JP2009071340A - Solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell module effectively suppressing lowering of output even when an area of the backside of a solar battery cell constituting the solar cell module becomes large. <P>SOLUTION: The solar cell module including a plurality of electrically connected solar battery cells 20, 21, and 22 is configured such that a p+ layer and an n+ layer are formed on the backsides of the solar battery cells 20, 21, and 22; and at least one of bus bar electrodes composed of a bus bar p electrode 13 intersecting with a finger p electrode 11 formed on the p+ layer and a bus bar n electrode 14 intersecting with a finger n electrode 12 formed on the n+ layer is formed inside the backside of the solar battery cells 20, 21, and 22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solar cell module, and more particularly to a solar cell module that can effectively suppress a decrease in output even when the area of the back surface of a solar cell constituting the solar cell module increases.

In recent years, development of clean energy has been desired due to the problem of depletion of energy resources and global environmental problems such as the increase of CO _{2 in} the atmosphere. In particular, a solar battery module configured by connecting a plurality of solar cells. The solar power generation used has been developed and put into practical use as a new energy source and is on the path of development.

  Conventionally, a solar cell constituting a solar cell module has a conductivity type opposite to the conductivity type of the silicon substrate on the surface (light receiving surface) on the side where sunlight enters among the surfaces of a single crystal or polycrystalline silicon substrate, for example. A pn junction is formed by diffusing impurities to be formed, and electrodes are formed on the light receiving surface of the silicon substrate and the back surface on the opposite side. It is also common to increase the output by the back surface field effect by diffusing impurities of the same conductivity type as the silicon substrate at a high concentration on the back surface of the silicon substrate. However, in the solar cell having such a structure, the electrode formed on the light receiving surface blocks sunlight incident thereon, so that the output of the solar cell is reduced, and consequently the output of the solar cell module is reduced. There was a problem that.

  Therefore, so-called back junction solar cells have been developed in which electrodes are not formed on the light receiving surface of a silicon substrate, but electrodes of different conductivity types are formed only on the back surface of the silicon substrate.

  In a back junction solar cell, since power can be taken out only from the back side of the silicon substrate on which the electrode is formed, the structure of the electrode is a back junction solar cell and a solar cell in which a plurality of these are connected. Very important in terms of module output.

  FIG. 20 shows a schematic cross-sectional view of an example of a conventional back junction solar cell. In this conventional back junction solar cell, for example, an antireflection film 109 is formed on the light receiving surface of a p-type silicon substrate 101, and an n + layer 105 and a p + layer 106 are formed on the back surface of the silicon substrate 101. Are formed at predetermined intervals alternately. A finger p electrode 111 is formed on the p + layer 106, and a finger n electrode 112 is formed on the n + layer 105.

  When sunlight is incident on the light receiving surface of the back junction solar cell, carriers generated in the vicinity of the light receiving surface of the semiconductor substrate 101 reach the pn junction formed on the back surface, and reach the finger p electrode 111 and the finger n electrode 112. It is collected as an electric current, taken out outside, and becomes an output of the solar cell module.

  FIG. 21 shows a schematic plan view of an example of the back surface of a conventional back junction solar cell. In this conventional electrode structure, from the viewpoint of improving the output of the solar battery cell, the finger p electrode 111 and the finger n electrode 112 are formed inside the back surface of the silicon substrate 101 so as to cover the entire back surface. A bus bar p-electrode 113 that intersects the finger p-electrode 111 and a bus-bar n-electrode 114 that intersects the finger n-electrode 112 are formed at the end of the back surface of 101.

Here, since the finger p electrode 111 and the finger n electrode 112 lose output when the series resistance increases, the cross-sectional area (electrode width × height) generally increases from the viewpoint of reducing the series resistance. Designed to. However, when the area of the back surface of the solar battery cell becomes large, the length L ₀ of the finger p electrode 111 and the finger n electrode 112 needs to be longer, but the height of these electrodes is limited, In order to increase the cross-sectional area, it was necessary to increase the electrode width W ₀ . When the electrode width W ₀ is increased, the pitch P ₀ between the finger p-electrode 111 and the finger n-electrode 112 is increased, and the carrier moving distance in the silicon substrate 101 is increased, so that the output of the solar cell is increased. As a result, there is a problem that the output of the entire solar cell module is lowered.

JP 2001-68699 A JP 2002-359388 A

  The objective of this invention is providing the solar cell module which can suppress the fall of an output effectively, even when the area of the back surface of the photovoltaic cell which comprises a solar cell module becomes large.

  The present invention is a solar cell module including a plurality of electrically connected solar cells, wherein a p + layer and an n + layer are formed on at least one back surface of the solar cells, and p At least one of the bus bar electrodes consisting of the bus bar p electrode intersecting the finger p electrode formed on the + layer and the bus bar n electrode intersecting the finger n electrode formed on the n + layer is inside the back surface. It is the solar cell module currently formed.

  In addition, the present invention is a solar cell module including a plurality of electrically connected solar cells, wherein p + layers and n + layers are formed on all back surfaces of the solar cells, and p At least one of the bus bar electrodes including the bus bar p electrode intersecting the finger p electrode formed on the + layer and the bus bar n electrode intersecting the finger n electrode formed on the n + layer is a solar cell. It is a solar cell module currently formed in the inside of each back.

  Here, in the solar cell module of the present invention, the substrate including the insulator formed with a plurality of holes and the conductor formed on the holes of the insulator is installed on the bus bar electrode of the solar cell. The bus bar electrode and the conductor are electrically connected through the hole, and the bus bar p electrode of one solar cell and the bus bar n electrode of the other solar cell are electrically connected by the conductor. It is a solar cell module.

  Moreover, in the solar cell module of this invention, it is preferable that the insulating board | substrate is installed on the conductor.

  Moreover, in the solar cell module of this invention, it is preferable that the photovoltaic cell is sealed with transparent resin between a pair of board | substrates which oppose.

  ADVANTAGE OF THE INVENTION According to this invention, even when the area of the back surface of the photovoltaic cell which comprises a photovoltaic module becomes large, the solar cell module which can suppress effectively the fall of an output can be provided.

It is typical sectional drawing after the slice from the ingot of the silicon substrate used for this invention. It is typical sectional drawing after the etching of the damage layer of the silicon substrate used for this invention. It is typical sectional drawing after formation of the diffusion prevention film of the silicon substrate used for this invention. It is typical sectional drawing after formation of the p <+> layer and n <+> layer of the silicon substrate used for this invention. It is typical sectional drawing after formation of the texture structure of the silicon substrate used for this invention. It is typical sectional drawing after the removal of the diffusion protective film and paste material of a silicon substrate used for this invention. It is typical sectional drawing after formation of the passivation film of the silicon substrate used for this invention. It is typical sectional drawing after the removal of the passivation film of the silicon substrate used for this invention. It is typical sectional drawing after electrode formation of the silicon substrate used for this invention. It is a typical top view of a desirable example of the back of a photovoltaic cell of the present invention. It is a schematic plan view of another preferred example of the back surface of the solar battery cell of the present invention. It is a typical top view of the substrate used for the solar cell module of the present invention. It is typical sectional drawing along line X13-X13 in the substrate shown by FIG. It is typical sectional drawing of another preferable example of the substrate used for the solar cell module of this invention. It is a typical top view of a preferable example of the solar cell module of the present invention. It is typical sectional drawing along line X16-X16 in the solar cell module shown by FIG. It is typical sectional drawing of another preferable example of the solar cell module of this invention. It is a typical expanded sectional view of another preferable example of the solar cell module of this invention. (A) is the typical top view which looked at an example of the solar cell module of this invention from the light-receiving surface side, (B) is the schematic which looked at another example of the solar cell module of this invention from the light-receiving surface side. FIG. It is typical sectional drawing of an example of the conventional back junction type photovoltaic cell. It is a typical top view of an example of the back surface of the conventional back junction type photovoltaic cell.

  Embodiments of the present invention will be described below. In the drawings of the present application, the same reference numerals represent the same or corresponding parts. Moreover, in this specification, let the surface of the side which sunlight injects into a solar cell module be a light-receiving surface, and let the surface on the opposite side of a light-receiving surface and the side which sunlight does not enter be a back surface.

  The schematic cross-sectional views of FIGS. 1 to 9 show a preferred example of the manufacturing process of the solar cell used in the solar cell module of the present invention. First, as shown in FIG. 1, a silicon substrate 1 as a semiconductor substrate obtained by slicing an ingot of a silicon crystal has a damaged layer 1a in the vicinity of the surface at the time of slicing. Therefore, as shown in FIG. 2, the damaged layer 1a is preferably etched using an acidic or alkaline solution. Here, the silicon substrate 1 may be n-type or p-type, and the size and thickness of the silicon substrate 1 are not limited. However, when a pyramidal microstructure called a texture is formed on the light receiving surface of the silicon substrate 1 in order to suppress the loss of reflection of incident sunlight, the surface orientation of the light receiving surface of the silicon substrate 1 is (100). Preferably there is.

  Next, as shown in FIG. 3, a p-type paste material 2 containing, for example, boron as a p-type impurity on the back surface opposite to the light-receiving surface of the silicon substrate 1, and an n-type paste material containing, for example, phosphorus as an n-type impurity. 3 are attached to a desired pattern shape. And in order to evaporate the organic solvent component contained in these paste materials, after heating the silicon substrate 1 to the temperature of 100 to 200 degreeC, for example, the whole back surface to which the paste material adhered is covered with the diffusion prevention film 4. Here, as means for attaching the paste material to a desired pattern shape, for example, screen printing or ink jet printing can be used. Further, as a pattern shape, in order to efficiently collect minority carriers generated in the silicon substrate 1, a p-type paste material 2 and an n-type paste material 3 are arranged along the back surface of the silicon substrate 1 as shown in FIG. It is preferable that they are formed alternately at intervals. Further, the diffusion preventing film 4 is made of, for example, a silicon oxide film, and can be formed by forming a film by an atmospheric pressure CVD method or drying a coating solution containing silicon oxide.

  Subsequently, the silicon substrate 1 is put into a quartz furnace heated to, for example, 900 ° C. to 1000 ° C., and placed in the quartz furnace, for example, for 30 minutes to 60 minutes, whereby boron contained in the p-type paste material 2 is contained. Then, phosphorus contained in the n-type paste material 3 diffuses into the silicon substrate 1, and a plurality of p + layers 6 and n + layers 5 are alternately spaced along the back surface of the silicon substrate 1 as shown in FIG. Open and formed. Here, since the diffusion prevention film 4 is formed on the back surface of the silicon substrate 1, boron contained in the p-type paste material 2 and phosphorus contained in the n-type paste material 3 are diffused into the silicon substrate 1. Diffusion outside the silicon substrate 1 is prevented.

  Next, the silicon substrate 1 is immersed in a high-temperature aqueous solution containing, for example, an alkali such as sodium hydroxide or potassium hydroxide and isopropyl alcohol (IPA), and anisotropic etching along the silicon crystal orientation proceeds. As shown in FIG. 5, a fine pyramid-like texture structure 8 having a (111) plane is formed on the light receiving surface of the silicon substrate 1. Here, since the diffusion prevention film 4 is formed on the back surface of the silicon substrate 1, the back surface of the silicon substrate 1 is not etched.

  Next, as shown in FIG. 6, the silicon substrate 1 is immersed in hydrofluoric acid or the like to remove the diffusion protective film 4, the p-type paste material 2, and the n-type paste material 3 on the back surface of the silicon substrate 1. . Then, as shown in FIG. 7, passivation films 9 and 10 for suppressing the surface recombination of carriers are formed on the light receiving surface and the back surface of the silicon substrate 1. As the passivation films 9 and 10, for example, a silicon oxide film formed by thermal oxidation or a silicon nitride film formed by a plasma CVD method is used. By forming the passivation films 9 and 10, it is possible to effectively suppress surface recombination of carriers. it can. Here, when a silicon nitride film is used as the passivation film 9 formed on the light receiving surface of the silicon substrate 1, the refractive index thereof is about 2.1. Therefore, the silicon nitride film is the sun on the light receiving surface of the silicon substrate 1. It can also be used as an antireflection film that suppresses reflection of light.

  Next, in order to make electrical connection with the p + layer 6 and the n + layer 5 on the back surface of the silicon substrate 1, a passivation film 10 formed on the back surface of the silicon substrate 1 is desired as shown in FIG. Removed into pattern shape. Passivation film 10 is preferably removed in the form of a dot or a line, for example, and the removal shape is preferably determined according to the arrangement of p + layer 6 and n + layer 5. Further, the passivation film 10 inside the end portions of the p + layer 6 and the n + layer 5 is removed so that electrodes are not formed in portions other than the p + layer 6 and the n + layer 5. It is preferable.

  Finally, as shown in FIG. 9, the finger p electrode 11 is formed on the p + layer 6 and the finger n electrode 12 is formed on the n + layer 5 in accordance with the portion from which the passivation film 10 has been removed. The Here, as the electrode material of the finger p electrode 11 and the finger n electrode 12, a highly conductive material such as silver or aluminum may be used so that a current generated in the solar battery cell can be taken out sufficiently. preferable. Further, as means for forming the finger p electrode 11 and the finger n electrode 12, for example, means such as vapor deposition of an electrode material by electron beam heating in high vacuum, screen printing of a paste containing the electrode material, or plating of the electrode material is used. Can do. Furthermore, in order to obtain good ohmic contact between the silicon substrate 1 and the finger p-electrode 11 and the finger n-electrode 12, it is preferable that a heat treatment at 400 ° C. to 500 ° C. is performed after the electrode material is attached to the silicon substrate 1. A bus bar electrode intersecting with the finger electrodes is formed together with these finger electrodes. In addition, the finger p electrode 11 and the finger n electrode 12 are electrodes which mainly collect the current generated in the solar battery cell. Moreover, a bus-bar electrode means the electrode which collects the electric current which the finger electrode collected, and is mainly used for a connection with another photovoltaic cell.

A schematic plan view of FIG. 10 shows a preferable example of the back surface of the solar battery cell of the present invention obtained as described above. As shown in FIG. 10, a plurality of finger p-electrodes 11 and finger n-electrodes 12 are linearly formed on the back surface of the solar battery cell so as to alternately cover the entire back surface of the solar battery cell. The bus bar p electrode 13 that intersects the p electrode 11 is formed at the end of the back surface, while the bus bar n electrode 14 that intersects the finger n electrode 12 is formed inside the back surface. By doing in this way, even if it is a case where the area of the back surface of a photovoltaic cell is the same by this invention and the conventional, the length L of the finger n electrode 12 and the finger p electrode 11 of the back surface of the photovoltaic cell of this invention ₁ becomes shorter than the length L _{0 of the} conventional finger n electrode 112 and finger p electrode 111 shown in FIG. Therefore, even when the area of the back surface of the solar battery cell is increased, the series resistance can be reduced, and not only the width W _{1 of} the finger n electrode 12 and the finger p electrode 11 but also the finger p electrode 11 and the finger n electrode 12. The pitch P ₁ between these can also be reduced. Therefore, in the present invention, even when the area of the back surface of the solar battery cell becomes large, the moving distance of the carrier in the silicon substrate 1 does not become long, and it becomes possible to improve the carrier collection efficiency in the finger electrode. Thus, a decrease in the output of the solar battery cell can be effectively suppressed.

The schematic plan view of FIG. 11 shows another preferred example of the back surface of the solar battery cell of the present invention. As shown in FIG. 11, two bus bar n electrodes 14 intersecting the finger n electrode 12 and one bus bar p electrode 13 intersecting the finger p electrode 11 are formed inside the back surface of the solar battery cell. Yes. Therefore, even when the area of the back surface of the solar battery cell is increased, the length L ₁ of the finger n electrode 12 and the finger p electrode 11 can be shortened. Can be deterred.

10 and FIG. 11, the length L ₁ of the finger n electrode 12 and the finger p electrode 11 is not more than ½ of the length L in the longitudinal direction of the finger electrode on the back surface of the solar battery cell. Preferably, it is preferably 1/4 or less, and more preferably 1/6 or less. When L ₁ is larger than 1/2 of L, when the area of the back surface of the solar battery cell becomes large, the series resistance tends to be too large and the decrease in the output of the solar battery cell cannot be effectively suppressed. When L ₁ is 1/4 or less of L, particularly 1/6 or less, even when the area of the back surface of the solar battery cell is increased, the series resistance is not so large and the output of the solar battery cell is particularly effectively reduced. It tends to be deterred.

In this specification, the length L ₁ of the finger electrode refers to the length from the contact between the finger electrode and the bus bar electrode to the tip of the finger electrode, as shown in FIGS. Further, when there are a plurality of finger electrodes, at least one of the finger electrodes may be in the above range, but it is preferable that all finger electrodes have a length in the above range.

  In FIG. 12, the typical top view of a preferable example of the substrate used for the solar cell module of this invention is shown. In this substrate 18, a conductor 15 is formed in a predetermined shape on the surface of an insulator 16 in which a plurality of holes 17 are formed by etching or the like. FIG. 13 shows a schematic cross section taken along line X13-X13 in the substrate 18 shown in FIG. As shown in FIG. 13, in the substrate 18, the conductor 15 is formed on the plurality of holes 17 formed in the insulator 16 so as to block the holes 17. Further, as shown in the schematic cross-sectional view of FIG. 14, an insulating substrate 19 such as glass or resin may be formed on the conductor 15.

  In FIG. 15, the typical top view of a preferable example of the solar cell module of this invention is shown. In this solar cell module, the substrate 18 shown in FIG. 13 is installed on the bus bar p electrode 13 and the bus bar n electrode 14 of the solar cells 20, 21, 22. The substrate 18 and the solar battery cells 20, 21, and 22 are electrically connected to each other, and the solar battery cells 20, 21, and 22 are electrically connected by the substrate 18. Here, the bus bar p-electrode 13 of the solar battery cell 21 is electrically connected to the conductor 15 of the substrate 18 at six locations. The bus bar n-electrode 14 of the solar battery cell 21 is electrically connected to the conductor 15 of the substrate 18 at four locations.

  FIG. 16 shows a schematic cross section taken along line X16-X16 in the solar cell module shown in FIG. As shown in the schematic cross-sectional view of FIG. 16, the conductor 15 of the substrate 18 is electrically connected by the bus bar p electrode 13 and the bus bar n electrode 14 of the solar cells 20, 21, 22 and the solder 23 through the holes 17. It is connected. As shown in FIG. 15, the bus bar p-electrode 13 of the solar battery cell 20 and the bus bar n-electrode 14 of the solar battery cell 21 are electrically connected by the conductor 15, and the bus bar p-electrode of the solar battery cell 21. 13 and the bus bar n-electrode 14 of the solar battery cell 22 are electrically connected by a conductor 15. By doing in this way, a plurality of photovoltaic cells can be electrically connected in series via the substrate. Moreover, a bypass diode, a blocking diode, etc. can also be electrically connected with a photovoltaic cell. Moreover, as shown in the schematic cross-sectional view of FIG. 17, an insulating substrate 19 such as glass or resin may be formed on the conductor 15.

  Here, the solder 23 shown in FIGS. 16 and 17 can be formed on the bus bar p electrode 13 and the bus bar n electrode 14 in advance in the manufacturing process of the solar battery cell. In addition, a space between the substrate 18 and the solar battery cell 21 where the bus bar p-electrode 13 and the bus bar n-electrode 14 are not formed is filled with an insulating resin 24 such as silicon resin. Moreover, the size of the back surface of the photovoltaic cells 20, 21, 22 is, for example, about 155 mm wide × 155 mm long. Further, an insulating film such as a polyimide film having a thickness of about 25 to 500 μm is used as the insulator 16 of the substrate 18, and a metal such as copper or nickel having a thickness of about 50 to 500 μm is used as the conductor 15. Used.

  Moreover, as shown in the schematic enlarged sectional view of FIG. 18, the transparent substrate which permeate | transmits sunlight, such as tempered glass which improved the intensity | strength of plate glass or plate glass, for example to the light-receiving surface side of the photovoltaic cells 20, 21, and 22 25, and a substrate 26 such as plate glass or tempered glass is installed on the back side of the solar cells 20, 21, 22 and EVA (ethylene vinyl acetate) is interposed between the pair of opposed substrates 25 and 26. The solar cell module of the present invention can also be manufactured by crosslinking the transparent resin 27 after filling with the transparent resin 27.

  Moreover, in the solar cell module of this invention, as shown to the schematic top view of FIG. 19 (A), the several solar cell may be connected by one substrate 18, FIG.19 (B). As shown in the schematic plan view, a plurality of substrates 18 connecting a plurality of solar cells may be provided.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the present invention, it is possible to provide a solar cell module capable of effectively suppressing a decrease in output even when the area of the back surface of the solar battery cell constituting the solar cell module is increased. It can be suitably used for a solar cell module in which a plurality of junction type solar cells are electrically connected.

  1,101 Silicon substrate, 2 p-type paste material, 3 n-type paste material, 4 diffusion prevention film, 5,105 n + layer, 6,106 p + layer, 8 texture structure, 9,10 passivation film, 11,111 Finger p electrode, 12, 112 Finger n electrode, 13, 113 Bus bar p electrode, 14, 114 Bus bar n electrode, 15 Conductor, 16 Insulator, 17 holes, 18 Substrate, 19 Insulating substrate, 20, 21, 22 Solar cell, 23 solder, 24 insulating resin, 25, 26 substrate, 27 transparent resin.

Claims (5)

  A solar cell module including a plurality of electrically connected solar cells, wherein a p + layer and an n + layer are formed on at least one back surface of the solar cells, and the p + layer At least one of the bus bar electrodes composed of the bus bar p electrode intersecting with the finger p electrode formed on the upper surface and the bus bar n electrode intersecting with the finger n electrode formed on the n + layer is formed inside the back surface. It is formed in the solar cell module characterized by the above-mentioned.   A solar cell module including a plurality of electrically connected solar cells, wherein a p + layer and an n + layer are formed on all back surfaces of the solar cells, and the p + layer is formed on the p + layer. At least one of the bus bar electrodes including the bus bar p electrode intersecting the formed finger p electrode and the bus bar n electrode intersecting the finger n electrode formed on the n + layer is each of the solar cells. A solar cell module, characterized in that it is formed inside the back surface of the solar cell module.   A substrate including an insulator in which a plurality of holes are formed and a conductor formed on the hole of the insulator is disposed on the bus bar electrode of the solar cell, and the bus bar electrode and the A conductor is electrically connected through the hole, and a bus bar p electrode of one solar cell and a bus bar n electrode of another solar cell are electrically connected by the conductor. The solar cell module according to claim 1 or 2.   The solar cell module according to claim 3, wherein an insulating substrate is installed on the conductor.   The solar cell module according to any one of claims 1 to 4, wherein the solar cell is sealed with a transparent resin between a pair of opposing substrates.

Images