JP4905595B2 - Organic thin film solar cell, organic thin film solar cell module, and organic thin film solar cell manufacturing method - Google Patents

Description

The present invention relates to an organic thin film solar cell having a transparent electrode layer containing a conductive metal oxide.

In the solar cell, the electrode on the light receiving side is a transparent electrode. Conventionally, conductive metal oxides such as indium tin oxide (ITO) have been used for this transparent electrode. Among them, ITO is mainly used because of its high conductivity and transparency and high work function. ing.
However, since the ITO electrode used for the solar cell is thin and has a large sheet resistance, there is a problem that the generated current is consumed when passing through the ITO electrode and power generation efficiency is lowered. This phenomenon becomes more prominent as the area of the solar cell increases.

  An annealing process has been proposed as a technique for reducing the resistance of the ITO electrode (see, for example, Patent Document 1). In addition, studies have been made to crystallize an ITO film by irradiating a laser to improve electrical conductivity (for example, see Non-Patent Document 1). Further, in addition to ITO, it has been proposed to crystallize a metal oxide exhibiting n-type or p-type semiconductor properties, for example, an oxide layer such as indium or tin by irradiating a laser (for example, a patent). Reference 2). These methods use a laser annealing method.

JP-A-6-88973 JP 2004-314313 A

Plastic LCD Material Technology and Low Temperature Process Technical Information Association 2002 p. 65-71

  However, when the ITO electrode is crystallized by annealing, there is a problem that the ITO electrode becomes brittle. In particular, in a flexible solar cell, the ITO electrode breaks when bent, resulting in a problem that the conversion efficiency is lowered. In addition, although a flexible film substrate is used in the flexible solar cell, since the film substrate has low heat resistance, it is difficult to perform an annealing process when forming an ITO electrode on the film substrate.

  In particular, in an organic thin film solar cell, a buffer layer may be provided between the electrode and the photoelectric conversion layer so that the charge can be easily taken out from the photoelectric conversion layer to the electrode. In this buffer layer, polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) is often employed. However, since the coating liquid containing PEDOT / PSS shows acidity, when a coating liquid containing PEDOT / PSS is applied on the electrode to form a buffer layer, there is a risk of damage such as dissolution of the electrode by the acid. is there. Further, when the buffer layer absorbs moisture, PEDOT / PSS in the buffer layer shows acidity, and the electrode may be similarly damaged.

The present invention has been made in view of the above problems, and provides an organic thin-film solar cell having an electrode having both low resistance and flexibility , and further capable of reducing damage to the electrode due to acid. The main purpose is to do.

  As a result of intensive studies in order to solve the above problems, the present inventor crystallized only the surface of an amorphous film containing a conductive metal oxide by laser annealing, so that low resistance, flexibility, The inventors have found that a transparent electrode layer having acid resistance can be obtained, and have completed the present invention.

The present invention provides a transparent substrate having flexibility, a transparent electrode layer formed on the transparent substrate, a buffer layer containing polyethylenedioxythiophene / polystyrenesulfonic acid formed on the transparent electrode, An organic thin film solar cell having a photoelectric conversion layer formed on a buffer layer and a counter electrode layer formed on the photoelectric conversion layer , wherein the transparent electrode layer is formed on the transparent substrate and is conductive An amorphous film containing a conductive metal oxide, and a crystal formed on the amorphous film and containing the same conductive metal oxide as the conductive metal oxide contained in the amorphous film An organic thin film solar cell comprising a film is provided.

  According to the present invention, since the transparent electrode layer has an amorphous film and a crystal film containing the same conductive metal oxide, a transparent electrode layer having both low resistance and flexibility can be obtained. In addition, since the crystalline film is a crystallized amorphous film, it has better acid resistance than the amorphous film. Since this crystalline film is formed on the buffer layer side, the buffer layer is made acidic. In the case of containing the material shown, the amorphous film is protected by the crystal film, and the damage of the transparent electrode layer due to the influence of the acid contained in the buffer layer can be reduced, thereby improving the reliability of the organic thin film solar cell. It becomes possible to improve.

In the said invention, the heat insulation layer may be formed between the said transparent substrate and the said transparent electrode layer. This is because the transparent substrate can be protected from heat during the annealing process when the transparent electrode layer is formed by the heat insulating layer. In particular, since a transparent substrate having flexibility tends to be inferior in heat resistance, a heat insulating layer is preferably formed.

  Furthermore, the present invention provides an organic thin film solar cell module, wherein a plurality of the above organic thin film solar cells are connected in series or in parallel.

The present invention also includes a transparent substrate having flexibility, a transparent electrode layer formed on the transparent substrate, a buffer layer containing polyethylenedioxythiophene / polystyrenesulfonic acid formed on the transparent electrode, A method for producing an organic thin film solar cell, comprising: a photoelectric conversion layer formed on the buffer layer; and a counter electrode layer formed on the photoelectric conversion layer, wherein a conductive metal oxide is formed on the transparent substrate. After forming the amorphous film to be contained, the surface of the amorphous film is crystallized by laser annealing to form a crystalline film, thereby obtaining the transparent film layer having the amorphous film and the crystalline film Forming a buffer layer by applying a coating solution for forming a buffer layer containing polyethylenedioxythiophene / polystyrenesulfonic acid on the transparent electrode layer; It provides a method for manufacturing an organic thin film solar cell and having an over layer forming step.

  According to the present invention, the surface of the amorphous film is crystallized by laser annealing to form a crystalline film, and the transparent electrode layer having the amorphous film and the crystalline film is obtained. Therefore, the transparent film having both low resistance and flexibility is obtained. An electrode layer can be formed. Since the crystalline film is a crystallized amorphous film, it has better acid resistance than the amorphous film. Therefore, a buffer layer forming coating solution that shows acidity is applied onto the transparent electrode layer to buffer the crystalline film. When forming a layer, it is possible to reduce damage to the transparent electrode layer due to the influence of an acid. Therefore, a highly reliable organic thin film solar cell can be obtained.

In the present invention, since the transparent electrode layer has an amorphous film and a crystal film containing the same conductive metal oxide, a transparent electrode layer having both low resistance and flexibility and also having acid resistance is provided. There exists an effect that it can be set as the organic thin film solar cell which has .

It is a schematic sectional drawing which shows an example of the board | substrate for solar cells of this invention. It is a schematic sectional drawing which shows an example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows an example of an organic thin film solar cell provided with the board | substrate for solar cells of this invention. It is a schematic sectional drawing which shows the other example of the board | substrate for solar cells of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the board | substrate for solar cells of this invention. It is a schematic sectional drawing which shows the other example of the board | substrate for solar cells of this invention. It is process drawing which shows an example of the manufacturing method of the board | substrate for solar cells of this invention. It is process drawing which shows an example of the manufacturing method of the organic thin film solar cell of this invention.

Hereinafter, the solar cell substrate, organic thin film solar cell, organic thin film solar cell module, solar cell substrate manufacturing method, and organic thin film solar cell manufacturing method of the present invention will be described in detail.

A. First, the solar cell substrate of the present invention will be described.
The solar cell substrate of the present invention is a solar cell substrate having a transparent substrate and a transparent electrode layer formed on the transparent substrate, wherein the transparent electrode layer is formed on the transparent substrate and is electrically conductive. An amorphous film containing a conductive metal oxide, and a crystal formed on the amorphous film and containing the same conductive metal oxide as the conductive metal oxide contained in the amorphous film And a film.

The solar cell substrate of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the solar cell substrate of the present invention. In the example shown in FIG. 1, a solar cell substrate 1 includes a transparent substrate 2 and a transparent electrode layer 3 formed on the transparent substrate 2 and containing a conductive metal oxide. The transparent electrode layer 3 is formed on the transparent substrate 2 and includes an amorphous film 3a containing a conductive metal oxide, and a crystal film 3b formed on the amorphous film 3a and containing a conductive metal oxide. And have. The amorphous film 3a and the crystal film 3b contain the same conductive metal oxide, and the crystal film 3b is obtained by crystallizing the surface of the amorphous film 3a.

  In general, in a conductive metal oxide, a crystalline film has a lower resistance than an amorphous film, that is, has high conductivity. In the conductive metal oxide, the crystal film has better acid resistance than the amorphous film. Further, in the conductive metal oxide, the work function is different between the amorphous film and the crystal film.

  According to the present invention, since the transparent electrode layer has a crystal film having a resistance lower than that of the amorphous film, the conductivity of the transparent electrode layer itself can be increased. Further, since the transparent electrode layer has an amorphous film having excellent flexibility, it is possible to maintain the flexibility of the transparent electrode layer itself. Therefore, in the present invention, a transparent electrode layer having both low resistance and flexibility can be obtained.

  According to the invention, when the transparent substrate is a flexible film substrate, the transparent electrode layer has an amorphous film and is excellent in flexibility. It is possible to obtain a high-performance flexible solar cell by using

  FIG. 2 is a schematic cross-sectional view showing an example of an organic thin-film solar cell having the solar cell substrate of the present invention. An organic thin film solar cell 10 shown in FIG. 2 includes a solar cell substrate 1, a buffer layer 4 formed on the transparent electrode layer 3, a photoelectric conversion layer 5 formed on the buffer layer 4, and a photoelectric conversion layer 5. A counter electrode layer 6 formed thereon.

According to the present invention, the transparent electrode layer has an amorphous film and a crystal film, and the crystal film having excellent acid resistance is formed on the buffer layer side. Therefore, in the organic thin film solar cell as shown in FIG. 2, when the buffer layer contains an acidic material, the buffer layer is not in direct contact with the amorphous film, and the Since the film is protected, damage to the transparent electrode layer due to the influence of the acid contained in the buffer layer can be reduced. Thereby, it can suppress that a transparent electrode layer melt | dissolves by the influence of an acid and the electrical property of a transparent electrode layer falls. As a result, it becomes possible to improve the reliability of the organic thin film solar cell.
Therefore, in the present invention, the resistance of the transparent electrode layer can be reduced, the damage of the transparent electrode layer due to acid can be suppressed, and the electrical performance can be improved.

  FIG. 3 is a schematic cross-sectional view showing another example of an organic thin-film solar cell having the solar cell substrate of the present invention. The organic thin film solar cell 20 shown in FIG. 3 has a solar cell substrate 1, an organic layer 15 formed on the transparent electrode layer 3, and a counter electrode layer 6 formed on the organic layer 15. .

  According to the present invention, since the work function is different between the amorphous film and the crystal film of the transparent electrode layer, in the organic thin film solar cell as shown in FIG. 3, the work function is set at the interface between the transparent electrode layer and the organic layer. It is possible to adjust. For example, the difference between the work function of the crystalline film and the work function of the organic layer in direct contact with the transparent electrode layer is greater than the difference between the work function of the amorphous film and the work function of the organic layer in direct contact with the transparent electrode layer. When it is small, the charge mobility from the organic layer to the transparent electrode layer can be improved.

  Hereafter, each structure in the board | substrate for solar cells of this invention is demonstrated.

1. Transparent electrode layer The transparent electrode layer in the present invention is formed on a transparent substrate, formed on the transparent substrate, and formed on the amorphous film containing the conductive metal oxide and the amorphous film. And a crystalline film containing the same conductive metal oxide as the conductive metal oxide contained in the amorphous film. The amorphous film and the crystalline film contain the same conductive metal oxide, and the crystalline film is obtained by crystallizing the surface of the amorphous film. Even if the elemental composition of the conductive metal oxide changes during the process of crystallizing the amorphous film to obtain the crystal film, the conductive metal oxide contained in the amorphous film and the crystal film contain it. The conductive metal oxides to be used are the same.

  In addition, it can confirm that a transparent electrode layer has an amorphous film | membrane and a crystalline film by etching a transparent electrode layer. Specifically, the transparent electrode layer is amorphous by comparing the etching rates of the transparent electrode layer, the electrode layer whose whole layer is an amorphous film, and the electrode layer whose whole layer is a crystalline film. It can be confirmed that the film has a film and a crystal film. First, for an electrode layer whose whole layer is an amorphous film and an electrode layer whose whole layer is a crystalline film, after corroding with an acidic etching solution for an arbitrary time in advance, the amount of decrease in film thickness is measured with a step gauge. Keep measuring. Since the crystal film has better acid resistance than the amorphous film, the amount of decrease in the film thickness of the crystal film is smaller than the amount of decrease in the film thickness of the amorphous film. Next, after the transparent electrode layer is corroded with an acidic etching solution for an arbitrary time, the amount of film thickness reduction is measured with a step gauge. The amount of decrease in the thickness of the transparent electrode layer ranges between the amount of decrease in the thickness of the electrode layer whose entire layer is an amorphous film and the amount of decrease in the thickness of the electrode layer whose entire layer is a crystalline film. If it is within the range, the transparent electrode layer is determined to have an amorphous film and a crystalline film.

  The transparent electrode layer is usually an electrode (hole extraction electrode) for extracting holes generated in the photoelectric conversion layer. In the present invention, the transparent electrode layer has transparency, and the transparent electrode layer side is the light receiving surface.

  Conductive metal oxides used for amorphous films and crystal films are conductive and transparent, have an amorphous structure and a crystal structure, and can have low resistance and high acid resistance due to crystallization. There is no particular limitation as long as it can be crystallized by annealing treatment. As such a conductive metal oxide, indium tin oxide (ITO) is preferably used. This is because ITO has conductivity and transparency and has a high work function. Further, when ITO is used, only the layer surface can be crystallized by laser annealing.

The crystal film preferably has a work function comparable to that when the conductive metal oxide has a crystal structure. That is, it is preferable that the surface of the transparent electrode layer is crystallized until it has a work function comparable to that when the conductive metal oxide has a crystal structure. The work function of the crystal film varies depending on the type of conductive metal oxide. For example, when the conductive metal oxide is ITO, the crystal film preferably has a work function of about 4.6 eV to 4.9 eV.
The work function of the crystal film can be obtained by measuring the work function of the surface of the transparent electrode layer on which the crystal film is formed.

The sheet resistance of the transparent electrode layer is preferably 100Ω / □ or less, more preferably 50Ω / □ or less, and particularly preferably 20Ω / □ or less. If the sheet resistance of the transparent electrode layer having an amorphous film and a crystal film is in the above range, sufficient conductivity can be obtained.
In addition, the said sheet resistance is measured based on JIS R1637 (Resistance test method of fine ceramics thin film: Measurement method by 4 probe method) using a surface resistance meter (Loresta MCP: Four-terminal probe) manufactured by Mitsubishi Chemical Corporation. It is the value.

  The film thickness of the transparent electrode layer is preferably in the range of 0.1 nm to 500 nm, and more preferably in the range of 10 nm to 300 nm. If the film thickness is smaller than the above range, the sheet resistance of the transparent electrode layer may become too large, and the generated charge may not be sufficiently transmitted to the external circuit. This is because the rate may decrease and the photoelectric conversion efficiency may decrease.

The thickness of the crystal film in the transparent electrode layer may be such that the transparent electrode layer has flexibility. If the crystal film is thick, the flexibility of the transparent electrode layer may be impaired. Therefore, in order to increase the flexibility of the transparent electrode layer, the thickness of the crystal film is preferably relatively thin.
Further, when the solar cell substrate of the present invention is an organic thin film solar cell substrate, the thickness of the crystal film in the transparent electrode layer may be any thickness that has acid resistance. If the crystal film is thin, desired acid resistance may not be obtained. On the other hand, if the crystal film is thick, the flexibility of the transparent electrode layer is impaired. If the thickness of the crystal film is equal to or greater than a certain level, sufficient acid resistance can be obtained. Therefore, in order to increase the flexibility of the transparent electrode layer, the thickness of the crystal film is preferably relatively thin among the acid-resistant thicknesses.

The total light transmittance of the transparent electrode layer is preferably 85% or more, more preferably 90% or more, and particularly preferably 92% or more. This is because when the total light transmittance of the transparent electrode layer is within the above range, light can be sufficiently transmitted through the transparent electrode layer, and light can be efficiently absorbed by the photoelectric conversion layer.
The total light transmittance is a value measured using an SM color computer (model number: SM-C) manufactured by Suga Test Instruments Co., Ltd. in the visible light region.

The transparent electrode layer may be formed on the entire surface of the transparent substrate, or may be formed in a pattern.
Further, the crystal film 3b may be formed on the entire surface of the amorphous film 3a as illustrated in FIG. 1, and is formed in a pattern on the amorphous film 3a as illustrated in FIG. May be. When the crystal film is formed in a pattern on the amorphous film, for example, an organic thin film solar cell 10 as shown in FIG. 5 is obtained. Even in such a case, the device performance can be improved.

The method for forming the transparent electrode layer will be described later in the section “ D. Method for manufacturing a solar cell substrate”, and will not be described here.

2. Transparent substrate The transparent substrate used in the present invention supports the transparent electrode layer.

It does not specifically limit as a transparent substrate, For example, the transparent flexible material which has flexibility , such as a transparent resin film and an optical resin board, can be mentioned.
This is because the transparent resin film is excellent in workability, is useful in realizing a reduction in manufacturing cost, weight reduction, and a solar cell that is difficult to break, and expands the applicability to various applications such as application to curved surfaces.

When using a flexible material, since there is a concern of water vapor permeation from the transparent substrate surface, it is preferable that a barrier layer is formed on the transparent substrate surface. As the barrier layer, an inorganic thin film such as silicon oxide (SiO ₂ ), silicon oxynitride (SiON), or silicon nitride (SiN) is generally formed by a vacuum film formation method or the like. The barrier layer can be the same as that described in JP-A-2007-73717.

3. Heat Insulating Layer In the present invention, a heat insulating layer 7 may be formed between the transparent substrate 2 and the transparent electrode layer 3 as illustrated in FIG. This is because when the surface of an amorphous film is crystallized by laser annealing to form a crystal film, the heat insulating layer can protect the transparent substrate from heat. When the transparent substrate is a flexible film substrate, a heat insulating layer is preferably formed. Since the heat absorption amount of the film substrate due to laser annealing is reduced by the heat insulating layer, it is possible to prevent the transparent electrode layer from being broken or broken due to the thermal expansion of the film substrate.

The material for forming the heat insulating layer is not particularly limited as long as it has a low thermal conductivity and heat resistance. Preferred examples include silicon oxide (SiO ₂ ) and silicon oxynitride (SiON). Etc. This is because a heat insulating layer using these materials also functions as a barrier layer.

  The thickness of the heat insulating layer may be any thickness that can protect the transparent substrate from the heat during laser annealing, and can be set to about 0.1 μm to 2 μm, for example.

  Examples of the method for forming the heat insulating layer include a vapor deposition method such as a sputtering method and a coating method such as a spin coat method.

4). Auxiliary Electrode In the present invention, as illustrated in FIG. 7, a patterned auxiliary electrode 8 may be formed between the transparent substrate 2 and the transparent electrode layer 3. Even when the sheet resistance of the transparent electrode layer is relatively high, the resistance of the entire laminate of the transparent electrode layer and the auxiliary electrode can be reduced by sufficiently reducing the sheet resistance of the auxiliary electrode. Therefore, the generated power can be collected efficiently.

  The auxiliary electrode used in the present invention is formed in a pattern on a transparent substrate. The auxiliary electrode usually has a lower resistance value than the transparent electrode layer.

  A metal is usually used as a material for forming the auxiliary electrode. Examples of the metal used for the auxiliary electrode include aluminum (Al), gold (Au), silver (Ag), cobalt (Co), nickel (Ni), platinum (Pt), copper (Cu), and titanium (Ti). And conductive metals such as iron (Fe), stainless steel, aluminum alloy, copper alloy, titanium alloy, iron-nickel alloy and nickel-chromium alloy (Ni-Cr). Among the conductive metals described above, those having a relatively low electrical resistance value are preferred. Examples of such a conductive metal include Al, Au, Ag, and Cu.

  In addition, the auxiliary electrode may be a single layer made of the conductive metal as described above, and a conductive metal layer and a contact layer are appropriately laminated in order to improve adhesion to the transparent substrate or the transparent electrode layer. It may be what you did. Examples of the material for forming the contact layer include nickel (Ni), chromium (Cr), nickel chromium (Ni—Cr), titanium (Ti), and tantalum (Ta). The contact layer is laminated on the conductive metal layer in order to obtain adhesion between the desired auxiliary electrode and the transparent substrate or transparent electrode layer, and may be laminated only on one side of the conductive metal layer. You may laminate | stack on both sides of a metal layer.

  Moreover, since the transparent electrode layer is a hole extraction electrode, it is preferable that the metal used for the auxiliary electrode has a high work function. Specifically, Al is preferably used.

  The shape of the auxiliary electrode is not particularly limited as long as it is a pattern, and is appropriately selected depending on desired conductivity, permeability, strength, and the like. For example, the auxiliary electrode may have a mesh-shaped mesh portion and a frame portion arranged around the mesh portion, or may be formed of a mesh-shaped mesh portion.

  When the auxiliary electrode has a mesh portion and a frame portion, the mesh portion and the frame portion may be arranged, for example, when the auxiliary electrode is rectangular, the frame portion may be arranged so as to surround four sides of the mesh portion. Further, it may be arranged so as to surround three sides of the mesh part, may be arranged so as to surround two sides of the mesh part, or may be arranged on one side of the mesh part. Especially, it is preferable that the frame part is arrange | positioned so that the four sides or three sides of a mesh part may be enclosed. This is because current can be collected efficiently.

  The shape of the mesh portion is not particularly limited as long as it is a mesh shape, and is appropriately selected depending on desired conductivity, permeability, strength, and the like. For example, a polygon such as a triangle, a quadrangle, and a hexagon, a circular lattice, and the like can be given. In addition, a polygon or circular “lattice shape” refers to a shape in which polygons or circles are periodically arranged. As the polygonal or circular lattice shape, for example, polygonal openings may be arranged in a straight line or zigzag.

  Especially, it is preferable that the shape of a mesh part is a hexagonal lattice shape or a parallelogram lattice shape. This is because the current flowing through the mesh portion can be prevented from being concentrated locally. In the case of a hexagonal lattice, it is particularly preferable that the hexagonal openings are arranged in a zigzag (so-called honeycomb shape). On the other hand, in the case of a parallelogram lattice, the acute angle of the parallelogram is preferably within the range of 40 ° to 80 °, more preferably within the range of 50 ° to 70 °, and even more preferably 55 ° to 65 °. Within the range of °.

  Since the auxiliary electrode itself basically does not transmit light, light enters the photoelectric conversion layer from the opening of the mesh portion of the auxiliary electrode. Therefore, it is preferable that the opening of the mesh part of the auxiliary electrode is relatively large. Specifically, the ratio of the openings in the mesh portion of the auxiliary electrode is preferably about 50% to 98%, more preferably in the range of 70% to 98%, and still more preferably in the range of 80% to 98%. Within range.

The pitch of the openings of the mesh portion of the auxiliary electrode and the line width of the mesh portion are appropriately selected according to the area of the entire auxiliary electrode and the like.
The line width of the frame portion is appropriately selected according to the area of the entire auxiliary electrode.

  The thickness of the auxiliary electrode is not limited as long as it does not cause a short circuit between the transparent electrode layer and the counter electrode layer. The thickness of the auxiliary electrode is not limited to the thickness of the layer formed between the transparent electrode layer and the counter electrode layer. It is selected as appropriate. For example, in the case of an organic thin film solar cell, the thickness of the auxiliary electrode is appropriately selected according to the thickness of the photoelectric conversion layer, the buffer layer, and the like. Specifically, when the total film thickness of layers formed between the transparent electrode layer and the counter electrode layer (in the case of an organic thin film solar cell, a photoelectric conversion layer, a buffer layer, etc.) is 1, the thickness of the auxiliary electrode is It is preferably 5 or less, more preferably 3 or less, further 2 or less, particularly preferably 1.5 or less, and most preferably 1 or less. This is because if the thickness of the auxiliary electrode is larger than the above range, a short circuit may occur between the electrodes. More specifically, the thickness of the auxiliary electrode is preferably in the range of 100 nm to 1000 nm, more preferably in the range of 200 nm to 800 nm, further in the range of 200 nm to 500 nm, and particularly in the range of 200 nm to 400 nm. It is preferable. This is because if the thickness of the auxiliary electrode is thinner than the above range, the sheet resistance of the auxiliary electrode may become too large. Moreover, it is because there exists a possibility that a short circuit may arise between electrodes when the thickness of an auxiliary electrode is thicker than the said range.

Among them, when the solar cell substrate of the present invention is an organic thin film solar cell substrate, the photoelectric conversion layer is formed on the transparent electrode layer by a method capable of adjusting the thickness mainly in accordance with the coating amount. When formed, the thickness of the auxiliary electrode is preferably in the range of 200 nm to 300 nm. When the photoelectric conversion layer is formed on the transparent electrode layer by a method capable of adjusting the thickness mainly in accordance with the coating amount, if the thickness of the auxiliary electrode is larger than the above range, the mesh portion or the frame of the auxiliary electrode It becomes difficult to cover the edge of the part, and a short circuit is likely to occur between the electrodes. Further, if the thickness of the auxiliary electrode is larger than the above range, the photoelectric conversion layer may be formed thicker than the desired thickness due to surface tension. If the thickness of the photoelectric conversion layer is too thick, it exceeds the electron diffusion length and the hole diffusion length, and the conversion efficiency decreases. It is preferable to adjust the thickness of the auxiliary electrode so that the photoelectric conversion layer is not formed thicker than desired due to surface tension. In particular, since it is known that the distance that holes and electrons can move in the photoelectric conversion layer is about 100 nm, the auxiliary electrode is formed so that the photoelectric conversion layer is not formed thicker than the desired thickness due to surface tension. It is preferable to adjust the thickness.
On the other hand, when the photoelectric conversion layer is formed by, for example, a spin coating method, a uniform film is formed by centrifugal force, so that the edge of the auxiliary electrode can be covered even if the auxiliary electrode is relatively thick. In the case of the spin coating method, the thickness can be adjusted by the number of rotations, so that a uniform film can be obtained even if the auxiliary electrode is relatively thick.
Therefore, when the photoelectric conversion layer is formed mainly by a method capable of adjusting the thickness according to the coating amount, the above range is particularly preferable.

The sheet resistance of the auxiliary electrode may be lower than that of the transparent electrode layer. Specifically, the sheet resistance of the auxiliary electrode is preferably 5Ω / □ or less, more preferably 3Ω / □ or less, more preferably 1Ω / □ or less, particularly preferably 0.5Ω / □ or less, and 0.1Ω. Most preferably, it is less than / □. This is because if the sheet resistance of the auxiliary electrode is larger than the above range, desired power generation efficiency may not be obtained.
In addition, the said sheet resistance is measured based on JIS R1637 (Resistance test method of fine ceramics thin film: Measurement method by 4 probe method) using a surface resistance meter (Loresta MCP: Four-terminal probe) manufactured by Mitsubishi Chemical Corporation. It is the value.

  The method for forming the auxiliary electrode is not particularly limited, and examples thereof include a method of forming a metal thin film on the entire surface and then patterning it into a mesh shape, a method of directly forming a mesh-like conductor, and the like. These methods are appropriately selected depending on the auxiliary electrode forming material, configuration, and the like.

The method for forming the metal thin film is preferably a vacuum film forming method such as a vacuum deposition method, a sputtering method, or an ion plating method. That is, the auxiliary electrode is preferably a metal thin film formed by a vacuum film forming method. The metal species formed by the vacuum film formation method has less inclusions than the plating film and can reduce the specific resistance, and can also reduce the specific resistance as compared with those formed using Ag paste or the like. Further, a vacuum film formation method is also suitable as a method for forming a metal thin film having a thickness of 1 μm or less, preferably 500 nm or less, with a precise thickness and a uniform thickness.
The method for patterning the metal thin film is not particularly limited as long as it can be accurately formed into a desired pattern, and examples thereof include a photoetching method.

5. Applications The solar cell substrate of the present invention is used for solar cells in general, and is particularly preferably used for organic thin-film solar cells. Since the organic thin film solar cell has a relatively high resistance to bending, it is suitable as a flexible solar cell, and is suitable for the solar cell substrate of the present invention.
In the present invention, the resistance of the transparent electrode layer can be reduced, damage to the transparent electrode layer due to acid can be suppressed, and electrical characteristics can be improved.

B. Next, the organic thin film solar cell of the present invention will be described.
The organic thin film solar cell of the present invention includes a transparent substrate, a transparent electrode layer formed on the transparent substrate, a buffer layer formed on the transparent electrode layer, and a photoelectric conversion layer formed on the buffer layer. And a counter electrode layer formed on the photoelectric conversion layer, wherein the transparent electrode layer is an amorphous material formed on the transparent substrate and containing a conductive metal oxide. And a crystalline film formed on the amorphous film and containing the same conductive metal oxide as the conductive metal oxide contained in the amorphous film. It is. That is, the organic thin-film solar cell of the present invention includes the above-described solar cell substrate, and a buffer layer is formed on the transparent electrode layer.

The organic thin-film solar cell of this invention is demonstrated referring drawings.
FIG. 2 is a schematic cross-sectional view showing an example of the organic thin film solar cell of the present invention. In the example shown in FIG. 2, the organic thin-film solar cell 10 includes a solar cell substrate 1, a buffer layer 4 formed on the transparent electrode layer 3 of the solar cell substrate 1, and a photoelectric film formed on the buffer layer 4. It has a conversion layer 5 and a counter electrode layer 6 formed on the photoelectric conversion layer 5. The solar cell substrate 1 has a transparent substrate 2 and a transparent electrode layer 3 formed on the transparent substrate 2 and containing a conductive metal oxide. The transparent electrode layer 3 is formed on the transparent substrate 2 and is formed on the amorphous film 3a containing the conductive metal oxide and in contact with the buffer layer 4 on the amorphous film 3a. And a crystal film 3b containing. The amorphous film 3a and the crystal film 3b contain the same conductive metal oxide, and the crystal film 3b is obtained by crystallizing the surface of the amorphous film 3a.

  According to the present invention, since the solar cell substrate is provided, a transparent electrode layer having both low resistance and flexibility can be obtained. Further, when the transparent substrate is a flexible film substrate, the transparent electrode layer has an amorphous film and is excellent in flexibility, so that a high-performance flexible organic thin film solar cell can be obtained. Is possible.

  Further, according to the present invention, since the solar cell substrate is included, when the buffer layer contains a material exhibiting acidity, it is due to the influence of the acid contained in the buffer layer when the buffer layer is formed and when the solar cell is used. It is possible to reduce damage to the transparent electrode layer. Thereby, it is possible to suppress the deterioration of the electrical characteristics of the transparent electrode layer and to improve the reliability of the organic thin film solar cell.

  The transparent substrate, the transparent electrode layer, the heat insulating layer, and the auxiliary electrode have been described in detail in the section “A. Substrate for Solar Cell” above, and thus description thereof is omitted here. Hereinafter, the other structure in the organic thin-film solar cell of this invention is demonstrated.

1. Buffer layer The buffer layer in the present invention is formed directly on the transparent electrode layer, and is a layer provided so that the charge can be easily taken out from the photoelectric conversion layer to the transparent electrode layer. Since the transparent electrode layer is usually a hole extraction electrode, the buffer layer is preferably a layer provided so that holes can be easily extracted from the photoelectric conversion layer to the transparent electrode layer. Since the hole extraction efficiency from the photoelectric conversion layer to the transparent electrode layer is increased by the buffer layer, the photoelectric conversion efficiency can be improved.

  The material used for the buffer layer is not particularly limited as long as it is a material that stabilizes the extraction of holes from the photoelectric conversion layer to the transparent electrode layer. Specifically, doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, polyacetylene, conductive organic compounds such as triphenyldiamine (TPD), or electron donation such as tetrathiofulvalene, tetramethylphenylenediamine, etc. An organic material that forms a charge transfer complex composed of an organic compound and an electron-accepting compound such as tetracyanoquinodimethane and tetracyanoethylene. Among these, polyethylene dioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) is particularly preferable.

Moreover, it is preferable that the material used for a buffer layer is what shows acidity. Specifically, a material having a pH of less than 7 when used as a coating solution is preferable. As described above, when the buffer layer contains a material exhibiting acidity, the damage of the transparent electrode layer due to the influence of the acid contained in the buffer layer can be reduced, so the configuration of the present invention is useful. Examples of the material showing acidity include PEDOT / PSS and doped polyaniline, and PEDOT / PSS is particularly preferably used.
That is, the buffer layer preferably contains PEDOT / PSS. PEDOT / PSS is a material that exhibits acidity in the coating liquid for forming the buffer layer, and also exhibits acidity in the buffer layer when the buffer layer absorbs moisture. Therefore, it is useful that the transparent electrode layer has a crystal film on the buffer layer side as in the configuration of the present invention.

  The thickness of the buffer layer is preferably in the range of 10 nm to 200 nm.

In addition, since the formation method of a buffer layer is described in the term of " E. manufacturing method of an organic thin film solar cell" mentioned later, description here is abbreviate | omitted.

2. Photoelectric Conversion Layer The photoelectric conversion layer used in the present invention is formed between the transparent electrode layer and the counter electrode layer. The “photoelectric conversion layer” refers to a member that contributes to charge separation of the organic thin film solar cell and has a function of transporting generated electrons and holes toward electrodes in opposite directions.

  The photoelectric conversion layer may be a single layer having both an electron-accepting function and an electron-donating function (first aspect), or an electron-accepting layer having an electron-accepting function and an electron-donating function. A layer in which an electron donating layer having n is laminated may be used (second embodiment). Hereinafter, each aspect will be described.

(1) 1st aspect The 1st aspect of the photoelectric converting layer in this invention is a single layer which has both an electron-accepting function and an electron-donating function, and contains an electron-donating material and an electron-accepting material It is. In this photoelectric conversion layer, since charge separation occurs using a pn junction formed in the photoelectric conversion layer, it functions as a photoelectric conversion layer alone.

The electron donating material is not particularly limited as long as it has a function as an electron donor, but it is preferable that the material can be formed by a wet coating method. A polymer material is preferred.
The conductive polymer is a so-called π-conjugated polymer, which is composed of a π-conjugated system in which double bonds or triple bonds containing carbon-carbon or hetero atoms are alternately linked to single bonds, and exhibits semiconducting properties. It is. In the conductive polymer material, π conjugation is developed in the polymer main chain, so that charge transport in the main chain direction is basically advantageous. In addition, since the electron transfer mechanism of the conductive polymer is mainly hopping conduction between molecules by π stacking, it is advantageous not only for the main chain direction of the polymer but also for the charge transport in the film thickness direction of the photoelectric conversion layer. is there. Furthermore, since the conductive polymer material can be easily formed by a wet coating method using a coating solution in which the conductive polymer material is dissolved or dispersed in a solvent, a large-area organic thin film solar cell Can be manufactured at low cost without requiring expensive equipment.

  Examples of the electron-donating conductive polymer material include polyphenylene, polyphenylene vinylene, polysilane, polythiophene, polycarbazole, polyvinyl carbazole, porphyrin, polyacetylene, polypyrrole, polyaniline, polyfluorene, polyvinyl pyrene, polyvinyl anthracene, and derivatives thereof. And copolymers thereof, or phthalocyanine-containing polymers, carbazole-containing polymers, organometallic polymers, and the like.

Among the above, thiophene-fluorene copolymer, polyalkylthiophene, phenylene ethynylene-phenylene vinylene copolymer, phenylene ethynylene-thiophene copolymer, phenylene ethynylene-fluorene copolymer, fluorene-phenylene vinylene copolymer A thiophene-phenylene vinylene copolymer is preferably used. This is because the energy level difference is appropriate for many electron-accepting materials.
For example, a phenylene ethynylene-phenylene vinylene copolymer (Poly [1,4-phenyleneethynylene-1,4- (2,5-dioctadodecyloxyphenylene) -1,4-phenyleneethene-1,2-diyl-1,4- ( 2,5-dioctadodecyloxyphenylene) ethene-1,2-diyl]) is described in detail in Macromolecules, 35, 3825 (2002) and Micromol. Chem. Phys., 202, 2712 (2001).

  Further, the electron-accepting material is not particularly limited as long as it has a function as an electron acceptor, but it is preferable that it can be formed into a film by a wet coating method. A conductive polymer material is preferable. This is because the conductive polymer material has the advantages as described above.

Examples of the electron-accepting conductive polymer material include polyphenylene vinylene, polyfluorene, and derivatives thereof, and copolymers thereof, or carbon nanotubes, fullerene derivatives, CN group or CF ₃ group-containing polymers, and the like. -CF ₃ substituted polymer, and the like. Specific examples of the polyphenylene vinylene derivative include CN-PPV (Poly [2-Methoxy-5- (2′-ethylhexyloxy) -1,4- (1-cyanovinylene) phenylene]), MEH-CN-PPV (Poly [2 -Methoxy-5- (2′-ethylhexyloxy) -1,4- (1-cyanovinylene) phenylene]) and the like.

  Further, an electron accepting material doped with an electron donating compound, an electron donating material doped with an electron accepting compound, or the like can also be used. Among these, a conductive polymer material doped with an electron donating compound or an electron accepting compound is preferably used. Conductive polymer materials are basically advantageous in charge transport in the direction of the main chain because of the development of π conjugation in the polymer main chain, and are doped with electron-donating compounds and electron-accepting compounds. This is because electric charges are generated in the π-conjugated main chain, and the electrical conductivity can be greatly increased.

Examples of the electron-accepting conductive polymer material doped with the electron-donating compound include the above-described electron-accepting conductive polymer material. As the electron-donating compound to be doped, for example, a Lewis base such as an alkali metal such as Li, K, Ca, or Cs or an alkaline earth metal can be used. The Lewis base acts as an electron donor.
Examples of the electron-donating conductive polymer material doped with the electron-accepting compound include the above-described electron-donating conductive polymer material. As the electron-accepting compound to be doped, for example, a Lewis acid such as FeCl ₃ (III), AlCl ₃ , AlBr ₃ , AsF ₆ or a halogen compound can be used. In addition, Lewis acid acts as an electron acceptor.

  As the film thickness of the photoelectric conversion layer, the film thickness generally employed in bulk heterojunction organic thin film solar cells can be employed. Specifically, it can be set within a range of 0.2 nm to 3000 nm, and preferably within a range of 1 nm to 600 nm. This is because when the film thickness is thicker than the above range, the volume resistance in the photoelectric conversion layer may increase. On the other hand, if the film thickness is thinner than the above range, light may not be sufficiently absorbed.

  The mixing ratio of the electron-donating material and the electron-accepting material is appropriately adjusted to an optimal mixing ratio depending on the type of material used.

  The method for forming the photoelectric conversion layer is not particularly limited as long as it can be uniformly formed in a predetermined film thickness, but a wet coating method is preferably used. This is because if the wet coating method is used, the photoelectric conversion layer can be formed in the air, and the cost can be reduced and the area can be easily increased.

The method for applying the photoelectric conversion layer coating solution is not particularly limited as long as it can uniformly apply the photoelectric conversion layer coating solution. For example, a die coating method, a spin coating method, a dip coating method, and the like. Examples thereof include a coating method, a roll coating method, a bead coating method, a spray coating method, a bar coating method, a gravure coating method, an ink jet method, a screen printing method, and an offset printing method.
Especially, it is preferable that the application | coating method of the coating liquid for photoelectric conversion layers is a method which can adjust thickness mainly according to the application amount. Methods that can adjust the thickness mainly according to the coating amount include, for example, a die coating method, a bead coating method, a bar coating method, a gravure coating method, an ink jet method, a screen printing method, and an offset printing method. Can be mentioned. The printing method is suitable for increasing the area of the organic thin film solar cell.

After application of the coating liquid for photoelectric conversion layer, a drying treatment for drying the formed coating film may be performed. It is because productivity can be improved by removing the solvent etc. which are contained in the coating liquid for photoelectric conversion layers at an early stage.
As a drying method, for example, a general method such as heat drying, air drying, vacuum drying, infrared heat drying, or the like can be used.

(2) Second Aspect In the second aspect of the photoelectric conversion layer in the present invention, an electron accepting layer having an electron accepting function and an electron donating layer having an electron donating function are laminated. Hereinafter, the electron-accepting layer and the electron-donating layer will be described.

(Electron-accepting layer)
The electron-accepting layer used in this embodiment has an electron-accepting function and contains an electron-accepting material.

  The electron-accepting material is not particularly limited as long as it has a function as an electron acceptor, but is preferably a material that can be formed into a film by a wet coating method. A polymer material is preferred. This is because the conductive polymer material has the advantages as described above. Specific examples include the same electron-accepting conductive polymer materials used for the photoelectric conversion layer of the first aspect.

  As the film thickness of the electron-accepting layer, a film thickness generally employed in a bilayer type organic thin film solar cell can be employed. Specifically, it can be set within a range of 0.1 nm to 1500 nm, and preferably within a range of 1 nm to 300 nm. This is because if the film thickness is larger than the above range, the volume resistance in the electron-accepting layer may be increased. On the other hand, if the film thickness is thinner than the above range, light may not be sufficiently absorbed.

  The method for forming the electron-accepting layer can be the same as the method for forming the photoelectric conversion layer of the first aspect.

(Electron donating layer)
The electron donating layer used in this embodiment has an electron donating function and contains an electron donating material.

  The electron donating material is not particularly limited as long as it has a function as an electron donor, but it is preferable that the material can be formed by a wet coating method. A polymer material is preferred. This is because the conductive polymer material has the advantages as described above. Specific examples include the same electron donating conductive polymer materials used for the photoelectric conversion layer of the first aspect.

  As a film thickness of the electron donating layer, a film thickness generally employed in a bilayer type organic thin film solar cell can be employed. Specifically, it can be set within a range of 0.1 nm to 1500 nm, and preferably within a range of 1 nm to 300 nm. This is because if the film thickness is larger than the above range, the volume resistance in the electron donating layer may be increased. On the other hand, if the film thickness is thinner than the above range, light may not be sufficiently absorbed.

  The method for forming the electron donating layer can be the same as the method for forming the photoelectric conversion layer of the first aspect.

3. Counter Electrode Layer The counter electrode layer used in the present invention is an electrode facing the transparent electrode layer. Usually, the counter electrode layer is an electrode (electron extraction electrode) for extracting electrons generated in the photoelectric conversion layer. In the present invention, since the transparent electrode layer side becomes the light receiving surface, the counter electrode layer may or may not have transparency.

The material for forming the counter electrode layer is not particularly limited as long as it has conductivity. However, since the counter electrode layer is an electron extraction electrode, it preferably has a low work function. Specific examples of the material having a low work function include Li, In, Al, Ag, Ca, Mg, Sm, Tb, Yb, Zr, and LiF. The counter electrode layer may be a single layer or may be laminated using materials having different work functions. Examples of the counter electrode layer in which different materials are laminated include those in which any one of Ca, LiF, LiCa, MoO ₃ or VO ₅ and any one of Al or Ag are laminated.

  When the counter electrode layer is a single layer, the thickness of the counter electrode layer is within a range of 0.1 nm to 500 nm, particularly 1 nm to 300 nm. It is preferable to be within the range. When the film thickness is thinner than the above range, the sheet resistance of the counter electrode layer becomes too large, and the generated charge may not be sufficiently transmitted to the external circuit.

The counter electrode layer may be formed on the entire surface of the photoelectric conversion layer, or may be formed in a pattern.
As a method for forming the counter electrode layer, a general electrode forming method can be used. For example, a vacuum evaporation method or a pattern evaporation method using a metal mask can be used.

4). Electron Extraction Layer In the present invention, an electron extraction layer may be formed between the photoelectric conversion layer and the counter electrode layer. The electron extraction layer is a layer provided so that electrons can be easily extracted from the photoelectric conversion layer to the electron extraction electrode. Thereby, since the electron extraction efficiency from the photoelectric conversion layer to the electron extraction electrode is increased, the photoelectric conversion efficiency can be improved.

  The material used for the electron extraction layer is not particularly limited as long as it is a material that stabilizes the extraction of electrons from the photoelectric conversion layer to the electron extraction electrode. Specifically, doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, polyacetylene, conductive organic compounds such as triphenyldiamine (TPD), or electron donation such as tetrathiofulvalene, tetramethylphenylenediamine, etc. An organic material that forms a charge transfer complex composed of an organic compound and an electron-accepting compound such as tetracyanoquinodimethane and tetracyanoethylene. Moreover, the metal dope layer with an alkali metal or alkaline-earth metal is mentioned. Suitable materials include bathocuproin (BCP) or bathophenantrone (Bphen) and metal doped layers such as Li, Cs, Ba, Sr.

5. Other Configurations The organic thin film solar cell of the present invention may have constituent members to be described later as necessary in addition to the constituent members described above. For example, the organic thin film solar cell of the present invention is a functional layer such as a protective sheet, a filler layer, a barrier layer, a protective hard coat layer, a strength support layer, an antifouling layer, a high light reflection layer, a light containment layer, a sealing material layer, etc. You may have. In addition, an adhesive layer may be formed between the functional layers depending on the layer configuration.
These functional layers can be the same as those described in JP-A-2007-73717.

C. Organic thin film solar cell module The organic thin film solar cell module of the present invention is characterized in that a plurality of the above organic thin film solar cells are connected in series or in parallel.
The connection of the plurality of organic thin-film solar cells is not limited as long as a desired electromotive force can be obtained, may be only in series, may be only in parallel, or may be a combination of series and parallel.
Since the organic thin film solar cell is described in detail in the section “ B. Organic thin film solar cell”, description thereof is omitted here.

D. Next, a method for manufacturing a solar cell substrate of the present invention will be described.
In the method for manufacturing a solar cell substrate of the present invention, an amorphous film containing a conductive metal oxide is formed on a transparent substrate, and then the surface of the amorphous film is crystallized by laser annealing to form a crystalline film. It has a transparent electrode layer forming step of forming and obtaining a transparent electrode layer having the amorphous film and the crystal film.

A method for producing a solar cell substrate of the present invention will be described with reference to the drawings.
8A to 8B are process diagrams showing an example of a method for producing a solar cell substrate of the present invention. First, as shown in FIG. 8A, an amorphous film 3 a containing a conductive metal oxide is formed on the transparent substrate 2. Next, as shown in FIG. 8B, the surface of the amorphous film 3a is crystallized by irradiating the laser 11 to form a crystal film 3b. Since the crystal film 3b is obtained by crystallizing the surface of the amorphous film 3a, the crystal film 3b has a lower resistance and superior acid resistance than the amorphous film 3a. Thereby, the transparent electrode layer 3 having the amorphous film 3a and the crystal film 3b is obtained (transparent electrode layer forming step).

  According to the present invention, since the surface of the amorphous film is crystallized by laser annealing to form a crystalline film having a resistance lower than that of the amorphous film, it is possible to obtain a transparent electrode layer with good conductivity. Moreover, since only the surface of the amorphous film is crystallized by laser annealing to form a crystal film, the transparent electrode layer has an amorphous film having excellent flexibility, and the transparent electrode layer having flexibility It is possible to obtain Therefore, in the present invention, a transparent electrode layer having both low resistance and flexibility can be formed.

  Further, according to the present invention, since laser annealing is used, heat is instantaneously applied only to the surface of the amorphous film, and the heat effect on the transparent substrate is suppressed, so a transparent substrate with low heat resistance is used. It is possible. Therefore, a flexible film substrate can be used as the transparent substrate. As described above, in the present invention, a flexible transparent electrode layer can be obtained, and a flexible film substrate can be used as the transparent substrate. Therefore, a high-performance flexible solar cell can be manufactured. Is possible.

Furthermore, according to the present invention, since the surface of the amorphous film is crystallized by laser annealing to form a crystalline film, for example, when an organic thin film solar cell 10 as shown in FIG. The buffer layer 4 is not directly formed. Therefore, when the buffer layer is formed using an acidic material, the amorphous film is protected by the crystal film, and it is possible to reduce the damage of the transparent electrode layer due to the influence of the acid contained in the buffer layer. is there. Thereby, it becomes possible to obtain an organic thin film solar cell with high reliability.
Therefore, in the present invention, it is possible to produce an organic thin-film solar cell excellent in electrical performance by reducing the resistance of the transparent electrode layer and suppressing damage to the transparent electrode layer due to acid.

  Further, according to the present invention, the surface of the amorphous film is crystallized by laser annealing to form a crystalline film having a work function different from that of the amorphous film, and thus, for example, an organic thin film solar cell 20 as shown in FIG. In this case, it is possible to adjust the work function at the interface between the transparent electrode layer 3 and the organic layer 15 to improve the charge mobility.

  Hereinafter, each process in the manufacturing method of the board | substrate for solar cells of this invention is demonstrated.

1. Transparent electrode layer forming step In the transparent electrode layer forming step in the present invention, an amorphous film containing a conductive metal oxide is formed on a transparent substrate, and then the surface of the amorphous film is crystallized by laser annealing. This is a step of forming a crystal film and obtaining a transparent electrode layer having the amorphous film and the crystal film.

  The method for forming the amorphous film is not particularly limited as long as it is a method capable of forming a film having an amorphous structure. For example, a sputtering method, a vacuum evaporation method, an ion plating method, a thermal CVD method is used. And plasma CVD method. Among these, the sputtering method is preferable.

After the formation of the amorphous film, only the surface of the amorphous film is crystallized by laser annealing to form a crystalline film.
An excimer laser can be used as the laser. Examples of the excimer laser include a KrF excimer laser (wavelength 248 nm), an ArF excimer laser (wavelength 193 nm), and the like. Among these, a KrF excimer laser having a wavelength of 248 nm is preferably used because of its versatility.
The laser irradiation conditions are appropriately adjusted according to the damage to the amorphous film and the crystallinity of the irradiated portion. For example, if the laser output is too large, the amorphous film may be damaged significantly, and if the laser output is small, crystallization becomes difficult. Specifically, the output of the laser can be in a range of ^{70mJ / cm 2 ~110mJ / cm 2} , the range among them of ^{80mJ / cm 2 ~100mJ / cm 2} , particularly 85mJ / cm ² ~95mJ / cm ² It is preferable to be within the range.
The atmosphere in laser annealing is usually an air atmosphere.

  The laser may be applied to the entire surface of the amorphous film, or the amorphous film may be irradiated in a pattern. When the amorphous film is irradiated with laser in a pattern, the crystal film 3b is formed in a pattern on the amorphous film 3a as illustrated in FIG. Even in such a case, the device performance can be improved.

  The degree to which the amorphous film surface is crystallized by laser annealing is appropriately adjusted in consideration of the conductivity, flexibility, and acid resistance of the obtained transparent electrode layer. The surface of the amorphous film is preferably crystallized until the crystal film obtained by crystallization has a work function comparable to that when the conductive metal oxide has a crystal structure. . If the progress of crystallization is insufficient, the desired acid resistance may not be obtained. On the other hand, if crystallization proceeds excessively, the flexibility of the transparent electrode layer is impaired. When the crystallization progresses to a certain extent, the work function hardly changes. Therefore, in order to obtain high flexibility, the laser annealing may be stopped immediately after the crystal film has a work function comparable to that when the conductive metal oxide has a crystal structure. preferable.

  Note that the surface of the amorphous film is crystallized can be confirmed by etching the film after laser annealing. Specifically, by comparing the etching rates of the film after laser annealing, the film whose entire layer is an amorphous film, and the film whose entire layer is a crystalline film, the surface of the amorphous film is It can be confirmed that it is crystallized. First, a film whose entire layer is an amorphous film and a film whose entire layer is a crystalline film are previously corroded with an acidic etchant for an arbitrary time, and then the amount of decrease in film thickness is measured with a step gauge. Keep it. Next, after the laser-annealed film is corroded with an acidic etching solution for an arbitrary time, the reduction amount of the film thickness is measured with a step gauge. The amount of film thickness reduction after laser annealing is in the range between the amount of film thickness reduction where the entire layer is an amorphous film and the amount of film thickness reduction where the entire layer is a crystalline film. If it is within the range, it is determined that only the surface of the amorphous film is crystallized.

  The other points of the conductive metal oxide, the amorphous film, the crystal film, and the transparent electrode layer are described in the above section “A. Solar Cell Substrate”, and thus the description thereof is omitted here.

2. Other process In this invention, you may perform the heat insulation layer formation process which forms a heat insulation layer on a transparent substrate before a transparent electrode layer formation process. This is because the transparent substrate can be protected from heat by the heat insulating layer during the laser annealing. When the transparent substrate is a flexible film substrate, it is preferable to perform a heat insulating layer forming step. In addition, since it described in the term of the said "A. solar cell substrate" about the heat insulation layer, description here is abbreviate | omitted.

3. Applications The method for producing a solar cell substrate of the present invention is a method for producing a solar cell substrate used for all solar cells, and particularly preferably a method for producing an organic thin film solar cell substrate. In the present invention, as described above, it is possible to reduce the resistance of the transparent electrode layer, suppress damage to the transparent electrode layer due to acid, and improve electrical characteristics.

E. Next, the manufacturing method of the organic thin film solar cell of this invention is demonstrated.
The organic thin film solar cell manufacturing method of the present invention is formed on a transparent substrate, a transparent electrode layer formed on the transparent substrate, a buffer layer formed on the transparent electrode layer, and the buffer layer. A method for producing an organic thin film solar cell having a photoelectric conversion layer and a counter electrode layer formed on the photoelectric conversion layer, wherein an amorphous film containing a conductive metal oxide is formed on a transparent substrate Thereafter, the surface of the amorphous film is crystallized by laser annealing to form a crystal film, and a transparent electrode layer forming step for obtaining the amorphous film and the transparent electrode layer having the crystal film is formed on the transparent electrode layer. And a buffer layer forming step of forming a buffer layer by applying a coating solution for forming a buffer layer. That is, the method for producing an organic thin-film solar cell of the present invention applies a buffer layer-forming coating solution on a transparent electrode layer using a solar cell substrate produced by the above-described method for producing a solar cell substrate. This is a method for forming a buffer layer.

The manufacturing method of the organic thin film solar cell of this invention is demonstrated referring drawings.
9A to 9E are process diagrams showing an example of a method for producing an organic thin film solar cell of the present invention. First, as shown in FIG. 9A, an amorphous film 3 a containing a conductive metal oxide is formed on the transparent substrate 2. Next, as shown in FIG. 9B, the surface of the amorphous film 3a is crystallized by irradiating the laser 11 to form a crystal film 3b. Since the crystal film 3b is obtained by crystallizing the surface of the amorphous film 3a, the resistance is lower than that of the amorphous film 3a. Thereby, the transparent electrode layer 3 having the amorphous film 3a and the crystal film 3b is obtained (transparent electrode layer forming step). Next, as shown in FIG. 9C, a buffer layer forming coating solution is applied on the crystal film 3b of the transparent electrode layer 3 to form the buffer layer 4 (buffer layer forming step). Next, as illustrated in FIG. 9D, the photoelectric conversion layer 5 is formed on the buffer layer 4. Subsequently, as illustrated in FIG. 9E, the counter electrode layer 6 is formed on the photoelectric conversion layer 5.

  According to the present invention, since the solar cell substrate manufactured by the above-described method for manufacturing a solar cell substrate is used, a transparent electrode layer having both low resistance and flexibility can be formed. In addition, since the above-described solar cell substrate is used, a transparent substrate with low heat resistance can be used, and a flexible film substrate can be used as the transparent substrate. Therefore, it is possible to manufacture a high performance flexible organic thin film solar cell.

  Furthermore, according to the present invention, since the solar cell substrate described above is used, when the buffer layer is formed using a buffer layer forming coating solution exhibiting acidity, the transparent electrode due to the influence of the acid contained in the buffer layer Damage to the layer can be reduced, and a highly reliable organic thin-film solar cell can be obtained.

In addition, since it described in the said " D. manufacturing method of the board | substrate for solar cells" about the transparent electrode layer formation process, description here is abbreviate | omitted. Hereinafter, the other process in the manufacturing method of the organic thin-film solar cell of this invention is demonstrated.

1. Buffer Layer Forming Step The buffer layer forming step in the present invention is a step of forming a buffer layer by applying a buffer layer forming coating solution on the transparent electrode layer.

The coating solution for forming the buffer layer can be prepared by dissolving or dispersing the materials described in the section of the buffer layer in “ B. Organic thin film solar cell” in a solvent.
The solvent is not particularly limited as long as it can dissolve or disperse the above materials, and examples thereof include water.
In addition to the above materials and solvents, various additives can be added to the buffer layer forming coating solution.

It is preferable that the buffer layer forming coating solution is acidic. Specifically, the pH of the buffer layer forming coating solution is preferably less than 7. As described above, when the buffer layer forming coating solution is acidic, damage to the transparent electrode layer due to the influence of the acid can be reduced, and therefore the configuration of the present invention is useful. Examples of the buffer layer forming coating solution exhibiting acidity include those containing PEDOT / PSS and those containing polyaniline as the main component, and PEDOT / PSS is particularly preferably used.
That is, it is preferable that the buffer layer forming coating solution contains PEDOT / PSS. PEDOT / PSS is a material that exhibits acidity in the coating liquid for forming the buffer layer, and also exhibits acidity in the buffer layer when the buffer layer absorbs moisture. Therefore, it is useful to produce a transparent electrode layer by crystallizing the surface of an amorphous film by laser annealing to form a crystal film as in the configuration of the present invention.

  The method for applying the buffer layer forming coating solution is not particularly limited as long as it can be applied on the transparent electrode layer. For example, spin coating, die coating, casting, dip coating , Bar coating method, blade coating method, roll coating method, spray coating method, flexographic printing method, gravure printing method, offset printing method, screen printing method, inkjet method and the like.

2. Other Steps In the present invention, after the buffer layer forming step, a photoelectric conversion layer forming step for forming a photoelectric conversion layer on the buffer layer, a counter electrode layer forming step for forming a counter electrode layer on the photoelectric conversion layer, and the like are performed. be able to. Since the photoelectric conversion layer and the counter electrode layer are described in the above section “ B. Organic thin film solar cell”, description thereof is omitted here.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example 1]
(Production of organic thin film solar cells)
An ITO layer having a thickness of 150 nm and a surface resistance of 60Ω / □ was formed on a PET film having a thickness of 125 μm by sputtering. Next, laser annealing using an excimer laser with an output of 90 mJ / cm ² was performed on the ITO layer to obtain an ITO layer in which only the surface was crystallized.

Next, a conductive polymer paste (poly- (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid dispersion) is formed on the ITO layer by spin coating, and then at 100 ° C. for 10 minutes. Dried to form a buffer layer.
Next, polythiophene (P3HT: poly (3-hexylthiophene-2,5-diyl), manufactured by Aldrich) and C60PCBM ([6,6] -phenyl-C61-butyric acid mettric ester, manufactured by Nano-C) It was dissolved in benzene to prepare a coating solution for a photoelectric conversion layer having a solid content concentration of 1.4 wt%. Subsequently, after applying the coating liquid for photoelectric conversion layers on the said buffer layer by the spin coat method, it was dried at 100 degreeC for 10 minute (s), and the photoelectric converting layer was formed.
Next, calcium and aluminum were formed on the photoelectric conversion layer by a vacuum deposition method to obtain a metal electrode.

(Evaluation of ITO layer)
First, the crystallinity of the ITO layer before laser annealing was evaluated by X-ray diffraction measurement. The ITO layer before laser annealing was an amorphous film.
Next, the crystallinity of the ITO layer after laser annealing was evaluated. When the work function of the ITO layer surface before and after laser annealing was measured, the work function of the ITO layer surface before laser annealing was 5.3 eV, and the work function of the ITO layer surface after laser annealing was 4.7 eV. This confirmed that the ITO layer surface was crystallized.
Further, it was examined that only the surface of the ITO layer after laser annealing was crystallized. First, an ITO layer having a thickness of 150 nm was formed on a PET film having a thickness of 125 μm by an unheated sputtering method as an ITO layer whose entire layer was an amorphous film. Further, an ITO layer having a thickness of 150 nm was formed on a PET film having a thickness of 125 μm by a substrate heating sputtering method as an ITO layer whose entire layer was a crystal film. The crystallinity of each ITO layer was evaluated by X-ray diffraction measurement and confirmed to be an amorphous film and a crystalline film, respectively. Next, the ITO layer after laser annealing, the ITO layer whose whole layer is an amorphous film, and the ITO layer whose whole layer is a crystalline film are corroded with an acidic etching solution for 5 minutes, and then the amount of decrease in film thickness Was measured with a step gauge. The amount of film thickness reduction in the ITO layer after laser annealing is larger than the amount of film thickness reduction in the ITO layer where the whole layer is a crystalline film, and the amount of film thickness reduction in the ITO layer where the whole layer is an amorphous film. Less than. Thereby, it was determined that only the surface of the ITO layer was crystallized.
In addition, in the etching of the ITO layer, the reduction amount of the film thickness in the ITO layer after laser annealing is smaller than the reduction amount of the film thickness in the ITO layer in which the whole layer is an amorphous film. It was found that the damage of the ITO layer due to the acid can be reduced by crystallizing the surface.

[Example 2]
An organic thin film as in Example 1 except that a 1 μm thick SiO ₂ layer (heat insulation layer) is formed on a 125 μm thick PET film by spin coating and an ITO layer is formed on the SiO ₂ layer by sputtering. A solar cell was produced.

[Comparative Example 1]
An organic thin film solar cell was produced in the same manner as in Example 1 except that laser annealing was not performed.

[Evaluation]
100 mW / cm ² by solar simulator, A. M.M. The solar cell performance was evaluated under the condition of 1.5G. The organic thin film solar cell of Comparative Example 1 showed a conversion efficiency value of 0.5%, whereas the organic thin film solar cell of Example 1 was 2.5%, and the organic thin film solar cell of Example 2 was 3. The conversion efficiency value improved to 0%.

DESCRIPTION OF SYMBOLS 1 ... Substrate for solar cells 2 ... Transparent substrate 3 ... Transparent electrode layer 3a ... Amorphous film 3b ... Crystal film 4 ... Buffer layer 5 ... Photoelectric conversion layer 6 ... Counter electrode layer 7 ... Heat insulation layer 8 ... Auxiliary electrode 10 ... Organic Thin film solar cell

Claims (4)

A transparent substrate having flexibility, a transparent electrode layer formed on the transparent substrate, a buffer layer containing polyethylenedioxythiophene / polystyrenesulfonic acid formed on the transparent electrode, and on the buffer layer An organic thin film solar cell having a formed photoelectric conversion layer and a counter electrode layer formed on the photoelectric conversion layer ,
The transparent electrode layer is formed on the transparent substrate and includes an amorphous film containing a conductive metal oxide, and the conductive film formed on the amorphous film and contained in the amorphous film. An organic thin film solar cell comprising a crystalline film containing the same conductive metal oxide as the metal oxide. The organic thin-film solar cell according to claim 1, wherein a heat insulating layer is formed between the transparent substrate and the transparent electrode layer. An organic thin film solar cell module comprising a plurality of the organic thin film solar cells according to claim 2 connected in series or in parallel. A transparent substrate having flexibility, a transparent electrode layer formed on the transparent substrate, a buffer layer containing polyethylenedioxythiophene / polystyrenesulfonic acid formed on the transparent electrode, and on the buffer layer A method for producing an organic thin-film solar cell, comprising: a formed photoelectric conversion layer; and a counter electrode layer formed on the photoelectric conversion layer,
  After forming an amorphous film containing a conductive metal oxide on the transparent substrate, the amorphous film and the crystal are formed by crystallizing the surface of the amorphous film by laser annealing. A transparent electrode layer forming step for obtaining a transparent electrode layer having a film; and
  A buffer layer forming step of forming a buffer layer by applying a coating solution for forming a buffer layer containing polyethylene dioxythiophene / polystyrene sulfonic acid on the transparent electrode layer;
  The manufacturing method of the organic thin-film solar cell characterized by having.

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