JP2011216199A - Dye-sensitized solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new kind of dye-sensitized solar cell of high photoelectric conversion rate, in which component amount that contributes to power generation is not decreased, contact resistance is low, necking formation between metal oxide particulates such as titanium oxide or the like is not hindered, and an ink in order to form a semiconductor layer in the solar cell, and the dye-sensitized solar cell module.SOLUTION: The dye-sensitized solar cell 1 includes: an conductive base material 10; the semiconductor layer 20 that is arranged on the conductive base material 10 and contains a partially nitrided titanium oxide of needle shape which is made to carry the sensitized dye; a counter-electrode 40 arranged opposing to the semiconductor layer 20; and an electrolyte layer 30 that is arranged between the conductive base material 10 and the counter-electrode 40 and that contains a redox pair.

Description

  The present invention relates to a dye-sensitized solar cell, an ink for forming a semiconductor layer in the dye-sensitized solar cell, and a solar cell module.

  In recent years, global warming caused by carbon dioxide has become a global problem. In recent years, active research and development of solar cells using solar energy has been promoted as an environmentally friendly and clean energy source. . Among them, a dye-sensitized solar cell has attracted attention as a solar cell with higher photoelectric conversion efficiency and lower cost.

  A dye-sensitized solar cell includes, for example, a transparent substrate, a transparent conductive layer formed on the transparent substrate, a metal oxide semiconductor layer on which the dye is supported, and an electrolyte layer having a redox pair from the light incident side. In addition, the substrate on which the counter electrode is formed is sequentially stacked to form a cell. In particular, the Gretcher cell is characterized by using a porous metal oxide semiconductor layer obtained by firing titanium oxide, which is a nanoparticulate, and the adsorption amount of the sensitizing dye by making the metal oxide semiconductor layer porous. To increase the light absorption ability.

  For example, the dye-sensitized solar cell may be manufactured by first forming a porous semiconductor layer made of titanium oxide fine particles on a transparent conductive layer formed on the surface of a transparent substrate, and sensitizing the semiconductor layer. The dye is supported. Next, a catalyst such as a platinum film is coated on the counter electrode, and the semiconductor layer and the platinum film are overlapped so that they face each other. Then, an electrolyte is injected between them to form an electrolyte layer, and the side surface is sealed with an epoxy resin or the like. Stop. In this way, a dye-sensitized solar cell is produced.

  In such a Gretchel cell, the titanium oxide fine particles are bonded by point contact, and there is a problem that contact resistance increases. In addition, the contact resistance at the interface between the titanium oxide fine particles and the transparent conductive layer has a problem that the electronic energy is lost and the performance is deteriorated. Furthermore, if the thickness of the semiconductor layer is increased in order to obtain a current value, the distance of electron movement in the titanium oxide fine particles having a lower conductivity than that of the metal becomes longer, resulting in a greater loss due to resistance or recombination. Problem arises. That is, in a semiconductor layer using fine particles of titanium oxide, a battery such as a photoelectric conversion rate is low because of the contact resistance at the interface between fine particles or the interface between the fine particles and the conductive layer and because the electrical conductivity of the titanium oxide itself is small. It was difficult to improve the characteristics.

  On the other hand, (Patent Document 1) discloses a method for maintaining the conductivity of a semiconductor layer by mixing spherical conductive particles between dye-sensitized semiconductor particles (metal oxide fine particles) constituting the semiconductor layer. Is disclosed. Further, in Patent Document 2, at least an electrode having a semiconductor layer deposited on one surface thereof, a counter electrode facing the semiconductor layer of the electrode, and a gap between the semiconductor layer and the counter electrode are arranged. In the method of manufacturing a photoelectric conversion element having a formed electrolyte layer, the semiconductor layer is coated with a mixed paste or slurry of sensitizing dye-supporting semiconductor particles and elongated conductive particles on the surface of the electrode and heated. A method for producing a photoelectric conversion element is disclosed, wherein the conductive particles are brought into contact with each other and the conductive particles and the electrodes are brought into contact with each other by sintering. However, in this technique, as a result of the addition of conductive particles that cannot carry a sensitizing dye, there is a problem in that the relative amount of components that do not contribute to power generation increases and the generated charge decreases. Further, since the elongated conductive particles and the semiconductor particles are merely in contact, there is a drawback that the contact resistance is still high. That is, in general, when forming a semiconductor layer, by performing a baking process at 300 to 700 ° C. on the semiconductor particles applied on the electrodes, the contact interface between the semiconductor particles is melted, and the molecules at the interface part are mutually connected. So-called necking that thermally diffuses into the semiconductor particles occurs, and as a result, the electrons injected from the sensitizing dye are smoothly conducted to improve the battery characteristics. There is a problem that the desired battery characteristics cannot be obtained due to inhibition by the presence of conductive particles.

JP-A-10-290018 Japanese Patent No. 4135323

  Therefore, in view of the above-described conventional situation, the present invention has a photoelectric conversion rate that does not reduce the amount of components that contribute to power generation, has low contact resistance, and does not inhibit the formation of necking between metal oxide fine particles such as titanium oxide. An object is to provide a high novel dye-sensitized solar cell, an ink for forming a semiconductor layer in the solar cell, and a dye-sensitized solar cell module.

  The present inventor has found that the above problems can be solved by using acicular partial titanium nitride oxide as a component constituting the semiconductor layer, and has completed the present invention.

  That is, the present invention includes a conductive substrate, a semiconductor layer that is disposed on the conductive substrate and includes acicular partial titanium nitride oxide supporting a sensitizing dye, and is disposed to face the semiconductor layer. A dye-sensitized solar cell including a counter electrode and an electrolyte layer including a redox couple disposed between the conductive substrate and the counter electrode.

  Moreover, this invention is a dye-sensitized solar cell in which the said semiconductor layer further contains the metal oxide fine particle which carry | supported the sensitizing dye.

  In addition, the present invention is a dye-sensitized solar cell in which the average axis ratio between the major axis and the minor axis in the acicular partially titanium nitride oxide is 5 or more and 50 or less.

The present invention, the needle-like portions titanium oxynitride is represented by the chemical formula _{TiO 2-x N} x, x is a dye-sensitized solar cell is 0.18 to 0.95.

  Further, the present invention is an ink for forming the semiconductor layer in the dye-sensitized solar cell, and includes an acicular partial titanium nitride oxide.

  Furthermore, the present invention is a dye-sensitized solar cell module formed by connecting a plurality of the dye-sensitized solar cells in series or in parallel.

  According to the present invention, acicular partial titanium nitride oxide can support a sensitizing dye, and thus can contribute to power generation. In addition, the needle-like partially oxidized titanium oxide itself has conductivity and can form necking with the metal oxide fine particles, so that the resistance loss at the interface can be reduced, and the dye has high photoelectric conversion efficiency. A sensitized solar cell can be obtained.

It is sectional drawing which shows one Embodiment of the dye-sensitized solar cell of this invention.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a cross-sectional view showing an embodiment of the dye-sensitized solar cell of the present invention. The dye-sensitized solar cell 1 includes a conductive substrate 10, a semiconductor layer 20 disposed on the conductive substrate 10, a counter electrode 40 disposed to face the semiconductor layer 20, and a conductive group. An electrolyte layer 30 including an oxidation-reduction pair disposed between the material 10 and the counter electrode 40 is schematically configured.

  Next, each member constituting the dye-sensitized solar cell 1 will be described.

(1) Conductive base material As the conductive base material 10, general conductive materials such as various metal foils and metal plates such as titanium and aluminum can be used, or substrates such as glass and plastic. It can also be obtained by forming a conductive layer on the surface. The substrate on which the conductive layer is formed may be transparent or opaque, but when the conductive base material 10 side is a light receiving surface, it is a transparent substrate with excellent light transmission. Is preferred. Furthermore, it is preferable that it is excellent in heat resistance, weather resistance, and gas barrier properties against water vapor and the like. Specifically, transparent flexible materials such as quartz glass, Pyrex (registered trademark), and synthetic quartz glass that are not flexible, ethylene-tetrafluoroethylene copolymer film, biaxially stretched polyethylene terephthalate film, polyethersulfone Examples thereof include plastic films such as a film, a polyether ether ketone film, a polyether imide film, a polyimide film, and polyethylene naphthalate (PEN). In particular, when a conductive substrate made of a flexible film having a plastic film as a substrate and a conductive layer formed thereon is employed, solar cells can be used for various purposes, and the solar cells can be reduced in weight and manufacturing cost. Can be reduced. The plastic film may be used alone as a substrate, or may be used in a state where two or more different plastic films are laminated.

  The thickness of the substrate of the conductive base material is preferably in the range of 15 μm to 500 μm.

The material of the conductive layer formed on the substrate is not particularly limited as long as it is excellent in conductivity. However, when the conductive substrate 10 side is a light receiving surface, the conductive layer transmits light. It is preferable that it is excellent in property. For example, as a material having excellent light _{permeability,} may be mentioned SnO 2, ITO, IZO, ZnO or the like. Among these, fluorine-doped SnO ₂ (FTO) and ITO are particularly preferably used because they are excellent in both conductivity and permeability.

Moreover, it is preferable to select a material for the conductive layer of the conductive base material so that the solar cell functions in consideration of its work function. For example, a high work function materials include Au, Ag, Co, Ni, Pt, C, ITO, and SnO _{2, SnO} 2, ZnO or the like fluorine-doped. On the other hand, examples of the material having a low work function include Li, In, Al, Ca, Mg, Sm, Tb, Yb, and Zr.

  Note that the conductive layer may be formed of a single layer or may be formed by stacking materials having different work functions.

  The thickness of the conductive layer is in the range of 0.1 nm to 500 nm, preferably in the range of 1 nm to 300 nm.

  A method for forming such a conductive layer is not particularly limited, and examples thereof include a vapor deposition method, a sputtering method, and a CVD method. Among these, the sputtering method is preferably used.

(2) Semiconductor Layer Next, the semiconductor layer 20 will be described. The semiconductor layer in the present invention is characterized by containing acicular partial titanium nitride oxide. The acicular partial titanium nitride oxide can be used alone, but usually further contains metal oxide fine particles in addition to this, and the acicular partial titanium nitride oxide and metal oxide fine particles are combined to form a semiconductor. It is preferable to constitute the layer. These acicular partial titanium nitride oxide and metal oxide fine particles carry a sensitizing dye, thereby having a function of conducting charges generated from the sensitizing dye by light irradiation.

  The film thickness of the semiconductor layer is preferably in the range of 1 μm to 100 μm, and more preferably in the range of 5 μm to 30 μm. This is because the film resistance of the semiconductor layer can be reduced within the above range, and light absorption by the semiconductor layer is sufficiently performed.

  “Needle shape” refers to a shape in which the length in one direction is sufficiently longer than the other direction, and is a concept including a so-called beard shape, fiber shape, or rod shape. This acicular partial titanium nitride oxide forms a network in the semiconductor layer and facilitates charge transfer in the thickness direction of the semiconductor layer. The size of the acicular partial titanium nitride oxide is generally about 0.1 to 200 μm in the major axis direction and about 0.01 to 20 μm in the minor axis direction orthogonal thereto, but is limited to this. is not. In addition, the average axis ratio (aspect ratio) between the major axis and the minor axis is generally larger (more elongated) so that a network can be easily formed in the semiconductor layer. When necking is formed between the two, the number of the necking sites is increased and the overall contact resistance is reduced, which is preferable. Specifically, the average axial ratio is preferably 5 or more and 50 or less, and particularly preferably 10 or more and 20 or less.

  Acicular titanium oxide can be prepared according to a conventionally known method. That is, acicular titanium oxide can be synthesized by treating normal titanium oxide fine particles as a raw material with an alkali or an acid. As an example, 20 g of titanium oxide fine particles (trade name: CR-EL, manufactured by Ishihara Sangyo Co., Ltd.) are mixed with 32 g of potassium hydroxide and 48 g of water, and hydrothermal synthesis is performed on this solution at 150 ° C. for 150 hours. By washing with 1 M hydrochloric acid, acicular titanium oxide having an average axial ratio of 10 can be obtained. In this case, the average axial ratio can be controlled to increase by increasing the reaction time.

Then, acicular partial titanium nitride oxide can be obtained by appropriately nitriding the acicular titanium oxide by firing in an ammonia atmosphere or the like. By nitriding partially and synthesizing TiN, conductivity is imparted to the particles. In addition, since titanium oxide remains in part, when the semiconductor layer further contains metal oxide fine particles, necking is formed between the metal oxide fine particles by firing, and the contact resistance of the interface is reduced. Can be reduced. The degree of partial nitriding can be controlled by changing the nitriding conditions such as the firing temperature and time, and is appropriately set in consideration of the balance of the performance of the solar cell to be manufactured. Specifically, when the partially nitrided titanium oxide is represented by the chemical formula TiO _2-x N _x , x is 0.18 or more and 0.95 or less (N / O ratio (molar ratio) is 0.1 or more and 0.9 or less). It is preferable to perform nitriding so that the N / O ratio (molar ratio) corresponds to 0.2 or more and 0.6 or less.

  When the metal oxide fine particles are further included in addition to the acicular partial titanium nitride oxide as described above, the metal oxide fine particles are porous having communication holes because the sensitizing dye is supported in the pores. Preferably there is. By using such a porous material, the surface area of the semiconductor layer is increased, and a sufficient amount of a sensitizing dye can be carried. Moreover, a contact area with the electrolyte layer mentioned later becomes large, and energy conversion efficiency can be improved.

The metal oxide fine particles are not particularly limited as long as the charges generated from the sensitizing dye can be conducted to the conductive layer of the conductive substrate 10. _{Specifically, TiO 2, ZnO, SnO 2} , ITO, ZrO 2, SiO 2, MgO, Al 2 O 3, CeO 2, Bi 2 O 3, Mn 3 O 4, Y 2 O 3, WO 3, Ta ₂ O ₅ , Nb ₂ O ₅ , La ₂ O _{3 and the} like can be mentioned. Any one kind of these metal oxide fine particles may be used, or two or more kinds may be mixed and used. Among these, TiO ₂ can be preferably used. Further, a core-shell structure in which one of these is used as a core particle and the core particle is coated with another metal oxide fine particle to form a shell may be used.

  The particle diameter of the metal oxide fine particles is preferably in the range of 1 nm to 10 μm, particularly in the range of 10 nm to 500 nm. Within this range, it is preferable because the particles can be produced efficiently and the dispersibility of the particles is excellent.

  Mixtures of the same or different metal oxide fine particles having different particle diameters may be used. As a result, the light scattering effect can be enhanced and more light can be confined in the semiconductor layer, so that light absorption by the sensitizing dye can be efficiently performed. For example, a case where metal oxide fine particles of 10 nm to 50 nm and metal oxide fine particles of 50 nm to 200 nm are mixed and used can be exemplified.

  The content of the above-mentioned acicular partial titanium nitride oxide (not including the sensitizing dye) in the semiconductor layer is in the range of 10% by weight to 100% by weight, particularly in the range of 50% by weight to 100% by weight. It is preferable to do. When the metal oxide fine particles are further contained, the total amount of the acicular partial titanium nitride oxide and the metal oxide fine particles is 10% by weight to 100% by weight, particularly 50% by weight to 100% by weight of the semiconductor layer. It is preferable to design to occupy.

  The sensitizing dye supported on the acicular partial titanium nitride oxide and the metal oxide fine particles is not particularly limited as long as it can absorb light and generate an electromotive force. Specifically, an organic dye or a metal complex dye can be used. Examples of organic dyes include acridine, azo, indigo, quinone, coumarin, merocyanine, phenylxanthene, indoline, and squalium dyes. In particular, a coumarin system is preferably used.

  As the metal complex dye, a ruthenium dye, particularly a ruthenium bipyridine dye and a ruthenium terpyridine dye are preferably used. By supporting such a sensitizing dye on acicular partial titanium nitride oxide and metal oxide fine particles, it is possible to efficiently take in the visible light range and cause photoelectric conversion.

  A method for forming the semiconductor layer is not particularly limited, but it is preferably formed by a coating method. That is, by using a known disperser such as a homogenizer, ball mill, sand mill, roll mill, planetary mixer, etc., an ink in which acicular titanium oxide and, if necessary, metal oxide fine particles are dispersed in a solvent is prepared, This ink is applied onto the conductive layer of the conductive substrate 10, dried, and further baked as necessary. Thereafter, the sensitizing dye is adsorbed on the acicular titanium oxide and the metal oxide fine particles, whereby a semiconductor layer carrying the sensitizing dye can be formed.

  The solvent used for the ink for forming the semiconductor is not particularly limited. Specifically, chlorine solvents such as chloroform, methylene chloride, dichloroethane, ether solvents such as tetrahydrofuran, aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone and methyl ethyl ketone, ethyl acetate, butyl acetate And ester solvents such as ethyl cellosolve acetate, alcohol solvents such as isopropyl alcohol, ethanol, methanol and butyl alcohol, N-methyl-2-pyrrolidone, and pure water.

  In addition, if necessary, various additives may be used in order to improve the coating suitability of the ink used for forming the semiconductor layer. As the additive, a surfactant, a viscosity adjuster, a dispersion aid, a pH adjuster and the like can be used. Examples of the pH adjuster include nitric acid, hydrochloric acid, acetic acid, ammonia and the like.

  The method for applying the ink for forming the semiconductor is not particularly limited as long as it is a known application method, but specifically, die coating, gravure coating, gravure reverse coating, roll coating, reverse roll coating, bar coating, blade Examples include coat, knife coat, air knife coat, slot die coat, slide die coat, dip coat, micro bar coat, micro bar reverse coat, and screen printing. Using such a coating method, the semiconductor layer is formed so as to have a desired film thickness by repeating coating and drying once or a plurality of times.

  After coating and drying, baking is performed as necessary. As a result, the semiconductor layer can be homogenized and densified, and since the necking between the metal oxide fine particles or between the metal oxide fine particles and the needle-like partial titanium nitride oxide is increased, Charge conductivity can be improved. In addition, the adhesion between the conductive substrate and the semiconductor layer can be improved. The firing temperature and time differ depending on the film thickness of the semiconductor layer and are not limited, but are generally about 300 to 700 ° C. and about 5 to 120 minutes. Moreover, when a conductive base material is comprised from a flexible film, it is preferable to perform drying and baking below the heat-resistant temperature of a film.

  Examples of the method for supporting the sensitizing dye include, for example, a method in which the dried and fired acicular partially oxidized titanium oxide and metal oxide fine particles are immersed in a sensitizing dye solution and then dried, or a sensitizing dye solution is used. Examples of the method include coating on needle-like partial titanium nitride oxide and metal oxide fine particles, infiltrating, and drying. The solvent used in the sensitizing dye solution is appropriately selected from an aqueous solvent and an organic solvent according to the type of the dye sensitizer used.

(3) Counter Electrode Next, the counter electrode 40 will be described. As the counter electrode 40, general conductive materials such as various metal foils such as titanium and aluminum and metal plates can be used, or a conductive layer is formed on the surface of a substrate such as glass or plastic. Can also be obtained. The substrate may be transparent or opaque, but when the counter electrode 40 side is a light receiving surface, it is preferably a transparent substrate having excellent light transmittance. Furthermore, it is preferable that it is excellent in heat resistance, weather resistance, and gas barrier properties against water vapor and the like. Specifically, transparent flexible materials such as quartz glass, Pyrex (registered trademark), and synthetic quartz glass that are not flexible, ethylene-tetrafluoroethylene copolymer film, biaxially stretched polyethylene terephthalate film, polyethersulfone Examples thereof include plastic films such as a film, a polyether ether ketone film, a polyether imide film, a polyimide film, and polyethylene naphthalate (PEN). In particular, when a counter electrode made of a flexible film having a conductive layer formed on a plastic film as a substrate is employed, solar cells can be used for various applications, and the solar cells can be reduced in weight and manufacturing cost. Can be reduced. The plastic film may be used alone as a substrate, or may be used in a state where two or more different plastic films are laminated.

  The thickness of the counter electrode substrate is preferably in the range of 15 μm to 500 μm.

The material of the conductive layer formed on the substrate is not particularly limited as long as it has excellent conductivity. However, when the counter electrode 40 side is a light receiving surface, the conductive layer is light transmissive. It is preferable that it is excellent. For example, as a material having excellent light _{permeability,} may be mentioned SnO 2, ITO, IZO, ZnO or the like. Among these, fluorine-doped SnO ₂ (FTO) and ITO are particularly preferably used because they are excellent in both conductivity and permeability.

Moreover, it is preferable to select a material for the conductive layer of the counter electrode so as to function as a solar cell in consideration of the work function. For example, a high work function materials include Au, Ag, Co, Ni, Pt, C, ITO, and SnO _{2, SnO} 2, ZnO or the like fluorine-doped. On the other hand, examples of the material having a low work function include Li, In, Al, Ca, Mg, Sm, Tb, Yb, and Zr.

  Note that the conductive layer of the counter electrode may be formed of a single layer or may be formed by stacking materials having different work functions.

  The thickness of the conductive layer of the counter electrode is in the range of 0.1 nm to 500 nm, preferably in the range of 1 nm to 300 nm.

  A method for forming such a conductive layer is not particularly limited, and examples thereof include a vapor deposition method, a sputtering method, and a CVD method. Among these, the sputtering method is preferably used.

  Moreover, the power generation efficiency of the dye-sensitized solar cell can be further improved by forming a catalyst layer on the conductive layer of the counter electrode. Examples of the catalyst layer include a layer deposited with Pt and a catalyst layer made of an organic material such as polyaniline, polythiophene, polypyrrole, but are not limited thereto.

(4) Electrolyte Layer Next, the electrolyte layer 30 will be described. The electrolyte layer 30 is disposed between the conductive substrate 10 and the counter electrode 40, and is produced by removing the solvent from the coating solution containing at least the electrolytic solution containing the redox couple and the solvent.

  The redox couple can be appropriately selected from those generally used in the electrolyte layer. Specifically, a redox couple of iodine or a redox couple of bromine is preferably used. Examples of the redox pair of iodine include combinations of iodine and iodides such as lithium iodide, sodium iodide, potassium iodide, calcium iodide, and TPAI (tetrapropylammonium iodide). Examples of the redox pair of bromine include combinations of bromine and bromides such as lithium bromide, sodium bromide, potassium bromide, and calcium bromide.

  The concentration of the redox couple in the electrolyte layer 30 varies depending on the type of the redox couple and is not particularly limited. In general, when an iodine or bromine redox couple is used, iodine or bromine is 0% in the electrolyte layer. 0.001 to 0.5 mol / l, and iodide or bromide is preferably 0.1 to 5 mol / l.

  The electrolyte layer 30 may contain an ionic liquid (room temperature molten salt) for the purpose of reducing the viscosity of the electrolyte and improving the conductivity of ions to improve the photoelectric conversion efficiency. Since the ionic liquid has an extremely low vapor pressure, it hardly evaporates substantially at room temperature, and there is no fear of volatilization or ignition like a general organic solvent, so that deterioration of cell characteristics due to volatilization can be prevented.

  Examples of the ionic liquid include cations such as 1-methyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, and 1-octyl-3-methylimidazolium. 1-octadecyl-3-methylimidazolium, 1-methyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-hexyl-2,3-dimethylimidazolium, 1-octyl -Imidazoles such as -2,3-dimethylimidazolium and 1-octadecyl-2,3-dimethylimidazolium, pyridiums such as 1-methylpyridium, 1-butylpyridium and 1-hexylpyridium, alicyclic rings Formula amines, aliphatic amines, phosphoniums such as tetrabutylphosphonium, triethyls Sulfonium-based compounds such as phonium, and anion ions such as iodine ion, bromine ion, chlorine ion, tetrafluoroborate, hexafluoroborate, trifluoromethanesulfonate, trifluoroacetate, etc., fluorine-based, cyanate-based, thiocyanate-based, etc. Can be mentioned. Any one of these substances may be used alone, or a plurality of these substances may be mixed and used.

  In particular, it is preferable to use an iodide ionic liquid having iodine as an anion. Specifically, for example, 1,2-dimethyl-3-n-propylimidazolium iodide, 1-methyl-3-n-propylimidazolium iodide, 1-propyl-3-methylimidazolium iodide, 1 -Butyl-2,3-dimethylimidazolium iodide, 1-hexyl-3-methylimidazolium iodide, etc. can be mentioned. These iodide-based ionic liquids are a source of iodine ions and can also function as the above-described redox couple.

  The concentration of the ionic liquid in the electrolyte layer varies depending on the type of the ionic liquid. An ionic liquid that also functions as a redox pair, such as an iodide ionic liquid, should be contained as a redox pair, and the concentration described above for the redox pair is preferable, that is, in the electrolyte layer. It is preferable to contain 0.1-5 mol / l. In that case, iodides other than the iodide-based ionic liquid may or may not be contained. As a result, the total concentration of iodides functioning as a redox pair may be 0.1 to 5 mol / l.

  In addition, the electrolyte layer 30 can contain various additives for the purpose of improving durability, improving open-circuit voltage value, and the like. Specific examples of the additive include guanidinium thiocyanate, tertiary butyl pyridine, N-methylbenzimidazole and the like. The concentration of these additives in the electrolyte layer is preferably 1 mol / l or less in the electrolyte layer by adding the various additives.

  The thickness of the electrolyte layer 30 is preferably in the range of 2 μm to 150 μm including the thickness of the semiconductor layer 20, and preferably in the range of 10 μm to 50 μm. If the film thickness is too small, the semiconductor layer and the counter electrode may come into contact with each other and cause a short circuit. Conversely, if the film thickness is too large, the internal resistance increases, leading to performance degradation.

  As a method of forming the electrolyte layer 30, a method of forming the semiconductor layer 20 by applying a coating liquid used for forming the electrolyte layer on the semiconductor layer 20 and drying it (hereinafter referred to as a coating method), or forming the semiconductor layer 20. Examples include a method of forming an electrolyte layer (hereinafter referred to as an injection method) by disposing the conductive substrate 10 and the counter electrode 40 so as to have a predetermined gap and injecting a coating liquid into the gap. it can.

  The solvent of the coating solution can be selected as appropriate, and specific examples include alcohol solvents such as ethanol, ketone solvents such as methyl ethyl ketone, amide solvents such as N-methylpyrrolidone, and pure water. In particular, from the viewpoint of the stability of the coating solution and the film formability of the electrolyte, it is preferable to use a redox couple and a solvent in which the ionic liquid exhibits solubility, for example, an alcohol solvent such as ethanol is preferably used. It is done.

  In the coating method, known means can be used as means for applying the coating liquid onto the semiconductor layer 20, and specifically, die coating, gravure coating, gravure reverse coating, roll coating, reverse roll coating, bar Examples include coating, blade coating, knife coating, air knife coating, slot die coating, slide die coating, dip coating, micro bar coating, micro bar reverse coating, and screen printing. After coating, the electrolyte layer can be formed by appropriately drying and removing the solvent.

  The dye-sensitized solar cell of the present invention can be obtained by bonding the catalyst layer side of the counter electrode 40 to the electrolyte layer 30 thus formed.

  When the electrolyte layer 30 is formed by an injection method, first, the conductive substrate 10 on which the semiconductor layer 20 is formed and the counter electrode 40 are arranged so as to face each other with a predetermined gap. The gap at this time is preferably set so that the distance between the conductive substrate 10 and the counter electrode 40 is 2 μm to 150 μm. In order to dispose the counter electrode 40 with a predetermined gap, a spacer can be provided on either the conductive substrate 10 side or the counter electrode 40 side. Examples of such a spacer include known glass spacers and resin spacers.

  Next, the coating solution used for forming the electrolyte layer can be injected into the gap by utilizing a capillary phenomenon or the like, and cured as necessary to form the electrolyte layer 30. Thereby, a dye-sensitized solar cell can be obtained.

  Furthermore, a dye-sensitized solar cell module can be obtained by connecting a plurality of the dye-sensitized solar cells 1 obtained as described above in series or in parallel. Specifically, for example, a plurality of dye-sensitized solar cells are arranged in a planar shape or a curved shape, and non-conductive partition walls are provided between the cells to partition each cell. These members can be used for electrical connection, and a positive or negative electrode lead can be drawn from the end portion to form a module. The number of dye-sensitized solar cells constituting the module is arbitrary, and can be freely designed so as to obtain a desired voltage.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, it is not limited to this.

Example 1
<Preparation of acicular partial titanium nitride oxide>
Acicular titanium oxide (trade name: FTL-300, average axial ratio 24) manufactured by Ishihara Sangyo Co., Ltd. was baked at 950 ° C. in an ammonia atmosphere to obtain acicular partial titanium nitride oxide. This needle part titanium oxynitride, composition was determined by X-ray photoelectron _{spectroscopy, TiO 2-x N x (} x is 0.2) had a composition of.

<Preparation of semiconductor layer forming ink>
5.65 g of porous titanium oxide fine particles (trade name: P25) manufactured by Nippon Aerosil Co., Ltd. were added to 9.77 g of ethanol, and 0.56 g of acicular partial titanium nitride oxide, 1.25 g of acetylacetone, zirconia beads ( The mixed solution to which 20 g (φ1.2 mm) was added was stirred with a paint shaker to prepare an ink for forming a semiconductor layer.

<Formation of semiconductor layer>
As a conductive substrate, transparent conductive glass (manufactured by Nippon Sheet Glass Co., Ltd., surface resistivity 6Ω / □) having a fluorine-doped tin oxide (FTO) film formed on a glass plate is prepared, and the above ink is FTO by a doctor blade method. It was applied to the film surface and then baked at 450 ° C. for 30 minutes to form a 10 μm thick layer containing a large number of metal oxide fine particles (titanium oxide fine particles) and acicular partial titanium nitride oxide. Subsequently, a ruthenium complex (manufactured by Solaronix, cis-bis (thiocyanato) -N, N-bis (2,2′-dipyridyl-4,4′-dicarboxylic acid) -ruthenium (II) dihydrate as a sensitizing dye Is dissolved in absolute ethanol to a concentration of 3 × 10 ⁻⁴ mol / l to prepare a dye solution, and a layer containing the above-described titanium oxide fine particles and needle-like partially titanium nitride oxide is added to this solution. It was immersed for 12 hours at room temperature. Thereafter, the dye solution was pulled up from the dye solution, and the dye solution adhering to the titanium oxide fine particles and the acicular partial titanium nitride oxide was washed with absolute ethanol and then air-dried. Thereby, a semiconductor layer was formed on the conductive substrate. Then, it trimmed so that a semiconductor layer might be set to 4 mm x 4 mm, and the conductive base material with a semiconductor layer for dye-sensitized solar cells whose size of a conductive base material is 10 x 10 mm was obtained.

<Preparation of counter electrode>
A platinum film is formed by sputtering on a transparent conductive glass (manufactured by Nippon Sheet Glass Co., Ltd., surface resistivity 6Ω / □) on which a fluorine-doped tin oxide (FTO) film is formed on a glass plate. Produced a 10 × 10 mm counter electrode.

<Preparation of coating solution for electrolyte layer formation>
To a solution obtained by mixing methoxyacetonitrile and valeronitrile at a volume ratio of 85:15 (volume mixing ratio), 0.03M iodine, 0.5M tert-butylpyridine, and 0.6M butylmethylimidazolium iodide were added, respectively. A coating solution for layer formation was prepared.

<Preparation of dye-sensitized solar cell>
On the conductive substrate on which the semiconductor layer (4 mm × 4 mm) is formed, an epoxy resin layer having a thickness of 30 μm is formed as a spacer so as to surround the periphery of the semiconductor layer, and then opposed to the semiconductor layer and the epoxy resin layer. The platinum layer of the electrode was bonded. Subsequently, a coating liquid for forming an electrolyte layer was injected from an injection port opened in the counter electrode, and the injection port was sealed with an epoxy resin and a glass plate to produce a target dye-sensitized solar cell.

<Evaluation of battery performance>
About the produced dye-sensitized solar cell, it makes it incident from the electroconductive base material side which has the semiconductor layer which carry | supported the sensitizing dye, using pseudo sunlight (AM1.5, incident light intensity: 100mW / cm < ² >) as a light source. A voltage was applied using a source measure unit (manufactured by Keithley, Model 2400), and current-voltage characteristics were measured. In addition, the area of the semiconductor layer used for the measurement is 0.16 cm ² (4 mm × 4 mm).

(Example 2)
Example 1 except that acicular titanium oxide FTL-200 (Ishihara Sangyo Co., Ltd., average axial ratio of 14) was used instead of acicular titanium oxide FTL-300 (Ishihara Sangyo Co., Ltd., average axial ratio of 24). A dye-sensitized solar cell was prepared in the same manner as described above, and the current-voltage characteristics were measured. In addition, the acicular titanium oxide had a composition of TiO _2-x N _x (x is 0.2).

(Example 3)
Example 1 except that acicular titanium oxide FTL-100 (Ishihara Sangyo Co., Ltd., average axis ratio 13) was used instead of acicular titanium oxide FTL-300 (Ishihara Sangyo Co., Ltd., average axis ratio 24). A dye-sensitized solar cell was prepared in the same manner as described above, and the current-voltage characteristics were measured. In addition, the acicular titanium oxide had a composition of TiO _2-x N _x (x is 0.2).

(Comparative Example 1)
A dye-sensitized solar cell was prepared in the same manner as in Example 1 except that no acicular partial titanium nitride oxide was added to the semiconductor-forming ink, and current-voltage characteristics were measured.

(Comparative Example 2)
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that acicular titanium oxide was not nitrided, and current-voltage characteristics were measured.

(Comparative Example 3)
Instead of acicular partial titanium nitride oxide, acicular conductive particles having a tin oxide-based conductive coating on a whisker-like aluminum borate core (Mitsui Metal Mining Co., Ltd., trade name: TYPE-V, average axial ratio) A dye-sensitized solar cell was prepared in the same manner as in Example 1 except that 8.0 and a minor axis diameter of 1 μm were used, and current-voltage characteristics were measured.

<Test results>
Table 1 below shows the results of performance evaluation. The fill factor (FF) is a value obtained by dividing the maximum output of the solar cell by the short circuit current (I _sc ) × the open circuit voltage (V _oc ), and the short circuit current density J _sc (A / The conversion efficiency η (%) of the solar cell can be obtained by dividing the value of cm ² ) × V _oc (V) × FF (%) by the incident light intensity.

  As is clear from the results in Table 1, the dye-sensitized solar cells of Examples 1 to 3 have higher output characteristics than the conventional dye-sensitized solar cells shown in Comparative Examples 1, 2, and 3. . This is because the contact resistance of the interface between the semiconductor layer and the conductive base material is reduced by containing conductive acicular partial titanium nitride oxide in the semiconductor layer, and the acicular partial titanium nitride oxide and This is probably because necking was formed between the fine particles of titanium oxide. Furthermore, unlike the case of Comparative Example 3, the acicular partial titanium nitride oxide in the present invention can contribute to power generation because the sensitizing dye is carried by itself.

DESCRIPTION OF SYMBOLS 1 Dye sensitized solar cell 10 Conductive base material 20 Semiconductor layer 30 Electrolyte layer 40 Counter electrode

Claims (6)

A conductive substrate;
A semiconductor layer that is disposed on a conductive substrate and includes acicular partial titanium nitride oxide carrying a sensitizing dye;
A counter electrode disposed opposite the semiconductor layer;
An electrolyte layer comprising a redox couple disposed between the conductive substrate and the counter electrode;
A dye-sensitized solar cell comprising:   The dye-sensitized solar cell according to claim 1, wherein the semiconductor layer further contains metal oxide fine particles carrying a sensitizing dye.   3. The dye-sensitized solar cell according to claim 1, wherein an average axial ratio between a major axis and a minor axis in the needle-like partially titanium nitride oxide is 5 or more and 50 or less. Acicular parts titanium oxynitride is represented by the chemical formula _{TiO 2-x N} x, dye-sensitized solar cell according to any one of claims 1 to 3 x is 0.18 to 0.95.   It is an ink for forming the said semiconductor layer in the dye-sensitized solar cell in any one of Claims 1-4, Comprising: The said ink containing acicular partial titanium nitride oxide.   A dye-sensitized solar cell module formed by connecting a plurality of the dye-sensitized solar cells according to claim 1 in series or in parallel.

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