JP2000261012A - Solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase adherence strength between an external electrode and a current collecting electrode so as to prevent the exfoliation of the external electrode, by increasing the area on which a fillet of a soldering layer is formed. SOLUTION: A current collecting electrode 5 is divided into four unit current collecting electrodes 5', and all of the unit current collecting electrodes 5' are electrically connected to an external electrode 7. The bottoms of thin wires 4 are electrically connected to an impurity diffused layer 2. Furthermore, a fillet 9 on solder 8 is formed, so as to cover the upper surface of a current collecting electrode 5 and the side of the external electrode 7. The larger the fillet 9 is, the larger the adherence strength between the external electrode 7 and the current collecting electrode 5 becomes. Since the current collecting electrode 5 is divided into four, a soldering layer 8 covers the bottom surface of the external electrode 7 at the ends of the unit current collecting electrodes 5'. The soldering layer 8 further covers the side walls of the unit current collecting electrodes 5' and the back of the external electrode 7 to form the fillet 9. Therefore, it is possible to increase the connecting strength between the external electrode and the current collecting electrode to prevent exfoliation of the external electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solar cell structure, and more particularly, to an electrode structure formed on a light receiving surface.

[0002]

2. Description of the Related Art FIG. 11 is a perspective view showing a structure of a general solar cell widely used in, for example, a residential photovoltaic power system manufactured by Sharp Corporation, and FIG.
FIG. 13 is a cross-sectional view taken along the line XII-XII. In the drawing, 1 is a semiconductor substrate made of p-type silicon, 2 is an n-type impurity diffusion layer formed by phosphorus diffusion using POCl ₃ , 3 is an antireflection film made of a silicon nitride film, 4
Are thin wire electrodes made of silver paste formed by printing, 5
Is a current collecting electrode made of silver paste formed by printing in the same manner as the thin wire electrode 4, 6 is a back electrode made of aluminum paste formed by printing, 7 is an external electrode made of copper, and 8 is an external electrode 7 on the current collecting electrode 5. A solder layer made of tin to be fixed to the
Reference numeral 9 denotes a fillet portion in which the solder layer 8 is formed between the upper surface of the current collecting electrode 5 and the side wall of the external electrode 7. The external electrode 7 is shown by a virtual line.

[0003]

In the conventional solar cell, the external electrode 7 on the current collecting electrode 5 peels off during the manufacturing process or during use, causing a failure such as disconnection. On the other hand, as a result of analyzing the fixing strength between the current collecting electrode 5 and the external electrode 7, the solar cell having the conventional structure has the external electrode 7.
Is fixed on the current collecting electrode 5 by the solder layer 8. More specifically, the fixing strength of the thin solder layer 8 inserted between the current collecting electrode 5 and the external electrode 7 is small, The overall fixing strength is substantially determined by the fillet 9 formed by the solder layer 8 formed between the upper surface of the electrode 4 and the side surface of the external electrode 7. Therefore, it has been found that by increasing the strength of the fillet portion 9, separation between the current collecting electrode 5 and the external electrode 7 can be prevented. That is, the present invention has been made based on such analysis results. A highly reliable solar cell in which the adhesive strength between the external electrode 7 and the current collecting electrode 5 is increased to prevent the external electrode 7 from peeling off. The purpose is to provide.

[0004]

Accordingly, the present inventors have made intensive studies and as a result, formed the current collecting electrode 5 into a plurality of unit current collecting electrodes 5 'to form the fillet portion 9 of the solder layer. The present inventors have found that by increasing the area of the region, the adhesion strength between the external electrode 7 and the current collecting electrode 5 can be increased and the peeling of the external electrode 7 can be prevented, and the present invention has been completed.

That is, the present invention relates to a solar cell in which semiconductor layers of different conductivity types are stacked and one surface of the semiconductor layer is used as a light-receiving surface. A comb-shaped electrode composed of a fine wire electrode and a current collecting electrode connected to the fine wire electrode, and an external electrode fixed with a conductive adhesive so as to overlap the current collecting electrode, wherein the current collecting electrode is In the longitudinal direction of the external electrode, a plurality of unit current collecting electrodes are provided at predetermined intervals between the electrode ends, and the conductive adhesive is also provided below the external electrode at the electrode end. A solar cell, wherein a fillet portion is formed so as to wrap around and connect between a side wall portion of the electrode end and a back surface of the external electrode. In this way, the collecting electrode is divided
By using a plurality of unit current collecting electrodes, a fillet portion can be formed between the side surface of the unit current collecting electrode and the back surface of the external electrode, thereby improving the adhesive strength between the current collecting electrode and the external electrode. Can be. That is, by using such a structure, the area where the fillet portion is formed can be enlarged, and the external electrode can be fixed from different directions such as the side surface and the back surface, so that the fixing strength of the external electrode can be increased. Thereby, peeling of the external electrode during the manufacturing process or during use can be prevented, and a highly reliable solar cell can be provided.

[0006] The electrode width in the direction perpendicular to the longitudinal direction is larger in the unit current collecting electrode than in the external electrode, and extends between the side surface of the external electrode and the upper surface of the unit current collecting electrode. Preferably, a fillet portion to be connected is formed. By using such a structure, in particular, when it is desired to increase the connection strength of the external electrode even if the power generation efficiency of the solar cell is somewhat sacrificed, the electrode width of the unit current collecting electrode is increased, and the area for forming the fillet portion is reduced. This is because the connection strength of the external electrode can be further increased by increasing the size.

[0007] The unit current collecting electrode may have a partially increased electrode width. By using such a structure, it is possible to improve the connection strength of the external electrodes while minimizing a decrease in the power generation efficiency of the solar cell.

The width of the electrode is smaller in the unit current collecting electrode than in the external electrode, and a fillet portion is formed to connect between the back surface of the external electrode and a side surface of the unit current collecting electrode. It may be. By using such a structure, the adhesive strength of the external electrode can be improved without lowering the power generation efficiency of the solar cell.

The electrode width is substantially equal between the external electrode and the unit current collecting electrode, and forms a fillet portion that connects between the side surface of the external electrode and the side surface of the unit current collecting electrode. It may be made. Even by using such a structure, without lowering the power generation efficiency of the solar cell,
This is because the adhesive strength of the external electrode can be improved.

The distance between the electrode ends of the unit integrated electrode is
It is preferable that the distance is larger than the distance between the fine wire electrodes. For example, when the distance between the electrode ends is three pitches rather than one pitch of the fine wire electrode, the connection strength of the external electrodes is improved.

The electrode end of the unit current collecting electrode may be connected by a connecting electrode having a smaller electrode width than the electrode width of the unit current collecting electrode. In this way, by connecting the connection electrodes having a narrower electrode width than the unit current collection electrodes, it is possible to increase the connection strength of the external electrodes, suppress an increase in the resistance value of the electrode portion, and reduce the current collection loss. It is.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS. FIG.
Is a top view of the solar cell according to the present embodiment, FIG.
It is sectional drawing in II, and the same code | symbol as FIG. 11 shows the same or equivalent part in a figure.

In the solar cell according to the present embodiment, a comb-shaped electrode comprising a plurality of fine wire electrodes 4 provided substantially in parallel on a light receiving surface and a current collecting electrode 5 connected to the fine wire electrodes 4;
An external electrode 7 fixed by a solder layer 8 so as to overlap the current collecting electrode 5, and the current collecting electrode 5 has a predetermined interval between the electrode ends in the longitudinal direction of the external electrode 7. And a plurality of unit current collecting electrodes 5 ′ are provided, and the solder layer 8 wraps around the lower end of the external electrode 7 at the end of the electrode, so that the side wall of the end of the electrode and the back surface of the external electrode 7 are separated from each other. A fillet portion 9 is formed so as to connect between them. Specifically, the current collecting electrode 5 is composed of four unit current collecting electrodes 5 ′ arranged on the same straight line.
The distance between the unit current collecting electrodes 5 'is shown in FIG.
In the electrode shown above, the distance is the same as the distance between the fine wire electrodes 4,
On the other hand, in the electrode shown in the lower part of FIG. All the unit current collecting electrodes 5 'are electrically connected to the external electrodes 7 formed thereon. The thin wire electrode 4 is electrically connected to the impurity diffusion layer 2 at the bottom surface.

Here, the fillet portion 9 of the solder 8 is shown in FIG.
As shown in (2), it is formed so as to extend between the upper surface of the current collecting electrode 5 and the side surface of the external electrode 7, and as the number of such fillet portions 9 increases, the adhesive strength of the external electrode 7 to the current collecting electrode 5 increases. . Therefore, in the present embodiment, the current collecting electrode 5 is
FIG. 2 shows the structure of the unit current collecting electrode 5 '
As shown in the figure, at the electrode end of the unit current collecting electrode 5 ',
The solder layer 8 also goes under the external electrode 7 to form a fillet portion 9 between the side wall of the electrode end of the unit current collecting electrode 5 ′ and the back surface of the external electrode 7.

FIG. 3 shows the structure of FIG.
This is the result of measuring the pulling strength required for peeling the external electrode plate 7 from the test piece by a peel test. In the case where there is no division between the collecting electrodes on the horizontal axis (conventional structure), when the division distance between the collecting electrodes corresponds to one pitch of the interval between the fine wire electrodes 4 (the electrode structure shown in the upper part of FIG. 1). 1 shows a case where the separation distance between the collecting electrodes is equivalent to three pitches of the interval of the fine wire electrodes 4 (the electrode structure shown in the lower part of FIG. 1), and the vertical axis shows the external electrode adhesion strength (measured by the peel test). kg / cm ² ). FIG.
As is clear from the above, the unitary current collecting electrode 5 ′ having the current collecting electrode 5 with a divided portion has an increased adhesion strength (adhesive strength) as compared with the conventional structure without division.
Also, it can be seen that the adhesion strength is further increased by increasing the distance of the divided portion from one pitch to three pitches. As described above, by dividing the current collecting electrode 5 into a plurality of unit current collecting electrodes 5 ′, the area where the fillet portion 9 is formed becomes larger than in the conventional structure, and the external electrode 7 and the current collecting electrode 5 are formed. And the adhesive strength with the adhesive can be increased. Thereby, the peeling of the external electrode 7 during the manufacturing process and during use can be prevented, and a highly reliable solar cell can be provided. In addition, in the solar cell according to the present embodiment, since the external electrode 7 is electrically connected to the unit current collecting electrode 5 ′ over the entire surface, the current collecting electrode 5 is divided to collect the current. Losses do not increase so much as to be a problem.

Embodiment 2 A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a top view of the solar cell according to the present embodiment, in which the same reference numerals as in FIG. 1 indicate the same or corresponding parts. In the electrodes shown above, the interval between the unit current collecting electrodes 5 ′ is one of the fine wire electrodes 4.
In the electrode shown below, the pitch is three pitches of the fine wire electrode 4. In the present embodiment, the electrode width in the width direction perpendicular to the longitudinal direction of the current collecting electrode 5 between the unit current collecting electrodes 5 ′ of the first embodiment is smaller than the electrode width of the unit current collecting electrode 5 ′. They are electrically connected by connection electrodes 10. Such connection electrodes 10 can be formed simultaneously in the step of forming the unit current collecting electrode 5 ', and the material is also formed from the same silver paste as the unit current collecting electrode 5'.

As described above, the unit current collecting electrode 5 'is connected by the connecting electrode 10 having a narrower electrode width.
The fillet portion 9 can be formed between the portion not connected to 0 and the back surface of the external electrode 7. Thereby, the connection strength between the unit current collecting electrode 5 'and the external electrode 7 can be increased, and the separation of the external electrode 7 can be prevented. Furthermore, since each unit current collecting electrode 5 'is electrically connected by the connection electrode 10, the unit current collecting electrode 5' is electrically connected only by the external electrode 7 as compared with the case where each unit current collecting electrode 5 'is electrically connected only by the external electrode 7. Thus, the resistance value of the electrode portion (the unit current collecting electrode 5 ′ and the external electrode 7) can be reduced, and the current collecting loss can be reduced. In the present embodiment, the case where the connection electrode 10 is applied to the structure of the first embodiment has been described. However, the connection electrode 10 can be applied to the following third to fifth embodiments.

Embodiment 3 A third embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a top view of the solar cell according to the present embodiment, and FIG.
It is sectional drawing in -V. In the figure, the same reference numerals as those in FIG.
Indicates the same or equivalent parts. In the upper electrode, the interval between the unit current collecting electrodes 5 ′ is the interval of one pitch of the fine wire electrode 4, and in the lower electrode, the distance between the unit current collecting electrodes 5 ′ is 3
The interval is equal to the pitch. In the solar cell according to the present embodiment, as shown in FIG.
At the end of the electrode, the electrode width is partially increased. By adopting such a structure, FIG.
As shown in FIG. 5, in a region where the electrode width is partially widened, a cross section of a fillet portion 9 in which the solder layer 8 is formed between the upper surface of the unit current collecting electrode 5 ′ and the side surface of the external electrode 7 is shown. For example, as compared with the structure shown in FIG. 2, the connection strength between the unit current collecting electrode 5 ′ and the external electrode 7 can be increased. That is, the unit current collecting electrode 5 '
Increasing the area of the electrode leads to an increase in the cross-sectional area of the fillet portion 9 formed on the upper surface thereof and an increase in the connection strength between the unit current collecting electrode 5 'and the external electrode 7.
On the other hand, the area of the light receiving surface of the solar cell is reduced, and the power generation efficiency is reduced. Therefore, in the present embodiment, by forming a region in which the electrode width of the unit current collecting electrode 5 ′ is partially widened, the unit current collecting electrode 5 ′ is prevented from being reduced in area, and the unit current collecting electrode 5 ′ is more unitary than in the first embodiment. The connection strength between the electrode 5 'and the external electrode 7 can be increased. In the present embodiment, a large area is provided at the electrode ends at both ends of the unit current collecting electrode 5 ', but it may be provided in a region other than the end.

Embodiment 4 A fourth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a top view of the solar cell according to the present embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts. In the electrodes shown above, the interval between the unit current collecting electrodes 5 ′ is one of the fine wire electrodes 4.
In the electrode shown below, the pitch is three pitches of the fine wire electrode 4.

In the solar cell according to the third embodiment,
While the unit collecting electrode 5 'is partially widened,
In the solar cell according to the present embodiment, the unit current collecting electrode 5 ′
In all regions, the area of the unit current collecting electrode 5 'is increased. That is, even if a section in the electrode width direction is taken at any part of the unit current collecting electrode 5 ', a sectional structure as shown in FIG. 6 is obtained. Therefore, even if the area of the light receiving surface of the solar cell is slightly reduced, a structure as shown in FIG. 7 is used when there is a demand to increase the connection strength between the unit current collecting electrode 5 ′ and the external electrode 7. This makes it possible to further increase the connection strength between the unit current collecting electrode 5 'and the external electrode 7 and prevent the external electrode 7 from peeling off as compared with the case of the first embodiment.

Embodiment 5 A fifth embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a top view of the solar cell according to the present embodiment, and FIGS.
0 is a sectional view taken along line VIII-VIII. In the figure, FIG.
The same reference numerals indicate the same or corresponding parts. In the electrodes shown above, the interval between the unit current collecting electrodes 5 ′ is
In the electrode shown below, the pitch is three pitches of the fine wire electrode 4.

In this embodiment, the width of the unit current collecting electrode 5 ′ is equal to or smaller than the width of the external electrode 7. FIG. 9 shows the electrode width of the unit current collecting electrode 5 ′.
FIG. 8 is a cross-sectional view taken along the line VIII-VIII when the width is smaller than the electrode width of the external electrode 7. As is clear from the figure, in the first embodiment, the fillet portion 9 formed between the upper surface of the unit current collecting electrode 5 ′ and the side wall of the external electrode 7 is replaced with the side surface of the unit current collecting electrode 5 ′. , And the back surface of the external electrode 7. By using such a structure, the cross-sectional area of the fillet portion 9 formed between the unit current collecting electrode 5 ′ and the external electrode 7 is maintained to be equal, and the same connection strength as in the first embodiment is obtained. By making the electrode width of the unit current collecting electrode 5 ′ smaller than the electrode width of the external electrode 7 while maintaining, the area of the light receiving surface of the solar cell surface can be increased, and the power generation efficiency of the solar cell can be improved. Becomes possible.

On the other hand, FIG. 10 shows that the electrode width of the unit current collecting electrode 5 ′ and the electrode width of the external electrode 7 are the same, and the fillet 9 is formed by the side surface of the unit current collecting electrode 5 ′ and the external electrode 7. 7 is formed so as to cross over the side surface of the first embodiment. By forming the fillet portion 9 in this way, the first embodiment
As described above, it is possible to obtain the same connection strength as when the fillet portion 9 is formed between the upper surface of the unit current collecting electrode 5 ′ and the side surface of the external electrode 7. Further, by making the electrode width of the unit current collecting electrode 5 'as narrow as the electrode width of the external electrode 7, the area of the light receiving surface of the solar cell can be increased, and the power generation efficiency of the solar cell is improved. It becomes possible.

[0024]

As is apparent from the above description, according to the present invention, the area in which the fillet portion is formed is increased by dividing the current collecting electrode into a plurality of unit current collecting electrodes. The connection strength between the external electrode and the current collecting electrode can be increased, and a highly reliable solar cell in which peeling of the external electrode is prevented can be provided.

Further, by increasing the area of the unit current collecting electrode in part or all, the connection strength of the fillet portion can be increased, and a highly reliable solar cell can be provided.

Also, by making the electrode width of the unit current collecting electrode equal to or smaller than that of the external electrode, the area of the light receiving surface of the solar cell can be increased while preventing the external electrode from peeling off. Power generation efficiency can be improved.

Further, by forming a structure in which the unit current collecting electrodes are connected by connecting electrodes having a narrower electrode width, it is possible to reduce the resistance value of the electrode portion and reduce the current collecting loss. Become.

[Brief description of the drawings]

FIG. 1 is a top view of a solar cell according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along a line II.

FIG. 3 is a measurement result of external electrode adhesion strength.

FIG. 4 is a top view of the solar cell according to the second embodiment of the present invention.

FIG. 5 is a top view of the solar cell according to Embodiment 3 of the present invention.

FIG. 6 is a sectional view taken along line VV.

FIG. 7 is a top view of a solar cell according to Embodiment 4 of the present invention.

FIG. 8 is a top view of a solar cell according to a fifth embodiment of the present invention.

FIG. 9 is a sectional view taken along line VIII-VIII.

FIG. 10 is a sectional view taken along line VIII-VIII.

FIG. 11 is a perspective view of a solar cell according to a conventional structure.

FIG. 12 is a top view of a solar cell according to a conventional structure.

FIG. 13 is a sectional view taken along XII-XII.

[Explanation of symbols]

1 semiconductor substrate, 2 impurity diffusion layer, 3 anti-reflection film,
4 fine wire electrode, 5 current collecting electrode, 5 'unit current collecting electrode, 6
Back electrode, 7 external electrode, 8 solder layer, 9 fillet, 10 connection electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Takashi Ishihara, 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Akihiro Kuroda 2-3-2, Marunouchi, Chiyoda-ku, Tokyo (72) Inventor Shinji Nakamoto 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 5F051 BA03 FA06 FA13 FA14 FA16 FA30

Claims (7)

[Claims] 1. A solar cell in which semiconductor layers of different conductivity types are stacked and one surface of the semiconductor layer is used as a light receiving surface, and a plurality of thin wire electrodes provided substantially in parallel on the light receiving surface. A comb-shaped electrode composed of a current collecting electrode connected to the thin wire electrode, and an external electrode fixed with a conductive adhesive so as to overlap the current collecting electrode; In the direction, a plurality of unit current collecting electrodes are provided at predetermined intervals between the electrode ends, and the conductive adhesive wraps around the lower part of the external electrode at the electrode ends, and A solar cell comprising a fillet portion that connects between a side wall portion of an extreme portion and a back surface of the external electrode. 2. The electrode width in a direction perpendicular to the longitudinal direction is:
The unit current collecting electrode is wider than the external electrode, and a fillet portion is formed to connect between a side surface of the external electrode and an upper surface of the unit current collecting electrode. Item 2. The solar cell according to item 1. 3. The solar cell according to claim 2, wherein the unit current collecting electrode has a partially increased electrode width. 4. The unit electrode according to claim 1, wherein the width of the unit collector electrode is smaller than that of the external electrode, and a fillet portion is formed to connect between the back surface of the external electrode and a side surface of the unit collector electrode. The solar cell according to claim 1, wherein: 5. A fillet portion in which the electrode width is substantially equal between the external electrode and the unit current collecting electrode, and is connected between a side surface of the external electrode and a side surface of the unit current collecting electrode. The solar cell according to claim 1, wherein: 6. The solar cell according to claim 1, wherein a distance between electrode ends of the unit integrated electrode is wider than a distance between the fine wire electrodes. 7. The unit current collecting electrode according to claim 1, wherein an electrode end of the unit current collecting electrode is connected to a connection electrode having a smaller electrode width than an electrode width of the unit current collecting electrode. Solar cell.