Process for producing solar cells and solar cells produced...

Details Process for producing solar cells and solar cells produced... Process for producing solar cells and solar cells produced...

1999-05-03

2001-02-06

Smith, Matthew (Department: 2825)

Semiconductor device manufacturing: process

Making device or circuit responsive to nonelectrical signal

Responsive to electromagnetic radiation

C257S447000

Reexamination Certificate

active

06184056

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese application No. HEI 10(1998)-137032 filed on May 19, 1998, whose priority is claimed under 35 USC §119, the disclosure of which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing solar cells and solar cells produced thereby, and more particularly relates to a process for producing solar cells for use in outer space which can be borne by an artificial satellite and solar cells produced by the process.
2. Description of Related Art
In recent years, solar cells which can be used in outer space are under active development.
Solar cells in use in space are exposed to cosmic rays flying around in huge numbers. As a result, the solar cells deteriorate in properties including conversion efficiency with varying degrees of deterioration depending upon the kind of the solar cells. Accordingly, it is one of the most important challenges in development of space-use solar cells to realize the highest possible output for an final output (i.e., minimum output during their service) in view of irradiation doses in a use environment.
Typical space-use solar cells are produced by the following process:
First, as shown in FIG.
12
(
a
), a semiconductor substrate
50
is used. The semiconductor substrate
50
is cut from an ingot of single-crystal silicon usually in the form of a wafer of about 300 &mgr;m thickness.
Next, as shown in FIG.
12
(
b
), this substrate
50
is made into a thin-film silicon substrate
51
of about 100 to 200 &mgr;m thickness by etching with an aqueous acidic or alkali solution or by polishing. Subsequently, the thin-film silicon substrate
51
is washed a number of times. Then, p-type diffusion layers (not shown) are formed on one surface of the silicon substrate
51
, for example, on a surface opposite to a photo-receptive face-to-be (i.e., on a non-photo-receptive face).
Subsequently, high-concentration n-type diffusion layers (not shown) are formed on the photo-receptive face. Thereafter, as shown in FIG.
12
(
c
), an insulating film is partially removed, and n-electrodes
52
of Ag/Pd/Ti and p-electrodes (not shown) of Ag/Pd/Ti/Al are formed on the photo-receptive face and on the non-photo-receptive face, respectively.
Then, as shown in FIG.
12
(
d
), the resulting substrate is separated into individual cells. Thus solar cells of single-crystal silicon are obtained.
Also solar cells in which both electrodes contact on a rear surface are well known. The solar cells of this type are produced by the following process:
First, a semiconductor substrate
50
as shown in FIG.
13
(
a
) which is cut in the form of a wafer as in the above-described process is made into a thin-film silicon substrate
51
as illustrated in FIG.
13
(
b
). Subsequently, the silicon substrate
51
is subjected to a number of washings.
Thereafter, on one surface of the silicon substrate
51
, for example, on the non-photo-receptive face thereof, p-type diffusion layers and n-type diffusion layers are formed in the form of islands.
Then, as shown in FIG.
13
(
c
), an insulating film is partially removed, and electrodes, for example, of Ag/Pd/Ti/Al are formed as p-electrodes
54
and n-electrodes
52
so as to come in contact with the island-like p-type and n-type diffusion layers, respectively.
Subsequently, as in the aforementioned process, the resulting substrate is divided into individual cells, as shown in FIG.
13
(
d
). Thus solar cells of single-crystal silicon are obtained.
Generally, the thinner the substrate of a solar cell is, the less susceptible to the effect of cosmic rays the solar cell is.
However, in the case of a substrate of a crystalline semiconductor, the thinner the substrate is, the stronger the possibility of the substrate breaking during manufacture of solar cells becomes. Therefore, it is actually impossible to manufacture thin solar cells from a very thin substrate of a crystalline semiconductor. In a conventional technique, the marginal thickness of the substrate is about 100 &mgr;m. Furthermore, in this case, it is required to process an originally thick substrate into a substrate of about 100 &mgr;m thickness before entering the process of constructing a solar cell structure.
On the other hand, in the case where an amorphous semiconductor is used, it is possible to obtain very thin solar cells. This is because the amorphous semiconductor can usually be formed in extreme thin films on transparent substrates by CVD and the thin films can be used for the solar cells. In addition to that, the amorphous semiconductor can have relatively free band gaps, and accordingly is excellent in radiation resistance. However, the films of the amorphous semiconductor include lots of elements nucleating re-association of minority carriers such as in-gap levels and grain boundaries within the full area of the films, and the films of the amorphous semiconductor have a shorter diffusion length for carriers, which greatly affects the conversion efficiency of solar cells, compared with single-crystal silicon. Therefore, a high initial conversion efficiency cannot be expected unless a breakthrough technique is introduced to the thin films.
In contrast, with solar cells of crystalline materials typified by silicon, a high initial conversion efficiency before exposure to radiation can be realized. However, every crystalline material has its own fixed band gap. In addition to that, a thin substrate thereof is difficult to handle as described above. Therefore, it has been very hard to improve the radiation resistance of the solar cells of this type.
SUMMARY OF THE INVENTION
The present invention provides a process for producing a solar cell comprising the steps of forming at least one electrode on a first surface of a semiconductor substrate for constructing a solar cell, attaching a support substrate to the first surface of the semiconductor substrate on which said electrode is formed, and then processing the semiconductor substrate into a thin-film semiconductor substrate.
In another aspect, the invention provides a solar cell produced by the above-mentioned process.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


REFERENCES:
patent: 4824489 (1989-04-01), Cogan et al.
patent: 5430616 (1995-07-01), Katsu et al.
patent: 5472885 (1995-12-01), Matsumo et al.
patent: 5828117 (1998-10-01), Kondo et al.
patent: 5972732 (1999-10-01), Gee et al.
patent: 0 474 349 A2 (1992-03-01), None
patent: 63-261761 (1988-10-01), None
patent: 2-001914 (1990-01-01), None
patent: 2-202023 (1990-08-01), None
patent: 3-044067 (1991-02-01), None
patent: 3-050713 (1991-03-01), None
patent: 4-091482 (1992-03-01), None
patent: 8-274286 (1996-10-01), None
patent: 89/05521 (1989-06-01), None

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