 9a has two outer tabs and the sub tab 9b has a central one. Therefore, when adjacent solar cell elements are electrically connected to each other by these tabs, there is little current bias, Excellent uniformity.

  In the solar cell module according to the present invention described above, the sub tab 9b and the back main electrode 6 are connected. Thus, since the sub tab 9b is connected to the back side main electrode 6 to which the back side collector electrode 5 is connected, it is possible to sufficiently collect and flow current to the sub tab 9b. In addition, as shown in FIG. 2, the sub tab 9 b and the back side collector electrode 5 may be connected. 2A is a schematic diagram before the tab connection, and FIG. 2B is a schematic diagram after the tab connection. The back side collector electrode 5 is usually made of aluminum and has poor solder connectivity. Therefore, as shown in FIG. 2A, the back side collector electrode 5 is made of a metal paste containing silver or the like having good solderability. A tab-attached point 5a that is electrically connected to the electrode 5 is formed, and the sub-tab 9b may be connected through this point. If the sub-tab 9b and the back-side collector electrode 5 are directly connected in this way, the back-side main electrode 6 provided on the non-light-receiving surface side becomes equal to the number of main tabs 9a, and the back-side main electrode 6 is connected to the number of sub-tabs 9b. Can be reduced. Therefore, it is possible to reduce not only the amount of copper foil used for the tab but also the amount of silver paste used to form the back main electrode 6.

  Further, as described above, when the back side collector electrode 5 is provided on substantially the entire surface on the non-light-receiving surface side of the solar cell element X2, the back side electrode (the back side collector electrode 5 and the back side main electrode 6 to which the back side collector electrode 5 is connected) is located at any location. Is also low resistance. As is clear from FIG. 1B, in the solar cell element X2, the length of the junction where the main tab 9a and the back side main electrode 6 that are larger in number than the sub tab 9b are connected is the length of the sub tab 9b and the back side. It is made larger than the junction part length to which an electrode (the back side collector electrode 5 and the back side main electrode 6 to which this is connected) is connected. Therefore, by these interactions, the action of causing the main tab 9a to play most of the role for electrically connecting the solar cell elements can be further strengthened. For the sub tabs 9b having a smaller number than the main tabs 9a, even if the length of the joint connected to the back electrode of the solar cell element is shortened, the influence is small, so that the labor of connection is saved and the tab material is used. The amount can be reduced to further increase the cost reduction effect.

  Further, in the solar cell module according to the present invention, as shown in FIG. 3, the plurality of main tabs 9 a and sub tabs 9 b are electrically connected by, for example, bypass tabs 9 c at locations other than the light receiving surface of the solar cell element X <b> 1. It is desirable to connect. FIG. 3A is an example in which a bypass tab 9c is provided for the solar cell element X2 shown in FIG. 1B, and FIG. 3B is an example of the solar cell element X2 shown in FIG. In contrast, this is an example in which a bypass tab 9c is provided. By doing in this way, the connection resistance by a tab can be lowered without hindering the incidence of light on the solar cell element, and the number of tabs can be reduced and high efficiency can be obtained without lowering the FF. Can do.

  Further, regarding the position where the main electrode is provided, the front side provided on the light receiving surface side when the solar cell element is regarded as transparent from the direction substantially orthogonal to the light receiving surface and viewed from above. It is desirable that the main electrode 7a and the back side main electrode 6 provided on the non-light-receiving surface side be provided at a position where they can be visually recognized in the same direction. This is, for example, the relationship shown in the solar cell elements X1 and X2 in FIG. That is, no matter which solar cell element is used, the front side main electrode 7a and the back side main electrode 6 are provided at the same distance in the same direction at positions that are substantially plane symmetrical on the front and back sides of the solar cell element. A linear tab can be used, and it becomes very easy to connect solar cell elements to each other by the tab.

  Furthermore, in this case, the position of the back side main electrode 6 is a position hidden behind the front side main electrode 7a. This portion where the back side main electrode 6 is provided is a region where the generation of photogenerated carriers is reduced when the front side main electrode 7a is exposed to light. There is also an effect that it is possible to suppress an adverse effect caused by the absence of.

The front main electrode may be provided at a position that satisfies the following relationship. In other words, the number of the front side main electrodes 7a is n ₁ and the light receiving surface of the solar cell element is divided into 2n ₁ parts so that the total number is _1. Thus, the front side main electrode 7a is provided at a position satisfying the expression (1).
m ₁ / 2n ₁ (1) (m ₁ : 1 to 2n ₁ −1 all odd numbers)
FIG. 4 is a schematic diagram for explaining the relationship of the equation (1), and FIG. 4A shows a case where there are three front side main electrodes. In this case, since the number of front side main electrodes is n ₁ = 3, when the light receiving surface of this solar cell element is divided into 2n ₁ = 6 parts to make 1 as a whole, this equally divided m ₁ / It is provided at a position satisfying 2n _1, that is, at positions 1/6, 3/6, and 5/6 (enclosed by a frame line) in the drawing (m ₁ : 1 to 2n ₁ −1 = 5 or less). Are all odd numbers of 1, 3, 5, and 5). If the front-side main electrode is provided at a position satisfying such a relationship, the size of the regions formed on both sides of each linear main electrode becomes substantially equal. This is as shown by the double arrows in the figure. These regions are regions where collector electrodes connected to the respective main electrodes are provided. Therefore, it is possible to collect current in a balanced manner from the collector electrode provided in a region having approximately the same size to each main electrode.

  When the same number of the back side main electrodes as the front side main electrodes is used, the solar cell element is regarded as transparent from the direction substantially perpendicular to the light receiving surface as described above, and viewed from above. In this case, it is desirable that the front side main electrode 7a provided on the light receiving surface side and the back side main electrode 6 provided on the non-light receiving surface side be provided at a position where they are visually recognized in the same direction. . As a result, it is possible to use a linear tab as described above, and it is possible to obtain an effect that it is very easy to connect the solar cell elements to each other with the tab, and at the same time, the position satisfies the formula (1). This is because the effect of collecting current in a balanced manner for each main electrode can also be obtained.

Further, as shown in FIG. 2, when the sub-tab 9b and the back side collector electrode 5 are connected, the number of the back side main electrodes can be reduced. The front main electrode 7a provided on the light-receiving surface side and the back-side main electrode provided on the non-light-receiving surface side when viewed from above when the solar cell element is regarded as transparent from a direction substantially orthogonal to 6 is provided at a position where they can be visually recognized by being overlapped with each other in substantially the same direction, it is possible to obtain an effect of easily connecting the solar cell elements with the tabs. However, in this case, it may be provided at a position satisfying the following relationship. That is, the back side main electrode 6, and the number and n _2, the non-light-receiving surface of the solar cell element 2n ₂ equal portions, at a position satisfying the total and 1 and the case in (2), and the front-side main electrode 7a is provided in substantially the same direction.
m ₂ / 2n ₂ (2) (m ₂ : all odd numbers of 1 to 2n ₂ −1)
FIG. 4B illustrates the case where there are two backside main electrodes. In this case, since the number of backside main electrodes is n ₂ = 2, the non-light-receiving surface of this solar cell element is equally divided into 2n ₂ = 4, and the whole is 1 and m ₂ / 2n ₂ is satisfied. Positions, i.e., 1/4 and 3/4 positions (enclosed by frame lines) in the figure (m ₂ : 1 to 2n ₂ −1 = 3 and all odd numbers are 1 and 3) 2). If the back side main electrode is provided at a position satisfying such a relationship, the sizes of the regions formed on both sides of each of the linear main electrodes become substantially uniform. This is as shown by the double arrows in the figure. These regions are regions where collector electrodes connected to the respective main electrodes are provided. Therefore, it is possible to collect current in a balanced manner from the collector electrode provided in a region having approximately the same size to each main electrode.

  FIG. 5 shows an example in which the solar cell elements are connected to each other by the tab according to the present invention when the front main electrode is in the state shown in FIG. 4A and the back main electrode is in the state shown in FIG. 4B. FIG. 5A is before the tab connection, and FIG. 5B is after the tab connection. As shown in FIG. 5, in the case where the main electrode is shown in FIG. 4, it is necessary to use a deformed main tab 9 d as a tab connecting the front side main electrode 7 a and the back side main electrode 6. Although it is not easy to tab-connect battery elements, good electrical characteristics can be obtained in both the front main electrode 7a and the back main electrode 6 as described above.

  Although the solar cell module of the present invention can be realized as described above, the embodiments of the present invention are not limited to the above-described examples, and various modifications can be made without departing from the scope of the present invention. Can be added.

  Usually, an electrode by screen printing is a solar cell element of 10 cm × 10 cm and has two main electrodes. If it is larger than this, it will be a tradeoff with other series resistance components, but if necessary, it may be better to use three. This is effective only when the bottleneck portion is on the collector electrode due to the balance with other series resistance components, and is not necessary when the other portion becomes a bottleneck. Therefore, the present invention is not limited by the area of the solar cell element.

  For example, in the above description, the example in which the number of front main electrodes is three has been described. However, the number is not limited to this, and may be four or more. The number of front-side main electrodes on the light-receiving surface side is determined by the balance with other series resistance components. If the number of the main resistance is increased when the bottleneck part of the series resistance is on the front-side collector electrode, the resistance is reduced. Is effective. This can be determined by performing a simulation or actually making a prototype.

It is a schematic diagram which shows an example by which solar cell elements are connected by the tab which concerns on this invention, (a) shows before tab connection, (b) shows after tab connection. Moreover, (c) is a cross-sectional structure diagram seen from the Aa direction of (b). It is a schematic diagram which shows another example by which solar cell elements are connected by the tab which concerns on this invention, (a) shows before tab connection, (b) shows after tab connection. (A), (b) is a schematic diagram which shows another example in which solar cell elements are connected by the tab which concerns on this invention. It is a schematic diagram for demonstrating the position which provides a main electrode, (a) is a case where the front side main electrode is three, (b) is a case where the back side main electrode is two. When a main electrode is in the state shown in FIG. 4, it is a schematic diagram which shows the example by which solar cell elements are connected by the tab which concerns on this invention, (a) is before tab connection, (b) is after tab connection. Indicates. It is a figure which shows the solar cell element used for the solar cell module of this invention, (a) is sectional drawing, (b) is the figure seen from the surface, (c) is the figure seen from the back surface. It is a cross-section figure of a general solar cell module. It is a figure which shows a general solar cell element, (a) is a cross-section figure, (b) is the figure seen from the surface, (c) is the figure seen from the back surface. It is a schematic diagram which shows the example in which solar cell elements are connected by the tab in a general solar cell module, (a) shows before tab connection, (b) shows after tab connection.

Explanation of symbols

1. Semiconductor substrate (silicon substrate)
2 ... Reverse conductivity type diffusion region 3 ... Antireflection film 4 ... Back surface electric field region 5 ... Back side collector electrode 5a ... Point with tab 6 ... Back side main electrode 7 ... Front side electrode 7a ... Front side main electrode 7b ... Front side collector electrode 9 ... Tab 9a ... Main tab 9b ... Sub tab 9c ... Bypass tab 9d ... Deformed main tab 10 ... -Translucent panel 11-Filler 12-Back surface protective material 13-Output wiring 14-Terminal box 101-Semiconductor substrate 102-Reverse conductivity type diffusion region 103-Reflection Prevention film 104 ... Back surface electric field region 105 ... Back side collector electrode 106 ... Back side main electrode 107 ... Front side electrode 107a ... Front side main electrode 107b ... Front side collector electrode X ... Solar cell element X1 ... solar cell element (first solar cell element)
X2 ... solar cell element (second solar cell element)

Claims (10)

A plurality of solar cell elements having a light receiving surface and a non-light receiving surface and arranged at a predetermined interval,
A front side electrode provided on the light receiving surface side, including a front side collector electrode for collecting current and three or more linear front side main electrodes to which the front side collector electrode is connected and to extract output to the outside, A plurality of backside electrodes provided on the non-light-receiving surface side, each including a backside collector electrode for collecting current and a plurality of backside main electrodes connected to the backside collector electrode for extracting output to the outside A solar cell element;
A front-side main electrode of a first solar cell element selected from the plurality of solar cell elements, and a back side of a second solar cell element selected from the plurality of solar cell elements and adjacent to the first solar cell element A plurality of main tabs electrically connecting the main electrodes,
A sub tab having a shorter length and a smaller number than the main tab, electrically connecting the remaining front side main electrode of the first solar cell element and the back side electrode of the second solar cell element,
A solar cell module comprising: The back side collector electrode is provided on a substantially entire surface of the second solar cell element on the non-light-receiving surface side,
The junction length at which the plurality of main tabs and the back side main electrode of the second solar cell element are connected is longer than the junction length at which the sub tab and the back side electrode of the second solar cell element are connected. The solar cell module according to claim 1, wherein the solar cell module is made large. The solar cell module according to claim 1 or 2, wherein the plurality of main tabs and the sub tabs are electrically connected at a place other than the light receiving surface of the first solar cell element. In any solar cell element constituting the plurality of solar cell elements,
The number of the front side main electrodes is n _1, and the light receiving surface of the solar cell element is divided into 2n ₁ parts so that the total number is _1, and the front side main electrode is provided at a position satisfying the expression (1). Item 4. The solar cell module according to any one of Items 3.
m ₁ / 2n ₁ (1) (m ₁ : 1 to 2n ₁ −1 all odd numbers) The number of the backside main electrodes is n ₂ (where n ₁ > n ₂ ), and the non-light-receiving surface of this solar cell element is equally divided into 2n _{2 so} as to satisfy the formula (2) when the whole is 1. And the solar cell module of Claim 4 provided so that it might become the substantially the same direction as the said front side main electrode.
m ₂ / 2n ₂ (2) (m ₂ : all odd numbers of 1 to 2n ₂ −1) The solar cell module according to any one of claims 1 to 4, wherein the back electrode of the second solar cell element connected to the sub tab is a back main electrode. In any solar cell element that constitutes the plurality of solar cell elements, when viewed from the top, assuming that the solar cell element is transparent from a direction substantially orthogonal to the light receiving surface, the light receiving surface side The solar cell module according to claim 6, wherein the provided front-side main electrode and the back-side main electrode provided on the non-light-receiving surface side are visually recognized by overlapping each other in substantially the same direction. The front side main electrode and the back side main electrode are both three, and the plurality of main tabs are connected to the outer two, and the sub tab is connected to the central one. 8. The solar cell module according to 7. The solar cell module according to any one of claims 1 to 5, wherein the back side electrode of the second solar cell element connected to the sub tab is a back side collecting electrode. The front side main electrode is three and the back side main electrode is two, the plurality of main tabs are connected to two outside the front side main electrode, and the secondary main electrode is connected to one center of the front side main electrode. The solar cell module according to claim 9, to which a tab is connected.

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