JP4931402B2 - Photoelectric conversion element - Google Patents

Description

  The present invention relates to a photoelectric conversion element.

The dye-sensitized solar cell element announced by Gretzell et al. In 1991 is a wet solar cell using a titanium oxide porous thin film spectrally sensitized by a ruthenium complex as a working electrode, and can obtain performance equivalent to that of a silicon solar cell. Has been reported (see Non-Patent Document 1). Since this method can use an inexpensive oxide semiconductor such as titania without purifying it with high purity, it can provide an inexpensive dye-sensitized solar cell element, and since the absorption of the dye is broad, it is visible. It has the advantage of being able to convert light in almost all wavelength regions of light into electricity, and has attracted attention.
The titania porous thin film is generally obtained by applying a high-viscosity dispersion containing titania fine particles on an electrode and baking it at a high temperature. In general, a working electrode is produced by adsorbing a photosensitizer having a carboxyl group to a semiconductor layer composed of the titania porous thin film. The photosensitizer absorbs light and generates electrons and holes. Electrons flow into the semiconductor layer and become an electric current. However, in the conventional method, the adsorption amount of the photosensitizer per unit area of the semiconductor layer is not sufficient. For this reason, there existed a subject that an electric current value fell.
On the other hand, when the adsorption amount of the photosensitizer is increased, a bond between the photosensitizers is formed, and the photosensitizer layer is multi-layered, thereby inhibiting the flow of excited electrons to the semiconductor layer. Will be. For this reason, when the amount of adsorption is increased, a tendency that the current value decreases from the point of a certain amount of adsorption is observed.
B. O'Regan, M. Gratzel, “Nature” (UK), 1991, 353, p. 737

  Thus, in a photoelectric conversion element, in order to obtain a large current value, it has been required to adsorb more photosensitizer in an optimal adsorption state.

  The present invention has been made in view of such a situation, and particularly preferably a photosensitizer by setting the proportion of the ammonium salt portion of all carboxyl groups in the photosensitizer within a specific range. As a result of using two or more kinds of mixtures having different proportions of ammonium chloride, when the photosensitizer layer is multi-layered, it flows to the semiconductor layer due to the difference in energy level. The increase and the reduction of current loss can be achieved, and the above-mentioned problems have been solved.

  That is, the present invention relates to a photoelectric conversion element comprising at least a conductive substrate, a semiconductor layer adsorbing a photosensitizer, a charge transport layer and a counter electrode, wherein the photosensitizer is contained in a photosensitizer molecule. The present invention relates to a photoelectric conversion element characterized in that 10% or more and 40% or less of all carboxyl groups are made of a compound which is ammonium chloride.

（式（１）中、Ｘは水素またはアンモニウムカチオンを表し、各Ｘは互いに同一でも異なっていてもよい。） The present invention also relates to the photoelectric change element as described above, wherein the photosensitizer is a compound represented by the formula (1) and is a mixture of two or more kinds having different numbers of ammonium cations. .

(In formula (1), X represents hydrogen or an ammonium cation, and each X may be the same as or different from each other.)

In the present invention, the photosensitizer adsorbed on the semiconductor layer is in the range of 2.0 × 10 ⁻⁴ mol / cm ^{3 to} 3.0 × 10 ⁻⁴ mol / cm ³ per unit volume of the semiconductor layer, and a photoelectric conversion element of the described, which is a 1.0 range of ^{× 10 -8 mol / cm 2 ~1.0} × 10 -6 mol / cm 2 per semiconductor unit area.

  The present invention also relates to the above-described photoelectric conversion element, wherein the semiconductor layer is formed of a metal oxide.

  Furthermore, this invention relates to the photovoltaic cell using the said photoelectric conversion element.

The present invention is described in detail below.
The photoelectric conversion element of the present invention includes at least a conductive substrate, a semiconductor layer adsorbing a photosensitizer, a charge transport layer, and a counter electrode.
The conductive substrate usually has a conductive film on the substrate. The substrate is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose. For example, metal, colorless or colored glass, meshed glass, glass block, etc. are used. Colorless or colored resin may be used. Examples of such resins include polyesters such as polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, and polymethylpentene. In addition, the board | substrate in this invention has a smooth surface at normal temperature, The surface may be a plane or a curved surface, and may deform | transform by stress.

The material of the conductive film that functions as an electrode is not particularly limited, and examples thereof include a metal such as gold, silver, chromium, copper, tungsten, and titanium, a metal thin film, and a conductive film made of a metal oxide. Examples of the metal oxide include Indium Tin Oxide (ITO (In ₂ O ₃ : Sn)) obtained by doping a metal oxide such as tin and zinc with a small amount of other metal elements, Fluorine doped Tin Oxide (FTO (SnO ₂ )). : F)), Aluminum doped Zinc Oxide (AZO (ZnO: Al)) and the like are preferably used.
The film thickness of the conductive film is usually 100 to 10,000 nm, preferably 500 to 3000 nm. The surface resistance (resistivity) is appropriately selected, but is usually 0.5 to 500 Ω / sq, preferably 1 to 50 Ω / sq.

  The method for forming the conductive film is not particularly limited, and a known method can be appropriately employed depending on the type of metal or metal oxide used. Usually, a vacuum deposition method, an ion plating method, a CVD method, a sputtering method, or the like is used. In either case, it is desirable that the substrate temperature be formed within a range of 20 to 700 ° C.

The counter electrode (counter electrode) in the photoelectric conversion element of the present invention may have a single layer structure made of a conductive material, or may be composed of a conductive layer and a substrate. The substrate is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose. For example, metal, colorless or colored glass, meshed glass, glass block, etc. are used. Resin may be used. Examples of such resins include polyesters such as polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, and polymethylpentene. Alternatively, the counter electrode may be formed by applying, plating, or vapor-depositing (PVD, CVD) a conductive material directly on the charge transport layer.
As the conductive material, metals such as platinum, gold, nickel, titanium, aluminum, copper, silver, and tungsten, and materials having a small specific resistance such as carbon materials and conductive organic substances are used.
A metal lead may be used for the purpose of reducing the resistance of the counter electrode. The metal lead is preferably made of a metal such as platinum, gold, nickel, titanium, aluminum, copper, silver or tungsten, and particularly preferably made of aluminum or silver.

The semiconductor layer is composed of a metal oxide. As the metal oxide, TiO ₂ , SnO ₂ , ZnO ₂ , WO ₃ , NiO, TiSrO ₃ or the like is used, and preferably formed from a titanium oxide thin film.
The titanium oxide thin film may be formed of titanium oxide fine particles and nanotubes. Such titanium oxide fine particles preferably have a particle size of 0.5 to 100 nm, more preferably 2 to 30 nm. Specific examples include those prepared from titanium ore by a liquid phase method and those synthesized by a vapor phase method, a sol-gel method, and a liquid phase growth method. Here, the vapor phase method is a method for producing titania by calcining hydrous titanium oxide obtained by heating and hydrolyzing titanium ore with a strong acid such as sulfuric acid at 800 ° C. to 850 ° C. The liquid phase method is a method for producing titania by bringing oxygen and hydrogen into contact with titanium chloride. In the sol-gel method, titanium alkoxide is hydrolyzed in an alcohol aqueous solution to form a sol, and further, a hydrolysis catalyst is added to the sol, left to gel, and the gelled product is baked to titania. It is a method of manufacturing. The liquid phase growth method is a method for obtaining titania by hydrolysis of titanium fluoride, ammonium tetrafluorotitanate, titanyl sulfate or the like.

The nanotube can be obtained by anodizing titanium metal or an alloy containing titanium as a main component to obtain tube-shaped titanium oxide having a longitudinal length of 1 μm or more, preferably 2 to 100 μm. The outer diameter of the tube-shaped titanium oxide is usually 5 to 50 nm, preferably 10 to 30 nm, and the wall thickness is usually 2 to 20 nm, preferably 3 to 10 nm. The specific surface area of the nanotube is 50 m ² / g or more, preferably 70 m ² / g or more.
The nanotube-shaped titanium oxide obtained as described above can be crystallized into an arbitrary crystal type by performing post-treatment such as heat treatment, pressure treatment, electron beam irradiation, and light irradiation, if necessary. . For example, in the case of heat treatment, crystallization is performed by performing treatment at a temperature of 100 ° C. to 1200 ° C., preferably 150 ° C. to 800 ° C., for 10 to 500 minutes, preferably 10 to 300 minutes.

  The formed semiconductor layer is preferably subjected to heat treatment for the purpose of enhancing electronic contact between titanium oxides and improving adhesion with the conductive substrate. As heat processing temperature, 100 to 600 degreeC is preferable, More preferably, it is 250 to 550 degreeC. Moreover, heat processing time can be normally performed in 10 minutes-10 hours.

In the photoelectric conversion element of the present invention, a photosensitizer is adsorbed on the semiconductor layer for the purpose of improving (sensitizing) the light absorption efficiency of the semiconductor layer. The photosensitizer is not particularly limited as long as it is a dye that has absorption characteristics in the visible region and near-infrared region and improves (sensitizes) the light absorption efficiency of the semiconductor layer, but imparts adsorptivity to the semiconductor layer. Therefore, those having a carboxyl group in the dye molecule are used.
The photosensitizer used in the present invention is a compound in which a range of 10% to 40% of all carboxyl groups in the molecule is ammonium chloride. If the proportion of the ammonium salt is outside this range, it is not preferable because the flow of excited electrons to the semiconductor layer is inhibited when the adsorption amount of the photosensitizer is increased. The ratio of ammonium chloride carboxyl group to the total carboxyl group is preferably 10% or more, more preferably 20% or more, preferably 40% or less, more preferably 35% or less.

The dye used in the present invention is preferably a metal complex dye, an organic dye, a natural dye, or a semiconductor.
As the metal complex dye, a complex of ruthenium, osmium, iron, cobalt, zinc, mercury (for example, mellicle chrome), metal phthalocyanine, chlorophyll, or the like can be used. Examples of organic dyes include, but are not limited to, cyanine dyes, hemicyanine dyes, merocyanine dyes, xanthene dyes, triphenylmethane dyes, and metal-free phthalocyanine dyes. Usually, there are often about 1 to 4 carboxyl groups as adsorption sites. However, protons in the photosensitizer shift the semiconductor conduction band to the positive side. Since the shift of the conduction band affects the voltage drop of the solar cell, it is necessary to reduce the number of protons. Usually, a method of substituting protons with ammonium salts is used.

As the metal complex dye, a ruthenium complex is preferably used, and a complex having a bipyridyl ring represented by the formula (1) as a ligand is particularly preferably used.

  In formula (1), X represents hydrogen or an ammonium cation. The ammonium cation represents ammonium having an alkyl group or an aryl group, and these groups may be different from each other or the same. Moreover, when it has several ammonium cations, it is preferable that each is the same.

As an alkyl group, a C1-C24 alkyl group is mentioned. Specifically, methyl, ethyl, propyl, butyl, pentyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, Examples include heptadecyl group, octadecyl group, nonadecyl group, icosyl group, heicosyl group, docosyl group, tricosyl group, tetracosyl group and the like.
Examples of the aryl group include an aryl group having 6 to 10 carbon atoms and an alkylaryl group having 7 to 18 carbon atoms. Specifically, phenyl group, naphthyl group, tolyl group, xylyl group, ethylphenyl group, propylphenyl group, butylphenyl group, pentylphenyl group, hexylphenyl group, heptylphenyl group, octylphenyl group, nonylphenyl group, decyl A phenyl group, an undecylphenyl group, a dodecylphenyl group, etc. are mentioned.

  Specific examples of the ammonium cation include tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, methyltriethylammonium, tetraphenylammonium, methyltriphenylammonium and the like.

In the present invention, as the photosensitizer, a compound composed of two or more kinds of compounds represented by the formula (1) and having different numbers when the group represented by X is an ammonium cation is particularly preferably used. It is done. In this case, it is necessary that the ratio of the ammonium salt as a whole mixture is in the range of 10% to 40% with respect to the total carboxyl groups.
Specifically, when all of the four groups represented by X of the compound represented by the formula (1) are ammonium cations, the proportion of the ammonium salified sites is 100%, and the three groups are ammonium cations. The ratio of ammonium salified sites is 75%, and when two groups are ammonium cations, the proportion of ammonium salified sites is 50% and only one group is an ammonium cation. The ratio of the site that is ammonium chloride is 25%, and when all four Xs are hydrogen, it becomes 0%.
In the present invention, by appropriately mixing and adjusting two or more of the above five kinds of compounds having different numbers of ammonium-saturated sites, the ratio of ammonium-stained sites to the total carboxyl groups as a whole mixture can be obtained. Adjust within the range of 10% to 40%. For example, in the formula (1), when a compound in which one of X is ammonium salified and a compound in which two of X are ammonium salified are mixed at a molar ratio of 1: 1, the mixture as a whole in all carboxyl groups. The proportion of the ammonium-chlorinated sites is 37.5%.
In addition, the kind and mixing ratio of two or more kinds of compounds are not particularly limited as long as the ratio of the ammonium salified site to the total carboxyl groups in the whole mixture falls within the range of 10% to 40%.

  As a method for adsorbing the photosensitizer on the semiconductor layer, for example, a solution in which a dye is dissolved in a solvent is applied by spray coating or spin coating on the semiconductor layer and then dried. . In this case, the substrate may be heated to an appropriate temperature. Alternatively, a method in which a semiconductor layer is immersed in a solution and adsorbed can be used. The immersion time is not particularly limited as long as the dye is sufficiently adsorbed, but is preferably 10 minutes to 30 hours, more preferably 1 to 20 hours. Moreover, you may heat a solvent and a board | substrate when immersing as needed. The concentration of the dye in the case of the solution is about 0.01 to 100 mmol / L, preferably about 0.1 to 50 mmol / L.

  As the solvent, alcohols, ethers, nitriles, esters, hydrocarbons and the like can be used. When the number of adsorbed dye ammonium salts is arbitrarily adjusted, it can be achieved by changing the solvent each time. For example, if you want to reduce the proportion of ammonium salt, you can use a single solvent of alcohols such as ethanol, and if you want to increase the proportion of ammonium salt, alcohols and other ethers, nitriles, esters, etc. And a mixed solvent can be used.

  In order to reduce the interaction such as aggregation between the dyes, a colorless compound having properties as a surfactant may be added to the dye adsorption liquid and co-adsorbed to the semiconductor layer. Examples of such colorless compounds include steroid compounds such as cholic acid having a carboxyl group or sulfo group, deoxycholic acid, chenodeoxycholic acid, taurodeoxycholic acid, sulfonates, and the like.

  It is preferable to remove the unadsorbed dye by washing immediately after the adsorption step. Washing is preferably performed using acetonitrile, an alcohol solvent or the like in a wet washing tank.

The adsorption amount of the photosensitizer is calculated from the light absorption amount of the alkaline solution after desorbing the photosensitizer from the semiconductor layer with a strong alkaline solution. Further, the proportion of ammonium chloride in all carboxyl groups is calculated from the peak intensity of the NMR spectrum of the photosensitizer after desorption.
When a mixture of the photosensitizers is used, it is usually adsorbed competitively with a small amount and a large amount of ammonium. The adsorption rate of the thing with little ammonium is high, and the thing with much ammonium gradually adsorb | sucks. By utilizing this difference in the adsorption rate, more photosensitizer can be adsorbed, and 2.0 × 10 ⁻⁴ mol / cm ^{3 to} 3.0 × 10 ⁻⁴ mol / with respect to the semiconductor layer. Adsorption can be in the amount of cm ³ .
Further, the adsorption amount to the semiconductor surface, can be adsorbed in the range of ^{1.0 × 10 -8 mol / cm 2} ~1.0 × 10 -6 mol / cm 2.

  After adsorbing the dye, a semiconductor using an amine, a quaternary ammonium salt, a ureido compound having at least one ureido group, a silyl compound having at least one silyl group, an alkali metal salt, an alkaline earth metal salt, etc. The surface of the layer may be treated. Examples of preferred amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like. Examples of preferred quaternary ammonium salts include tetrabutylammonium iodide, tetrahexylammonium iodide and the like. These may be used by dissolving in an organic solvent, or may be used as they are in the case of a liquid.

  The charge transport layer contains a charge transport material having a function of replenishing electrons to the oxidant of the dye. The charge transport material used in the present invention may be a charge transport material related to ions or a charge transport material related to carrier movement in a solid. Examples of the charge transport material in which ions are involved include a solution in which a redox counter ion is dissolved, a gel electrolyte composition in which a polymer matrix gel is impregnated with a solution of a redox pair, a solid electrolyte composition, and the like. Examples of the charge transport material involved in the electron transport material include an electron transport material and a hole transport material. A plurality of these charge transport materials may be used in combination.

The electrolyte solution as a charge transport material involving ions is preferably composed of an electrolyte, a solvent, and an additive. Examples of the electrolyte used in the electrolytic solution, iodine and iodide (LiI, NaI, KI, CsI, metal iodide such as CaI _2, tetraalkylammonium iodide, pyridinium iodide, quaternary ammonium such as imidazolium iodide A combination of bromine and bromide (metal bromide such as LiBr, NaBr, KBr, CsBr, CaBr, CaBr ₂ , quaternary ammonium compound bromide such as tetraalkylammonium bromide, pyridinium bromide, etc.) Examples thereof include metal complexes such as Russianate-ferricyanate and ferrocene-ferricinium ions, sulfur compounds such as sodium polysulfide and alkylthiol-alkyldisulfides, viologen dyes, and hydroquinone-quinone. Among them, an electrolyte in which I ₂ and a quaternary ammonium compound iodine salt such as LiI or pyridinium iodide, imidazolium iodide or the like are combined is preferable. The electrolyte may be used as a mixture.

  Any solvent can be used as long as it is generally used in electrochemical cells and batteries. Specifically, acetic anhydride, methanol, ethanol, tetrahydrofuran, propylene carbonate, nitromethane, acetonitrile, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide, ethylene carbonate, dimethoxyethane, γ-butyrolactone, γ-valerolactone, sulfolane, dimethoxy Ethane, propiononitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, dimethylacetamide, methylpyrrolidinone, dimethyl sulfoxide, dioxolane, sulfolane, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, ethyldimethyl phosphate, tributyl phosphate, phosphorus Tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, phosphoric acid Tridecyl, tris phosphate (trifluoromethyl), tris phosphate (pentafluoroethyl), triphenyl polyethylene glycol phosphate, polyethylene glycol, and the like can be used. In particular, propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethoxyethane, acetonitrile, γ-butyrolactone, sulfolane, dioxolane, dimethylformamide, dimethoxyethane, tetrahydrofuran, adiponitrile, methoxyacetonitrile, methoxypropionitrile, dimethylacetamide, methylpyrrolidinone, dimethylsulfoxide , Dioxolane, sulfolane, trimethyl phosphate and triethyl phosphate are preferred. Also, room temperature molten salts can be used. Here, the room temperature molten salt is a salt composed of an ion pair that is melted at room temperature (that is, in a liquid state) and usually has a melting point of 20 ° C. or lower and is a liquid at a temperature exceeding 20 ° C. Is a salt. The solvent may be used alone or in combination of two or more.

  Moreover, it is preferable to add basic compounds, such as 4-t-butyl pyridine, 2-picoline, and 2, 6-lutidine, to the above-mentioned molten salt electrolyte composition and electrolyte solution. A preferable concentration range when adding the basic compound to the electrolytic solution is 0.05 to 2 mol / L. When added to the molten salt electrolyte composition, the basic compound preferably has an ionic group. The blending ratio of the basic compound with respect to the entire molten salt electrolyte composition is preferably 1 to 40% by mass, more preferably 5 to 30% by mass.

The material that can be used as the polymer matrix is not particularly limited as long as the polymer matrix alone, or the solid state or gel state is formed by adding a plasticizer, adding a supporting electrolyte, or adding a plasticizer and a supporting electrolyte. Generally used so-called polymer compounds can be used.
Examples of the polymer compound exhibiting characteristics as the polymer matrix include hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, ethylene, propylene, acrylonitrile, vinylidene chloride, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, methyl Examples thereof include polymer compounds obtained by polymerizing or copolymerizing monomers such as acrylate, ethyl acrylate, methyl methacrylate, styrene, and vinylidene fluoride. These polymer compounds may be used alone or in combination. Among these, a polyvinylidene fluoride polymer compound is particularly preferable.

  Further, instead of the ion conductive electrolyte, an organic solid hole transport material, an inorganic solid hole transport material, or a material in which both are combined can be used.

Examples of organic hole transport materials that can be preferably used include triphenylene derivatives, oligothiophene compounds, polypyrrole, polyacetylene and / or derivatives thereof, poly (p-phenylene) and / or derivatives thereof, poly (p-phenylene vinylene) and Examples thereof include conductive polymers such as / or derivatives thereof, polythienylene vinylene and / or derivatives thereof, polythiophene and / or derivatives thereof, polyaniline and / or derivatives thereof, polytoluidine and / or derivatives thereof. In order to control the dopant level, a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate may be added to the hole transport material. In addition, a salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added in order to perform potential control (space charge layer compensation) on the surface of the metal oxide semiconductor.

A p-type inorganic compound semiconductor can be used as the inorganic hole transport material, and the band gap is preferably 2 eV or more, more preferably 2.5 eV or more. Further, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye adsorption electrode in order to reduce the holes of the dye. Although the preferable range of the ionization potential of the p-type inorganic compound semiconductor varies depending on the dye used, it is preferably 4.5 to 5.5 eV, more preferably 4.7 to 5.3 eV. Preferred p-type inorganic compound semiconductor is a compound semiconductor containing monovalent copper, _{examples, CuI, CuSCN, CuInSe 2,} Cu (In, Ga) Se 2, CuGaSe 2, Cu 2 O, CuS, CuGaS 2 CuInS ₂ , CuAlSe _{2 and the} like. Among these, CuI and CuSCN are preferable, and CuI is most preferable. Examples of other p-type inorganic compound semiconductors include GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , Cr ₂ O _{3 and the} like.

  The charge transport layer can be formed by one of two methods. The first method is a method in which a semiconductor layer and a counter electrode are bonded together, and a liquid charge transport layer is sandwiched between the gaps. The second method is a method in which a charge transport layer is provided directly on the semiconductor layer, and a counter electrode is provided thereafter.

In the case of the former method, when sandwiching the charge transport layer, a normal pressure process using capillary action by dipping or the like, or a vacuum process in which the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure can be used. .
When a wet charge transport layer is used in the latter method, a counter electrode is usually applied in an undried state to prevent liquid leakage at the edge. Moreover, when using a gel electrolyte composition, you may solidify by methods, such as superposition | polymerization, after apply | coating this with a wet method. Solidification may be performed before or after applying the counter electrode.

  When a solid electrolyte composition or a solid hole transport material is used, a charge transport layer can be formed by a dry film forming process such as a vacuum deposition method or a CVD method, and then a counter electrode can be provided. The organic hole transport material can be introduced into the electrode by a vacuum deposition method, a casting method, a coating method, a spin coating method, a dipping method, an electrolytic polymerization method, a photoelectrolytic polymerization method, or the like. The inorganic solid compound can be introduced into the electrode by a casting method, a coating method, a spin coating method, a dipping method, an electrolytic deposition method, an electroless plating method, or the like.

  As described above, as a photosensitizer adsorbed on the semiconductor layer, a compound in which 10% or more and 40% or less of all carboxyl groups in the photosensitizer molecule are ammonium chloride is used in a suitable state. The amount of adsorption can be increased, and the efficiency of the dye-sensitized solar cell can be increased.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
<< Production of semiconductor layer (titania electrode) >>
Using titania paste (Ti-Naoxide T manufactured by SOLARONIX), it was applied onto F-SnO ₂ by the doctor blade method and dried. The obtained thin film was baked at 450 ° C. for 1 hour to obtain an electrode. The film thickness was 11 μm.
<< Evaluation of photoelectric conversion characteristics >>
The obtained semiconductor layer was mixed with ruthenium dye (Rutenium 535-bisTBA: manufactured by SOLARONIX, the ratio of ammonium salt in all carboxyl groups was adjusted to 40%) / ethanol solution (1.0 × 10 ⁻³ mol / L) 3 Dipping for a period of time formed a dye layer. The adsorption amount of the dye layer was 2.3 × 10 ⁻⁴ mol / cm ³ and 2.5 × 10 ⁻⁷ mol / cm ² , and the proportion of ammonium salt in all carboxyl groups was 28%.
The obtained substrate and the Pt surface of the glass with the Pt thin film were put together, 0.5 mol / L dimethylpropylimidazolium iodide, 0.05 mol / L iodine, 0.5 mol / L 4-t-butylpyridine. An acetonitrile solution containing 0.1 mol / L lithium iodide was impregnated by capillary action, and the periphery was sealed with an epoxy adhesive. A lead wire was connected to the conductive layer portion of the transparent conductive substrate and the counter electrode.
When the cell thus obtained was irradiated with pseudo-sunlight (1 kW / m ² ) and the current-voltage characteristics were measured, good photoelectric conversion characteristics (conversion efficiency 7.4%) were obtained.

[Example 2]
<< Evaluation of photoelectric conversion characteristics >>
The obtained semiconductor layer was mixed with ruthenium dye (Rutenium 535-bisTBA: manufactured by SOLARONIX, the ratio of ammonium salt in all carboxyl groups was adjusted to 38%) / ethanol solution (1.0 × 10 ⁻³ mol / L) to 12%. Dipping for a period of time formed a dye layer. The adsorption amount of the dye layer was 2.6 × 10 ⁻⁴ mol / cm ³ and 2.8 × 10 ⁻⁷ mol / cm ² , and the proportion of ammonium salt in all carboxyl groups was 23%.
The obtained substrate and the Pt surface of the glass with the Pt thin film were put together, 0.5 mol / L dimethylpropylimidazolium iodide, 0.05 mol / L iodine, 0.5 mol / L 4-t-butylpyridine. An acetonitrile solution containing 0.1 mol / L lithium iodide was impregnated by capillary action, and the periphery was sealed with an epoxy adhesive. A lead wire was connected to the conductive layer portion of the transparent conductive substrate and the counter electrode.
When the cell thus obtained was irradiated with pseudo-sunlight (1 kW / m ² ) and the current-voltage characteristics were measured, good photoelectric conversion characteristics (conversion efficiency 7.0%) were obtained.

[Example 3]
<< Evaluation of photoelectric conversion characteristics >>
The obtained semiconductor layer was mixed with ruthenium dye (Rutenium 535-bisTBA: manufactured by SOLARONIX, the ratio of ammonium salt in all carboxyl groups was adjusted to 58%) / ethanol solution (1.0 × 10 ⁻³ mol / L) to 12%. Dipping for a period of time formed a dye layer. The adsorption amount of the dye layer was 2.2 × 10 ⁻⁴ mol / cm ³ and 2.4 × 10 ⁻⁷ mol / cm ² , and the proportion of ammonium salt in the carboxyl group was 27%.
The obtained substrate and the Pt surface of the glass with the Pt thin film were put together, 0.5 mol / L dimethylpropylimidazolium iodide, 0.05 mol / L iodine, 0.5 mol / L 4-t-butylpyridine. An acetonitrile solution containing 0.1 mol / L lithium iodide was impregnated by capillary action, and the periphery was sealed with an epoxy adhesive. A lead wire was connected to the conductive layer portion of the transparent conductive substrate and the counter electrode.
When the cell thus obtained was irradiated with pseudo-sunlight (1 kW / m ² ) and the current-voltage characteristics were measured, good photoelectric conversion characteristics (conversion efficiency 7.0%) were obtained.

[Comparative Example 1]
<< Evaluation of photoelectric conversion characteristics >>
The obtained semiconductor layer was mixed with ruthenium dye (Rutenium 535-bisTBA: manufactured by SOLARONIX, the ratio of ammonium salt in all carboxyl groups was adjusted to 94%) / ethanol solution (1.0 × 10 ⁻³ mol / L) in 12%. Dipping for a period of time formed a dye layer. The adsorption amount of the dye layer was 1.7 × 10 ⁻⁴ mol / cm ³ and 1.0 × 10 ⁻⁷ mol / cm ² , and the proportion of ammonium salt in all carboxyl groups was 42%.
The obtained substrate and the Pt surface of the glass with the Pt thin film were put together, 0.5 mol / L dimethylpropylimidazolium iodide, 0.05 mol / L iodine, 0.5 mol / L 4-t-butylpyridine. An acetonitrile solution containing 0.1 mol / L lithium iodide was impregnated by capillary action, and the periphery was sealed with an epoxy adhesive. A lead wire was connected to the conductive layer portion of the transparent conductive substrate and the counter electrode.
When the cell thus obtained was irradiated with pseudo-sunlight (1 kW / m ² ) and the current-voltage characteristics were measured, photoelectric conversion characteristics (conversion efficiency 6.2%) were obtained.

[Comparative Example 2]
<< Evaluation of photoelectric conversion characteristics >>
Ruthenium dye (Rutenium 535-bisTBA: manufactured by SOLARONIX, adjusting the ratio of ammonium salt in all carboxyl groups to 58%) / acetonitrile / butanol solution (0.5 × 10 ⁻³ mol / L) For 12 hours to form a dye layer. The adsorption amount of the dye layer was 1.7 × 10 ⁻⁴ mol / cm ³ and 1.9 × 10 ⁻⁷ mol / cm ² , and the proportion of ammonium salt in all carboxyl groups was 45%.
The obtained substrate and the Pt surface of the glass with the Pt thin film were put together, 0.5 mol / L dimethylpropylimidazolium iodide, 0.05 mol / L iodine, 0.5 mol / L 4-t-butylpyridine. An acetonitrile solution containing 0.1 mol / L lithium iodide was impregnated by capillary action, and the periphery was sealed with an epoxy adhesive. A lead wire was connected to the conductive layer portion of the transparent conductive substrate and the counter electrode.
The cell thus obtained was irradiated with pseudo-sunlight (1 kW / m ² ) and the current-voltage characteristics were measured, and photoelectric conversion characteristics (conversion efficiency 5.2%) were obtained.

Claims (4)

In a photoelectric conversion element comprising at least a conductive substrate, a semiconductor layer adsorbing a photosensitizer, a charge transport layer, and a counter electrode, the photosensitizer is a compound represented by the formula (1), A photoelectric conversion element comprising a mixture of two or more kinds having different numbers of ammonium cations, and a compound in which 10% to 40% of all carboxyl groups in the photosensitizer molecule are converted to ammonium chloride.

(In formula (1), X represents hydrogen or an ammonium cation, and each X may be the same as or different from each other.) The photosensitizer adsorbed on the semiconductor layer is in the range of 2.0 × 10 ⁻⁴ mol / cm ^{3 to} 3.0 × 10 ⁻⁴ mol / cm ³ per unit volume of the semiconductor layer, and 1 per unit area of the semiconductor. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is in a range of 0.0 × 10 ⁻⁸ mol / cm ^{2 to} 1.0 × 10 ⁻⁶ mol / cm ² . The photoelectric conversion device according to claim 1 or 2 semiconductor layer is characterized in that it is formed of a metal oxide. The photovoltaic cell using the photoelectric conversion element in any one of Claims 1-3 .