JP2007095664A - Photoelectric transfer device and dye-sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell having a high transfer efficiency while being a total solid type and with superior durability by applying in combination an organic charge transporting substance and an antioxidant in the charge transporting layer of a solar cell. <P>SOLUTION: The photoelectric transfer element and the solar cell have a dye-sensitized semiconductor electrode, a charge transporting layer, and a counter electrode on a conductive support body. The charge transporting layer contains a charge transporting substance and an antioxidant in this photoelectric transfer element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element and a dye-sensitized solar cell, and more particularly to a dye-sensitized photoelectric conversion element and a dye-sensitized solar cell containing a charge transport material and an antioxidant.

  For solar power generation, single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, compound solar cells such as cadmium telluride and indium copper selenide have been put into practical use or the main research and development targets. In practical terms, it is necessary to overcome problems such as manufacturing costs and securing raw materials. On the other hand, many solar cells using organic materials aimed at increasing the area and reducing the cost have been proposed, but have problems such as low conversion efficiency and poor durability. Under such circumstances, a photoelectric conversion element and a solar cell using semiconductor fine particles sensitized with a dye, and a material and a manufacturing technique for producing the photoelectric conversion element are disclosed (for example, see Non-Patent Document 1 and Patent Document 1). .) The proposed solar cell is a wet solar cell using a titanium oxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode. The first advantage of this method is that an inexpensive oxide semiconductor such as titanium oxide can be used without being purified with high purity, so that an inexpensive photoelectric conversion element can be provided. A second advantage is that light in almost all wavelength regions of visible light can be converted into electricity because the absorption of the dye used is broad.

However, in the proposed solar battery, an electrolyte solution containing iodine ions is used as the electrolyte in the cell. Such a liquid electrolyte has a problem that it is easily depleted, has poor stability as a solar cell, and has a short lifetime. Furthermore, since it is a liquid, the processability in a manufacturing process is bad, and it was thought that the application to a flexible solar cell like a plastic substrate was also difficult. In contrast, attempts have been made to improve the stability and workability of solar cells by using a solid electrolyte (charge transport layer). For example, in a photoelectric conversion element having a conductive support and a semiconductor electrode including semiconductor fine particles adsorbing a dye coated thereon, a charge transport layer, and a counter electrode, the charge transport layer is a p-type inorganic compound semiconductor and a molten salt electrolyte Has been described (see, for example, Patent Document 2). In addition, an element in which an organic charge transport material is contained in a polymer having a charge transport layer having transparency has been proposed (see, for example, Patent Document 3). However, in the p-type inorganic compound semiconductor, the photoelectric conversion efficiency is remarkably lowered, and the organic charge transport material is not able to overcome the durability problem due to oxidative degradation.
US Pat. No. 4,927,721 JP 2001-230434 A JP 2004-356281 A Nature (Vol. 353, pages 737-740, 1991)

  The object of the present invention is to apply a combination of an organic charge transport material and an antioxidant to a charge transport layer of a solar cell, thereby providing a dye sensitization having high conversion efficiency and excellent durability while being an all-solid type. It is to provide a solar cell.

  The above object of the present invention can be achieved by the following configuration.

  1. A photoelectric conversion device having a dye-sensitized semiconductor electrode, a charge transport layer, and a counter electrode on a conductive support, wherein the charge transport layer contains a charge transport material and an antioxidant. element.

  2. 2. The photoelectric conversion element as described in 1 above, wherein the antioxidant is a hindered amine compound or a hindered phenol compound.

  3. 3. The photoelectric conversion element as described in 1 or 2 above, wherein the content of the antioxidant is 0.01 to 20% by mass with respect to the mass of the charge transport layer.

  4). 4. The photoelectric conversion element according to any one of 1 to 3, wherein the charge transport layer contains a charge transport material having a molecular weight of 750 to 100,000.

  5. 5. The photoelectric conversion element as described in any one of 1 to 4 above, wherein the charge transport layer contains a polymer charge transport material and an antioxidant and does not contain a binder resin.

  6). 6. The photoelectric conversion element as described in 5 above, wherein the polymer charge transport material is a conductive polymer.

  7). 7. The photoelectric conversion device as described in any one of 1 to 6 above, further comprising an insulating layer or a blocking layer made of a semiconductor between the conductive support and the dye-sensitized semiconductor electrode. .

  8). The film thickness of the said semiconductor electrode is 100-10000 nm, The photoelectric conversion element of any one of said 1-7 characterized by the above-mentioned.

  9. 9. The photoelectric conversion element according to any one of 1 to 8, wherein the charge transport layer has a thickness of 0.1 to 20 μm.

  10. A dye-sensitized solar cell comprising the photoelectric conversion element according to any one of 1 to 9 above.

  According to the present invention, by applying a combination of an organic charge transport material and an antioxidant to a charge transport layer of a solar cell, the dye-sensitized solar cell having high conversion efficiency and excellent durability while being an all solid type Could be provided. In particular, as organic charge transport materials, high molecular weight charge transport materials having a molecular weight of 750 to 100,000, as well as oligomers and polymer type charge layer materials, which are not described in the prior application, are particularly high as charge transport materials. It is preferable as an electrolyte for an all solid-state solar cell.

  The present invention will be described in more detail. The present invention relates to a photoelectric conversion device having a dye-sensitized semiconductor electrode, a charge transport layer, and a counter electrode on a conductive support, and an antioxidant for the photoelectric conversion device having a charge transport layer containing an organic charge transport material. It has been found that a photoelectric conversion element that can significantly improve the element life and is resistant to environmental fluctuations can be obtained by containing the element.

  As shown in FIG. 1, the photoelectric conversion element of the present application has a conductive support 4, a semiconductor electrode 3 (dye sensitized in the present invention), a charge transport layer 2, and a counter electrode 1 as shown in FIG. It is the comprised photoelectric conversion element. The conductive support 4 is preferably a transparent conductive layer that absorbs less light and scatters light. Specifically, ITO, antimony-doped tin oxide, zinc oxide, or the like is used. In addition to the above basic structure, the photoelectric conversion element of the present invention may arbitrarily form an additional layer. For example, an insulating layer or a semiconductive layer may be added as a blocking layer in order to suppress unnecessary leakage between the conductive support 4 and the dye-sensitized semiconductor electrode 3. As the blocking layer, a metal oxide having a specific adsorbing group may be used for the purpose of improving not only the blocking effect but also the adhesion to the support. Alternatively, a blocking layer may be provided between the dye-sensitized semiconductor electrode 3 and the charge transport layer 2.

  Next, a semiconductor electrode that can be used in the present invention will be described. As a semiconductor used for the semiconductor electrode of the photoelectric conversion element of the present invention, a simple substance such as silicon or germanium, a group 3 to a group 5 or a group 13 to a group 15 of a periodic table (also referred to as an element periodic table). Compounds having these elements, metal chalcogenides (for example, oxides, sulfides, selenides, etc.), metal nitrides, and the like can be used.

  Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxides, cadmium, zinc, lead, silver, antimony or Bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like. Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, gallium-arsenic or copper-indium selenide, copper-indium sulfide, titanium nitride, and the like.

Specific examples of the semiconductor according to the photoelectric conversion element of the present invention include TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, ZnS, PbS, Bi ₂ S ₃ , CdSe, CdTe. , GaP, InP, GaAs, CuInS ₂ , CuInSe ₂ , Ti ₃ N _4, etc., but TiO ₂ , ZnO, SnO ₂ , Fe ₂ O ₃ , WO ₃ , Nb ₂ O ₅ , Among these, CdS and PbS are preferably used as metal oxides or metal sulfide semiconductors. Of these, a metal oxide semiconductor is more preferably used, and among them, TiO ₂ or Nb ₂ O ₅ is used, and TiO ₂ is more preferably used.

The semiconductor used for the photoelectric conversion element of the present invention may be used in combination with a plurality of semiconductors described above. For example, several types of metal oxides or metal sulfides described above can be used in combination, or 20% by mass of titanium nitride (Ti ₃ N ₄ ) may be mixed and used in the titanium oxide semiconductor. In addition, J.H. Chem. Soc. , Chem. Commun. 15 (1999). At this time, when a component is added as a semiconductor in addition to the metal oxide or metal sulfide, the mass ratio of the additional component to the metal oxide or metal sulfide semiconductor is preferably 30% or less.

  Any dye can be used as long as it can spectrally sensitize the semiconductor according to the present invention. In order to increase the wavelength range of photoelectric conversion as much as possible and increase the conversion efficiency, it is preferable to mix two or more kinds of dyes. Moreover, the pigment | dye to mix and its ratio can be selected so that it may match with the wavelength range and intensity distribution of the target light source.

  Examples of the dye that can be used in combination with the compound according to the present invention include metal complex dyes, phthalocyanine dyes, porphyrin dyes, from a comprehensive viewpoint such as photoelectron transfer reaction activity, photo durability, and photochemical stability. A polymethine dye or a solvent-soluble pigment derivative (latent pigment) in which a protecting group that promotes solvent solubility is introduced into the base skeleton constituting the pigment is preferably used.

  Among the metal complex dyes, JP-A Nos. 2001-223037, 2001-226607, US Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440, JP-A-7-249750, JP 10-504512, World Patent 989/50393, etc. Ruthenium complex dyes are preferably used.

  Examples of the porphyrin dye and the phthalocyanine dye include dyes described in JP-A No. 2001-223037 as preferable dyes.

  Examples of the polymethine dye include conventionally known methine dyes, JP-A Nos. 11-35836, 11-158395, 11-163378, 11-214730, and 11-214731. 10-093118, 11-273754, JP-A-2000-106224, 2000-357809, 2001-052766, EP 892,411, 911,841, etc. Those described are mentioned.

  The photoelectric conversion element of the present invention can be sensitized by any of the dyes described above, and can achieve the effects described in the present invention. Here, the sensitizing treatment with the dye includes various modes such as adsorption of the dye to the semiconductor surface, and when the semiconductor has a porous structure such as a porous structure, the dye enters the porous structure of the semiconductor. It is done.

In addition, the total content of the dye per 1 m ^{2 of} the semiconductor layer (semiconductor electrode) is preferably in the range of 0.01 mmol to 100 mmol, more preferably 0.1 mmol to 50 mmol, and particularly preferably 0. 5 to 20 mmol.

  In particular, when the application of the photoelectric conversion element of the present invention is a solar cell to be described later, two or more types having different absorption wavelengths can be used so that sunlight can be used effectively by widening the wavelength range of photoelectric conversion. It is preferable to use a mixture of dyes.

  A general method is to dissolve a dye in a suitable solvent (such as ethanol) in a semiconductor and immerse a well-dried semiconductor in the solution for a long time.

  When preparing a photoelectric conversion element using a combination of a plurality of dyes, a mixed solution of each compound may be prepared and used, or a solution is prepared for each compound and prepared by sequentially immersing in each solution. You can also When preparing a separate solution for each compound and immersing in each solution in order, the effects described in the present invention can be obtained regardless of the order in which the semiconductor, the sensitizing dye, and the like are included in the semiconductor. be able to. Further, it may be produced by mixing semiconductor fine particles on which the compound is adsorbed alone.

  The adsorption treatment may be performed when the semiconductor is in the form of particles, or may be performed after forming a film on the support. The solution in which the compound used for the adsorption treatment is dissolved may be used at room temperature, or may be used by heating in a temperature range in which the compound does not decompose and the solution does not boil. Moreover, you may implement adsorption | suction of the said compound after application | coating of a semiconductor fine particle (after formation of a photosensitive layer) like manufacture of the photoelectric conversion element mentioned later. Moreover, you may implement adsorption | suction of the said compound by apply | coating a semiconductor fine particle and the said compound of this invention simultaneously. Unadsorbed compounds can be removed by washing.

  In the case of a photoelectric conversion element having a semiconductor thin film with a high porosity, a dye adsorption process (photoelectric conversion) is performed before water is adsorbed on the semiconductor thin film and in the voids inside the semiconductor thin film by moisture, water vapor, or the like. It is preferable to complete the element sensitization process.

  The photoelectric conversion element of the present invention may be surface-treated using an organic base. Examples of the organic base include diarylamine, triarylamine, pyridine, 4-t-butylpyridine, polyvinylpyridine, quinoline, piperidine, amidine, and the like, among which pyridine, 4-t-butylpyridine, and polyvinylpyridine are preferable. .

  Surface treatment can be carried out by preparing a solution dissolved in an organic solvent as it is when the organic base is a liquid and by immersing the photoelectric conversion element of the present invention in a liquid amine or an amine solution.

  Moreover, in this invention, you may have a blocking layer which consists of an insulator layer or a semiconductor further on the electroconductive support body and the said dye-sensitized semiconductor electrode. The blocking layer is preferably not decomposed and deteriorated under the conditions for forming the semiconductor layer and the carrier transport layer to be formed thereafter. For example, a metal oxide layer or a silicon nitride layer formed by a sol-gel method is preferable. Examples of the metal oxide used here include oxides such as Si, Ti, and Zr.

  These metal oxide layers are preferable because a coating film obtained by sol-gel reaction of an alkoxy metal as a precursor can form a uniform thin film. More preferably, an oligomer having a slightly advanced reaction is used as a starting material, so that the reaction rate is increased and a denser film is formed.

  Next, the charge transport layer will be described. The charge transport layer of the present invention is a layer that is solid at room temperature and contains a compound that transports charges, and is formed by dispersing and mixing a low molecular charge transport material (also referred to as CTM) in a binder layer. It is conceivable that the layer is formed of layers, or the binder itself is a polymer charge transport material having charge transport ability. These layers can be formed, for example, by dissolving a charge transporting substance and a binder in a solvent, and applying and drying the same. Alternatively, it can be formed by using a polymer charge transport material having different mass average molecular weights as a main component, dissolving or dispersing the polymer charge transport material in an appropriate solvent, and applying and drying it. Unlike the charge transport layer of the present application and, for example, a conventionally known electrolyte, it is not an ion-dissociated electrolyte. The electrolyte usually requires a solvent or a liquid because of the need for ion dissociation, and is more stable than the photoelectric conversion element of the present application.

  The charge transporting substance can be classified into a low molecular weight charge transporting substance, a large molecular weight charge transporting substance, and a high molecular weight charge transporting substance from the viewpoint of molecular weight. The low molecular weight is a low molecular weight molecule having a molecular weight of less than 750, and the large molecular weight charge transporting substance has a molecular weight of 750 or more and can be specified as a molecular structure, and at most several kinds of isomers or several kinds It is a group of compounds containing compounds with different molecular structures. High molecular weight charge transporting substances are difficult to uniquely identify molecular structures, and charge transporting compounds that can identify a group of compounds by molecular weight distribution. It is. The molecular weight can be measured by a well-known FDMAS method for low molecular weight and large molecular compounds.

  If the molecular weight is low, the molecular structure may be specified and calculated using NMR, IR, and MAS spectra. In the case of polymer CTM, there are several methods for measuring the molecular weight, but in this application, it is defined by the number average molecular weight in terms of styrene by GPC.

  GPC measurement conditions are as follows: 1 ml of THF is added to 1 mg of a sample, and the mixture is stirred at room temperature using a magnetic stirrer and sufficiently dissolved. Next, after filtration through a membrane filter having a pore size of 0.45 to 0.50 μm, the solution is injected into GPC. The measurement conditions of GPC are measured by stabilizing the column at 40 ° C., adding THF at a flow rate of 1 ml / min, and injecting about 100 μl of a sample having a concentration of 1 mg / ml. As the column, TSK-GEL SUPER HZM-M 4.6 × 150 manufactured by Tosoh Corporation, and Gardrum TSK guardcolumn super HZ-L were used.

  As the detector, a refractive index detector (IR detector) or a UV detector is preferably used. In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve created using monodisperse polystyrene standard particles. About 10 points are preferably used as polystyrene for preparing a calibration curve.

  Examples of the low molecular weight charge transporting material include triphenylamine compounds represented by the following general formulas [I], [II] and [III], and benzidine compounds represented by the general formula [III ′]. It is done.

In the formula, Ar ₁ and Ar ₂ each represent an alkyl group or an aryl group, Ar ₃ represents a phenylene group, and _one of Ar ₁ and Ar ₂ may be bonded to Ar ₃ to form a ring. R ₁ , R ₂ and R ₃ each represent a hydrogen atom, an alkyl group or an aryl group, and R ₂ and R ₃ may combine to form a ring. Although the typical example of general formula [I] is shown below, this invention is not limited to these.

In the formula, Ar ₄ represents an alkyl group or an aryl group, and Ar ₅ represents a phenylene group. R ₄ and R ₅ each represent a hydrogen atom, an alkyl group or an aryl group, and R ₄ and R ₅ may be bonded to form a ring. Although the typical example of general formula [II] is shown below, this invention is not limited to these.

In the formula, Ar ₆ and Ar ₇ each represents an alkyl group or an aryl group, Ar ₃ represents a phenylene group, and one of Ar ₆ and Ar ₇ and a phenylene group bonded to a nitrogen atom are bonded to form a ring. It may be formed. R ₆ represents a hydrogen atom, an alkyl group or an aryl group, and R ₇ represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom.

In the formula, R ₁₁ represents an alkyl group, an alkoxy group or a halogen atom. R ₁₂ and R ₁₃ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group or a substituted amino group.

  Examples of large molecular weight charge transport materials include amine compounds represented by general formula [IV].

In the formula, Ar ₁₁ represents a substituted or unsubstituted aromatic group, Ar ₁₂ represents a divalent substituted, unsubstituted aromatic group, divalent heterocyclic group, or the following general formula [IV2], and R ₂₀ represents A substituted, unsubstituted alkyl group, monovalent substituted, or unsubstituted aromatic group is represented. However, the plurality of Ar ₁₁ , Ar ₁₂ , and R ₂₀ may be different from each other. n represents an integer.

In the formula, Y is an oxygen atom, a sulfur atom, —CH═CH—, or —CH ₂ —CH ₂ —. However, R < ₂₁ >, R < ₂₂ > is a hydrogen atom or a C1-C4 alkyl group. The chemical structures of typical compounds of the general formula [IV] are listed below. A mixture of compounds having different numbers n of chain structures in each of the following chemical structures may be used as the charge transport material.

  Examples of the high molecular weight charge transport material include resins represented by general formulas [V], [VI], general formulas [VII1] to [VII3], and compounds [VIII1] to [VIII8]. , Poly-N-vinylcarbazole, polysilylene polymer and the like. In particular, among the compounds represented by the general formula [V], the compound [V1] is suitable because the molecule has a self-organizing function and causes effective placement of the participation inhibitor in the layer. Furthermore, the resin represented by the general formula [V] is preferable in that it has a low conversion efficiency due to non-uniform leakage and has a stable conversion efficiency over a long period of time.

  In the formula, R represents a substituted or unsubstituted hydrocarbon group, and n11 represents the number of repeating units.

  In the formula, R ′, R ″ and R ′ ″ represent hydrogen, a lower alkyl group, a lower alkoxy group and a halogen.

  Specific examples of the stilbene group-containing monomer unit represented by the general formula [VI] include the following monomer units.

In the general formulas [VII1] to [VII3], R ₃₁ , R ₃₂ , R ₃₃ , R ₃₄ and R ₃₅ each represent an alkyl group or an alkoxy group, n1 and n3 each represent an integer of 1 to 5, n2, n4 and n5 each represent an integer of 1 to 4. L, m, and p each represent a number that is greater than 0 and less than or equal to 1. Specific examples of the polymer compounds represented by the general formulas [VII1] to [VII3] are shown below.

  In the present invention, as a structure having high conversion efficiency and high durability, the molecular weight or average molecular weight of the charge transport material is preferably 750 to 100,000, more preferably 1,000 to 50,000. The reason for this is that the charge movement site is fast and it is difficult to form charge trap sites that cause a reduction in efficiency in the middle of the layer.

  Binder resins that can be used for the charge transport layer include polycarbonate (bisphenol A type, bisphenol Z type), polyester, methanol resin, acrylic resin, vinyl chloride, polystyrene, phenol resin, epoxy resin, polyurethane, polyvinylidene chloride, alkyd. Resin, silicone resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, polyacrylate, polyacrylamide, phenoxy resin, and the like are used. These binders can be used alone or as a mixture of two or more, and the amount used is suitably about 0 to 30 parts by mass with respect to 100 parts by mass of the charge transport material.

  The thickness of the charge transport layer of the present application is preferably 0.1 to 20 μm.

  A feature of the photoelectric conversion element of the present application is that the charge transport layer contains an acid additive. Examples of the antioxidant that can be used in the charge transport layer include the following compounds.

(1) Radical chain inhibitor Phenol antioxidant (hindered phenol)
Amine-based antioxidants (hindered amines, diallyldiamines, diallylamines)
Hydroquinone antioxidant (2) Peroxide decomposer Sulfur antioxidant (thioethers)
Phosphoric acid antioxidants (phosphites)
Among the above antioxidants, the radical chain inhibitor (1) is good, and a hindered phenol-based or hindered amine-based antioxidant is particularly preferable. Two or more types may be used in combination, for example, a combination of (1) a hindered phenol antioxidant and (2) a thioether antioxidant. Furthermore, the above-mentioned structural unit, for example, a hindered phenol structural unit and a hindered amine structural unit may be included in the molecule.

  The content of the hindered phenol-based or hindered amine-based antioxidant is preferably 0.01 to 20% by mass with respect to the mass of the charge transport layer. When the content is less than 0.01% by mass, the conversion efficiency is significantly reduced due to durability. When the content is more than 20% by mass, the photoelectric conversion efficiency is decreased from the beginning, and the subsequent conversion efficiency is also decreased.

  Here, hindered phenol refers to compounds having a branched alkyl group at the ortho position relative to the hydroxyl group of the phenol compound and derivatives thereof (however, the hydroxyl group may be converted to alkoxy).

  The hindered amine system is a compound having a bulky organic group near the N atom. The bulky organic group includes a branched alkyl group, for example, a t-butyl group is preferable.

  Examples of the antioxidant having a hindered phenol partial structure are listed below, but the present invention is not limited thereto.

  Examples of the antioxidant having a hindered amine partial structure are listed below, but the present invention is not limited thereto.

  As an organic phosphorus compound, it is a compound represented, for example by general formula: RO-P (OR) -OR. Here, R represents a hydrogen atom, each substituted or unsubstituted alkyl group, alkenyl group or aryl group.

  The organic sulfur compound is, for example, a compound represented by the general formula: R—S—R. Here, R represents a hydrogen atom, each substituted or unsubstituted alkyl group, alkenyl group or aryl group.

  Further, as the antioxidants that have been commercialized, the following compounds, for example, “Irganox 1076”, “Irganox 1010”, “Irganox 1098”, “Irganox 245”, “Irganox” as hindered phenols, are used. Knox 1330 "," Irganox 3114 "," Irganox 1076 "," 3,5-di-t-butyl-4-hydroxybiphenyl ", hindered amine series" Sanol LS2626 "," Sanol LS765 "," Sanol LS770 " , “Sanol LS744”, “Tinuvin 144”, “Tinuvin 622LD”, “Mark LA57”, “Mark LA67”, “Mark LA62”, “Mark LA68”, “Mark LA63”, and “Sumilyzer TPS” , "Sumi Iser TP-D ", and the phosphite system is" Mark 2112 "," Mark PEP-8 "," Mark PEP-24G "," Mark PEP-36 "," Mark 329K "," Mark HP-10 " Is mentioned.

  In addition, if necessary, an appropriate amount of a low-molecular compound such as a plasticizer and an ultraviolet absorber and a leveling agent can be added to the charge transport layer.

  A method for manufacturing a semiconductor for a photoelectric conversion material of the present invention will be described.

  As one embodiment of the semiconductor for a photoelectric conversion material of the present invention, a method such as forming the above semiconductor for a photoelectric conversion material on a conductive support by firing is exemplified.

  When the semiconductor for a photoelectric conversion material of the present invention is produced by firing, the semiconductor is sensitized (adsorption, penetration into a porous layer, etc.) with the above-described compound or sensitizing dye after firing. It is preferable to do. It is particularly preferable to perform the compound adsorption treatment quickly after the firing and before the water is adsorbed to the semiconductor.

  When the semiconductor for photoelectric conversion materials of the present invention is in the form of particles, the semiconductor electrode is preferably prepared by applying or spraying the semiconductor for photoelectric conversion materials onto a conductive support. Moreover, when the semiconductor for photoelectric conversion materials of this invention is a film | membrane form, Comprising: It is not hold | maintained on an electroconductive support body, the semiconductor electrode for photoelectric conversion materials is bonded on an electroconductive support body, and a semiconductor electrode is attached. It is preferable to produce it.

  Hereinafter, a process for producing a semiconductor for a photoelectric conversion material of the present invention will be specifically described.

  First, a coating solution containing fine semiconductor powder is prepared. The semiconductor fine powder preferably has a finer primary particle diameter, and the primary particle diameter is preferably 1 nm to 5000 nm, and more preferably 2 nm to 50 nm. The coating liquid containing the semiconductor fine powder can be prepared by dispersing the semiconductor fine powder in a solvent. The semiconductor fine powder dispersed in the solvent is dispersed in the form of primary particles. The solvent is not particularly limited as long as it can disperse the semiconductor fine powder.

  Examples of the solvent include water, an organic solvent, and a mixed solution of water and an organic solvent. As the organic solvent, alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone, acetone and acetyl acetone, hydrocarbons such as hexane and cyclohexane, and the like are used. A surfactant and a viscosity modifier (polyhydric alcohol such as polyethylene glycol) can be added to the coating solution as necessary. The range of the semiconductor fine powder concentration in the solvent is preferably 0.1% by mass to 70% by mass, and more preferably 0.1% by mass to 30% by mass.

  The semiconductor fine powder-containing coating solution obtained as described above is applied or sprayed onto a conductive support, dried, etc., and then baked in air or in an inert gas, on the conductive support. A semiconductor layer (semiconductor film) is formed.

  Examples of the method for applying the semiconductor fine powder-containing coating solution include roller coating, spin coating, and dipping.

  The film obtained by applying and drying the coating liquid on the conductive support is composed of an aggregate of semiconductor fine particles, and the particle size of the fine particles corresponds to the primary particle size of the semiconductor fine powder used. is there.

  The semiconductor fine particle aggregate film formed on the substrate such as the conductive support in this way has a low bonding strength with the conductive support and a bonding strength between the fine particles and a low mechanical strength. Therefore, preferably, the semiconductor fine particle aggregate film is fired to increase the mechanical strength, thereby obtaining a fired product film strongly fixed to the conductive support.

  In the present invention, the fired product film may have any structure, but is preferably a porous structure film (also referred to as a porous layer having voids).

  Here, the porosity of the semiconductor thin film according to the present invention is preferably 10% by volume or less, more preferably 8% by volume or less, and particularly preferably 0.01% by volume to 5% by volume. The porosity of the semiconductor thin film means a porosity that is penetrable in the thickness direction of the dielectric, and can be measured using a commercially available apparatus such as a mercury porosimeter (Shimadzu Polarizer 9220 type).

  The film thickness of the semiconductor layer that is a fired product film having a porous structure is preferably at least 10 nm or more, more preferably 100 nm to 10,000 nm.

  From the viewpoint of appropriately adjusting the actual surface area of the fired product film during the firing treatment and obtaining a fired product film having the above porosity, the firing temperature is preferably lower than 1000 ° C, more preferably 200 ° C to 800 ° C. It is the range of 300 degreeC, Most preferably, it is the range of 300 to 800 degreeC.

  Further, the ratio of the actual surface area to the apparent surface area can be controlled by the particle diameter and specific surface area of the semiconductor fine particles, the firing temperature, and the like. In addition, after heat treatment, for example, chemical plating or aqueous trichloride using a titanium tetrachloride aqueous solution is used to increase the surface area of the semiconductor particles, increase the purity in the vicinity of the semiconductor particles, and increase the efficiency of electron injection from the dye into the semiconductor particles. Electrochemical plating using a titanium aqueous solution may be performed.

  As described above, the semiconductor sensitization treatment is performed by dissolving the dye in an appropriate solvent and immersing the conductive support obtained by firing the semiconductor in the solution. In that case, a conductive support formed by firing a semiconductor layer (also referred to as a semiconductor film) is preliminarily subjected to reduced pressure treatment or heat treatment to remove bubbles in the film, and the dye is formed in the semiconductor layer (semiconductor film). ) It is preferable to be able to enter deep inside, and it is particularly preferable when the semiconductor layer (semiconductor film) is a porous structure film.

  The time for immersing the conductive support obtained by baking the semiconductor in the solution containing the dye is such that the compound penetrates deeply into the semiconductor layer (semiconductor film) to sufficiently advance adsorption and the like, and the semiconductor is sufficiently sensitized, and From the viewpoint of suppressing the decomposition product generated by decomposition of the compound in the solution from interfering with the adsorption of the compound, it is preferably 3 hours to 48 hours under the condition of 25 ° C., more preferably 4 hours to 24 hours. This effect is particularly remarkable when the semiconductor film is a porous structure film. However, the immersion time is a value under the condition of 25 ° C., and is not limited to the above when the temperature condition is changed.

  In soaking, the solution containing the dye may be heated to a temperature that does not boil as long as the dye does not decompose. A preferable temperature range is 10 ° C to 100 ° C, and more preferably 25 ° C to 80 ° C. However, as described above, this is not the case when the solvent boils in the temperature range.

  After the immersion of the conductive support of the dye is completed, drying is performed. Although there is no restriction | limiting in particular in drying temperature, It is preferable to carry out between room temperature and 100 degreeC, and it is more preferable to carry out at around 50 degreeC.

  In the present invention, a blocking layer may be provided before forming the semiconductor layer. As the blocking layer, it is preferable to select the material of the blocking layer and the subsequent firing temperature so that the semiconductor layer is not easily decomposed or deteriorated during the subsequent formation of the semiconductor layer.

  The photoelectric conversion element of the present invention is provided with a semiconductor layer (a dye-sensitized semiconductor electrode) adsorbing the above-described dye on a conductive support, and a charge containing a charge transport material and an antioxidant on the layer. A moving layer is provided. A counter electrode is provided on the charge transport layer.

  The support used for the photoelectric conversion element of the present invention and the solar cell of the present invention has a structure in which a conductive material is provided on a conductive material such as a metal plate or a non-conductive material such as a glass plate or a plastic film. Can be used. Examples of materials used for the conductive support include metal (for example, platinum, gold, silver, copper, aluminum, rhodium, indium) or conductive metal oxide (for example, indium-tin composite oxide, tin oxide doped with fluorine) And carbon). The thickness of the conductive support is not particularly limited, but is preferably 0.3 mm to 5 mm.

The conductive support is preferably substantially transparent, and substantially transparent means that the light transmittance is 10% or more, more preferably 50% or more, and 80 % Or more is most preferable. In order to obtain a transparent conductive support, it is preferable to provide a conductive layer made of a conductive metal oxide on the surface of a glass plate or a plastic film. Transparent plastic film materials include tetraacetylcellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polyester (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate. (PAr), polysulfone (PSF), polyester sulfone (PES), polyetherimide (PEI), cyclic polyolefin, brominated phenoxy and the like. In order to ensure sufficient transparency, the coating amount of the conductive metal oxide is preferably 0.01 to 100 g per 1 m ² of glass or plastic support. When a transparent conductive support is used, light is preferably incident from the support side.

The conductive support preferably has a surface resistance of 50 Ω / cm ² or less, and more preferably 10 Ω / cm ² or less.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

Example 1
Production of photoelectric conversion element A dispersion of titanium oxide (P-25; manufactured by Nippon Aerosil Co., Ltd.) was applied to the conductive surface side of transparent conductive glass (surface resistance 10 Ω / □) coated with fluorine-doped tin dioxide, and room temperature was applied. After drying for 30 minutes, firing was performed at 450 ° C. for 60 minutes to produce an electrode having a thickness of about 10 μm. After this electrode was cooled, it was refluxed for 30 minutes in an ethanol solution of eosin Y dye (3 × 10 ⁻⁴ mol / dm ³ ) to adsorb the dye.

  Next, according to Table 1, CTM (4 parts of the compounds shown in Table 1), antioxidant (described in Table 1) as the charge transport layer, bisphenol Z-type polycarbonate (1 part) or no additive as the binder (described in Table 1) ), A solution obtained by dissolving titanium tetraisopropoxide (1 part) in dichloromethane (100 parts) was applied so that the film thickness after drying was 2 μm, and then dried at 100 ° C. for 60 minutes. 1-16 were obtained.

  Next, the change sample of the molecular weight of CTM-4-1 to CTM-4-4 was synthesized as follows.

  (1) In a 200 ml flask, 10.0 g of NN′-bis (3,4-dimethylphenyl) -3,3′-dimethylbiphenyl-4,4′diamine, 4-ethoxycarbonylethyl-4′-iodophenyl 24.0 g, 11 g of potassium carbonate, 1.0 g of copper sulfate pentahydrate and 30 ml of n-tridecane were added, and this was reacted at 230 ° C. for 1 hour under a nitrogen stream. After the completion of the reaction, the reaction mixture was cooled to room temperature and dissolved in 10 ml of toluene, the insoluble matter was filtered, and the obtained filtrate was purified by silica gel column chromatography using toluene. This gave 15.2 g of oily NN′-bis (3,4-dimethylphenyl) -N—N′-bis-4-ethoxycarbonylethylphenyl- [1-1′-biphenyl] -4,4′diamine. Got. Next, 10 g of the obtained diamine having an ester group is placed in a 100 ml flask, and a solution obtained by dissolving 2 g of potassium hydroxide in 50 ml of ethylene glycol is added thereto, and the reaction is heated at 150 ° C. for 1 hour in a nitrogen stream. did. After the completion of this reaction, the reaction product liquid is cooled to room temperature, hydrochloric acid is added until it becomes acidic, the formed precipitate is filtered, washed thoroughly with distilled water, and dried to give CTM-4. As a precursor, 8.1 g of charge transporting compound 4 ′ having two carboxyl groups was obtained.

  (2) Next, Compound 4 'was dissolved in 7 g, 1 g of ethylene glycol, 10 g of toluene, and 30 g of isopropanol, 0.5 g of sulfuric acid was added as a catalyst, and the reaction was performed at 80 ° C. for 60 minutes while replacing the solvent with nitrogen. Thereafter, the reaction solution was opened in hexane and then washed twice with methanol to obtain CTM-4-2. When the molecular weight of this CTM-4-2 was determined, the number average molecular weight was 20000 (in terms of styrene). Similarly, CTM-4-3 was obtained with a reaction time of 120 minutes. The number average molecular weight was 50000 (in terms of styrene). Furthermore, reaction temperature was raised to 90 degreeC and reaction time was made to react for 120 minutes and CTM-4-4 was obtained. The number average molecular weight was 120,000. Next, the reaction temperature was lowered to 70 ° C. and reacted for 45 minutes to obtain CTM-4-1. The number average molecular weight was 5000 (in terms of styrene). Using the above CTM-4-1 to 4-4, the sample No. 17-21 were produced.

CTM-5 was synthesized by adding 0.3472 g of 2,5-dibromo-3-hexylthiophene and 0.0447 g of naphthalene as an internal standard substance to a container which had been dried and then replaced with argon, and substituted with argon once again. Under a stream of N ₂ , 5 ml of dry THF was added using a dried syringe and cooled to 0 ° C. Under a stream of N ₂ , 0.53 ml (1.1 mmol, 1.0 eq) was added using a syringe dried with isopropylmagnesium chloride-THF solution (2.0 mol / l), and the mixture was stirred at 0 ° C. for 30 minutes. Another container was then dried and replaced with argon. To this, 0.0030 g (0.006 mmol: 0.50 mol% with respect to the monomer) of 1,3-bisdiphenylphosphinopropane nickel chloride (II) and an appropriate amount of distilled toluene were added and azeotroped under reduced pressure. -Nickel (II) chloride of bisdiphenylphosphinopropane was dried. Thereto, 3 ml of dry THF was added under a stream of N ₂ using a dried syringe, and this was added to a thiophene solution monometallic with Grignard reagent and stirred at room temperature (about 20 ° C.) for 10 hours. Sampling of the reaction solution was performed using a dried syringe under a N ₂ stream. After completion of the reaction, water was added, followed by extraction with chloroform. The organic phase was washed with water and then dried over anhydrous magnesium sulfate. After evaporating the solvent under reduced pressure, a black solid was obtained. The number average molecular weight was 45,000 (in terms of styrene). Using the obtained CTM-5, sample No. 22 was produced.

  A photoelectric conversion element as a counter electrode using a transparent conductive glass plate (FTO) in which a tin oxide doped with fluorine is coated on the charge transport layer and a conductive agent supporting platinum is coated on the glass surface. 1-22 were produced.

Photoelectric conversion element 23
Sample No. A photoelectric conversion element 23 was produced in the same manner as the photoelectric conversion element 2 except that the blocking layer was formed with a coating liquid having the following constitution before applying the transparent conductive glass and titanium oxide dispersion liquid used in 2.

Coating solution Ethyl silicate oligomer (Silicate 40, manufactured by Tama Chemical Industry Co., Ltd.)
100 parts by mass Tetraethoxysilane 50 parts by mass Ion-exchanged water 20 parts by mass The above coating solution was applied by a spin coater at 1000 rpm, and primary dried at 150 ° C. for 20 minutes. At this time, the thickness of the blocking layer was 0.2 μm.

Production of Solar Cell After the side surfaces of the photoelectric conversion elements 1 to 23 were encapsulated with resin, lead wires were attached to produce 3 lots of the solar cells 1 to 23 of the present invention.

Evaluation of photoelectric conversion efficiency of solar cell Each of the solar cells 1 to 23 obtained above was irradiated with light having an intensity of 100 mW / m ² by a solar simulator (manufactured by JASCO (JASCO), low energy spectral sensitivity measuring device CEP-25). Table 1 shows the photoelectric conversion efficiency when irradiated. The indicated value was the average value of the measurement results for three solar cells having the same configuration and production method.

Evaluation of photoelectric conversion efficiency (energy conversion efficiency) About the above-mentioned solar cells 1-23, it tested so that each photoelectric conversion efficiency (energy conversion efficiency (eta)) might be evaluated. This evaluation test was conducted using a solar simulator (trade name: “WXS-85-H type” manufactured by Wacom Denso Co., Ltd.) and 100 mW / cm ² from a xenon lamp that passed through an AM filter (AM-1.5). The following procedure was performed by irradiating simulated sunlight.

  For each solar cell immediately after completion, the current-voltage characteristics were measured at room temperature using an IV tester, and the short circuit current (Jsc), the open circuit voltage (Voc), and the fill factor (FF) were obtained. From these, the photoelectric conversion efficiency (η (%)) was determined. In addition, the photoelectric conversion efficiency ((eta) (%)) of the solar cell was computed based on the following formula (A).

η = 100 × (Voc × Jsc × FF) / P (A)
Here, P is the incident light intensity [mW / cm ⁻² ], Voc is the open circuit voltage [V], Jsc is the short-circuit current density [mA · cm ⁻² ], F.V. F. Indicates a fill factor. Table 1 shows the photoelectric conversion efficiency results thus obtained.

Durability Evaluation Table 1 shows the rate of decrease after 100 hours of light irradiation with a solar simulator at 100 mW / m ² .

  From Table 1, it can be seen that the solar cell of the present invention exhibits high photoelectric conversion characteristics, no reduction in photoelectric conversion efficiency is observed, and excellent stability.

It is the schematic showing the basic composition of the photoelectric conversion element of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Counter electrode 2 Charge transport layer 3 Semiconductor electrode 4 Conductive support body

Claims (10)

A photoelectric conversion device having a dye-sensitized semiconductor electrode, a charge transport layer, and a counter electrode on a conductive support, wherein the charge transport layer contains a charge transport material and an antioxidant. element. The photoelectric conversion device according to claim 1, wherein the antioxidant is a hindered amine compound or a hindered phenol compound. 3. The photoelectric conversion element according to claim 1, wherein the content of the antioxidant is 0.01 to 20% by mass with respect to the mass of the charge transport layer. The photoelectric conversion element according to claim 1, wherein the charge transport layer contains a charge transport material having a molecular weight of 750 to 100,000. The photoelectric conversion element according to any one of claims 1 to 4, wherein the charge transport layer contains a polymer charge transport material and an antioxidant and does not contain a binder resin. The photoelectric conversion element according to claim 5, wherein the polymer charge transport material is a conductive polymer. The photoelectric conversion according to any one of claims 1 to 6, further comprising a blocking layer made of an insulator layer or a semiconductor between the conductive support and the dye-sensitized semiconductor electrode. element. The film thickness of the said semiconductor electrode is 100-10000 nm, The photoelectric conversion element of any one of Claims 1-7 characterized by the above-mentioned. The photoelectric conversion element according to claim 1, wherein the charge transport layer has a thickness of 0.1 to 20 μm. It comprised using the photoelectric conversion element of any one of Claims 1-9, The dye-sensitized solar cell characterized by the above-mentioned.

Images