JPH04218977A - Photovoltaic device and fabrication thereof - Google Patents

Abstract

PURPOSE:To provide a photovoltaic device and a method of fabrication thereof improved in photoelectric conversion efficiency by effectively confining light in a semiconductor film. CONSTITUTION:A photoelectric device is formed on a substrate 1 so as to cover a uneven semi-continuous metal layer 2a. The device includes a substantially uniform thickness reflective continuous metal layer 2b, a photoelectric conversion semiconductor film 3 formed on the continuous metal layer 2b, and a transparent electrode 4 formed on the semiconductor film 3.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to photovoltaic devices, and more particularly to improving the photovoltaic conversion efficiency of photovoltaic devices including thin films of amorphous semiconductors.

0002

[Industrial Application Field] Photovoltaic devices are required to reduce their cost and improve their photoelectric conversion efficiency. A photovoltaic device including an amorphous semiconductor film has a higher light absorption than a photovoltaic device including a crystalline semiconductor layer, and therefore can be formed thinner. Furthermore, the amorphous photovoltaic device has advantages such as a simple manufacturing process and a low manufacturing temperature, so that energy can be saved during manufacturing. Furthermore, amorphous photovoltaic devices can use inexpensive materials such as glass, stainless steel, and ceramics as substrate materials.
It is easy to reduce costs.

However, when glass, stainless steel, ceramic, or the like is used as a substrate material, the light reflectance of the surface of these materials is generally low. Therefore, in order to improve photoelectric conversion efficiency, the reflectance of the substrate surface is increased by forming a smooth reflective layer on the substrate using one or more types of metals with high reflectance. . The photoelectric conversion efficiency is improved by reflecting incident light that has passed through the semiconductor film of the photovoltaic device without being absorbed by the substrate surface, and causing the semiconductor film to absorb the reflected light as well.

However, when the light that has passed through the semiconductor film is specularly reflected on the substrate surface and enters the semiconductor film again, "interference" may occur between the incident light and the reflected light, resulting in the appearance of interference fringes. Interference fringes are a phenomenon in which light waves weaken or strengthen each other. Therefore, depending on the thickness of the semiconductor film and the wavelength of the incident light, the intensities of the incident light and the reflected light cancel each other out and weaken each other. This is equivalent to a relative decrease in the amount of light, leading to a decrease in photoelectric conversion efficiency.

Referring to FIG. 15, there is shown a well-known conceptual cross-sectional view of a photovoltaic device that is expected to improve photovoltaic conversion efficiency by reducing light interference as described above. . In this photovoltaic device, a reflective metal layer 2 having an uneven surface is formed on a substrate 1. This metal layer 2 acts as a back electrode. An amorphous semiconductor film 3 serving as a photoelectric conversion layer is formed on the back electrode 2, and the semiconductor film 3 is covered with a transparent front electrode 4.

When a light ray L0 is incident on such a photovoltaic device, if the incident light ray L0 is not absorbed within the semiconductor film 3 and reaches the back metal electrode 2, the incident light ray L0 will be absorbed by the unevenness of the metal electrode 2. It is scattered and reflected by the surface. If the scattered and reflected light L1 is not absorbed within the semiconductor film 2 and returns to the interface between the semiconductor film 3 and the transparent electrode 4, the scattered and reflected light L1 forms a relatively large angle with respect to the normal to the interface. Therefore, the light L1 tends to become the light L2 reflected back into the semiconductor film 3 at the interface. That is, once the incident light enters the semiconductor film 3, the light tends to be confined within the semiconductor film 3. This is often referred to as "optical confinement technology."

As a result, in the photovoltaic device as shown in FIG. 15, interference between the light reflected from the back metal electrode 2 and the incident light is reduced. Furthermore, since the optical path length of the light scattered and reflected from the back metal electrode 2 becomes longer in the semiconductor film, the reflected light is efficiently absorbed within the semiconductor film and contributes to photoelectric conversion.

In one prior art attempt to form a back metal electrode with a textured surface, a film of silver approximately 1000 Å thick was deposited by electron beam evaporation at approximately 260° C. on a substrate; It is baked in a vacuum to create a textured surface. In another prior art attempt, a silver film about 1000 Å thick was deposited by sputtering on a substrate at about 200°C, and about 6
Baked at 00°C.

However, it is difficult to form sufficient unevenness for "light confinement" on the surface of the back metal electrode using baking. Furthermore, baking at a high temperature such as 600° C. may have an adverse effect on the substrate.

In view of the problems of the prior art, an object of the present invention is to provide a photovoltaic device including a back metal electrode that can sufficiently scatter and reflect incident light, and a method for manufacturing the same. Another object of the present invention is to provide a photovoltaic device with improved photoelectric conversion efficiency and a method for manufacturing the same.

[0011]

According to a first aspect of the invention, a photovoltaic device includes a substrate, a semi-continuous metal layer formed on the substrate and having a non-uniform rough surface. , a reflective continuous metal layer formed over the semi-continuous metal layer and having a substantially uniform thickness, a semiconductor film formed on the continuous metal layer, and a semiconductor film formed on the semiconductor film. and a transparent electrode formed on the surface.

According to a second aspect of the invention, a method for manufacturing a photovoltaic device includes forming a semi-continuous metal layer having a non-uniform uneven surface on a substrate at a relatively high temperature; depositing at a relatively low temperature a reflective, continuous metal layer having a substantially uniform thickness overlying the metal layer;
The method includes the steps of depositing a semiconductor film for photoelectric conversion so as to cover the continuous metal layer, and depositing a transparent electrode on the semiconductor film.

According to a third aspect of the invention, a photovoltaic device includes a substrate, a continuous metal film formed on the substrate and having a reflective surface, and a continuous metal film covering the continuous metal film. a transparent conductive layer formed on the transparent conductive layer, an island-shaped reflective metal layer formed on the transparent conductive layer, and a semiconductor film for photoelectric conversion formed to cover the island-shaped metal layer; , and a transparent electrode formed on the semiconductor film.

[0014]

In the photovoltaic device according to the first aspect of the invention, the semi-continuous metal layer has a non-uniform uneven surface and the reflective continuous metal layer has a substantially uniform thickness. Therefore, the surface of the continuous metal layer inherits the irregularities of the surface of the semi-continuous metal layer. Therefore, the incident light that has passed through the semiconductor film is scattered and reflected by the uneven surface of the continuous metal layer and is effectively confined within the semiconductor film. That is, not only incident light but also reflected light is efficiently used for photoelectric conversion in the semiconductor film, improving the photovoltaic device's photoelectric conversion efficiency.

In the method of manufacturing a photovoltaic device according to the second aspect of the invention, the semi-continuous metal layer is deposited on the substrate at a relatively high temperature, so that the surface of the semi-continuous metal layer is non-uniform. It can have sufficient unevenness. And since the reflective continuous metal layer is deposited on the semi-continuous metal layer at a relatively low temperature, the continuous metal layer has a uniform thickness and its surface is below the surface of the semi-continuous metal layer. It can take over the unevenness.

In the photovoltaic device according to the third aspect of the present invention, the incident light that has passed through the semiconductor film is scattered and reflected by the island-shaped metal layer, and the incident light that has passed through the opening of the island-shaped metal layer is It is reflected by the continuous metal film towards the semiconductor film. Therefore, the incident light and reflected light are efficiently used for photoelectric conversion in the semiconductor film, improving the photoelectric conversion efficiency of the photovoltaic device.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a photovoltaic device according to a first embodiment of the present invention is shown in a conceptual cross-sectional view. In this photovoltaic device, a semi-continuous first metal layer 2a having a finely uneven surface is formed on a substrate 1 made of glass, stainless steel, ceramic, or the like. The semi-continuous metal layer 2a having an uneven surface is covered with a reflective continuous second metal layer 2b having a substantially uniform thickness. The first and second metal layers 2a, 2b act as back electrodes. On the continuous second metal layer 2b are Si, S for photoelectric conversion.
An amorphous semiconductor thin film 3 such as iGe or CdS is formed. A transparent front electrode 4 is formed on the semiconductor thin film 3.

A photovoltaic device as shown in FIG. 1 can be formed, for example, as follows. As the substrate 1, a plate of stainless steel SUS304 whose surface has been polished can be used. Further, the semi-continuous first metal layer 2a and the continuous second metal layer 2b can be formed using highly reflective silver.

The semi-continuous first silver layer 2a having an uneven surface is formed to a thickness ranging from 250 Å to 800 Å by electron beam evaporation or sputtering at a growth rate of about 10 Å/sec on the substrate 1 maintained at a temperature of 300° C. or higher. may be formed by depositing to a thickness within the range. The temperature of the board is 300℃
In the following cases, a semi-continuous first silver layer 2a having a sufficiently uneven surface cannot be formed. Although a higher substrate temperature is preferred to promote local agglomeration and obtain a sufficiently rough surface, the substrate 1 will be adversely affected if the substrate temperature is too high. Therefore, the semi-continuous first silver layer 2a having a sufficiently uneven surface
A more preferable substrate temperature range for forming is 300~
The temperature is 450°C. If the first silver layer 2a is thinner than 250 Å or thicker than 800 Å, sufficient unevenness due to aggregation cannot be obtained on the surface of the first metal layer 2a. 1st
In order to obtain sufficient unevenness on the surface of the silver layer 2a, a more preferable thickness of the first silver layer 2a is in the range of 250 to 600 Å.

A continuous second silver layer 2b having a substantially uniform thickness is formed by electron beam evaporation or sputtering to cover the semi-continuous first silver layer 2a at a substrate temperature of 260° C. or less. It can be formed by depositing to a thickness of 300 Å or more at a growth rate of seconds. Since the continuous second silver layer 2b has a substantially uniform thickness, the continuous second silver layer 2b has a substantially uniform thickness.
The upper surface of the silver layer 2b also has unevenness similar to the unevenness on the surface of the discontinuous first silver layer 2a. When the second silver layer 2b is thinner than 300 Å, it is difficult for the second silver layer 2 to become a completely continuous film. However, the second silver layer 2b does not need to be very thick,
If the thickness is too high by 700 Å, the unevenness of the surface tends to become smaller. Therefore, the most preferable thickness range of the second silver layer 2b is 350 to 500 Å. In order to avoid agglomeration and form a continuous second silver layer 2b as thin as possible, it is preferable that the substrate temperature be low. However, if the substrate temperature is too low, the bonding properties between the semi-continuous first silver layer 2a and the continuous second silver layer 2b will deteriorate. Therefore, it is preferable that the substrate temperature during formation of the continuous second silver layer 2b is 100 to 260°C.

Referring to FIG. 2, there is shown a SEM (scanning electron microscope) photograph of a semi-continuous first silver layer 2a deposited to a thickness of 200 Å on a stainless steel substrate 1 at 350°C. This SEM photograph was taken from a direction forming an angle of 45 degrees from the surface of the substrate 1. The semi-continuous silver layer 2a contains locally aggregated areas in the form of islands or peninsulas appearing white and covers approximately 50% of the substrate surface. The short white horizontal bar at the bottom of the photo represents a length of 1.0 μm.

Referring to the graph of FIG. 3(A), thickness 2
Stainless steel substrate 1 including a semi-continuous first silver layer 2a with a thickness of 00 Å
The light reflectance is shown. In this graph, the horizontal axis represents the wavelength (nm) of the incident light, and the vertical axis represents the light reflectance (%).
). A dashed-dotted curve R represents specular reflection (reflection in which the incident angle of light with respect to the substrate surface is equal to the reflection angle). On the other hand, the solid curve TR represents total reflection (including not only specular reflection but also scattered reflection). Figure 3 (
In the graph of B), the horizontal axis represents the wavelength (nm) of the incident light, and the vertical axis represents the ratio of scattered reflection to total reflection (TR-
R)/TR (%). Figure 3 (A) and (B)
), it can be seen that the total reflection T on the substrate surface in Figure 2 is
It can be seen that both R and scattered reflection (TR-R)/TR are insufficient.

Referring to FIG. 4, a SEM photograph of a semi-continuous first silver layer 2a deposited to a thickness of 500 Å on a stainless steel substrate 1 at 350° C. is shown.
Local aggregation has progressed in the silver layer 2a, and the first silver layer 2a in FIG. 4 has a rougher structure than that in FIG. 2.

The graph of FIG. 5A shows the light reflectance of the substrate of FIG. 4, which includes a semi-continuous first silver layer 2a having a thickness of 500 Å. In FIG. 5(A), it can be seen that the total reflection TR is increased compared to FIG. 3(A). This increase in total reflection TR is mainly caused by scattered reflection (TR-R).
It can be seen from FIG. 5(B) that this is due to an increase in /TR.

Referring to FIG. 6, a SEM photograph of a silver layer deposited to a thickness of 1000 Å on a stainless steel substrate 1 at 350° C. is shown. Although the silver layer in FIG. 6 has irregularities on its surface, it is a substantially continuous layer. That is, this silver layer completely covers the surface of the stainless steel substrate.

The graph in FIG. 7(A) shows the thickness of 1000 Å.
7 shows the light reflectance of the substrate of FIG. 6 containing a silver layer of . In Figure 7 (A), compared to Figure 5 (A), the total reflection T
It can be seen from a comparison between FIG. 7(B) and FIG. 5(B) that although R has increased, scattered reflection (TR-R)/TR has decreased.

Therefore, in the photovoltaic device according to the first embodiment of the present invention, total reflection is achieved while maintaining a satisfactory scattered reflection (TR-R)/TR as shown in FIG. 5(B). In order to increase the TR, a continuous second silver layer 2b having a substantially uniform thickness is deposited on the semi-continuous first silver layer 2a having irregularities on its surface.

In Table 1, various photovoltaic conversion characteristics of a photovoltaic device A according to a first embodiment of the invention are shown in comparison with a photovoltaic device B according to the prior art. The photovoltaic device A is mounted on a stainless steel substrate 1 at a temperature of 500 Å at 350°C.
a semi-continuous first silver layer 2a deposited to a thickness and a
a continuous second silver layer 2b deposited to a substantially uniform 500 Å thickness at 50° C. and amorphous SiGe deposited thereon;
It includes a membrane 3. The amorphous SiGe film includes a p-i-n junction, and the i-layer thickness is about 2500 Å. On the other hand, photovoltaic device B according to the prior art has 35
It includes a single continuous silver layer deposited to a thickness of 1000 Å at 0° C. and an amorphous SiGe film deposited thereon.

[0029]

[Table 1]

As is clear from Table 1, the photovoltaic device A of the first embodiment has short-circuit current IS C and fill factor F, which are photoelectric conversion characteristics other than open-circuit voltage VOC.
It is superior to the prior art photovoltaic device B in both F and conversion efficiency η, especially photovoltaic conversion efficiency η of 18%.
It can be seen that this has also been improved.

In the first embodiment described above, the first and second silver layers 2a and 2b are directly deposited on the polished surface of the stainless steel substrate 1.
However, a titanium layer may be formed on the substrate 1 by electron beam evaporation or sputtering, and silver reflective layers 2a and 2b may be formed thereon. This is because such a titanium layer has a stainless steel substrate 1 and a silver reflective layer 2.
This is because it improves the adhesion between a and 2b.

Further, in the first embodiment described above, the SiGe semiconductor film 3 is formed directly on the continuous second silver layer 2b, but a transparent ZnO conductive layer is formed between the reflective layer 2b and the semiconductor film 3. may be formed. This is because the ZnO layer enhances the effect of confining light within the semiconductor film 3 due to its refractive index. Preferably, the ZnO layer is formed to a thickness of 500 to 2500 Å. This is because if the ZnO layer is too thin, it will be difficult to form a uniform film, and conversely, even if the ZnO layer is made thicker than 2500 Å, the photoelectric conversion efficiency will not further increase. A more preferable thickness range of the ZnO layer is 7
00 to 1500 Å.

FIG. 8 shows the influence of the thickness of the first silver layer 2a on various photoelectric conversion characteristics. In this graph, the horizontal axis represents the thickness (Å) of the first silver layer, and the vertical axis represents photoelectric conversion characteristics such as short circuit current ISC, open circuit voltage VOC, fill factor FF, and maximum output Pmax. It represents. The photovoltaic device shown in FIG.
a titanium layer deposited to a thickness of 500 Å at a growth rate of Å/sec; a first silver layer formed on the titanium layer at 350° C. and having a thickness expressed in coordinates on the horizontal axis; 1
Includes a 500 Å thick second silver layer formed at 50°C. However, the point Ref on the horizontal axis represents a prior art photovoltaic device, which consists of a 500 Å thick titanium layer formed on a stainless steel substrate and a titanium layer formed at 350°C on top of the titanium layer. It contains a single silver layer of 1000 Å thick. The various photovoltaic conversion characteristics on the vertical axis are shown normalized by the characteristics of this prior art photovoltaic device. 8th
As can be seen from the graph in the figure, the thickness of the first silver layer is preferably in the range of about 250-600 Å.

FIG. 9 is similar to FIG. 8, but the horizontal axis in FIG. 9 represents the thickness of the second silver layer, and the thickness of the first silver layer is set at a constant 350 Å. ing. As can be seen from FIG. 9, the second silver layer preferably has a thickness of about 300 Å or more. However, the thickness of the second silver layer was reduced to 500 Å.
Since the photoelectric conversion characteristics will not be further improved even if the thickness is increased beyond 35 mm, the more preferable thickness range of the second silver layer is
It is 0 to 500 Å.

The photovoltaic device illustrated in the graph of FIG. 10 includes a first silver layer 350 Å thick, a second silver layer 500 Å thick, and a second silver layer deposited on the second silver layer. It contains a ZnO layer. The horizontal axis in FIG. 10 represents the thickness (Å) of this ZnO layer. Various photoelectric conversion characteristics on the vertical axis are normalized by the characteristics of a photovoltaic device that does not include a ZnO layer. As understood from this graph, Z
The thickness of the nO layer is preferably in the range of 500-2500 Å, more preferably in the range of 700-1500 Å.

Referring to FIG. 11, a photovoltaic device according to a second embodiment of the present invention is shown in a conceptual cross-sectional view. In this photovoltaic device, a continuous, reflective first metal layer 2 is formed so as to completely cover the upper surface of the substrate 1 . The first metal layer 2 is covered with a transparent conductive layer 5. On the transparent conductive layer 5, an island-shaped reflective second metal layer is formed. This island-shaped second metal layer preferably covers 30 to 70% of the upper surface of the transparent conductive layer 5. The first metal layer 2, the transparent conductive layer 5 and the second metal layer 6 act as a back electrode. An amorphous semiconductor film 3 for photoelectric conversion is formed to cover the island-shaped second metal layer 6 and the transparent conductive layer 5. A transparent front electrode 4 is formed on the amorphous semiconductor film 3.

When light enters the photovoltaic device as shown in FIG. 11, a portion of the light transmitted through the semiconductor film 3 is scattered and reflected by the island-shaped second metal layer 6. Second metal layer 6
Light that passes between the islands in the transparent conductive layer 5 or is redirected by the islands is reflected by the continuous first metal layer 2 and passes again between the islands in the second metal layer 6 or The direction is changed by these islands and returned into the semiconductor film 3. Therefore, the light incident on the photovoltaic device tends to be confined within the semiconductor film 3,
Photoelectric conversion efficiency is improved.

Referring to FIG. 12, a more specific example of a photovoltaic device according to the second embodiment is shown in a sectional view. A titanium layer 7 is formed on the stainless steel substrate 1 by electron beam evaporation to a thickness of about 500 Å. On the titanium layer 7 a continuous first silver layer 2 is deposited by vapor deposition at 350° C. to a thickness of 1000 Å. On the first silver layer 2,
A transparent ZnO conductive layer 5 with a thickness of 1000 Å is formed,
A second island-shaped silver layer 6 with a thickness of 200 Å is deposited thereon by vapor deposition. This island-shaped second silver layer 6 is a transparent conductive layer 5.
covers about 50% of the surface.

Thereafter, an n-type amorphous Si layer 3n, an i-type amorphous Si layer 3i, and an amorphous SiC p- i interface layer 3pi
and p-type amorphous SiC layer 3p are sequentially deposited by plasma CVD. Finally, a transparent front electrode 4 is formed on the p-type amorphous SiC layer 3p.

Referring to FIG. 13, a plasma CVD apparatus for depositing an amorphous semiconductor layer is conceptually illustrated. This plasma CVD apparatus includes an introduction chamber 11,
gate valve 12, reaction chamber 13 for forming an n-type semiconductor layer,
It includes a reaction chamber 14 for forming an i-type semiconductor layer, a reaction chamber 15 for forming a p-type semiconductor layer, and an extraction chamber 16. Within each of the reaction chambers 13 to 15,
A cathode 18 is provided. Cylinder 19 to 23 are
Each contains SiH4, H2, CH4, PH3, and B2H6. The plasma CVD apparatus further includes a high frequency power source 24, and a semiconductor layer is deposited on the substrate 1. Amorphous semiconductor layers 3n, 3i in the photovoltaic device shown in FIG.
, 3pi, and 3p can be formed using the CVD apparatus shown in FIG. 13 under the gas flow rates shown in Table 2.

[0041]

[Table 2] Unit (sccm)

The photovoltaic device of FIG. 12 has a short circuit current of approximately 1
showed an improvement of 0%. The electromotive force device for comparison is similar to that shown in FIG. 12, but does not include the transparent conductive layer 5 and the island-shaped second silver layer 6 thereon.

In the above second embodiment, when the continuous first silver layer 2 is formed of the semi-continuous silver layer 2a and the continuous silver layer 2b of FIG. 1, the short circuit current is further improved.

Referring to FIG. 14, a tandem photovoltaic device including a stacked three-layer photovoltaic cell according to a third embodiment of the present invention is shown in a schematic cross-sectional view. . Since the absorption coefficient of long wavelength light in a semiconductor film is generally small, a tandem type photovoltaic device is preferable when long wavelength light is to be used more efficiently. Furthermore, in order to efficiently utilize long wavelength light, it is preferable to use an amorphous SiGe i-layer having an energy bandgap smaller than 1.75 eV, which is the energy bandgap of amorphous silicon. The photovoltaic cell comprising this amorphous SiGe i-layer is preferably placed below the tandem photovoltaic device. In the tandem photovoltaic device shown in FIG. 14, a titanium layer 7 with a thickness of 500 Å and a titanium layer 7 with a thickness of 10
00 Å continuous first silver layer 2, 1000 Å thick transparent Z
An nO conductive layer 5 and an island-shaped second silver layer 6 having a thickness of 200 Å are successively deposited.

On the island-shaped second silver layer 6 and the transparent conductive layer 5 are an n-type amorphous Si layer 3n, an i-type amorphous SiGe layer 3ia, and an amorphous SiC p-i interface layer. 3pi and p-type amorphous SiC layer 3p is deposited, thereby forming the first
A photovoltaic cell of layers is formed.

On the first layer photovoltaic cell, there are also an n-type amorphous Si layer 8n, an i-type amorphous Si layer 8i, an amorphous SiC p-i interface layer 8pi, and a p-i interface layer 8pi. type of amorphous SiC
Layers 8p are deposited in sequence, thereby forming a second layer of photovoltaic cells.

[0047] Further, on the second layer photovoltaic cell, n
type amorphous Si layer 9n, i-type amorphous SiC layer 9i, amorphous SiC p-i interface layer 9pi, and p-type amorphous S
iC layers 9p are sequentially deposited, thereby forming a third layer of photovoltaic cells. Finally, a transparent front electrode 4 is formed on the third layer of photovoltaic cells.

The tandem photovoltaic device of FIG. 14 showed an approximately 20% improvement in short circuit current over the prior art comparative tandem photovoltaic device. The tandem photovoltaic device for comparison is similar to that shown in FIG. 14, but does not include the transparent conductive layer 5 and the island-shaped second silver layer 6 thereon.

Also in the tandem photovoltaic device of the third embodiment, the continuous first silver layer 2 is replaced with the semi-continuous silver layer 2a in FIG.
When formed with a continuous silver layer 2b, the short circuit current is further improved.

[0050]Although silver was used as the reflective metal in the various examples above, aluminum,
It will be understood that copper, gold, etc. may also be used. Also,
As the semiconductor layer, not only an amorphous semiconductor layer but also a polycrystalline semiconductor layer or a single crystal semiconductor layer can be used. Furthermore, as the semiconductor, not only Si, SiGe, and SiC but also various other compound semiconductors can be used. Furthermore, as the material of the substrate, not only stainless steel but also various other materials such as glass can be used.

[0051]

As described above, according to the present invention, it is possible to provide a photovoltaic device with improved photoelectric conversion efficiency by efficiently confining light within a semiconductor film, and a method for manufacturing the same. .

[Brief explanation of the drawing]

FIG. 1 is a conceptual cross-sectional view of a photovoltaic device according to a first embodiment of the present invention.

[Figure 2] 200 Å onto a stainless steel substrate at 350°C
1 is a SEM photograph showing the metallographic structure of a silver layer deposited to a thickness of .

FIG. 3 is a graph showing the light reflection characteristics of the substrate of FIG. 2;

[Figure 4] 500 Å onto a stainless steel substrate at 350°C
SE showing the metallography of a semi-continuous silver layer deposited to a thickness of
This is an M photo.

FIG. 5 is a graph showing the light reflection characteristics of the substrate of FIG. 4;

[Figure 6] 1000 nm onto a stainless steel substrate at 350°C
SE showing the metallography of a continuous silver layer deposited to a thickness of Å
This is an M photo.

FIG. 7 is a graph showing the reflection characteristics of the substrate of FIG. 6;

FIG. 8 is a graph showing the influence of the thickness of the first silver layer on photoelectric conversion characteristics in the first example.

FIG. 9 is a graph showing the influence of the thickness of the second silver layer on photoelectric conversion characteristics in the first example.

FIG. 10 is a graph showing the influence of the thickness of the ZnO layer on photoelectric conversion characteristics in the first example.

FIG. 11 is a conceptual cross-sectional view showing a photovoltaic device according to a second embodiment of the present invention.

FIG. 12 is a sectional view showing a more specific example of a photovoltaic device according to the second embodiment.

FIG. 13: Plasma C for depositing an amorphous semiconductor layer
It is a conceptual diagram showing a VD device.

FIG. 14 is a schematic cross-sectional view showing a tandem photovoltaic device according to a third embodiment of the present invention.

FIG. 15 is a conceptual diagram for explaining "light confinement" within a semiconductor film of a photovoltaic device.

[Explanation of symbols]

1 is a substrate, 2 is a metal film, 2a is a semi-continuous metal layer with an uneven surface, 2b is a continuous metal layer with a uniform thickness, 3
4 represents a semiconductor film, 4 represents a transparent front electrode, 5 represents a transparent ZnO layer, 6 represents an island-shaped metal layer, and 7 represents a titanium layer. In each figure, the same reference numerals indicate the same contents or corresponding parts.

Claims (3)

[Claims] 1. A substrate, a semi-continuous metal layer formed on the substrate and having a non-uniform uneven surface, and a semi-continuous metal layer formed over the semi-continuous metal layer and having a substantially uniform thickness. 1. A light source comprising: a reflective continuous metal layer having a reflective surface; a semiconductor layer for photoelectric conversion formed on the continuous metal layer; and a transparent electrode formed on the semiconductor layer. Electromotive force device. 2. Depositing a semi-continuous metal layer with a non-uniform rough surface on a substrate at a relatively high temperature and a reflective continuous metal layer having a substantially uniform thickness at a relatively low temperature. depositing a semiconductor layer for photoelectric conversion so as to cover the semi-continuous metal layer, depositing a semiconductor layer for photoelectric conversion so as to cover the continuous metal layer, and depositing a transparent electrode on the semiconductor layer. A method for manufacturing a photovoltaic device. 3. A substrate, a continuous metal layer formed on the substrate and having a reflective surface, a transparent conductive layer formed over the continuous metal layer, and the transparent conductive layer. an island-shaped reflective metal layer formed above, a semiconductor layer for photoelectric conversion formed so as to cover the island-shaped metal layer and the transparent conductive layer, and a semiconductor layer formed on the semiconductor layer. A photovoltaic device comprising a transparent electrode.