JPH1197724A - Solar cell and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the short-circuiting current of a solar cell by arranging an aluminum oxide film layer with a roughened surface between an aluminum substrate and a lower electrode. SOLUTION: An aluminum oxide(Al2 O3 ) film 2 is electrochemically an insulation film is formed on a substrate 1 by anode oxidation. An aluminum substrate 1 is subjected to anode oxidation in a nitric acid bath. When a porous covering (Al2 O3 ) is grown to a thickness of 2-6 μm on the surface of the substrate 1, surface 2a of the film 2 is made recessed and projected (roughened). A P-I-N junction type amorphous silicon film 3 is formed on the Al2 O3 film 2 with a recessed and projected surface as an amorphous silicon generation layer and then an ITO film 4 that becomes a transparent electrode is formed. A solar beam with a wavelength of 550-800 mm is diffused and reflected on the recessed and projected surface for confining light and the optical path length in the amorphous silicon is extended, thus increasing the short-circuiting current of a solar cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solar cell and a method for manufacturing the same, and more particularly, to an amorphous silicon solar cell with improved photoelectric conversion efficiency and a method for manufacturing the same.

[0002]

2. Description of the Related Art Amorphous silicon solar cells are known as low-cost solar cells that use clean, non-depleting energy that does not emit harmful substances. Such an amorphous silicon solar cell has the advantage that it can be manufactured at low cost because it can be composed of an inexpensive substrate and a thin film having a thickness of 1 μm or less that can be formed at a low temperature. In order to make full use of such features, it is necessary to improve the photoelectric conversion efficiency so that the performance can be put to practical use.

Conventionally, as a substrate material of such an amorphous silicon solar cell, a metal substrate such as stainless steel, an insulating substrate such as glass, polymer film, ceramic or the like, or an insulating substrate obtained by coating an insulating material on the surface of the metal substrate. Etc. are known. When using a structure in which an insulating film is coated on a metal substrate that can be reduced in weight and size unlike a glass substrate that cannot be made too thin, a heat-resistant resin film such as polyimide is generally used on a stainless steel substrate. Is done.

[0004] Conventionally, for example, S
When a stainless metal material such as US is used, an insulating film is interposed between the substrate and the lower electrode when a large-capacity solar cell is formed by connecting a plurality of cell elements in series. Need to be done. However, conventionally, an insulating film made of an organic material is often used as the insulating film, and the insulating film made of the organic material is
Because of its high thermal conductivity and poor heat resistance, it deteriorated the characteristics as a solar cell.

[0005] In addition, since it is necessary to process the surface of the base metal and reduce the film thickness, the manufacturing cost is also increased.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a solar cell having a thin metal substrate provided with a heat-resistant insulating portion and having a high photoelectric conversion efficiency and a method of manufacturing the same. That is.

[0007]

According to a first aspect of the present invention, there is provided a solar cell comprising a metal substrate, on which a lower electrode, an amorphous power generation layer and an upper electrode are sequentially disposed. The metal substrate is made of aluminum,
A solar cell in which a roughened aluminum oxide film layer is disposed between the aluminum substrate and the lower electrode, and a second aspect of the present invention is a solar cell including a lower electrode on a metal substrate,
In a method for manufacturing a solar cell in which an amorphous power generation layer and an upper electrode are sequentially disposed, a step of selecting aluminum as a metal substrate and a step of forming an aluminum oxide film layer having a roughened surface on the aluminum substrate surface Forming a lower electrode, an amorphous power generation layer, and an upper electrode sequentially on the roughened aluminum oxide film layer.

[0008]

In DETAILED DESCRIPTION OF THE INVENTION The present invention, since the aluminum substrate surface is oxidized by anodic oxidation, forming a coating layer surface was roughened becomes uneven by selecting the acid anodization step surface of the aluminum substrate can do. Sunlight having a wavelength of 550 to 800 mm is diffusely reflected on the uneven surface to confine the light, thereby increasing the path length in the amorphous silicon. As a result, the short-circuit current of the solar cell can be increased. Thereby, a solar cell with high photoelectric conversion efficiency can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a first example of the solar cell of the present invention.
It is a process sectional view for explaining the manufacturing method of an example.
As shown in FIG. 1A, first, the surface is polished by buffing or the like, and then chemically polished with a mixed solution of phosphoric acid and nitric acid to give mirror-like aluminum (A) having a thickness of about 0.2 mm.
1) An aluminum oxide (Al ₂ O ₃ ) film 2 which is an electrochemically insulating film is formed on a substrate 1 by anodic oxidation.
This anodic oxidation is performed on the aluminum substrate 1 in a nitric acid bath, and a porous film (Al ₂ O ₃ )
The surface 2a of the film 2 is grown to a thickness of 6 μm.
Are in an uneven state (roughened).

Next, as shown in FIG.
a on the Al ₂ O ₃ film 2 having a
5550 ° C. at a temperature of about 250 ° C. (P layer: 4
00Å, I layer: 5000Å, N layer: 150Å) to form a P-I-N junction type amorphous silicon film 3 to form an amorphous silicon power generation layer. An ITO film 4 serving as a transparent electrode having a thickness of 1000 ° is formed at 300 ° C. Light is incident from this transparent electrode (arrow L).

In the solar cell in which the amorphous power generation layer 3 and the transparent electrode 4 are sequentially disposed on the metal substrate 1 by the above steps, the metal substrate 1 is made of aluminum and has the uneven surface 2a on the aluminum substrate 1. A solar cell having the aluminum oxide film 2 can be obtained at low cost. Although not shown, a metal film may be formed between the Al ₂ O ₃ film 2 and the amorphous silicon film 3 to obtain ohmic contact with the amorphous silicon film 3. The material can be titanium, molybdenum, nickel, chromium, and the like.

FIG. 2 shows a second embodiment of the solar cell according to the present invention.
FIG. The solar cell shown in FIG.
Physically or in advance on the surface of the aluminum substrate 11 of the example.
Is the same as that of the first embodiment after chemically forming the uneven surface 11a.
Similarly, the Al of the anodic oxide film_TwoO _ThreeFilm 2, amorphous silicon
A structure in which a capacitor film 3 and an ITO film 4 of a transparent electrode are sequentially formed;
Has become.

In this second embodiment, the anodic oxide film Al_TwoO
_ThreeThe underlying aluminum surface forming the uneven surface 2a of the film 2 is
Since the uneven surface 11a is provided in advance, the first embodiment is different from the first embodiment.
Even rougher Al_TwoO_ThreeFilm 2 is obtained
Light is confined within the recon power generation layer and has a high photoelectric conversion efficiency.
A positive battery can be obtained. In the above embodiment, the transparent electrode
Although ITO was used as No. 4, transparency to visible light and
Materials having excellent electrical conductivity, such as SnO
_TwoFilm and In_TwoO _ThreeA membrane or the like can also be used.

In the above embodiment, the amorphous silicon film 3
Discloses that a hydrogenated amorphous silicon film is formed by a plasma CVD method so that hydrogen is taken into an amorphous silicon Si film. The p-layer and the n-layer of the hydrogenated amorphous silicon film are formed by adding B ₂ to SiH ₄ gas, respectively.
Impurity addition (doping) of H ₆ gas and PH ₃ gas
The I layer was formed by glow discharge decomposition of only SiH ₄ gas.

Further, in this embodiment, a PIN junction type hydrogenated amorphous silicon laminated film is used.
A fluorinated amorphous silicon film in which fluorine F having a stronger bonding force with i is incorporated into the amorphous silicon film is also possible. Although not implemented in the present embodiment, by forming an insulating film such as SiN _X between the transparent electrode 4 and the amorphous silicon photovoltaic layer 3, to obtain an amorphous silicon photovoltaic layer having a more chemically stable flatness be able to. However, in that case, the insulating film must be excellent in light transmission in order to correspond to the transparent electrode 4.

[0016]

As described above, according to the present invention,
An amorphous silicon solar cell with high photoelectric conversion efficiency in which a high heat-resistant insulating film is formed on a metal substrate at low cost can be obtained.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view showing a manufacturing process of a first embodiment of a solar cell of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the solar cell of the present invention.

[Explanation of symbols]

1, 11: aluminum substrate 2: Al ₂ O ₃ film (anodic oxide film) 2a: uneven surface (Al ₂ O ₃ film) 3: amorphous silicon film (power generation layer) 4: ITO film (transparent electrode) 11a: uneven surface (Aluminum substrate)

Claims (4)

[Claims] 1. A solar cell in which a lower electrode, an amorphous power generation layer, and an upper electrode are sequentially disposed on a metal substrate, wherein the metal substrate is made of aluminum, and a rough surface is provided between the aluminum substrate and the lower electrode. A solar cell, wherein a converted aluminum oxide film layer is disposed. 2. A method for manufacturing a solar cell in which a lower electrode, an amorphous power generation layer, and an upper electrode are sequentially disposed on a metal substrate, wherein aluminum is selected as the metal substrate, and the surface of the aluminum substrate is roughened. Forming an aluminum oxide film layer having a roughened surface, and sequentially forming a lower electrode, an amorphous power generation layer and an upper electrode on the roughened aluminum oxide film layer. Solar cell manufacturing method. 3. The method according to claim 2, wherein the step of forming a roughened aluminum oxide film on the surface of the aluminum substrate is a step of anodizing the surface of the aluminum substrate. . 4. A step of selecting aluminum as the metal substrate, a step of roughening the surface of the aluminum substrate,
Performing anodization on the surface of the roughened aluminum substrate to form a roughened aluminum oxide film layer, a lower electrode, an amorphous power generation layer, and an upper electrode on the roughened aluminum oxide film layer; Forming a top electrode sequentially.