JPH073879B2 - Solar cell - Google Patents

Description

The present invention relates to a solar cell using a corrugated substrate.

[Conventional technology]

Previously, `` The Conference Record of the 20th IEEE P
hotovoltaic specialists conference 1988 pp.792-79
As shown in "5", the V-grooves formed on the two main surfaces of the substrate were oriented in the same direction, so a cross beam was provided at a right angle to the V-grooves to enhance the mechanical strength.

[Problems to be Solved by the Invention]

As described above, conventionally, the strength of the element was increased by adding a cross beam, but since the area of the cross beam cannot be increased to improve the element characteristics, sufficient mechanical strength can be obtained. Was difficult to obtain.

An object of the present invention is to increase the mechanical strength of a corrugated substrate without deteriorating the device characteristics.

[Means for Solving the Problems]

In order to achieve the above object, the present invention has a structure in which at least some of the directions of the plurality of V-shaped grooves formed on the two main surfaces of the substrate have directions different from the other directions.

[Operation] The above means will be described with reference to the drawings.

As shown in FIG. 2, the conventional corrugated substrate has a V groove.
By providing the cross beam 100 orthogonal to 20, the mechanical strength with respect to the stress applied in the AA 'direction in the figure is maintained. In order to increase the strength using this structure, it is necessary to increase the area of the cross beam 100. However, B-
As can be seen from the B ′ cross-sectional view, the substrate thickness at the cross beam portion is larger than that at other portions, so that if this area increases, the average thickness of the substrate cannot be kept thin, and as a result, the device characteristics ( Output voltage) deteriorates.

In order to solve the above problems, the region having the V groove is subdivided into the structure shown in FIG. 1, for example. In this structure, the main surface of the substrate is divided into large and small squares. In the larger square, for example, areas 1, 2, and 3 in the drawing are areas having V grooves parallel to the X axis, and areas 11 and 12 are areas having V grooves parallel to the Y axis. Thereby, for example, on any straight line that crosses the main surface of the substrate in parallel with the Y axis, there is always a region having a V groove parallel to the X axis. In addition, even in a straight line crossing parallel to the X axis, there is always a region having a V groove parallel to the Y axis. Thereby, even when stress is applied to the main surface of the substrate in a direction parallel to the X axis or the Y axis, the mechanical strength of the substrate can be kept sufficiently large.

Although the above description has described the minimum repeating pattern in each region, it goes without saying that it is necessary to cover the main part of the substrate with this pattern. In addition, regions 2, 11 and 3, 12 in the figure are respectively V-parallel to the X-axis and Y-axis.
The same can be said for a region having a groove. Further, the small square portion may be divided into regions having V grooves parallel to the X axis or the Y axis by any rule. Further, the V-grooves parallel to the X-axis and the Y-axis in the above description may be oriented in a diagonal direction such as the Y'-axis in the figure.

Most importantly, there is at least one region having a V-groove that is not substantially parallel to the straight line on any straight line across the main surface of the substrate.

The application examples of the present invention are shown below.

FIG. 3 shows an example using a rectangle and a square. In this example, for example, the regions 1, 2, 3, 4, 5 and the regions 11, 12, 13, 14 are regions having V grooves in different directions to achieve the above object.

FIG. 4 shows an example using the L-shape. In this example, for example, the regions 1, 2, 3, ... And the regions 11, 12, 13, ... Are regions having V grooves in different directions to achieve the above object.

FIG. 5 shows an example using only a rectangle. In this example,
For example, the above-mentioned object can be achieved by forming the regions 1, 2, 3, ... And the regions 11, 12, 13, ... With V grooves having different directions.

FIG. 6 shows an example using a T-shape. In this example, for example, the regions 1, 2, 3, ... And the regions 11, 12, ... Are regions having V grooves in different directions to achieve the above object.

FIG. 7 shows an example using a cross shape. In this example, for example, the regions 1, 2, ... And the regions 11, 12, ... Are regions having V grooves in different directions to achieve the above object.

FIG. 8 shows an example using a key type. In this example, for example, the regions 1, 2, ... And the regions 11, 12, ... Are regions having V grooves in different directions to achieve the above object.

Next, another example will be described with reference to FIG. In this example, the main region 1 of the substrate has V-grooves parallel to the Y-axis and region 2 has V-grooves parallel to the X-axis. It is obvious that the above object can be achieved by such a structure.

FIG. 10 shows an application of the example explained in FIG. In this example, the shape of the area 2 in FIG. 9 is replaced with the shape of the areas 2, 3 and 4 in this figure.

Although various examples have been described so far, what is a combination satisfying that there is at least one region having a V groove that is not parallel to the straight line on the straight line crossing the main surface of the substrate? Even in any combination, the object of the present invention can be achieved.

Furthermore, as another application example, the main surface of the substrate is shown in FIG.
In one example, regions 1, 3 are divided into regions having V grooves parallel to the X axis, and regions 2 and 4 are divided into regions having V grooves parallel to the Y axis. Also in this example, various combinations can be obtained by, for example, aligning the directions of the V-grooves of the regions 1 and 2 and the regions 3 and 4 or switching the directions of the respective V-grooves.

Further, as shown in FIG. 12, it is possible to divide the area of the main surface of the substrate and combine the directions of the V-grooves of the respective areas.

Although it is considered in FIGS. 11 and 12 that the main surface of the substrate is covered with one of these, a plurality of these may be combined to cover the main surface of the substrate.

So far, the V groove has been described, but it goes without saying that this is also effective when the corrugated substrate is thinned using a U groove, a rectangular groove, or the like. The same thing can be said when the substrate is made of not only Si but also a glass substrate or a compound semiconductor.

〔Example〕

 An embodiment of the present invention will be described below with reference to FIG.

In this embodiment, the structure composed of square areas of two types, large and small, described in FIG. 1 is used. Each area is divided into areas having V-grooves in the vertical direction and the horizontal direction as shown by the broken lines in the figure. The side a of the large square is 20 mm, and the side b of the small square is 10 mm. Also, at the boundary of each area,
The V grooves intersect as shown in the enlarged view, and the pitch e of the V grooves is 240 μm. 250μ with (100) surface on the substrate
Using an m-thick Si single crystal substrate, a 1000 Å-thick oxide film is formed on the front and back surfaces by a normal thermal oxidation method.
It was processed into a thin wire with m width. This detail is shown by the solid line in the enlarged view of FIG. The oxide film on the back surface was formed in the same manner as the front surface, with a shift of a half cycle from the fine line pattern on the front surface. Using this oxide film as an etching mask, Si was anisotropically etched with a vidrazine solution to form a corrugated section as shown in the section AA 'in FIG. As a result, the substrate thickness t becomes 50 μm.

As can be seen from FIG. 13, by combining a region having a vertical groove and a region having a horizontal groove, every cross section of the device always includes a vertical V groove and a horizontal V groove. It was possible to maintain extremely high strength against shocks during the manufacture and handling of and the stress applied after it was incorporated into the device. In this embodiment, the method of forming the V groove by anisotropic etching has been described, but this may be machined by dicing or laser scribing. In this case, since anisotropic etching is not used, a wafer having a surface other than (100) may be used. Also, instead of the V groove, a U groove or other cross-sectional shape may be used. In addition, in this embodiment, Si
Although the crystal substrate has been described, the substrate is not limited to the Si crystal, and may be a compound semiconductor such as GaAs or InP or a Ge crystal. Further, these are not limited to single crystals, and may be polycrystalline substrates. In addition, single crystal on glass or ceramic substrate,
In a structure in which a polycrystalline, microcrystalline, or amorphous photoelectric conversion layer is formed, the substrate having the structure of the present invention can have high strength even when the substrate is thin.

〔The invention's effect〕

When a solar cell having a relatively large area is manufactured using a very thin substrate, a corrugated structure having a V-shaped groove in one direction does not have sufficient mechanical strength in a specific direction. However, by adopting the structure of the present invention, the mechanical strength of the solar cell became extremely high against stress from all directions.

[Brief description of drawings]

FIG. 1 shows an example of the structure of the present invention. FIG. 2 shows an example of a conventional structure. FIG. 3 shows an example of the structure of the present invention. FIG. 4 shows an example of the structure of the present invention. FIG. 5 shows an example of the structure of the present invention. FIG. 6 shows an example of the structure of the present invention. FIG. 7 shows an example of the structure of the present invention. FIG. 8 shows an example of the structure of the present invention. FIG. 9 shows an example of the structure of the present invention.
FIG. 10 shows an example of the structure of the present invention. FIG. 11 shows an example of the structure of the present invention. FIG. 12 shows an example of the structure of the present invention. FIG. 13 shows an embodiment of the present invention. Explanation of reference numerals 1,2,3,4,5,6,11,12,13,14 ... V groove forming region, 20 ... V groove, 1
00 ... Cross beam.

Claims (1)

[Claims] 1. A solar cell having a corrugated Si single crystal substrate, wherein the corrugation has linear V-grooves in two kinds of directions orthogonal to each other on a desired region of the front surface and the back surface of the Si single crystal substrate at the same pitch. The linear V-grooves in the two directions described above are arranged so that an area consisting of only the other linear V-groove exists on the extension of one linear V-groove. A solar cell characterized by.