Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
2000-07-12
2002-09-17
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C136S252000, C136S265000, C136S244000, C136S245000, C136S251000, C438S455000, C438S066000, C438S067000, C438S057000, C438S458000, C438S497000, C438S477000, C156S196000, C156S212000, C156S220000, C156S224000, C156S226000
Reexamination Certificate
active
06452091
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing thin-film single-crystal devices, solar cell modules, and a method of producing the same. The thin-film single-crystal devices include, for example, photoelectric converters such as solar cells and devices for a circuit for driving image display elements such as liquid crystal display elements.
2. Related Background Art
A solar cell is becoming in common use as an independent source for driving various types of electrical machinery and apparatus or as a source for system interconnection with commercial electric power. As semiconductors constituting a solar cell, silicon and gallium arsenide are generally used. In order to obtain a high photoelectric conversion efficiency (efficiency to convert optical energy into electric power), these semiconductor single-crystals are preferably used.
In large-area image display elements such as liquid crystal display elements, with an increasing demand for a more high-fine and high-speed image display in recent years, a drive circuit formed within an element is required to have much higher capability. In order to meet this demand, the drive circuit should be formed on single-crystal silicon rather than amorphous or polycrystal silicon.
When using single-crystal semiconductors for the above purpose, there arise several problems. For example, in cases where silicon is used in a solar cell, the thickness of the single-crystal wafers commonly used is as thick as about 300 to 600 &mgr;m, while the film thickness required for the absorption of the incident sunlight is about 30 to 50 &mgr;m. Under recent circumstances where the single-crystal silicon used in solar cells accounts for ten percent of the total production, its consumption should be reduced. In image display devices, because of the form in which they are used, the light must be transmitted through the areas among the elements in a drive circuit. However, the single-crystal wafers in a common use are difficult to have such a structure formed thereon. In addition, the thickness of a single-crystal layer required for the drive element itself is only 1 &mgr;m or less, the rest portion merely serves as a supporting substrate.
In order to solve this problem, thin-film single-crystals having a suitable thickness should be selected depending on the purpose for which it is used; however, as long as the prior arts are employed, a single-crystal layer having a thickness of 300 &mgr;m or less is difficult to produce. Specifically, in some methods of prior art, since single-crystal substrates are produced in such a manner as to slice and polish an ingot single-crystal obtained by subjecting a melt of crystal material to crystal growth, single-crystal of 300 &mgr;m or less in thickness are difficult to obtain. In some other methods, in order to obtain a high-quality thin-film single-crystal for special purposes, etching is conducted on the back side of a single-crystal substrate having a thickness of several hundreds &mgr;m; however, a high-quality thin-film single-crystal is considerably difficult to produce by these methods. Recently, however, the method disclosed in Japanese Patent Application Laid-Open No. 7-302829 enables the peeling of a thin-film single-crystal from a substrate on which the thin-film single-crystal is epitaxially grown, and a technique disclosed in Japanese Patent Application Laid-Open No. 9-331077 enables the peeling of a portion ranging from the surface of a single-crystal substrate to a certain depth, as a thin-film, from the substrate. These methods, however, also have a problem that lattice defects may appear in a thin-film single-crystal during the peeling operation, leading to a reduction in quality of the thin-film single-crystal, and in an extreme case, cracks appear in the thin-film single-crystal, leading to a remarkable reduction in production yield. Thus, effective solutions of the above problems have been desired.
Roughly speaking, there are two common types of solar cells at present: solar cells using amorphous silicon and solar cells using crystalline silicon. And these solar cells are devised in various ways depending on their applications so as to make full use of their respective characteristics.
For example, amorphous silicon solar cells, which are formed by depositing an amorphous silicon film on a conductive substrate by the plasma CVD method and forming a transparent conductive layer on the amorphous silicon film, are inexpensive, lightweight, and excellent in impact resistance and flexibility compared with solar cells using crystalline silicon. Making good use of these characteristics, attempts have been made to use an amorphous silicon solar cell as a solar cell incorporated with building materials, that is, as an amorphous silicon solar cell incorporated with roof, wall, etc. of building.
In this case, a solar cell is used as a building material by bonding a reinforcing material to its non-light-receiving side via a bonding agent. Bonding a reinforcing material enhances mechanical strength of a solar cell module and prevents warps and strain, due to changes in temperature. This type of solar cell is often installed on a roof because more sunlight can be collected there. In its use as a solar cell incorporated with roofing, conventionally the installation has been performed as follows: fitting a frame to the solar cell, installing a stand on a roof, and installing the solar cell on the stand. On the other hand, the solar cell with a reinforcing material bonded thereto can be directly installed on a roof as a roofing material by bending the reinforcing material. This allows to materially reduce the raw material cost as well as the number of operational steps, and hence to provide a roof with solar cells at a low price.
In addition, the solar cell can be made lightweight since it requires neither frame nor stand. Thus, the solar cell can be treated as a metal roofing, which has lately attracted considerable attention, due to its excellent workability, lightweight and superior earthquake resistance.
The solar cell module incorporated with roofing, for example, disclosed in Japanese Patent Application Laid-Open No. 7-302924 is excellent in workability since the portions where roof materials engage with each other (the region where photovoltaic elements are not arranged) have been subjected to bending just like ordinary roofing. It is also easy to handle in terms of machining since the current molding machine used for ordinary roofing is applicable as it is. It enables the installation of a roof with solar cells at low costs.
As described above, since it is preferable that the solar cell module incorporated with roofing is constructed in such a manner as to be lightweight and machinable like ordinary roofing, the most common type of solar cell module incorporated with roofing has a construction in which a photovoltaic element is bonded to or installed on a steel plate (roofing) and subjected to insulation sealing with resin, as shown in
FIGS. 10A and 10B
.
FIGS. 10A and 10B
are a schematic perspective view of a plate-type solar cell module incorporated with roofing and a cross-sectional view taken along the line
10
B—
10
B of
FIG. 10A
, respectively. In
FIGS. 10A and 10B
, reference numeral
1001
denotes a surface protective material, numeral
1002
a filler material, numeral
1003
a photovoltaic element and numeral
1004
a reinforcing plate.
An amorphous silicon solar cell module, when used as a solar cell module incorporated with roofing described above, has preferable and excellent characteristics, but has problems that its photoelectric conversion efficiency (efficiency to convert optical energy into electric power, hereinafter sometimes refereed to as “conversion efficiency”) is generally low compared with that of a crystalline silicon solar cell and its properties may deteriorate due to light (optical deterioration) to some extent when it is used for a long period of time.
On the other hand, for a crystalline silicon solar cell, its ph
Iwane Masaaki
Iwasaki Yukiko
Nakagawa Katsumi
Sakaguchi Kiyofumi
Takai Yasuyoshi
Canon Kabushiki Kaisha
Diamond Alan
Fitzpatrick ,Cella, Harper & Scinto
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