JP4557097B2 - Electrolyte for photoelectric conversion element and photoelectric conversion element and dye-sensitized solar cell using the electrolyte - Google Patents

Description

  The present invention relates to an electrolyte for a photoelectric conversion element, a photoelectric conversion element using the electrolyte, and a dye-sensitized solar cell.

  In recent years, environmental problems such as global warming caused by an increase in carbon dioxide have become serious, and non-silicon solar cells have attracted attention as solar cells that can reduce the environmental burden and reduce manufacturing costs. ing.

Among non-silicon-based solar cells, dye-sensitized solar cells developed by Grezel, etc. of Switzerland have high photoelectric conversion efficiency among solar cells using organic materials, and are less expensive to manufacture than silicon-based solar cells. It is also attracting attention as a new type of solar cell due to its advantages such as low price.
However, since dye-sensitized solar cells are electrochemical cells, organic electrolytes or ionic liquids are used as electrolytes. When organic electrolytes are used, they may volatilize or be depleted during long-term use. However, when using ionic liquids, volatilization and depletion during long-term use can be prevented, but there are durability problems such as structural deterioration due to liquid leakage. It was.
In view of this, studies have been made to change the electrolyte from liquid to gel or solid for the purpose of preventing volatilization and leakage of the electrolyte and ensuring long-term stability and durability of the solar cell.

For example, Patent Document 1 describes “a gel-like electrolyte composition containing an ionic liquid and conductive particles as main components” ([Claim 1] and [Claim 2]).
Patent Document 2 discloses that “a dye-sensitized photoelectric conversion element having a porous photoelectrode layer made of dye-sensitized semiconductor particles, a charge transport layer, and a counter electrode layer in this order, The layer is made of a solid mixture containing 1 to 50% by mass of a p-type conductive polymer, 5 to 50% by mass of a carbon material, and 20 to 85% by mass of an ionic liquid. Conversion element ”is described ([Claim 1]).

  However, when the electrolyte composition described in Patent Document 1 is used, from the viewpoint of achieving high energy conversion efficiency, a redox couple (redox couple), in particular, when iodine is used, the photoelectric conversion element due to the corrosive nature of iodine. There is a problem that the metal wiring (collecting electrode), the sealing material, and the like constituting the material are corroded and the stability of the electrolyte is affected by the volatility of iodine.

International Publication No. 2005/006482 JP 2007-227087 A

Further, as a result of examining the dye-sensitized photoelectric conversion element described in Patent Document 2, the present inventor has revealed that the energy conversion efficiency is not sufficient. This is because when a mixture of a p-type conductive polymer (for example, polyaniline, polypyrrole, etc.), a carbon material (for example, acetylene black, etc.) and an ionic liquid is used as the charge transport layer, the carbon material (especially acetylene black) It is considered that the ability to retain the ionic liquid itself (retention ability) is low and the retention ability is further lowered by mixing with the p-type conductive polymer.
Therefore, the present invention provides an electrolyte for a photoelectric conversion element that can achieve high energy conversion efficiency even when substantially not containing iodine, and a photoelectric conversion element and a dye-sensitized solar cell using the electrolyte. Objective.

As a result of intensive studies, the inventor has found that the electrolyte for a photoelectric conversion element containing the ionic liquid and the carbon material having a specific surface area of 1000 to 3500 m ² / g in a specific ratio does not substantially contain iodine. The present inventors have found that high energy conversion efficiency can be achieved and completed the present invention.
That is, the present invention provides the following (a) to ( k ).

(A) containing an ionic liquid (A) and a carbon material (B) having a specific surface area of 1000 to 3500 m ² / g,
The content of the carbon material (B) is Ri 10-50 parts by der respect to the ionic liquid (A) 100 parts by mass of,
Furthermore, as carbon material (C) other than the carbon material (B), acetylene black, boron-modified acetylene black, a carbon material having a pH of 2 to 6 measured by a pH measuring method defined in JIS Z8802, and nitrogen the photoelectric conversion element for electrolyte you containing any one or more of adsorption specific surface area is selected from the group consisting of higher carbon black 90m ² / g.

  (B) The electrolyte for photoelectric conversion elements according to (a), wherein the carbon material (B) has a primary average particle size of 0.5 to 120 μm.

  (C) The electrolyte for photoelectric conversion elements according to (a) or (b), wherein the ionic liquid (A) has a cation represented by the following formula (1) or (2).

In Formula (1), R ¹ represents a hydrocarbon group that may contain a C 1-20 hetero atom, and has a substituent that may contain a C 1-20 hetero atom. May be. R ² and R ³ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, it may contain a hetero atom. However, when the nitrogen atom contains a double bond, R ³ does not exist. In formula (2), Q represents a nitrogen atom, an oxygen atom, a phosphorus atom or a sulfur atom, and R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a hydrogen atom or a hydrocarbon having 1 to 8 carbon atoms. Represents a group and may contain a heteroatom. However, when Q is an oxygen atom or a sulfur atom, R ⁷ does not exist.

  (D) The electrolyte for photoelectric conversion elements according to (c), wherein the ionic liquid (A) has iodine ions as anions.

( E ) The electrolyte for photoelectric conversion elements according to any one of the above (a) to (d), wherein the carbon material having a pH of 2 to 6 has a primary average particle diameter of 0.010 to 0.050 μm.

( F ) Said ( a )-whose total content of said carbon material (B) and said other carbon material (C) is 10-50 mass parts with respect to 100 mass parts of said ionic liquids (A). ( E ) The electrolyte for photoelectric conversion elements in any one of.

( G ) The ratio of the content of the carbon material (B) and the other carbon material (C) [carbon material (B) / other carbon material (C)] is 99.9 / 0.1-60. The electrolyte for photoelectric conversion elements according to any one of ( a ) to ( f ), which is / 40.

( H ) The above ( a ) to ( g ) prepared by mixing the carbon material (B) after mixing the ionic liquid (A) and the other carbon material (C) to obtain a dispersion. The electrolyte for photoelectric conversion elements according to any one of the above.

( I ) The electrolyte for photoelectric conversion elements according to any one of (a) to ( h ), further containing silicon oxide and / or a metal oxide.

( J ) a photoelectrode having a transparent conductive film and a metal oxide semiconductor porous film;
A counter electrode disposed to face the photoelectrode;
An electrolyte layer disposed between the photoelectrode and the counter electrode;
The photoelectric conversion element whose said electrolyte layer is an electrolyte for photoelectric conversion elements in any one of said (a)-( i ).

( K ) A dye-sensitized solar cell in which a photosensitizing dye is supported on the photoelectrode according to ( j ) above.

As will be described below, according to the present invention, an electrolyte for a photoelectric conversion element that can achieve high energy conversion efficiency without substantially containing iodine, and a photoelectric conversion element and dye sensitization using the electrolyte This is useful because a solar cell can be provided.
The electrolyte for photoelectric conversion elements of the present invention is very useful because it can achieve high energy conversion efficiency without using a p-type conductive polymer such as polyaniline.

FIG. 1 is a schematic cross-sectional view showing an example of the basic configuration of the photoelectric conversion element of the present invention. FIG. 2 is a drawing showing the basic configuration of the solar cell of the present invention used in Examples and the like.

Hereinafter, the present invention will be described in more detail.
The electrolyte for photoelectric conversion elements of the present invention (hereinafter also simply referred to as “the electrolyte of the present invention”) contains an ionic liquid (A) and a carbon material (B) having a specific surface area of 1000 to 3500 m ² / g. And it is electrolyte for photoelectric conversion elements whose content of the said carbon material (B) is 10-50 mass parts with respect to 100 mass parts of said ionic liquids (A).
Next, each component of the electrolyte of the present invention will be described in detail.

[Ionic liquid (A)]
The ionic liquid (A) used for the electrolyte of the present invention is not particularly limited, and any ionic liquid used as a conventional electrolyte can be used.
For example, the fourth described in Hiroyuki Ohno, “Ionic Liquids—Development Frontiers and Future”, CMC Publishing (2003), “Functional Creation and Application of Ionic Liquids” NTS (2004), etc. Secondary ammonium salts, imidazolium salts, pyridinium salts, pyrrolidinium salts, piperidinium salts, and the like can be used.

The ionic liquid (A) has a cation and an anion which is a counter ion.
Here, specifically as a cation, the cation represented by following formula (1) or (2) is illustrated suitably.

In Formula (1), R ¹ represents a hydrocarbon group that may contain a C 1-20 hetero atom, and has a substituent that may contain a C 1-20 hetero atom. May be. R ² and R ³ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, it may contain a hetero atom. However, when the nitrogen atom contains a double bond, R ³ does not exist.
In formula (2), Q represents a nitrogen atom, an oxygen atom, a phosphorus atom or a sulfur atom, and R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a hydrogen atom or a hydrocarbon having 1 to 8 carbon atoms. Represents a group and may contain a heteroatom. However, when Q is an oxygen atom or a sulfur atom, R ⁷ does not exist.

Here, as the hydrocarbon group which may contain a C 1-20 hetero atom of R ^{1 in} the above formula (1), a ring structure together with a nitrogen atom (ammonium ion) in the above formula (1). It is preferable to take it.
Then, may have R ¹ in the formula (1) is, as the substituent which may contain a hetero atom having 1 to 20 carbon atoms, an alkyl group having 1 to 12 carbon atoms (e.g., methyl Group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, etc.), C1-C12 alkoxy group (for example, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group) Group, n-butoxy group, tert-butoxy group, sec-butoxy group, n-pentoxy group, n-hexoxy group, 1,2-dimethylbutoxy group, etc.), alkyl alkoxy group having 2 to 12 carbon atoms (for example, methylene) methoxy (-CH ₂ OCH _3), ethylene methoxy _{(-CH 2 CH 2 OCH 3)} , n- propylene - iso - propoxy _{(-CH 2 CH 2 CH 2 OCH} (CH 3 _2), the methylene -t- butoxy _{(-CH 2 -O-C (CH} 3) 3 , etc.) are preferred. Further, R ¹ in the formula (1) is closed the substituent more You may do it.

Further, R ² and R ³ of the hydrocarbon group which may contain a hetero atom having 1 to 20 carbon atoms in the formula (1), specifically, an alkyl group having 1 to 12 carbon atoms (e.g. , Methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, etc.), C1-C12 alkoxy group (for example, methoxy group, ethoxy group, n-propoxy group, iso -Propoxy group, n-butoxy group, tert-butoxy group, sec-butoxy group, n-pentoxy group, n-hexoxy group, 1,2-dimethylbutoxy group, etc.), alkyl alkoxy group having 2 to 12 carbon atoms (for example, , Methylene methoxy group (—CH ₂ OCH ₃ ), ethylene methoxy group (—CH ₂ CH ₂ OCH ₃ ), n-propylene-iso-propoxy group (—CH ₂ CH ₂ CH ₂ OCH (C H ₃ ) ₂ ), methylene-t-butoxy group (—CH ₂ —O—C (CH ₃ ) ₃ etc.) and the like.

In the above formula (2), the hydrocarbon group which may contain a hetero atom having 1 to 8 carbon atoms of R ⁴ , R ⁵ , R ⁶ and R ⁷ is specifically 1 to 1 carbon atom. 8 alkyl groups (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, etc.), C 1-8 alkoxy groups (for example, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, tert-butoxy group, sec-butoxy group, n-pentoxy group, n-hexoxy group, 1,2-dimethylbutoxy group, etc.), C 2-8 Alkyl alkoxy groups (for example, methylene methoxy group (—CH ₂ OCH ₃ ), ethylene methoxy group (—CH ₂ CH ₂ OCH ₃ ), n-propylene-iso-propoxy group (—CH ₂ CH ₂ CH ₂ OCH) (CH ₃ ) ₂ ), methylene-t-butoxy group (—CH ₂ —O—C (CH ₃ ) ₃ etc.) and the like.

Examples of the cation represented by the above formula (1) include imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, and the like.
Specifically, a cation represented by any of the following formulas (3) to (6) is preferably exemplified.
Among these, the cation represented by the following formulas (3) and (5) is the photoelectric conversion of the photoelectric conversion element using the electrolyte of the present invention (hereinafter also referred to as “the photoelectric conversion element of the present invention”). This is preferable because the efficiency tends to be better.

In formulas (3) to (6), R ^{8 to} R ⁴⁰ each independently represent a hydrocarbon group that may contain a nitrogen atom having 1 to 20 carbon atoms.
More specifically, the following cations are mentioned.

Examples of the cation represented by the above formula (2) include organic cations such as ammonium ion, sulfonium ion, and phosphonium ion.
Specifically, the following cations are preferably exemplified.
Among these, aliphatic quaternary ammonium ions are preferable because the photoelectric conversion efficiency of the photoelectric conversion element of the present invention tends to be better.

On the other hand, specific examples of anions of the ionic liquid (A) include I ⁻ , Br ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ ⁻ , NO ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ and CH _3. COO ⁻ , CF ₃ COO ⁻ , CF ₃ SO ₃ ⁻ , (CN) ₄ B ⁻ , SCN ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CN) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , (CN) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , F (HF) _n ⁻ , CF ₃ CF ₂ CF ₂ CF ₂ SO ₃ ⁻ , (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ , CF ₃ CF ₂ CF ₂ COO ^-, and the like are preferably exemplified.
Of these, bromine ions (Br ⁻ ) and iodine ions (I ⁻ ) are preferable because the photoelectric conversion efficiency of the photoelectric conversion element of the present invention tends to be better, and iodine ions (I ⁻ ). More preferably.

As an ionic liquid (A), what consists of a combination of the cation and the anion illustrated above, etc. are mentioned, for example.
Among these, an ionic liquid having imidazolium ions as cations and iodine ions as anions is preferable.
In the present invention, the method for synthesizing the ionic liquid (A) is not particularly limited, and various ionic liquids composed of combinations of cations and anions exemplified above can be synthesized by a conventionally known method.

  Examples of such an ionic liquid (A) include 1-methyl-3-methylimidazolium iodide, 1-ethyl-3-methylimidazolium iodide, 1-methyl-3-pentylimidazolium iodide, 1- In addition to synthetic products such as hexyl-3-methylimidazolium iodide, 1-((2-methoxyethoxy) ethyl) -3-((2-methoxyethoxy) ethyl) imidazolium iodide, use commercially available products Specifically, for example, 1-methyl-3-propylimidazolium iodide (manufactured by Tokyo Chemical Industry Co., Ltd.), 1-methyl-3-butylimidazolium iodide (manufactured by Tokyo Chemical Industry Co., Ltd.), 1-methyl- 1-methyl-pyrrolidinium iodide (manufactured by Aldrich), 1-ethyl-3-methylimidazolium tetracyano Rate (Merck Co.), 1-ethyl-3-methylimidazolium thiocyanate (Merck Co.) and the like can be used.

  In the present invention, the content of the ionic liquid (A) is preferably 50 to 95% by mass, and more preferably 65 to 95% by mass with respect to the total mass of the electrolyte of the present invention. When the content is within this range, the photoelectric conversion efficiency of the photoelectric conversion element of the present invention becomes better.

[Carbon material (B)]
The carbon material (B) used for the electrolyte of the present invention is a carbon material having a specific surface area of 1000 to 3500 m ² / g.
Here, the specific surface area refers to a measured value measured using the BET method by nitrogen adsorption according to the method defined in JIS K1477.

In the present invention, by containing 10 to 50 parts by mass of the carbon material (B) with respect to 100 parts by mass of the ionic liquid (A), high energy conversion efficiency can be achieved even if substantially no iodine is contained. can do.
This is because a carbon material (B) having a surface area larger than that of carbon black (acetylene black) or graphite is used to form an electrolyte in which the carbon material (B) sufficiently holds the ionic liquid (A). It is considered that this is because the ionic liquid (A) can be sufficiently filled in the metal oxide semiconductor porous film described later. In addition, since the carbon material (B) having a large surface area has a function like a sponge capable of taking in and out the ionic liquid (A), each interface, that is, an interface between the electrolyte and a metal oxide semiconductor porous film described later, This is considered to be because the formation of a layer (ionic liquid layer) in which the ionic liquid (A) formed at the interface between the carbon particles and the interface between the electrolyte and the counter electrode is localized is suppressed. If the ionic liquid (A) is not present in the electrolyte, it does not function as an electrolyte for the photoelectric conversion element. For example, in the dye-sensitized photoelectric conversion element described in Patent Document 2, the ionic liquid is the above-described one. It was found that an ionic liquid layer having a low charge transporting ability is formed between the interfaces, which may become a resistance component that lowers the photoelectric conversion efficiency.
From the viewpoint of filling the metal oxide semiconductor porous membrane with the ionic liquid (A) and enhancing the function of the sponge described above, the content of the carbon material (B) is 100 masses of the ionic liquid (A). The amount is preferably 15 to 45 parts by mass, more preferably 25 to 40 parts by mass with respect to parts.

In the present invention, the specific surface area of the carbon material (B) is preferably from 1100~3200m ² / g, and more preferably 1200~2800m ² / g. When the specific surface area is within this range, the filling of the metal oxide semiconductor porous film with the ionic liquid (A) and the function of the sponge described above work effectively, and the photoelectric conversion efficiency of the photoelectric conversion element of the present invention is better. It becomes.

Furthermore, in this invention, it is preferable that the primary average particle diameters of the said carbon material (B) are 0.5-120 micrometers, and it is more preferable that it is 0.8-80 micrometers. When the primary average particle diameter is in this range, the photoelectric conversion efficiency of the photoelectric conversion element of the present invention becomes better.
Here, the primary average particle diameter is a value measured by a method of measuring the primary average particle diameter of a normal carbon material (for example, activated carbon or the like). In the present invention, the carbon material (B) is It means a 50% volume cumulative diameter (D50) measured by using a laser diffraction particle size distribution analyzer (for example, SALD2000J (registered trademark, manufactured by Shimadzu Corporation)) after being dispersed in a neutral detergent-containing aqueous solution.

Furthermore, in the present invention, the specific resistance of the carbon material (B) is preferably 1 × 10 ^{−4 to} 5 × 10 ² Ω · cm, and preferably 1 × 10 ⁻² to 1 × 10 ² Ω · cm. It is more preferable that it is 5 × 10 ^{−2 to} 50 Ω · cm. When the specific resistance is within this range, surface graphitization has not progressed, so that the wettability with the ionic liquid (A) described above is good, and the carbon material has a high ability to hold the ionic liquid (A).
Here, the specific resistance means a value obtained by measuring specific resistance (volume specific resistance value) by a two-terminal measurement method using a low resistivity meter.
The specific resistance of acetylene black, which will be described later, is 3 × 10 ⁻² Ω · cm.

As such a carbon material (B), specifically, for example, activated carbon (specific surface area: 1000 to 2800 m ² / g, primary average particle diameter: 0.5 to 120 μm, specific resistance: 1.0 × 10 10 ⁻¹ Ω · cm), boron-containing porous carbon material (specific surface area: 1000 to 2000 m ² / g, primary average particle size: 0.5 to 100 μm, specific resistance: 1 × 10 ⁻¹ Ω · cm), nitrogen Containing porous carbon material (specific surface area: 1000 to 2000 m ² / g, primary average particle size: 0.5 to 100 μm, specific resistance: 1 × 10 ⁻¹ Ω · cm), and the like. Or two or more of them may be used in combination.

Of these, activated carbon is preferable because it is easily available.
The activated carbon is not particularly limited, and activated carbon particles used in known carbon electrodes and the like can be used. Specific examples thereof include coconut shell, wood powder, petroleum pitch, phenol resin, etc., water vapor, various chemicals, alkali Activated carbon particles activated using the above, etc., and these may be used alone or in combination of two or more.

[Other carbon materials (C)]
From the viewpoint of further improving the photoelectric conversion efficiency of the photoelectric conversion element of the present invention, the electrolyte of the present invention includes other carbon materials (C) such as acetylene black (C1), boron-modified acetylene black (C2), and JIS Z8802. Any one or more selected from the group consisting of carbon material (C3) having a pH of 2 to 6 measured by the pH measurement method and carbon black (C4) having a nitrogen adsorption specific surface area of 90 m ² / g or more. using Ru.
Two or more of these carbon materials (C) can be used in combination, but it is preferable to use a boron-modified acetylene black (C2) and a carbon material (C3) described later in combination.

<Acetylene black (C1)>
The acetylene black (C1) that can be used in the electrolyte of the present invention is not particularly limited, and is a carbon black having high crystallinity obtained by thermal decomposition of acetylene gas, and is a conventionally known one used as a conductivity imparting agent. Can be used.

As such acetylene black (C1), specifically, for example, acetylene black (denka black powder, specific surface area: 68 m ² / g, primary average particle size: 400 nm, specific resistance: 3 × 10 ⁻² Ω · cm, manufactured by Denki Kagaku Kogyo Co., Ltd.).

<Boron-modified acetylene black (C2)>
The boron-modified acetylene black (C2) that can be used in the electrolyte of the present invention is not particularly limited, and specific examples thereof include boron-modified acetylene black (Denka Black BMAB, specific surface area: 50 m ² / g, primary average particle diameter). : 35 nm, specific resistance: 1 × 10 ⁻² Ω · cm, manufactured by Denki Kagaku Kogyo Co., Ltd.).
In the present invention, the photoelectric conversion efficiency of the photoelectric conversion element of the present invention is better when the boron-modified acetylene black is used than when the acetylene black (C1) is used.

<Carbon material (C3)>
The carbon material (C3) that can be used for the electrolyte of the present invention is a carbon material having a pH of 2 to 6 measured by the pH measurement method defined in JIS Z8802.
Specifically, the pH is measured as follows. First, 5 g of a carbon material sample is weighed into a beaker, 50 mL of water is added thereto, and heated until the water boils. Next, the heated dispersion is cooled to room temperature, and after the carbon material is allowed to settle, the supernatant is removed, leaving a mud. An electrode of a glass electrode pH meter is placed in this mud and measured by the pH measurement method specified in JIS Z8802-1984.

Furthermore, in this invention, it is preferable that the primary average particle diameter of the said carbon material (C3) is 0.010-0.050 micrometer, and it is more preferable that it is 0.010-0.035 micrometer. When the primary average particle diameter is in this range, the photoelectric conversion efficiency of the photoelectric conversion element of the present invention becomes better.
Here, the primary average particle diameter is a value measured by a method of measuring a primary average particle diameter of a normal carbon material (for example, furnace carbon black or the like). It means the arithmetic mean diameter obtained by observation with an electron microscope.

Examples of such a carbon material (C3) include acidic carbon black to which acidic groups such as phenolic hydroxyl group, carboxy group, quinone group, and lactone group are attached or bonded; pigment carbon black; color carbon black; These may be used alone or in combination of two or more.
Among these, acidic carbon black is preferable because it can be easily mixed with the ionic liquid (A) described above and the photoelectric conversion efficiency of the photoelectric conversion element of the present invention becomes better.

Here, the carbon black for attaching the hydroxyl group and the like used for the acidic carbon black is not particularly limited, and carbon blacks that are usually used such as oil furnace black, gas furnace black, thermal black, channel black (gas black), etc. Can be used.
Examples of a method for attaching a hydroxyl group or the like include a normal ozone treatment, a plasma treatment, a liquid phase oxidation treatment, a method disclosed in JP-A-2004-238111, and the like.

  Moreover, as said acidic carbon black, although channel black (gas black) itself which has many acidic groups (phenolic hydroxyl group, carboxy group, etc. which were illustrated above) on the carbon black surface can also be used, a commercial item is used. Specifically, for example, # 2200B manufactured by Mitsubishi Chemical Corporation (pH: 3.5, primary average particle size: 0.018 μm), # 1000 (pH: 3.5, primary average particle size) : 0.018 μm), # 970 (pH: 3.5, primary average particle size: 0.016 μm), MA77 (pH: 2.5, primary average particle size: 0.023 μm), MA7 (pH: 3) Primary average particle size: 0.024 μm), MA8 (pH: 3, primary average particle size: 0.024 μm), MA11 (pH: 3.5, primary average particle size: 0.029 μm), MA100 pH: 3.5, primary average particle size: 0.024 μm), MA100R (pH: 3.5, primary average particle size: 0.024 μm), MA100S (pH value: 3.5, primary average particle size) : 0.024 μm), MA230 (pH: 3, primary average particle size: 0.030 μm), MA200RB (pH: 3, primary average particle size: 0.030 μm) and MA14 (pH: 3, primary average particle) Diameter: 0.040 μm);

  Special Black 6 (pH: 2.5, primary average particle size: 17 nm), Special Black 5 (pH: 3.0, primary average particle size: 20 nm), Special Black 4 (pH: 3.0, manufactured by Degussa Evonik) Primary average particle size: 25 nm), Special Black 4A (pH: 3.0, primary average particle size: 25 nm), Special Black 550 (pH: 2.8, primary average particle size: 25 nm), Special Black 100 (pH: 3.3, primary average particle size: 50 nm), Special Black 250 (pH: 3.1, primary average particle size: 56 nm), Special Black 350 (pH: 3.5, primary average particle size: 31 nm), Printex 150T (PH: 4.0, primary average particle size: 29 nm), Color Black FW1 (pH: 3.5, primary average particle size: 13 nm), Color Black FW18 (pH: 4.5, primary average particle size) : 15nm), Color Black FW2 5 (pH: 3.5, primary average particle size: 11 nm), Color Black S170 (pH: 4.5, primary average particle size: 17 nm), Color Black S160 (pH: 4.5, primary average particle) Diameter: 17 nm), Color Black FW200 (pH: 2.5, primary average particle size: 13 nm), Color Black FW2 (pH: 2.5, primary average particle size: 13 nm) and Color Black FW2V (pH: 2) .5, primary average particle size: 13 nm);

  Toka Black # 8300F (pH: 5.0, primary average particle size: 16 nm) and Toka Black # 8500F (pH: 5.5, primary average particle size: 14 nm) manufactured by Tokai Carbon Co., Ltd .; Can do.

These may be used alone or in combination of two or more.
Among these, from the viewpoint of increasing the temporal stability of the electrolyte for a photoelectric conversion element of the present invention and further improving the photoelectric conversion efficiency of the photoelectric conversion element of the present invention, the pH is 3 to 5.5. preferable.

<Carbon black (C4)>
The carbon black (C4) that can be used for the electrolyte of the present invention is not particularly limited as long as the nitrogen adsorption specific surface area is 90 m ² / g or more.
Here, the nitrogen adsorption specific surface area is a surrogate property of the surface area that carbon black can be used for adsorption with rubber molecules, and the nitrogen adsorption amount on the surface of carbon black is defined as JIS K6217-7: 2008 “Part 7: Rubber compound. -The value measured according to "How to determine the multipoint nitrogen specific surface area and the statistical thickness specific surface area".

In the present invention, because the photoelectric conversion efficiency of the photoelectric conversion element of the present invention becomes better, the nitrogen adsorption specific surface area is preferably used carbon black 90~200m ² / g, 100~180m ² / It is more preferable to use g carbon black.

Furthermore, in the present invention, the carbon black (C4) is preferably carbon black having a pH of 7 to 13 measured by a pH measurement method defined in JIS Z8802, more preferably a carbon black having a pH of 7 to 11. It is.
The measurement of the pH is specifically performed as follows in the same manner as described in the carbon material (C3). First, 5 g of a carbon black sample is weighed in a beaker, 50 mL of water is added thereto, and heated until the water boils. Next, the heated dispersion is cooled to room temperature, carbon black is allowed to settle, and then the supernatant is removed, leaving a mud. An electrode of a glass electrode pH meter is placed in this mud and measured by the pH measurement method specified in JIS Z8802-1984.

A commercial item can be used as such carbon black (C4).
Specifically, for example, SAF (N134, nitrogen adsorption specific surface area: 151m ² /g,pH:7.3, manufactured by Cabot Japan K.K.), ISAF (N234, nitrogen adsorption specific surface ^{area: 117m 2 / g, pH:} 7 .5, manufactured by Cabot Japan K.K.), ISAF (N220, nitrogen adsorption specific surface area: 119m ² /g,pH:7.5, manufactured by Cabot Japan K.K.), ISAF (N219, nitrogen adsorption specific surface area: 106m ² / g, pH : 7.5, manufactured by Tokai Carbon Co., Ltd.), HAF (N339, nitrogen adsorption specific surface area: 93 m ^{2 /} g, pH: 7.5, manufactured by Tokai Carbon Co., Ltd.), and the like.

In the present invention, the carbon black (C4) preferably has a primary average particle diameter of 5 to 30 nm, and more preferably 5 to 25 nm. When the primary average particle diameter is in this range, the photoelectric conversion efficiency of the photoelectric conversion element of the present invention becomes better.
Here, the primary average particle diameter means the arithmetic average diameter obtained by observing the carbon black particles with an electron microscope, as described in the carbon material (C3).

In the present invention, when the other carbon material (C) is contained, 100 masses of the ionic liquid (A) can be achieved because higher energy conversion efficiency can be achieved without substantially containing iodine. It is preferable to contain 10-50 mass parts of said carbon material (B) and said other carbon material (C) in total with respect to a part.
Similarly, the ratio [carbon material (B) / other carbon material (C)] of the carbon material (B) and the other carbon material (C) is 99.9 / 0.1. It is preferably ~ 60/40.
Here, for the content, any two or more of acetylene black (C1), boron-modified acetylene black (C2), carbon material (C3), and carbon black (C4) were used as the other carbon material (C). In some cases, it refers to the total content, and when only one of them is used, it refers to the content of any one of them.

Although it is not clear in detail that high energy conversion efficiency can be achieved without substantially containing iodine, it is considered as follows.
Among the other carbon materials (C), acetylene black (C1) and boron-modified acetylene black (C2) having a small surface area, together with the ionic liquid (A) that cannot be retained by the carbon material (B), It is thought that it can contribute to promotion. In particular, since boron-modified acetylene black (C2) has hydrophilicity due to the introduction of boron, the affinity with the above-described ionic liquid (A) is increased, and dispersion into the ionic liquid (A) is achieved. It is considered that the effect of promoting the charge transfer can be enhanced as compared with acetylene black (C1).
Of the other carbon materials (C), the carbon material (C3) is an anion derived from an acidic group (such as the phenolic hydroxyl group or carboxy group exemplified above) present as a functional group on the surface of the carbon material. For example, it is considered that carboxylate, phenolate, etc.) interact with the cation of the ionic liquid (A) described above. Further, it is considered that the presence of functional groups on the surface of the carbon material makes it more hydrophilic than general carbon black and graphite, and it is also considered that the dispersion in the ionic liquid (A) described above is easy. .
Further, among other carbon materials (C), carbon black (C4) having a large nitrogen specific surface area is similar to the above-described carbon material (B), and the sponge ionic liquid (A) can be taken in and out. The ionic liquid (A) formed at each interface, that is, the interface between the electrolyte and the metal oxide semiconductor porous film described later, the interface between the carbon particles, and the interface between the electrolyte and the counter electrode. In addition, carbon black (C4) has a well-developed structure, so that the electron conductivity is improved. From these results, the photoelectric conversion element This is probably because the open-circuit voltage has increased.
The open circuit voltage is the voltage between the terminals when no current is flowing through the power supply terminal. Light is emitted when the reverse voltage (bias voltage) is applied to the electrodes and the bias voltage is gradually increased. The voltage generated when the generated current stops flowing against this bias voltage (when the current value is zero).

In the present invention, the carbon material (B) and the other carbon are added from the viewpoint of filling the metal oxide semiconductor porous film with the ionic liquid (A) and enhancing the function and charge transfer of the sponge. As for the total content of material (C), it is more preferable that it is 15-45 mass parts with respect to 100 mass parts of said ionic liquids (A), and it is still more preferable that it is 20-40 mass parts.
Furthermore, from the same viewpoint, the ratio of the content of the carbon material (B) and the other carbon material (C) [carbon material (B) / other carbon material (C)] is 99/1 to 65. / 35 is more preferable, and 98/2 to 70/30 is still more preferable.

The electrolyte of the present invention can contain silicon oxide and / or metal oxide because the photoelectric conversion efficiency of the photoelectric conversion element of the present invention is further improved.
This is considered to be because the arrangement of cations (for example, imidazolium ions) contained in the ionic liquid (A) described above is improved and the movement of electrons proceeds smoothly.

The silicon oxide that can be used in the electrolyte of the present invention is not particularly limited, and conventionally known ones can be used.
Specific examples of silicon oxide include fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, colloidal silica, and the like.

  As such silicon oxide, commercially available products can be used, and specifically, for example, Z1165MP (manufactured by Rodia), AEROSIL200 (manufactured by Deguss), AEROSIL300 (manufactured by Deguss) and the like can be used. it can.

On the other hand, the metal oxide that can be used in the electrolyte of the present invention is not particularly limited, and conventionally known metal oxides can be used.
Specific examples of the metal oxide include titanium oxide (titanium dioxide), tin oxide, zinc oxide, tungsten oxide, zirconium oxide, hafnium oxide, strontium oxide, vanadium oxide, niobium oxide, and the like. May be used alone or in combination of two or more.
Of these, titanium oxide, zinc oxide, niobium oxide, tungsten oxide, and zirconium oxide are preferable from the viewpoint of high photoelectric conversion capability.

In the present invention, the total content of the silicon oxide and / or metal oxide and the carbon material (B) and the other carbon material (C) optionally contained is the ionic liquid (A). The amount is preferably 10 to 50 parts by mass, more preferably 15 to 45 parts by mass, and still more preferably 20 to 40 parts by mass with respect to 100 parts by mass.
When the total content of the silicon oxide and / or metal oxide, the carbon material (B), and the other carbon material (C) optionally contained is within this range, iodine is substantially not included. Even higher energy conversion efficiency can be achieved.

  Furthermore, in the present invention, the silicon oxide and / or metal oxide (hereinafter referred to as “silicon oxide or the like” in this paragraph), the carbon material (B), and the other carbon materials optionally contained ( C) (hereinafter referred to as “carbon material etc.” in this paragraph) The content ratio (silicon oxide etc./carbon material etc.) is preferably 1/99 to 50/50. More preferably, it is -40/60.

From the viewpoint of further improving the photoelectric conversion efficiency of the photoelectric conversion element of the present invention, the electrolyte of the present invention can be added with a redox pair (redox pair).
As the redox couple, any one generally used or usable in a dye-sensitized solar cell can be used as long as the object of the present invention is not impaired.
Examples thereof include metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium salt; sulfur compounds of disulfide compounds and mercapto compounds; hydroquinone; quinone; and the like, and these may be used alone. Two or more kinds may be used in combination.

Moreover, the electrolyte of this invention can add inorganic salt and / or organic salt from a viewpoint of improving the short circuit current of the photoelectric conversion element of this invention.
Examples of inorganic salts and organic salts include alkali metal, alkaline earth metal salts, and the like. Specifically, lithium iodide, sodium iodide, potassium iodide, magnesium iodide, calcium iodide, Examples include lithium trifluoroacetate, sodium trifluoroacetate, lithium thiocyanate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, and lithium bis (trifluoromethanesulfonyl) imide. These may be used alone or in combination of two or more.
The amount of the inorganic salt or organic salt added is not particularly limited, and can be the same as before as long as the object of the present invention is not impaired.

Moreover, the electrolyte of this invention can add pyridines and benzimidazoles from a viewpoint of improving the open circuit voltage of the photoelectric conversion element of this invention.
Specifically, alkyl pyridines such as methyl pyridine, ethyl pyridine, propyl pyridine and butyl pyridine; alkyl imidazoles such as methyl imidazole, ethyl imidazole and propyl imidazole; alkyl such as methyl benzimidazole, ethyl benzimidazole and propyl benzimidazole Benzimidazoles; and the like. These may be used alone or in combination of two or more.
The addition amounts of pyridines and benzimidazoles are not particularly limited, and can be conventional as long as the object of the present invention is not impaired.

An organic solvent may be added to the electrolyte of the present invention. Specific examples thereof include carbonates such as ethylene carbonate and propylene carbonate; ethers such as ethylene glycol dialkyl ether and propylene glycol dialkyl ether; ethylene glycol monoalkyl. Alcohols such as ether and propylene glycol monoalkyl ether; Polyhydric alcohols such as ethylene glycol and propylene glycol; Nitriles such as propionitrile, methoxypropionitrile and cyanoethyl ether; Amides such as dimethylformamide and N-methylpyrrolidone Aprotic polar solvents such as dimethyl sulfoxide, sulfolane, etc., and these may be used alone or in combination of two or more.
The content of the organic solvent is not particularly limited, and can be conventional as long as the object of the present invention is not impaired.

The method for producing the electrolyte of the present invention is not particularly limited. For example, the ionic liquid (A) and the carbon material (B) described above, and other carbon materials (C), silicon oxide, metal oxides, and the like that are optionally contained. Mix well, using a ball mill, sand mill, pigment disperser, pulverizer, ultrasonic disperser, homogenizer, planetary mixer, Hobart mixer, roll, kneader, etc. at room temperature or under heating (for example, 40 to 150 ° C.) It can be produced by mixing and uniformly dispersing (kneading).
Here, for the mixing of the ionic liquid (A) and the carbon material (B) described above and other carbon materials (C), silicon oxide, metal oxides and the like that are optionally contained, an organic solvent (for example, , Toluene, etc.) may be used in combination, and the organic solvent may be distilled off in vacuo after mixing.
In addition, when the ionic liquid (A) and the carbon material (B) described above and other carbon materials (C), silicon oxide, metal oxides and the like that are optionally contained are mixed, the ionic liquid (A) is converted into the carbon. For the purpose of sufficiently impregnating the material (B), the carbon material (B) that has been finely pulverized by a known pulverizer such as a ball mill or a jet mill may be used. For the same purpose, the above-described ionic liquid (A) and carbon material (B) may be optionally contained in a mixture of other carbon material (C), silicon oxide, metal oxide or the like at room temperature or under heating. (For example, 40-150 degreeC) may perform a pressure reduction process.

In the present invention, when the electrolyte of the present invention contains the above-mentioned other carbon material (C), the above-described ionic liquid (A) and other carbon material (C) are mixed to form a dispersion ( For example, after obtaining a paste-like dispersion), it is preferable to prepare by mixing the carbon material (B) described above.
By preparing by such a method, the photoelectric conversion efficiency of the photoelectric conversion element of this invention becomes more favorable. This is because the other carbon material (C) is unevenly distributed in the ionic liquid (A), and the ionic liquid (A) that cannot be held by the carbon material (B) is acetylene black (C1) or boron-modified. It is considered that it contributes to the promotion of charge transfer together with acetylene black (C2), and the carbon material (C3) interacts with the cation of the ionic liquid (A) described above.

  Next, the photoelectric conversion element and the dye-sensitized solar cell of the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an example of the basic configuration of the photoelectric conversion element of the present invention.

  The photoelectric conversion element of the present invention includes a photoelectrode having a transparent conductive film and a metal oxide semiconductor porous film, a counter electrode disposed to face the photoelectrode, and the photoelectrode and the counter electrode. It is a photoelectric conversion element which has the electrolyte layer made.

<Photoelectrode>
For example, as shown in FIG. 1, the photoelectrode includes a transparent substrate 1, a transparent conductive film 2, and an oxide semiconductor porous film 3.
Here, the transparent substrate 1 preferably has good light transmittance. Specific examples thereof include a glass substrate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyphenylene sulfide, and cyclic olefin polymer. And resin substrates (films) such as polyethersulfone, polysulfone, polyetherimide, polyarylate, triacetylcellulose, and polymethylmethacrylate.

As the transparent conductive film 2, specifically, for example, conductive metal oxides such as tin oxide doped with antimony or fluorine, zinc oxide doped with aluminum or gallium, indium oxide doped with tin, etc. Is mentioned.
Moreover, it is preferable that the thickness of the transparent conductive film 2 is about 0.01 to 1.0 μm.
Furthermore, the method for providing the transparent conductive film 2 is not particularly limited, and examples thereof include a coating method, a sputtering method, a vacuum deposition method, a spray pyrolysis method, a chemical vapor deposition method (CVD), and a sol-gel method.

Next, the oxide semiconductor porous film 3 is obtained by applying a dispersion of oxide semiconductor fine particles on the transparent conductive film 2.
Specific examples of the oxide semiconductor fine particles include titanium oxide, tin oxide, zinc oxide, tungsten oxide, zirconium oxide, hafnium oxide, strontium oxide, vanadium oxide, niobium oxide, and the like. You may use independently and may use 2 or more types together.

The dispersion is obtained by mixing the oxide semiconductor fine particles and the dispersion medium with a dispersing machine such as a sand mill, a bead mill, a ball mill, a three roll mill, a colloid mill, an ultrasonic homogenizer, a Henschel mixer, or a jet mill.
The dispersion is preferably obtained by mixing with a disperser and then subjected to ultrasonic treatment using an ultrasonic homogenizer or the like immediately before use (coating). By performing ultrasonic treatment immediately before use, the photoelectric conversion efficiency of the photoelectric conversion element of the present invention becomes better. This is presumably because the above-described ionic liquid (A) is easily filled into the oxide semiconductor porous film formed using the dispersion liquid subjected to ultrasonic treatment immediately before use.
Furthermore, in order to prevent re-aggregation of the oxide semiconductor fine particles in the dispersion, acetylacetone, hydrochloric acid, nitric acid, a surfactant, a chelating agent, or the like may be added to the dispersion. Therefore, a polymer such as polyethylene oxide and polyvinyl alcohol, a cellulose-based thickener, or the like may be added.

  Examples of the dispersion include titanium oxide pastes SP100 and SP200 (both manufactured by Showa Denko KK), titanium oxide fine particles Ti-Nanoxide T (manufactured by Solaronics), Ti-Nanoxide D (manufactured by Solaronics), and Ti-Nanoxide T. / SP (manufactured by Solaronics), Ti-Nanoxide D / SP (manufactured by Solaronics), titania coating paste PECC01 (manufactured by Pexel Technologies), titania particle paste PST-18NR (JGC Catalysts & Chemicals), titania particle paste PST400C Commercial products such as (JGC catalyst conversion) can also be used.

As a method for applying the dispersion on the transparent conductive film, for example, a known wet film forming method can be used.
Specific examples of the wet film forming method include a screen printing method, an ink jet printing method, a roll coating method, a doctor blade method, a spin coating method, and a spray coating method.

In addition, after applying the dispersion onto the transparent conductive film, for the purpose of improving electronic contact between the fine particles, improving adhesion with the transparent conductive film, and improving film strength, heat treatment, chemical treatment, plasma, It is preferable to perform ozone treatment or the like.
As temperature of heat processing, it is preferable that it is 40 to 700 degreeC, and it is preferable that it is 40 to 650 degreeC. The time for the heat treatment is not particularly limited, but is usually about 10 seconds to 24 hours.
Specific examples of the chemical treatment include chemical plating treatment using a titanium tetrachloride aqueous solution, chemical adsorption treatment using a carboxylic acid derivative, and electrochemical plating treatment using a titanium trichloride aqueous solution.

<Counter electrode>
As shown in FIG. 1, the counter electrode is an electrode 5 disposed to face the photoelectrode 4. For example, a metal substrate, a glass substrate having a conductive film on the surface, a resin substrate, or the like can be used. .
As the metal substrate, metals such as platinum, gold, silver, copper, aluminum, indium, and titanium can be used. As the resin substrate, in addition to the substrate (film) exemplified as the transparent substrate 1 constituting the photoelectrode 4, a general resin substrate which is opaque or inferior in transparency can also be used.
As the conductive film provided on the surface, metals such as platinum, gold, silver, copper, aluminum, indium and titanium; carbon; tin oxide; tin oxide doped with antimony and fluorine; zinc oxide; doped with aluminum and gallium Zinc oxide; indium oxide doped with tin; conductive metal oxides such as; The thickness and formation method of the conductive film can be the same as those of the transparent conductive film 2 constituting the photoelectrode 4.

In the present invention, the counter electrode 5 may be an electrode in which a conductive polymer film is formed on a substrate or a conductive polymer film electrode.
Specific examples of the conductive polymer include polythiophene, polypyrrole, polyaniline, and the like.
As a method for forming a conductive polymer film on a substrate, a conductive polymer film is formed on a substrate from a polymer dispersion using a dipping method, a spin coating method, or the like that is usually known as a wet film formation method. be able to.
Examples of conductive polymer dispersions include polyaniline dispersions disclosed in JP-A-2006-169291, polythiophene derivative aqueous dispersions (Vitron P, manufactured by Bayer) which are commercially available products, Mitsubishi Rayon Co., Ltd. (Aquasave, polyaniline). Derivative aqueous solution) and the like can be used.
When the substrate is the conductive substrate, a conductive polymer film can be formed on the substrate by an electrolytic polymerization method in addition to the above method. Conductive polymer film electrode is a casting that is usually known as a wet film-forming method from a self-supporting film or a conductive polymer dispersion obtained by peeling off a conductive polymer film formed on an electrode by electrolytic polymerization. It is also possible to use a self-supporting film formed using a method or a spin coating method. The conductive polymer dispersion referred to here is a conductive polymer dispersion in which conductive polymer fine particles are dispersed in a solvent and a conductive polymer is dissolved in a solvent. A functional polymer dispersion.

<Electrolyte>
As shown in FIG. 1, the electrolyte layer is an electrolyte layer 6 provided between the photoelectrode 4 and the counter electrode 5, and the above-described electrolyte of the present invention is used in the photoelectric conversion element of the present invention.

  Since the photoelectric conversion element of the present invention uses the above-described electrolyte of the present invention, high energy conversion efficiency can be achieved without substantially containing iodine.

The dye-sensitized solar cell of the present invention is a kind of photoelectric conversion element in which a photosensitizing dye is supported on the photoelectrode constituting the photoelectric conversion element of the present invention described above.
Here, the photosensitizing dye is not particularly limited as long as it is a dye having absorption in the visible light region and / or the infrared light region, and a metal complex, an organic dye, or the like can be used.
Specifically, a ruthenium complex dye, a porphyrin dye, a phthalocyanine dye, a cyanine dye, a merocyanine dye, a xanthene dye or the like coordinated with a ligand such as a bipyridine structure or a terpyridine structure can be used. Although there is no particular limitation on the method of supporting, the dye is dissolved in, for example, water or alcohol, and the oxide semiconductor porous film 3 is immersed in the dye solution or the dye solution is applied to the oxide semiconductor porous film 3. It is supported by.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.

(Reference Example 1-5, Example 6-34, Comparative Examples 1 to 11)
<Preparation of electrolyte>
In a 30 mL mixing container, an ionic liquid A1 and the like shown in Table 1 below, toluene, and zirconia beads (diameter 3 mm) with a composition shown in Table 1 below and a bead mill (Rocking RM02, manufactured by Seiwa Giken Co., Ltd.) ) And stirred and mixed for 60 minutes.
Toluene was distilled off from the dispersion after mixing in vacuo to obtain an electrolyte.

<Preparation of dye-sensitized solar cell>
A titanium oxide paste Ti-Nanoxide D (manufactured by Solaronix) is applied onto transparent conductive glass (FTO glass, surface resistance 15Ω / □, manufactured by Nippon Sheet Glass Co., Ltd.), dried at room temperature, and then heated to 450 ° C. Was sintered for 30 minutes to produce a photoelectrode in which a porous titanium oxide film was formed on transparent conductive glass.
The produced photoelectrode was converted into a ruthenium complex dye (cis- (dithiocyanate) -N, N′-bis (2,2′-bipyridyl-4,4′-dicarboxylic acid) ruthenium (II) complex) (Ruthenium). It was immersed in an ethanol solution (concentration 3 × 10 ⁻⁴ mol / L) of 535-bisTBA (manufactured by Solaronix) for 4 hours.
Then, it wash | cleaned with acetonitrile, and what carried the sensitizing dye on the titanium oxide electrode of the photoelectrode by drying under nitrogen stream in the dark place was used as a photoelectrode.
The electrolyte prepared above is applied on the photoelectrode carrying the photosensitizing dye, and this is and a transparent conductive glass substrate (indium oxide doped with tin on the conductive surface, sheet resistance: 8Ω / □, manufactured by Nippon Sheet Glass Co., Ltd.) A dye-sensitized solar cell was obtained by pasting a platinum counter electrode having a platinum thin film having a thickness of about 100 nm formed on the surface thereof by sputtering and fixing it with a clip.

  The photoelectric conversion efficiency of the obtained dye-sensitized solar cell was measured and evaluated by the method shown below. The results are shown in Table 1.

<Photoelectric conversion efficiency>
As shown in FIG. 2, a solar simulator is used as a light source, and AM1.5 simulated sunlight is irradiated from the photoelectrode side with a light intensity of 100 mW / cm ² , and a current-voltage measuring device (Digital Source Meter 2400 manufactured by Keithley Instruments Co., Ltd.) ) To determine the conversion efficiency.

Each component in Table 1 is as follows.
Ionic liquid A1: 1-methyl-3-propylimidazolium iodide (manufactured by Tokyo Chemical Industry Co., Ltd.)
Carbon material B1: Activated carbon (NY1151, specific surface area: 1325 m ² / g, primary average particle size: 5 μm, specific resistance: 1.5 × 10 ⁻¹ Ω · cm, manufactured by Kuraray Chemical Co., Ltd.)
Carbon material B2: activated carbon (NK261, specific surface area: 2300 m ² / g, primary average particle diameter: 5 μm, specific resistance: 1.5 × 10 ⁻¹ Ω · cm, manufactured by Kuraray Chemical Co., Ltd.)
Carbon material C1-1: Acetylene black (denka black powder, specific surface area: 68 m ² / g, primary average particle size: 35 nm, specific resistance: 3 × 10 ⁻² Ω · cm, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Carbon material C2-1: Boron-modified acetylene black (Denka black BMAB, specific surface area: 50 m ² / g, primary average particle size: 35 nm, specific resistance: 1 × 10 ⁻² Ω · cm, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Carbon material C3-1: Acidic carbon black (Color Black FW1, pH: 4.5, primary average particle size: 13 nm, specific resistance: 5 × 10 ⁻¹ Ω · cm, manufactured by Degussa)
Carbon material C3-2: Special Black 5 (pH: 3.0, primary average particle size: 20 nm, specific resistance: 1.5 Ω · cm, manufactured by Degussa)
Carbon material C3-3: Toka Black # 8500F (pH: 5.5, primary average particle size: 14 nm, specific resistance: 5 × 10 ⁻¹ Ω · cm, manufactured by Tokai Carbon Co., Ltd.)
Carbon material C4-1: SAF (N134, nitrogen adsorption specific surface area: 151 m ^{2 /} g, pH: 7.3, average particle size: 19 nm, manufactured by Cabot Japan)
Carbon material C4-2: ISAF (N234, nitrogen adsorption specific surface area: 117 m ^{2 /} g, pH: 7.5, average particle size: 23 nm, manufactured by Cabot Japan)
Carbon material C4-3: HAF (N339, nitrogen adsorption specific surface area: 93 m ^{2 /} g, pH: 7.5, average particle size: 24 nm, manufactured by Tokai Carbon Co., Ltd.)
・ Silicon oxide: Precipitated silica (Z1165MP, manufactured by Rodia)
・ Titanium oxide: Fumed titanium oxide P25 (manufactured by Degussa)

As is clear from the results shown in Table 1, the electrolytes of Reference Examples 1 to 5 prepared so as to contain the ionic liquid (A) and the carbon material (B) at a specific ratio substantially contain iodine. Even without this, the photoelectric conversion efficiency was found to be sufficiently high at 4.3 to 4.9%. This is an unexpected result showing that it is superior to the electrolytes of Comparative Examples 3 to 7 prepared using acetylene black which is a conductive material.
On the other hand, the carbon material (B) with respect to 100 parts by mass of the electrolyte and ionic liquid (A) of Comparative Example 1 prepared by blending 5 parts by mass of the carbon material (B) with 100 parts by mass of the ionic liquid (A). It was found that the electrolyte of Comparative Example 2 prepared by blending 60 parts by mass of the compound had a low photoelectric conversion efficiency.

Moreover, even when it is a case where carbon material (C) is used together, the electrolytes of Comparative Examples 8 to 11 in which the content of the carbon material (B) with respect to 100 parts by mass of the ionic liquid (A) deviates from 10 to 50 parts by mass is used. Even if the total content of the carbon material (B) and the carbon material (C) was 10 to 50 parts by mass, the photoelectric conversion efficiency remained around 4.0%.
On the other hand, the electrolytes of Examples 6 to 32 prepared so as to contain the ionic liquid (A) and the carbon material (B) at a specific ratio and further contain the carbon material (C) substantially contain iodine. Even if it does not contain, it turned out that photoelectric conversion efficiency becomes high enough with 5.0% or more.
In particular, the electrolytes of Examples 10 and 15 prepared using boron-modified acetylene black as the carbon material (C) have an even higher photoelectric conversion efficiency of 6.0% or more even when substantially free of iodine. As can be seen, the electrolytes of Examples 19 to 28 prepared using acidic carbon black as the carbon material (C) have a sufficiently high photoelectric conversion efficiency of 5.5% or more even when substantially free of iodine. I understood that.
In addition, although all the electrolytes of Examples 6 to 32 have a total content of the carbon material (B) and the carbon material (C) of 10 to 50 parts by mass with respect to 100 parts by mass of the ionic liquid (A). , Examples 6 to 23 in which the content ratio [carbon material (B) / carbon material (C)] of the carbon material (B) and the carbon material (C) is 99.9 / 0.1 to 60/40 26-28 and 30-32 electrolytes were found to tend to have higher photoelectric conversion efficiency.

  In addition, the electrolytes of Examples 33 and 34 prepared so as to contain the ionic liquid (A) and the carbon material (B) at a specific ratio and further contain silicon oxide or titanium oxide are substantially free of iodine. However, the photoelectric conversion efficiency was found to be sufficiently high at 5.9% or more.

1: transparent substrate 2: transparent conductive film 3: oxide semiconductor porous film 4: photoelectrode 5: counter electrode 6: electrolyte layer 11: transparent substrate 12: transparent conductive film (ITO, FTO)
13: Metal oxide 14: Electrolyte 15: Platinum thin film 16: Transparent conductive film (ITO, FTO)
17: Substrate 18: Counter electrode

Claims (11)

Containing an ionic liquid (A) and a carbon material (B) having a specific surface area of 1000 to 3500 m ² / g,
The content of the carbon material (B) is Ri 10-50 parts by der respect to the ionic liquid (A) 100 parts by mass of,
Further, as other carbon material (C) other than the carbon material (B), acetylene black, boron-modified acetylene black, a carbon material having a pH of 2 to 6 measured by a pH measurement method defined in JIS Z8802, and nitrogen the photoelectric conversion element for electrolyte you containing any one or more of adsorption specific surface area is selected from the group consisting of higher carbon black 90m ² / g.   The electrolyte for photoelectric conversion elements according to claim 1, wherein the carbon material (B) has a primary average particle diameter of 0.5 to 120 μm. The electrolyte for photoelectric conversion elements according to claim 1 or 2, wherein the ionic liquid (A) has a cation represented by the following formula (1) or (2).
(In the formula (1), R ¹ represents a hydrocarbon group which may contain a hetero atom having 1 to 20 carbon atoms, having a substituent group which may contain a hetero atom having 1 to 20 carbon atoms R ² and R ³ each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms and may contain a hetero atom, provided that the nitrogen atom contains a double bond. during R ³ is absent. equation (2), Q is a nitrogen atom, an oxygen atom, a phosphorus atom or a sulfur ^{atom, R 4, R 5, R} 6 and R ⁷ each independently represent a hydrogen atom or a C Represents a hydrocarbon group of formulas 1 to 8, and may contain a hetero atom, provided that when Q is an oxygen atom or a sulfur atom, R ⁷ does not exist.   The electrolyte for photoelectric conversion elements according to claim 3, wherein the ionic liquid (A) has iodine ions as anions. The electrolyte for photoelectric conversion elements according to any one of claims 1 to 4, wherein the carbon material having a pH of 2 to 6 has a primary average particle diameter of 0.010 to 0.050 µm. The total content of the carbon material (B) and the other carbon material (C) is any one of the preceding claims 10 to 50 parts by mass with respect to the ionic liquid (A) 100 parts by mass of The electrolyte for photoelectric conversion elements described in 1. The content ratio [carbon material (B) / other carbon material (C)] of the carbon material (B) and the other carbon material (C) is 99.9 / 0.1-60 / 40. The electrolyte for photoelectric conversion elements according to any one of claims 1 to 6 . In after obtaining a dispersion by mixing the ionic liquid (A) and the other carbon material (C), according to claim 1 which is prepared by mixing the carbonaceous material (B) Electrolyte for photoelectric conversion element. Furthermore, the electrolyte for photoelectric conversion elements in any one of Claims 1-8 containing a silicon oxide and / or a metal oxide. A photoelectrode having a transparent conductive film and a metal oxide semiconductor porous film;
A counter electrode disposed to face the photoelectrode;
An electrolyte layer disposed between the photoelectrode and the counter electrode;
The electrolyte layer, the photoelectric conversion element is a photoelectric conversion element for electrolyte according to any one of claims 1-9. A dye-sensitized solar cell obtained by supporting a photosensitizing dye on the photoelectrode according to claim 10 .