JP3172365B2 - Photovoltaic device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device for converting light energy such as sunlight into electric energy and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, various types of photovoltaic devices for converting light energy such as sunlight into electric energy have been known. One of such photovoltaic devices is shown in FIG. As shown in FIG.
And the like, and a light-transmitting conductive film 2 such as
For example, one conductivity type semiconductor layer 3a (or 3c) composed of a p-type (or n-type) semiconductor, a photovoltaic layer 3b composed of an i-type semiconductor, and another conductive layer composed of an n-type (or p-type) semiconductor It is known that a photoelectric conversion layer 3 on which a mold semiconductor layer 3c (or 3a) is laminated is provided, and a back electrode 4 made of a highly reflective metal such as Ag is provided on the photoelectric conversion layer 3. .

In such a photovoltaic device, light is guided from the light-transmitting substrate 1 side to the photoelectric conversion layer 3 through the light-transmitting conductive film 2, and the carrier is generated in the photovoltaic layer 3b. Are generated to perform photoelectric conversion.

In recent years, in a photovoltaic device as described above, as shown in FIG.
The interface between the light-transmitting conductive film 2 and the photoelectric conversion layer 3 is textured to form an uneven shape so that light is guided to the photoelectric conversion layer 3 through the light-transmitting conductive film 2. In addition to suppressing the reflection of light at the interface with, the light guided to the photoelectric conversion layer 3 is scattered so that the optical path length of light passing through the photoelectric conversion layer 3 is increased. Was.

Here, when the interface between the light-transmitting conductive film 2 and the photoelectric conversion layer 3 is made uneven as in the photovoltaic device shown in FIG. 2, the light-transmitting conductive film 2 and the photoelectric conversion layer 3 The optical path length of light passing through the photovoltaic layer 3b of the photoelectric conversion layer 3 is longer than that of the photovoltaic device of FIG. The current has increased.

However, when the interface at which the light-transmitting conductive film 2 and the photoelectric conversion layer 3 come into contact with each other has an uneven shape, the fill factor F.F. F. And the conversion efficiency cannot be sufficiently improved.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in a photovoltaic device, and an uneven interface between a light transmitting conductive film and a photoelectric conversion layer is provided. Even when the photovoltaic device is formed, the fill factor is not reduced, and a photovoltaic device with good conversion efficiency can be obtained, and such a photovoltaic device can be easily and reliably manufactured. The purpose is to do so.

Here, the present inventors have found that the fill factor is reduced when the interface where the translucent conductive film 2 and the photoelectric conversion layer 3 come into contact with each other is made uneven as in the photovoltaic device shown in FIG. The cause was studied.

As a result, when the interface where the translucent conductive film 2 and the photoelectric conversion layer 3 are in contact with each other is formed in an uneven shape as described above,
As a result, the internal electric field in the photoelectric conversion layer 3 becomes non-uniform in the surface direction of the layer surface. It was found that the internal electric field of the photovoltaic device 3 was weakened, and the fill factor in this photovoltaic device was reduced.

The present inventors conducted further research on the basis of the above research results and found that the transparent conductive film 2 and the photoelectric conversion layer 3
When the internal electric field in the photoelectric conversion layer 3 becomes non-uniform in the plane direction of the layer surface, for example, due to an uneven interface at the interface with which the contact is made, this is corrected to suppress a decrease in the fill factor,
Means for improving the conversion efficiency of the photovoltaic device has been developed, and the present invention has been completed.

[0011]

First, in the present invention, in order to solve the above-mentioned problems, in a photovoltaic device in which a photovoltaic layer is provided in a photoelectric conversion layer, an internal electric field in the photoelectric conversion layer is provided. Is non-uniform in the plane direction of the layer surface, the thickness of the photovoltaic layer at the portion where the internal electric field is weak is made thinner than at other portions.

Further, according to the present invention, there is provided a photovoltaic device in which an interface between a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film has an uneven shape. The thickness of the photovoltaic layer at the portion in contact with the recess was made thinner than at the other portions.

Further, in the photovoltaic device in which the interface between the photoelectric conversion layer having the photovoltaic layer provided therein and the light-transmitting conductive film has an uneven shape, the light-transmitting conductive film In forming the photovoltaic layer at a portion in contact with the concave portion to be thinner than the other portions, according to the present invention, unevenness is formed on the light transmitting conductive film by the intensity of light due to light interference fringes, and As in the case of the conductive film, unevenness is formed on the photovoltaic layer by the intensity of light due to light interference fringes.

[0014]

According to the present invention, in a photovoltaic device in which a photovoltaic layer is provided in a photoelectric conversion layer for performing photoelectric conversion as described above, the internal electric field in the photoelectric conversion layer is non-uniform in the plane direction of the layer surface. In some cases, the thickness of the photovoltaic layer in the portion where the internal electric field is weak is made thinner than in other portions, so that the internal electric field of the photoelectric conversion layer in this portion substantially increases and the internal electric field in the photoelectric conversion layer is uniform to some extent. Accordingly, a decrease in the fill factor in the photovoltaic device is suppressed.

Further, in a photovoltaic device in which an interface between a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film has an uneven shape, as described in the above-mentioned prior art, Although the internal electric field of the photoelectric conversion layer in a portion in contact with the concave portion of the light-transmitting conductive film is reduced, in the present invention, the thickness of the photovoltaic layer in the portion in contact with the concave portion of the light-transmitting conductive film is reduced as described above. Since it is thinner than the other parts, the internal electric field of the photoelectric conversion layer in this part is substantially increased, and the internal electric field in the photoelectric conversion layer is made uniform to some extent. A decrease in the fill factor is suppressed.

As a result, the reduction of the fill factor in the photovoltaic device is suppressed, so that the conversion efficiency in each photovoltaic device is improved.

Further, in the photovoltaic device in which the interface between the photoelectric conversion layer having the photovoltaic layer provided therein and the light-transmitting conductive film has an uneven shape, the light-transmitting conductive film In forming the photovoltaic layer at a portion in contact with the concave portion to be thinner than other portions, as in the present invention, unevenness is formed in the translucent conductive film depending on the intensity of light due to light interference fringes, and the transparent conductive film is formed. When unevenness is formed in the photovoltaic layer in the photoelectric conversion layer by the intensity of light due to light interference fringes as in the case of the light-transmitting conductive film, the unevenness is provided in the photovoltaic layer corresponding to the unevenness of the light-transmitting conductive film. The thickness of the photovoltaic layer at the portion in contact with the concave portion of the light-transmitting conductive film can be easily and reliably reduced, and the interface between the photoelectric conversion layer and the light-transmitting conductive film is made uneven. Even if there is no decrease in fill factor,
A photovoltaic device with good conversion efficiency can be easily obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a photovoltaic device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings, and the photovoltaic device of this embodiment will be superior to a conventional photovoltaic device. Make it clear.

In the photovoltaic device according to this embodiment, as shown in FIG. 3, a textured SnO having an irregular shape is formed on an insulating translucent substrate 1 such as glass.
₂ is formed, and p-type semiconductor layers 3a and i made of p-type amorphous silicon are formed on the light-transmitting conductive film 2 as photoelectric conversion layers 3 for performing photoelectric conversion. A photovoltaic layer 3b made of amorphous silicon of the type and an n-type semiconductor layer 3c made of amorphous silicon of the n-type are sequentially stacked, and furthermore, Ag or the like is formed on the photoelectric conversion layer 3. The back electrode 4 made of a highly reflective metal was provided.

In manufacturing the photovoltaic device, in this embodiment, when the light-transmitting conductive film 2 having the uneven shape is provided on the light-transmitting substrate 1 as described above, FIG. As shown in FIG.
1, and about half of the laser light is directly passed through the half mirror 11 to form the light-transmitting conductive film 2.
On the other hand, about half of the laser light is reflected by the half mirror 11, and about half of the laser light thus reflected is further reflected by the mirror 12 to guide the laser light to the transparent substrate 1. The angle θ between the laser light passing through the half mirror 11 and guided to the transparent substrate 1 and the laser light reflected by the mirror 12 and guided to the transparent substrate 1 is adjusted, and Interference fringes at an appropriate distance d were generated on the substrate 1.

The interval d of the interference fringes generated on the translucent substrate 1 is expressed by the following equation, where λ is the wavelength of the laser light and n is the refractive index of the medium through which the laser light passes. You. d = λ / (n · sin θ)

In this embodiment, ArF excimer laser light having a wavelength λ of 193 nm is used as the laser light, the angle θ is set to 11 degrees, and the refractive index n is set to 1
Under the conditions described above, the distance d is about 1 μm on the light-transmitting substrate 1.
In this situation where the interference fringes are generated, SnCl ₄ is supplied as a source gas at a rate of 7 scc.
m, O ₂ were supplied at a gas flow rate of 350 sccm, the substrate temperature was set to 400 ° C., and the pressure was set to 20 Torr.
The light-transmitting conductive film 2 having an uneven shape was formed on the light-transmitting substrate 1 by the thermal CVD method.

Here, when the light-transmitting conductive film 2 is formed on the light-transmitting substrate 1 as described above, SnO ₂
The deposition rate of the light-transmitting conductive film 2 was about 200 ° / min in the part irradiated with light and about 100 ° / min in the part not irradiated with light. In this embodiment, the light-transmitting conductive film 2 is provided on the light-transmitting substrate 1 for about 30 minutes as described above, and the film thickness X of the projection 2b is formed on the light-transmitting substrate 1. ₁ is about 6000 Å, to form a translucent conductive film 2 having a thickness X ₂ of the recess 2a was about 3000 Å.

After the light-transmitting conductive film 2 having an uneven shape is formed on the light-transmitting substrate 1 in this manner, a film thickness of about 100 ° is formed on the light-transmitting conductive film 2 by a known method. Became p
After forming the mold semiconductor layer 3a, in the same manner as in the case of the light-transmitting conductive film 2 described above, while generating interference fringes having a distance d of about 1 μm, 5% Si ₂ H ₆ is used as a source gas.
0 sccm, N ₂ is supplied at a gas flow rate of 300 sccm, the substrate temperature is 200 ° C., and the pressure is 0.5 Torr.
r, RF power was set to 10 mW / cm ² and plasma C
By the VD method, a photovoltaic layer 3b made of i-type amorphous silicon having an uneven shape corresponding to the light-transmitting conductive film 2 was formed on the p-type semiconductor layer 3a.

Here, when the photovoltaic layer 3b is formed as described above, the deposition rate of the photovoltaic layer 3b is about 60 ° / min in the portion where light is irradiated. It was about 40 ° / min in the missing part. In this embodiment, the photovoltaic layer 3b is provided on the p-type semiconductor layer 3a for about 50 minutes as described above, and the film in the portion corresponding to the convex portion 2b in the translucent conductive film 2 is formed. whereas thickness Y ₁ is about 3000 Å, the photovoltaic layer 3b having a thickness Y ₂ is thinned about 2000Å and film thickness at a portion corresponding to the recess 2b of the p-type semiconductor layer 3
a.

After the photovoltaic layer 3b having the irregular shape corresponding to the translucent conductive film 2 is formed on the p-type semiconductor layer 3a, the film is formed on the photovoltaic layer 3b by a known method. An n-type semiconductor layer 3c having a thickness of about 300 °;
By forming the back electrode 4 having a thickness of 000 °, the photovoltaic device of this example was obtained.

Next, in a comparative example which is compared with the photovoltaic device of this embodiment, the photovoltaic layer 3
The photovoltaic device was obtained in exactly the same way as in the above embodiment except for the method of forming b. Here, in the photovoltaic device of this comparative example, the photovoltaic layer 3
b is formed by using a conventionally known method which has been conventionally performed, and as shown in FIG. 2, a photovoltaic power generation having a substantially uniform film thickness of about 3000 ° on the p-type semiconductor layer 3a. The layer 3b was formed.

Then, each of the photovoltaic devices of the above Examples and Comparative Examples was irradiated with light under the same light irradiation conditions, and the open-circuit voltage (Voc) and short-circuit current (Isc) of each photovoltaic device were measured. , Fill factor (FF) and conversion efficiency were determined, and the results are shown in Table 1 below.

[0029]

[Table 1]

As is apparent from the results, the photovoltaic layer 3
b is formed in an uneven shape corresponding to the light-transmitting conductive film 2, and the thickness of the photovoltaic layer 3b in the portion corresponding to the concave portion 2a of the light-transmitting conductive film 2 is reduced. As compared with the photovoltaic device of the comparative example in which the photovoltaic layer 3b is formed with a substantially uniform film thickness along the translucent conductive film 2, the photovoltaic power generation at the portion corresponding to the concave portion 2a of the translucent conductive film 2 is performed. Despite the fact that the film thickness of the layer 3b was 2/3, there was almost no decrease in the short-circuit current, the fill factor was greatly improved, and the conversion efficiency was improved by about 0.8%.

Here, when comparing the photovoltaic device of this embodiment with the photovoltaic device of the comparative example, even if the photovoltaic layer 3b has a thin portion as described above, the short-circuit current Is hardly decreased because light is absorbed most in the photovoltaic layer 3b in a portion near the light incident side of the photovoltaic layer 3b corresponding to the concave portion 2a of the translucent conductive film 2, and this photovoltaic layer 3b Even if the thickness of the layer 3b is reduced, the amount of generated carriers is rarely reduced, and the decrease in the internal electric field of the photoelectric conversion layer 3 in this portion is suppressed. This is considered to be due to the fact that the photovoltaic device of the comparative example becomes larger than the photovoltaic device of the comparative example, and the effect of confining light is improved.

In the photovoltaic device of this embodiment, SnO ₂ is used as the material of the light-transmitting conductive film 2, but other known light-transmitting conductive materials such as ZnO and ITO are used. Can also be used. Further, as for the material constituting the photoelectric conversion layer 3, in the photovoltaic device of this embodiment, amorphous silicon is used, but other amorphous semiconductors and CuInSe ₂ (copper, indium, A thin film compound semiconductor such as selenium) may be used.

In this embodiment, when the thickness of the photovoltaic layer 3b in the photoelectric conversion layer 3 at the portion in contact with the concave portion 2a of the translucent conductive film 2 is made thinner than other portions, light interference fringes are formed. Unevenness is formed in the light-transmitting conductive film 2 by the intensity of light caused by the light, and the unevenness is formed on the photovoltaic layer 3b in the photoelectric conversion layer 3 by the intensity of the light due to the interference fringes of light as in the case of the light-transmitting conductive film 2. However, the method of providing irregularities on the translucent conductive film 2 and the photovoltaic layer 3b is not particularly limited to such a method. However, if the light-transmitting conductive film 2 and the photovoltaic layer 3b are provided with irregularities as described above, the thickness of the photovoltaic layer 3b can be easily and reliably reduced in correspondence with the concave portion 2a of the light-transmitting conductive film 2. We were able to.

In this embodiment, when the irregularities are formed on the translucent conductive film 2 and the photovoltaic layer 3b by the intensity of light due to the light interference fringes as described above, the distance d between the light interference fringes is set to about 1 μm, and the irregularities with a pitch of about 1 μm are provided on the translucent conductive film 2 and the photovoltaic layer 3b. However, the pitch of the irregularities provided on the translucent conductive film 2 and the photovoltaic layer 3b depends on the incident light. Any range is possible as long as scattering is performed effectively, and is generally in the range of about 0.1 to 10 μm, preferably in the range of 0.3 to 1.5 μm.

In the photovoltaic device of this embodiment, when the interface between the photoelectric conversion layer 3 and the light-transmitting conductive film 2 is formed in an uneven shape, the light-transmitting conductive film 2 itself has unevenness. However, the light-transmitting substrate 1 on which the light-transmitting conductive film 2 is formed is provided with unevenness, and the light-transmitting conductive film 2 is formed on the light-transmitting substrate 1 having such an uneven shape. It is also possible to form and make the interface to be bonded to the photoelectric conversion layer 3 an uneven shape.

Further, in the photovoltaic device of this embodiment, the interface at which the photoelectric conversion layer 3 and the translucent conductive film 2 are joined is formed in an uneven shape, and the internal electric field in the photoelectric conversion layer 3 is reduced by the surface of the layer. Although only an example in which the non-uniformity is obtained in the plane direction of the photoelectric conversion layer 3 is shown, even if the internal electric field in the photoelectric conversion layer 3 becomes non-uniform in the plane direction of the layer surface due to other factors, By making the thickness of the photovoltaic layer 3b at a portion where the internal electric field is weak as compared with the other portions, the internal electric field of the photoelectric conversion layer 3 is made uniform to some extent and the fill factor in the photovoltaic device is improved. Can be.

[0037]

As described above in detail, according to the present invention, in a photovoltaic device in which a photovoltaic layer is provided in a photoelectric conversion layer, the internal electric field in the photoelectric conversion layer is non-uniform in the layer direction. In some cases, the thickness of the photovoltaic layer in a portion where the internal electric field is weak is made thinner than in other portions, so that the internal electric field of the photoelectric conversion layer in this portion substantially increases,
The internal electric field in the photoelectric conversion layer was made uniform to some extent, whereby the fill factor in the photovoltaic device was improved, and the conversion efficiency was improved.

In the present invention, the interface between the photoelectric conversion layer having the photovoltaic layer provided therein and the light-transmitting conductive film is formed in an uneven shape, and the incident light is scattered at this interface. As compared with the photovoltaic device, the thickness of the photovoltaic layer at the portion joined to the concave portion of the light-transmitting conductive film is made thinner than the other portions. The internal electric field of the layer increases substantially,
The internal electric field in the photoelectric conversion layer becomes uniform to some extent, and the fill factor is reduced as in a conventional photovoltaic device in which the interface between the photoelectric conversion layer and the light-transmitting conductive film is formed in an uneven shape. Therefore, a photovoltaic device with high conversion efficiency can be obtained.

According to the present invention, when the thickness of the photovoltaic layer at the portion in contact with the concave portion of the light-transmitting conductive film is made thinner than at other portions as described above, the intensity of light due to light interference fringes is increased. Since the unevenness is formed in the light-transmitting conductive film and the unevenness is formed in the photovoltaic layer in the photoelectric conversion layer by the intensity of the light due to the interference fringes of the light as in the case of the light-transmitting conductive film, In this case, the thickness of the photovoltaic layer can be easily and reliably reduced in accordance with the concave portions of the conductive film, and the interface between the photoelectric conversion layer and the light-transmitting conductive film is made uneven as described above. No decrease in fill factor
A photovoltaic device with good conversion efficiency can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a structure of a conventional photovoltaic device.

FIG. 2 is a schematic cross-sectional view showing an example of a structure of a conventional photovoltaic device in which an interface at which a light-transmitting conductive film and a photoelectric conversion layer are in contact has an uneven shape.

FIG. 3 is a schematic sectional view showing a structure of a photovoltaic device according to one embodiment of the present invention.

FIG. 4 is a schematic explanatory view showing a state in which unevenness is formed on a light-transmitting conductive film or a photovoltaic layer by the intensity of light due to light interference fringes in the photovoltaic device of the embodiment.

[Explanation of symbols]

 Reference Signs List 2 translucent conductive film 2a concave portion of translucent conductive film 3 photoelectric conversion layer 3b photovoltaic layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (3)

(57) [Claims] In a photovoltaic device in which a photovoltaic layer is provided in a photoelectric conversion layer, when an internal electric field in the photoelectric conversion layer is non-uniform in a plane direction of the layer surface, the photovoltaic device in a portion where the internal electric field is weak A photovoltaic device characterized in that the photovoltaic layer has a smaller thickness than other portions. 2. A portion of a photovoltaic device in which an interface between a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film has an uneven shape, the portion being in contact with a concave portion of the light-transmitting conductive film. 3. The photovoltaic device according to claim 1, wherein the thickness of the photovoltaic layer is smaller than other portions. 3. A portion of a photovoltaic device in which an interface between a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film has an uneven shape, the portion being in contact with a concave portion of the light-transmitting conductive film. In forming the photovoltaic layer at a thickness smaller than that of the other portions, unevenness is formed in the light-transmitting conductive film by the intensity of light due to light interference fringes, and light is emitted similarly to the light-transmitting conductive film. Forming unevenness in the photovoltaic layer according to the intensity of light caused by the interference fringes.