JP2003298082A - Composite semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element exhibiting a high open voltage (Voc) and a high functional factor (F.F.) and a photochemical cell employing it. <P>SOLUTION: Surface of a crystalline n-type semiconductor is coated with at least any one kind of metal carbonate, metal oxide and metal titanate to produce a composite semiconductor and a film of semiconductor containing the composite semiconductor is formed on a conductive support, thus producing the photoelectric conversion element. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composite semiconductor and a photoelectric conversion element using the same. Furthermore, it relates to a photochemical cell using the device.

[0002]

2. Description of the Related Art In recent years, as environmental energy problems such as global warming caused by an increase in carbon dioxide generation and burning of fossil fuels have become serious, as a countermeasure, infinite solar energy that does not generate harmful substances is used efficiently. The development of technology to extract it as an energy source is being actively conducted. Above all, a photochemical cell, which is excellent in both efficiency and cost, has been attracting attention in place of the conventional high cost pn silicon solar cell.

Among the photochemical cells, Michael G
publicized by ratzel et al. (Nature
1991, 353, 737-740) Dye-sensitized wet solar cells are extremely low in cost and highly efficient, and many studies have been conducted since the publication. The dye-sensitized wet type solar cell is an indium oxide-based film (IT) having excellent conductivity and transparency on a support such as glass or polymer.
O) or fluorine doped tin oxide film (FTO)
On a substrate (conductive support) coated with, a photoelectric conversion element in which a film having a porous structure of titanium oxide of several tens of nanometer size which is an inexpensive material is laminated as an n-type oxide semiconductor is used as a cathode, A general structure is one in which an anode having a platinum thin film laminated on a similar substrate is used, and the cathode and the anode are arranged mainly via an electrolytic solution containing redox ions such as iodine.

The cathode often carries a photosensitizer represented by a complex dye in order to absorb light having a wavelength in the visible region of sunlight and generate excited electrons. Excited electrons generated from the photosensitizer move to the n-type oxide semiconductor and further to the anode through the lead wire connecting both electrodes. The electrons that have moved to the anode reduce the electrolytic solution, and the electrolytic solution releases the electrons to reduce the photosensitizer in the oxidized state.
The dye-sensitized wet solar cell functions by repeating such a series of flows. In a photochemical cell such as a dye-sensitized wet solar cell, an excited electron transferred to a semiconductor is recombined with a photosensitizer in an oxidized state in the process of moving to a conductive support, There has been a problem that the photoelectric conversion performance of the battery is deteriorated by the recombination with the redox ions of the electrolytic solution in an oxidized state and the decrease in voltage.

In order to solve this problem, Kirthi
Tennakone et al., A so-called core, in which tin oxide (core) is coated (shell) with an insulating compound of magnesium oxide or aluminum oxide having a thickness of several nanometers.
It was shown that the photoelectric conversion element using the shell-type n-type oxide semiconductor improves the performance of the photoelectric conversion element formed of fine particles of tin oxide (Jpn. J. App.
l. Phys. Vol. 40.2001,353, p
p. L732-734) (J. Phys. D: App.
l. Phys. 34.2001, 868-873). However, in this technique, the voltage remained at about 650 mV, and it cannot be said that a sufficient voltage was obtained.

Further, in JP-A-2000-113913 and JP-A-2001-155791, a core-shell type oxide fine particle in which an oxide semiconductor is used as a core and titanium oxide is used as a shell is used as a semiconductor. Is disclosed. In these technologies, electrons injected into the core part are injected into the shell part because the resistance of the shell part is higher than the resistance of the core part or the conduction band level of the shell part is higher than the conduction band level of the core part. The purpose of this is to reduce the probability of recombination with the photosensitizer in the oxidized state and the redox ion in the electrolyte in the oxidized state. However, since titanium oxide is used for the shell, there is a problem that the production is not easy.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a composite semiconductor that can be easily manufactured and can obtain a high open circuit voltage (Voc), as compared with a conventional photoelectric conversion device in which n-type semiconductors are stacked. , And to provide a photoelectric conversion element and a photochemical cell using the same.

[0008]

The inventors of the present invention have made extensive studies in order to solve the above-mentioned problems, and as a result, have found that a crystalline n-type semiconductor is used as a core and the surface of the core is a metal carbonate, a metal oxide or titanium. A photoelectric conversion element having a high open circuit voltage (Voc) and a high fill factor (FF) can be obtained by using a composite semiconductor coated with a shell made of any one or more of acid metal salts. This has led to the present invention.

That is, the present invention (1) is a composite semiconductor characterized in that the surface of a crystalline n-type semiconductor is coated with one or more of metal carbonate, metal oxide and metal titanate. (2) A composite semiconductor, wherein the crystalline n-type semiconductor according to (1) is crystalline titanium oxide. (3) The composite semiconductor according to (1) or (2), wherein the metal of the metal carbonate, the metal oxide and the metal titanate is an alkaline earth metal or an alkali metal.

(4) A photoelectric conversion element comprising a film of the composite semiconductor according to any one of (1) to (3) laminated on a conductive support. (5) A photoelectric conversion element, wherein the semiconductor film according to (4) further contains a photosensitizer. (6) A photochemical cell, wherein the photoelectric conversion element according to any one of (4) and (5) is opposed to a counter electrode via an electrolyte layer.

The present invention will be described in detail below. First, details of the composite semiconductor of the present invention will be described. The composite semiconductor of the present invention has a crystalline n-type semiconductor as a core, and the core has a surface covered with one or more kinds of metal carbonate, metal oxide and metal titanate. To do. The present invention can greatly reduce the probability of recombination with the redox ions in the photosensitizer in the oxidation state or the electrolyte in the oxidation state by using the specific material for the shell as described above, and as a result, a high open-circuit voltage. (Voc) is obtained. Furthermore, it has achieved that a high fill factor (FF) is also obtained.

The composite semiconductor of the present invention has a fine particle structure composed of a shell part in which the surface of primary particles of crystalline n-type semiconductor is coated with a specific material as the core part, or the crystalline structure which constitutes the core part. The structure may be composed of a shell part in which the surface of a sintered body obtained by previously sintering and integrating the n-type semiconductor particles is coated with a specific material, or a structure in which these are combined. . The crystalline n-type semiconductor used for the core of the composite semiconductor of the present invention preferably has a primary particle size of 1 to 5000 nm, more preferably 2 to 100 nm, and further preferably 2 to 50 nm.
Is. That is, if the primary particle diameter is larger than 5000 nm, the light transmittance of the semiconductor film may be deteriorated and the incident light may not be effectively used. Also, in the case where the primary particle diameter is less than 1 nm. This is because there is a case that the loss in transferring the excited electrons generated by the decrease in the electronic conductivity of the semiconductor particles to the conductive support described later becomes large.

The composite semiconductor of the present invention is laminated as a part of a film on a conductive support to be described later to form a photoelectric conversion element. When the composite semiconductor has a fine particle structure, a film structure obtained by sintering fine particles is used. Therefore, it has a porous structure. Further, even if the surface of the crystalline n-type semiconductor particles is coated with a specific material after being sintered and integrated into a film structure, it has a porous structure. Therefore, the film of the composite semiconductor constituting the photoelectric conversion element of the present invention has a large contact area with the electrolyte, and when the photosensitizer is used as a carrier, the amount of the carrier is increased and the photoelectric conversion performance is not only improved. In addition, the effect of reducing the probability of recombination with the photosensitizer in the oxidized state and the redox ion in the electrolyte in the oxidized state due to the presence of the shell portion becomes more remarkable.

In the present invention, the porous structure means, for example, that the surface where the particles are present is projected on a plane by the increase of the surface area calculated from the surface area per mass obtained by BET surface area measurement using nitrogen gas. The area is 5 times or more the area. In the present invention, in the case where the surface of the sintered body as a core portion in which crystalline n-type semiconductor particles are sintered and integrated in advance is coated with a specific material to form a shell portion, the electron conductivity is excellent. Therefore, it may be preferably used.

The crystalline n-type semiconductor used in the core portion of the composite semiconductor of the present invention is titanium oxide, tin oxide, zinc oxide, indium oxide, niobium oxide, tungsten oxide,
Various oxide semiconductors such as vanadium oxide, various composite oxide semiconductors such as strontium titanate, calcium titanate, barium titanate, and potassium niobate,
It is an n-type semiconductor having crystallinity such as sulfides of cadmium and bismuth, selenides and tellurides of cadmium, phosphides of gallium, and arsenides of gallium, and these can be used in combination. . Among these, crystalline titanium oxide is preferable from the viewpoints of easiness of sintering and high photoelectric conversion ability.

When crystalline titanium oxide is used as the crystalline n-type semiconductor, it may be any one of anatase type titanium oxide, rutile type titanium oxide and brookite type titanium oxide, or a mixture of two or more of the above titanium oxides. Although it does not matter, when the titanium oxide is a mixture of two or more kinds, the ratio is not particularly limited, but the anatase type titanium oxide is preferably 50% by mass or more.

In the present invention, the anatase-type titanium oxide is observed at a peak intensity ratio of each crystal face of (101) (200) (004) by X-ray diffraction at an intensity ratio of about 100: 35: 20. It is crystalline titanium oxide, and rutile type titanium oxide has a peak intensity ratio of each crystal plane of (110) (211) (101) in X-ray diffraction of about 100: 6.
It is crystalline titanium oxide observed at an intensity ratio of 0:50, and brookite type titanium oxide is (120)
This is crystalline titanium oxide whose peak intensity ratio of each of the (121) and (111) crystal faces is observed by X-ray diffraction at an intensity ratio of about 100: 90: 80.

The degree of crystallinity of the crystalline titanium oxide used in the present invention is not particularly limited as long as the above-mentioned peaks are observed by X-ray diffraction, but a higher degree is preferable. This is because the photoelectric conversion performance of the semiconductor film is largely due to the crystallinity of the semiconductor particles forming the film, and the higher the crystallinity, the higher the electron conductivity and the higher activity.

The crystallinity of the crystalline titanium oxide of the present invention will be described below.
The degree will be described by taking anatase type titanium oxide as an example. Conclusion
When the crystalline titanium oxide is anatase type titanium oxide,
Half of the X-ray diffraction peak of the (101) plane, which is the main peak
The valence range is preferably 1.3 ° or less, more preferably 0.
It is 75 ° or less, most preferably 0.30 ° or less. This
These X-ray diffraction measurements are performed using, for example, a powder X-ray diffractometer.
Cu K as the radiation source _αLines are used
It Titanium oxide of types other than anatase type is also bound from the half-value width.
The degree of crystallinity can be similarly indicated. This is
For semiconductors with high crystallinity, the sintering process described later
Alternatively, it can be obtained by firing the semiconductor in advance.
It is possible.

Next, materials constituting the shell portion of the composite semiconductor of the present invention will be described. The material forming the shell portion of the composite semiconductor of the present invention is any one of metal carbonate, metal oxide and metal titanate, and these can be used in combination. The present invention achieves high voltage and high fill factor due to the presence of the shell made of these particular materials.

In the present invention, the metal carbonate is not particularly limited as long as it is a carbonate of a metal element, and alkali metal carbonates such as lithium carbonate, sodium carbonate and potassium carbonate,
Alkaline earth metal carbonates such as magnesium carbonate, calcium carbonate, strontium carbonate and barium carbonate, transition metal carbonates such as cobalt carbonate, nickel carbonate and manganese carbonate, lanthanide carbonates such as lanthanum carbonate, ytterbium carbonate and cerium carbonate. It can be illustrated.

In the present invention, the metal oxide is not particularly limited as long as it is an oxide of a metal element, and alkali metal oxides such as lithium oxide, sodium oxide and potassium oxide,
Alkaline earth metal oxides such as magnesium oxide, calcium oxide, strontium oxide and barium oxide, transition metal oxides such as cobalt oxide, nickel oxide and manganese oxide, lanthanoid oxides such as gadolinium oxide, samarium oxide and ytterbium oxide. It can be illustrated.

In the present invention, the metal titanate is not particularly limited as long as it is a titanate of a metal element, and alkali metal titanate represented by sodium titanate, magnesium titanate, strontium titanate, titanic acid. Examples thereof include calcium, barium titanate and other alkaline earth metal titanates, lead titanate, neodymium titanate, cadmium titanate and the like. Among these, it is more preferable that the metal forming the metal carbonate, metal oxide or metal titanate is an alkaline earth metal such as magnesium, calcium, strontium or barium or an alkali metal such as lithium, sodium or potassium. It is preferable because a voltage can be obtained. It should be noted that any material is not limited to crystalline or amorphous.

The material forming the shell in the present invention is
The resistance value thereof is preferably larger than the resistance value of the crystalline n-type semiconductor forming the core portion. In addition, when the shell is an n-type semiconductor such as an alkaline earth metal titanate, prevention of outflow of electrons in the crystalline n-type semiconductor of the core part,
The conduction band level of the shell is preferably higher than that of the crystalline n-type semiconductor of the core in order to enable the development of a higher open circuit voltage value. In particular, when the core portion is titanium oxide, an alkaline earth metal titanate is preferable as the n-type semiconductor forming the shell from the viewpoint of high conduction band level and ease of production, and more preferably titanic acid. It is calcium.

In the present invention, the shell portion of the composite semiconductor is
The core may be completely covered or partially covered, but its thickness is obtained as an average value of the thickness of the shell. Specifically, a transmission electron microscope (TE
M) for direct observation, or using X-ray photoelectron spectroscopy (XPS) whose measurement depth is generally 5 nm or less, a specific element of the n-type semiconductor constituting the core (for example, When the n-type semiconductor constituting the core is titanium oxide, titanium and a specific element of the material forming the shell (for example,
In the case of calcium carbonate, it can also be calculated using the atomic ratio of (calcium) and the specific gravity of the shell found from the composition of the shell obtained by the method described below. It should be noted that the specific element selected for obtaining this atomic ratio is for ease of analysis (small peak overlap, strong peak intensity, and preferably present only in one of the core / shell). It is selected as appropriate.

The composition distribution is determined while etching using an apparatus such as time-of-flight secondary ion mass spectrometry (TOF-SIMS), and the shell thickness is calculated by using the etching thickness until the change in the composition becomes apparent. You can also ask. More simply, it can be calculated from the specific gravities of the materials of the shell portion and the core portion, the amounts of the raw materials used, and the average particle diameter of the core particles. The thickness of the shell is not particularly limited as long as the voltage can be improved, but it is preferably 0.1 nm or more, more preferably 0.4 nm or more. This is because if it is thinner than 0.1 nm, the voltage improving effect may be insufficient, and if it is 0.4 nm or more, the voltage improving effect becomes more remarkable. On the other hand, with respect to the upper limit, a range not exceeding the radius of the core particles used is preferably used,
It is preferably less than 5 nm, more preferably less than 3 nm.

In the case of a thin region where the thickness of the shell portion is less than 0.4 nm, it may be difficult to analyze its composition by X-ray diffraction. The composite semiconductor formed by the operation and the semiconductor composed of the core portion thereof are measured by XPS, and it is possible to determine whether or not the shell portion of the present invention is formed by the difference between them. In addition, for the sake of simplicity, a shell having a thickness of 0.4 nm or more is formed and analyzed using an X-ray diffractometer or the like, and the same raw material and operation as in the case where the shell structure is specified are used to add the shell-forming material. When the thickness is controlled by the amount, it can be determined that the material has a structure similar to that of the shell formed to 0.4 nm or more.

Next, a semiconductor film containing a composite semiconductor which constitutes the photoelectric conversion element of the present invention will be described. As shown in FIG. 1, the photoelectric conversion element of the present invention is a semiconductor film 2 containing a composite semiconductor of the present invention on a transparent conductive film 4 of a conductive support composed of a transparent substrate 1 and a transparent conductive film 4. Are laminated. The semiconductor film of the present invention contains the composite semiconductor of the present invention in an amount of 1% by mass or more based on the entire semiconductor film. The mass fraction of the composite semiconductor with respect to the entire semiconductor film is preferably 30% by mass or more, more preferably 50% by mass or more, and most preferably 70% by mass or more because the effect of improving the voltage becomes more remarkable. The upper limit is not particularly limited, but since the semiconductor film preferably contains a photosensitizer as described below, the upper limit is preferably 99% by mass or less, more preferably 98% or less, Most preferably it is 96% or less. The semiconductor film of the present invention also includes a semiconductor film composed only of the composite semiconductor of the present invention and a photosensitizer.

Various semiconductors other than the composite semiconductor of the present invention can be added to the semiconductor film of the present invention. Specifically, amorphous titanium oxide, titanium peroxide having anatase type low crystallinity, anatase type low crystalline titanium oxide, rutile type titanium oxide, brookite type titanium oxide,
Various oxide semiconductors such as zinc oxide, tin oxide, indium oxide, niobium oxide, tungsten oxide, vanadium oxide, strontium titanate, calcium titanate,
Various complex oxide semiconductors such as barium titanate and potassium niobate, sulfides of cadmium and bismuth, selenides and tellurides of cadmium, gallium phosphide, gallium arsenide, and other semiconductors. . Further, these may be used in combination.

In the semiconductor film of the present invention, in addition to the above semiconductors, if necessary, an organic binder such as acetylacetone in an amount not deteriorating the performance of the photoelectric conversion element,
Inorganic binders such as metal peroxides (eg titanium peroxide, tin peroxide, niobium peroxide) and metal alkoxides, inorganic substances such as nitric acid and sulfuric acid, polymer compounds such as polyethylene glycol, polypropylene glycol, cellulose and its modified products, It is also possible to add various surfactants such as nonionic, anionic, cationic and silicone type, and chelate auxiliary agents.

The semiconductor film of the present invention preferably contains a photosensitizer for the purpose of more efficiently absorbing light in the visible light region and obtaining high photoelectric conversion performance. The photosensitizer of the present invention is not particularly limited as long as it has the ability to absorb light, but when used as a photochemical cell, it is preferable that it has good absorption characteristics in the wavelength range of sunlight, and absorbs visible light. The thing is more preferable. The wavelength of visible light here is about 4
The range is from 00 nm to about 800 nm. Specific examples thereof include dyes and metal fine particles, but dyes that absorb incident light to be in an excited state and form pairs of holes and electrons are preferable. Further, it is desirable that the LUMO level of the dye is located above the conduction band level of the semiconductor. This is because electrons can be injected more efficiently into the semiconductor film.

When the dye used in the photosensitizer of the present invention is carried on the semiconductor film, its bonding form is not particularly limited, but preferably it is chemically bonded such as chelate bond or ester bond in the semiconductor film. Is desirable. Therefore, those having a reactive functional group such as a carboxyl group, a carboxyalkyl group, a hydroxyl group, a hydroxyalkyl group, a sulfonic acid group and a phosphoric acid group in the molecule are preferable. The dye is
Although both a metal complex and an organic molecule are possible, a metal complex that is excellent in light resistance and spectral sensitization effect is preferable.

In the metal complex, the central metal is, for example, ruthenium, osmium, iron, copper, nickel, cobalt,
Palladium or the like can be used, and the ligand preferably contains a π-conjugated system, and examples thereof include a bipyridine derivative, a terpyridine derivative, a phenanthroline derivative, and a quinoline derivative. Furthermore, in addition to the ligand described above,
Those in which a thiocyanate group, a cyan group, a chloro group, a bromo group and the like are coordinated are preferable. Further, it is not limited to a mononuclear complex and may be a polygonal complex. In addition to the above, phthalocyanine-based complex,
Examples include porphyrin-based complexes.

Examples of organic molecules include rhodamine B,
A xanthene dye such as rose bengal, eosin and erythrosine, a cyanine dye such as quinocyanine and cryptocyanine, a basic dye such as phenosafranine, thiocin and methylene blue, an anthraquinone dye, a polycyclic quinone dye and the like can be used. The above-mentioned photosensitizers may be used alone or in combination of two or more kinds.

In the present invention, the supported amount of the dye as the photosensitizer is determined by converting the dye amount from the absorbance of the dye by UV-visible absorption spectrum measurement. Further, when a semiconductor other than the composite semiconductor of the present invention, which is optionally added, is mixed in the semiconductor film, the photosensitizer can be adsorbed to these as well. At that time, all the photosensitizers adsorbed on all the substances mixed in the semiconductor film are defined as the photosensitizer amount in the present invention. The photosensitizer may be preliminarily supported on the composite semiconductor as described above, may be supported after forming a semiconductor film containing the composite semiconductor, or may be supported after sintering the semiconductor film. Furthermore, the n-type semiconductor primary particles of the core portion or the sintered body obtained by previously sintering the particles of the core portion may carry the photosensitizer, and then may have a shape in which the material of the shell portion described above is coated.

Next, the transparent substrate and the transparent conductive film which constitute the conductive support for laminating the semiconductor film of the present invention will be described below. In the present invention, “transparent” means that the light transmittance is 10% or more, preferably 50% or more, and particularly preferably 70% or more. As the transparent substrate used in the present invention, the above-mentioned transparent glass or organic substance can be used and is not particularly limited.

Specifically, examples of organic substances include transparent polymer films such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN),
Syndiotactic polystyrene (SPS), polyphenylene sulfide (PPS), polyarylate (PA
r), polysulfone (PSF), polyethersulfone (PES), polyetherimide (PEI), polycarbonate (PC), tetraacetyl cellulose (T
AC), polymethylmethacrylate (PMMA) and the like can be used. On the other hand, the transparent conductive film may be any one having the above-mentioned transparency, and a preferable example thereof is a metal oxide semiconductor, for example, ITO (In-Sn-O).
Compounds), FTO (tin oxide doped with fluorine, etc.), zinc oxide and the like are preferable.

The method for producing the photoelectric conversion element in which the composite semiconductor of the present invention and the semiconductor film containing the composite semiconductor of the present invention are laminated on a conductive support will be described in detail below. The composite semiconductor of the present invention is manufactured by coating the material used for the core part with the material used for the shell part in advance and by manufacturing the compound used for the core part by sintering and integrating the material used for the shell part. The method can be roughly divided into two methods, but an organic or inorganic metal compound that is a precursor of the material used for the shell portion can also be used. In the case of a method of manufacturing by sintering the material used for the core part and coating the material used for the shell part, it becomes possible to manufacture a composite semiconductor in the process of manufacturing the semiconductor film of the present invention. .

The following four specific manufacturing methods will be illustrated. The first method is a step of producing composite semiconductor particles,
A step of preparing a dispersion liquid containing the particles of the composite semiconductor, a coating step of coating the dispersion liquid on a conductive support, and a subsequent sintering step to form a semiconductor film on the conductive support, and further desired Is a method for producing a photoelectric conversion element by the order of an adsorption step of adsorbing the photosensitizer in the semiconductor film.

The second method is a step of preparing a dispersion liquid containing a core material and a shell material of the composite semiconductor or a precursor thereof without preparing a particulate composite semiconductor in advance, and the dispersion liquid is electrically conductive. Coating step of coating on a flexible support, a subsequent sintering step (a semiconductor film is formed at the same time when a composite semiconductor is formed in this step), and an adsorption step of adsorbing a photosensitizer into the semiconductor film, if desired. It is a method of manufacturing a photoelectric conversion element in the order of.

The third method is a step of preparing a dispersion liquid containing the core material of the composite semiconductor without preparing a particulate composite semiconductor in advance, and coating the dispersion liquid on a conductive support. A process, optionally a subsequent drying or sintering process,
Then, the shell material or the precursor thereof is attached by a method such as dipping in a solution or a dispersion liquid of the shell material or a precursor thereof, or applying a solution or a dispersion liquid of the shell material or a precursor thereof, and if desired, A method for manufacturing a photoelectric conversion element by the steps of re-sintering (a semiconductor film is formed at the same time when a composite semiconductor is formed in this step) and, if desired, an adsorption step of adsorbing a photosensitizer in the semiconductor film. Is.

The fourth method is a step of preparing a dispersion liquid containing a core material of the composite semiconductor without preparing a particulate composite semiconductor in advance, and applying the dispersion liquid onto a conductive support. A process, optionally a subsequent drying or sintering process,
Next, if desired, an adsorption step of adsorbing the photosensitizer in the film, followed by dipping in a solution or dispersion of the shell material or its precursor, or applying a solution or dispersion of the shell material or its precursor. A method of manufacturing a photoelectric conversion element by the steps of depositing a shell material or a precursor thereof by a method such as the above and sintering again if desired (in this step, a semiconductor film is simultaneously formed with a composite semiconductor). is there.

As the precursor of the shell material described above, an organic metal compound or an inorganic metal compound is preferably used. Of the above methods, when the second to fourth methods are used and when the metal titanate salt is produced in the shell part, there is no particular limitation other than the above description as long as the shell part material is used as it is. However, when the shell material is formed from its precursor in the sintering step to produce the desired composite semiconductor, the core portion is preferably crystalline titanium oxide from the viewpoint of ease of sintering. Of these, the third and fourth methods may be preferably used from the viewpoint of excellent electron conductivity when the composite semiconductor of the present invention is used in a photoelectric conversion element. The second method may be preferably used from the viewpoint of ease of production.

The above process conditions will be described in detail below.
First, the process of producing a dispersion liquid will be described. In the present invention, the composite semiconductor, the medium of the dispersion containing the core material or shell material or its precursor is not particularly limited as long as it can maintain a liquid state at room temperature, for example, water, ethanol, methanol, propanol, butanol, Alcohol-based organic solvents such as isopropyl alcohol, acetone, acetonitrile, propionitol,
Examples thereof include hydrophilic organic solvents such as dimethylsulfoxide and dimethylformamide, hydrophobic organic solvents such as dichloromethane, chloroform, carbon tetrachloride, ethyl acetate, diethyl ether, tetrahydrofuran and toluene, and mixtures thereof.

Further, an organic binder such as acetylacetone, a metal peroxide (for example, titanium peroxide, tin peroxide, niobium peroxide, etc.) for the purpose of enhancing the dispersibility of the composite semiconductor or the core material and adjusting the viscosity. )
And inorganic binders such as metal alkoxides, inorganics such as nitric acid and sulfuric acid, polyethylene glycol, polypropylene glycol, polymer compounds such as cellulose and its modified products, various surfactants such as nonionic, anionic, cationic and silicone type, A chelating auxiliary agent can also be added and used.

Further, in order to improve the mixing property in the dispersion liquid, the composite semiconductor used in the present invention or the crystalline n-type semiconductor of the core material may be previously treated as described below. For example, when crystalline titanium oxide is used as the crystalline n-type semiconductor, a nitric acid heat treatment can be performed for several hours to obtain a powder having high dispersibility in the medium. The solid content mass concentration of the dispersion is not particularly limited, the ease of application,
It is appropriately selected depending on the drying speed and the like, but is preferably 10 to 50%, more preferably 15 to 40%.

The mixing conditions for preparing the dispersion are not particularly limited, but a mixing stirrer such as a paint shaker, a ball mill and a homogenizer, an ultrasonic homogenizer and the like can be used for the purpose of more fine dispersion. It is also an effective means to sufficiently pulverize the dispersed particles in advance with a mortar or the like. When the crystalline n-type semiconductor of the core material and the organometallic compound or the inorganic metal compound which is the precursor of the shell material are mixed, they can be dispersed individually or after mixing under the above conditions. When dispersed independently, they can be mixed and used after dispersion, if necessary. When the precursor of the shell material is supplied as a solution, a medium in which the precursor described later is dissolved is used. Specifically, the same medium as the above dispersion liquid can be used.

A metal carbonate,
Although either a metal oxide or a metal titanate is used, as described above, these materials may be used directly, or an organometallic compound or an inorganic metal compound which is a precursor of these materials may be used. good. The organometallic compound and the inorganic metallic compound when the shell part material is supplied as a precursor are
In the subsequent sintering step, there is no particular limitation as long as it can be changed to a material for forming the shell portion, but specifically, the organometallic compound is acetate, oxalate, formate, benzoic acid. Low molecular weight organometallic compounds such as organometallic salts and metal alkoxides of salts, high molecular weight organometallic compounds represented by polyacrylic acid metal salts can be exemplified, and as inorganic metal compounds, nitrates, sulfates, chloride salts, Examples thereof include phosphates and silicates. Further, these materials can be used in combination. Among these, the organometallic compound is preferably a low molecular weight organometallic compound, and most preferably an oxalate, from the viewpoint that the organic substance is unlikely to remain in the semiconductor film. In addition, the inorganic metal compound is preferably a nitrate salt from the viewpoint of the ease of leaving a residue and the safety of the gas generated when overheated by sintering or the like.

Next, the coating process will be described. The method of coating in the present invention is not particularly limited as long as it can form a semiconductor film on a conductive support, and specifically, a screen printing method, a spin coater method, a dip coater method, a doctor blade method, a wire. A coating method using a bar can be exemplified. After application, a step of drying at room temperature may be performed if necessary. Further, when the coating operation is divided into several times and repeated coating is performed, it is preferable to perform the above-described drying step for each coating. Further, the drying step described above may be omitted by performing only the sintering step described below.

Next, the sintering process will be described. In the present invention, the sintering temperature varies depending on the type of semiconductor used, the type of shell, the required degree of sintering, and the heat resistance of the conductive support used, and is appropriately selected according to the purpose. In general,
Higher sintering temperature is preferable because particles can be bonded to each other in a short time and higher conductivity between particles is easily obtained, but depending on the substance, a crystal phase transition may occur to deteriorate photoelectric conversion performance. There is. The type of conductive support is also important in determining the sintering temperature. That is, the conductive support is composed of a transparent substrate and a transparent conductive film, and each has a heat resistant temperature.

For example, an organic material having a low melting point or softening point such as a polymer film is used for the transparent substrate and I is used for the transparent conductive film.
When TO is used, the sintering temperature may be lower than the heat resistant temperature of the polymer film, preferably 250 ° C. or lower, more preferably 200 ° C. or lower. On the other hand, when glass is used for the transparent substrate and FTO is used for the transparent conductive film, the sintering temperature needs to be lower than the heat resistant temperature of glass, and preferably 600 ° C. or lower. The sintering time is preferably 10 minutes or more and 1 hour or less, more preferably 20 minutes or more and 1 hour or less.

The atmosphere gas at the time of sintering is not particularly limited and may be appropriately selected depending on the purpose. Specifically, an inert gas atmosphere such as nitrogen or argon, a reducing atmosphere represented by hydrogen, a mixed gas atmosphere of nitrogen and oxygen, the atmosphere,
Carbon dioxide, oxygen, etc. can be used. Among them, the atmosphere or a mixed gas atmosphere of nitrogen and oxygen is preferably used particularly in the step of supplying the shell material with its precursor to form the shell material during sintering. In this case, the mixing ratio of nitrogen and oxygen can be appropriately selected to obtain the target structure.

The thickness of the sintered semiconductor film formed under the above conditions is preferably 0.5 μm or more and 50 μm or less, more preferably 1.0 μm or more and 30 μm or less. 0.
If the thickness is less than 5 μm, the above-mentioned photosensitizer cannot be sufficiently adsorbed and the energy conversion efficiency cannot be increased. On the other hand, when the thickness is more than 50 μm, the mechanical strength of the semiconductor film itself is lowered and the semiconductor film is easily peeled off from the conductive support, and at the same time, the light transmittance is lowered, resulting in a problem that sufficient light cannot reach the photosensitizer. In addition, the electron transfer path in the semiconductor film becomes long, the internal resistance increases, and the energy conversion efficiency may decrease.

Next, the adsorption step of supporting the photosensitizer in the semiconductor film will be described. Here, details of the case where a dye is used as the photosensitizer will be described. However, if the photosensitizer can be stably adsorbed to the composite semiconductor in the semiconductor film and other substances added as necessary, adsorption is possible. There is no particular limitation on the process.

Below, a dye as a photosensitizer was dissolved.
It is adsorbed by contacting the photoelectric conversion element with the solution.
The adsorption process will be described as an example. Solvents that dissolve dyes are organic
The medium is not particularly limited, but preferably ethanol or dime
Examples include tyl sulfoxide, acetonitrile and the like.
Appropriate dye concentration depends on the type of dye and solvent used
It can be adjusted, for example, 1 × 10 ^-Fivemol / l
Above, further 5 × 10^-Fivemol / l-1 × 10^-2mol
/ L is preferable. Adsorption is performed on the above dye solvent with a semiconductor film.
The method of soaking for a few hours to several days
50 ℃ to 150 ℃ (melting condition)
Adsorption under reflux condition (depending on the medium) is 10 minutes or more and several hours or less.
It can also be done below. Above, either method is possible
However, the latter is more preferable. After adsorption, the film surface
It is preferable to wash the surface with an aprotic or hydrophobic solvent.
Yes.

Next, a method of using the photoelectric conversion element manufactured as described above in a photochemical cell will be described. The structure of a photochemical cell using the photoelectric conversion element of the present invention is shown in FIG. 1 and will be described below with reference to FIG. The photoelectric conversion element formed by stacking the semiconductor film 2 containing the composite semiconductor of the present invention on the transparent conductive film 4 of the conductive support composed of the transparent substrate 1 and the transparent conductive film 4 serves as a cathode. Semiconductor film 2
Optionally, a photosensitizer is supported. On the semiconductor film 2 side of this photoelectric conversion element, a counter electrode 5 supported by a transparent substrate 6 serving as a positive electrode is opposed via the electrolyte layer 3.

The electrolyte layer 3 and the counter electrode 5 will be described in detail below. The electrolyte layer 3 is a layer having a function of supplementing electrons to the photosensitizer and the semiconductor. As a typical example, a liquid in which a redox couple is dissolved in an organic solvent, a so-called gel electrolyte in which a liquid in which a redox couple is dissolved in an organic solvent is impregnated in a polymer matrix, a molten salt containing a redox couple or an inorganic or organic Examples include solid electrolytes. In addition, organic polymers with hole transport capability, CuI and C
Even if a p-type semiconductor such as uNCS is used, the same operation as described above can be achieved.

As the redox couple, for example, a combination of iodine and iodide (for example, lithium iodide, tetrabutylammonium iodide, tetrapropylammonium iodide, etc.), a combination of bromine and bromide, a combination of alkyl viologen and a reduced form thereof, etc. Is mentioned. In addition, quinone / hydroquinone, iron (II) ion / iron (II
I) ion, copper (I) ion / copper (II) ion, etc. are also possible. Further, a supporting electrolyte may be added to the electrolyte solution for the purpose of increasing the electric conductivity of the electrolyte solution. Examples of the supporting electrolyte include calcium chloride, sodium sulfate, ammonium chloride and the like. Organic solvents that dissolve these include aprotic polar solvents (eg, acetonitrile, methoxyacetonitrile, methoxypropionitrile, ethylene carbonate, propylene carbonate, dimethylformamide, dimethyl sulfoxide, 1,3-dimethylimidazolinone, 3-methyl). Oxazolidinone) is preferred. Since the redox couple serves as an electron carrier, a certain concentration is required, and a desirable concentration is 0.01 mo.
It is 1 / l or more, more preferably 0.3 mol / l or more.

As the counter electrode 5, it is possible to use a noble metal material such as platinum, palladium, gold, or silver, or a metal material such as copper or aluminum from the viewpoint of conductivity. It is also possible to use carbon. Considering the stability and the catalytic effect at the time of contact with the electrolyte layer, platinum is preferable. In addition, considering the light transmittance, the above-mentioned transparent conductive material can be selected, such as ITO or FTO.
It is also possible to use a transparent conductive film such as.

The transparent substrate 6 supporting the counter electrode 5 can be made of the same material as the transparent substrate 1. In the present invention, when a metal material is used for the counter electrode,
A transparent conductive film 4 such as a cathode may be used between the transparent substrate and the transparent substrate if necessary. The photochemical cell is assembled by a known method. An electrolyte may be injected after previously fixing a cathode and an anode prepared in advance, or an electrolyte may be dropped on either of the electrodes and then the counter electrode may be stacked thereon to form a battery. At that time, a film-shaped or particle-shaped spacer may be interposed between both electrodes.

In the photochemical battery, in order to prevent the evaporation of components such as the electrolyte layer, the side surface of the battery cell is coated with a polymer such as paraffin, an epoxy resin, a polyacrylate resin, a silicone resin, a fluorine resin by a known method. It is preferable to seal with the adhesive. Further, when the transparent substrate 1 or 6 is a polymer film having a low melting point and a low softening point, it can be fused and sealed.

[0062]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method for producing a photoelectric conversion element and a photochemical cell of the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. RINT-2500 (manufactured by Rigaku Denki Co., Ltd.) was used to identify the composition of the core and shell of the composite semiconductor in this example.
The measurement conditions were Cu K _α ray for the radiation source, 2θ / θ for the scanning axis,
Step interval is 0.02 °, scan speed is 4.0
° / min, acceleration voltage 40kV, acceleration current 200m
The results obtained were determined by belonging to the JCPDS card. In addition, the slit used at the time of measurement,
The divergence slit was 1 °, the scattering slit was 1 °, the light receiving slit was 0.15 mm, and a graphite monochromator was attached in front of the detector.

The dye adsorption amount in this example was derived as follows. Using MPC2200 (manufactured by Shimadzu Corporation), the measurement conditions were a transmission mode at a wavelength of 300 nm to 800 nm, and the dye amount was converted from the absorbance of the dye. The performance of the photochemical battery cell in this example was measured as follows. The solar simulator (manufactured by Wacom Denso Co., Ltd.) irradiates the cell with pseudo sunlight of about 100 mW / cm ² , and the IV curve tracer (manufactured by Eiko Seiki Co., Ltd.) opened the voltage value (Voc). , Fill factor (FF) was determined. Cell measurement area is 1 cm ^2.
Is.

Further, the crystalline titanium oxide fine particles (P-25 manufactured by Nippon Aerosil Co., Ltd.) used in this example were RIN.
Cu K _α using T-2500 (manufactured by Rigaku Denki Co., Ltd.)
When powder X-ray diffraction measurement by X-ray was performed, a peak waveform of a highly crystalline mixture of anatase type and rutile type was shown, and the ratio was anatase: rutile = about 8: 2, which was the main peak of anatase type (101 The half-value width of the X-ray diffraction peak of the () plane was about 0.40 °. The thickness of the shell in this example is premised on that the amount of the metal element in the shell precursor material is changed to the identified shell material, and using its specific gravity, the specific gravity of the core semiconductor, and the average particle diameter of the core semiconductor, It was calculated.

[0065]

Example 1 (1) Preparation of Dispersion Liquid for Semiconductor Film Crystalline titanium oxide fine particles (P manufactured by Nippon Aerosil Co., Ltd.)
-25) 6 g, 120 g of water and 1.49 g of nitric acid were mixed and then heat-treated at 80 ° C. for about 8 hours. After cooling down,
All the water was distilled off with an evaporator to give a powder, which was well ground in a mortar. 1. As a n-type semiconductor, 1 g of crystalline titanium oxide fine particles obtained by the method described above, and 3.
68g and calcium oxalate as shell precursor-1
0.21 g of the hydrate was mixed well and dispersed using an ultrasonic homogenizer for about 10 minutes. After dispersion, 1 g of 1.7 mass% titanium peroxide aqueous solution (manufactured by Tanaka Transfer Co., Ltd.) and Trit
0.06 g of on-X100 (manufactured by Aldrich) was slowly added and stirred.

(2) Preparation of photoelectric conversion element (semiconductor electrode containing composite semiconductor) Fluorine-doped tin oxide (FTO: sheet resistance of about 8)
Use a wire bar (wire winding part 300m / m, core diameter 12.5m / m, winding diameter 1.0m / m) on the conductive surface side of transparent conductive glass coated with Ω / □) (1)
Was applied. After coating, it was air dried at room temperature for about 1 hour. The semiconductor film coated on this transparent conductive glass was placed in an electric furnace and sintered at a temperature of 500 ° C. for about 30 minutes. The film thickness after sintering was about 8 μm. When powder X-ray diffraction measurement of the obtained semiconductor film was carried out, crystalline titanium oxide (mixing of anatase type and rutile type) forming the core of the composite semiconductor and calcium carbonate forming the shell were assigned. The observed peak was observed. The thickness of the shell was calculated to be 1.1 nm. Next, an ethanol solution of a spectral sensitizing dye represented by a bis-tetrabutylammonium salt of cis-di (thiocyanato) -bis (2,2'-bipyridyl-4,4'-dicarboxylate) ruthenium (II) ( Refluxing in 3 × 10 ⁻⁴ mol / l) for about 45 minutes,
The above dye was adsorbed in the semiconductor film. After the reflux, the membrane surface was lightly washed with acetonitrile. The adsorption amount of the above dye is 5.
It was 5 × 10 ⁻⁸ mol / cm ² .

(3) Preparation of photochemical cell As a counter electrode, a platinum film having a thickness of about 0.1 μm was prepared on a slide glass by sputtering, and several drops of chloroplatinic acid aqueous solution were further dropped, followed by drying and sintering (385 ° C.). , 15 minutes) and platinum fine particles were vapor-deposited thereon to prepare a platinum electrode. Electrolyte solution (iodine 0.05 mol / l using methoxypropionitrile as a solvent, lithium iodide 0.1 mol / l
1, tert-butylpyridine 0.5 mol / l, dimethylpropyl imidazolium iodide 0.6 mo
1 / l solution) was prepared, an electrolytic solution was dropped on the prepared semiconductor electrode, and a counter electrode was overlaid thereon to prepare a photochemical cell.

(4) Measurement of cell performance Pseudo sunlight having an intensity of light of about 100 mW / cm ²
Cell performance was measured by irradiating the produced photochemical battery cell. Voc = 0.76V, F.V. F. Was 0.56.

[0069]

Example 2 A dispersion for a semiconductor film was prepared in the same manner as in Example 1 except that the amount of calcium oxalate monohydrate added was changed to 0.50 g, and the same procedure as in Example 1 was carried out. When a photoelectric conversion element (semiconductor electrode containing a composite semiconductor), a photochemical cell, and cell performance were measured, crystalline titanium oxide (anatase type, rutile) forming the core of the composite semiconductor in the semiconductor film was observed. And a peak attributed to the calcium carbonate forming the shell. The thickness of the shell was calculated to be 2.4 nm.
The amount of dye adsorbed was 2.3 × 10 ⁻⁸ mol / cm ² . The cell performance is Voc = 0.77V, F.S. F. =
It was 0.60.

[0070]

Example 3 A dispersion for a semiconductor film was prepared in the same manner as in Example 1 except that 0.50 g of magnesium oxalate dihydrate was used instead of calcium oxalate monohydrate. A photoelectric conversion element (composite semiconductor-containing semiconductor electrode) was prepared, a photochemical cell was prepared, and cell performance was measured in the same manner as in Example 1. Crystals forming a composite semiconductor core in the semiconductor film were obtained. Peaks attributed to soluble titanium oxide (mixture of anatase type and rutile type) and magnesium oxide forming a shell were observed. The thickness of the shell was calculated to be 0.60 nm. The amount of dye adsorbed was 6.1 × 10 ^-8 mol / cm ² . The cell performance is Voc = 0.79V, F.S. F. = 0.64.

[0071]

Example 4 Instead of calcium oxalate monohydrate, strontium oxalate monohydrate was changed to 0.13 g, and the amount of Triton-X100 added was 0.1.
A dispersion for a semiconductor film was prepared in the same manner as in Example 1 except that the amount was changed to 3 g, and a photoelectric conversion element (composite semiconductor-containing semiconductor electrode) was prepared and a photochemical cell was prepared in the same manner as in Example 1. When cell performance was measured, the peaks attributable to crystalline titanium oxide (mixture of anatase type and rutile type) forming the core of the composite semiconductor in the semiconductor film and strontium carbonate forming the shell were observed. Was observed. Further, the thickness of the shell was calculated to be 0.43 nm. Further, the dye adsorption amount is 6.6 × 10 ⁻⁸ mol / cm ²
Met. The cell performance is Voc = 0.79V, F.S. F.
= 0.60.

[0072]

Example 5 Instead of calcium oxalate monohydrate, strontium oxalate monohydrate was changed to 0.21 g, and the amount of Triton-X100 added was 0.0.
A dispersion for a semiconductor film was prepared in the same manner as in Example 1 except that the amount was changed to 6 g, and a photoelectric conversion element (composite semiconductor-containing semiconductor electrode) was prepared in the same manner as in Example 1, a photochemical cell was prepared, When cell performance was measured, the peaks attributable to crystalline titanium oxide (mixture of anatase type and rutile type) forming the core of the composite semiconductor in the semiconductor film and strontium carbonate forming the shell were observed. Was observed. Further, the thickness of the shell was calculated to be 0.67 nm. Further, the dye adsorption amount is 6.7 × 10 ⁻⁸ mol / cm ²
Met. The cell performance is Voc = 0.80V, F.S. F.
= 0.64.

[0073]

Example 6 Instead of calcium oxalate monohydrate, magnesium nitrate hexahydrate 0.75 g was used.
Furthermore, except that the addition amount of Triton-X100 was changed to 0.26 g, a dispersion liquid for a semiconductor film was prepared in the same manner as in Example 1, and the photoelectric conversion element (composite semiconductor-containing semiconductor was prepared in the same manner as in Example 1). Electrode) production, photochemical cell production, and cell performance measurement showed that crystalline titanium oxide (a mixture of anatase type and rutile type) forming the core of the composite semiconductor in the semiconductor film formed a shell. A peak attributed to magnesium oxide was observed. Moreover, the thickness of the shell was calculated to be 0.52 nm. The amount of dye adsorbed was 8.4 × 10 ^-8 mol / cm ² . The cell performance is Voc = 0.85V, F.O. F. = 0.
It was 73.

[0074]

[Example 7] Instead of calcium oxalate monohydrate, calcium nitrate tetrahydrate 0.30 g was changed, and the addition amount of Triton-X100 was changed to 0.26 g. A dispersion for a semiconductor film was prepared in the same manner as in Example 1, and a photoelectric conversion element (composite semiconductor-containing semiconductor electrode) was prepared, a photochemical cell was prepared in the same manner as in Example 1.
When the cell performance was measured, it was attributed to crystalline titanium oxide (a mixture of anatase type and rutile type) forming the core of the composite semiconductor in the semiconductor film and calcium titanate forming the shell. A peak was observed. Also,
The shell thickness was calculated to be 0.65 nm. The amount of dye adsorbed was 6.5 × 10 ^-8 mol / cm ² . The cell performance is Voc = 0.81V, F.S. F. = 0.68.

[0075]

Example 8 Instead of calcium oxalate monohydrate, strontium nitrate was changed to 0.21 g, and T
A dispersion for a semiconductor film was prepared in the same manner as in Example 1 except that the addition amount of the Riton-X100 was changed to 0.26 g, and the photoelectric conversion element (composite semiconductor-containing semiconductor electrode) was prepared in the same manner as in Example 1. ), A photochemical cell, and cell performance were measured, and it was found that crystalline titanium oxide (a mixture of anatase type and rutile type) forming the core of the composite semiconductor in the semiconductor film formed a shell. A peak attributed to calcium titanate was observed. The thickness of the shell was calculated to be 0.59 nm. The amount of dye adsorbed was 5.9 × 10 ⁻⁸ mol / cm ² . The cell performance is Voc = 0.80V, F.S. F. = 0.65.

[0076]

[Example 9] Instead of calcium oxalate monohydrate, the amount of lithium oxalate was changed to 0.13 g, and Tr
A dispersion liquid for a semiconductor film was prepared in the same manner as in Example 1 except that the addition amount of iton-X100 was changed to 0.13 g, and the photoelectric conversion element (composite semiconductor-containing semiconductor electrode) was prepared in the same manner as in Example 1. ), A photochemical cell, and cell performance were measured, and it was found that crystalline titanium oxide (a mixture of anatase type and rutile type) forming the core of the composite semiconductor in the semiconductor film formed a shell. A peak attributed to the existing lithium carbonate was observed. Further, the thickness of the shell was calculated to be 0.70 nm. The amount of dye adsorbed was 3.5 × 10 ⁻⁸ mol / cm ² . Cell performance is
Voc = 0.79V, F.V. F. = 0.66.

[0077]

Comparative Example 1 A dispersion liquid for a semiconductor film was prepared in the same manner as in Example 1 without adding calcium oxalate monohydrate, and the photoelectric conversion element was prepared in the same manner as in Example 1. When (composite semiconductor-containing semiconductor electrode) was manufactured, a photochemical battery was manufactured, and cell performance was measured, only crystalline titanium oxide (mixture of anatase type and rutile type) was observed in powder X-ray diffraction measurement in the semiconductor film. In addition, the dye adsorption amount is 4.7 x
It was 10 ^-8 mol / cm ² . Cell performance is Voc =
0.67V, F.I. F. Was 0.46.

[0078]

[Table 1]

Examples and comparative examples of the present invention are summarized in the table. The mass ratio (shell / core) of the shell part is the charged mass ratio of the shell / core when the precursor of the shell material is completely changed to the composition of the shell material.

[0080]

As described in detail above, according to the present invention,
A semiconductor film containing a composite semiconductor characterized in that a crystalline n-type semiconductor is used as a core, and the surface of the core is covered with a shell made of any one of metal carbonate, metal oxide and metal titanate. By using the photoelectric conversion element in a photochemical cell, it is possible to provide a cell capable of exhibiting a high open circuit voltage (Voc) and a high fill factor (FF).

[Brief description of drawings]

FIG. 1 shows a schematic view of a cross section of a photoelectric conversion element and a photochemical cell according to an example of the present invention.

[Explanation of symbols]

1 Transparent substrate 2 Semiconductor film 3 Electrolyte layer 4 Transparent conductive film 5 Counter electrode 6 Transparent substrate

Claims (6)

[Claims] 1. A metal carbonate on the surface of a crystalline n-type semiconductor,
A composite semiconductor, which is coated with at least one of a metal oxide and a metal titanate. 2. The crystalline n-type semiconductor according to claim 1,
A composite semiconductor, which is crystalline titanium oxide. 3. The composite semiconductor according to claim 1, wherein the metal of the metal carbonate, the metal oxide and the metal titanate is an alkaline earth metal or an alkali metal. 4. A photoelectric conversion element comprising a semiconductor film containing the composite semiconductor according to claim 1 laminated on a conductive support. 5. A photoelectric conversion element, wherein the semiconductor film according to claim 4 further contains a photosensitizer. 6. A photochemical cell, wherein the photoelectric conversion element according to claim 4 and the counter electrode face each other via an electrolyte layer.