JP2012059388A - Photoelectric conversion element and method of manufacturing photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element using a stainless-steel grid electrode capable of realizing excellent photoelectric conversion efficiency by improving adhesion between an electrode and a photoelectric conversion layer.SOLUTION: The photoelectric conversion element at least includes: a first electrode which is the stainless-steel grid electrode subjected to acid cleaning processing and having a surface layer containing a semiconductive compound; the photoelectric conversion layer; a hole transport layer; and a second electrode.

Description

  The present invention relates to a photoelectric conversion element typified by a dye-sensitized solar cell having a function of converting light energy into electric energy, and particularly relates to a photoelectric conversion element having a grid electrode.

  Photoelectric conversion elements typified by solar cells are elements that convert light energy such as infinite solar energy into electrical energy and supply power to various devices, and are environmentally friendly, such as solar cells using silicon. Conventionally, it has been studied as an energy conversion element. For solar cells using silicon, in addition to single-crystal silicon type solar cells used for artificial satellites, solar cells using polycrystalline silicon or amorphous silicon are widely used for industrial and household purposes. ing. In addition, with the widespread use of various portable information devices such as mobile phones and mobile terminals, flexible solar cells have also emerged so that these compact devices can be set smoothly and supply stable power. Yes. All of these solar cells using silicon require large and expensive production equipment, have high raw material prices, and have problems with production costs, and also have problems with energy consumption and photoelectric conversion efficiency during production. Therefore, it was difficult to be an energy-saving power source that is environmentally friendly.

  Against this background, the development of a new type of photoelectric conversion element that can replace solar cells using silicon has been studied, and the development of a type of photoelectric conversion element called a dye-sensitized solar cell has attracted attention. (For example, see Non-Patent Document 1). The photoelectric conversion element disclosed in Non-Patent Document 1 uses titanium oxide that is spectrally sensitized with a ruthenium complex, which is one of noble metal atoms, and is an effort to purify titanium oxide that is a semiconductor material with high purity. Photoelectric conversion in the visible light range was made possible without application of light.

  By the way, the dye-sensitized photoelectric conversion element used a transparent electrode in which a compound such as indium-doped tin oxide was deposited as a conductive film on the surface of the heat-resistant glass plate from the viewpoint of securing the amount of incident light. Since the transparent conductive film is expensive, it has hindered realization of cost reduction.

  Therefore, as a photoelectric conversion element electrode that replaces the transparent electrode, an electrode having a low resistance material and a form capable of securing the amount of incident light has been studied, and a structure in which a linear metal material or the like is arranged in a lattice shape. An electrode called a grid electrode has been proposed (see, for example, Patent Documents 1 and 2). For example, Patent Document 1 is an electrode having a structure in which an oxide semiconductor sintered body is integrally coupled to a metal grid provided with innumerable openings in a metal foil. It was possible to increase the photoelectric conversion efficiency by reducing the resistance. Patent Document 2 provides a sufficient power generation effective area by providing a porous oxide semiconductor layer carrying a dye on the outer periphery of a wire forming an electrode and arranging the wire without gaps to form an electrode. In addition, excellent photoelectric conversion efficiency is realized.

  In addition, in a photoelectric conversion element having a grid electrode formed of a metal material having excellent conductivity, a technique for providing a surface layer on the grid electrode for preventing the grid electrode from being eroded by the contained electrolyte is being studied. (For example, refer to Patent Documents 3 and 4). For example, Patent Document 3 discloses a technique of covering a metal grid wiring with a shielding layer made of glass, polyimide resin, or the like, and Patent Document 4 discloses a technique of performing electrolytic copper plating on a silver thin wire. .

JP 2003-123855 A JP 2009-301840 A JP 2009-277624 A JP 2009-129552 A

B. O'Regan, M.M. Gratzel, Nature, 353, 737 (1991)

  However, since the photoelectric conversion element using the grid electrode has a structure in which it is difficult to ensure the contact area between the electrode and the photoelectric conversion layer, the adhesion between the two becomes insufficient, and the expression of predetermined photoelectric conversion efficiency or It had a tendency to be difficult to maintain stably. For example, in the manufacturing process of the photoelectric conversion element, the baking process is performed at the time of forming the photoelectric conversion layer, etc., but the electrode is slightly peeled from the photoelectric conversion layer due to the temperature change from high temperature to room temperature at the time of baking, and from the initial stage There was a possibility that a product with low photoelectric conversion efficiency was produced. Also, for example, when using a photoelectric conversion element under conditions where temperature changes between high and low temperatures are repeated, such as when used in cooking utensils, there is a concern about electrode peeling, and stable photoelectric conversion even in such an environment. There has been a demand for a photoelectric conversion element using a grid electrode that exhibits efficiency.

  The present invention provides a photoelectric conversion element using a grid electrode in which it is difficult to secure a contact area with the photoelectric conversion layer, and exhibits good adhesion between the electrode and the photoelectric conversion layer, thereby stabilizing high photoelectric conversion efficiency. It is an object of the present invention to provide a photoelectric conversion element that can be maintained.

The present inventor has found that the above problem is solved by the following configuration. That is, the invention described in claim 1
“At least a first electrode, a photoelectric conversion layer, a hole transport layer, a photoelectric conversion element having a second electrode,
The first electrode is
It is a grid electrode made of stainless steel that has been pickled and has a surface layer,
The photoelectric conversion element, wherein the surface layer contains a semiconductive compound. ].

The invention described in claim 2
“The surface layer is
The photoelectric conversion element according to claim 1, wherein the semiconductive compound contains a titanium oxide compound. ].

The invention according to claim 3
“The titanium oxide compound contained in the surface layer is
The titanium alkoxide compound alone, a mixture of a titanium alkoxide compound and an amine compound, or a mixture of a titanium alkoxide compound and an organic compound having a carboxyl group or a carbonyl group is heated to form the alkoxide compound. Or the photoelectric conversion element of 2. ].

The invention according to claim 4
[3] The photoelectric conversion device according to claim 1 or 2, wherein the titanium oxide compound contained in the surface layer is formed by thermally decomposing a titanium alkoxide complex compound. ].

The invention described in claim 5
“The stainless steel grid electrode is formed by performing the pickling treatment through a step of immersing in a solution containing at least hydrofluoric acid (HF). The photoelectric conversion element of any one. ].

The invention described in claim 6
The said stainless steel grid electrode is formed using a linear stainless steel member, The photoelectric conversion element of any one of Claims 1-5 characterized by the above-mentioned. ].

The invention described in claim 7
The said stainless steel grid electrode is formed using a plate-shaped stainless steel member, The photoelectric conversion element of any one of Claims 1-5 characterized by the above-mentioned. ].

The invention according to claim 8 provides:
“At least a method for producing a photoelectric conversion element having a first electrode, a photoelectric conversion layer, a hole transport layer, and a second electrode,
The first electrode is
It is made of stainless steel grid electrodes,
A method for producing a photoelectric conversion element, comprising at least a step of performing a pickling treatment and a step of forming a surface layer containing a semiconductive compound. ].

The invention according to claim 9 is:
“The surface layer is
The method for producing a photoelectric conversion element according to claim 8, wherein the semiconductive compound contains a titanium oxide compound. ].

The invention according to claim 10 is:
“The titanium oxide compound contained in the surface layer is
Either a titanium alkoxide compound alone, a mixture obtained by adding an amine compound to a liquid containing a titanium alkoxide compound, or a mixture obtained by adding an organic compound having a carboxyl group or a carbonyl group to a liquid containing a titanium alkoxide compound is heated. The method for producing a photoelectric conversion element according to claim 8, wherein the photoelectric conversion element is formed. ].

The invention according to claim 11
The production of the photoelectric conversion device according to claim 8 or 9, wherein the titanium oxide compound contained in the surface layer is formed by thermally decomposing a liquid containing a titanium alkoxide complex compound. Method. ].

The invention according to claim 12
The step of pickling the stainless steel grid electrode is performed by immersing the stainless steel grid electrode in a solution containing at least hydrofluoric acid (HF). The manufacturing method of the photoelectric conversion element of any one of these. ].

The invention according to claim 13
The said stainless steel grid electrode is formed using a linear stainless steel member, The manufacturing method of the photoelectric conversion element of any one of Claims 8-12 characterized by the above-mentioned. ].

The invention according to claim 14
The said stainless steel grid electrode is formed using a plate-shaped stainless steel member, The manufacturing method of the photoelectric conversion element of any one of Claims 8-12 characterized by the above-mentioned. ].

  In the present invention, the adhesion between the grid electrode and the photoelectric conversion layer is greatly improved by subjecting the stainless steel grid electrode constituting the photoelectric conversion element to a pickling treatment and providing a surface layer containing a semiconductor material. Made it happen. That is, the above-described configuration greatly improves the adhesion between the grid electrode and the photoelectric conversion layer, and the photoelectric conversion element using the grid electrode having a structure in which it is difficult to ensure the contact area between the electrode and the photoelectric conversion layer has good photoelectric conversion efficiency. Is now possible.

  For example, in the process of producing a photoelectric conversion element, a baking treatment is performed at the time of forming a photoelectric conversion layer, etc., but according to the present invention, the electrode peels from the photoelectric conversion layer when the temperature from the high temperature during baking changes to room temperature. As a result, a photoelectric conversion element that exhibits a predetermined level of photoelectric conversion efficiency from the initial stage can be produced. Moreover, when using a photoelectric conversion element in an environment where temperature changes between high and low temperatures are repeated, such as when using a photoelectric conversion element in a cooking utensil, according to the present invention, the electrode from the photoelectric conversion layer Peeling does not occur, and it can be used safely in such an environment.

It is a figure which shows typically the cross-sectional structure of the photoelectric conversion element which has a grid electrode. It is the schematic which shows the shape of a grid electrode typically. It is a figure which shows typically the relationship between the numerical value of "shape factor FF", and the shape of a "voltage-current characteristic graph."

  The present invention relates to a photoelectric conversion element having an electrode called a “grid electrode” having a region for allowing light to pass between conductive members, for example, by forming a linear conductive material in a lattice shape. And the photoelectric conversion element which concerns on this invention has a grid electrode made from stainless steel which has a surface layer which performs a pickling process and contains a semiconductive compound.

  This inventor solves the said subject by setting it as the grid electrode made from stainless steel which has the said structure about the photoelectric conversion element which has the grid electrode made difficult to ensure a contact area with a photoelectric converting layer. I found out. And the grid electrode of the said structure is not considered easily from the technique regarding the conventional grid electrode.

  That is, Patent Document 1 described above describes that a metal grid made of any of gold, silver, platinum, palladium, copper, and titanium is preferable, and there is no description suggesting that a grid electrode is made of stainless steel. It was. In addition, Patent Document 2 describes that any of titanium, nickel, tungsten, rhodium, molybdenum, and alloys thereof is used for the wire forming the electrode, but there is a description of forming the electrode with an iron-containing material. There was no suggestion of a stainless steel electrode.

  In addition, Patent Documents 3 and 4 disclose that a shielding layer and a conductive metal plating layer are provided on the surface of a metal member constituting the electrode, but these prevent corrosion of the grid electrode due to contact with the electrolytic solution. It was provided. Further, it is structurally impossible to incorporate a semiconductive compound in the formed layer. Therefore, it was considered that this does not suggest the constitution of the present invention in which a surface layer is provided on stainless steel having excellent corrosion resistance and the compound is contained in the tank. The materials of the grid electrodes disclosed in Patent Documents 3 and 4 are the same as those of Patent Documents 1 and 2, and it cannot be said that the grid electrodes are formed using stainless steel.

  Hereinafter, the present invention will be described in detail.

  First, the configuration of the photoelectric conversion element according to the present invention will be described. FIG. 1 is a diagram schematically showing a cross-sectional configuration of a photoelectric conversion element according to the present invention, that is, a photoelectric conversion element having a grid electrode. The photoelectric conversion element according to the present invention is of a type generally called “dye sensitized photoelectric conversion element”.

  The photoelectric conversion element 1 shown in FIG. 1 has a first electrode 3 (also referred to as a grid electrode in the present invention) disposed in a photoelectric conversion layer 5 that forms electrons by receiving sunlight, and faces the first electrode 3. The 2nd electrode 4 is arrange | positioned. And between the 1st electrode 3 and the 2nd electrode 4, the photoelectric conversion layer 5 containing the semiconductor material which adsorb | sucked the well-known pigment | dye from the 1st electrode 3 side, and the well-known represented by the aromatic amine compound A hole transport layer 6 containing a hole transport material is provided.

  Moreover, the 1st electrode (grid electrode) 3 which comprises the photoelectric conversion element 1 of FIG. 1 is the electrode made from stainless steel which performed the pickling process by the method mentioned later, and is formed by the method mentioned later on the surface. It has the surface layer 3A. The 1st electrode 3 which has the form of a grid electrode is arrange | positioned so that the photoelectric converting layer 5 upper surface may be covered, and transfer of an electron is performed between the 1st electrode 3 and the photoelectric converting layer 5, and it is received by the 1st electrode. The electrons are transmitted to an external circuit.

  Further, in the photoelectric conversion element 1 shown in FIG. 1, a transparent base 7 having a flat plate shape is disposed outside the first electrode 3 and the second electrode 4, respectively. The photoelectric conversion layer 5, the hole transport layer 6 and the second electrode 4 are supported, and mechanical strength is imparted to the photoelectric conversion element 1. Note that the downward white arrow shown in the upper part of FIG.

  As shown in FIG. 1, the photoelectric conversion element according to the present invention uses a grid electrode for the first electrode. The grid electrode does not need to use a noble metal like a transparent electrode, and is advantageous in terms of cost and material supply. In particular, in the present invention, the grid electrode is made of stainless steel, which is a general-purpose conductive metal. This is particularly advantageous in terms of cost and material supply stability. Hereinafter, the grid electrode will be described.

  The first electrode 3 shown in FIG. 1 has a form called a grid electrode or a mesh electrode as described above, and the electrode is used so that the photoelectric conversion layer 5 adjacent to the first electrode 3 can receive sunlight smoothly. This is an electrode provided with a region for allowing light to pass between the constituent members. That is, the grid electrode referred to in the present invention refers to an electrode that is made of a conductive material that does not transmit light like a metal material and that has a region for allowing light to pass through the electrode. . In other words, the grid electrode used for the first electrode 3 is, for example, formed by braiding a linear conductive material such as a wire into a lattice shape, or punching a plate-shaped conductive material to provide a plurality of holes. There are things.

  The grid electrodes used for these first electrodes 3 have a “light transmission region between conductive materials” called “openings”, so that sunlight 12 is smoothly transferred to the adjacent photoelectric conversion layer 5. It is designed so that it can be incident on. And the incident amount of the sunlight 12 in a grid electrode can be grasped | ascertained from the ratio of the opening part area which occupies the grid electrode total area called "aperture ratio", and the incident value of sunlight 12 is so large that the value of an aperture ratio is large. Indicates that the amount is large.

  A specific example of the grid electrode is schematically shown in FIG. FIG. 2 shows the shape of the grid electrode as viewed from the irradiation direction of sunlight 12 shown in FIG. 1, and shows a state where the grid electrode is arranged on the light receiving surface of the photoelectric conversion layer 5. The shape of the grid electrode that can be used in the present invention is not limited to that shown in FIG. First, FIG. 2A shows a lattice shape formed by knitting or weaving a linear conductive material such as a stainless steel wire, and the linear conductive material intersects vertically and horizontally. FIGS. 2B and 2C show a shape in which linear conductive materials are arranged in parallel. 2D to 2F are produced by regularly punching a plurality of holes in a conductive plate-like material such as a stainless steel thin plate.

  As is clear from the example of the shape shown in FIG. 2, the aperture ratio of the grid electrode is determined by controlling the thickness of the linear conductive material and the arrangement interval thereof, for example, when using a linear conductive material, In the case of using a conductive material, a desired value can be obtained by controlling the area of the punched hole. The aperture ratio of the grid electrode can be calculated by a known method. For example, the projected area of the entire grid electrode and the opening can be calculated by irradiating the grid electrode with light, and calculated from these projected areas. Is possible.

  The aperture ratio of the grid electrode used in the present invention is preferably 70% to 90%, and more preferably 75% to 90%. When the aperture ratio of the grid electrode is in the above range, a wide light receiving area can be secured, so that high photoelectric conversion efficiency can be obtained, and the electric charge formed in the photoelectric conversion region can reach the electrode in a short time, so that In the conversion layer, efficient charge formation can be performed without waste.

  The stainless steel used as a conductive material for the grid electrode used in the present invention will be described. As mentioned above, the 1st electrode which comprises the photoelectric conversion element which concerns on this invention provides the layer containing compounds, such as a titanium oxide, on the grid electrode surface made from stainless steel which performed the pickling process.

  The stainless steel (hereinafter also referred to as stainless steel) used as the grid electrode in the first electrode of the photoelectric conversion element according to the present invention is an alloy containing iron, chromium, nickel, etc., and the content of the iron component Is known from 60% to 80%. Various types of stainless steel are usually formed depending on the type and content of additive metals such as chromium and nickel. Such a type of stainless steel is called a steel type. Stainless steel has the property of forming an oxide film called a passive film on its surface by the action of added chromium, etc., and this oxide film has the property of being repaired immediately even if the surface is destroyed by scratches or the like. And imparts corrosion resistance to stainless steel.

  The stainless steel material that can be used in the present invention is not particularly limited, and known materials can be used. Specific examples of stainless steel include, for example, SUS304 and SUS316. SUS304 is a steel type containing 18% chromium and 8% nickel. SUS316 is based on SUS304 and increases the nickel content. It is a steel type containing 2-3%.

  The grid electrode made of stainless steel used for the first electrode of the photoelectric conversion element according to the present invention is, for example, knitted or woven linear stainless steel such as stainless steel wire by a known method as described in Examples described later. Can be manufactured. It is also possible to punch a plurality of holes in a stainless steel thin plate.

  In the present invention, a process called “pickling process” is performed in which a stainless steel grid electrode manufactured by the above-described method is immersed in a strongly acidic chemical solution or applied with a paste-like acidic agent.

  The pickling treatment of stainless steel products is usually performed through the following steps. First, there is a pretreatment process for removing foreign matters and oil adhering to the surface of the stainless steel product by washing or the like. Next, there is a pickling process in which the stainless steel product from which foreign substances and oils and fats have been removed in the pretreatment process is placed in an acidic solution tank and the product surface is uniformly contacted with the acidic solution to dissolve and roughen the surface of the stainless steel product. is there. Then, there is a drying process in which the stainless steel product that has been subjected to the pickling process is washed with water, followed by a washing process in which the remaining acid components are removed, and then the washed stainless steel product is dried to remove moisture.

  The pickling process includes a method of applying the pickling agent onto the stainless steel product by brushing or spraying in addition to the method of immersing the stainless steel product in the acidic solution bath described above. Further, in the pretreatment step, in addition to the above water washing, there may be a case of immersing in a sodium hydroxide aqueous solution tank or wiping with a waste containing an organic solvent such as alcohol in order to remove fats and oils. Further, in the washing step, neutralization may be performed using an alkaline aqueous solution in addition to the water washing.

  The stainless steel grid electrode used in the present invention transfers electrons between adjacent photoelectric conversion layers when used as a photoelectric conversion element, and can transfer electrons at the same level as a conventional transparent electrode. In order to achieve this, it is necessary to increase the surface area of the electrode constituent member. Therefore, the present inventor will increase the contact area with the photoelectric conversion layer by roughening the surface of the member constituting the grid electrode so that electrons can be efficiently exchanged with the photoelectric conversion layer. I thought. In the case of pickling treatment, the surface of the grid electrode with a complicated shape formed by braiding a stainless steel member into a mesh shape can be wetted uniformly with the treatment liquid, so a metal having a complicated and fine shape We thought that the surface of the material could be uniformly roughened without unevenness.

  And as confirmed from the result of the Example mentioned later, the photoelectric conversion element using the stainless steel grid electrode which gave the pickling process came to be able to express favorable photoelectric conversion efficiency. That is, it is considered that by roughening the surface of the grid electrode, the surface area of the electrode is increased, and by increasing the contact area between the electrode and the photoelectric conversion layer, electrons can be smoothly exchanged between the two. Moreover, it is thought that the increase in the surface area of the electrode improves the adhesion between the electrode and the photoelectric conversion layer, thereby contributing to the improvement in the durability of the photoelectric conversion element.

  The grid electrode made of stainless steel used in the present invention has a surface layer containing a semiconductive compound. This surface layer provides the grid electrode with electrical conductivity equivalent to that of the photoelectric conversion layer, and allows electrons formed in the photoelectric conversion layer to move smoothly toward the first electrode. As described above, the surface layer of the grid electrode efficiently moves the electrons formed in the photoelectric conversion layer to the first electrode, thereby contributing to improvement in photoelectric conversion efficiency.

  The improvement in photoelectric conversion efficiency by the surface layer is realized by containing a semiconductive compound in the surface layer, and the semiconductive compound contained in the surface layer is a photoelectric conversion adjacent to the first electrode. The same semiconductor material contained in the layer is preferred. As described above, in the present invention, by interposing a semiconductive compound on the surface of the first electrode, electrons formed in the photoelectric conversion layer are easily transferred to the first electrode, and thus excellent photoelectric conversion efficiency is exhibited. It seems to be done.

  Here, the “semiconductive compound” contained in the surface layer is, for example, a property of moving the formed charge when a charge amount equal to or greater than a threshold is formed due to an increase in incident light amount, etc. That is, it refers to a compound that exhibits electrical conductivity. In the present invention, as the semiconductive compound contained in the surface layer, an N-type semiconductive compound that expresses and promotes charge transfer by electrons is used. In this way, by allowing the N-type semiconductive compound to be present in the grid electrode surface layer, the movement of electrons near the interface between the photoelectric conversion layer and the first electrode is promoted, and the positive electrode formed in the photoelectric conversion layer is formed. The hole is blocked so as not to move toward the first electrode.

Examples of the semiconductive compound that is included in the surface layer of the grid electrode and promotes the movement of electrons to the grid electrode include titanium oxide, tin oxide (SnO ₂ ), aluminum oxide (Al ₂ O ₃ ), There are metal oxides such as zinc oxide (ZnO), SrTiO ₃ and SiO ₂ . Moreover, it is also possible to use metal compounds such as TiC, Si ₃ N ₄ , SiC, B ₄ N, and BN, and these metal oxides and metal compounds can be contained alone or in combination.

  Among the metal oxides and metal compounds, those containing titanium oxide in the surface layer of the grid electrode are preferable, and titanium oxide formed by thermally decomposing at least one of a titanium alkoxide compound and a titanium alkoxide complex compound is particularly preferable. . And the said metal oxide and metal compound may be contained as a semiconductor material in the photoelectric converting layer mentioned later.

  Moreover, the average film thickness of the surface layer provided in a grid electrode is not specifically limited, However, 10 nm or more and 200 nm or less are preferable from a viewpoint of making adhesiveness and electronic conductivity compatible.

  Next, the photoelectric conversion layer 5 will be described. A photoelectric conversion element 1 shown in FIG. 1 has a photoelectric conversion layer 5 that converts light energy such as sunlight into electrical energy below a stainless steel grid electrode 3 that has been subjected to the pickling treatment described above. The photoelectric conversion layer 5 has a light receiving surface 5A in which the first electrode 3 is disposed on the upper surface, and contains a semiconductive compound called a semiconductor material in which a photosensitizing dye is adsorbed. The light receiving surface 5A of the photoelectric conversion layer 5 is a portion that receives light that has passed through the opening formed between the first electrodes 3 described above, and is a first electrode that is disposed so as to cover the light receiving surface 5A. This is the place where electrons are transferred to and from 3.

  Conversion of light energy into electric energy in the photoelectric conversion layer 5 is performed in the following procedure. First, light that has passed through the opening of the first electrode 3 enters the photoelectric conversion layer 5, and the light that has entered collides with a semiconductor material described later. The light that collides with the semiconductor material is diffusely reflected in an arbitrary direction and diffused in the photoelectric conversion layer 5, and the diffused light comes into contact with the sensitizing dye to generate electrons and holes. Moves toward the first electrode 3. With such a mechanism, the photoelectric conversion layer 5 converts light energy into electric energy.

  The thickness of the photoelectric conversion layer 5 is not particularly limited, but specifically, is preferably about 0.1 μm to 50 μm, more preferably about 0.5 μm to 25 μm, and particularly preferably about 1 μm to 10 μm. . Note that the thickness of the photoelectric conversion layer 5 is substantially the same as the thickness of the contained semiconductor material, and a semiconductor material having a layered form is used from the viewpoint of realizing miniaturization of the element and reduction in manufacturing cost. It is preferable to use it.

As described above, the photoelectric conversion layer 5 contains a semiconductor material in which a photosensitizing dye is adsorbed, and examples of the semiconductor material include titanium oxide, zinc oxide (ZnO), and tin oxide (SnO ₂ ). N-type semiconductor material is used. Of these n-type semiconductor materials, titanium oxide is preferably used. Examples of titanium oxide include titanium dioxide (TiO ₂ ), titanium monoxide (TiO), and titanium trioxide (Ti ₂ O ₃ ). Titanium is particularly preferably used. In other words, in addition to having good electron transport properties, titanium dioxide has high sensitivity to light, and high photoelectric conversion efficiency can be expected, such as titanium dioxide itself receiving light to generate electrons directly. To be particularly preferred. Moreover, since titanium dioxide has a stable crystal structure, even if it continues to be irradiated with light in a harsh environment, deterioration with time does not easily occur, and a predetermined performance can be stably expressed over a long period of time.

  By the way, there are anatase type and rutile type in the crystal structure of titanium dioxide, and semiconductor materials for photoelectric conversion elements are mainly those of anatase type crystal structure, those mainly of rutile type crystal structure, both Any of those based on the above mixture can be used. Among these, titanium dioxide having an anatase type crystal structure can perform efficient electron transport. When anatase type and rutile type are used in combination, the mixing ratio of the anatase type and rutile type is not particularly limited, and anatase type: rutile type = 95: 5 to 5:95. It is possible, and it is preferable to set it as 80: 20-20: 80.

  In addition, the semiconductor material preferably has a plurality of fine pores (pores) on the surface from the viewpoint of improving the photoelectric conversion efficiency by promoting the diffuse reflection and diffusion of the colliding light. Therefore, high photoelectric conversion efficiency can be expected. The pores of the semiconductor material can be defined by, for example, the ratio of the area of the pores per unit area of the surface of the semiconductor particles called porosity. In other words, the semiconductor material having an appropriate porosity promotes diffuse reflection and diffusion of light, and in addition, the sensitizing dye adsorbed on the outer surface of the semiconductor material and the inner surface of the pore as the surface area increases due to the pore. The adsorption area is also increased, and the photoelectric conversion efficiency can be further improved. The porosity of the semiconductor material is not particularly limited. For example, in the case of titanium dioxide, 5% to 90% is preferable, more preferably 15% to 80%, and particularly preferably 25% to 70%. is there.

  The average particle size of the semiconductor material is not particularly limited, but in the present invention, the average particle size is preferably 1 nm to 1 μm, more preferably 5 nm to 50 nm. When the average particle size of the semiconductor material is within the above range, it becomes easier to improve the uniformity of the semiconductor material when the sol solution is formed. As the dye is adsorbed to the same level, it contributes to the improvement of power generation efficiency.

  Furthermore, the semiconductor material has a structure in which a photosensitizing dye is adsorbed, but the adsorption formed between the semiconductor material and the photosensitizing dye is, for example, physical such as intermolecular attractive force or electrostatic attractive force. It is realized by a chemical bond such as a covalent bond or a coordinate bond. The photosensitizing dye generates electrons and holes by receiving light, and actually converts light energy into electric energy in the photoelectric conversion layer 5. That is, in the photoelectric conversion layer 5, the region where the photosensitizing dye is present functions as a light receiving region for generating electrons and holes. As described above, the photosensitizing dye is used on the outer surface of the semiconductor material. Adsorbed along the inner surface of the hole. Then, electrons generated by the photosensitizing dye move to the semiconductor material bonded to the photosensitizing dye, and move from the semiconductor material toward the first electrode 3.

The amount of adsorption of the photosensitizing dye to the semiconductor material is not particularly limited. For example, in the case of titanium dioxide, 0.01 to 100 mmol per 1 m ^{2 of the} photoelectric conversion layer is preferable, more preferably 0.1. -50 mmol, particularly preferably 0.5-20 mmol. In addition, the specific compound example of the photosensitizing dye which can adsorb | suck to a semiconductor material is mentioned later.

  Next, the hole transport layer 6 will be described. The hole transport layer 6 is formed in a layer shape adjacent to the photoelectric conversion layer 5. The hole transport layer 6 is injected with holes generated in the photoelectric conversion layer 5 by a hole transport material such as an aromatic amine compound, and transports it toward an external circuit via a second electrode described later. Is. In some cases, the hole transport layer 6 itself functions as the second electrode. Although the average thickness of the positive hole transport layer 6 is not specifically limited, For example, 0.1-100 micrometers is preferable, More preferably, it is 0.5-50 micrometers, Most preferably, it is 1-20 micrometers. In addition, the specific compound example of the hole transport material which can be contained in the hole transport layer will be described later.

  Next, the second electrode 4 will be described. The second electrode 4 is formed in a layer shape (flat plate shape) adjacent to the hole transport layer 6, and the average thickness is appropriately set depending on the material, use, etc., and is not particularly limited. The second electrode 4 can be formed using a known conductive material or semiconductive material. Examples of the conductive material include various ion conductive materials, metals such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, and tantalum, alloys containing these, and various carbons such as graphite. Materials and the like. Examples of the semiconductive material include p-type semiconductor materials such as triphenyldiamine (monomers, polymers, etc.), polyaniline, polypyrrole, polythiophene, phthalocyanine compounds (eg, copper phthalocyanine, etc.), and derivatives thereof. . The second electrode 4 can be formed by combining one or more of these conductive materials and semiconductive materials.

  As shown in FIG. 1, the photoelectric conversion element according to the present invention is a transparent plate having a flat shape that supports the first electrode 3, the photoelectric conversion layer 5, the hole transport layer 6, and the second electrode 4 described above. A simple substrate 8 can be used. Specific examples of the substrate include transparent inorganic materials such as quartz and glass and known transparent resin materials shown below.

  Specific examples of the transparent resin material include, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyimide (PI), polycarbonate (PC), polystyrene (PS), polypropylene (PP), Examples include polybutylene terephthalate (PBT), trimethylene terephthalate, polybutylene naphthalate, polyamideimide, cycloolefin polymer, and styrene butadiene copolymer. Among the transparent resin materials, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyimide (PI), and the like having a flexibility are commercially available to produce a flexible photoelectric conversion element. Is preferable.

  Further, the thickness of the substrate can be appropriately set depending on the material and application. For example, when the substrate is made of a hard material such as a transparent inorganic material such as glass, the average thickness is preferably 0.1 mm to 1.5 mm. 0.8 mm to 1.2 mm is more preferable. Moreover, when using a transparent resin material, it may be the same average thickness as the transparent inorganic material, but when using a transparent resin material having flexibility, 0.5 to 150 μm is preferable, and 10 to 75 μm is more preferable. preferable.

  Next, the photosensitizing dye to be adsorbed on the semiconductor material contained in the photoelectric conversion layer 5 will be described. As described above, the photoelectric conversion layer 5 constituting the photoelectric conversion element 1 shown in FIG. 1 contains a semiconductor material to which a photosensitizing dye is adsorbed. The photosensitizing dye that can be adsorbed to the semiconductor material contained in the photoelectric conversion layer 5 is not particularly limited, and a known pigment or dye is used alone or in combination. Among these photosensitizing dyes, pigments have merit in terms of durability with little deterioration and deterioration over time, and dyes have merit in that good adsorptivity is exhibited in semiconductor materials.

  Examples of the pigment that can be used as the photosensitizing dye include organic pigments, carbon pigments, and known inorganic pigments as described below. Among these, examples of the organic pigment include phthalocyanine pigments, azo pigments, anthraquinone pigments, quinacridone pigments, and perylene pigments as shown below.

  Here, specific examples of the phthalocyanine pigment include phthalocyanine green and phthalocyanine blue. Specific examples of the azo pigment include, for example, fast yellow, disazo yellow, condensed azo yellow, benzimidazolone yellow, dinitroaniline orange, penzimidazolone orange, toluidine red, permanent carmine, permanent red, naphthol red, Examples include condensed azo red, benzimidazolone carmine, and benzimidazolone brown.

  Specific examples of anthraquinone pigments include anthrapyrimidine yellow and anthraquinonyl red. Specific examples of the quinacridone pigment include quinacridone magenta, quinacridone maroon, quinacridone scarlet, quinacridone red, and the like, and specific examples of the perylene pigment include perylene red and perylene maroon.

  In addition to the above organic pigments, examples of organic pigments that can be used as photosensitizing dyes include azomethine pigments such as copper azomethine yellow, quinophthalone pigments such as quinophthalone yellow, and isoindoline pigments such as isoindoline yellow. And pigments, nitroso pigments such as nickel dioxime yellow, perinone pigments such as perinone orange, pyrrolopyrrole pigments such as diketopyrrolopyrrole red, and dioxazine pigments such as dioxazine violet. Carbon-based pigments include carbon black, lamp black, furnace black, ivory black, graphite, fullerene and the like.

As the dyes that can be used as a photosensitizing dye, for _example, (manufactured by Solaronics, _{Inc.) RuL 2 (SCN) 2,} RuL 2 Cl 2, RuL 2 (CN) 2, Rutenium535-bisTBA, _[Ru 2 (NCS) _{2] 2} H ₂ O and the like of the metal complex dyes. Note that L in the composition formula of the metal complex dye represents 2,2′-bipyridine, or a derivative thereof. In addition to the aforementioned metal complex dyes, cyan dyes, xanthene dyes, azo dyes, hibiscus dyes, blackberry dyes, raspberry dyes, pomegranate juice dyes, chlorophyll dyes, and the like, one of these Or it is possible to use 2 or more types in combination.

The total amount of these photosensitizing dyes supported on a semiconductor material such as titanium dioxide is not particularly limited, but is preferably 0.01 to 100 mmol, and preferably 0.1 to 50 mmol per 1 m ^{2 of the} photoelectric conversion layer. More preferred is 0.5 to 20 mmol.

  Next, specific examples of the hole transport material contained in the above-described hole transport layer 6 will be described. The hole transport layer constituting the photoelectric conversion element according to the present invention is contained as a hole transport material typified by an aromatic amine compound. As described above, in the hole transport layer 6, holes generated in the photoelectric conversion layer 5 are captured by the hole transport material, and the captured holes are directed to the external circuit through the second electrode. It is to be transported.

  The hole transport material that can be added to the hole transport layer constituting the photoelectric conversion element according to the present invention is particularly limited as long as it is a compound that can transport holes generated in the photoelectric conversion layer. It is possible to use a well-known thing instead of a thing. Among the compounds having the property of transporting holes, aromatic amine compounds are preferably used for the following reasons. That is, in the photoelectric conversion element in which the photoelectric conversion efficiency in the photoelectric conversion layer is improved by the semiconductor material carrying the photosensitizing dye compound, an environment in which more holes are generated is generated. It is possible to reliably transport all the holes formed in a rough environment. As described above, it is preferable to use an aromatic amine compound as the hole transporting material because the generated holes can be transported to the hole transporting layer and good photoelectric conversion efficiency can be stably maintained.

  Among the aromatic amine compounds used as the hole transport material, those having a molecular weight of 500 or more and 2000 or less are more preferably used. When an aromatic amine compound having a molecular weight in the above range is used as a hole transport material, a hole transport layer formed of a solid film can be obtained, so that photoelectric conversion with excellent durability without causing leakage or volatilization of an electrolytic solution is obtained. It is considered that an element is formed. In addition, since the aromatic amine compound having a molecular weight in the above range has a property of easily penetrating into the photoelectric conversion layer, it is considered that the aromatic amine compound contributes to the improvement of the charge transport performance by the penetration.

Specific examples of the aromatic amine compound that can be used for the hole transport material include the following. In addition, the name of a document in which the compound is disclosed is described in parentheses after the specific compound name. That is,
N, N′-diphenyl-N, N′-bis (4-methoxyphenyl)-(1,1′-biphenyl) -4,4′-diamine (J. Hagen et al., Synthetic Metal 89 (1997) 215 -220)
2,2 ′, 7,7′-tetrakis (N, N-di-p-methoxyphenylamine) 9,9′-spirobifluorene (Nature, Vol. 395, 8 Oct. 1998, p583-585 and WO97 / 10617)
Aromatic diamine compounds having a structure in which tertiary aromatic amine units of 1,1-bis [4- (di-p-tolylamino) phenyl] cyclohexane are linked (Japanese Patent Laid-Open No. 59-194393)
It contains two or more nitrogen atoms forming a tertiary amine typified by 4,4-bis [(N-1-naphthyl) -N-phenylamino] biphenyl, and two or more condensed aromatics in the nitrogen atom Aromatic amine compounds having a structure in which rings are bonded (Japanese Patent Laid-Open No. 5-234681)
Aromatic triamine compound having a starburst structure which is a derivative of triphenylbenzene (US Pat. No. 4,923,774, JP-A-4-308688)
Aromatic diamine compounds such as N, N′-diphenyl-N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (US Pat. No. 4,764,625) issue)
α, α, α ′, α′-tetramethyl-α, α′-bis (4-di-p-tolylaminophenyl) -p-xylene (Japanese Patent Laid-Open No. 3-269084)
p-Phenylenediamine derivative Triphenylamine derivative which is sterically asymmetric as a whole molecule (Japanese Patent Laid-Open No. 4-129271)
Aromatic amine compounds having a structure in which a plurality of aromatic diamino groups are substituted for pyrenyl groups (Japanese Patent Laid-Open No. 4-175395)
An aromatic diamine compound having a structure in which a tertiary aromatic amine unit is linked by an ethylene group (JP-A-4-264189)
Aromatic diamine compounds having a styryl structure (Japanese Patent Laid-Open No. 4-290851)
Benzylphenyl compound (Japanese Patent Laid-Open No. 4-364153)
Aromatic amine compounds having a structure in which a tertiary amine is linked by a fluorene group (Japanese Patent Laid-Open No. 5-25473)
Triamine compound (JP-A-5-239455)
Pisdipyridylaminobiphenyl (JP-A-5-320634)
N, N, N-triphenylamine derivative (JP-A-6-1972)
Aromatic diamine having phenoxazine structure (Japanese Patent Laid-Open No. 7-138562)
Diaminophenylphenanthridine derivatives (Japanese Patent Laid-Open No. 7-252474) and the like.

  Moreover, the thiophene compound shown below can also be used as a hole transport material. That is, α-octylthiophene and α, ω-dihexyl-α-octylthiophene (Adv. Mater. 1997, 9No. 7, p557), hexadodecyl dodecithiophene (Angew. Chem. Int. Ed. Engl. 1995, 34). , No. 3, p303-307), 2,8-dihexylanthra [2,3-b: 6,7-b ′] dithiophene (JACS, Vol120, No. 4, 1998, p664-672) There are compounds.

  Moreover, the conductive polymer shown below can also be used as a hole transport material. That is, polypyrrole (K. Murakoshi et al., Chem. 1997, p471), Handbook of Organic Conducive Molecules and Polymers Vol. 1,2,3,4 (NALWA, published by WILEY), polyacetylene and derivatives thereof, poly (p-phenylene) and derivatives thereof, poly (p-phenylene vinylene) and derivatives thereof, polythienylene vinylene and derivatives thereof , Polythiophene and derivatives thereof, polyaniline and derivatives thereof, polytoluidine and derivatives thereof, and the like.

Furthermore, Nature, Vol. 395, 8 Oct. As described in 1998, p583-585, a compound containing a cation radical such as tris (4-bromophenyl) aluminum hexachloroantimonate is added to control the dopant level, and the potential of the oxide semiconductor surface It is also possible to add a salt such as Li [(CF ₃ SO ₂ ) ₂ N] for control.

Next, the manufacturing method of the photoelectric conversion element concerning this invention is demonstrated. A typical method for producing a photoelectric conversion element according to the present invention is, for example, a production method having at least the following steps [1] to [6]. That is,
[1] Production of first electrode (grid electrode) [2] Pickling treatment of grid electrode [3] Formation of surface layer on grid electrode [4] Formation of photoelectric conversion layer [5] Formation of hole transport layer [ 6] Formation of Second Electrode Hereinafter, the steps [1] to [6] will be sequentially described. However, the method for producing a photoelectric conversion element according to the present invention is not limited to the one having the following steps. .

[1] Production of the first electrode (grid electrode) The first electrode (grid electrode) is produced by knitting or weaving a stainless steel wire to form a mesh-like region (opening). Part) and a method of punching a plate member made of stainless steel to form a hole and forming it in the opening.

[2] Pickling treatment of grid electrode Next, the pickling treatment is performed on the stainless steel material (grid electrode) provided with the opening through which sunlight passes by the above method. For the pickling treatment to the grid electrode, it is possible to apply a known pickling treatment that is usually performed on a stainless steel material. Specifically, the liquid used for the pickling treatment is a mixed solution of hydrofluoric acid, sodium chlorate, and hydrochloric acid described in Examples described later, a solution mixed with hydrofluoric acid, sodium chlorate, and sulfuric acid, or There is a mixed solution of nitric acid (HNO ₃ ) and hydrofluoric acid (hydrogen fluoride HF) called nitric hydrofluoric acid. It is also possible to use a commercially available pickling treatment solution. For example, “Lasnon Well P-500 (manufactured by Keisho Co., Ltd.)”, “Coolmin ES (manufactured by Coolmin Chemical Industry Co., Ltd.)”, etc. is there.

  The pickling treatment can be performed with the temperature of the treatment liquid in the range of room temperature to 60 ° C, and is preferably performed at 35 ° C to 45 ° C from the viewpoint of efficiently performing the treatment. Further, the treatment time is preferably 1 minute to 20 minutes, and preferably about 10 minutes from the viewpoint of the material such as a stainless steel wire or a thin plate material.

  Furthermore, in addition to the method of immersing the grid electrode in the bath containing the treatment liquid (immersion method), the treatment method includes a method of applying the treatment liquid to the grid electrode by brush, or a mist shape using a spray nozzle or an air pump. There is a method (spraying method) of spraying the treated liquid. In the dipping method, aeration or pump circulation can be used in combination with the tank in which the grid electrode is placed when pickling.

[3] Formation of surface layer on grid electrode Next, a surface layer is formed on the grid electrode subjected to the pickling treatment. The formation of the surface layer is, for example, a known method such as a sol-gel method, vapor deposition (vacuum vapor deposition) method, sputtering method (high frequency sputtering, DC sputtering), spray pyrolysis method, jet mold (plasma spraying) method, CVD method or the like. Can be done. Among the above-mentioned methods, the “sol-gel method” is preferable because the surface layer is formed by the following procedure, and the surface layer can be easily formed without using a large apparatus. In the sol-gel method, first, a sol solution of a semiconductive compound contained in the surface layer is prepared, and the prepared sol solution is dipped (dip coating) or dripped, doctor blade, spin coating, brush coating, spray coating, It is applied to the grid electrode by a known application method such as a roll coater. Then, the surface layer is formed by heating and baking the applied grid electrode.

  As described above, the surface layer contains a semiconductive compound such as titanium oxide that efficiently moves electrons formed in the photoelectric conversion layer to the grid electrode. Hereinafter, a method for forming a surface layer containing titanium oxide, which is one of typical semiconductive compounds, by a sol-gel method will be described.

  By the way, the sol liquid used when forming the surface layer containing titanium oxide contains, for example, a titanium oxide-forming compound such as a titanium alkoxide compound or a titanium alkoxide complex compound. The sol-gel method includes a method using a sol solution that allows a titanium oxide forming reaction by hydrolysis and polycondensation, and a method using a sol solution that does not allow a titanium oxide forming reaction.

  One of the methods using a sol solution that does not allow the titanium oxide formation reaction is a method called “MOD method (Metal Organic Deposition method or Metal Organic Decomposition method)”. The “MOD method” is a method in which a metal organic compound is dissolved in an organic solvent, this solution is applied as a sol solution to a grid electrode, and the organic component is burned and removed by heating to remove a metal oxide such as titanium oxide. Is formed into a film. That is, the reactivity of the titanium oxide-forming compound is suppressed in the sol solution, and the titanium oxide-forming compound becomes titanium oxide by heating and baking performed after application to the grid electrode surface, thereby forming a dense surface layer. Preferred method above.

  The sol liquid used in the surface layer formation by the “MOD method” contains one or more organic titanium compounds typified by a titanium alkoxide compound as a titanium oxide forming compound. Specific examples of the titanium alkoxide compound include, for example, titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide, and the like. In addition to the titanium alkoxide compounds, organic titanium compounds include compounds such as titanium oxyacetylacetonate (TOA). Furthermore, in preparation of the sol solution, it is possible to use an inorganic titanium compound such as titanium tetrachloride (TTC) in addition to the organic titanium compound.

  Hereinafter, as a specific example of the surface layer forming method by the “MOD method”, a method of forming a sol solution using a titanium alkoxide compound as a titanium oxide forming compound and forming the surface layer using the sol solution will be described. Surface layer formation on a pickled stainless steel grid electrode by the “MOD method” includes at least (1) preparation of a sol solution, (2) application of the sol solution to the grid electrode, and (3) firing treatment of the coating layer. These are performed through the three steps. Here, each process of (1)-(3) is demonstrated.

(1) Preparation of sol solution This step is a step of preparing a sol solution containing a titanium oxide forming compound to be applied to a pickled stainless steel grid electrode. When using a titanium alkoxide compound as the titanium oxide forming compound, first, the titanium alkoxide compound is dissolved in an organic solvent to prepare a solution. The titanium alkoxide compound single solution thus formed can be applied to the surface of the grid electrode and subjected to heat treatment to form titanium oxide.

  The organic solvent for dissolving the titanium alkoxide compound may be any one that can dissolve the titanium alkoxide compound, and examples thereof include anhydrous ethanol, 2-butanol, 2-propanol, 2-n-butoxyethanol, and 2-ethoxyethanol. . The titanium alkoxide compound is dissolved using these organic solvents alone or as a mixed solvent using a plurality of types. In addition, the titanium alkoxide compound used for the formation of the sol liquid may be one kind or a combination of two or more kinds.

  The concentration of the titanium alkoxide compound in the titanium alkoxide compound solution is not particularly limited. For example, by setting the concentration to 0.1 mol / liter to 10 mol / liter, a viscosity that allows smooth application to the electrode is obtained. Therefore, it is preferable. That is, when the grid electrode is applied by a dip coating method in the coating process described later, the amount of the titanium alkoxide compound added is adjusted so that the optimum viscosity is 0.5 cP to 20 cP (normal temperature) by the coating method. Prepare. Moreover, when apply | coating by a dip coating method, the addition amount of a titanium alkoxide compound is prepared so that it may become 0.1 cP-2 cP (normal temperature) made into the optimal viscosity by the said coating method.

  There is also a method of preparing a sol solution by adding a compound that stabilizes a titanium alkoxide compound such as acetylacetone or diethanolamine to the above-described solution in which a titanium alkoxide compound is dissolved in an organic solvent. A method for stabilizing the titanium alkoxide compound by adding a compound such as acetylacetone to the titanium alkoxide compound solution will be described. Examples of the compound that stabilizes the titanium alkoxide compound (hereinafter also referred to as a stabilizing compound) include acetic acid, acetylacetone, triethanolamine, and diethanolamine. These compounds replace the alkoxyl group coordinated with the titanium atom in the titanium alkoxide compound to form a complex by coordinating with the titanium atom. This complex formation suppresses hydrolysis of the titanium alkoxide compound. It is thought to stabilize.

  For example, when diethanolamine is added to the solution, the alkoxyl group in the titanium alkoxide compound is replaced with diethanolamine, and two diethanolamine molecules are coordinated to the titanium atom. The complex formed by coordination of diethanolamine becomes a more stable compound than the titanium alkoxide compound in forming titanium oxide. The compounding ratio of the stabilizing compound and the titanium alkoxide compound in the solution is not particularly limited, but for example, the molar ratio is preferably in the range of 1: 2 to 8: 1.

  By the above procedure, a sol solution of a titanium alkoxide compound can be prepared. When preparing a sol solution using a stable organic titanium compound such as titanium oxyacetylacetonate or an inorganic titanium compound such as titanium tetrachloride, the sol solution is prepared by dissolving them in the organic solvent as they are. be able to. For example, in the case of using an inorganic titanium compound, an organic solvent in which the inorganic titanium compound is dissolved coordinates to a titanium atom to achieve stabilization.

(2) Application | coating to grid electrode of sol liquid This process is a process of apply | coating to the grid electrode made from stainless steel which pickled the sol liquid produced in the said procedure. The application of the sol solution to the stainless steel grid electrode can be performed by using the above-described application method. For example, in the case of applying by a spin coat method, the sol solution prepared to have the above-described viscosity is used. The number of rotations can be set from 500 rpm to 4000 rpm. In addition, it is preferable to remove deposits such as organic substances from the grid electrode surface by a known method before applying the sol solution. Examples of the method for removing deposits such as organic substances include O ₂ plasma treatment, EB (electron beam) treatment, and cleaning treatment with ethanol or acetone.

(3) Baking treatment This step is a step of heating the grid electrode to remove the organic solvent from the coating film formed on the surface of the grid electrode in the coating step and generating titanium oxide to form a surface layer. . Specifically, the coating is first dried by heating at a temperature of 50 ° C. to 250 ° C. for 1 minute to 60 minutes, followed by heating at a temperature of 300 ° C. to 700 ° C. for 1 minute to 70 minutes. To remove the residual organic solvent and form a surface layer containing titanium dioxide in the coating film. This heat treatment is preferably performed in the air, in an atmosphere of nitrogen gas or various inert gases, or in a non-oxidizing atmosphere such as vacuum or reduced pressure. The first “heat treatment performed at a temperature of 50 ° C. to 250 ° C. for 1 minute to 60 minutes” is preferably performed at a temperature of 100 ° C. to 200 ° C. for 5 minutes to 30 minutes. The subsequent “heat treatment performed at a temperature of 300 ° C. to 700 ° C. for 1 minute to 70 minutes” is preferably performed at a temperature of 400 ° C. to 550 ° C. for 5 minutes to 45 minutes.

  Through the above operation, a surface layer containing a semiconductor compound is formed on the pickled stainless steel grid electrode.

[4] Formation of photoelectric conversion layer Next, a photoelectric conversion layer is formed adjacent to the first electrode on which the surface layer is formed. As shown below, the photoelectric conversion layer is formed by at least a step of forming a semiconductor material constituting the photoelectric conversion layer, a step of forming the photoelectric conversion layer by applying the formed semiconductor material to the first electrode surface, and formation It is performed through a process of adsorbing a sensitizing dye to the photoelectric conversion layer.

  First, “the step of forming a semiconductor material constituting the photoelectric conversion layer” will be described. The semiconductor material can be formed by a known method such as a sol-gel method, a vapor deposition method, or a sputtering method, and among these, the sol-gel method is preferable. The reason is that, as shown below, when the semiconductor material is made into a sol liquid, it is easy to form a semiconductor material having a porous surface.

  Here, as an example of a specific method for forming a semiconductor material, a method for forming a semiconductor material by producing a sol solution containing a titanium oxide compound and a titanium dioxide powder will be described.

(1) Preparation of Titanium Oxide Powder Rutile type titanium dioxide powder and anatase type titanium dioxide powder are mixed so as to have a predetermined blending ratio. The average particle size of the rutile type titanium dioxide powder and the average particle size of the anatase type titanium dioxide powder may be the same or different, and it is particularly preferable that the two are different.

(2) Preparation of Sol Solution The preparation of the sol solution is performed through the following procedures (a) to (d), but is not limited thereto. That is,
(A) Preparation of Titanium Compound Solution First, a known organic titanium compound or a combination of two or more known inorganic titanium compounds is dissolved in an organic solvent to prepare a solution of the titanium compound. At this time, although the said titanium compound density | concentration (content) in an organic solvent is not specifically limited, For example, it is preferable to set it as 0.1-3.0 mol / liter.

  Examples of the organic titanium compound used here include titanium alkoxide compounds such as titanium tetraisopropoxide (TPT) and titanium oxyacetylacetonate (TOA) mentioned in the description of the surface layer formation on the grid electrode. . Examples of the inorganic titanium compound include titanium tetrachloride (TTC) described above. Moreover, as the organic solvent for dissolving the titanium compound, it is possible to use an organic solvent such as anhydrous ethanol mentioned in the description of the surface layer formation on the grid electrode or a mixed solvent of the above organic solvent.

Moreover, it is also possible to add the compound which stabilizes the said titanium compound in the said solution similarly to when forming the surface layer on a grid electrode. As a compound that stabilizes the titanium compound in the solution, for example, when titanium alkoxide is contained, it is preferable to add acetic acid, acetylacetone, nitric acid, and the like, thereby chemically stabilizing the titanium alkoxide. The blending ratio of these stabilizing compound and titanium compound is preferably 1: 2 to 8: 1 in terms of molar ratio as in the case of forming the surface layer on the grid electrode.
(B) Addition of water to titanium solution In the above titanium compound solution, water such as distilled water, ultrapure water, or ion exchange water is added and mixed, and the mixing ratio of water and titanium compound is a molar ratio. The ratio is preferably 1: 4 to 4: 1.
(C) Addition of titanium dioxide powder In the titanium compound solution to which the water has been added, the titanium dioxide powder prepared in the step (1) is added and mixed to prepare a suspension (dispersion).
(D) Preparation of sol liquid A suspension (dispersion liquid) prepared by adding and mixing the above titanium dioxide powder is diluted with the organic solvent used in (a) to prepare a sol liquid. When preparing the sol solution, the dilution ratio with the organic solvent is preferably about 1.2 to 3.5 times, for example, and the content of the titanium dioxide powder is preferably 0.1 to 10% by mass, for example. 5-5 mass% is more preferable. By setting the dilution ratio with the organic solvent and the content of the titanium dioxide powder within the above ranges, a porous titanium dioxide semiconductor material having an appropriate porosity can be formed.

  Next, a process of forming the photoelectric conversion layer by applying the formed semiconductor material to the first electrode in a planar shape will be described. This step is a step of directly applying the sol solution of the porous semiconductor material produced by the above procedure to the first electrode by a known application method. Specific examples of the method for applying the sol solution to the first electrode include a dipping method, a dropping method, a doctor blade method, a spin coating method, a brush coating method, a spray coating method, and a roll coater method.

  After the sol solution is applied to the first electrode by the known application method described above, the coating film is formed by heat treatment at, for example, 80 ° C. to 180 ° C., preferably 100 ° C. to 160 ° C. And after heat-processing, a sol liquid is again apply | coated to the formed coating film, this is heat-processed, and a coating film is grown. By performing such coating treatment and heat treatment, for example, 1 to 10 times, preferably 5 to 7 times, the photoelectric conversion layer can be formed adjacent to the first electrode.

  Next, the “step of adsorbing the sensitizing dye to the formed photoelectric conversion layer” will be described. In this step, the semiconductor material constituting the photoelectric conversion layer formed by the above procedure is brought into contact with the liquid containing the above-described photosensitizing dye, and the photosensitizing dye is adsorbed and bonded to the outer surface or hole of the semiconductor material. It is a process. Specifically, when a laminate composed of the first electrode and the photoelectric conversion layer is immersed in a photosensitizing dye-containing liquid, photosensitization is performed along the outer surface and inner surface of the hole of the semiconductor material constituting the photoelectric conversion layer. The dye is adsorbed and the photosensitizing dye is bound to the semiconductor material. Here, the photosensitizing dye-containing liquid includes, for example, a dispersion in which a photosensitizing dye is dispersed in a solvent in addition to a solution in which the photosensitizing dye is dissolved in a solvent. And a liquid having a property capable of adsorbing and bonding the photosensitizing dye to the semiconductor material.

  Although the solvent which can be used for a photosensitizing dye containing liquid is not specifically limited, For example, organic solvents, such as alcohol and ether other than water, such as distilled water and ion-exchange water, are mentioned. Specific examples of alcohol include methanol, ethanol, isopropyl alcohol, and the like, and specific examples of ether include methyl ethyl ether, diethyl ether, and the like. Acetonitrile, ethyl acetate, N-methylpyrrolidone, etc. can also be used.

  As described above, after immersing the laminate in the photosensitizing dye-containing solution, the laminate is taken out from the solution and naturally dried or sprayed with a gas such as air or nitrogen gas to remove the solvent. Furthermore, if necessary, for example, it is possible to perform a drying treatment at a temperature of 60 ° C. to 100 ° C. for 30 minutes to 2 hours to remove the solvent. By these solvent removal treatments, the photosensitizing dye is more strongly adsorbed and bonded to the semiconductor material constituting the photoelectric conversion layer.

[5] Formation of hole transport layer The hole transport layer is formed, for example, by applying a hole transport material typified by the above-described aromatic amine compound to the surface of the photoelectric conversion layer by a known method. Examples of the coating method that can be used for forming the hole transport layer include the known coating methods described in the above-described formation of the photoelectric conversion layer. Specific examples include a dipping method, a dropping method, a doctor blade method, a spin coating method, a brush coating method, a spray coating method, and a roll coater method. The hole transporting layer can be penetrated into the photoelectric conversion layer by these known coating methods.

  Further, the hole transport layer formed by the above method can be subjected to a heat treatment, for example, under reduced pressure or in an inert atmosphere. By performing the heat treatment, the residual solvent in the hole transport layer is efficiently removed, and the production of the hole transport layer is speeded up, so that the production efficiency of the photoelectric conversion element is improved. The heating temperature for the heat treatment is preferably, for example, 50 ° C to 150 ° C. Then, by repeatedly performing the above-described application and heat treatment, a stacked hole transport layer can be formed.

  Solvents that can be used for forming the hole transport layer include polar solvents and organic solvents such as aprotic solvents described below. Examples of the polar solvent include tetrahydrofuran (THF), butylene oxide, cyclohexanone, acetone, various alcohols, and the like. Examples of the aprotic solvent include dimethylformamide (DMF), acetonitrile, dimethoxyethane, dimethyl sulfoxide, hexamethylphosphoric triamide, and the like. One or two or more of these organic solvents can be used in combination.

[6] Formation of second electrode The second electrode is formed adjacent to the hole transport layer surface. The second electrode can be formed adjacent to the hole transport layer surface by a known method such as a vapor deposition method, a sputtering method, or a printing method, for example, using a material composed of gold or the like.

  Through the above steps, the photoelectric conversion element according to the present invention can be manufactured.

  Examples of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

1. 1. Production of “photoelectric conversion elements 1 to 12” 1-1. Production of “photoelectric conversion element 1” (1) Formation of first electrode (grid electrode) Linear SUS316 steel (commercially available) having a diameter of 30 μm is knitted into a shape shown in FIG. A grid electrode made of stainless steel with a rate of 85% was produced.

(2) Pickling treatment of grid electrode Next, the above-mentioned stainless steel grid electrode is put into a tank containing an acidic mixed solution of 2% hydrofluoric acid (HF), 5% sodium chlorate, and 5% hydrochloric acid, and the temperature After the immersion treatment at 40 ° C. for 10 minutes, the grid electrode was washed with water.

(3) Formation of surface layer First, the coating liquid apply | coated to the grid electrode which performed the said pickling process was produced. Titanium tetraisopropoxide, which is a titanium oxide forming compound, was added to 2- (n-butoxy) ethanol and dissolved so as to have a concentration of 0.5 mol / liter. Subsequently, diethanolamine was added to prepare a coating solution so that the mixing ratio with titanium tetraisopropoxide was 2: 1 in terms of molar ratio.

  Next, a surface layer is formed by dip-coating the coating solution onto the first electrode, and the first electrode on which the surface layer is formed is placed on a hot plate and heat-treated at 120 ° C. for 3 minutes. The layer was dried and further heat treated in an oven at 450 ° C. for 20 minutes. The dip coating is performed by setting the coating speed at 1 mm / sec. In this way, a surface layer containing titanium oxide was formed on the surface of the first electrode.

(4) Formation of photoelectric conversion layer Next, the photoelectric conversion layer containing a titanium oxide was formed adjacent to the 1st electrode which has the said surface layer with the following procedure.

(Preparation of titanium oxide powder)
A titanium dioxide powder made of a mixture of a rutile type titanium dioxide powder and an anatase type titanium dioxide powder was prepared. The average particle diameter of the titanium dioxide powder was 40 nm, and the mixing ratio of the rutile type titanium dioxide powder and the anatase type titanium dioxide powder was 60:40 by mass ratio.

(Preparation of sol solution)
First, after dissolving titanium tetraisopropoxide in 2-propanol to a concentration of 1 mol / liter, acetic acid is added to the solution so that the molar ratio is 1: 1 with respect to titanium tetraisopropoxide. did. Subsequently, distilled water was added to the solution so that the molar ratio with respect to titanium tetraisopropoxide was 1: 1.

  Next, the above-mentioned titanium oxide powder was added to the above solution to prepare a suspension, and this suspension was diluted twice with 2-propanol to prepare a sol solution. The amount of the titanium oxide powder added to the solution was added so that the concentration when the sol solution was obtained was 3% by mass.

(Formation of photoelectric conversion layer)
The first electrode having the above surface layer was placed on a hot plate heated to 140 ° C., and the sol solution was applied onto the first electrode by a dropping method, followed by drying treatment. This process is repeated three times to form a photoelectric conversion layer containing titanium oxide having an average thickness of 30 μm adjacent to the first electrode, and further, commercially available flexible PEN (polyethylene naphthalate having a thickness of 75 μm). ) The resin was bonded to the side opposite to the side where the photoelectric conversion layer of the first electrode was formed. Thus, the laminated body which has a board | substrate, the 1st electrode of a grid structure, and a photoelectric converting layer was formed.

(Adsorption of photosensitizing dye)
Next, a solution prepared by dissolving Rutenium 535-bisTBA (manufactured by Solaronics), which is a photosensitizing dye, in an acetonitrile / t-butanol mixed solution (mass ratio 1: 1) until saturated is prepared in advance. The laminate was immersed in the solution. Then, the said laminated body was taken out from the said solution, naturally dried, acetonitrile and t-butanol were volatilized, and also the drying process was performed for 30 minutes in the clean oven heated at 80 degreeC. In this way, the photosensitizing dye was adsorbed and bonded along the outer surface of titanium dioxide and the inner surface of the hole contained in the photoelectric conversion layer.

(5) Formation of hole transport layer Next, an aromatic amine compound (2,2 ′, 7,7′-tetrakis (N, N-di-p-methoxyphenylamine) 9,9 which is a hole transport material is used. A coating solution for forming a hole transport layer in which '-spirobifluorene) is dissolved in tetrahydrofuran is prepared in advance. Then, the coating liquid for forming the hole transport layer is applied to the upper surface of the photoelectric conversion layer on which the above-described photosensitizing dye is adsorbed and bonded by spin coating, and subjected to vacuum drying for 10 minutes. Was removed to form a hole transport layer. The coating liquid for forming the hole transport layer was applied with the spin coat rotation speed set to 500 rpm.

(6) Formation of 2nd electrode Next, the 2nd electrode was produced by forming the film | membrane of gold | metal | money (Au) with the vapor deposition method on the upper surface of the positive hole transport layer formed in the said procedure. By the above procedure, a flexible PEN (polyethylene naphthalate) substrate, a grid-structured first electrode, a photoelectric conversion layer containing titanium dioxide adsorbing the dye-sensitizing dye, and the aromatic amine compound A “photoelectric conversion element 1” having a stacked structure including a hole transport layer and a second electrode made of gold was prepared.

1-2. Production of “Photoelectric Conversion Elements 2 to 11” (1) Production of “Photoelectric Conversion Element 2” When the above-mentioned stainless steel grid electrode was pickled in the production of “photoelectric conversion element 1”, 2% hydrofluoric acid, “Photoelectric conversion element 2” was prepared in the same procedure except that an acidic mixed solution of 5% sodium chlorate and 10% sulfuric acid was used.

(2) Production of “Photoelectric Conversion Element 3” Same as the production of “Photoelectric Conversion Element 1” except that the solvent of the surface layer forming coating solution applied to the stainless steel grid electrode was changed to 2-ethoxyethanol. “Photoelectric conversion element 3” was prepared according to the procedure.

(3) Production of “Photoelectric Conversion Element 4” In the production of the “photoelectric conversion element 1”, the same procedure was followed except that the above-described pickling treatment and surface layer formation were not performed on the stainless steel grid electrode. A photoelectric conversion element 4 ”was produced.

(4) Production of “Photoelectric Conversion Element 5” “Photoelectric conversion element 5” was produced in the same procedure as the production of “photoelectric conversion element 1” except that the above-described pickling treatment was not performed on the stainless steel grid electrode. Produced.

(5) Production of “photoelectric conversion element 6” “Photoelectric conversion element 6” was produced in the same procedure as the production of “photoelectric conversion element 1” except that the above-described surface layer was not formed on the stainless steel grid electrode. Was made.

(6) Preparation of “photoelectric conversion elements 7 to 9” In preparing the “photoelectric conversion element 1”, when preparing a coating solution for forming a surface layer to be applied to the grid electrode made of stainless steel subjected to the pickling treatment, Instead of diethanolamine, triethanolamine was added at a molar ratio of 3: 1 to titanium tetraisopropoxide. Other than that, “photoelectric conversion element 7” was prepared in the same procedure.

  In preparing the “photoelectric conversion element 1”, when preparing a coating solution for forming a surface layer to be applied to the above-described pickled stainless steel grid electrode, acetic acid is replaced by titanium tetraisopropoxide instead of diethanolamine. The molar ratio was 1: 1. Other than that, “photoelectric conversion element 8” was produced in the same procedure. Further, in preparing the “photoelectric conversion element 1”, when preparing a coating solution for forming a surface layer to be applied to the above-mentioned pickled stainless steel grid electrode, acetylacetone is replaced with titanium tetraisopropoxide instead of diethanolamine. The molar ratio was 1: 1. Other than that, “photoelectric conversion element 9” was produced in the same procedure.

(7) Production of “Photoelectric Conversion Element 10” In preparing the “photoelectric conversion element 1”, when preparing a coating solution for forming a surface layer to be applied to the above-described pickled stainless steel grid electrode, titanium tetra It was prepared by dissolving titanium oxyacetylacetonate in 2-propanol instead of isopropoxide. At this time, it added so that the density | concentration in 2-propanol of titanium oxyacetylacetonate might be 0.5 mol / liter. In addition, diethanolamine was not added to the solution. Other than that, “photoelectric conversion element 10” was produced in the same procedure.

(8) Production of “photoelectric conversion element 11” In the production of “photoelectric conversion element 1”, a coating solution for forming a surface layer applied to the above-described stainless steel grid electrode subjected to the pickling treatment was used as titanium tetraisopropoxide. Diethanolamine was not added to a solution obtained by dissolving the simple substance in 2- (n-butoxy) ethanol. Other than that, “photoelectric conversion element 11” was produced in the same procedure.

(9) Production of “Photoelectric Conversion Element 12” In the production of “photoelectric conversion element 1”, a commercially available SUS316 plate material having a thickness of 40 μm was punched by a known method instead of the linear SUS316 steel having a diameter of 30 μm. A stainless steel grid electrode having the shape shown in FIG. Note that the aperture ratio of the grid electrode was set to 85%. Further, a treatment solution used when pickling the stainless steel grid electrode is a commercially available pickling solution “Las Nonwell P-500 (manufactured by Keisho Co., Ltd.)” in which hydrofluoric acid (HF) and nitric acid are mixed. Was changed. Other than that, “photoelectric conversion element 12” was produced in the same procedure. The commercially available pickling solution “Lasnon Well P-500” had a nitric acid concentration of 13.5% and a hydrofluoric acid concentration of 3.7%.

  The production conditions of “photoelectric conversion elements 1 to 11” produced by the above procedure are shown in Table 1 below.

2. Evaluation Experiment Evaluation is performed 100 times in photoelectric conversion efficiency η in the initial state and constant speed temperature change (heat cycle test) in which 50 ° C. is repeated for 1 hour and −20 ° C. for 1 hour with a conversion time of 2 hours. Thereafter, the photoelectric conversion efficiency η was measured, and the difference (decrease width) Δη in photoelectric conversion efficiency was calculated. The evaluation was performed by irradiating each photoelectric conversion element with simulated sunlight having an irradiation intensity of 100 mW / cm ² formed by a commercially available solar simulator “WXS-85-H (manufactured by Wacom Denso Co., Ltd.)”. is there. The simulated sunlight is formed by passing xenon lamp light through an AM filter (AM1.5) by the solar simulator.

  First, the current-voltage characteristic of each photoelectric conversion element at the time of irradiation of the pseudo sunlight under a room temperature environment (temperature 20 ° C.) is measured using a commercially available IV tester, and the short-circuit current value Isc and the open circuit voltage are measured. The shape factor FF was calculated from Voc and the current-voltage characteristic graph. And the photoelectric conversion efficiency was computed from the calculation formula mentioned later using these values. Next, after standing for 240 hours in a dark place at a temperature of 85 ° C., pseudo-sunlight irradiation is performed again under the same conditions as above, and the short-circuit current value Isc, the open-circuit voltage Voc, and the shape factor FF are calculated. The photoelectric conversion efficiency η was calculated. Thus, while evaluating the fluctuation | variation of photoelectric conversion efficiency, the presence or absence of the liquid leak generation | occurrence | production after dark storage was evaluated.

  Here, “open circuit voltage Voc” in the evaluation item is a voltage at which no current flows when a voltage load is applied to the photoelectric conversion element, and “short circuit current value Isc” is a voltage applied to the photoelectric conversion element. This is the value of the current that flows when no load is applied. Furthermore, the “shape factor FF” is a value obtained by dividing Pmax by the product of the short-circuit current value Isc and the open-circuit voltage Voc in a voltage-current characteristic graph when measuring the photoelectric conversion efficiency described later. FIG. 3 shows the relationship between the numerical value of “shape factor FF” and the shape of “voltage-current characteristic graph”.

Further, the photoelectric conversion efficiency η in the evaluation item is calculated from the following formula. That is, from the solar simulator, the short-circuit current of each photoelectric conversion element obtained by irradiating pseudo solar light with an AM1.5 filter and an irradiation intensity of 100 mW / cm ² is Isc (mA / cm ² ), and the open-circuit voltage is Voc ( V), the photoelectric conversion efficiency η (%) when the shape factor is FF (%),
η (%) = Isc (mA / cm ² ) × Voc (V) × FF (%)
It is calculated from.

  The photoelectric conversion efficiency η after the initial state and the heat cycle test were both 4.00% or more, and the photoelectric conversion efficiency decrease width Δη was 0.50% or less. The above results are shown in Table 2 below.

  As shown in Table 2, “Examples 1 to 9” using “photoelectric conversion elements 1 to 3 and 7 to 12” having the configuration of the present invention are all the same as the initial state after the heat cycle test. Photoelectric conversion efficiency was obtained, and it was confirmed that it could be used even under conditions of repeated temperature changes between high and low temperatures. That is, in “Examples 1 to 9”, there is no fear that the grid electrode peels off from the photoelectric conversion layer even in an environment where temperature changes between high and low temperatures are repeated, and stable photoelectric conversion efficiency due to good adhesion between the two. It was confirmed that the photoelectric conversion element of the grid electrode which can express this is obtained. On the other hand, in “Comparative Examples 1 to 3” in which pickling treatment and surface layer formation were not performed on the stainless steel grid electrode, stable photoelectric conversion efficiency as obtained in “Examples 1 to 9” was not expressed. .

DESCRIPTION OF SYMBOLS 1 Photoelectric conversion element 3 1st electrode (grid electrode)
3A Surface layer 4 Second electrode 5 Photoelectric conversion layer 6 Hole transport layer 7 Substrate 12 Sunlight

Claims (14)

A photoelectric conversion element having at least a first electrode, a photoelectric conversion layer, a hole transport layer, and a second electrode,
The first electrode is
It is a grid electrode made of stainless steel that has been pickled and has a surface layer,
The photoelectric conversion element, wherein the surface layer contains a semiconductive compound. The surface layer is
The photoelectric conversion element according to claim 1, wherein the semiconductive compound contains a titanium oxide compound. The titanium oxide compound contained in the surface layer is
The titanium alkoxide compound alone, a mixture of a titanium alkoxide compound and an amine compound, or a mixture of a titanium alkoxide compound and an organic compound having a carboxyl group or a carbonyl group is heated to form the alkoxide compound. Or the photoelectric conversion element of 2.   The photoelectric conversion element according to claim 1, wherein the titanium oxide compound contained in the surface layer is formed by thermally decomposing a titanium alkoxide complex compound.   The stainless steel grid electrode is formed by performing the pickling treatment through a step of immersing in a solution containing at least hydrofluoric acid (HF). The photoelectric conversion element of Claim 1.   The photoelectric conversion element according to any one of claims 1 to 5, wherein the stainless steel grid electrode is formed using a linear stainless steel member.   The photoelectric conversion element according to claim 1, wherein the stainless steel grid electrode is formed using a plate-like stainless steel member. A method for producing a photoelectric conversion element having at least a first electrode, a photoelectric conversion layer, a hole transport layer, and a second electrode,
The first electrode is
It is made of stainless steel grid electrodes,
A method for producing a photoelectric conversion element, comprising at least a step of performing a pickling treatment and a step of forming a surface layer containing a semiconductive compound. The surface layer is
The method for producing a photoelectric conversion element according to claim 8, wherein the semiconductive compound contains a titanium oxide compound. The titanium oxide compound contained in the surface layer is
Either a titanium alkoxide compound alone, a mixture obtained by adding an amine compound to a liquid containing a titanium alkoxide compound, or a mixture obtained by adding an organic compound having a carboxyl group or a carbonyl group to a liquid containing a titanium alkoxide compound is heated. The method for producing a photoelectric conversion element according to claim 8, wherein the photoelectric conversion element is formed.   The method for producing a photoelectric conversion element according to claim 8 or 9, wherein the titanium oxide compound contained in the surface layer is formed by thermally decomposing a liquid containing a titanium alkoxide complex compound. .   The step of pickling the stainless steel grid electrode is performed by immersing the stainless steel grid electrode in a solution containing at least hydrofluoric acid (HF). The manufacturing method of the photoelectric conversion element of any one of Claims 1.   The method for manufacturing a photoelectric conversion element according to any one of claims 8 to 12, wherein the stainless steel grid electrode is formed using a linear stainless steel member.   The method for manufacturing a photoelectric conversion element according to any one of claims 8 to 12, wherein the stainless steel grid electrode is formed using a plate-like stainless steel member.

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