JP2934369B2 - Solar cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell,
In particular, it relates to a thin solar cell used for artificial satellites.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. 4 and 5 are perspective views of a conventional solar cell, FIG. 6 is a cross-sectional view of a conventional solar cell, and FIG. 7 is a cross-sectional view showing a state in which a plurality of conventional solar cells are connected in series. It is.

One technique for increasing the power generated by a solar cell is to increase the photocurrent.
For example, incident light is reflected multiple times on the solar cell surface, and fine pyramid-shaped irregularities called textures are formed on the light receiving surface side of the solar cell substrate in order to reduce the reflection of the incident light and increase the optical path length. How to In recent years, as shown in FIG. 4, a pyramid 10 has an inverted pyramid in which the apex is directed toward the inside of the solar cell substrate, and as shown in FIG. Some have been formed. (Hereinafter, the shape on the light-receiving surface side of the substrate of these solar cells having fine irregularities is collectively referred to as "non-reflective shape.") In the figure, reference numeral 12 denotes a substrate and 13 a back electrode.

FIG. 6 is a conceptual sectional view of a conventional solar cell having a non-reflective shape. A surface electrode 14 is provided on the light receiving surface side of the substrate 12 having a non-reflective shape, and a surface electrode connection portion 15 is provided on the surface. 13 is a back electrode,
Reference numeral 16 denotes a back electrode connecting portion connected by an interconnector 17 as described later.

FIG. 7 is a sectional view of an embodiment in which a plurality of solar cells of FIG. 6 are connected in series. here,
Although the description will be given taking the adjacent solar cells 20 and 21 as an example, the connection of other solar cells is the same. Back electrode 13 of solar cell 20 and front electrode 1 of solar cell 21
4 are connected by an interconnector 17. The interconnector 17 is connected to the back electrode 13 and the front electrode 14 via the back electrode connection part 16 and the front electrode connection part 15, respectively. A cover glass 18 is adhered to the upper surface side of the solar cell via an adhesive 19.

Here, the surface electrode connection portion 15 of the solar cell 21 has a fine unevenness because the surface electrode 14 is formed on the substrate 12 whose light-receiving surface is non-reflective. Also, the front electrode connecting portion 15 of the solar cell 21 and the back electrode connecting portion 16 of the solar cell 20 having the light receiving surface side of the substrate having such a surface shape, and the interconnector 1
The connection 7 is connected by a welding connection method or a solder connection method.

At this time, in order to perform a highly reliable connection, a pressure of a certain level or more is applied from above the interconnector 17, and the interconnector 17 is connected to the front electrode connecting portion 15 or the back electrode connecting portion 16. Generally, the method of applying the required heat is selected.

In particular, in the case of a solar cell for an artificial satellite,
Since the interconnector is made of a metal having a low electric resistance such as silver, a wide temperature cycle in the universe (for example, a temperature range of -180 ° C to + 100 ° C) due to a difference in linear expansion coefficient between the solar cell substrate and the interconnector. 10
00 cycle), a large stress is generated at the connection point,
In the worst case, it will be open. For this reason, it is important for the connection of the interconnector to be a highly reliable connection that can withstand stress.

[0009]

However, when the connection between the front electrode connection portion 15 and the interconnector 17 and the connection between the rear electrode connection portion 16 and the interconnector 17 are made, the substrate corresponding to the connection portion is used. Since the light-receiving surface side of the substrate 12 has a non-reflective shape, local stress concentration occurs during pressurization and heating necessary for highly reliable connection, and the substrate 12 is often broken. In particular, in the case of a thin solar cell having a substrate material thickness of 100 μm or less, the substrate was frequently broken.

The order of the steps is as follows.
An interconnector 17 is connected to one surface electrode 14,
After the cover glass 18 is bonded with the adhesive 19, the interconnector 17 is connected to the back electrode 13 of the adjacent solar cell 20, so that the connection at the back electrode connection portion 16 breaks the solar cell substrate 12. If so, the damage is enormous.

On the other hand, when the entire light receiving surface of the solar cell is flattened in order to prevent the solar cell from breaking when the interconnector is connected, the photocurrent is reduced, and the generation of the solar cell is reduced. The power is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photovoltaic cell capable of highly reliable interconnector connection without reducing photocurrent or causing substrate cracking.

[0013]

In order to achieve the above object, the present invention provides a light receiving surface having an uneven shape on a substrate surface,
In a solar cell in which electrodes externally connected to each other by an interconnector are provided on the front and back surfaces of the substrate, the surface electrode mounting surface of the substrate is flattened, and the surface of the substrate includes The surface facing the interconnector connection portion is formed flat.

[0014]

[Function] Since the connection portion of the interconnector is flat, when connecting and using a plurality of solar cells,
Even if the pressure and heat necessary for connection are applied to the cell, the stress on the substrate is dispersed, and stress concentration does not occur as in the case of pressing on a conventional uneven substrate surface, and the substrate may be broken. Absent.

Further, the area of the portion to be flattened is only the connection portion of the interconnector, and is very small as compared with the whole cell. Therefore, even if the portion of the anti-reflection structure slightly increases, There is almost no output reduction.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. 1 is a cross-sectional view of a solar cell according to one embodiment of the present invention, FIG. 2 is a cross-sectional view showing a state where a plurality of solar cells of FIG. 1 are connected, and FIG. 3 is a top view of the same.

The same functional parts as those in the conventional example shown in FIGS. 4 to 7 are denoted by the same reference numerals. Here, only the points different from the conventional example will be mainly described. As is clear from FIGS. 1 and 2, the feature of this embodiment is that the mounting surface of the surface electrode 1 of the substrate 3 and the surface electrode connection portion 2 are made flat without using a non-reflective shape as in the related art, The light receiving surface portion 4 of the substrate 3 facing the connection portion 16 is also flat. The other portions have a non-reflective shape as in the related art.

As described above, the solar cell of this embodiment is
Since the light receiving surface of the substrate 3 facing the front electrode connection portion 2 and the back electrode connection portion 16 is flat, even if pressure and heat necessary for highly reliable connection of the interconnector 17 are applied,
The stress applied to the substrate at that time is dispersed, so that stress concentration does not occur. This is because, when only the part to which the interconnector 17 is connected is viewed, the state is equivalent to a flat solar cell interconnector connection having no non-reflective shape on the light receiving surface side of the substrate.

Further, by flattening the surface of the light receiving surface portion 4 of the substrate 3 corresponding to the front surface connection portion 2 and the back surface electrode connection portion 16 of the substrate 3 to which the interconnector 17 is connected, the non-reflection structure of that portion is obtained. However, as is clear from FIG. 3, the area of the flat portion is very small compared to the area of the entire cell, and the reduction in the power generated by the solar cell due to the provision of the flat portion does not increase. , Is at most about 0.2%, and has almost no effect.

As described above, according to the solar cell of the present embodiment, a highly reliable interconnector connection can be made without reducing the photocurrent or causing the substrate to crack.

[0021]

As described above, according to the present invention,
A photovoltaic cell capable of highly reliable interconnector connection can be realized without reducing photocurrent or causing substrate cracking.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a solar cell according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state where a plurality of solar cells of FIG. 1 are connected.

FIG. 3 is a top view of FIG. 2;

FIG. 4 is a perspective view of a conventional solar cell.

FIG. 5 is a perspective view of a solar cell according to another conventional example.

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

FIG. 7 is a cross-sectional view showing a state in which a plurality of solar cells of FIG. 6 are connected.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front electrode 3 Substrate 4 Flat part 13 Back electrode 16 Back electrode connection part 17 Interconnector

Claims (1)

(57) [Claims] An uneven light receiving surface is formed on a substrate surface,
In a solar cell in which electrodes externally connected to each other by an interconnector are provided on the front and back surfaces of the substrate, the surface electrode mounting surface of the substrate is flattened, and the back surface electrode of the substrate surface is A solar cell, wherein a surface facing an interconnector connecting portion is formed flat.