Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
2001-02-26
2002-09-17
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S249000, C136S251000, C257S443000, C257S448000, C438S080000, C438S066000, C438S073000
Reexamination Certificate
active
06452087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention particularly provides, in a photovoltaic device comprising a first electrode composed of zinc oxide, a photovoltaic device whose characteristics are improved, and a method of fabricating the same.
2. Description of Prior Art
Photovoltaic devices composed of an amorphous semiconductor such as amorphous silicon, amorphous silicon carbide, or amorphous silicon germanium are low in fabrication cost and can be easily increased in area. Accordingly, the photovoltaic devices have been developed as low-cost solar cells.
Referring to a cross-sectional view of
FIG. 18
, description is made of a photovoltaic element composed of an amorphous semiconductor. A photovoltaic element
10
composed of an amorphous semiconductor comprises a first electrode
2
, a photovoltaic conversion layer
3
composed of a lamination body of p-type, i-type, and n-type amorphous semiconductor layers
3
p,
3
i,
and
3
n,
and a second electrode
4
laminated in this order on a substrate
1
. When a translucent member such as glass or plastic is used as the substrate
1
, the first electrode
2
is composed of a translucent conductive material, and the second electrode
4
is composed of a highly reflective conductive material.
As the translucent conductive material composing the first electrode
2
, tin oxide (SnO
2
) has been conventionally used. However, it has been examined whether or not zinc oxide (ZnO) is used in order to achieve low cost in recent years, so that a photovoltaic element having high photovoltaic conversion characteristics has been obtained.
For example, a first electrode
2
composed of ZnO is formed by sputtering on a substrate
1
composed of glass, a photovoltaic conversion layer
3
composed of a lamination body of a p-type layer
3
p
having a thickness of approximately 150 Å composed of p-type amorphous silicon carbide, an i-type layer
3
i
having a thickness of approximately 4000 Å composed of i-type amorphous silicon, and an n-type layer
3
n
having a thickness of approximately 200 Å composed of n-type amorphous silicon is then formed by plasma CVD (Chemical Vapor Deposition), and a second electrode
4
composed of Ag is laminated using sputtering, thereby fabricating a photovoltaic element
10
.
As a result of changing the thickness of the first electrode
2
to various thicknesses to measure photovoltaic conversion efficiency, high photovoltaic conversion efficiency in excess of 10.5% is obtained in a case where the thickness of the first electrode
2
composed of ZnO is in the range of approximately 2100 Å to approximately 5000 Å, as shown in a characteristic view of FIG.
19
.
SUMMARY OF THE INVENTION
In a photovoltaic element using ZnO for a first electrode, however, high photovoltaic conversion efficiency is obtained, as described above. In the case of an integrated photovoltaic device, sufficient characteristics are not obtained.
The present invention has been made in order to solve such a conventional problem, and its object is to provide a photovoltaic device capable of obtaining superior photovoltaic conversion characteristics when ZnO is used for a first electrode and a method of fabricating the same.
A photovoltaic device according to the present invention is characterized by comprising a substrate; a plurality of first electrodes separated from one another by separating trenches on the substrate; a photovoltaic conversion layer provided on the substrate, including the first electrodes; and a plurality of second electrodes provided on the photovoltaic conversion layer and separated from one another by second separating trenches, and in that the thickness of a side end in the first electrode in the vicinity of the separating trench existing between the first electrode and the adjacent first electrode is larger than the thickness of an element region in the first electrode.
According to such construction, a portion irradiated with laser beams for forming the separating trench is formed to a thickness larger than the thickness of the element region. As a result, the first electrodes can be formed in a separated manner with a high yield, thereby making it possible to provide a photovoltaic device having high photovoltaic conversion characteristics.
The photovoltaic device is characterized in that the first electrode is composed of zinc oxide, is characterized in that the thickness of the side end in the first electrode is not less than 5000 Å, and is characterized in that the thickness of the element region in the first electrode is in the range of approximately 2100 Å to approximately 5000 Å.
Furthermore, the photovoltaic device is characterized in that a textured surface is formed in the element region in the first electrode, and is characterized in that the element region in the first electrode is made thinner than the side end in the step of forming the textured surface.
Alternatively, the photovoltaic device is characterized in that the thickness of the side end in the first electrode is larger than the thickness of the element region by forming a laser beam absorbing member.
As described in the foregoing, the thickness of the side end in the vicinity of the separating trench in the first electrode is made larger than the thickness of the element region by providing the laser beam absorbing member on the first electrode. As a result, the first electrodes can be formed in a separated manner with a high yield, thereby making it possible to provide a photovoltaic device having high photovoltaic conversion characteristics.
In addition thereto, the photovoltaic device is characterized in that the first electrode is divided into a plurality of parts by laser beam irradiation.
The present invention is directed to a photovoltaic device, characterized by comprising a substrate; an insulation thin film provided in a portion corresponding to an element region on the substrate; a plurality of first electrodes formed on the substrate, including the insulation thin film, and separated from one another by separating trenches; a photovoltaic conversion layer provided on the substrate, including the first electrodes; and a plurality of second electrodes provided on the photovoltaic conversion layer and separated from one another by second separating trenches, and in that the thickness of a side end in the first electrode in the vicinity of the separating trench existing between the first electrode and the adjacent first electrode is larger than the thickness of the element region in the first electrode.
According to such construction, the portion irradiated with the laser beams for forming the separating trench is formed to a thickness larger than the thickness of the element region. Further, it has a good film orientation. As a result, the first electrodes can be formed in a separated manner with a high yield, thereby making it possible to provide a photovoltaic device having high photovoltaic conversion characteristics.
The photovoltaic device is characterized in that the first electrode is composed of zinc oxide, and is characterized in that the insulation thin film is selected from silicon dioxide (SiO
2
), aluminum oxide (Al
2
O
3
), and titanium oxide (TiO
2
).
The photovoltaic device is characterized in that the element region in the first electrode is made thinner than the side end in the step of forming the textured surface.
A method of fabricating a photovoltaic device according to the present invention is a method of fabricating a photovoltaic device comprising on a substrate a plurality of photovoltaic elements each composed of a lamination body of a first electrode, a photovoltaic conversion layer, and a second electrode, characterized by comprising the steps of forming an electrode film on the substrate; thinning a region serving as an element region in the electrode film; irradiating laser beams into a separating region in the electrode film, and removing the electrode film in a portion irradiated with the laser beams, to form a plurality of f
Ishimaru Hiroshi
Ninomiya Kunimoto
Sasaki Manabu
Sayama Katsunobu
Yata Shigeo
Arent Fox Kintner & Plotkin & Kahn, PLLC
Diamond Alan
Sanyo Electric Co,. Ltd.
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