JP5194893B2 - Dye-sensitized photoelectric conversion element and solar cell - Google Patents

Description

  The present invention relates to a dye-sensitized photoelectric conversion element and a solar cell using the same.

  Since 1991, when Prof. Gretzel announced that a new dye-sensitized solar cell using a ruthenium complex as a sensitizing dye has a conversion efficiency of 10% (see Non-Patent Document 1), It is attracting attention as a generational power source. Since ruthenium complexes have absorption in the long wavelength region, light of a wide range of wavelengths can be taken in. Therefore, it is considered that high conversion efficiency has been achieved.

  However, since ruthenium is a rare metal, it is an expensive substance. In addition, improvement of the form factor is essential for improving the conversion efficiency of the dye-sensitized photoelectric conversion element. Therefore, the present inventors use a nonmetallic organic sensitizing dye that can be synthesized easily and inexpensively, and use a solution in which a plurality of sensitizing dyes are dissolved when the sensitizing dye is adsorbed on the semiconductor layer. It was considered that an improvement in the shape factor can be obtained by densely adsorbing the sensitizing dye on the semiconductor layer.

However, the performance of the dye-sensitized solar cell is greatly affected by the conduction band level of the semiconductor layer, the LUMO and HOMO levels of the sensitizing dye molecule, and the redox level of the electrolyte, and a plurality of sensitizing dye molecules should be used. In this case, there are a plurality of LUMO and HOMO levels, and there is a problem that the transfer of electrons is complicated and the movement of electrons does not proceed smoothly and the efficiency of the battery is lowered.
B. O'Regan and M.M. Gratzel, Nature, 353, 737 (1991)

  The present invention has been made in view of the above problems, and an object thereof is to provide a dye-sensitized photoelectric conversion element having a high conversion efficiency using an inexpensive sensitizing dye and a solar cell using the dye-sensitized photoelectric conversion element. Is to provide.

  The above object of the present invention is achieved by the following configurations.

1. In the dye-sensitized photoelectric conversion element in which a dye-carrying semiconductor electrode in which a plurality of dyes are carried on an oxide semiconductor on a conductive support and a counter electrode are arranged to face each other with a charge transfer layer interposed therebetween, The dye has two kinds of dyes represented by the following general formulas (1) and (4), or general formulas (2) and (5), or general formulas (3) and (6), and A dye-sensitized photoelectric conversion element characterized in that a difference in molecular length (| L ₁ −L ₂ |) between two kinds of dyes is in accordance with the following formula (X).

(In General Formula (1) and General Formula (4), Ar ₁ represents an aryl group and may have a substituent. R ₁ and R ₂ are a hydrogen atom, a halogen atom, an alkyl group, an amino group, Represents an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group, and heterocyclic group may have a substituent, and R ₃ and R ₁₀ are a single bond, an alkylene group, an arylene group, or a divalent group. And an alkylene group, an arylene group or a divalent heterocyclic group may have a substituent, and X ₁ and X ₇ each represents an acidic group, R ₁ , R ₂ and Ar ₁ may be linked to form a ring.
In general formulas (2) and (5), Ar ₂ and Ar ₃ each represents an aryl group and may have a substituent. R ₄ represents a hydrogen atom, a halogen atom, an alkyl group, an amino group, an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group and heterocyclic group may have a substituent. R ₅ , R ₆ , R ₁₁ , and R _{12 each} represents a single bond, an alkylene group, an arylene group, or a divalent heterocyclic group, or a linking group thereof. The alkylene group, the arylene group, or the divalent heterocyclic group is It may have a substituent. X ₂ , X ₃ , X ₈ and X ₉ represent an acidic group. R ₄ , Ar ₂ and Ar ₃ may be connected to form a ring.
In general formulas (3) and (6), Ar ₄ , Ar ₅ , and Ar ₆ represent an aryl group and may have a substituent. R ₇ , R ₈ , R ₉ , R ₁₃ , R ₁₄ and R _{15 each} represents a single bond, an alkylene group, an arylene group or a divalent heterocyclic group, an alkylene group, an arylene group or a divalent heterocyclic group; Alternatively, these bonding groups may have a substituent. Ar ₄ , Ar ₅ and Ar ₆ may be linked to form a ring. X ₄ , X ₅ , X ₆ , X ₁₀ , X ₁₁ and X ₁₂ each represents an acidic group. )
Formula (X) 0.1 ≦ | L ₁ −L ₂ | ≦ 2.2 (nm)
(Wherein, L ₁ is the general formula (1) to (represents the molecular length of the dyes represented by 3), L ₂ represents a general formula (4) the molecular length of the dye represented by - (6). The molecular lengths L ₁ and L ₂ are the central nitrogen atom in the structure optimized for the longest molecular length when the compound is drawn with ChemDraw Ultra Ver. 9.0.1 manufactured by Hybrid Soft. To the atom to which the acidic group is bonded (nm).
2. In the dye-sensitized photoelectric conversion element in which a dye-carrying semiconductor electrode in which a plurality of dyes are carried on an oxide semiconductor on a conductive support and a counter electrode are arranged to face each other with a charge transfer layer interposed therebetween, The dye has two kinds of dyes represented by the following general formulas (7) and (10), or general formulas (8) and (11), or general formulas (9) and (12), and A dye-sensitized photoelectric conversion element characterized in that a difference in molecular length (| L ₁ −L ₂ |) between two kinds of dyes is in accordance with the following formula (X).

(In the general formula (7) and the general formula (10), Ar ₂₁ , Ar ₂₂ and Ar ₂₃ each represent a divalent aryl group and may have a substituent. R ₂₁ and R ₂₃ represent a hydrogen atom, Represents a halogen atom, an alkyl group, an amino group, an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group and heterocyclic group may have a substituent, R ₂₂ and R ₃₀ are a single bond, Represents an alkylene group, an arylene group, or a divalent heterocyclic group, or a bonding group thereof, and the alkylene group, the arylene group, or the divalent heterocyclic group may have a substituent, X ₂₁ , X ₂₇ Represents an acidic group, and Ar ₂₁ , Ar ₂₂ and Ar ₂₃ may be linked to form a ring.
In General Formula (8) and General Formula (11), Ar ₂₄ , Ar ₂₅ and Ar ₂₆ represent an aryl group and may have a substituent. R ₂₄ represents a hydrogen atom, a halogen atom, an alkyl group, an amino group, an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group or heterocyclic group may have a substituent. R ₂₅ , R ₂₆ , R ₃₁ and R _{32 each} represents a single bond, an alkylene group, an arylene group, or a divalent heterocyclic group, or a linking group thereof, and the alkylene group, the arylene group, or the divalent heterocyclic group is It may have a substituent. X ₂₂ , X ₂₃ , X ₂₈ and X ₂₉ each represents an acidic group. Ar ₂₄ , Ar ₂₅ and Ar ₂₆ may be linked to form a ring.
In General Formula (9) and General Formula (12), Ar ₂₇ , Ar ₂₈ , and Ar ₂₉ each represent an aryl group and may have a substituent. R ₂₇ , R ₂₈ , R ₂₉ , R ₃₃ , R ₃₄ , and R _{35 each} represents a single bond, an alkylene group, an arylene group, or a divalent heterocyclic group, or a linking group thereof. An alkylene group, an arylene group, or 2 The valent heterocyclic group may have a substituent. Ar ₂₇ , Ar ₂₈ and Ar ₂₉ may be linked to form a ring. X ₂₄ , X ₂₅ , X ₂₆ , X ₃₀ , X ₃₁ and X ₃₂ represent an acidic group. )
Formula (X) 0.1 ≦ | L ₁ −L ₂ | ≦ 2.2 (nm)
(In the formula, L ₁ represents the molecular length of the dye represented by the general formulas (7) to (9), and L ₂ represents the molecular length of the dye represented by the general formulas (10) to (12). The molecular lengths L ₁ and L ₂ are the central nitrogen atom in the structure optimized for the longest molecular length when the compound is drawn with ChemDraw Ultra Ver. 9.0.1 manufactured by Hybrid Soft. To the atom to which the acidic group is bonded (nm).
3. 3. A solar cell using the dye-sensitized photoelectric conversion element as described in 1 or 2 above.

  According to the present invention, it is possible to provide a dye-sensitized photoelectric conversion element having a high conversion efficiency using an inexpensive sensitizing dye and a solar cell using the dye-sensitized photoelectric conversion element.

  In the development of dye-sensitized solar cells, in order to obtain high conversion efficiency, when dyes are co-attached to a semiconductor layer, aggregation of deoxycholic acid and the like is prevented so that association between the dyes is prevented and electron injection is efficient. It was known to introduce an inhibitor. On the contrary, in order to develop the agglomeration with good characteristics, a plurality of dyes are adsorbed to form a unique agglomerated structure and improve the battery characteristics. However, depending on the combination of dyes, the efficiency is reduced due to the mismatch of the energy levels.

Therefore, the present inventors co-adsorbed two or more types of sensitizing dye molecules having different structures and different molecular sizes, thereby developing an aggregate structure and improving conversion efficiency without causing potential mismatch. We investigated whether there was a dye-sensitized photoelectric conversion element that also contributed to the above. As a result, in a dye-sensitized photoelectric conversion element in which a dye-carrying semiconductor electrode in which a plurality of dyes are carried on an oxide semiconductor on a conductive support and a counter electrode are arranged to face each other via a charge transfer layer, The plurality of dyes have a specific similar structure represented by the general formulas (1) to (6), and a difference in molecular length (| L ₁ −L ₂ |) between two kinds of dyes to be combined is 0. It has been found that a dye-sensitized photoelectric conversion element with high conversion efficiency can be obtained by setting the thickness to 1 to 2.2 nm, and the present invention has been achieved.

  Hereinafter, the present invention will be described in more detail.

  The dye-sensitized photoelectric conversion element of the present invention (hereinafter also simply referred to as a photoelectric conversion element) will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of the photoelectric conversion element of the present invention.

  As shown in FIG. 1, it is comprised from the board | substrates 1, 1 ', the transparent conductive films 2 and 7, the oxide semiconductor 3, the pigment | dye 4, the electrolyte 5, and the partition 9.

  In the present invention, an oxide semiconductor layer having pores formed by sintering particles of an oxide semiconductor 3 on a substrate 1 (also referred to as a conductive support) provided with a transparent conductive film 2 is provided. A dye-carrying semiconductor electrode having a dye 4 adsorbed on the surface of the pores is used.

  As the counter electrode 6, a transparent conductive film 7 is formed on a substrate 1 ′ and platinum 8 is vapor-deposited thereon, and an electrolyte 5 (charge transfer layer) is formed by filling an electrolyte 5 between both electrodes. Is done.

In the present invention, dye sensitization in which a dye-carrying semiconductor electrode in which a plurality of dyes 4 are carried on an oxide semiconductor 3 on a conductive support and a counter electrode 6 are arranged to face each other via a charge transfer layer. In the photoelectric conversion element, the plurality of dyes 4 are represented by the general formulas (1) and (4), the general formulas (2) and (5), or the general formulas (3) and (6). It has two kinds of dyes, and the difference in molecular length between the two kinds of dyes (| L ₁ −L ₂ |) is in accordance with the formula (X).

  The reason why a good photoelectric conversion element can be obtained in the present invention is considered as follows. When a dye is adsorbed on an oxide semiconductor, if a single dye is used, the amount of adsorption is limited due to steric repulsion around the central amine where the molecules are sterically crowded, and the dye unadsorbed sites on the oxide semiconductor Occurs. Therefore, if multiple sensitizing dye molecules with different molecular lengths from the central nitrogen atom to the adsorbing group (acidic group) are used, molecules of different lengths coordinate with each other on the oxide semiconductor so as to fill the generated space. Dye can be adsorbed densely. Thereby, the shape factor is improved and the conversion efficiency is also improved.

If the difference in length from the central nitrogen atom to the atom to which the acidic group is bonded | L ₁ −L ₂ | It is thought that the steric repulsion around the central nitrogen atom is alleviated. In addition, when the difference in length | L ₁ −L ₂ | exceeds 2.2 nm, the similarity of the dyes is reduced and a preferable aggregate structure is not formed, and it is considered that the adsorption cannot be uniformly performed on the oxide semiconductor. .

The molecular lengths L ₁ and L ₂ of the two types of dyes were obtained from ChemDraw Ultra Ver. 9. When drawing a compound at 9.0.1, the interatomic distance (nm) from the central nitrogen atom to the atom to which the acidic group is bonded in the structure optimized for the longest molecular length It is. To determine this, ChemDraw Ultra Ver. In 9.0.1, after drawing so that the length from the central nitrogen atom to the atom to which the acidic group is bonded is the longest among the three-dimensional structures that can be taken by the structure of the dye molecule, Chem 3D Pro Ver. 9. The structure is optimized by MM2 calculation of 9.0.1, and the distance from the central nitrogen atom to the atom to which the acidic group is bonded is measured, and is set as L1, L2, L3, and L4. In the dye having a plurality of acidic groups as in the general formulas (2), (3), (5) and (6), the longest distance from the central nitrogen atom to the acidic group is L1, L2, L3. , L4.

<Dye>
In the present invention, two kinds of dyes represented by the general formulas (1) and (4), the general formulas (2) and (5), or the general formulas (3) and (6) are used as the dyes. Use in combination.

In General Formula (1) and General Formula (4), Ar ₁ represents an aryl group and may have a substituent. R ₁ and R ₂ are a hydrogen atom, a halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (eg, methyl group, ethyl group, propyl group, butyl group, octyl group, nonyl group) Etc.), amino group (eg, amino group, methylamino group, ethylamino group, diethylamino group, etc.), aryl group (eg, phenyl group, tolyl group, naphthyl group, etc.) or heterocyclic group (furanyl group, thienyl group, etc.) An imidazolyl group, a thiazolyl group, a morpholyl group, and the like, and the alkyl group, amino group, aryl group, and heterocyclic group may have a substituent. R ₃ and R ₁₀ are a single bond, an alkylene group (eg, methylene group, ethylene group, propylene group, etc.), an arylene group (eg, phenylene group, tolylene group, etc.), or a divalent heterocyclic group (R ₁ , R ₂ represents a divalent group obtained by removing one hydrogen atom from the heterocyclic group described in 2) or a linking group thereof, and the alkylene group, arylene group or divalent heterocyclic group may have a substituent. Good. X ₁ and X _{7 each} represents an acidic group (such as a sulfonic acid group, a phosphoric acid group, or a carboxylic acid group). R ₁ , R ₂ and Ar ₁ may be linked to form a ring.

In the general formulas (2) and (5), Ar ₂ and Ar ₃ each represents an aryl group and may have a substituent. R ₄ represents a hydrogen atom, a halogen atom, an alkyl group, an amino group, an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group and heterocyclic group may have a substituent. R ₅ , R ₆ , R ₁₁ and R _{12 each} represents a single bond, an alkylene group, an arylene group, a divalent heterocyclic group or a linking group thereof, and the alkylene group, arylene group or divalent heterocyclic group is substituted. It may have a group. X ₂ , X ₃ , X ₈ and X ₉ represent an acidic group. R ₄ , Ar ₂ and Ar ₃ may be connected to form a ring. In the general formulas (2) and (5), specific examples of the halogen atom, alkyl group, amino group, aryl group, heterocyclic group, alkylene group, arylene group, divalent heterocyclic group, and acidic group include the general formula It is synonymous with the halogen atom, alkyl group, amino group, aryl group, heterocyclic group, alkylene group, arylene group, divalent heterocyclic group and acidic group mentioned in (1) and general formula (4).

In the general formulas (3) and (6), Ar ₄ , Ar ₅ , and Ar ₆ represent an aryl group and may have a substituent. R ₇ , R ₈ , R ₉ , R ₁₃ , R ₁₄ , and R _{15 each} represents a single bond, an alkylene group, an arylene group, a divalent heterocyclic group, or a bonding group thereof, and represents an alkylene group, an arylene group, or a divalent group. The heterocyclic group may have a substituent. Ar ₄ , Ar ₅ and Ar ₆ may be linked to form a ring. X ₄ , X ₅ , X ₆ , X ₁₀ , X ₁₁ and X ₁₂ each represents an acidic group. In the general formulas (3) and (6), specific examples of the halogen atom, alkyl group, amino group, aryl group, heterocyclic group, alkylene group, arylene group, divalent heterocyclic group and acidic group include the general formula It is synonymous with the halogen atom, alkyl group, amino group, aryl group, heterocyclic group, alkylene group, arylene group, divalent heterocyclic group and acidic group mentioned in (1) and general formula (4).

In the general formula (7) to the general formula (12), Ar _{21 to} Ar ₂₉ (represents Ar ₂₁ , Ar ₂₂ , Ar ₂₃ , Ar ₂₄ , Ar ₂₅ , Ar ₂₆ , Ar ₂₇ , Ar ₂₈ , Ar ₂₉ ) are arylene. Represents a group and may have a substituent. R ₂₁ and R ₂₃ R ₂₄ are a hydrogen atom, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (for example, a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, Nonyl group etc.), amino group (eg amino group, methylamino group, ethylamino group, diethylamino group etc.), aryl group (eg phenyl group, tolyl group, naphthyl group etc.) or heterocyclic group (furanyl group, thienyl etc.) Group, imidazolyl group, thiazolyl group, morpholyl group, etc.), and the alkyl group, amino group, aryl group, and heterocyclic group may have a substituent. R ₂₂ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₃₀ , R ₃₁ , R ₃₂ , R ₃₃ , R ₃₄ , R ₃₅ are a single bond, an alkylene group (for example, a methylene group, an ethylene group, a propylene group, etc.) ), An arylene group (for example, a phenylene group, a tolylene group, etc.), a divalent heterocyclic group (a divalent group in which one hydrogen atom has been removed from the heterocyclic group mentioned for R ₁ or R ₂ ), or the like An alkylene group, an arylene group or a divalent heterocyclic group may have a substituent. X ₂₁ , X ₂₂ , X ₂₃ , X ₂₄ , X ₂₅ , X ₂₆ , X ₂₇ , X ₂₈ , X ₂₉ , X ₃₀ , X ₃₁ , X ₃₂ are acidic groups (sulfonic acid group, phosphoric acid group, carboxylic acid group) Etc.).

Ar ₂₁ , Ar ₂₂ , Ar ₂₃ , R ₂₁ , R ₂₃ in the general formulas (7) and (10) may be linked to form a ring. Ar ₂₄ , Ar ₂₅ , Ar ₂₆ , R ₂₄ , R ₂₅ and R ₂₆ in the general formulas (8) and (11) may be linked to form a ring. Ar ₂₇ , Ar ₂₈ , Ar ₂₉ , R ₂₄ , R ₂₇ , R ₂₈ , R ₂₉ in the general formulas (9) and (12) may be linked to form a ring.

Examples of the acidic group include carboxylic acid (—COOH), phosphonic acid (—PO (OH) ₂ ), and sulfonic acid (—SO ₂ OH).

  Specific examples of the dyes represented by the general formulas (1) to (12) are shown below, but the present invention is not limited to these dyes.

  The dyes represented by the general formulas (1) to (12) of the present invention can be prepared by a general synthesis method. Specific synthesis examples are shown below.

<Synthesis of Dye D-1>
Add 3 equivalents of phosphorus oxychloride and 4 equivalents of N, N'-dimethylformamide to the following triphenylamine compound, heat at 60 ° C for 8 hours under nitrogen atmosphere, add water and stir at 20 ° C for 1 hour. To obtain a formyl body.

  The formyl body was dissolved in acetic acid, 1.2 equivalents of cyanoacetic acid and 2.5 equivalents of ammonium acetate were added, and the mixture was heated to reflux at 120 ° C. for 60 minutes to obtain Dye D-1. The resulting dye D-1 was confirmed in structure by nuclear magnetic resonance spectrum and mass spectrum.

<Synthesis of Dye D-2>
1.05 equivalents of N-bromosuccinimide was added to the DMF solution of the triphenylamine compound, and the mixture was stirred at 20 ° C. for 10 minutes. The reaction solution was extracted with ethyl acetate, washed with water, dried over magnesium sulfate, concentrated to dryness on a rotary evaporator, and treated with a silica column to obtain a bromo compound.

The bromo compound was dissolved in THF, 0.03 equivalents of Pd (PPh ₃ ) ₄ , 1.5 equivalents of thiophene boronic acid, and 1 equivalent of potassium carbonate were added, and the mixture was stirred for 7 hours with heating under reflux. The reaction solution was extracted with ethyl acetate, washed with water, dried over magnesium sulfate, concentrated to dryness on a rotary evaporator, and separated and purified on a silica column to obtain a thiophene.

  Dissolve the thiophene in toluene, add 1.5 equivalents of phosphorus oxychloride and 1.5 equivalents of N, N′-dimethylformamide, heat at 110 ° C. for 5 hours under nitrogen atmosphere, add water and add 20 Stir at 1 ° C. for 1 hour. The reaction solution was extracted with ethyl acetate, washed with water, dried over magnesium sulfate, concentrated to dryness on a rotary evaporator, and separated and purified on a silica column to obtain a formyl form.

  The formyl body was dissolved in acetic acid, 2.5 equivalents of cyanoacetic acid and 2.5 equivalents of ammonium acetate were added, and the mixture was heated to reflux at 120 ° C. for 5 hours to obtain Dye D-2. The resulting dye D-2 was confirmed in structure by nuclear magnetic resonance spectrum and mass spectrum.

<Synthesis of Dye D-7>
Add 6 equivalents of phosphorus oxychloride and 8 equivalents of N, N'-dimethylformamide to the following triphenylamine compound, heat at 60 ° C for 8 hours in a nitrogen atmosphere, add water and stir at 20 ° C for 1 hour. To obtain a diformyl form.

  The diformyl form was dissolved in acetic acid, 2.4 equivalents of cyanoacetic acid and 5 equivalents of ammonium acetate were added, and the mixture was heated to reflux at 120 ° C. for 60 minutes to obtain Dye D-7. The structure of the obtained dye D-7 was confirmed by a nuclear magnetic resonance spectrum and a mass spectrum.

<Synthesis of Dye D-8>
2.1 equivalents of N-bromosuccinimide was added to a DMF solution of a triphenylamine compound, and the mixture was stirred at 20 ° C. for 10 minutes. The reaction solution was extracted with ethyl acetate, washed with water, dried over magnesium sulfate, concentrated to dryness on a rotary evaporator, and treated with a silica column to obtain a dibromo compound.

This dibromo compound was dissolved in THF, 0.12 equivalents of Pd (PPh ₃ ) ₄ , 2.2 equivalents of thiophene boronic acid and 3.0 equivalents of potassium carbonate were added, and the mixture was stirred for 4 hours with heating under reflux. The reaction solution was extracted with ethyl acetate, washed with water, dried over magnesium sulfate, concentrated to dryness on a rotary evaporator, and separated and purified on a silica column to obtain a dithiophene.

  Dissolve the dithiophene in toluene, add 10 equivalents of phosphorus oxychloride and 5 equivalents of N, N′-dimethylformamide, heat at 110 ° C. for 5 hours in a nitrogen atmosphere, then add water for 1 hour at 20 ° C. Stir. The reaction solution was extracted with ethyl acetate, washed with water, dried over magnesium sulfate, concentrated to dryness on a rotary evaporator, and separated and purified on a silica column to obtain a diformyl form.

  The diformyl form was dissolved in acetic acid, 6 equivalents of cyanoacetic acid and 10 equivalents of ammonium acetate were added, and the mixture was heated to reflux at 110 ° C. for 6 hours to obtain Dye D-8. The structure of the obtained dye D-8 was confirmed by a nuclear magnetic resonance spectrum and a mass spectrum.

<Synthesis of Dye D-13>
Add 9 equivalents of phosphorus oxychloride and 12 equivalents of N, N′-dimethylformamide to the following triphenylamine compound, heat at 60 ° C. for 8 hours in a nitrogen atmosphere, add water and stir at 20 ° C. for 1 hour. Thus, a triformyl isomer was obtained.

  The triformyl form was dissolved in acetic acid, 3.6 equivalents of cyanoacetic acid and 7.5 equivalents of ammonium acetate were added, and the mixture was heated to reflux at 120 ° C. for 60 minutes to obtain Dye D-13. The structure of the obtained dye D-13 was confirmed by a nuclear magnetic resonance spectrum and a mass spectrum.

  The dye according to the present invention thus obtained is sensitized by being contained in an oxide semiconductor, and the effects described in the present invention can be achieved. Here, the fact that the oxide semiconductor contains a dye means adsorption to the semiconductor surface, and when the oxide semiconductor has a porous structure such as a porous structure, the oxide semiconductor has a porous structure filled with the dye. Various embodiments are mentioned.

The total content of the dye according to the present invention per 1 m ^{2 of} the semiconductor layer is preferably in the range of 0.01 to 100 mmol, more preferably 0.1 to 50 mmol, particularly preferably 0.5 to 20 mmol. It is.

  When sensitizing treatment is performed using the dye according to the present invention, the dye is used in combination, but other compounds (for example, U.S. Pat. Nos. 4,684,537 and 4,927,721). 5,084,365, 5,350,644, 5,463,057, 5,525,440, JP-A-7-249790, And compounds described in JP-A-2000-150007 and the like.

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

  Further, the conductive support is preferably substantially transparent, and substantially transparent means that the light transmittance is 10% or more, more preferably 50% or more, Most preferably, it is 80% or more. 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. 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.

<< Preparation of dye-supported semiconductor electrode >>
A method for producing a dye-carrying semiconductor electrode according to the present invention will be described.

  When the oxide semiconductor of the dye-carrying semiconductor electrode according to the present invention is in the form of particles, the dye-carrying semiconductor electrode is preferably produced by applying or spraying the oxide semiconductor to a conductive support. Further, when the oxide semiconductor according to the present invention is in a film form and is not held on the conductive support, the oxide semiconductor is bonded onto the conductive support to produce a dye-carrying semiconductor electrode It is preferable to do.

  A preferred embodiment of the dye-carrying semiconductor electrode according to the present invention includes a method of forming the oxide support fine particles on the conductive support by firing.

  When the semiconductor according to the present invention is produced by firing, the semiconductor sensitization (adsorption, filling in a porous layer, etc.) treatment with a dye is preferably performed after firing. It is particularly preferable to perform the compound adsorption treatment quickly after the firing and before the water is adsorbed to the semiconductor.

  Hereinafter, a method for forming a dye-carrying semiconductor electrode, which is preferably used in the present invention, by baking using semiconductor fine powder will be described in detail.

(Preparation of coating liquid containing oxide semiconductor fine powder)
First, a coating liquid containing fine oxide semiconductor powder is prepared. The finer the primary particle diameter of the semiconductor fine powder, the better. The primary particle diameter is preferably 1 to 5000 nm, and more preferably 2 to 50 nm. The coating liquid containing the oxide 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 oxide 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 oxide semiconductor fine powder concentration in the solvent is preferably 0.1 to 70 mass%, more preferably 0.1 to 30 mass%.

(Coating of coating liquid containing oxide semiconductor fine powder and baking of formed semiconductor layer)
The oxide 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 to be conductive. An oxide semiconductor layer (semiconductor film) is formed over the support.

  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.

  Thus, the semiconductor fine particle layer formed on the conductive layer such as the conductive support is weak in bonding strength with the conductive support and fine particles, and has low mechanical strength. The semiconductor fine particle layer is baked to increase the mechanical strength and form a semiconductor layer that is strongly fixed to the substrate.

  In the present invention, the oxide semiconductor layer 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 oxide semiconductor layer according to the present invention is preferably 10% by volume or less, more preferably 8% by volume or less, and particularly preferably 0.01 to 5% by volume. Note that the porosity of the oxide semiconductor layer means a porosity that is penetrable in the thickness direction of the dielectric, and can be measured using a commercially available device such as a mercury porosimeter (Shimadzu porer 9220 type).

  As for the film thickness of the oxide semiconductor layer used as the baked material film | membrane which has a porous structure, 10 nm or more is preferable at least, More preferably, it is 100-10000 nm.

  From the viewpoint of appropriately preparing 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 in the range of 200 to 800 ° C. Especially preferably, it is the range of 300-800 degreeC.

  The ratio of the actual surface area to the apparent surface area can be controlled by the particle size, specific surface area, firing temperature, etc. of the semiconductor fine particles. In addition, for the purpose of increasing the surface area of the semiconductor particles after heating, increasing the purity in the vicinity of the semiconductor particles, and increasing the efficiency of electron injection from the dye into the semiconductor particles, for example, chemical plating using a titanium tetrachloride aqueous solution or three An electrochemical plating process using a titanium chloride aqueous solution may be performed.

(Oxide semiconductor sensitization treatment)
The sensitization treatment of the oxide semiconductor is performed by dissolving the dye in an appropriate solvent and immersing the substrate on which the semiconductor is baked in the solution. In that case, it is preferable that a substrate on which a semiconductor layer (also referred to as a semiconductor film) is formed by baking is subjected to pressure reduction treatment or heat treatment in advance to remove bubbles in the film. By such treatment, the dye according to the present invention can penetrate deep inside the semiconductor layer (semiconductor film), which is particularly preferable when the semiconductor layer (semiconductor film) is a porous structure film.

  The solvent used for dissolving the dye according to the present invention is not particularly limited as long as it can dissolve the compound and does not dissolve the semiconductor or react with the semiconductor. However, in order to prevent moisture and gas dissolved in the solvent from entering the semiconductor film and hindering the sensitization treatment such as adsorption of the compound, it is preferable to perform deaeration and distillation purification in advance.

  Solvents preferably used in dissolving the compound are alcohol solvents such as methanol, ethanol and n-propanol, ketone solvents such as acetone and methyl ethyl ketone, ether ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran and 1,4-dioxane. Solvents and halogenated hydrocarbon solvents such as methylene chloride and 1,1,2-trichloroethane, particularly preferably methanol, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran and methylene chloride.

(Tensing temperature and time)
The time for immersing the substrate on which the oxide semiconductor is baked in the solution containing the dye according to the present invention is such that the compound penetrates deeply into the semiconductor layer (semiconductor film) to sufficiently adsorb the oxide semiconductor, Sensitization is preferable. Further, from the viewpoint of suppressing degradation products generated by decomposition of the compound in the solution from interfering with the adsorption of the compound, it is preferably 3 to 48 hours under 25 ° C., more preferably 4 to 24 hours. is there. 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 according to the present invention may be used by heating to a temperature at which it does not boil as long as the dye does not decompose. A preferable temperature range is 10 to 100 ° C., more preferably 25 to 80 ° C., but this is not the case when the solvent boils in the temperature range as described above.

"Electrolytes"
The electrolyte used in the present invention will be described.

In the photoelectric conversion element of the present invention, an electrolyte is filled between the counter electrodes, and an electrolyte layer (charge transfer layer) is formed. A redox electrolyte is preferably used as the electrolyte. Here, examples of the redox electrolyte include I ⁻ / I ₃ ⁻ system, Br ⁻ / Br ₃ ⁻ system, and quinone / hydroquinone system. Such a redox electrolyte can be obtained by a conventionally known method. For example, an I ⁻ / I ₃ ⁻ based electrolyte can be obtained by mixing iodine ammonium salt and iodine. The electrolyte layer is composed of dispersions of these redox electrolytes. These dispersions are dispersed in liquid electrolytes when they are solutions, solid polymer electrolytes and gel substances when dispersed in polymers that are solid at room temperature. It is called a gel electrolyte. When a liquid electrolyte is used as the electrolyte layer, an electrochemically inert solvent is used as the solvent, for example, acetonitrile, propylene carbonate, ethylene carbonate, or the like is used. Examples of the solid polymer electrolyte include the electrolyte described in JP-A No. 2001-160427, and examples of the gel electrolyte include the electrolyte described in “Surface Science” Vol. 21, No. 5, pages 288 to 293.

《Counter electrode》
The counter electrode used in the present invention will be described.

The counter electrode as long as it has conductivity, but any conductive material is used, I ₃ ^- oxidation and the like ions, the catalytic ability to perform fast enough the reduction reaction of other redox ions It is preferable to use what you have. Examples of such a material include a platinum electrode, a surface of a conductive material subjected to platinum plating or platinum deposition, rhodium metal, ruthenium metal, ruthenium oxide, and carbon.

[Solar cell]
The solar cell of the present invention will be described.

  The solar cell of the present invention has a structure in which the optimum design and circuit design for sunlight are performed as one aspect of the photoelectric conversion element of the present invention, and the optimum photoelectric conversion is performed when sunlight is used as a light source. Have That is, the oxide semiconductor subjected to dye sensitization can be irradiated with sunlight. When the solar cell of the present invention is constructed, it is preferable that the dye-carrying semiconductor electrode, the electrolyte layer and the counter electrode are housed in a case and sealed, or the whole is resin-sealed.

  When the solar cell of the present invention is irradiated with sunlight or an electromagnetic wave equivalent to sunlight, the dye according to the present invention adsorbed on the oxide semiconductor absorbs the irradiated light or electromagnetic wave and excites it. Electrons generated by excitation move to the oxide semiconductor, and then move to the counter electrode via the conductive support, thereby reducing the redox electrolyte of the charge transfer layer. On the other hand, the dye according to the present invention in which electrons are transferred to an oxide semiconductor is an oxidant, but is reduced by being supplied with electrons from the counter electrode via the redox electrolyte of the electrolyte layer. At the same time, the redox electrolyte of the charge transfer layer is oxidized and returned to a state where it can be reduced again by the electrons supplied from the counter electrode. In this way, electrons flow, and a solar cell using the photoelectric conversion element of the present invention can be configured.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example << Preparation of Photoelectric Conversion Cell >>
(Preparation of photoelectric conversion cell 1)
A commercially available titanium oxide paste (particle size 18 nm) was applied to a fluorine-doped tin oxide (FTO) conductive glass substrate. The paste paste was dried by heating at 60 ° C. for 10 minutes, and then baked at 500 ° C. for 30 minutes. Next, a 1: 1 mixture of the dye D-1 and the dye D-2 was dissolved in ethanol to prepare a 3 × 10 ⁻⁴ M solution. The FTO glass substrate coated and sintered with the titanium oxide was immersed in this solution at room temperature for 12 hours to perform dye adsorption treatment to obtain a photoelectric conversion electrode. As the electrolytic solution, a 3-methylpropionitrile solution containing 0.4 M lithium iodide, 0.05 M iodine, and 0.5 M 4- (t-butyl) pyridine was used. A platinum plate was used as the counter electrode, and the photoelectric conversion cell 1 was obtained by assembling the photoelectric conversion electrode prepared earlier, the electrolyte solution, and the clamp cell.

(Production of photoelectric conversion cells 2 to 11 and 26 to 27)
Photoelectric conversion cells 2 to 11, in the same manner as the production of the photoelectric conversion cell 1, except that the dye D-1 and the dye D-2 used for the production of the photoelectric conversion cell 1 were changed to the dyes shown in Table 1 (combined use). 26-27 were produced.

(Preparation of photoelectric conversion cell 12)
A commercially available titanium oxide paste (particle size 18 nm) was applied to a fluorine-doped tin oxide (FTO) conductive glass substrate. The paste paste was dried by heating at 60 ° C. for 10 minutes, and then baked at 500 ° C. for 30 minutes. Next, Dye D-1 (single use) was dissolved in ethanol to prepare a 3 × 10 ⁻⁴ M solution. The FTO glass substrate coated and sintered with the titanium oxide was immersed in this solution at room temperature for 12 hours to perform dye adsorption treatment to obtain a photoelectric conversion electrode. As the electrolytic solution, a 3-methylpropionitrile solution containing 0.4 M lithium iodide, 0.05 M iodine, and 0.5 M 4- (t-butyl) pyridine was used. A platinum plate was used as the counter electrode, and the photoelectric conversion cell 12 was obtained by assembling the photoelectric conversion electrode, the electrolyte solution, and the clamp cell prepared above.

(Preparation of photoelectric conversion cells 13 to 25)
Photoelectric conversion cells 13 to 25 were produced in the same manner as the production of the photoelectric conversion cell 12 except that the dye D-1 used for the production of the photoelectric conversion cell 12 was changed to the dye described in Table 1.

  The molecular length of each dye used for the production of the photoelectric conversion cell was measured using the above-mentioned ChemDraw Ultra Ver. 9. When drawing a compound at 9.0.1, the interatomic distance (nm) from the central nitrogen atom to the atom to which the acidic group is bonded in the structure optimized for the longest molecular length Table 1 shows the absolute value of the difference in molecular length between the two dyes combined.

<< Evaluation of photoelectric conversion cell >>
Photoelectric conversion characteristics were measured when the produced photoelectric conversion cell was exposed to AM1.5G simulated sunlight (100 mA / cm ² ). That is, for the photoelectric conversion element, current-voltage characteristics were measured at room temperature using an IV tester, and a short circuit current (Jsc), an open circuit voltage (Voc), and a form factor (FF) were obtained. From this, the photoelectric conversion efficiency (η (%)) was determined. The photoelectric conversion efficiency (η (%)) was calculated based on the following formula (A).

Formula (A) η = 100 × (Voc × Jsc × FF) / P
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. Indicates a form factor.

  The evaluation results are shown in Table 2.

  From the table, it can be seen that the photoelectric conversion cell of the present invention has an improved form factor compared to the photoelectric conversion cell of the comparative example. As one of the factors, in the photoelectric conversion cell of the comparative example using one kind of dye, an unadsorbed portion of the dye is formed on the semiconductor layer and reverse electron transfer occurs, but the dye 2 having a similar structure and a different molecular size is used. In the photoelectric conversion cell of the present invention using seeds, it is considered that the dye was closely adsorbed on the semiconductor layer, and as a result, reverse electron transfer was prevented.

  Moreover, although the improvement of the shape factor was seen in the photoelectric conversion cell 26 of this invention, in the photoelectric conversion cell 27 of the comparative example, the fall of the shape factor occurred. If there is an excessive difference in molecular length, it is considered that the similarity of the dye is reduced and a preferable aggregate structure is not formed, and it is impossible to uniformly adsorb on the oxide semiconductor. From this, the difference in molecular length was reasonable up to 2.2 nm.

  FIG. 2 shows the photoelectric conversion cell 1 of the present invention (in combination with Dye D-1 and D-2), the photoelectric conversion cell 12 in Comparative Example (using only Dye D-1), and the photoelectric conversion cell 13 in Comparative Example (Dye D). -2 single use) shows the absorption spectrum of the FTO glass substrate adsorbed with the dye. From FIG. 2, in the photoelectric conversion cell 1 of the present invention, extension of the light absorption wavelength was confirmed. This is thought to be due to the development of aggregation because the two types of dye molecules have similar structures. For the photoelectric conversion cells 2 to 11 and 26 of the present invention other than the photoelectric conversion cell 1, the extension of the light absorption wavelength was confirmed in the same manner.

  From this result, it was suggested that by co-adsorbing two or more dye molecules having different light absorption regions, the light absorption region can be expanded, leading to improvement of battery characteristics.

It is a structure sectional view showing an example of the dye-sensitized photoelectric conversion element of the present invention. It is an absorption spectrum of a dye-adsorbed FTO glass substrate.

Explanation of symbols

1, 1 'substrate 2, 7 transparent conductive film 3 oxide semiconductor 4 dye 5 electrolyte 6 counter electrode 8 platinum (Pt)

Claims (3)

In the dye-sensitized photoelectric conversion element in which a dye-carrying semiconductor electrode in which a plurality of dyes are carried on an oxide semiconductor on a conductive support and a counter electrode are arranged to face each other with a charge transfer layer interposed therebetween, The dye has two kinds of dyes represented by the following general formulas (1) and (4), or general formulas (2) and (5), or general formulas (3) and (6), and A dye-sensitized photoelectric conversion element characterized in that a difference in molecular length (| L ₁ −L ₂ |) between two kinds of dyes is in accordance with the following formula (X).

(In General Formula (1) and General Formula (4), Ar ₁ represents an aryl group and may have a substituent. R ₁ and R ₂ are a hydrogen atom, a halogen atom, an alkyl group, an amino group, Represents an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group, and heterocyclic group may have a substituent, and R ₃ and R ₁₀ are a single bond, an alkylene group, an arylene group, or a divalent group. And an alkylene group, an arylene group or a divalent heterocyclic group may have a substituent, and X ₁ and X ₇ each represents an acidic group, R ₁ , R ₂ and Ar ₁ may be linked to form a ring.
In general formulas (2) and (5), Ar ₂ and Ar ₃ each represents an aryl group and may have a substituent. R ₄ represents a hydrogen atom, a halogen atom, an alkyl group, an amino group, an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group and heterocyclic group may have a substituent. R ₅ , R ₆ , R ₁₁ , and R _{12 each} represents a single bond, an alkylene group, an arylene group, or a divalent heterocyclic group, or a linking group thereof. The alkylene group, the arylene group, or the divalent heterocyclic group is It may have a substituent. X ₂ , X ₃ , X ₈ and X ₉ represent an acidic group. R ₄ , Ar ₂ and Ar ₃ may be connected to form a ring.
In general formulas (3) and (6), Ar ₄ , Ar ₅ , and Ar ₆ represent an aryl group and may have a substituent. R ₇ , R ₈ , R ₉ , R ₁₃ , R ₁₄ and R _{15 each} represents a single bond, an alkylene group, an arylene group or a divalent heterocyclic group, an alkylene group, an arylene group or a divalent heterocyclic group; Alternatively, these bonding groups may have a substituent. Ar ₄ , Ar ₅ and Ar ₆ may be linked to form a ring. X ₄ , X ₅ , X ₆ , X ₁₀ , X ₁₁ and X ₁₂ each represents an acidic group. )
Formula (X) 0.1 ≦ | L ₁ −L ₂ | ≦ 2.2 (nm)
(Wherein, L ₁ is the general formula (1) to (represents the molecular length of the dyes represented by 3), L ₂ represents a general formula (4) the molecular length of the dye represented by - (6). The molecular lengths L ₁ and L ₂ are the central nitrogen atom in the structure optimized for the longest molecular length when the compound is drawn with ChemDraw Ultra Ver. 9.0.1 manufactured by Hybrid Soft. To the atom to which the acidic group is bonded (nm). In the dye-sensitized photoelectric conversion element in which a dye-carrying semiconductor electrode in which a plurality of dyes are carried on an oxide semiconductor on a conductive support and a counter electrode are arranged to face each other with a charge transfer layer interposed therebetween, The dye has two kinds of dyes represented by the following general formulas (7) and (10), or general formulas (8) and (11), or general formulas (9) and (12), and A dye-sensitized photoelectric conversion element characterized in that a difference in molecular length (| L ₁ −L ₂ |) between two kinds of dyes is in accordance with the following formula (X).

(In the general formula (7) and the general formula (10), Ar ₂₁ , Ar ₂₂ and Ar ₂₃ each represent a divalent aryl group and may have a substituent. R ₂₁ and R ₂₃ represent a hydrogen atom, Represents a halogen atom, an alkyl group, an amino group, an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group and heterocyclic group may have a substituent, R ₂₂ and R ₃₀ are a single bond, Represents an alkylene group, an arylene group, or a divalent heterocyclic group, or a bonding group thereof, and the alkylene group, the arylene group, or the divalent heterocyclic group may have a substituent, X ₂₁ , X ₂₇ Represents an acidic group, and Ar ₂₁ , Ar ₂₂ and Ar ₂₃ may be linked to form a ring.
In General Formula (8) and General Formula (11), Ar ₂₄ , Ar ₂₅ and Ar ₂₆ represent an aryl group and may have a substituent. R ₂₄ represents a hydrogen atom, a halogen atom, an alkyl group, an amino group, an aryl group or a heterocyclic group, and the alkyl group, amino group, aryl group or heterocyclic group may have a substituent. R ₂₅ , R ₂₆ , R ₃₁ and R _{32 each} represents a single bond, an alkylene group, an arylene group, or a divalent heterocyclic group, or a linking group thereof, and the alkylene group, the arylene group, or the divalent heterocyclic group is It may have a substituent. X ₂₂ , X ₂₃ , X ₂₈ and X ₂₉ each represents an acidic group. Ar ₂₄ , Ar ₂₅ and Ar ₂₆ may be linked to form a ring.
In General Formula (9) and General Formula (12), Ar ₂₇ , Ar ₂₈ , and Ar ₂₉ each represent an aryl group and may have a substituent. R ₂₇ , R ₂₈ , R ₂₉ , R ₃₃ , R ₃₄ , and R _{35 each} represents a single bond, an alkylene group, an arylene group, or a divalent heterocyclic group, or a linking group thereof. An alkylene group, an arylene group, or 2 The valent heterocyclic group may have a substituent. Ar ₂₇ , Ar ₂₈ and Ar ₂₉ may be linked to form a ring. X ₂₄ , X ₂₅ , X ₂₆ , X ₃₀ , X ₃₁ and X ₃₂ represent an acidic group. )
Formula (X) 0.1 ≦ | L ₁ −L ₂ | ≦ 2.2 (nm)
(In the formula, L ₁ represents the molecular length of the dye represented by the general formulas (7) to (9), and L ₂ represents the molecular length of the dye represented by the general formulas (10) to (12). The molecular lengths L ₁ and L ₂ are the central nitrogen atom in the structure optimized for the longest molecular length when the compound is drawn with ChemDraw Ultra Ver. 9.0.1 manufactured by Hybrid Soft. To the atom to which the acidic group is bonded (nm). A solar cell using the dye-sensitized photoelectric conversion element according to claim 1 or 2.

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