JP2003142703A - Method for manufacturing integrated solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an integrated solar battery capable of executing the conductive bonding of an electrode and a leader in a much lower temperature than that in solder without using any general solder. SOLUTION: A finger bar and a bus bar 15B made of silver paste are formed as the surface electrode of a solar battery element having a semiconductor junction. A conductive bonding part 20A constituted of alloy containing indium and tin is formed on the surface of a lead wire 12. The conductive bonding part may be formed on the surface of an electrode such as the bus bar 15B. This conductive bonding part 20A is of low-melted structure so that the conductive bonding of the leader 12 to the bus bar 15B can be executed in a low temperature. Especially, the bonding of the lead wire 12 to the bus bar 15B is executed in a temperature where a thermoplastic film 30 is crosslinked, that is, temperatures ranging from 150 deg.C to 160 deg.C so that the bonding of the lead wire 12 and the bonding of the thermoplastic film 30 can be executed in parallel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an integrated solar cell suitable for manufacturing an integrated single crystal or polycrystalline silicon solar cell.

[0002]

2. Description of the Related Art A crystalline solar cell manufactured on a monocrystalline or polycrystalline silicon substrate is usually made up of several or several tens of solar cell elements (cells) by a leader line made of, for example, copper (Cu). It is used in the form of integrated solar cells (modules) connected in series. The voltage that can be generated by one solar cell element is 1 V or less, but it is possible to meet the working voltage by using an integrated solar cell.

For example, when solar cell elements each having a large area of 5 cm × 5 cm or more are integrated, a large current may flow through the electrodes of each solar cell element, especially the bus bar, and the bus bar may generate heat to cause a voltage drop. Therefore, after the electrodes of the solar cell element are formed, the solar cell element is dipped in a solder bath and the solder is attached to the surface of the electrode to reduce the electrical resistance of the electrode. However, since solder is insufficient for the bus bar alone, solder attached to the bus bar is used to bond a lead wire for connecting the solar cell elements in series to prevent heat generation and voltage drop due to a large current. The ends of the lead lines bonded along the bus bar are connected to the electrodes of the adjacent solar cell elements.

After forming the electrodes in this way, for example, EVA (ethylene vinyl acetate) is formed on the surface of the solar cell element.
A transparent thermoplastic resin film having light resistance, such as glass, is adhered to protect the electrodes and the like on the surface of the solar cell element.

[0005]

Conventionally, solder has been used to electrically bond the lead wire and the electrode. Common solders that have been conventionally used are tin (Sn) and lead (Pn).
It is made of an alloy with b), and in recent years, environmental pollution due to lead contained in solder has become a problem. Although solar cells are attracting attention as clean energy, since solder is used for the electrodes, there is a possibility that lead contained in the solder may cause environmental pollution during recovery or disposal. The life of solar cells is semipermanently longer than the life of ordinary home appliances of 10 years. If the service life of a solar cell is 20 years, then 20
It will be collected after a year. For general household appliances, lead-free solder is already being used for product development, but for solar cells as well, if you do not take immediate safety measures, even if general electrical products are switched to lead-free solder,
Environmental problems due to lead in the solder of discarded solar cells will continue.

The lead-free solder has a structure in which various elements other than lead are added to tin, but there are many kinds of material candidates at present, and the standard has not been established yet. Needless to say, lead-free solders with different compositions are inconvenient for recovery, but even if the global standard for lead-free solders is established, it will be difficult to convert them to other raw materials after recovery because of the cost of smelting.

The temperature at which the thermoplastic film adhered to the surface of the solar cell element crosslinks is about 150.degree.
If the lead wire and the electrode can be conductively bonded at a temperature of about 150 ° C., the thermoplastic film and the lead wire can be bonded in parallel. However, for the conductive adhesion at about 150 ° C, general solder whose working temperature is about 235 ° C cannot be used, and a low-temperature silver paste or an epoxy-based adhesive mixed with a conductive filler is mainly used. Used for. This bonding method has problems in reliability such as insufficient strength and low electric conductivity,
Due to its high cost, it is rarely used in solar cells that are used for a long time.

The present invention has been made in view of the above problems, and an object thereof is an integrated type in which an electrode and a lead wire can be conductively bonded at a temperature lower than that of solder without using general solder. It is to provide a method for manufacturing a solar cell.

[0009]

A method of manufacturing an integrated solar cell according to the present invention is an integrated solar cell in which a plurality of solar cell elements each including a semiconductor junction portion and an electrode formed on a semiconductor substrate are connected in series by a lead wire. A solar cell is manufactured, and electrodes are formed using indium (In) or an alloy containing indium.

Specifically, the method of manufacturing an integrated solar cell according to the present invention comprises the steps of forming a semiconductor junction on each of a plurality of semiconductor substrates and forming an electrode on the surface of each of the plurality of semiconductor substrates. A step of forming a plurality of solar cell elements each including a semiconductor junction and an electrode, and the surface of the lead wire or the surface of the electrode for connecting the plurality of solar cell elements in series, using indium or an alloy containing indium ,
It includes a step of forming a conductive adhesive portion, a step of adhering a lead wire to an electrode using the conductive adhesive portion, and a step of connecting a plurality of solar cell elements in series by a lead wire. Furthermore, the step of adhering the leader line using the conductive adhesive portion,
It is preferable to perform the adhesion of the leader line and the adhesion of the thermoplastic films in parallel by performing the operation at a temperature at which the thermoplastic films for protecting the surfaces of the plurality of solar cell elements are crosslinked. For that purpose, specifically, it is preferable to perform the step of adhering the leader line using the conductive adhesive portion at the same temperature as the adhering temperature of the thermoplastic film. As an example, the adhesive temperature of the thermoplastic film is the same as that of the conductive adhesive.
It is preferable to carry out simultaneously at 0 ° C to 160 ° C.

In the method of manufacturing an integrated solar cell according to the present invention, the electrodes of the solar cell element are formed using indium or an alloy containing indium. Specifically, a conductive adhesive portion is formed on the surface of the lead wire or the surface of the electrode using indium or an alloy containing indium, and the lead wire is attached to the electrode using the conductive adhesive portion. Since the melting point of the conductive adhesive portion is lowered, the lead wire can be conductively bonded to the electrode at a low temperature. Therefore, the adhesion of the leader line and the adhesion of the thermoplastic film can be performed in parallel.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 2 shows an example of the overall configuration of an integrated single crystal silicon solar cell, for example, as an integrated solar cell according to the first embodiment of the present invention. . This integrated solar cell 10 is formed by integrating a plurality of (five in FIG. 2) single crystal silicon solar cell elements,
A plurality of solar cell elements 11 are arranged in one direction and are connected in series by a lead wire 12 made of copper, for example. In addition,
The solar cell elements 11 are not limited to the one-dimensional array as shown in FIG. 2 and may be two-dimensionally arrayed.

The solar cell element 11 is shown in more detail in FIG.
As described above, the semiconductor substrate 1 made of p-type single crystal silicon
3 has a semiconductor junction 14 formed near the surface thereof.
It Specifically, the surface of the p layer 14A of the semiconductor substrate 13
To which n (P) was added ⁺With layer 14B
In addition, phosphorus is further added corresponding to the surface electrode 15 described later.
N⁺⁺It has a layer 14C.

The surface electrode 1 is provided on the surface of the solar cell element 11.
5, a finger bar 15F for collecting current and a bus bar 15B where the finger bar 15F joins are formed. The finger bar 15F and the bus bar 15B are made of, for example, silver (Ag) paste. The surface of the solar cell element 11 excluding the finger bar 15F and the bus bar 15B is an oxide film (passivation) 17
And is covered with the antireflection film 18. Although not shown in FIGS. 2 and 3, the entire surface of the solar cell element 11 is covered with a thermoplastic film or the like made of EVA (ethylene vinyl acetate), for example, for surface protection. This thermoplastic film will be described later.

A back surface electrode 16 is formed on the back surface of the semiconductor substrate 13.
As an example, an aluminum (Al) film is formed on the entire surface. An adhesive film 19 made of silver paste is provided on the surface of the back electrode 16. Adhesive film 19
Is for facilitating attachment of other layers to the back electrode 16 made of aluminum, and is formed by screen printing, for example. The front surface electrode 15 including the bus bar 15B and the finger bar 15F and the back surface electrode 16 are
It corresponds to the "electrode" in the present invention.

FIG. 1 is an enlarged sectional view of the bus bar 15B in the width direction. As shown in FIGS. 1 and 3, on the surface of the lead wire 12 made of copper, a conductive adhesive portion 20A is formed in a planar shape so as to cover the entire surface of the lead wire 12. The lead wire 12 is bonded along the bus bar 15B using the conductive bonding portion 20A. The reason why the lead wire 12 is bonded along the bus bar 15B is to reduce the electric resistance of the bus bar 15B and prevent heat generation and voltage drop due to a large current.

The conductive adhesive portion 20A is made of an alloy containing indium and tin (Sn) or an alloy containing indium, gallium (Ga) and tin. The composition can be represented by, for example, the following formula (1).

[0019] _{(In 1-x -Ga x)} a - (Sn 1-y -M y) b (1) ( where, x ≦ 0 · 07, y ≦ 0.1, a + b = 1,0.
25 <a <0.95, M is at least one element selected from bismuth (Bi), zinc (Zn), nickel (Ni), silver (Ag), and antimony (Sb), and each unit is a weight. ratio)

Here, the reason for making the content (weight ratio) of gallium smaller than 0.07 is that when gallium is deposited in the indium gallium alloy, the melting point of gallium is 30.
This is because the segregated portion may melt out because of the temperature of ° C. Further, the reason why the content (weight ratio) of the element represented by M in the above formula (1) is made smaller than 0.1 is that the melting point of the alloy is not too high. The reason why the total content (weight ratio) of indium and gallium is made larger than 0.25 is to lower the melting point, and the reason for making it smaller than 0.95 is to lower the melting point (to 130 ° C. or lower). This is because it is not too much. In the present embodiment, conductive adhesive portion 20A is made of an alloy containing indium and tin.

In this integrated solar cell 10, the surface electrode 1
Part of the light emitted from the 5 side passes through the antireflection film 18 and the oxide film 17, enters the solar cell element 11, and is absorbed. Further, a part of the light transmitted through the solar cell element 11 is reflected by the back surface electrode 16, enters the solar cell element 11 again, and is absorbed. Light-absorbed n ⁺ layers 14B and p
In the layer 14A, electron-hole pairs are generated. electrons generated in the p layer 14A are attracted to the field n ⁺ layer 14B, further enters the n ⁺⁺ layer 14C, holes generated in the n ⁺ layer 14B enter the p layer 14A is pulled in an electric field. As a result, a current proportional to the amount of incident light is generated and taken out from the lead wire 12.

Next, with reference to FIGS. 4 to 6 and FIGS. 2 and 3 described above, the integrated solar cell 1 will be described.
The manufacturing method of 0 will be described. In the present embodiment, the conductive adhesive portion 20A is formed using indium or an alloy containing indium instead of conventional solder.

First, as shown in FIG. 4A, for example, a (100) p-type silicon substrate is prepared as a semiconductor substrate 13 for forming the solar cell element 11. Next, as shown in FIG. 4B, n ⁺⁺ diffusion is performed in a region corresponding to the surface electrode 15 of the semiconductor substrate 13 to form an n ⁺⁺ layer 14C, and then n ⁺ diffusion is performed. ^{The +} layer 14B is formed. As a result, the p layer 14A and the n ⁺ layer 14B or the n ⁺⁺ layer 14 are formed.
The semiconductor junction portion 14 is formed between the semiconductor junction portion 14 and C.

Next, the surface of the semiconductor substrate 13 is thermally oxidized to form an oxide film 17 for passivation, and further an antireflection film 18 is formed. The oxide film 17 and the antireflection film 18 are selectively removed to form a groove 31 matching the shape of the surface electrode 15, as shown in FIG.

Thereafter, as shown in FIG. 5B, the surface electrode 15 is formed by screen printing of silver paste, for example.
Form the finger bar 15F and the bus bar 15B,
Bake. On the back surface of the semiconductor substrate 13, an aluminum film is formed as the back surface electrode 16 by screen printing, for example. Subsequently, an adhesion film 19 made of a silver paste is formed on the surface of the back surface electrode 16 by screen printing, for example, and then baked.

On the other hand, as shown in FIG. 6A, on the surface of the lead wire 12 made of copper, an alloy containing indium and tin (the content of tin is, for example, 30% by weight) is used, and the conductivity is improved. The adhesive portion 20A is formed. In the case where the conductive adhesive portion 20A is formed in a planar shape so as to cover the entire surface of the lead wire 12 as in the present embodiment, indium, which is significantly more expensive than silver or the like, is used rather than alone. However, it is highly desirable to use an alloy containing indium.

Next, as shown in FIG. 6B, the lead wire 12 on which the conductive adhesive portion 20A made of an alloy containing indium and tin is formed is placed on the bus bar 15B, and further from above. The surface of the solar cell element 11 is covered with the thermoplastic film 30 by covering with the thermoplastic film 30, and the thermoplastic film 30 is heated to cover the solar cell element 1 with the solar cell element 1.
Adhere to 1. The heating temperature is, for example, 150 ° C to 1
Temperature in the range of 60 ° C, for example, 150 ° C in the present embodiment
And The conductive adhesive portion 20A made of an alloy containing indium and tin can be melted at a temperature slightly lower than the above range, for example, about 120 ° C. to 140 ° C., but is made of EVA, for example, at the temperature in the above range. This is because the thermoplastic film 30 is crosslinked. Therefore, by heating to a temperature in the above range, the lead wire 12
Is pressure-bonded to the bus bar 15B, and at the same time, the thermoplastic film 30 is cross-linked to make the solar cell element 11
Can be glued to the surface of.

The end portion 12A of the lead wire 12 is also adhered to the adhering film 19 of the adjacent solar cell element 11 using the conductive adhering portion 20A, and thereby electrically connected to the back surface electrode 16. . The adhesion of the lead wire 12 and the back electrode 16 can also be performed in parallel with the adhesion of the thermoplastic film 30. Thereby, a plurality of solar cell elements 11 are connected in series, and the integrated solar cell 10 of the present embodiment can be completed.

As described above, in the present embodiment, the conductive adhesive portion 20A is formed on the surface of the lead wire 12 by using an alloy containing indium.
Leader wire 1 at lower temperature than conventional solder made of lead-tin alloy
2 and the bus bar 15B or the back electrode 16 can be electrically conductively bonded. That is, the eutectic point of the conventional solder made of lead-tin alloy is 183 ° C, but the normal working temperature is about 230 ° C. On the other hand, the conductive adhesive portion 2
The melting point of 0 A has a eutectic point of about 120 ° C. when it is made of an alloy containing indium and tin as in this embodiment.
Therefore, the lead wire 12 and the bus bar 15B or the back electrode 16 can be electrically conductively bonded at a significantly lower working temperature and energy cost as compared with the conventional solder made of an alloy of lead and tin.

Further, according to the present embodiment, since the conductive adhesive portion 20A is made of an alloy containing indium and tin, its eutectic point is about 120.degree. The integrated solar cell 10 is usually installed outdoors, and the temperature inside the solar cell 10 rises to about 80 ° C. in the midsummer, but even in a completely closed car, the temperature is only about 100 ° C. at most. Therefore, the conductive adhesive portion 20A is not only a low melting point and good in workability, but also does not melt even in a high temperature such as a car in the midsummer and is safe.

Further, in the present embodiment, the lead wire 12 having the conductive adhesive portion 20A formed on the surface thereof is placed on the bus bar 15B, and the surface of the solar cell element 11 is covered with the thermoplastic film 30 to remove heat. Plastic film 30
Since the heating is carried out to the temperature at which the crosslinking is carried out, specifically, the temperature in the range of 150 ° C. to 160 ° C. It can be done in parallel and simplifies the manufacturing process.

[Second Embodiment] Next, the second embodiment of the present invention will be described.
The integrated solar cell according to the embodiment will be described.
FIG. 7 shows each solar cell element of the integrated solar cell according to the present embodiment, and FIG. 8 shows a cross section in the width direction of the bus bar of the solar cell element shown in FIG. 7. In the first embodiment, the conductive adhesive portion 20A is connected to the lead wire 12
The surface is formed so as to cover the entire surface of the. On the other hand, in the present embodiment, the conductive adhesive portion 20B is formed in a planar shape so as to cover the entire surfaces of the front surface electrode 15 and the back surface electrode 16, and the leader line 12 is formed on the conductive adhesive portion 20B. The embedded state is conductively adhered to the bus bar 15B. Except for this, the present embodiment is the same as the first embodiment. Therefore, the same components are given the same reference numerals,
Here, the detailed description is omitted.

Since the material of the conductive adhesive portion 20B is the same as that described in the first embodiment, detailed description thereof will be omitted here.

Next, a method of manufacturing the integrated solar cell according to this embodiment will be described. In the present embodiment, the conductive adhesive portion 20B is formed by using an alloy containing indium instead of indium alone, as in the first embodiment.

First, in the same manner as the steps of FIGS. 4 (A), (B) and FIGS. 5 (A), (B) described in the first embodiment, the semiconductor junction portion 14 is formed on the semiconductor substrate 13. A bus bar 15B and a finger bar 15F as the front surface electrode 15, a back surface electrode 16 and a film 19 for adhesion are formed respectively. Since the steps up to this point are the same as those in the first embodiment, detailed description thereof will be omitted.

Thereafter, the solar cell element 11 is dipped in an unillustrated dip bath heated to 150 ° C., for example, with an alloy containing indium and tin (tin content is 50 wt%). Thus, the conductive adhesive portion 20B made of an alloy containing indium and tin can be formed in a planar shape so as to cover the entire surfaces of the finger bar 15F, the bus bar 15B and the adhesive film 19.

After that, the solar cell element 11 is heated on, for example, a hot plate, and the lead wire 12 made of copper, for example, is bonded along the bus bar 15B covered with the conductive bonding portion 20B with a soldering iron. Thus, the solar cell element 11 is completed as shown in FIG. The lead wire 12 bonded along the bus bar 15B is embedded in the conductive bonding portion 20B.

Finally, the end 12A of the lead wire 12 adhered along the bus bar 15B is connected to the adjacent solar cell element 1.
It is electrically connected to the back electrode 16 of No. 1 so that the plurality of solar cell elements 11 are connected in series. In addition, leader line 12
The end portion 12A of the conductive adhesive portion 20 on the adhesive film 19 is
It is in a state of being embedded in B. Thereafter, a thermoplastic film 30 (see FIG. 1) made of EVA, for example, is further adhered to the surface of each solar cell element 11 to protect the surface electrode 15.

As described above, in the present embodiment, the conductive adhesive portion 20B is formed on the surface of the surface electrode 15 and the adhesive film 19 using an alloy containing indium. The lead wire 12 and the bus bar 15B or the back electrode 16 can be electrically conductively bonded to each other at a lower working temperature and lower energy cost than the conventional solder made of a lead-tin alloy.

[Third Embodiment] Next, the third embodiment of the present invention will be described.
The integrated solar cell according to the embodiment will be described.
FIG. 9 shows a cross section in the longitudinal direction of the bus bar of each solar cell element of the integrated solar cell according to the present embodiment. First
In the embodiment, the conductive adhesive portion 20A is formed in a planar shape so as to cover the entire surface of the lead wire 12. On the other hand, in the present embodiment, as shown in FIG. 9, the conductive adhesive portion 20C is formed on the coat layer 12C formed on the surface of the lead wire 12 in the form of dots at intervals. I have to. Except for this, the present embodiment is the same as the first embodiment. Therefore, the same components are designated by the same reference numerals, and detailed description thereof will be omitted here.

Since the material of the conductive adhesive portion 20C is the same as that described in the first embodiment, its detailed description is omitted here.

Next, a method for manufacturing the integrated solar cell according to this embodiment will be described. In the present embodiment, unlike the first and second embodiments, the conductive adhesive portion 20C is formed by using indium alone.

First, in the same manner as the steps of FIGS. 4A and 4B and FIGS. 5A and 5B described in the first embodiment, the semiconductor junction portion 14 and the semiconductor junction portion 14 are formed on the semiconductor substrate 13. A bus bar 15B and a finger bar 15F as the front surface electrode 15, a back surface electrode 16 and a film 19 for adhesion are formed respectively. Since the steps up to this point are the same as those in the first embodiment, detailed description thereof will be omitted.

On the other hand, as shown in FIG. 10A, a coat layer 12C made of tin or an alloy containing tin is formed on the surface of the lead wire 12 made of copper. Examples of the material of the coat layer 12C include simple tin, various lead-free solders, and alloys containing at least one of silver and bismuth in addition to tin.

Next, as shown in FIG. 10 (B), about 1 part of the surface of the coat layer 12C of the lead wire 12 is applied.
The indium thin pieces 21C are placed at intervals of cm, for example, 160
By heating to 0 ° C., tin contained in the coating layer 12C and the indium thin piece 21B are alloyed. As a result, FIG.
As shown in (C), a conductive adhesive portion 20C (eutectic point 120 ° C.) made of an alloy of indium and tin is provided on the surface of the coat layer 12C of the lead wire 12 in a dotted pattern at intervals. Can be formed. As described above, in the present embodiment, since the conductive adhesive portion 20C is formed in a dot shape, the area of the conductive adhesive portion 20C becomes small and the amount of the indium thin piece 21C used becomes very small.

The conductive adhesive portion 20C is connected to the lead wire 12
Need not be provided over the entire length direction of the solar cell element 1 and the portion bonded to the bus bar 15B and the adjacent solar cell element 1
It may be provided in a portion to be bonded to the back surface electrode 16.

Next, as shown in FIG. 11, the lead wire 12 is placed on the bus bar 15B with the conductive adhesive portion 20C facing the bus bar 15B, and the surface of the solar cell element 11 is covered with the thermoplastic film 30. Cover and heat to a temperature at which the thermoplastic film 30 crosslinks, for example 150 ° C. Thereby, as shown in FIG. 8, the lead wire 12 is pressure-bonded to the bus bar 15B and the thermoplastic film 30 is bonded to the solar cell element 11.

The end portion 12A of the lead wire 12 uses the conductive adhesive portion 20C to form an adjacent solar cell element 11 (not shown).
Is electrically connected to the back surface electrode 16 of. Thereby, the plurality of solar cell elements 11 are connected in series, and the integrated solar cell of the present embodiment can be completed.

As described above, in the present embodiment, the indium thin piece 21C is used to form the conductive adhesive portion 20C on the surface of the coat layer 12C of the lead wire 12, so that the first adhesive layer is formed. As in the embodiment, the conventional lead-
Conductive bonding between the lead wire 12 and the bus bar 15B or the back electrode 16 can be performed due to a lower working temperature and lower energy cost than the solder made of tin alloy.

Further, in the present embodiment, since the conductive adhesive portions 20C are formed in the shape of dots at intervals, even if expensive indium is used alone, the amount of its use is made minute. be able to.

Further, also in this embodiment, as in the first embodiment, the lead wire 12 having the conductive adhesive portion 20C formed on its surface is placed on the bus bar 15B, and further,
Since the surface of the solar cell element 11 is covered with the thermoplastic film 30 and heated to a temperature at which the thermoplastic film 30 is crosslinked, specifically, a temperature in the range of 150 ° C. to 160 ° C., the bus bar 15B of the lead wire 12 is provided. To the solar cell element 11 and the thermoplastic film 30 can be performed in parallel, and the manufacturing process is simplified.

[Fourth Embodiment] Next, the fourth embodiment of the present invention will be described.
The integrated solar cell according to the embodiment will be described.
The integrated solar cell of this embodiment is different from the third embodiment only in the manufacturing method. That is, in the third embodiment, the conductive adhesive portion 20C is formed on the coat layer 12C formed on the surface of the lead wire 12 in a dot shape at intervals. On the other hand, in the present embodiment, the conductive adhesive portion 20C is provided on the surface of the bus bar 15B,
It is formed in dots at intervals. Except for this, the present embodiment is the same as the third embodiment. Therefore, the same components are designated by the same reference numerals, and detailed description thereof will be omitted here.

Next, a method for manufacturing the integrated solar cell according to this embodiment will be described. First, FIGS. 4A, 4B and 5 described in the first embodiment are described.
Similar to the steps (A) and (B), the semiconductor substrate 13
The semiconductor junction 14 and the bus bar 1 as the surface electrode 15
5B, the finger bar 15F, the back electrode 16 and the adhesive film 19 are formed respectively. Since the steps up to this point are the same as those in the first embodiment, detailed description thereof will be omitted.

On the other hand, as shown in FIG. 12 (A), on the surface of the bus bar 15B, at intervals of about 1 cm,
The indium thin piece 21C is placed and heated to, for example, 160 ° C. As a result, the indium thin piece 21C becomes the bus bar 1
The silver contained in 5B is melted, and as shown in FIG. 12B, the conductive adhesive portion 20C is formed on the surface of the bus bar 15B.
(Eutectic point 141 ° C.) can be formed in dots at intervals. As described above, in the present embodiment, since the conductive adhesive portion 20C is formed in a dot shape, the area of the conductive adhesive portion 20C is small and the indium thin piece 21C can be used as in the third embodiment. Is.

Next, the temperature is lowered to 150 ° C., and as shown in FIG. 13, the tin coat layer 1 made of, for example, tin is formed on the surface.
The lead wire 12 having 2C formed thereon is placed on the bus bar 15B having the conductive adhesive portion 20C formed thereon. Further, the surface of the solar cell element 11 is covered with the thermoplastic film 30.
Since the solar cell element 11 is kept at the temperature at which the thermoplastic film 30 is crosslinked, for example, 150 ° C., a molten alloy containing silver, indium and tin is formed in the conductive adhesive portion 20C, while The plastic film 30 is crosslinked. By cooling this, as shown in FIG. 14, the lead wire 12 is bonded to the bus bar 15B by the conductive bonding portion 20C, and the thermoplastic film 30 is formed.
Are bonded to the solar cell element 11.

Similarly, the end portion 12A of the lead wire 12 is electrically connected to the back surface electrode 16 of the adjacent solar cell element 11 by using the tin coat layer 12C. Thereby, the plurality of solar cell elements 11 are connected in series, and the integrated solar cell of the present embodiment can be completed.

As described above, in the present embodiment, indium is used for the surface of the bus bar 15B,
Since the conductive adhesive portion 20C is formed, the lead wire 12 and the bus bar 15B or the back surface can be formed at a lower working temperature and energy cost as compared with the conventional lead-tin alloy solder, as in the first embodiment. Conductive adhesion with the electrode 16 can be performed.

Further, in the present embodiment, the conductive adhesive portions 20C are formed in the shape of dots at intervals. Therefore, even if expensive indium is used alone, the amount used is very small. be able to.

Further, also in the present embodiment, as in the second and third embodiments, the lead wire 12 is placed on the bus bar 15B on which the conductive adhesive portion 20C is formed, and the solar cell element is further provided. The surface of 11 is a thermoplastic film 30
Since it was heated by heating to a temperature at which the thermoplastic film 30 is crosslinked, specifically, a temperature in the range of 150 ° C. to 160 ° C., the adhesion of the leader wire 12 to the bus bar 15B and the solar cell of the thermoplastic film 30. Bonding to the element 11 can be performed in parallel, which simplifies the manufacturing process.

[Fifth Embodiment] Next, the fifth embodiment of the present invention will be described.
The integrated solar cell according to the embodiment will be described.
The integrated solar cell of this embodiment is different from that of the third embodiment in the material of the conductive adhesive portion. That is, the third
In the embodiment, the conductive adhesive portion 20C is formed by using the indium thin piece 21C made of metal indium. On the other hand, in the present embodiment, the conductive adhesive portion 20D is formed using an alloy containing indium, specifically, an alloy containing indium and gallium. Except for this, the present embodiment is the same as the third embodiment.
Therefore, the same components are designated by the same reference numerals, and detailed description thereof will be omitted here.

Since the material of the conductive adhesive portion 20D is the same as that described in the first embodiment,
Here, the detailed description is omitted.

Next, a method of manufacturing the integrated solar cell according to this embodiment will be described. In the present embodiment, the conductive adhesive portion 20D is formed using an alloy containing indium. First, in the same manner as the steps of FIGS. 4A and 4B and FIGS. 5A and 5B described in the first embodiment, the semiconductor junction portion 14 is formed on the semiconductor substrate 13.
A bus bar 15B and a finger bar 15F as the front surface electrode 15, a back surface electrode 16 and a film 19 for adhesion are formed respectively. Since the steps up to this point are the same as those in the first embodiment, detailed description thereof will be omitted.

On the other hand, as shown in FIG. 10A of the third embodiment, a coat layer 12C is formed on the surface of the lead wire 12 made of copper. Next, as shown in FIG. 15 (A), an alloy containing indium and gallium is partially dissolved on the surface of the coat layer 12C of the lead wire 12 at intervals of about 1 cm, and the conductive adhesive portion 20D is formed into dots. Can be formed. In the present embodiment, since the conductive adhesive portion 20D is formed in a dot shape with an interval, the area of the conductive adhesive portion 20D is small as in the third and fourth embodiments. Therefore, indium may be partially dissolved instead of the alloy containing indium and gallium.

The conductive adhesive portion 20D is connected to the lead wire 12
Need not be provided over the entire length direction of the solar cell element 1 and the portion bonded to the bus bar 15B and the adjacent solar cell element 1
It may be provided in a portion to be bonded to the back surface electrode 16.

Next, as shown in FIG. 15B, the conductive adhesive portion 20D is made to face the bus bar 15B, and the lead wire 1 is provided.
2 is placed on the bus bar 15B, and the solar cell element 1
The surface of No. 1 is covered with the thermoplastic film 30, and the temperature at which the thermoplastic film 30 is crosslinked, that is, 150 ° C. to 16 ° C.
Heat to a temperature in the range of 0 ° C, for example 150 ° C. As a result, as shown in FIG.
The thermoplastic film 30 is bonded to the solar cell element 11 while being pressure-bonded to 5B.

The end portion 12A of the lead wire 12 is electrically connected to the back surface electrode 16 of the adjacent solar cell element 11 by using the conductive adhesive portion 20D. Thereby, the plurality of solar cell elements 11 are connected in series, and the integrated solar cell of the present embodiment can be completed.

As described above, in the present embodiment, the conductive adhesive portion 20D is formed on the surface of the coat layer 12D of the lead wire 12 by using indium or an alloy containing indium. Similar to the first embodiment, the lead wire 12 and the bus bar 15B or the back electrode 16 can be electrically conductively bonded at a lower working temperature and lower energy cost than the conventional solder made of a lead-tin alloy.

Further, in the present embodiment, by adding gallium to indium, the melting point is further lowered than that of indium, and the working temperature for bonding can be lowered.

Further, in the present embodiment, since the conductive adhesive portions 20D are formed in the shape of dots at intervals, the amount of expensive indium used can be made minute.

Further, also in the present embodiment, as in the first embodiment, the lead wire 12 having the conductive adhesive portion 20D formed on its surface is placed on the bus bar 15B, and further,
Since the surface of the solar cell element 11 is covered with the thermoplastic film 30 and heated to a temperature at which the thermoplastic film 30 is crosslinked, specifically, a temperature in the range of 150 ° C. to 160 ° C., the bus bar 15B of the lead wire 12 is provided. To the solar cell element 11 and the thermoplastic film 30 can be performed in parallel, and the manufacturing process is simplified.

The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above embodiment, the case of an integrated type single crystal silicon solar cell in which single crystal silicon solar cell elements formed on a single crystal silicon substrate are integrated has been described. It can also be applied to batteries. Further, it can be applied to general solar cells such as amorphous silicon formed on a thin film formed on a substrate other than silicon, silicon microcrystal, CIS, and dye-sensitized solar cell.

Further, in the above embodiment, the finger bar 15F and the bus bar 15B as the cathode are formed on the front side of the semiconductor substrate 13, and the back electrode 16 as the anode is formed on the back side, but the cathode and the anode are the same. The present invention can be applied to a solar cell having a structure formed on the surface.

Further, in the above embodiment, the surface electrode 1
5 is composed of a bus bar 15B and a plurality of finger bars 15F that merge with the bus bar 15B.
Although the example in which it is formed on the entire back surface of No. 3 has been described, the back electrode 16 may also have a configuration having a bus bar and a finger bar that joins with the bus bar, like the front electrode 15.

Although EVA is used as the material of the thermoplastic film 30 in the above embodiment, other transparent and highly workable materials may be used. As an example, it is softened at 100 ° C. to a hundred and several tens of ° C. to show adhesion.
Fluorine-based thermoplastic resin with excellent light resistance, such as THV
(Product name of Sumitomo 3M Ltd.) can be used.

[0075]

As described above, according to the method of manufacturing an integrated solar cell according to claim 1, the electrodes of the solar cell element are formed by using indium or an alloy containing indium. Conductive adhesion is possible at a lower temperature than the solder made of tin-lead alloy. More specifically, according to the method for manufacturing an integrated solar cell according to any one of claims 2 to 8, indium or an alloy containing indium is used on the surface of the lead wire or the surface of the electrode. Since the conductive adhesive portion is formed, the lead wire can be conductively adhered to the electrode at low temperature by using the conductive adhesive portion. Also, even though the conductive adhesive part has a low melting point, its melting point is not so low that it melts under high temperature such as in a car in midsummer, so it is applied to an integrated solar cell and safely used. be able to.

In particular, according to the method for manufacturing an integrated solar cell according to claim 3 or 4, the step of adhering the leader line using the conductive adhesive portion is performed at a temperature at which the thermoplastic film is crosslinked, specifically Since it is performed at a temperature in the range of 150 ° C. to 160 ° C., the adhesion of the leader wire to the electrode and the adhesion of the thermoplastic film to the solar cell element can be performed in parallel, which simplifies the manufacturing process. Be converted.

Further, in particular, according to the method of manufacturing an integrated solar cell of claim 7, the conductive adhesive portions are formed on the surface of the lead wire or the surface of the electrode in a dot shape at intervals. Therefore, the amount of expensive indium used can be reduced to a very small amount.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing a bus bar of each solar cell element of an integrated solar cell according to a first embodiment of the present invention in an enlarged manner.

FIG. 2 is a perspective view for explaining an example of the overall configuration of the integrated solar cell according to the first embodiment of the present invention.

3 is an enlarged perspective view of the solar cell element shown in FIG.

FIG. 4 is a perspective view showing an example of a manufacturing process of the integrated solar cell shown in FIG.

FIG. 5 is a perspective view illustrating a manufacturing process following FIG.

FIG. 6 is a perspective view illustrating a manufacturing process following FIG.

FIG. 7 is a perspective view showing a schematic configuration of a solar cell element of an integrated solar cell according to a second embodiment of the present invention.

8 is a cross-sectional view in a width direction in which a bus bar of the solar cell element shown in FIG. 7 is enlarged and shown.

FIG. 9 is a longitudinal sectional view of a bus bar of a solar cell element of an integrated solar cell according to a third embodiment of the present invention.

FIG. 10 is a cross-sectional view showing an example of a manufacturing process of the integrated solar cell shown in FIG. 9 in process order.

FIG. 11 is a perspective view illustrating a manufacturing process following FIG. 10.

FIG. 12 is a cross-sectional view showing an example of a manufacturing process of the integrated solar cell according to the fourth embodiment of the present invention in the order of processes.

FIG. 13 is a cross-sectional view showing a manufacturing process that follows FIG.

FIG. 14 is a cross-sectional view showing a manufacturing process following FIG.

FIG. 15 is a cross-sectional view showing an example of a manufacturing process of an integrated solar cell according to a fifth embodiment of the present invention in the order of processes.

FIG. 16 is a cross-sectional view showing a manufacturing process following FIG. 15.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Integrated solar cell, 11 ... Solar cell element, 12 ... Leader wire, 13 ... Semiconductor substrate, 14 ... Semiconductor junction part, 14A
... p layer, 14B ... n ⁺ layer, 14C ... n ⁺⁺ layer, 15 ... surface electrode, 15A ... bus bar, 15B ... finger bar, 1
6 ... Back electrode, 17 ... Oxide film (passivation), 1
8 ... Antireflection film, 19 ... Adhesive film, 20A, 20B,
20C, 20D ... Conductive adhesive portion, 21C ... Indium flakes

Claims (8)

[Claims] 1. A method for manufacturing an integrated solar cell in which a plurality of solar cell elements each including a semiconductor junction portion and an electrode formed on a semiconductor substrate are connected in series by a lead wire, wherein the electrode is made of indium (In ) Or an alloy containing indium is used to form the integrated solar cell. 2. A step of forming a semiconductor junction portion on each of the plurality of semiconductor substrates, and a plurality of suns each including an electrode on each surface of the plurality of semiconductor substrates to include the semiconductor junction portion and the electrode. A step of forming a battery element, and a step of forming a conductive adhesive portion using indium or an alloy containing indium on the surface of the lead wire or the surface of the electrode for connecting the plurality of solar cell elements in series, A method for manufacturing an integrated solar cell, comprising: bonding the lead wire to the electrode using the conductive adhesive portion; and connecting the plurality of solar cell elements in series with the lead wire. 3. The leader line is adhered by using the conductive adhesive portion at a temperature at which the thermoplastic films for protecting the surfaces of the plurality of solar cell elements are cross-linked. 3. The method for manufacturing an integrated solar cell according to claim 2, wherein the bonding of [1] and the bonding of the thermoplastic film are performed in parallel. 4. The method for manufacturing an integrated solar cell according to claim 3, wherein the step of adhering the lead wire using the conductive adhesive portion is performed at a temperature in the range of 150 ° C. to 160 ° C. . 5. The integrated device according to claim 2, wherein the conductive adhesive portion is made of an alloy containing indium and tin (Sn) or an alloy containing indium, gallium (Ga) and tin. Type solar cell manufacturing method. 6. The conductive adhesive portion is formed of (In _1-x −Ga _x ) _a − (Sn _1-y −M _y ) _b (where x ≦ 0.07, y ≦ 0.1, a + b = 1). , 0.
25 <a <0.95, M is indium represented by bismuth (Bi), zinc (Zn), nickel (Ni), silver (Ag), and antimony (Sb). The method for manufacturing an integrated solar cell according to claim 2, wherein the integrated solar cell is made of an alloy containing. 7. The method for manufacturing an integrated solar cell according to claim 2, wherein the conductive adhesive portion is formed in a dot shape at intervals on the surface of the lead wire or the surface of the electrode. . 8. The method for manufacturing an integrated solar cell according to claim 2, wherein the conductive adhesive portion is formed in a planar shape so as to cover the entire surface of the lead wire or the entire surface of the electrode. .