JP2004247596A - Solar battery element, manufacturing method thereof, and solar battery module using the element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a solar battery element wherein its long-term reliability can be secured by using its coating material containing no lead, and its external appearance is also made favorable. <P>SOLUTION: The solar battery element has electrodes 5, 6 on the surfaces of a semiconductor substrate 1. The surfaces of the electrodes 5, 6 are coated respectively with coating layers 7 having excised portions 9. Each inner lead coated with a solder containing silver is connected with each excised portion 9. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solar cell element, a method for manufacturing a solar cell element, and a solar cell module, and more particularly to a solar cell element having an electrode on a surface, a method for manufacturing a solar cell element, and a solar cell module.
[0002]
2. Description of the Related Art
FIG. 1 shows a cross-sectional view of a conventional solar cell element. In FIG. 1, 1 is a semiconductor substrate, 2 is a diffusion layer, 3 is an antireflection film, 4 is a BSF layer, 5 is a front electrode, 6 is a back electrode, and 11 is a solder layer.
[0003]
For example, on the front side of the P-type silicon substrate 1, an N-type diffusion layer 2 containing P and an antireflection film 3 made of a silicon nitride film or the like are formed. On the back side of the silicon substrate 1, there is provided a high-concentration P-type BSF layer 4 formed by diffusing aluminum, for example. Further, electrodes 5 and 6 are formed on the front and back surfaces of the silicon substrate 1, respectively. Furthermore, the surfaces of the electrodes 5 and 6 are covered with a solder layer 11 to connect the solar cell elements in an after-process to facilitate connection with inner leads, and to ensure long-term reliability of the solar cell elements. (See, for example, Patent Document 1).
[0004]
However, Pb contained in general Sn-Pb eutectic solder has become a problem in recent years while environmental problems have been taken up, and lead-free solder and lead-less solder are being developed. However, it is difficult to select a lead-free solder or a lead-less solder suitable for a solar cell element from the viewpoint of its use temperature and long-term reliability, and no solder has been developed that is superior to the conventional Sn-Pb eutectic solder.
[0005]
In addition, since the portion of the antireflection film 3 usually exhibits a color from blue to almost black, there is a difference in color from the portion of the solder layer 11, which is not preferable in appearance.
[0006]
The present invention has been made in view of such a problem, and a long-term reliability can be ensured by using a coating material containing no lead, and a solar cell element which is also preferable in appearance, a method for manufacturing the same, and the solar cell element An object of the present invention is to provide a solar cell module using the same.
[0007]
[Patent Document 1]
JP-A-2002-353377
[Means for Solving the Problems]
In order to achieve the above object, the solar cell element according to claim 1 is a solar cell element having an electrode on a surface of a semiconductor substrate, wherein the surface of the electrode is covered with a coating layer having a cutout. And
[0009]
In the above solar cell element, it is desirable that the surface of the electrode is in direct contact with the coating layer.
[0010]
Further, in the above solar cell element, it is preferable that the coating layer is a glass layer.
[0011]
Further, it is desirable that the electrode contains silver as a main component.
[0012]
Further, the glass layer is desirably colored.
[0013]
Further, in the method for manufacturing a solar cell element according to claim 6, in the method for manufacturing a solar cell element in which an electrode material is formed by applying and baking an electrode material on a surface of a semiconductor substrate, glass is mainly used on the surface of the electrode. A glass layer is formed on the surface of the electrode by applying and baking a paste.
[0014]
In the method for manufacturing a solar cell element, the softening point of the glass paste is desirably equal to or lower than the temperature at which the electrode material is baked.
[0015]
In the method for manufacturing a solar cell element, it is preferable that the glass paste contains sodium oxide, boron oxide, and silicon oxide.
[0016]
In the method for manufacturing a solar cell element, the glass paste preferably contains a pigment.
[0017]
Further, in the solar cell module according to claim 10, in a solar cell module in which the electrodes of the plurality of solar cell elements are connected by inner leads having a solder layer on the surface, the inner part is formed in a cutout portion of the coating layer of the electrode. The lead is connected, and the solder layer contains silver.
[0018]
Silver contained in the solar cell module and the solder layer is desirably 0.5 to 5% by weight.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of a solar cell element according to the present invention, and FIG. 2 is a plan view when the solar cell element according to the present invention is viewed from the front side.
[0020]
1 and 2, 1 is a semiconductor substrate, 2 is a diffusion layer, 3 is an antireflection film, 4 is a BSF layer, 5 is a front electrode, 6 is a back electrode, 7 is a coating layer, and 9 is a cutout.
[0021]
Semiconductor substrate 1 is made of single crystal or polycrystalline silicon or the like. This silicon substrate 1 is a substrate containing about 1 × 10 ¹⁶ to 1 × 10 ¹⁸ atoms / cm ³ of one conductivity type semiconductor impurity such as boron (B) and having a specific resistance of about 1.5 Ω · cm. In the case of a single crystal silicon substrate, it is formed by a pulling method or the like, and in the case of a polycrystalline silicon substrate, it is formed by a casting method or the like. A polycrystalline silicon substrate can be mass-produced and is more advantageous than a single crystal silicon substrate in terms of manufacturing cost. An ingot formed by a pulling method or a casting method is sliced into a thickness of about 300 to 500 μm, and cut into a size of about 10 cm × 10 cm or 15 cm × 15 cm to obtain a semiconductor substrate 1.
[0022]
A diffusion layer 2 is formed on the front side of the semiconductor substrate 1. The diffusion layer 2 is formed by placing the semiconductor substrate 1 in a diffusion furnace and heating the semiconductor substrate 1 in phosphorus oxychloride (POCl ₃ ) or the like, so that the surface portion of the semiconductor substrate 1 has phosphorus atoms of 1 × 10 ¹⁶ to 1 × 10 ^16. It is formed by diffusing about × 10 ¹⁸ atoms / cm ³ . The diffusion layer 2 is formed at a depth of about 0.2 to 0.5 μm, and is formed so that the sheet resistance becomes 40Ω / □ or more.
[0023]
An antireflection film 3 is formed on the surface side of the semiconductor substrate 1. The antireflection film 3 is made of, for example, a silicon nitride film, and is formed by a plasma CVD method using a mixed gas of silane and ammonia. The antireflection film 3 is provided to prevent light from being reflected on the surface of the semiconductor substrate 1 and to effectively take in light into the semiconductor substrate 1.
[0024]
A front surface electrode 5 is formed on the front surface side of the semiconductor substrate 1, and a back surface electrode 6 is formed on the back surface side. The front surface electrode 5 and the back surface electrode 6 are formed by applying an electrode material on the back surface side of the semiconductor substrate 1, etching a portion corresponding to the front surface electrode 5 of the antireflection film 3, applying the electrode material, and firing. Form. Alternatively, an electrode material is applied on the back surface side, and the electrode material is applied directly on the antireflection film 3 and baked. Thereby, the front surface electrode 5 and the back surface electrode 6 are formed. As an electrode material, a paste is prepared by adding 0.1 to 5 parts by weight of glass frit to silver powder and an organic vehicle with respect to 100 parts by weight of silver to form a paste, and the electrode paste is printed by a screen printing method. Then, it is baked by baking at 650 to 800 ° C. for about 1 to 30 minutes.
[0025]
In the present invention, the covering layer 7 having the cutout 9 is formed on the surface of the front electrode 5 and the back electrode 6. By doing so, the surfaces of the electrodes 5 and 6 except for the cutout portion 9 do not come into contact with the outside air, so that oxidation and moisture absorption can be prevented without coating with a solder layer, and long-term reliability is improved. Can be secured.
[0026]
The cutout 9 may be formed on the entire surface where the inner lead is to be arranged, and all of the cutout 9 may be connected to the inner lead. For example, the cutout 9 is formed on the surface of the front electrode 5 and the back electrode 6 at predetermined intervals. May be. This is to prevent the solar cell element and the inner lead from being pulled together during welding due to the difference in the coefficient of thermal expansion between the solar cell element and the inner lead, thereby preventing the solar cell element from being cracked or the solar cell element from being peeled off from the inner lead.
[0027]
At this time, the surfaces of the electrodes 5 and 6 are preferably in direct contact with the coating layer 7. By doing so, it is not necessary to consider the influence of the substance existing between the electrodes 5 and 6 and the coating layer 7, so that it is possible to more effectively prevent oxidation and moisture absorption of the surfaces of the electrodes 5 and 6. , It is possible to effectively secure long-term reliability.
[0028]
Further, it is better that the coating layer 7 is a glass layer. By doing so, the coating layer 7 becomes strong even if the thickness is reduced, so that oxidation and moisture absorption of the surfaces of the electrodes 5 and 6 can be more effectively prevented, and long-term reliability can be effectively secured. In addition, since the unevenness on the surface of the solar cell element 8 can be reduced, the solar cell element 8 can be prevented from cracking even when an external force is applied to the entire surface of the solar cell element 8 in a later step. Further, since the glass layer has a light-transmitting property, even if the glass layer is formed so as to protrude to the light receiving surface portion other than the surface electrode 5 on the front surface side, it is possible to suppress the deterioration of the characteristics due to the decrease in the light receiving area.
[0029]
This glass layer is formed by applying and baking a glass paste containing glass powder as a main component, an organic solvent and a binder, etc. on the surfaces of the electrodes 5 and 6.
[0030]
The softening point of the glass paste at this time is preferably lower than the temperature at which the electrode material is baked. By doing so, it is possible to prevent the problem that the previously baked electrode is affected when the glass paste is baked, or that the electrode reacts again, which adversely affects the output characteristics of the solar cell element. Is not affected.
[0031]
Further, the glass paste preferably contains sodium oxide, boron oxide, and silicon oxide. By not using lead as the material in this way, the same long-term reliability effect as obtained with the conventional Sn-Pb eutectic solder can be obtained without using lead, which has an adverse effect on the environment. No longer has any effect. For example, so-called borosilicate glass or the like can be suitably used.
[0032]
Further, by coloring the glass layer which is the coating layer 7, the color tone of the antireflection film 3 can be made uniform, and the appearance due to the difference in the color tone of the antireflection film 3 and the solder layer 11, which has been a problem in the related art, can be obtained. It is possible to solve the problem of disharmony. In order to color the glass layer, a pigment may be contained in the glass paste. Examples of such a pigment include a Co oxide.
[0033]
In addition, a resin or the like can be used as the coating layer 7 in addition to glass.
[0034]
FIG. 3 is a diagram for explaining the structure of the solar cell module according to the present invention. In the figure, 1 is a solar cell element, 10 is an inner lead, 5 in the solar cell element 1 is a front electrode, 6 is a back electrode, 7 is a coating layer, and 9 is a cutout.
[0035]
In the solar cell module according to the present invention, the inner lead 10 having a solder layer on the surface is connected to the surface of the electrodes 5 and 6 at the cutout 9 of the covering layer 7. By doing so, the coating layer 7 does not need to play the role of connection with the inner lead 11 that the solder layer 11 that has coated the electrode surface of the conventional solar cell element has played. It is not necessary to add a restriction in consideration of adhesion to the inner lead 11.
[0036]
At this time, it is preferable that the material that is the main component of the electrodes 5 and 6 be contained in the solder layer on the surface of the inner lead 11. By doing so, the electrodes 5, 6 and the inner leads can be easily bonded. For bonding, for example, heating is performed using a soldering iron or hot air, and heat welding may be performed by pressing. As such a material used for the electrodes 5 and 6, it is possible to use gold, platinum or the like having a low electric resistance, but it is better to use silver from the viewpoint of cost. That is, the electrodes 5 and 6 may be formed of a material containing silver as a main component, and the same silver may be contained in the solder layer on the surface of the inner lead 11.
[0037]
At this time, the amount of silver contained in the solder layer on the surface of the inner lead 11 is preferably 0.5 to 5% by weight. If the content is 0.5% by weight or less, problems such as insufficient adhesion strength with the electrodes 5 and 6, an increase in the temperature required for adhesion, and an increase in time may occur. If the content is 5% by weight or more, a problem that the solder layer on the surface of the inner lead 11 becomes brittle occurs.
[0038]
As the solder containing silver as described above, in addition to the conventional method of adding silver to Sn-Pb eutectic solder, Sn-Ag, Sn-Cu, Sn-Zn, Sn-Sb, and Sn-In are used. It is possible to use a so-called lead-free solder that does not contain lead, such as a Sn-Bi-based or Sn-Bi-based system. desirable.
[0039]
The present invention is not limited to the above embodiment, and many modifications and changes can be made within the scope of the present invention. For example, the structure of the solar cell element is not limited to this, and the solar cell element can be used for a solar cell element having electrodes on only one side, and is not limited to a crystalline silicon solar cell element.
[0040]
【The invention's effect】
As described above in detail, in the solar cell element according to claim 1, the covering layer having the cutout is formed on the surface of the front electrode and the back electrode. By doing so, the surface of the electrode except for the cutout portion does not come into contact with the outside air, so that oxidation and moisture absorption can be prevented without using solder, and long-term reliability can be secured.
[0041]
At this time, the surface of the electrode is preferably in direct contact with the coating layer. By doing so, it is not necessary to consider the influence of what exists between the electrode and the coating layer, so that oxidation and moisture absorption on the surface of the electrode can be more effectively prevented, and long-term reliability can be effectively improved. Can be secured.
[0042]
Further, the coating layer is preferably a glass layer. By doing so, a strong coating layer can be obtained even if the thickness is reduced, and oxidation and moisture absorption on the surface of the electrode can be more effectively prevented. Since the unevenness on the surface of the battery element can be reduced, the solar cell element can be prevented from cracking even when external force is applied to the entire surface of the solar cell element in a later step. Further, since the glass layer has a light-transmitting property, even if the glass layer is formed so as to protrude to the light receiving surface portion other than the surface electrode on the front surface side, it is possible to suppress a decrease in characteristics due to a decrease in the light receiving area.
[0043]
In the method for manufacturing a solar cell element according to claim 6, the glass layer is formed by applying and baking a glass paste containing glass powder as a main component, an organic solvent, a binder, and the like on the surface of the electrode.
[0044]
At this time, the softening point of the glass paste is preferably lower than the temperature at which the electrode material is baked. By doing so, it is possible to prevent the problem that the previously baked electrode is affected when the glass paste is baked or that the electrode reacts again, which adversely affects the output characteristics of the solar cell element. Is not affected.
[0045]
Further, the glass paste preferably contains sodium oxide, boron oxide, and silicon oxide. By not using lead as the material in this way, the same long-term reliability effect as obtained with the conventional Sn-Pb eutectic solder can be obtained without using lead, which has an adverse effect on the environment. No longer has any effect.
[0046]
In addition, by coloring the glass layer, which is the coating layer, it is possible to match the color tone of the anti-reflection film with the color tone of the anti-reflection film and the solder layer, which was a conventional problem, because of the difference in color tone of the solder layer. Can be eliminated. In order to color the glass layer, a pigment may be contained in the glass paste.
[0047]
In the solar cell module according to the tenth aspect, the surface of the electrode and the inner lead having a solder layer on the surface are connected at the cutout portion of the coating layer. By doing so, it is not necessary for the coating layer to play the role of connection with the inner lead, which was performed by the solder layer that was coated on the electrode surface of the conventional solar cell element. There is no need to add restrictions in consideration of adhesion.
[0048]
At this time, it is better that the silver material, which is the main component of the electrode, be contained in the solder layer on the surface of the inner lead. This makes it possible to easily bond the electrode and the inner lead.
[0049]
At this time, if the amount of silver contained in the solder layer on the surface of the inner lead is 0.5 to 5% by weight, sufficient bonding strength with the electrode can be obtained, and the temperature required for bonding increases, And the solder layer on the surface of the inner lead does not become brittle.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing one embodiment of a solar cell element according to the present invention.
FIG. 2 is a plan view showing one embodiment of a solar cell element according to the present invention.
FIG. 3 is a diagram illustrating an embodiment of a solar cell module according to the present invention.
FIG. 4 is a cross-sectional view illustrating a structure of a conventional solar cell element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Diffusion layer, 3 ... Anti-reflection film, 4 ... BSF layer, 5 ... Surface electrode, 6 ... Back electrode, 7 ... Coating layer, 8 ... Solar cell element, 9 ... Incision, 10 ... Inner lead, 11 ... Solder layer

Claims (11)

A solar cell element having an electrode on a surface of a semiconductor substrate, wherein the surface of the electrode is covered with a coating layer having a cutout. The solar cell element according to claim 1, wherein a surface of the electrode is in direct contact with the coating layer. The solar cell element according to claim 2, wherein the coating layer is a glass layer. The solar cell element according to claim 1, wherein the electrode contains silver as a main component. The solar cell element according to claim 3, wherein the glass layer is colored. In a method for manufacturing a solar cell element in which an electrode is formed by applying and baking an electrode material on a surface of a semiconductor substrate, a paste containing glass as a main component is applied to the surface of the electrode, and the electrode is baked. A method for manufacturing a solar cell element, comprising forming a glass layer. 7. The method according to claim 6, wherein the softening point of the glass paste is equal to or lower than a temperature at which the electrode material is baked. The method according to claim 6, wherein the glass paste contains at least one of sodium oxide, boron oxide, and silicon oxide. The method for manufacturing a solar cell element according to claim 6, wherein the glass paste contains a pigment. A solar cell module in which the electrodes of the plurality of solar cell elements according to any one of claims 1 to 5 are connected by an inner lead having a solder layer on a surface, wherein the inner lead is provided at a cutout portion of the coating layer of the electrode. The solar cell module being connected, wherein the solder layer contains the same material as the main component of the electrode. The solar cell module according to claim 10, wherein the same material as the main component of the electrode is silver, and the silver is contained in an amount of 0.5 to 5% by weight based on the total weight of the solder.

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