JPH0888380A - Substrate for photovoltaic element and its manufacture - Google Patents

Abstract

PURPOSE: To obtain a texture structure which is optimum for constituting a photovoltaic element of good characteristic and reliability by forming it by depositing transparent conductive oxygen coated particle consisting of an inner shell of high polymer resin and an outer shell of an oxide semiconductor layer. CONSTITUTION: A substrate is provided with a supporting substrate 101 and an injection side electrode 102. It is formed by depositing particles coated with transparent conductive oxide. Each particle consists of an inner shell of polymer resin and an outer shell of an oxide semiconductor layer applied to the inner shell. The polymer resin consists of at least one kind of polymer selected from acrylic, sthyrene and nylon. The oxide semiconductor consists of at least one kind selected from In2 O3 , TiO2 , SnO2 , ITO, ZnO and one wherein dopant is added to them. Thereby, a photovoltaic element of good initial characteristic and reliability is applicable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device substrate and a method for producing the same, and more particularly to a solar cell substrate having good conversion efficiency and manufacturing stability.

[0002]

2. Description of the Related Art Photovoltaic devices are used in solar cells, which are drawing attention as alternative energy sources that solve the problems of existing power generation methods such as thermal power generation and hydroelectric power generation. In particular, amorphous silicon solar cells are under active research and development because they can manufacture large-area solar cells at lower cost than crystalline solar cells.

An important technical issue in putting this amorphous silicon solar cell into practical use is to improve the photoelectric conversion efficiency, and various studies have been made to improve the conversion efficiency. Effective utilization is an important technical issue.

Amorphous silicon solar cells are manufactured mainly by forming a light-receiving surface electrode, a semiconductor layer, and a back surface electrode on a light-transmitting substrate such as glass in this order, or a non-light-transmitting material such as stainless steel. There is a method of laminating a semiconductor layer and a light-receiving surface electrode in this order on a flexible substrate. The light-receiving surface electrode is formed of a transparent conductive oxide, and as a forming method, a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a spray method, or the like is used. However, since the transparent conductive oxide and the semiconductor layer have different refractive indexes, a part of the incident light is reflected at the interface of the layer and cannot be effectively used. As a solution to this problem, studies are being made to provide the transparent conductive oxide with appropriate irregularities. By providing the unevenness, the incident light is scattered, the reflection is reduced, and the absorption in the semiconductor layer is increased. The invention of providing such unevenness is disclosed in JP-A-58-57756 and JP-A-62-90.
It is disclosed in Japanese Patent Publication No. 983, Japanese Patent Laid-Open No. 59-20147, Japanese Patent Publication No. 3-28073, and the like.

FIG. 6 is a schematic sectional view showing an example of a conventional amorphous silicon solar cell disclosed in Japanese Patent Publication No. 3-28073. In the figure, 601 is a transparent support substrate, 602 is a transparent conductive oxide which is an electrode on the light receiving surface side, 603, 604 and 605 are semiconductor layers, respectively.
Reference numeral 6 represents a back electrode. The transparent conductive oxide 602 has appropriate unevenness and has a function of scattering incident light so that the semiconductor layer is effectively absorbed. Such a structure is called a texture structure. A conventional example of the texture structure can be schematically represented as shown in FIG. In FIG. 3, 301 is a supporting substrate, 302 is a transparent conductive oxide, 2
r is the grain size of the irregularities, h is the height difference of the irregularities, and d is the interval between the convex portions. In the disclosed invention, it is said that the average particle size 2r forming the irregularities is preferably 0.1 μm to 2.5 μm. The height difference h of the unevenness is 0.1 μm.
It is said that m to 0.6 μm is suitable. It has also been proposed that good characteristics can be obtained by setting the interval d between the convex portions to 0.2 μm to 1.0 μm.

In order to obtain a suitable texture structure as described above, a method of depositing the transparent conductive oxide on the substrate which has been roughened by etching in advance or an etching of the transparent conductive oxide deposited on the substrate is performed. A method of forming irregularities using a method has been proposed. Further, it has been proposed that the transparent conductive oxide is formed as crystal grains to control unevenness. Further, as disclosed in Japanese Examined Patent Publication No. 60-41878, the transparent conductive oxide has a texture structure in the same manner as described above in the solar cell having the structure shown in FIG.

[0007]

However, in the above-mentioned conventional method for forming a transparent conductive oxide, there is a method of controlling the film quality and morphology (morphology such as unevenness) by parameters such as substrate temperature, gas flow rate and internal pressure. However, depending on these control factors, it is difficult to form the unevenness of the texture structure in terms of the size and interval of the unevenness with a desired shape and size, and the unevenness of the unevenness is large. Therefore, the desired optical effect is not sufficient, and the current value of the solar cell needs to be further improved.
Further, when the semiconductor layer is formed on the texture structure, there is a problem that the thin semiconductor layer is not normally formed due to the sharp irregularities, a shunt is generated, the conversion efficiency is lowered, and the yield is deteriorated.

The present invention overcomes the above problems and provides a photovoltaic device substrate having a texture structure most suitable for constructing a photovoltaic device having good characteristics and reliability, and at the same time, providing a texture structure. It is an object of the present invention to provide a method for producing a substrate for a photovoltaic device, which has good controllability and is simple.

[0009]

A substrate for a photovoltaic element of the present invention is a transparent conductive oxide coated particle comprising an inner shell of a polymer resin and an outer shell of an oxide semiconductor layer covering the inner shell. It is characterized by being deposited.

Further, in the method for producing a substrate for a photovoltaic element according to the present invention, a monomer for forming a polymer resin and an oxide semiconductor are mixed and suspension polymerization is carried out to form an inner shell of the polymer resin. It is characterized by forming transparent conductive oxide coated particles composed of the outer shell of the oxide semiconductor layer covering the inner shell and depositing the transparent conductive oxide coated particles on the substrate.

The polymer resin is preferably composed of at least one polymer selected from acrylic, styrene and nylon.

The oxide semiconductor is In ₂ O ₃ , Ti
It is desirable to be composed of at least one selected from O ₂ , SnO ₂ , ITO, ZnO and those obtained by adding a dopant to these.

The diameter of the transparent conductive oxide coated particles is preferably 0.3 to 10 μm.

[0014]

When the transparent conductive oxide semiconductor is formed as a thin film, the cause of the shunt described above is that it is formed as a polycrystal, so that sharp facets are always generated and the convex portion of the texture is formed at an acute angle. It is considered that the semiconductor layer is not normally formed on the portion.

According to the present invention, it is possible to replace the conventional acute-angled texture with a textured structure having a curved surface shape, and as a result, the initial production yield of a photovoltaic element and the reliability during long-term use. It is possible to improve the property. That is, this is possible only by using transparent conductive oxide-coated particles composed of an inner shell of a polymer resin and an outer shell of an oxide semiconductor layer that covers the inner shell, and disposing the particles on a substrate. It has become.

The transparent conductive oxide-coated particles are provided between the substrate and the semiconductor layer. However, when the substrate is translucent like a glass substrate, it is located on the light incident side and therefore serves as an electrode on the light receiving surface side. If the substrate is opaque like a stainless steel substrate, it acts as a back electrode.

As the structure of the transparent conductive oxide-coated particles, a spherical inner shell is provided, and an outer shell of the transparent conductive oxide semiconductor is formed so as to cover the inner shell. The function of the inner shell is to maintain the shape of the transparent conductive oxide-coated particles and serve as a nucleus for depositing the outer shell.

The shape of the inner shell is preferably spherical and is preferably a true sphere, but the same effect can be obtained even if it is deformed such as an ellipse. As a material for forming the inner shell, a transparent polymer resin or the like is preferable. As the polymer resin, specifically, versatile resins such as acrylic, styrene, silicone, polycarbonate, vinyl chloride, epoxy, polyester are preferably used, and as the resin particularly suitable for the production method of the present invention, Acrylic, styrene and nylon are mentioned.

The particle diameter of the inner shell depends on the thickness of the outer shell, but the light absorption is as small as possible, the texture structure can be maintained, and the adhesion with the substrate is designed to be good.
Specifically, it is preferably about 0.1 μm to 5 μm.

As the transparent conductive oxide semiconductor of the outer shell, In ₂ O ₃ , TiO ₂ , SnO ₂ , ITO and Zn are used.
O and materials obtained by adding a suitable dopant to these materials are preferably used.

The thickness of the transparent conductive oxide semiconductor layer is determined in relation to the wavelength of light because it has a predetermined conductivity and a function of causing light scattering is required. Is preferably 0.1 to 2.5 μm.

The surface shape of the transparent electrode of the photovoltaic device substrate of the present invention is preferably, for example, as shown in FIG. FIG.
2r is the grain size of the unevenness, h is the height difference of the unevenness, and d
Indicates the interval between the convex portions. In FIG. 1, the particle diameters of the transparent conductive oxide coated particles forming the irregularities are uniform, and thus the particle diameter 2r is uniform. FIG. 2 shows a second preferred example of the present invention. In this case, since the particle diameters of the transparent conductive oxide coated particles are distributed, the particle diameter 2r and the height difference h are also distributed. The particle size 2r is preferably in the range of 0.3 μm to 10 μm, and h and d are necessarily determined from the value of the particle size 2r.

As a method of forming the transparent conductive oxide coated particles, for example, a wet method can be used. That is, a polymer resin forming an inner shell is prepared by emulsion polymerization, and during this polymerization, fine particles of a transparent conductive oxide are simultaneously suspended so that the inner shell is a polymer resin and the outer shell is a transparent conductive oxide. The particles formed in 1. are obtained. When an acrylic resin is used as the polymer resin, for example, acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and monomers such as methacrylic monomers are dispersed in an aqueous solution. Form an emulsion. Similarly, when producing other resins, the monomers of the respective resins are used as starting materials. Further, as a transparent conductive oxide for the outer shell, for example, In ₂ O ₃
To form indium chloride (II
Dissolve I). Then, a suitable catalyst such as potassium peroxodisulfate, hydrogen peroxide, α-cumyl hydroperoxide, etc. is added and polymerized. In some cases, a surfactant may be added to stabilize the emulsification.

The spherical transparent conductive oxide-coated particles are produced to have a desired particle size depending on the polymerization conditions. If the particle size is not uniform, the particles are classified by an appropriate known method to obtain the desired particle size. May be. As another method for forming spherical transparent conductive oxide coated particles, for example, as a method of forming an inner shell made of a polymer resin and then forming an outer shell oxide semiconductor by a spray method or the like. Is also good.

For laminating the transparent conductive oxide-coated particles on the substrate, for example, a method is used in which a paste is prepared by dispersing in a suitable binder, and the paste is applied onto the suitable substrate. Further, as another method, a method of selecting an appropriate material that is melted by heat as the polymer resin of the inner shell and laminating by thermocompression bonding without using a binder is also used. For example, acrylic resin is used as the polymer resin for the inner shell,
By heating at 0 ° C. or higher, the acrylic resin can be melted and laminated.

The photovoltaic element substrate of the present invention is preferably used for an amorphous silicon solar cell,
The present invention is not limited to amorphous silicon, but can be applied to thin-film polycrystalline silicon solar cells, CdS solar cells, etc., and can also be applied to tandem solar cells having two or more semiconductor junctions, Schottky solar cells, etc. Needless to say.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a structural example of a photovoltaic element substrate of the present invention. In the figure, 101 is a supporting substrate and 102 is an incident side electrode.

Particles coated with an acrylic resin for the inner shell and ITO transparent conductive oxide for the outer shell were prepared as follows.

First, methyl acrylate as a monomer,
Potassium sulfate was dissolved in an aqueous solution as a polymerization catalyst to obtain an emulsion. Then, indium (III) chloride as a transparent conductive oxide forming material was dissolved to initiate polymerization. After completion of the polymerization, salting out, coagulation, filtration, washing with water and drying were carried out to obtain transparent conductive oxide-coated particles. The particle size of the transparent conductive oxide-coated particles was measured and found to be about 1 μm.

Next, 1 part of the transparent conductive oxide-coated particles was added.
It was applied on a 70-cm square Corning No. 7059 glass substrate and heated in a hot air drier to form an incident side electrode 102 having the surface shape shown in FIG. In this example, the particle size 2r was 1 μm, the height h was 0.5 μm, and the interval d was 1 μm.

In this embodiment, the inner shell is made of acrylic resin.
However, when styrene resin or nylon resin is used, the same result is obtained.
Fruit is obtained, and instead of ITO as an outer shell, In₂O₃,
TiO ₂, SnO₂, ZnO and suitable dopants for these materials
Similar results were obtained when using materials such as pant
Was done.

(Embodiment 2) FIG. 4 shows a constitutional example of a photovoltaic element using the photovoltaic element substrate of the present invention. In the figure, 400 is a photovoltaic element, 401 is a translucent support substrate,
Reference numeral 402 denotes an incident side electrode, 403, 404 and 405 denote semiconductor layers, and 406 denotes a back surface electrode. In this figure, pin
However, it is needless to say that the same effect as that of the present embodiment can be obtained even if the semiconductor layer has a tandem structure, a thin film polycrystal, or the like.

This photovoltaic element was produced as follows. First, transparent conductive oxide-coated particles having an acrylic resin inner shell and ITO outer shell were prepared by the method described in Example 1.

Next, in the same manner as in Example 1, the transparent conductive oxide-coated particles were applied onto a 1 cm square Corning No. 7059 glass substrate and heated in a hot air drier to form an incident side electrode 402. . In this embodiment, the particle size 2r is 1 μm
And the height h was 0.5 μm and the interval d was 1 μm.

Further, an amorphous silicon p-type semiconductor layer 403 is formed by using an RF plasma CVD apparatus (not shown).
An i-type semiconductor layer 404 of amorphous silicon and an n-type semiconductor layer 405 of amorphous silicon were formed. Then, a silver back electrode 406 is formed by using a sputtering device (not shown).
Was formed.

The initial characteristics of the photovoltaic element thus manufactured and the characteristics after the reliability test were measured. For the measurement of the characteristics, a pseudo solar light source having a light amount of 100 mW / cm ^{2 in} the AM1.5 global sunlight spectrum using the JISC8913 crystalline solar cell output measuring method was used. The reliability test was performed based on the temperature / humidity cycle test output measurement method A-2 defined in the environmental test method and the durability test method of the JIS C8917 crystalline solar cell module.

As a result of the measurement, the initial conversion efficiency is 5% ± 0.2.
It was 5%. The shunt resistance is 55 kΩcm ²
And it turns out that there are few shunts.

The characteristic after the reliability test is that the conversion efficiency is 4.8.
% ± 0.5%, there was no significant decrease in efficiency, and the shunt resistance was 55 kΩcm ^2, which was not changed by the reliability test.

From the above, it can be seen that by using the photovoltaic device substrate of this embodiment, a shunt can be prevented and a highly efficient solar cell can be obtained.

Comparative Example 1 A conventional photovoltaic element 600 was manufactured in the same manner as in Example 2 except that the transparent conductive oxide 602 was manufactured by the conventional method.

First, an ITO layer was formed on a 1 cm square glass substrate by using a sputtering device (not shown). The formed electrode 602 had a texture with a sharp tip. Subsequently, a p-type semiconductor layer 603, an i-type semiconductor layer 604, and an n-type semiconductor layer 605 are formed using an RF plasma CVD device (not shown).
Was formed. After that, a silver back electrode 606 was formed using a sputtering device (not shown).

The initial efficiency of the photovoltaic element thus produced was measured in the same manner as in Example 2. The conversion efficiency was 4.5% ± 1.25%, and
It was confirmed that the shunt resistance was 10 kΩcm ² and there were many shunts. Further, when a reliability test was conducted in the same manner as in Example 2, the conversion efficiency was 3.5% ± 0.5%,
The shunt resistance decreased to 1 kΩcm ² , and it was found that the shunt resistance was inferior to that of Example 1.

(Embodiment 3) Next, using the substrate for a photovoltaic element shown in FIG. 2, a structural example of the second preferred photovoltaic element of the present invention shown in FIG. It was made.

First, the inner shell is styrene resin and the outer shell is ITO.
The transparent conductive oxide covering particles of No. 3 were produced in the same manner as in Example 2 except that classification was not performed after formation.

The particle size of the obtained transparent conductive oxide-coated particles was measured and found to be 0.5 to 8 μm.

Next, the transparent conductive oxide-coated particles were mixed with 1
It was applied onto a cm square glass substrate and heated to form an incident side electrode 502 having a surface shape shown in FIG. The particle size 2r is 0.
It was 5 to 8 μm, the height h was 0.25 to 4 μm, and the interval d was 0.25 to 4 μm. Furthermore, RF (not shown)
A p-type semiconductor layer 503, an i-type semiconductor layer 504, and an n-type semiconductor layer 505 were formed using a plasma CVD apparatus. Then, a silver back electrode 506 is formed by using a sputtering device (not shown).
Was formed.

When the initial characteristics of the thus-produced photovoltaic element were measured in the same manner as in Example 2, the conversion efficiency was 5.5% ± 0.1%. The shunt resistance was 35 kΩcm ² , and it was found that there was almost no shunt.

The characteristic after the reliability test is that the conversion efficiency is 5.3.
% ± 0.2%, which means that significant reduction in efficiency did not occur.
Further, it was found that the shunt resistance was 20 kΩcm ² and hardly changed.

As described above, according to the present invention, it is understood that a photovoltaic element having high initial characteristics and high reliability can be obtained.

In this example, a styrene resin was used for the inner shell as in Example 2, but similar results were obtained with an acrylic resin or a nylon resin. In addition, the outer shell is made of In ₂ O ₃ , Ti
Similar results are obtained when O ₂ , SnO ₂ , ZnO, etc. are used.

[0052]

According to the first aspect of the present invention, that is, a photovoltaic layer formed by depositing transparent conductive oxide coated particles having an inner shell of a polymer resin and an outer shell of an oxide semiconductor layer covering the inner shell. By using the element substrate, it is possible to apply a photovoltaic element having excellent initial characteristics and good reliability.

Further, according to the invention of claim 5, that is, by mixing a monomer for forming a polymer resin and an oxide semiconductor and carrying out suspension polymerization, the inner shell of the polymer resin and the inner shell are coated. By forming transparent conductive oxide-coated particles composed of an outer shell of an oxide semiconductor layer and depositing the transparent conductive oxide-coated particles on a substrate, it is suitable for a photovoltaic device having high characteristics and high reliability. It is possible to easily and stably manufacture a photovoltaic device substrate having a texture structure.

When the polymer resin is at least one kind of polymer selected from acrylic, styrene and nylon, it is possible to obtain a substrate for a photovoltaic element which is easy to manufacture and has good characteristics.

The oxide semiconductor is In ₂ O ₃ , TiO ₂ ,
By using at least one selected from SnO ₂ , ITO, ZnO and a material obtained by adding a dopant to the above materials, a substrate for a photovoltaic device having low resistance and good characteristics can be obtained.

By setting the diameter of the transparent conductive oxide-coated particles to 0.3 to 10 μm, a substrate for a photovoltaic element having good optical characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a photovoltaic device substrate of the present invention.

FIG. 2 is a schematic view showing another configuration example of the substrate for photovoltaic element of the present invention.

FIG. 3 is a schematic view showing a conventional photovoltaic device substrate.

FIG. 4 is a schematic view showing a configuration example of a photovoltaic element using the photovoltaic element substrate of the present invention.

FIG. 5 is a schematic view showing another configuration example of a photovoltaic element using the photovoltaic element substrate of the present invention.

FIG. 6 is a schematic view showing a conventional photovoltaic device.

FIG. 7 is a schematic view showing a conventional photovoltaic device.

[Explanation of Codes] 100, 200, 300 101, 201, 301, 401, 501, 601, 7
01 support substrate, 102, 202, 303, 404, 505, 606, 7
07 electrode, 400, 500, 600, 700 photovoltaic element, 403, 503, 603, 703 p-type semiconductor layer, 404, 504, 604, 704 i-type semiconductor layer, 405, 505, 605, 705 n-type semiconductor layer , 406, 506, 606, 706 Backside electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Hasebe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (8)

[Claims] 1. A photovoltaic element comprising a transparent conductive oxide-coated particle comprising an inner shell of a polymer resin and an outer shell of an oxide semiconductor layer covering the inner shell. substrate. 2. The substrate for a photovoltaic element according to claim 1, wherein the polymer resin is made of at least one kind of polymer selected from acryl, styrene and nylon. 3. The oxide semiconductor is In ₂ O ₃ , TiO
_The substrate for a photovoltaic element according to claim 1 or 2, comprising at least one selected from the group consisting of ₂ , SnO ₂ , ITO, ZnO, and dopants added to these. 4. The substrate for a photovoltaic element according to claim 1, wherein the diameter of the transparent conductive oxide-coated particles is 0.3 to 10 μm. 5. An inner shell of the polymer resin and an outer shell of the oxide semiconductor layer covering the inner shell by mixing the polymer resin-forming monomer and the oxide semiconductor to carry out suspension polymerization. A method for producing a substrate for a photovoltaic element, which comprises producing transparent conductive oxide-coated particles and depositing the transparent conductive oxide-coated particles on a substrate. 6. The method for manufacturing a photovoltaic device substrate according to claim 5, wherein the polymer resin is made of at least one polymer selected from acryl, styrene and nylon. 7. The oxide semiconductor is In ₂ O ₃ , TiO
7. The method for producing a substrate for a photovoltaic element according to claim 5, comprising at least one selected from the group consisting of ₂ , SnO ₂ , ITO, ZnO, and dopants added to these. 8. The diameter of the transparent conductive oxide-coated particles is 0.3 to 10 μm.
8. A method for manufacturing a photovoltaic device substrate according to any one of items 1 to 7.