JP2000332269A - Solar battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish reliable connections between leads and back side electrodes of a plurality of solar batteries through soldering, when the plurality of solar batteries are connected to one another by the leads, and to prevent damages during the laminating step of adhering the solar batteries to a glass substrate or the like. SOLUTION: A solar battery 1 comprises a semiconductor substrate having a P-N junction, electrodes on the light-receiving surface side of the semiconductor substrate, and a back side electrode pattern 8 formed on the back of the semiconductor substrate. The pattern 8 is formed of three divided electrodes 10, 11 and 12 by printing and baking a silver paste. The electrodes 10, 11 and 12 are divided perpendicularly with respect to a direction in which leads are connected. Therefore, when the substrate is drawn up from a solder vessel during its dipping into the solder vessel, the tip of each of the three electrodes 10, 11 and 12 which points in the direction opposite to the substrate raising direction, serves as a solder accumulated layer forming portion, thereby allowing the solder to accumulate thereon in a proper amount. C-shaped or curved slender wires make connections between the electrodes 10 and 11 and between the electrodes 11 and 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell electrode and a method of manufacturing the same, and more particularly, to a back electrode capable of ensuring connection with a lead when a plurality of solar cells are connected by a lead. And a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 6 is a sectional view of a conventional general solar cell 1 in which active impurities are diffused shallowly into the surface of a P-type Si (silicon) substrate 2 to form an N + diffusion layer 3 and a PN near the surface. Si to form a junction and prevent sunlight reflection on it
An anti-reflection film 4 made of O ₂ , TiO ₂ , SiN or the like is formed. Electrode portions 5 and 8 for connecting a plurality of solar cell elements are formed on both front and back surfaces of the solar cell 1 by using a screen printing method, a vapor deposition method, a sputtering method, or the like. Among them, the back electrode 8 for connecting the wiring is, as shown in FIGS.
In order to easily connect the wiring such as the lead wire 22, it has a rectangular shape that is long in the normal connection direction B. As shown in FIG.
Is connected to the light receiving surface of the adjacent solar cell 1 '. At this time, since the lead wire 22 is connected to the light receiving surface (front surface) electrode 5 and the back surface electrode 8 by soldering, the solder layers 6 and 9 are formed in advance on both the front and back electrodes of each solar cell 1, 1 '. Keep it. Such solder layers 6, 9 are applied to the front and back electrodes 5,
As shown in FIG. 9, the solar cell 1 on which the front and back electrodes 5 and 8 are formed is immersed in the solder layer 21 by a solder dipping method, and is pulled up, as shown in FIG.

[0003]

However, in the conventional solar cell element, the thickness of the solder layer formed on the back side electrode is small, the solder layer is not formed well on the electrode, or the solder layer is partially formed. In some cases, a layer was not formed, and the adhesion between the lead wire and the back electrode portion when connecting a plurality of solar cell elements was insufficient. Further, the amount of the solder pool may be too large and the thickness may be too large, and there is a problem that the solar cell is damaged in a laminating step of bonding the solar cell element to a glass substrate or the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and is intended to provide a solar cell having a back electrode capable of improving a connection between a back electrode portion and a wiring connecting the solar cell. With the goal. Another object of the present invention is to provide a solar cell that is not damaged in a laminating step of a solar cell and a glass substrate or the like.

[0005]

In order to achieve the above-mentioned object, a first aspect of the present invention is to provide a semiconductor substrate having a PN junction and a back surface for connecting a wiring formed on the back side of the semiconductor substrate. And a back electrode is divided into a plurality of parts to form a solder pool. The invention of Claim 2 is Claim 1
In the solar cell described above, the back electrode is divided parallel or perpendicular to a wiring connection direction. According to a third aspect of the present invention, in the solar cell according to the first aspect, the back electrode is divided obliquely with respect to a wiring connection direction.

According to a fourth aspect of the present invention, in the solar cell according to any one of the first to third aspects, the back electrode has a polygonal shape such as a rectangle or a square having an arbitrary size, a circle or an ellipse or the like. It is characterized by being formed by a shape. According to a fifth aspect of the present invention, in the solar cell according to any one of the first to fourth aspects, a gap between the divided portions of the back electrode is 0.01 mm or more. According to a sixth aspect of the present invention, in the solar cell according to any one of the first to fifth aspects, the divided portion of the back electrode is connected by a thin wire. Claim 7
According to the invention of the sixth aspect, in the solar cell according to the sixth aspect, the thin line has a U shape or a curved shape. The invention according to claim 8 is the solar cell according to claim 6 or 7, wherein the fine line has a width of 0.01 mm or more. The invention according to claim 9 includes a semiconductor substrate having a PN junction, a light receiving surface electrode of the semiconductor substrate, and a back surface electrode formed on the back surface side of the semiconductor substrate, wherein the back surface electrode forms a solder pool. In a manufacturing method of solder-dipping a plurality of divided solar cells, the tip of the divided back electrode is directed downward or obliquely downward, and the solar cell is pulled up from the solder layer. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. In the following drawings and description, the same components as those of the conventional example are denoted by the same reference numerals, and the description may be omitted. FIG. 1 is a diagram for explaining one embodiment of the present invention, and is a rear view of a solar cell 1. The cross-sectional view of the solar cell 1 shown in FIG. 1 is the same as FIG. 6 shown in the conventional example, and will be described with reference to FIG. 2 is P type S
i (silicon) substrate, 3 is an N + diffusion layer formed by diffusing active impurities, and 4 is SiO to prevent reflection of sunlight.
₂ , an anti-reflection film made of TiO ₂ , SiN, etc., 5 is a negative light receiving surface electrode made of silver paste for receiving sunlight, 7 is a positive electrode made of Al (aluminum) paste, and 8 is a wiring connection. Is formed by printing and baking a silver paste on the back electrode for the purpose. Back electrode 8 is divided electrode 1
It is composed of 0, 11, and 12. Reference numerals 6 and 9 denote solder layers required for reducing the series resistance and connecting a plurality of solar cell elements 1.

FIG. 2 is a diagram showing a divided electrode pattern showing an embodiment of the back electrode 8 in an enlarged manner. This electrode pattern is formed by three divided electrodes 10, 11, and 12 which are perpendicular to the connection direction of the lead wires.

FIG. 5 is a view showing a solder dipping step for forming a solder layer on the back surface electrode 8. As shown in FIG. 5, at the time of lifting from the solder layer 21 at the time of solder dipping, the tip portions 13, 14, and 15 in the direction opposite to the lifting direction A become solder pool forming portions, and the solder is stored. Back electrode 8
In the case of the conventional example in which is not divided, the solder pool forming portions 13, 14, and 15 that can be bonded to the lead wire 22 can be formed only in one place, and the other portions are thin solder, so that the bonding with the lead wire 22 and the like cannot be performed. Although it becomes unstable, according to the present embodiment, since there are three portions where the solder pool is formed, the solder pool can be bonded to the lead wire 22 at many points, and sufficient bonding strength can be obtained.

Further, as shown in FIG. 2, the leading ends 13, 14, 15 in the direction opposite to the pulling direction A of the divided electrode 8 are
By making the tip having a thinner shape as the solder pool forming portion, the amount of the pooled solder can be controlled to an appropriate amount without changing the pulling speed from the solder layer 21. When the tip is thickened, the amount of solder pool increases, and the solar cell 1 may be damaged in a laminating step of bonding the solar cell 1 to a glass substrate or the like. In this embodiment, the tip of the electrode is thinned in a triangular shape in order to reduce the portion where the solder pool is formed. It accumulates in the accumulation forming part. In this embodiment, the divided electrode portion is divided into three, but may be divided into two or four or more.
What is necessary is just to set the division number suitable for the characteristic of the lead wire 22.

FIG. 3 shows an example of another electrode pattern of the back surface electrode 8. As shown in FIG. 3A, the back surface electrode 8 has divided electrodes 10 and 11 parallel to the connection direction of the lead wires. The above-described effect can be obtained even if the image is divided into two. FIG. 3 (B)
As shown in FIG.
Is divided obliquely to the connection direction of the lead wires, in addition to the above-described effects, the connection points are formed obliquely to the connection direction of the lead wires, so that there is an effect that the bonding is further stabilized. . FIG. 4 shows the split electrodes 10, 11,
12 shows an example of the shape, and the shape of the divided electrode 8 may be, for example, a polygon as shown in FIG. 4, a circle, an ellipse, or a combination thereof. By selecting the shapes of the tips 13, 14, and 15, the amount of accumulated solder can be controlled to an appropriate amount. The split electrodes 10, 11, 12
The distance between them was 2 mm in the embodiment of FIG. If the distance between the divided electrodes is shortened, the divided electrodes 10 and 11 or the divided electrodes 11 and 12 may be connected by solder, and a solder pool may not be formed. The distance between the divided electrodes must be at least 0.01 mm. When the back side split electrodes 10, 11, and 12 are electrically connected by the thin wires 16 and 17 as shown in FIG. 2, when the plurality of solar cell elements are connected by the lead wire 22, the split in FIG. Electrodes 10, 1
If any one of the wires 1 and 12 cannot be connected to the lead wire, by providing the thin wires 16 and 17, electrical isolation can be avoided.

As shown in FIG. 2, it is more preferable that the fine wires 16, 17 do not connect the divided electrodes 10, 11, 12 at the shortest distance but have a U-shaped or curved shape. When a thin line is formed in a straight line directly below the divided electrodes 10, 11, and 12 in FIG. 2, the solder from the upper electrode flows out to the lower electrode portion by pulling up from the solder layer at the time of solder dipping, and the lowermost electrode is formed. The solder pool can be formed only in the portion. Further, when the width is 0.01 mm or more, the electric resistance is reduced, and even if any of the divided electrodes cannot be connected to the lead wire, the increase in the resistance can be suppressed.

Next, a method of solder dip will be described. As shown in FIG. 2, on the silicon substrate 2, pentagonal backside divided electrodes 10, 11, and 12 each having a narrowed end and divided at right angles to the connection direction of the wiring are printed by a screen printing method. The silver paste is fired at a temperature of about ° C. Next, the solar cell 1 is immersed in a water-soluble flux or the like, dried at a temperature of about 150 ° C.,
It is immersed in the solder layer 21. The temperature of the solder layer at this time is around 200 ° C.

As shown in FIG. 5, the solar cell 1 immersed in the solder layer 21 is pulled up at a speed of about 10 cm / min with the divided electrode tips 13, 14, 15 downward. At this time, as shown in FIG. 3, excess solder flows from the upper part of the electrode in the direction of gravity opposite to the pulling direction. However, at the lower part of the split electrode, there is no way for the solder to flow down and the solder collects. Therefore, when the back electrode 8 is divided into a plurality of parts, the solder pool is formed in a direction opposite to the pulling-up direction from the solder layer 21 by the number of the divided parts, as shown in FIG.
14, 15 can be formed. At this time, the divided electrode tips 13, 14, 15 are lifted downward, but it is not always necessary to make the divided electrode tips directly downward, and the divided electrode tips are pulled obliquely downward to control the position and amount of the solder pool. can do.

Although the present embodiment has been described with reference to the figures of a square silicon substrate, the shape is not limited to this. For example, the silicon substrate may have any shape such as a round shape, a sector shape, a square shape with four missing corners, and the like. Is not limited to silicon.
Substrates used for solar cells, such as a compound semiconductor substrate such as s, may be used.

[0016]

As described above, according to the present invention, a plurality of solder pools can be formed by dividing the back electrode of the solar cell into a plurality of parts, and the lead wires can be connected with sufficient strength. it can. In addition, the amount of solder can be controlled to an appropriate amount by selecting the shape of the divided electrode tip. That is, if the tip of the divided electrode is made thinner, the solder pool can be reduced. By forming the solder pool in this way, it is possible to improve the connection with the wiring such as the lead wire connecting the solar cells. Further, it is possible to prevent the solar cell from being damaged during the step of laminating the solar cell on the glass substrate. Therefore, the connection between the solar cell element and the lead wire can be sufficiently ensured, and a highly reliable solar cell module can be manufactured.

[Brief description of the drawings]

FIG. 1 is a back view of a solar cell showing one embodiment of the present invention.

FIG. 2 is a divided electrode pattern showing a back electrode according to an embodiment of the present invention in an enlarged manner.

FIG. 3 is a backside divided electrode pattern showing another embodiment of the present invention.

FIG. 4 is a backside divided electrode pattern showing another embodiment of the present invention.

FIG. 5 is a schematic view showing a solder dip process showing one embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional solar cell.

FIG. 7 is a back view of a conventional solar cell.

FIG. 8 is a back view showing a state in which a plurality of conventional solar cells are connected by a lead wire to the back surface of the solar cell and a lighting surface of an adjacent solar cell.

FIG. 9 is a schematic view showing a conventional solder dip process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solar cell, 2 ... P-type silicon substrate, 3 ... N + diffusion layer, 4 ... Antireflection film, 5 ... Light receiving surface side electrode, 6, 9, 21
... Solder layer, 7 ... Back side Al electrode, 8 ... Back side silver electrode,
10, 11, 12: divided electrode, 13, 14, 15: solder pool forming portion, 16, 17: fine wire for electrically connecting between divided electrodes, 22: lead wire, A: pulling direction, B
… Lead wire connection direction.

Claims (9)

[Claims] 1. A solar cell comprising a semiconductor substrate having a PN junction and a back electrode for connecting wiring formed on the back side of the semiconductor substrate, wherein the back electrode is divided into a plurality of parts and solder pools are formed. A solar cell, characterized in that is formed. 2. The solar cell according to claim 1, wherein the back electrode is divided in parallel or perpendicular to a connection direction of a wiring. 3. The solar cell according to claim 1, wherein the back electrode is divided obliquely with respect to a wiring connection direction. 4. The back electrode is formed in a polygonal shape such as a rectangle or a square having an arbitrary size, a shape such as a circle or an ellipse, and the like.
The solar cell according to any one of the above. 5. The gap between the divided portions of the back electrode is 0.01 mm or more.
A solar cell according to any one of claims 1 to 4. 6. The solar cell according to claim 1, wherein the divided portions of the back electrode are connected by a thin wire. 7. The solar cell according to claim 6, wherein the thin line has a U shape or a curved shape. 8. The solar cell according to claim 6, wherein the thin line has a width of 0.01 mm or more. 9. A semiconductor substrate having a PN junction, a light receiving surface electrode of the semiconductor substrate, and a back surface electrode formed on a back surface side of the semiconductor substrate, wherein the back surface electrode forms a solder pool. In the manufacturing method of soldering a solar cell that has been divided into a plurality, the tip of the divided back electrode is directed downward or obliquely downward,
A method for manufacturing a solar cell in which the solar cell is pulled up from the solder layer.