JP2007096040A - Solar cell and method of manufacturing solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a solar cell which restrains the solar cell from warping, and the solar cell. <P>SOLUTION: The solar cell manufacturing method comprises a step of printing a part of the surface of a semiconductor substrate with aluminum paste, a step of forming an aluminum-containing electrode by baking the aluminum paste, a step of forming an insulation film covering the semiconductor substrate surface and the aluminum-containing electrode surface after forming the aluminum-containing electrode, a step of printing a part of the surface of the insulation film with silver paste, and a step of forming a silver-containing electrode on at least the surface of the aluminum-containing electrode by baking the silver paste. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a solar cell and a solar cell, and more particularly, to a method for manufacturing a solar cell and a solar cell capable of suppressing warpage occurring in the solar cell.

  Solar cells that convert sunlight light energy into electrical energy have been actively developed in various structures as interest in global environmental issues increases.

  FIG. 8 shows a schematic cross-sectional view of an example of a conventional solar cell. In this solar cell 1, an n + layer 3 that is an impurity diffusion layer is formed on the light receiving surface of a p-type silicon substrate 2, and an antireflection film 4 and a light receiving surface silver-containing electrode 7 are formed on the n + layer 3. Is formed. A p + layer 5 that is an impurity diffusion layer is formed on the back surface of the silicon substrate 2, an aluminum-containing electrode 6 is formed on the p + layer 5, and a back surface silver-containing material is formed on the aluminum-containing electrode 6. An electrode 8 is formed.

  The manufacturing process of this conventional solar cell is shown in the schematic cross-sectional views of FIGS. First, a p-type silicon substrate 2 shown in FIG. 9A is formed by cutting out a polycrystalline p-type silicon ingot using, for example, a wire saw. Here, since a damaged layer is formed on the surface of the silicon substrate 2 by a wire saw or the like, etching is performed using an alkaline aqueous solution in which isopropyl alcohol is added to an aqueous solution of NaOH (sodium hydroxide) or KOH (potassium hydroxide). Then, the damage layer is removed and irregularities (not shown) are formed on the light receiving surface of the silicon substrate 2.

Next, a dopant solution containing P ₂ O ₅ (phosphorus pentoxide) or the like as a diffusion source is applied to the entire surface of the light receiving surface of the silicon substrate 2 by a spin coater or the like, and then heated, whereby the light receiving surface of the silicon substrate 2 is applied. Phosphorus, which is an n-type impurity, diffuses to form an n + layer 3 on the light receiving surface of the silicon substrate 2 as shown in FIG. 9B.

  Next, as shown in FIG. 9C, an antireflection film 4 is formed on the n + layer 3 on the light receiving surface of the silicon substrate 2 by CVD or the like. Subsequently, an aluminum paste is printed on substantially the entire back surface of the silicon substrate 2 by screen printing or the like, dried, and then baked, whereby aluminum is formed on the back surface of the silicon substrate 2 as shown in FIG. The containing electrode 6 is formed, and the p + layer 5 containing a large amount of aluminum which is a p-type impurity is formed.

Thereafter, a silver paste is printed so as to overlap at least part of the aluminum-containing electrode 6 by screen printing or the like. A silver paste is also printed on the antireflection film 4 by a screen printing method or the like. And by baking after drying these silver paste, as shown in FIG.9 (e), while the back surface silver containing electrode 8 is formed on the aluminum containing electrode 6 in the back surface side of the silicon substrate 2, On the light receiving surface side, the silver containing electrode 7 in contact with the n + layer 3 is formed by the silver paste penetrating the antireflection film 4. Finally, the silicon substrate 2 is cooled to complete the solar cell shown in FIG.
JP 2004-235268 A

  In such a conventional solar cell, an aluminum-containing electrode is formed on substantially the entire back surface of the silicon substrate (see, for example, Patent Document 1). However, in the cooling process after forming the aluminum-containing electrode, there has been a problem that the solar cell is warped due to the difference in thermal expansion coefficient between the aluminum-containing electrode and the silicon substrate. In particular, the spread of solar cells has been promoted for energy saving, and there is a need to further reduce the cost of solar cells, and it is necessary to reduce the thickness and area of the silicon substrate, which accounts for the majority of the material cost. In recent times, this problem is important.

  Then, the objective of this invention is providing the manufacturing method and solar cell of a solar cell which can suppress the curvature which arises in a solar cell.

  The present invention includes a step of printing an aluminum paste on a part of the surface of a semiconductor substrate, a step of forming an aluminum-containing electrode by firing the aluminum paste, and a surface of the semiconductor substrate and the aluminum-containing electrode after the formation of the aluminum-containing electrode. A step of forming an insulating film covering the surface of the substrate, a step of printing a silver paste on a portion of the surface of the insulating film, and a silver-containing electrode on at least a portion of the surface of the aluminum-containing electrode by firing the silver paste. Forming the solar cell.

  According to the first aspect of the method for manufacturing a solar cell of the present invention, a plurality of aluminum-containing electrodes may be formed in a linear shape, and the aluminum-containing electrodes may be arranged in parallel to each other at intervals.

  Here, in the 1st aspect of the manufacturing method of the solar cell of this invention, a silver containing electrode can be formed in the linear form orthogonal to an aluminum containing electrode.

  According to the second aspect of the method for producing a solar cell of the present invention, a plurality of aluminum-containing electrodes may be formed in a linear shape, and the aluminum-containing electrodes may be arranged so as to form a lattice perpendicular to each other.

  Here, in the second aspect of the method for producing a solar cell of the present invention, the silver-containing electrode can be formed only on the aluminum-containing electrode extending in either direction of the lattice.

  According to the third aspect of the method for manufacturing a solar cell of the present invention, a plurality of aluminum-containing electrodes may be formed in an island shape and arranged at intervals.

  Here, in the 3rd aspect of the manufacturing method of the solar cell of this invention, a silver containing electrode can be formed so that an aluminum containing electrode may be connected.

  The present invention also includes an aluminum-containing electrode formed on a part of the surface of the semiconductor substrate, an insulating film formed on a part of the surface of the semiconductor substrate, and at least a part of the surface of the aluminum-containing electrode. It is a solar cell containing a silver containing electrode.

  Here, in the solar cell of this invention, the surface of a semiconductor substrate can be made into the back surface on the opposite side to the light-receiving surface of a semiconductor substrate.

  In the solar cell of the present invention, a plurality of aluminum-containing electrodes may be formed in a linear shape, and the aluminum-containing electrodes may be arranged in parallel to each other at intervals.

  In the solar cell of the present invention, a plurality of aluminum-containing electrodes may be formed linearly, and the aluminum-containing electrodes may be arranged so that the aluminum-containing electrodes are orthogonal to each other to form a lattice.

  In the solar cell of the present invention, a plurality of aluminum-containing electrodes may be formed in an island shape, and the aluminum-containing electrodes may be arranged with a space therebetween.

  In the solar cell of the present invention, the silver-containing electrode may be in contact with a plurality of aluminum-containing electrodes.

  In the present invention, the “light-receiving surface” means a surface of a semiconductor substrate that is usually directed to the incident light side when a solar cell is installed and used.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and solar cell of a solar cell which can suppress the curvature which arises in a solar cell can be provided.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

(Embodiment 1)
FIG. 1A shows a schematic plan view of the back surface of a preferred example of the solar cell of the present invention, and FIG. 1B shows a schematic cross-sectional view along Ib-Ib in FIG. . In this solar cell 1, as shown in FIG. 1A, two relatively wide aluminum-containing electrodes 6 extending in the vertical direction of the paper surface and the horizontal direction of the paper surface are formed on the back surface of the p-type silicon substrate 2. The aluminum-containing electrode 6 is arranged so that 18 aluminum-containing electrodes 6 having a relatively narrow width extending perpendicularly to form a lattice, and the back surface silver-containing electrode 8 has a relatively wide width extending in the vertical direction of the paper surface. Are formed on only a part of the surface of each of the two wide aluminum-containing electrodes 6.

  Further, as shown in FIG. 1B, an n + layer 3 is formed on the light receiving surface of the silicon substrate 2, and an antireflection film 4 and a light receiving surface silver-containing electrode 7 are formed on the n + layer 3. ing. Further, a p + layer 5 that functions as a back surface field (BSF) layer is formed on the back surface of the silicon substrate 2, and the p + layer 5 is formed on the back surface of the silicon substrate 2. Has an aluminum-containing electrode 6 and an insulating film 9 is formed at a location where the p + layer 5 is not formed. A backside silver-containing electrode 8 is formed on the aluminum-containing electrode 6.

  FIGS. 2A to 2F are schematic cross-sectional views of a preferable example of the manufacturing process of the solar cell shown in FIGS. 1A and 1B. First, the light-receiving surface of the silicon substrate 2 made of p-type polycrystal or single crystal shown in FIG. 2A is etched using an alkaline aqueous solution containing NaOH or the like. Here, instead of the alkaline aqueous solution, an acid may be used, and a texture structure is formed by performing anisotropic etching along the crystal orientation by immersing in an etchant obtained by adding isopropyl alcohol or the like to an alkaline aqueous solution such as NaOH or KOH. You may form the micro pyramid-shaped unevenness | corrugation called.

Next, the silicon substrate 2 is subjected to, for example, a vapor phase diffusion using P ₂ O ₅ or POCl ₃ or a diffusion method performed by applying a solution containing a phosphorus compound, for example, at a temperature of 800 ° C. to 950 ° C. By performing heat treatment for not less than 30 minutes and not more than 30 minutes, an n + layer 3 is formed by diffusing phosphorus as an n-type impurity on the light receiving surface of the silicon substrate 2 as shown in FIG.

Next, as shown in FIG. 2C, a titanium oxide film having a thickness of, for example, 60 nm or more and 90 nm or less is formed on the n + layer 3 as the antireflection film 4 by atmospheric pressure CVD. Here, instead of the titanium oxide film, a silicon nitride film having a thickness of 70 nm or more and 100 nm or less formed by a plasma CVD method may be used. When the silicon substrate 2 is made of polycrystalline silicon, the output of the solar cell can be improved by forming a silicon nitride film by the plasma CVD method as the antireflection film 4 by the passivation effect at the polycrystalline grain boundary.

  Subsequently, an aluminum paste is printed on a part of the back surface of the silicon substrate 2 by a screen printing method. In the present invention, as the aluminum paste, conventionally known ones such as those containing aluminum powder and glass frit in the resin can be used.

  Thereafter, the aluminum paste is dried and then baked, for example, at a temperature of 500 ° C. or higher and 900 ° C. or lower, thereby forming the aluminum-containing electrode 6 as shown in FIG. At this time, the p + layer 5 is formed by the diffusion of aluminum on the back surface of the silicon substrate 2. The aluminum-containing electrode 6 is formed on the back surface of the silicon substrate 2 in the pattern shown in the schematic plan view of FIG.

  Next, as shown in FIG. 2E, a silicon oxide film having a thickness of, for example, 5 nm to 100 nm is formed as the insulating film 9 by the CVD method so as to cover the back surface of the silicon substrate 2 and the surface of the aluminum-containing electrode 6. Here, as the insulating film 9, a silicon oxide film having a thickness of, for example, 5 nm to 100 nm formed by a thermal oxidation method, a silicon nitride film having a thickness of, for example, 60 nm to 100 nm formed by a plasma CVD method, or, for example, 50 nm or more A titanium oxide film having a thickness of 100 nm or less may be used. In the present invention, the insulating film 9 is preferably a passivation film that can suppress carrier recombination on the surface of the silicon substrate 2 from the viewpoint of improving the conversion efficiency of the solar cell. Further, when the silicon substrate 2 is made of polycrystalline silicon, the output of the solar cell can be improved by forming a silicon nitride film as the insulating film 9 by a plasma CVD method by a passivation effect at the polycrystalline grain boundary.

  Next, a silver paste is printed on a part of the surface of the antireflection film 4 on the light receiving surface side of the silicon substrate 2 by a screen printing method so that the pattern of the back surface silver-containing electrode 8 shown in FIG. The silver paste is also printed on a part of the surface of the insulating film 9 on the back surface of the silicon substrate 1.

  Here, as a silver paste, conventionally well-known things, such as what contains silver powder and glass frit in resin, can be used, for example. Furthermore, the silver paste printed on the surface of the antireflection film 4 on the light receiving surface side of the silicon substrate 2 can contain an additive containing phosphorus in order to reduce the contact resistance with the n + layer 3. The silver paste printed on the surface of the insulating film 9 on the back side of 2 can also contain an additive or aluminum that reduces the contact resistance with the aluminum-containing electrode 6.

  And after baking the silver paste printed as mentioned above, it bakes at the temperature of 500 degreeC or more and 900 degrees C or less, for example. As a result, as shown in FIG. 2 (f), on the light receiving surface side of the silicon substrate 2, a light receiving surface silver-containing electrode 7 is formed so that the silver paste penetrates the antireflection film 4 and comes into contact with the n + layer 3. On the back surface side of the substrate 2, a back surface silver-containing electrode 8 is formed in which the silver paste penetrates the insulating film 9 and contacts the aluminum-containing electrode 6. Here, the light-receiving surface silver-containing electrode 7 and the back surface silver-containing electrode 8 can each be used for soldering an interconnector for connecting a plurality of solar cells in series or in parallel. Here, the firing temperature of the silver paste is preferably lower than the firing temperature of the aluminum paste. In this case, the output of the solar cell tends to be further improved.

As described above, the solar cell 1 shown in FIGS. 1A and 1B is manufactured.
As described above, in the present invention, since the aluminum-containing electrode is formed on a part of the back surface of the silicon substrate, it is generated due to a difference in thermal expansion coefficient between the aluminum-containing electrode and the silicon substrate in the cooling process after forming the aluminum-containing electrode. It is possible to suppress warping of the solar cell. Thereby, since the crack of a solar cell can be suppressed and a yield can be suppressed significantly, it becomes possible to produce a solar cell at low cost.

  In the above, the light-receiving surface silver-containing electrode may be formed when the aluminum-containing electrode is formed.

(Embodiment 2)
FIG. 4A shows a schematic plan view of the back surface of another preferred example of the solar cell of the present invention, and FIG. 4B is a schematic cross-sectional view taken along IVb-IVb in FIG. Indicates.

  In the solar cell 1 of the present embodiment, as shown in FIG. 4A, 18 aluminum-containing electrodes 6 having a relatively narrow width extending in the left-right direction on the paper surface are formed on the back surface of the p-type silicon substrate 2. The back surface silver-containing electrodes 8 extend in the vertical direction of the paper surface so as to be orthogonal to all the above-described aluminum-containing electrodes 6.

  Further, as shown in FIG. 4B, an n + layer 3 is formed on the light receiving surface of the silicon substrate 2, and an antireflection film 4 and a light receiving surface silver-containing electrode 7 are formed on the n + layer 3. ing. A p + layer 5 that functions as a back surface field layer is formed on the back surface of the silicon substrate 2, and an aluminum-containing electrode 6 is formed on the back surface of the silicon substrate 2 where the p + layer 5 is formed. An insulating film 9 is formed at a location where the p + layer 5 is not formed. A backside silver-containing electrode 8 is formed on the aluminum-containing electrode 6.

  In Embodiment 2, the aluminum-containing electrode 6 is formed in the pattern shown in the schematic plan view of FIG. 5, and the back surface silver-containing electrode 8 is formed in the pattern shown in the schematic plan view of FIG. The other features are the same as those in the first embodiment.

(Embodiment 3)
FIG. 6 (a) shows a schematic plan view of the back surface of still another preferred example of the solar cell of the present invention, and FIG. 6 (b) shows a schematic cross section taken along VIb-VIb of FIG. 6 (a). The figure is shown.

  In solar cell 1 of the present embodiment, as shown in FIG. 6 (a), 216 island-shaped aluminum-containing electrodes 6 are arranged on the back surface of p-type silicon substrate 2 at intervals. And the back surface silver containing electrode 8 is arrange | positioned so that said island-shaped aluminum containing electrode 6 may be connected.

  Further, as shown in FIG. 6B, an n + layer 3 is formed on the light receiving surface of the silicon substrate 2, and an antireflection film 4 and a light receiving surface silver-containing electrode 7 are formed on the n + layer 3. ing. A p + layer 5 that functions as a back surface field layer is formed on the back surface of the silicon substrate 2, and an aluminum-containing electrode 6 is formed on the back surface of the silicon substrate 2 where the p + layer 5 is formed. An insulating film 9 is formed at a location where the p + layer 5 is not formed. A backside silver-containing electrode 8 is formed on the aluminum-containing electrode 6.

  In Embodiment 3, the aluminum-containing electrode 6 is formed in the pattern shown in the schematic plan view of FIG. 7, and the back surface silver-containing electrode 8 is formed in the pattern shown in the schematic plan view of FIG. The other features are the same as those in the first embodiment.

Example 1
The solar cell 1 shown in FIG. 1A and FIG. 1B was produced as follows, and the warpage and output of the solar cell were evaluated.

  First, a silicon substrate 2 made of p-type single crystal silicon having a substantially square plate shape of width 125 mm × length 125 mm × thickness 150 μm was prepared. Next, the surface of the silicon substrate 2 was etched using an aqueous NaOH solution to form a texture structure.

  Next, the light-receiving surface of the silicon substrate 2 on which the texture structure is formed is subjected to a heat treatment at 900 ° C. for 10 minutes after applying a solution containing phosphorus, so that the light-receiving surface of the silicon substrate 2 has n-type impurities. Phosphorus was diffused to form an n + layer 3 having a depth of about 0.5 μm.

  Next, a titanium oxide film having a thickness of 60 nm to 90 nm was formed as an antireflection film 4 on the n + layer 3 by an atmospheric pressure CVD method.

  Subsequently, a silver paste was printed by a screen printing method at a predetermined position on the light receiving surface of the titanium oxide film and dried.

  Also, an aluminum paste was printed at a predetermined position on the back surface of the silicon substrate 2 by a screen printing method and dried.

  Subsequently, the silver paste and the aluminum paste are baked at 700 ° C. to 800 ° C. so that the silver paste penetrates the antireflection film 4 and comes into contact with the n + layer 3. The containing electrode 7 is formed, and further, aluminum is dispersed from the above aluminum paste, whereby an aluminum containing electrode 6 having a thickness of several tens of μm is formed on the back surface of the silicon substrate 2 in the pattern shown in FIG. P + layer 5 was formed.

  Thereafter, an insulating film 9 made of silicon oxide having a thickness of 100 nm serving as a passivation film was formed by using the CVD method so as to cover the back surface of the silicon substrate 2 and the surface of the aluminum-containing electrode 6.

  Then, a silver paste was printed on a part of the surface of the insulating film 9 corresponding to the portion of the surface of the insulating film 9 where the aluminum-containing electrode 6 is formed and dried.

  Next, the silver paste printed on the surface of the insulating film 9 was baked at 500 ° C. to 800 ° C., thereby forming the back surface silver-containing electrode 8 having a thickness of several tens of μm in the pattern shown in FIG.

  Finally, the solar cell of Example 1 was produced by cooling the silicon substrate 2 after the formation of the back surface silver-containing electrode 8.

  For comparison, a solar cell of Comparative Example 1 was fabricated using the same method and the same conditions as in Example 1 except that no insulating film was formed and an aluminum-containing electrode was formed on the entire back surface of the silicon substrate.

  When the solar cell of Example 1 and the solar cell of Comparative Example 1 were compared, the warpage of the solar cell of Example 1 was reduced compared to the solar cell of Comparative Example 1. Further, the solar cell of Comparative Example 1 was frequently cracked in the solar cell transport and modularization process, whereas the solar cell of Example 1 was significantly cracked compared to the solar cell of Comparative Example 1. It was possible to reduce. Further, the output of the solar cell of Example 1 was substantially equal to the output of the solar cell of Comparative Example 1.

(Example 2)
The solar cell 1 shown in FIGS. 4A and 4B was produced as follows, and the warpage and output of the solar cell were evaluated.

  First, a silicon substrate 2 made of a substantially square plate-like p-type single crystal silicon having a width of 155 mm, a length of 155 mm, and a thickness of 100 μm was prepared. Next, the surface of the silicon substrate 2 was etched using an aqueous NaOH solution to form a texture structure.

  Next, the light-receiving surface of the silicon substrate 2 on which the texture structure is formed is subjected to a heat treatment at 900 ° C. for 10 minutes after applying a solution containing phosphorus, so that the light-receiving surface of the silicon substrate 2 has n-type impurities. Phosphorus was diffused to form an n + layer 3 having a depth of about 0.5 μm.

  Next, a titanium oxide film having a thickness of 60 nm to 90 nm was formed as an antireflection film 4 on the n + layer 3 by an atmospheric pressure CVD method.

  Subsequently, a silver paste was printed by a screen printing method at a predetermined position on the light receiving surface of the titanium oxide film and dried.

  Also, an aluminum paste was printed at a predetermined position on the back surface of the silicon substrate 2 by a screen printing method and dried.

  Subsequently, the silver paste and the aluminum paste are baked at 600 ° C. to 800 ° C. so that the silver paste penetrates the antireflection film 4 and comes into contact with the n + layer 3. The containing electrode 7 is formed, and further, aluminum is dispersed from the above aluminum paste, whereby an aluminum containing electrode 6 having a thickness of several tens of μm is formed on the back surface of the silicon substrate 2 in the pattern shown in FIG. P + layer 5 was formed.

  Thereafter, an insulating film 9 made of silicon nitride having a thickness of 80 nm and serving as a passivation film was formed using the CVD method so as to cover the back surface of the silicon substrate 2 and the surface of the aluminum-containing electrode 6.

  Then, a silver paste was printed on a part of the surface of the insulating film 9 corresponding to the portion of the surface of the insulating film 9 where the aluminum-containing electrode 6 is formed and dried.

  Next, the silver paste printed on the surface of the insulating film 9 is baked at a temperature lower than the temperature at the time of baking the aluminum paste in the range of 500 ° C. to 800 ° C. to obtain a pattern shown in FIG. A back surface silver-containing electrode 8 having a thickness of several tens of μm was formed.

As described above, the solar cell of Example 2 was produced.
For comparison, a solar cell of Comparative Example 2 was produced in the same manner and under the same conditions as in Example 2 except that no insulating film was formed and an aluminum-containing electrode was formed on the entire back surface of the silicon substrate.

  When the solar cell of Example 2 and the solar cell of Comparative Example 2 were compared, the warpage of the solar cell of Example 2 was reduced compared to the solar cell of Comparative Example 2. Further, the solar cell of Comparative Example 2 was frequently cracked in the solar cell transport and modularization process, whereas the solar cell of Example 2 was significantly cracked compared to the solar cell of Comparative Example 2. It was possible to reduce. Furthermore, the output of the solar cell of Example 2 was substantially equal to the output of the solar cell of Comparative Example 2.

(Example 3)
The solar cell 1 shown in FIGS. 6A and 6B was produced as follows, and the warpage and output of the solar cell were evaluated.

  First, a silicon substrate 2 made of p-type polycrystalline silicon having a substantially square plate shape of width 125 mm × length 125 mm × thickness 50 μm was prepared. Next, the surface of the silicon substrate 2 was etched using an aqueous NaOH solution to form a texture structure.

  Next, after applying a solution containing phosphorus to the etched light receiving surface of the silicon substrate 2, heat treatment is performed at 900 ° C. for 10 minutes to diffuse phosphorus, which is an n-type impurity, on the light receiving surface of the silicon substrate 2. Thus, an n + layer 3 having a depth of about 0.5 μm was formed.

  Next, a silicon nitride film having a thickness of 60 nm to 90 nm was formed as an antireflection film 4 on the n + layer 3 by plasma CVD.

  Subsequently, an aluminum paste was printed at a predetermined position on the back surface of the silicon substrate 2 by a screen printing method and dried.

  Subsequently, by baking the aluminum paste at 600 ° C. to 800 ° C., aluminum is dispersed from the aluminum paste, so that an aluminum-containing electrode 6 having a thickness of several tens of μm is formed on the back surface of the silicon substrate 2 in FIG. A p + layer 5 having a depth of about 10 μm and a pattern shown was formed.

  Thereafter, an insulating film 9 made of silicon nitride having a thickness of 80 nm and serving as a passivation film was formed by plasma CVD so as to cover the back surface of the silicon substrate 2 and the surface of the aluminum-containing electrode 6.

  Then, a silver paste was printed at a predetermined position on the surface of the antireflection film 4 by a screen printing method and then dried. Subsequently, a silver paste was printed on the surface of the insulating film 9 corresponding to the portion of the surface of the insulating film 9 where the aluminum-containing electrode 6 is formed and dried.

  Next, the silver paste printed on the surface of the insulating film 9 is baked at a temperature lower than the temperature at the time of baking the aluminum paste in the range of 500 ° C. to 800 ° C., so that the silver paste becomes the antireflection film 4. A light receiving surface silver-containing electrode 7 having a thickness of several tens of μm that penetrates the n + layer 3 and formed into a pattern shown in FIG. 6A was formed, and a back surface silver-containing electrode 8 having a thickness of several tens of μm was formed.

As described above, the solar cell of Example 3 was produced.
For comparison, a solar cell of Comparative Example 3 was fabricated using the same method and the same conditions as in Example 3 except that no insulating film was formed and an aluminum-containing electrode was formed on the entire back surface of the silicon substrate.

  When the solar cell of Example 3 and the solar cell of Comparative Example 3 were compared, the warpage of the solar cell of Example 3 was reduced compared to the solar cell of Comparative Example 3. Further, the solar cell of Comparative Example 3 was frequently cracked in the solar cell transport and modularization process, whereas the solar cell of Example 3 was significantly cracked compared to the solar cell of Comparative Example 3. It was possible to reduce. Furthermore, the output of the solar cell of Example 3 was substantially equal to the output of the solar cell of Comparative Example 3.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. 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, the aluminum paste is printed on a part of the surface of the semiconductor substrate to form the aluminum-containing electrode, so that the thermal expansion between the aluminum-containing electrode and the semiconductor substrate in the cooling process after the formation of the aluminum-containing electrode. Warpage of the solar cell caused by the coefficient difference can be suppressed. Thereby, since the crack of a solar cell can be suppressed and a yield can be suppressed significantly, it becomes possible to produce a solar cell at low cost. Furthermore, by forming an insulating film such as silicon oxide, titanium oxide, or silicon nitride on the back surface of the semiconductor substrate using a CVD method or the like, the passivation effect on the back surface of the semiconductor substrate (re-carriers on the back surface of the semiconductor substrate is regenerated). In addition to improving the output of the solar cell due to the effect of inhibiting the coupling, the light directly incident from the back side of the semiconductor substrate can also be absorbed into the solar cell, so the output of the solar cell is the output of the conventional solar cell It tends to improve.

(A) is a typical top view of the back surface of the preferable example of the solar cell of this invention, (b) is typical sectional drawing along Ib-Ib of (a). (A) is typical sectional drawing of an example of the silicon substrate used for this invention, (b) is typical sectional drawing of the silicon substrate shown to (a) in which the n <+> layer was formed in the light-receiving surface. (C) is a schematic cross-sectional view of the silicon substrate shown in (b) in which an antireflection film is formed on the light receiving surface, and (d) is shown in (c) in which an aluminum-containing electrode is formed on the back surface. It is a typical sectional view of a silicon substrate, (e) is a typical sectional view of a silicon substrate shown in (d) in which an insulating film was formed, and (f) is an acceptance surface silver content electrode and back surface silver content. It is typical sectional drawing of the silicon substrate shown to (e) in which the electrode was formed. It is a typical top view which shows an example of the back surface after the aluminum containing electrode formation of the silicon substrate used for this invention. (A) is a schematic top view of the back surface of another preferable example of the solar cell of this invention, (b) is typical sectional drawing along IVb-IVb of (a). It is a typical top view which shows another example of the back surface after the aluminum containing electrode formation of the silicon substrate used for this invention. (A) is a schematic top view of the back surface of another preferable example of the solar cell of this invention, (b) is typical sectional drawing along VIb-VIb of (a). It is a typical top view which shows another example of the back surface after the aluminum containing electrode formation of the silicon substrate used for this invention. It is typical sectional drawing of an example of the conventional solar cell. (A) is typical sectional drawing of an example of the silicon substrate used in the conventional method, (b) is typical sectional drawing of the silicon substrate shown to (a) in which the n <+> layer was formed in the light-receiving surface. (C) is a schematic cross-sectional view of the silicon substrate shown in (b) in which an antireflection film is formed on the light receiving surface, and (d) is in (c) in which an aluminum-containing electrode is formed on the back surface. It is typical sectional drawing of the silicon substrate shown, (e) is typical sectional drawing of the silicon substrate shown to (d) in which the light-receiving surface silver containing electrode and the back surface silver containing electrode were formed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Solar cell, 2 Silicon substrate, 3 n <+> layer, 4 Antireflection film, 5 p <+> layer, 6 Aluminum containing electrode, 7 Light-receiving surface silver containing electrode, 8 Back surface silver containing electrode, 9 Insulating film.

Claims (13)

Printing an aluminum paste on a part of the surface of the semiconductor substrate;
Forming an aluminum-containing electrode by firing the aluminum paste;
Forming an insulating film covering the surface of the semiconductor substrate and the surface of the aluminum-containing electrode after the formation of the aluminum-containing electrode;
Printing a silver paste on a part of the surface of the insulating film;
Forming a silver-containing electrode on at least a part of the surface of the aluminum-containing electrode by firing the silver paste;
A method for manufacturing a solar cell, comprising:   2. The method of manufacturing a solar cell according to claim 1, wherein a plurality of the aluminum-containing electrodes are formed in a linear shape, and the aluminum-containing electrodes are arranged in parallel with each other at intervals.   The said silver containing electrode is formed in the linear form orthogonal to the said aluminum containing electrode, The manufacturing method of the solar cell of Claim 2 characterized by the above-mentioned.   2. The method for manufacturing a solar cell according to claim 1, wherein a plurality of the aluminum-containing electrodes are formed in a linear shape, and the aluminum-containing electrodes are arranged so as to be orthogonal to each other to form a lattice.   The said silver containing electrode is formed only on the said aluminum containing electrode extended in any one direction of the said grating | lattice, The manufacturing method of the solar cell of Claim 4 characterized by the above-mentioned.   2. The method for manufacturing a solar cell according to claim 1, wherein a plurality of the aluminum-containing electrodes are formed in an island shape and are arranged with a space therebetween.   The method for manufacturing a solar cell according to claim 6, wherein the silver-containing electrode is formed to connect the aluminum-containing electrode.   An aluminum-containing electrode formed on a part of the surface of the semiconductor substrate, an insulating film formed on a part of the surface of the semiconductor substrate, and a silver-containing electrode formed on at least a part of the surface of the aluminum-containing electrode And a solar cell.   The solar cell according to claim 8, wherein the front surface of the semiconductor substrate is a back surface opposite to a light receiving surface of the semiconductor substrate.   10. The solar cell according to claim 8, wherein a plurality of the aluminum-containing electrodes are formed in a linear shape, and the aluminum-containing electrodes are arranged in parallel to each other at intervals.   The aluminum-containing electrode is formed in a plurality of lines, and the aluminum-containing electrode is disposed so that the aluminum-containing electrodes are orthogonal to each other to form a lattice. The solar cell described.   10. The solar cell according to claim 8, wherein a plurality of the aluminum-containing electrodes are formed in an island shape, and the aluminum-containing electrodes are spaced apart from each other.   The solar cell according to claim 8, wherein the silver-containing electrode is in contact with a plurality of the aluminum-containing electrodes.

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