WO2014076896A1

WO2014076896A1 - Redox pair, and photoelectric conversion element produced using same

Info

Publication number: WO2014076896A1
Application number: PCT/JP2013/006439
Authority: WO
Inventors: 恭輝齊藤; 温彦日比野; 一正船曳
Original assignee: 国立大学法人岐阜大学; 第一工業製薬株式会社
Priority date: 2012-11-15
Filing date: 2013-10-30
Publication date: 2014-05-22
Also published as: CN104813423B; JP5960033B2; KR102089819B1; JP2014099364A; TW201422595A; CN104813423A; KR20150082274A

Abstract

Provided are: a redox pair which does not have strong absorption in a visible region unlike a iodine redox pair, can be sealed readily, and has high performance; and a photoelectric conversion element which is produced using the redox pair and has high practical availability. A redox pair composed of a compound represented by general formula (1) and a compound represented by general formula (2) is used. In general formula (1), A represents Li, K, Na, an ammonium compound, an imidazolium compound or a pyrrolidinium compound. In general formulae (1) and (2), R¹ represents a linear alkyl group having 4 to 8 carbon atoms, wherein multiple R¹'s are the same as or different from each other or some or all of the multiple R¹'s are different from each other. AA General formula

Description

Redox couple and photoelectric conversion device using the same

The present invention relates to an organic redox couple and a photoelectric conversion element using the same.

In recent years, various solar cells have been proposed as photoelectric conversion elements that convert light energy into electrical energy. Among them, the dye-sensitized solar cell announced in 1991 by Gretzel et al. At the University of Lausanne in Switzerland in “Nature” 1991, 353, p737-740, etc. is low in cost because the materials and processes used are low. Practical use is expected as a solar cell.

A dye-sensitized solar cell generally includes a semiconductor electrode having a photoelectric conversion layer made of a semiconductor having a dye adsorbed on a conductive substrate, and a catalyst layer provided on the conductive substrate provided facing the semiconductor electrode. And an electrolyte layer held between the semiconductor electrode and the counter electrode.

The electrolyte of the dye-sensitized solar cell generally uses an iodine redox couple dissolved in an organic solvent. Iodine-based redox couples have excellent performance, such as high ion conductivity and a high rate of reducing oxidized dyes, while low reactivity on the conductive glass surface and titanium oxide surface of the working electrode. ing.

However, when an iodine-based redox couple is used, it is difficult to seal the element due to the high sublimation property of iodine, which causes a decrease in element durability under high temperature conditions. In addition, since iodine has high corrosiveness to many metals, there is a problem that the metal that can be used for the element substrate is limited, and an expensive substrate such as conductive glass must be used. In particular, in the case of a large area element, a metal current collector is often provided on the substrate for higher performance. In that case, in order to prevent corrosion of the metal current collector, contact between the electrolyte and the current collector is prevented. Processing is required, and the work process becomes complicated, and the effective area of the element is reduced.

In addition, iodine-based redox couples have strong absorption in the visible light range, and when high-viscosity solvents such as ionic liquids are used, it is necessary to increase the concentration of iodine-based redox couples in order to operate sufficiently as a solar cell element. As a result, light absorption of the dye is hindered, causing performance degradation, and when using various dyes to emphasize the colorfulness of solar cells, especially in the case of blue elements, the color of iodine It is a hindrance and it cannot be said that it is suitable for element design.

Thus, although the iodine-based redox couple has high performance as a redox couple, it also has drawbacks, so a redox couple that replaces the iodine-based system is required, and several studies have been made ( For example, Non-Patent Documents 1 to 7, Patent Documents 1 and 2).

Non-Patent Documents 1 to 3 have proposed using a cobalt complex as a redox pair. Although the performance is equivalent to that of an iodine-based redox couple under weak light conditions, the movement speed of the redox couple is slow due to the large molecular size, and the performance is reduced to about half under simulated sunlight irradiation conditions. Non-Patent Document 4 reports good performance by using a redox counter electrolytic solution in which a dye having a specific structure and a cobalt complex are dissolved in a low-viscosity and high-volatile organic solvent. There is no mention of the property, and since a highly volatile organic solvent is used, high durability cannot be expected. Further, the cobalt complex is expensive with respect to iodine, which is not practical.

Non-Patent Documents

5 and 6 have proposed using (SCN) ₂ / SCN ⁻ and (SeCN) ₂ / SeCN ⁻ as the redox pair. Although (SCN) ₂ / SCN ⁻ operates as a redox _couple, it can provide only half or less of the performance of an iodine-based redox _couple . (SeCN) ₂ / SeCN ⁻ shows higher performance than that, but has a problem in safety and cannot be said to have high practicality. Other redox pairs that can be used for photoelectric conversion elements other than iodine include Br ₂ / Br ⁻ , Fe (CN) ₆ ⁴⁻ / Fe (CN) ₆ ³⁻ , Fe ²⁺ / Fe ³⁺ , S ²⁻ / S. _{^{^{_{^{n 2-, Se 2- / Se n}}}}} 2-, V 2+ / V 3+, quinone / hydroquinone such as, but are exemplified, performance, is stable, problems such as safety, have performance obtained comparable to iodine Absent.

As shown in

Patent Documents

1 and 2, the applicants use a sulfide-based compound that absorbs less light in the visible light region as a redox pair, and use a conductive polymer as a counter electrode catalyst, thereby being effective as a photoelectric conversion element. It is clear that it works. Non-Patent Document 7 achieves high photoelectric conversion performance by using a sulfide-based redox couple and an organic solvent as an electrolyte.

However, when a volatile organic solvent such as acetonitrile and ethylene carbonate as shown in Non-Patent Document 7 is used as the electrolyte solution of the dye-sensitized solar cell, it is difficult to seal the electrolyte solution, which is practical. It is difficult to obtain element durability. Therefore, in many cases, an ionic liquid having very low volatility is used as an electrolyte solvent. However, since the ionic liquid has a higher viscosity than a general volatile organic solvent, the device performance is organic as described in Patent Document 1. The problem is that it is lower than the solvent electrolyte.

In addition, in the sulfide compound having a thiadiazole skeleton as the redox couple described in Patent Document 1, the disulfide compound that is an oxidant of the redox couple has particularly low solubility in an electrolyte solvent such as an ionic liquid and low volatility. However, when a solvent such as an ionic liquid having a high viscosity is used, there is a problem that the device performance deteriorates. In addition, when the concentration of the redox couple is increased, there is a problem that the stability of the redox itself is lowered.

Further, the sulfide compound having a tetrazole skeleton as the redox pair described in Patent Document 2 has improved solubility and improved solar cell element performance as compared with the sulfide compound of Patent Document 1, but the solubility of the oxidized disulfide compound is improved. The problem remained that was still inadequate.

Further, Non-Patent Document 7 shows that a tetramethylammonium salt of a sulfide compound is used as a reductant of a redox pair. Even in this case, a satisfactory element is insufficient in solubility in an ionic liquid. There is a problem that performance cannot be demonstrated. Accordingly, there is a need for an iodine substitute electrolyte solution that does not have sublimation property or light absorption property in the visible light region, has high solubility in an electrolyte solution solvent, and is stable and high performance in the solvent.

JP 2008-016442 A WO2012 / 096170A1

The present invention has been made in view of the above points, and has higher transparency than iodine-based redox couples, that is, less absorption in the visible light region, easy sealing, and high-performance redox couples. And a highly practical photoelectric conversion element using the redox couple thereof.

In order to solve the above problems, the redox pair of the present invention is composed of a compound represented by the general formula (1) and a compound represented by the general formula (2).

In the general formula (1), A is Li, K, or Na, or an ammonium compound represented by the general formula (3), an imidazolium compound represented by the general formula (4), or a general formula (5). The pyrrolidinium compound is shown. R ¹ in the general formula (1) and the general formula (2) represents a linear alkyl group having 4 to 8 carbon atoms, and the plurality of R ¹ are the same or partly or completely different from each other. .

In the general formulas (3) to (5), R ² represents an alkyl group having 1 to 12 carbon atoms, and R ³ represents H or a methyl group. The plurality of R ² are the same as each other or part or all of them are different.

Moreover, the photoelectric conversion element of the present invention is a photoelectric conversion element comprising a semiconductor electrode, a counter electrode, and an electrolyte layer held between these two electrodes, and the electrolyte layer comprises the redox pair of the present invention. It is assumed that the counter electrode contains a catalyst having catalytic activity for this redox pair.

In the above photoelectric conversion element, the electrolyte layer may contain an ionic liquid having a bis (fluorosulfonyl) imide anion represented by the following formula (6).

The catalyst contained in the counter electrode may be a conductive polymer containing a polymer of 3,4-ethylenedioxythiophene or a derivative thereof.

The photoelectric conversion device of the present invention has photoelectric conversion efficiency and stability comparable to devices using conventional iodine-based redox couples, and solves the coloring problem that was a weak point of conventional iodine-based redox couples. be able to. Specifically, since the redox couple of the present invention does not have strong absorption in the visible light region, not only the design of the device is improved, but also the ionic liquid is dissolved in a low-volatile ionic liquid at a high concentration. Even when is used as a solvent, the device performance does not deteriorate due to the light absorption of the electrolyte layer as seen in the iodine-based redox couple. Accordingly, it is possible to provide a highly practical photoelectric conversion element.

It is a schematic cross section which shows the basic structure of the photoelectric conversion element which concerns on embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an example of the photoelectric conversion element 10 of the present invention.

In FIG. 1, reference numeral 1 is a transparent substrate, reference numeral 2 is a transparent conductive film, reference numeral 3 is a porous metal oxide semiconductor layer, reference numeral 4 is a sensitizing dye, reference numeral 5 is an electrolyte layer, reference numeral 6 is a catalyst layer, reference numeral 7 is Reference numeral 6 denotes an electrode substrate, reference numeral 8 denotes an electrode substrate, and reference numeral 9 denotes a counter electrode.

As shown in FIG. 1, a porous metal oxide semiconductor layer 3 is formed on the surface of an electrode substrate 8 comprising a transparent substrate 1 and a transparent conductive film 2 formed thereon, and this porous metal oxide semiconductor is further formed. The sensitizing dye 4 is adsorbed on the surface 3. And the counter electrode 9 in which the catalyst layer 6 was formed on the surface of the electrode base material 7 is arrange | positioned through the electrolyte layer 5 of this invention, and the photoelectric conversion element 10 is formed. Hereinafter, a suitable form is demonstrated about each structural material of this photoelectric conversion element 10. FIG.

[Transparent substrate]
As the transparent substrate 1 constituting the electrode substrate 8, one that transmits visible light can be used, and transparent glass can be suitably used. Moreover, what processed the glass surface and scattered incident light can also be used. Moreover, not only glass but a plastic plate, a plastic film, etc. can be used if it transmits light.

The thickness of the transparent substrate 1 is not particularly limited because it varies depending on the shape of the photoelectric conversion element 10 and usage conditions. For example, when glass or plastic is used, 1 mm to 1 cm is considered in consideration of durability during actual use. When a plastic film or the like is used, the thickness is preferably about 1 μm to 1 mm.

[Transparent conductive film]
As the transparent conductive film 2, a material that transmits visible light and has conductivity can be used. An example of such a material is a metal oxide. Although not particularly limited, for example, tin oxide doped with fluorine (hereinafter abbreviated as “FTO”), indium oxide, a mixture of tin oxide and indium oxide (hereinafter abbreviated as “ITO”), antimony, and the like. Tin oxide, zinc oxide and the like doped with can be preferably used.

Further, an opaque conductive material can also be used if visible light is transmitted by a treatment such as dispersion. Such materials include carbon materials and metals. Although it does not specifically limit as a carbon material, For example, graphite (graphite), carbon black, glassy carbon, a carbon nanotube, fullerene, etc. are mentioned. Further, the metal is not particularly limited, and examples thereof include platinum, gold, silver, ruthenium, copper, aluminum, nickel, cobalt, chromium, iron, molybdenum, titanium, tantalum, and alloys thereof.

Therefore, the electrode substrate 8 can be formed by providing a conductive material made of at least one of the above-described conductive materials on the surface of the transparent substrate 1. Alternatively, it is also possible to incorporate the conductive material into the material constituting the transparent substrate 1 and integrate the transparent substrate 1 and the transparent conductive film 2 to form the electrode substrate 8.

As a method of forming the transparent conductive film 2 on the transparent substrate 1, when using a metal oxide, there are a liquid layer method such as a sol-gel method, a gas phase method such as sputtering or CVD, and a coating of a dispersion paste. Moreover, when using an opaque electroconductive material, the method of fixing powder etc. with a transparent binder etc. is mentioned.

Further, in order to integrate the transparent substrate 1 and the transparent conductive film 2, there is a method of mixing the conductive film material as a conductive filler when the transparent substrate 1 is molded.

The thickness of the transparent conductive film 2 is not particularly limited because the conductivity varies depending on the material to be used. However, in the glass with FTO film generally used, it is 0.01 μm to 5 μm, preferably 0.1 μm to 1 μm. It is. Further, the required conductivity varies depending on the area of the electrode to be used, and a wider electrode is required to have a lower resistance, but is generally 100Ω / □ or less, preferably 10Ω / □ or less, more preferably 5Ω. / □ or less.

The thickness of the electrode substrate 8 composed of the transparent substrate 1 and the transparent conductive film 2 or the electrode substrate 8 in which the transparent substrate 1 and the transparent conductive film 2 are integrated is the shape and use of the photoelectric conversion element 10 as described above. Although it is not particularly limited because it varies depending on conditions, it is generally about 1 μm to 1 cm.

[Porous metal oxide semiconductor]
Examples of the porous metal oxide semiconductor 3 include, but are not limited to, titanium oxide, zinc oxide, tin oxide, and the like. In particular, titanium dioxide and further anatase type titanium dioxide are suitable.

Further, it is desirable that the metal oxide has few grain boundaries in order to reduce the electric resistance value. In order to adsorb more sensitizing dye, the semiconductor layer preferably has a large specific surface area, specifically 10 to 200 m ² / g. Further, in order to increase the light absorption amount of the sensitizing dye, the particle size of the oxide to be used is widened to scatter light, or large oxide semiconductor particles having a particle size of about 300 to 400 nm are formed in the porous layer. It is desirable to provide it as a reflective layer on top.

Such a porous metal oxide semiconductor layer 3 is not particularly limited and can be provided on the transparent conductive film 2 by a known method. For example, there are a sol-gel method, dispersion paste application, electrodeposition and electrodeposition.

The thickness of the semiconductor layer 3 is not particularly limited because the optimum value varies depending on the oxide to be used, but is usually 0.1 μm to 50 μm, preferably 3 to 30 μm.

[Sensitizing dye]
As the sensitizing dye 4, any dye that can be excited by sunlight and can inject electrons into the metal oxide semiconductor 3 can be used, and a dye generally used in a photoelectric conversion element can be used. In order to improve the light intensity, it is desirable that the absorption spectrum overlaps with the sunlight spectrum in a wide wavelength range and has high light resistance.

The sensitizing dye 4 is not particularly limited, but is preferably a ruthenium complex, particularly a ruthenium polypyridine-based complex, and more preferably a ruthenium complex represented by Ru (L) ₂ (X) ₂ . Here, L is 4,4′-dicarboxy-2,2′-bipyridine, or a quaternary ammonium salt thereof, and a polypyridine-based ligand into which a carboxyl group is introduced, and X is SCN, Cl, CN. Examples thereof include bis (4,4′-dicarboxy-2,2′-bipyridine) diisothiocyanate ruthenium complex.

Examples of other dyes include metal complex dyes other than ruthenium, such as iron complexes and copper complexes. Further examples include organic dyes such as cyan dyes, porphyrin dyes, polyene dyes, coumarin dyes, cyanine dyes, squaric acid dyes, styryl dyes, eosin dyes, and indoline dyes.

These dyes desirably have a bonding group with the metal oxide semiconductor 3 in order to improve the electron injection efficiency into the metal oxide semiconductor 3. The bonding group is not particularly limited, but a carboxyl group, a sulfonic acid group, a hydroxyl group and the like are desirable.

In addition, by combining a dye that absorbs a red region or a near infrared region with the visible light transparent electrolyte of the present invention, a blue or transparent photoelectric conversion element can be produced, and uses that require colorfulness, etc. The use application of the device can be increased.

Examples of the solvent used for dissolving the dye include alcohols such as ethanol, nitrogen compounds such as acetonitrile, ketones such as acetone, ethers such as diethyl ether, halogenated aliphatic hydrocarbons such as chloroform, hexane Aliphatic hydrocarbons such as benzene, aromatic hydrocarbons such as benzene, and esters such as ethyl acetate. The concentration of the dye in the solution can be appropriately adjusted depending on the kind of the dye and the solvent to be used. In order to sufficiently adsorb on the semiconductor surface, it is desirable that the concentration is somewhat high. For example, a concentration of 4 × 10 ⁻⁵ mol / L or more is desirable.

The method for adsorbing the sensitizing dye 4 to the porous metal oxide semiconductor 3 is not particularly limited. For example, the porous metal is dissolved in a solution in which the dye is dissolved at room temperature and atmospheric pressure. A method of immersing the electrode substrate 8 on which the oxide semiconductor 3 is formed may be mentioned. The immersion time is preferably adjusted as appropriate so that the monomolecular film of the sensitizing dye 4 is uniformly formed on the semiconductor layer 3 according to the type of semiconductor, dye, solvent, and dye concentration used. In addition, adsorption | suction can be performed efficiently by performing the immersion under a heating.

[Electrolyte layer]
The electrolyte layer 5 used in the present invention includes a redox couple composed of a compound represented by the following general formula (1) and a compound represented by the general formula (2). In addition, the compound shown by General formula (1) is a reduced form, and the compound shown by General formula (2) is an oxidant.

In general formula (1), A is Li, K, or Na, or an ammonium compound represented by the following general formula (3), an imidazolium compound represented by general formula (4), or general formula (5) The pyrrolidinium compound represented by these is shown. R ¹ in the general formulas (1) and (2) represents a linear alkyl group having 4 to 8 carbon atoms, and the plurality of R ¹ may be the same or different from each other.

In the general formulas (3) to (5), R ² represents an alkyl group having 1 to 12 carbon atoms, and R ³ represents H or a methyl group. A plurality of R ² may be the same as or different from each other.

Specific examples of the compound represented by the formula (1) include 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: lithium salt (Li-BTZT), 1-n-butyl-5 -Mercapto-1,2,3,4-tetrazole: potassium salt (K-BTTZT), 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: tetramethylammonium salt (TMA-BTZT) 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: tetraethylammonium salt (TEA-BTZT), 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: Tetrapropylammonium salt (TPA-BTZT), 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: Tetrabutylammonium salt (TBA-BTZT) 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: tetrahexylammonium salt (THA-BTZT), 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: Trimethylpropylammonium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: Trimethylbutylammonium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: Trimethylhexylammonium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: Triethylpropylammonium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: Triethylbutylammonium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: triethylhex Rupropylammonium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazolium salt (EMIm-BTZT), 1-n-butyl-5-mercapto -1,2,3,4-tetrazole: 1,2-dimethyl-3-propylimidazolium salt (DMPIm-BTZT), 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1 -Methyl-1-propylpyrrolidinium salt (MPPy-BTZT), 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-propylimidazolium salt, 1-n -Butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-butylimidazolium salt, 1-n-butyl-5-mercapto-1,2,3,4-te Tolazole: 1-methyl-3-hexylimidazolium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1,2-dimethyl-3-butylimidazolium salt, 1-n- Butyl-5-mercapto-1,2,3,4-tetrazole: 1,2-dimethyl-3-hexylimidazolium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1 -Methyl-1-ethylpyrrolidinium salt, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-1-butylpyrrolidinium salt, 1-n-butyl-5 -Mercapto-1,2,3,4-tetrazole: 1-methyl-1-hexylpyrrolidinium salt and the like.

Examples of the compound represented by the formula (2) include 5,5′-dithiobis (1-n-butyl-1H-tetrazole) (BTZT) ₂ .

Further, the solvent for dissolving the redox couple can be used without particular limitation as long as it is a compound capable of dissolving the redox couple, and can be arbitrarily selected from a non-aqueous organic solvent, a room temperature molten salt, a protic organic solvent, and the like. For example, as organic solvents, nitrile compounds such as acetonitrile, methoxyacetonitrile, valeronitrile, 3-methoxypropionitrile, lactone compounds such as γ-butyllactone and valerolactone, carbonate compounds such as ethylene carbonate and propylene carbonate, dioxane and diethyl ether And ethers such as ethylene glycol dialkyl ether, alcohols such as methanol and ethanol, and dimethylformamide and imidazoles. Among them, acetonitrile, valeronitrile, 3-methoxypropionitrile, methoxyacetonitrile, propylene carbonate, etc. It can be used suitably.

As the solvent for dissolving the redox couple, a solvent containing an ionic liquid having a bis (fluorosulfonyl) imide anion represented by the formula (6) is preferably used.

Specific examples of the ionic liquid include 1-methyl-3-ethylimidazolium bis (fluorosulfonyl) imide, 1,3-dimethylimidazolium bis (fluorosulfonyl) imide, 1-methyl-3-propylimidazolium bis (fluoro Sulfonyl) imide, 1-methyl-3-butylimidazolium bis (fluorosulfonyl) imide, 1-methyl-3-hexylimidazolium bis (fluorosulfonyl) imide, 1,2-dimethyl-3-propylimidazolium bis (fluoro Sulfonyl) imide, 1,2-dimethyl-3-butylimidazolium bis (fluorosulfonyl) imide, 1,2-dimethyl-3-hexylimidazolium bis (fluorosulfonyl) imide, 1-methyl-1-ethylpyrrolidinium Bis (fluorosulfo ) Imide, 1-methyl-1-propylpyrrolidinium bis (fluorosulfonyl) imide, 1-methyl-1-butylpyrrolidinium bis (fluorosulfonyl) imide, 1-methyl-1-hexylpyrrolidinium bis ( Fluorosulfonyl) imide and the like.

The above-mentioned oxidation-reduction pair and ionic liquid can be commercially available, or can be synthesized from commercially available materials by a known method.

When an organic solvent such as a nitrile compound is used as the solvent, the concentration of the compound represented by the general formula (1) or the general formula (2) in the electrolyte layer (solvent) is 0.01 mol / L to 2 mol / L. It is preferable. If the concentration of the compound represented by the general formula (1) or the general formula (2) is less than 0.01 mol / L, the charge transporting ability of the redox pair is insufficient, and the current value of the device may be reduced. When it exceeds 2 mol / L, the viscosity of the electrolytic solution increases, so that the charge transporting ability of the redox couple is lowered, and the device performance may be lowered.

When the ionic liquid as described above is used as a solvent, the concentration of the compound represented by the general formula (1) in the electrolyte layer (solvent) is preferably 0.5 mol / L or more, preferably 0.5 to 3 mol. / L is more preferable. When the concentration of the compound represented by the general formula (1) is less than 0.5 mol / L, the charge transport ability of the redox couple is insufficient, and the current value of the device may be reduced. In addition, since the viscosity of the electrolytic solution is increased, the charge transport capability of the redox couple may be reduced, and the device performance may be reduced.

When the ionic liquid is used as a solvent, the concentration of the compound represented by the general formula (2) in the electrolyte layer (solvent) is preferably 0.5 mol / L or more, and preferably 0.5 to 2 mol / L. More preferably. If the concentration of the compound represented by the general formula (2) is less than 0.5 mol / L, the charge transport capability of the redox couple is insufficient, and the current value of the device may be reduced. If the concentration exceeds 2 mol / L In addition, since the viscosity of the electrolytic solution is increased, the charge transport capability of the oxidation-reduction pair is decreased, and the device performance may be decreased.

The lower limit of the ratio (molar ratio) of the compound represented by the general formula (2) to the compound represented by the general formula (1) is preferably 0.8 or more, more preferably 1 or more. More preferably, it is 2 or more. Further, the upper limit is preferably 5 or less, and more preferably 3 or less.

In the electrolyte layer 5, a supporting electrolyte, an additive, and the like can be further added as necessary without departing from the object of the present invention and without impairing the characteristics of the electrolyte layer. Examples of the supporting electrolyte include lithium salts, imidazolium salts, and quaternary ammonium salts. Examples of the additive include bases such as t-butylpyridine, N-methylimidazole, N-methylbenzimidazole and N-methylpyrrolidone, and thiocyanates such as guanidinium thiocyanate. Moreover, it can also be gelatinized physically or chemically by adding a suitable gelling agent.

[Counter electrode]
The counter electrode 9 has a structure in which the catalyst layer 6 is formed on the surface of the electrode substrate 7. Since this electrode base material 7 is used as a support and current collector of the catalyst layer 6, it is preferable that the surface portion has conductivity.

As such a material, for example, a conductive metal or metal oxide, a carbon material, a conductive polymer, or the like is preferably used. Examples of the metal include platinum, gold, silver, ruthenium, copper, aluminum, nickel, cobalt, chromium, iron, molybdenum, titanium, tantalum, and alloys thereof. Although it does not specifically limit as a carbon material, For example, graphite (graphite), carbon black, glassy carbon, a carbon nanotube, fullerene etc. are mentioned. Further, when a metal oxide such as FTO, ITO, indium oxide, zinc oxide or antimony oxide is used, the amount of incident light to the sensitizing dye layer 4 can be increased because it is transparent or translucent.

It should be noted that an insulator such as glass or plastic can be used as long as at least the surface of the electrode substrate 7 is treated. As a treatment method for maintaining conductivity in such an insulator, a method of covering a part or the entire surface of the insulating material with the above-described conductive material, for example, when using a metal, plating, electrodeposition, etc. In addition, a gas phase method such as a sputtering method or a vacuum deposition method is used. When a metal oxide is used, a sol-gel method or the like can be used. Moreover, the method of mixing with an insulating material using 1 type or multiple types of the said powder of an electroconductive material, etc. is mentioned.

Furthermore, even when an insulating material is used as the base material 7 of the counter electrode 9, the catalyst layer 6 is provided on the base material 7, so that the catalyst layer 6 can be used alone as a current collector and a catalyst. Both of these functions can be fulfilled and can be used as the counter electrode 9.

The shape of the electrode substrate 7 is not particularly limited because it can be changed according to the shape of the photoelectric conversion element 10 used as the catalyst electrode, and may be a plate shape or a film shape that can be curved. Furthermore, although the electrode base material 7 may be transparent or opaque, it is possible to increase the amount of light incident on the sensitizing dye layer 4 and, in some cases, to improve the design, so that it may be transparent or translucent. desirable.

In general, glass with an FTO film, PET with an ITO film, and a PEN film with an ITO film are used as the electrode substrate 7. However, since the conductivity differs depending on the material used, the thickness of the conductive layer is particularly limited. Not. For example, for FTO-coated glass, the thickness is 0.01 μm to 5 μm, preferably 0.1 μm to 1 μm.

Further, the required conductivity varies depending on the area of the electrode to be used, and a wider electrode is required to have a lower resistance, but is generally 100Ω / □ or less, preferably 10Ω / □ or less, more preferably 5Ω. / □ or less.

The thickness of the electrode substrate 7 is not particularly limited because it varies depending on the shape and use conditions of the photoelectric conversion element 10 as described above, but is generally about 1 μm to 1 cm.

The catalyst layer 6 is not particularly limited as long as it has electrode characteristics capable of promptly proceeding with a reduction reaction for reducing the oxidized form of the redox couple in the electrolyte to a reduced form. , Heat treated materials, platinum catalyst electrodes deposited with platinum, carbon materials such as activated carbon, glassy carbon and carbon nanotubes, inorganic sulfur compounds such as cobalt sulfide, conductive polymers such as polythiophene, polypyrrole and polyaniline, etc. Of these, a conductive polymer catalyst is preferably used.

Preferable specific examples of the monomer constituting the conductive polymer catalyst used in the present invention include a thiophene compound represented by the following general formula (7).

In the general formula (7), R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl or alkoxy group having 1 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyano group, a thiocyano group, a halogen atom. A group, a nitro group, an amino group, a carboxyl group, a sulfo group, or a phosphonium group, R ⁴ and R ⁵ may be linked to form a ring.

More specifically, thiophene, tetradecylthiophene, isothianaphthene, 3-phenylthiophene, 3,4-ethylenedioxythiophene and their derivatives can be preferably used, and among them, 3,4-ethylenedioxythiophene and The derivative can be preferably used. Examples of derivatives of 3,4-ethylenedioxythiophene include hydroxymethyl-3,4-ethylenedioxythiophene, aminomethyl-3,4-ethylenedioxythiophene, hexyl-3,4-ethylenedioxythiophene, and octyl. -3,4-ethylenedioxythiophene. In addition, these thiophene compounds may be used individually by 1 type, and the conductive polymer catalyst layer 6 may be formed using 2 or more types.

The monomer used to form the conductive polymer catalyst layer 6 is preferably one having a conductivity of 10 ⁻⁹ S / cm or more as a polymerized film.

In addition, it is desirable to add a dopant to the conductive polymer catalyst layer 6 in order to improve conductivity. As this dopant, a known material can be used without any particular limitation.

Specific examples of the dopant include halogen anions such as iodine, bromine and chlorine, hexafluorolin, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron, halide anions such as perchloric acid, methanesulfonic acid, dodecylsulfonic acid and the like. Alkyl group-substituted organic sulfonate anions, cyclic sulfonate anions such as camphor sulfonate, benzene sulfonate, para-toluene sulfonate, dodecyl benzene sulfonate, benzene disulfonate, etc. Alkyl group substituted or unsubstituted anions of naphthalenesulfonic acid substituted with sulfonic acid groups 1 to 3, such as 2-naphthalenesulfonic acid and 1,7-naphthalenedisulfonic acid, anthracenesulfonic acid, anthraquinonesulfonic acid, Alkyl group-substituted or unsubstituted biphenyl sulfonate ions such as alkyl biphenyl sulfonic acid and biphenyl disulfonic acid, polymer sulfonate anions such as polystyrene sulfonate and naphthalene sulfonate formalin condensate, substituted or unsubstituted aromatic sulfonate anions And boron compound anions such as bis-saltylate boron and biscatecholate boron, heteropoly acid anions such as molybdophosphoric acid, tungstophosphoric acid, tungstomolybdophosphoric acid, and imido acid. A dopant can be used 1 type or in combination of 2 or more types.

In order to suppress the desorption of the dopant, it is desirable that it is an organic acid anion rather than an inorganic anion, and it is desirable that thermal decomposition does not occur easily. Further, it is desirable that the dopant of the low molecular compound is higher than the dopant of the high molecular compound because the catalytic activity for the redox couple of the present invention is high. Specific examples include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, and the like.

The amount of dopant used in the conductive polymer catalyst layer is not particularly limited because the optimum value varies depending on the type of dopant used, but is preferably 5 to 60% by mass, more preferably 10 to 45% by mass.

Such a dopant can coexist with a monomer of a conductive polymer when forming the conductive polymer catalyst layer.

The conductive polymer catalyst layer 6 is formed on the electrode substrate 7. The formation method is not particularly limited, and examples thereof include a method of forming a film from a solution in which a conductive polymer is in a molten state or dissolved.

In addition, since it is desirable that the porous state has a larger surface area, for example, the monomer is chemically or electrochemically oxidatively polymerized in a state where the solution containing the conductive polymer monomer and the electrode substrate 7 are in contact with each other. Is preferably used.

Also, a method of forming the conductive polymer powder on the electrode substrate 7 by screen printing, spray coating, brush coating, etc. after processing the conductive polymer powder into a paste or emulsion or a mixture containing a polymer solution and a binder. Can also be used.

Among the above, the method for forming the conductive polymer catalyst layer 6 is preferably an electrolytic polymerization method or a chemical polymerization method, and particularly preferably a chemical polymerization method. The chemical polymerization method is a method in which a polymerization monomer is oxidatively polymerized using an oxidizing agent. On the other hand, the electrolytic polymerization method is a method of forming a conductive polymer film on an electrode made of metal or the like by performing electrolytic oxidation in a solution containing a polymerization monomer.

The oxidizing agent used in the chemical polymerization method includes iodine, bromine, bromine iodide, chlorine dioxide, iodic acid, periodic acid, chlorous acid and other halides, antimony pentafluoride, phosphorus pentachloride, phosphorus pentafluoride. , Metal halides such as aluminum chloride, molybdenum chloride, permanganate, dichromate, chromic anhydride, ferric salt, cupric salt and other high-valent metal salts, sulfuric acid, nitric acid, trifluoromethanesulfuric acid Protonic acids such as oxygen compounds such as sulfur trioxide and nitrogen dioxide, peroxo acids such as hydrogen peroxide, ammonium persulfate and sodium perborate or salts thereof, or molybdophosphoric acid, tungstophosphoric acid, tungstomolybdophosphoric acid There are heteropolyacids or salts thereof, and at least one of them can be used.

Although the above chemical polymerization method is suitable for mass production, when the polymer is reacted with an oxidizing agent in a solution containing an aromatic compound monomer, the resulting polymer is in the form of particles or lumps, and the desired porosity It is difficult to develop and form into an electrode shape. Therefore, the electrode substrate 7 is immersed in a solution containing either an aromatic compound monomer or an oxidizing agent, or after applying the solution to them, the electrode substrate 7 is subsequently immersed or applied in a solution in which the other component is dissolved. For example, it is desirable that the polymerization proceeds on the surface of the electrode substrate 7 to form a conductive polymer.

Alternatively, an additive that lowers the polymerization rate is added to the mixed solution of the monomer and polymerization initiator, and after forming into a film under conditions where polymerization does not occur at room temperature, a porous conductive polymer film is produced by heating reaction. can do. The method for forming a film is not particularly limited, and examples thereof include a spin coating method, a casting method, a squeegee method, and a screen printing method.

Regarding the additive for reducing the polymerization rate, according to the publicly known document “Synthetic Metals” 66, (1994) 263, when the polymerization initiator is a high-valent metal salt, for example, Fe (III) salt, Fe (III) salt Since the oxidation potential changes depending on the pH, the polymerization rate can be slowed by adding a base. Examples of the base include imidazole and dimethyl sulfoxide.

The solvent for dissolving / mixing the monomer, the polymerization initiator, and the additive is not particularly limited as long as it dissolves the compound to be used and does not dissolve the electrode substrate 7 and the polymer. For example, methanol, ethanol, propanol, Examples include alcohols such as normal butanol.

The mixing ratio of the monomer, the polymerization initiator, and the additive varies depending on the compound used, the target degree of polymerization, and the polymerization rate, but the molar ratio to the monomer, that is, the monomer: polymerization initiator is from 1: 0.3 to 1: Preferably, the molar ratio to the polymerization initiator is between 10, ie, the polymerization initiator: additive is between 1: 0.05 and 1: 4.

In addition, the heating conditions in the case of heat polymerization after coating the above mixed solution vary depending on the monomer used, the polymerization catalyst, the type of additives and their mixing ratio, concentration, coating film thickness, etc. When heated in air, the heating temperature is 25 ° C. to 120 ° C., and the heating time is between 1 minute and 12 hours.

Further, using a separately prepared conductive polymer particle dispersion or paste, a conductive polymer film is formed on the surface of the electrode substrate 7 or the electrode substrate with the conductive film, and then subjected to the above chemical polymerization to conduct the conductivity. A method of growing polymer particles can also be used.

The thickness of the catalyst layer 6 in the counter electrode 9 is suitably 5 nm to 5 μm, particularly preferably 50 nm to 2 μm.

After preparing each constituent material as described above, the photoelectric conversion element 10 can be completed by assembling the metal oxide semiconductor electrode and the catalyst electrode so as to face each other through an electrolyte by a conventionally known method.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples. In the following, “%” is based on mass unless otherwise specified.

[Example 1]
[Preparation of porous metal oxide semiconductor]
A porous metal oxide semiconductor layer 3 was formed on a transparent conductive film 2 formed by vacuum deposition of a transparent conductive film 2 made of SnO ₂ doped with fluorine on a transparent substrate 1 made of glass.

FTO glass (manufactured by Nippon Sheet Glass Co., Ltd.) is used as the electrode substrate 8 having the transparent conductive film 2 formed on the transparent substrate 1, and a commercially available titanium oxide paste (manufactured by Catalyst Kasei Co., Ltd., trade name TSP-18NR, A particle size of 20 nm) is printed on the transparent conductive film 2 side by a screen printing method with a film thickness of about 6 μm and an area of about 5 mm × 10 mm, and a commercially available titanium oxide paste (Catalytic Chemical Co., Ltd.) with the same area on the surface. (Product name: TSP-400C, particle size: 400 nm) was applied to a film thickness of about 4 μm by screen printing, and baked in the air at 500 ° C. for 30 minutes. As a result, a titanium oxide film (porous metallized semiconductor film 3) having a thickness of about 10 μm was obtained.

[Adsorption of sensitizing dye]
As the sensitizing dye 4, bis (4-carboxy-4′-tetrabutylammoniumcarboxy-2,2′-bipyridine) diisothiocyanate ruthenium complex (manufactured by Solaronix) generally called N719 dye was used. The porous titanium oxide semiconductor electrode was immersed in an absolute ethanol solution having a pigment concentration of 0.4 mmol / L and allowed to stand overnight under light shielding. Thereafter, excess pigment was washed with absolute ethanol and then air-dried to produce a semiconductor electrode of a solar cell.

[Electrolyte adjustment]
Next, an electrolytic solution constituting the electrolyte layer 5 was prepared. 1-Methyl-3-ethylimidazolium bis (fluorosulfonyl) imide (EMIm-FSI, product name Elexel IL-110 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as a solvent, and 0.8 mol / L of 5, 5′-dithiobis (1-n-butyl 1H-tetrazole) (BTZT) ₂ , 0.1 mol / L 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: lithium salt, (Li -BTZT), 1.5 mol / L of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazolium salt (EMIm-BTZT), 0.5 mol / L Prepared by dissolving L N-methylbenzimidazole (NMBI). In addition, said compound used what was synthesize | combined according to the well-known method or the said synthesis example from commercially available material or commercially available material.

[Production of counter electrode (counter electrode)]
As the counter electrode 9, a poly (3,4-ethylenedioxythiophene) (hereinafter referred to as PEDOT-PTS) counter electrode doped with p-toluenesulfonic acid was used. As the electrode substrate 7, FTO-coated glass (manufactured by Asahi Glass Co., Ltd., ˜10Ω / □) was used, and the electrode substrate cleaned ultrasonically in an organic solvent was subjected to 3,4-ethylenedioxythiophene, iron tris-p-toluenesulfonate ( III) A reaction solution in which dimethyl sulfoxide was dissolved in n-butanol at a weight ratio of 1: 8: 1 was applied by spin coating. The spin coating was performed at 2000 rpm for 30 seconds, and the concentration of 3,4-ethylenedioxythiophene in the solution was 0.48M. Subsequently, the electrode substrate coated with the solution was placed in a thermostat kept at 110 ° C., heated for 5 minutes, polymerized, and then washed with methanol to produce a counter electrode. The film thickness of the produced PEDOT thin film was about 0.3 μm.

[Assembly of solar cells]
The counter electrode 9 produced as described above is provided with a 1 mmφ electrolyte injection hole at an appropriate position with an electric drill, and then the titanium oxide film 3 on the transparent substrate 1 provided with the transparent conductive film 2 produced as described above. A thermoplastic sheet (Himiran 1652: made by Mitsui DuPont Polychemical Co., Ltd., film thickness 25 μm) was sandwiched between the electrode substrate 8 (working electrode) made of the above and the counter electrode, and both electrodes were bonded by thermocompression bonding. Next, after the electrolyte prepared as described above was injected between both electrodes, a 1 mm thick glass plate was placed on the electrolyte injection hole, and a UV sealant (developed product 31X-727 manufactured by ThreeBond Co., Ltd.) was placed thereon. ) Was applied, and UV light was applied at an intensity of 100 mW / cm ² for 30 seconds to perform sealing, thereby producing a solar cell element.

[Example 2]
As the electrolyte layer 5, 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1-n-butyl-5 instead of 1-methyl-3-ethylimidazolium salt (EMIm-BTZT) A solar cell element was produced in the same manner as in Example 1 except that -mercapto-1,2,3,4-tetrazole: 1-methyl-1-propylpyrrolidinium salt (MPPy-BTZT) was used.

[Example 3]
As the electrolyte layer 5, instead of 1-methyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazolium salt (EMIm-MTZT), 1-methyl-5-mercapto-1 , 2,3,4-tetrazole: 1,2-dimethyl-3-propylimidazolium salt (DMPIm-BTZT) was used to produce a solar cell element in the same manner as in Example 1.

[Example 4]
As electrolyte layer 5, the same as Example 1 except that the concentration of 5,5′-dithiobis (1-n-butyl-1H-tetrazole) (BTZT) ₂ was changed from 0.8 mol / L to 1.6 mol / L A solar cell element was prepared.

[Example 5]
As the electrolyte layer 5, 3-methoxypropionitrile was used as a solvent, and 0.4

M

5,5′-dithiobis (1-n-butyl-1H-tetrazole) (BTZT) ₂ , 0.05 mol / L of 1 -N-butyl-5-mercapto-1,2,3,4-tetrazole: lithium salt (Li-BTZT), 0.75 mol / L 1-n-butyl-5-mercapto-1,2,3,4 A solar cell element was produced in the same manner as in Example 1 except that tetramethylammonium salt (TMA-BTZT) and 0.2 mol / L t-butylpyridine (tBP) were used.

[Example 6]
As the electrolyte layer 5, instead of 1-n-butyl-5-mercapto-1,2,3,4-tetramethylammonium salt (TMA-BTZT), 1-n-butyl-5-mercapto-1,2,3 , 4-tetrazole: 1-methyl-3-ethylimidazolium salt (EMIm-BTZT) was used to produce a solar cell element in the same manner as in Example 5.

[Example 7]
As electrolyte layer 5, the concentration of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: tetramethylammonium salt (TMA-BTZT) was changed from 0.75 mol / L to 0.35 mol / L. A solar cell element was produced in the same manner as in Example 5 except that.

[Example 8]
As the electrolyte layer 5, the concentration of 1-n-butyl-5-mercapto-1,2,3,4-tetramethylammonium salt (TMA-BTZT) was changed from 0.75 mol / L to 0.95 mol / L, A solar cell element was produced in the same manner as in Example 5 except that the concentration of 5′-dithiobis (1-n-butyl-1H-tetrazole) (BTZT) ₂ was changed from 0.4 M to 1.0 M.

[Example 9]
As the sensitizing dye 4, a heptamethine cyanine dye represented by the following formula (8) is used in place of the N719 dye, and 3-methoxypropionitrile is used as a solvent as the electrolyte layer 5, and 0.1M of 5, 5′-dithiobis (1-n-butyl-1H-tetrazole) (BTZT) ₂ , 0.05 mol / L 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: lithium salt (Li -BTZT), 0.05 mol / L of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazolium salt (EMIm-BTZT) dissolved A solar cell element was produced in the same manner as in Example 1 except that was used.

[Comparative Example 1]
As the electrolyte layer 5, 1-methyl-3-ethylimidazolium bis (trifluoromethanesulfonyl) imide (EMIm-FSI) was used as a solvent, 0.2 mol / L iodine, 2.0 mol / L 1,2- A solar cell element was produced in the same manner as in Example 1 except that dimethyl-3-ethylimidazolium iodide (DMPIm-I) and 0.5 mol / L N-methylbenzimidazole (NMBI) were used. did.

[Comparative Example 2]
As the electrolyte layer 5, 1-methyl-3-ethylimidazolium bis (trifluoromethanesulfonyl) imide (EMIm-FSI) was used as a solvent, and 0.8 mol / L of 5,5′-dithiobis (1-methyl-1H) was used. -Tetrazole) (MTZT) ₂ , 0.1 mol / L of 1-methyl-5-mercapto-1,2,3,4-tetrazole: lithium salt, (Li-MTZT) 1.5 mol / L of 1-methyl- 5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazolium salt (EMIm-MTZT) dissolved in 0.5 mol / L N-methylbenzimidazole (NMBI) A solar cell element was produced in the same manner as in Example 1 except that.

[Comparative Example 3]
As a counter electrode 9, a solar cell element was produced in the same manner as in Comparative Example 1 except that a Pt counter electrode (manufactured by Geomatec) obtained by depositing Pt on ITO conductive glass by sputtering was used.

[Comparative Example 4]
As the electrolyte layer 5, 1-methyl-3-ethylimidazolium bis (trifluoromethanesulfonyl) imide (EMIm-FSI) was used as a solvent, and 0.5 mol / L of 1-methyl-5-mercapto-1,2, 3,4-tetrazole: tetramethylammonium salt, 0.5 mol /

L

2,2′-dithiobis (5-methyl-1,3,4-thiadiazole), 0.5 mol / L N-methylbenzimidazole (NMBI) ) Was used to prepare a solar cell element in the same manner as in Example 1.

[Comparative Example 5]
As the electrolyte layer 5, 1-methyl-3-ethylimidazolium bis (trifluoromethanesulfonyl) imide (EMIm-FSI) was used as a solvent, and 2 mol / L of 5-methyl-2-mercapto-1,3,4- Thiadiazole: 1-methyl-3-ethylimidazolium salt, 0.2

M

[Comparative Example 6]
As the electrolyte layer 5, 3-methoxypropionitrile was used as a solvent, and 0.15 mol / L iodine, 0.8 mol / L 1,2-dimethyl-3-ethylimidazolium iodide (DMPIm-I), A solar cell element was produced in the same manner as in Example 5 except that 0.2 mol / L t-butylpyridine (tBP) dissolved was used.

[Comparative Example 7]
As the electrolyte layer 5, 3-methoxypropionitrile was used as a solvent, and 0.4

M

5,5′-dithiobis (1-methyl-1H-tetrazole) (MTZT) ₂ , 0.05 mol / L 1-methyl was used. -5-mercapto-1,2,3,4-tetrazole: lithium salt (Li-MTZT), 0.35 mol / L 1-methyl-5-mercapto-1,2,3,4-tetramethylammonium salt ( A solar cell element was produced in the same manner as in Example 5 except that TMA-BTZT) and 0.2 mol / L t-butylpyridine (tBP) dissolved therein were used.

[Comparative Example 8]
As the electrolyte layer 5, 3-methoxypropionitrile was used as a solvent, and 0.1

M

5,5′-dithiobis (1-methyl-1H-tetrazole) (MTZT) ₂ , 0.05 mol / L 1-methyl was used as the electrolyte layer 5. -5-mercapto-1,2,3,4-tetrazole: lithium salt (Li-MTZT), 0.05 mol / L 1-methyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl A solar cell element was produced in the same manner as in Example 9 except that a solution in which -3-ethylimidazolium salt (EMIm-MTZT) was dissolved was used.

[Comparative Example 9]
As the electrolyte layer 5, 3-methoxypropionitrile was used as a solvent, and 0.1

M

5,5′-dithiobis (1-sec-butyl-1H-tetrazole) (sBTTZT) ₂ , 0.05 mol / L of 1 -Sec-butyl-5-mercapto-1,2,3,4-tetrazole: lithium salt (Li-sBTZT), 0.05 mol / L 1-sec-butyl-5-mercapto-1,2,3,4 -Tetrazole: A solar cell element was produced in the same manner as in Example 9 except that 1-methyl-3-ethylimidazolium salt (EMIm-sBTTZT) was used.

The oxidation-reduction pairs used in the above examples and comparative examples were synthesized by the following method. However, the synthesis method is not limited to these.

[Production Example 1] (Synthesis of redox couple precursors (1-n-butyl-5-mercapto-1,2,3,4-tetrazole) in Examples 1 to 9 and Comparative Example 3)
n-Butyl isothiocyanate (3.84 g, 33.3 mmol) and sodium azide (3.25 g, 50.0 mmol) were reacted in 25 ml of pure water for 5 hours. After the reaction, extraction was performed using diethyl ether to remove impurities. The aqueous layer was acidified with concentrated sulfuric acid (pH = 1), and extracted again with diethyl ether three times. The ether layer was dried over anhydrous sodium sulfate, the solvent was removed, and the target substance 1-n-butyl-5-mercapto-1,2,3,4 was obtained in a yield of 75% (3.97 g, 25.1 mmol). -Tetrazole was obtained. For identification of the product, high performance liquid chromatography (conditions: hexane: 2-propanol = 95: 5 as a solvent was passed at a flow rate of 1 ml / min and detection was performed under irradiation with a wavelength of 237 nm) was used. Melting point (mp) measurement, IR analysis, ¹ H-NMR and ¹³ C-NMR analysis were also performed. The measurement conditions and results are shown below.

HPLC 4.0 min; mp = 37.5 ° C; IR (KBr) 2600 (-SH); ¹ H NMR (CDCl ₃ ) δ 0.97 (t, J = 7.18 Hz, 3H), 1.40 (sex, J = 7.18 Hz, 2H) , 1.90 (quin, J = 7.18 Hz, 2H), 4.28 (t, J = 7.18 Hz, 2H), 14.0 (br s, 1H); ¹³ C NMR (CDCl ₃ ) δ 13.51, 19.66, 30.00, 47.28, 163.77 .

[Production Example 2] (Synthesis of redox couple precursors of Examples 1 to 9 and Comparative Example 3 (1-n-butyl-5-mercapto-1,2,3,4-tetrazole: potassium salt))
0.28 g (1.31 mmol) of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Preparation Example 1 and 0.0898 g (0.650 mmol) of potassium carbonate in 15 ml of methanol The mixture was reacted for 1 hour under ultrasonic irradiation. The remaining solid was filtered, and after removing the solvent, washed with dichloromethane, dried, and the target substance 1-n-butyl-5-mercapto-1,2, in a yield of 98% (0.2531 g, 1.29 mmol). , 3,4-tetrazole: potassium salt was obtained. The results of melting point measurement and ¹ H-NMR and ¹³ C-NMR analysis of the product are shown below.

mp = 195.0 ° C; ¹ H NMR (CD ₃ OD) δ 0.93 (t, J = 7.18 Hz, 3H), 1.34 (sex, J = 7.18 Hz, 2H), 1.82 (quin, J = 7.18 Hz, 2H), 4.24 (t, J = 7.18 Hz, 2H); ¹³ C NMR (CD ₃ OD) δ 12.68, 19.42, 30.63, 45.81, 165.63.

[Production Example 3] (Synthesis of oxidized form (5,5'-dithiobis (1-n-butyl1H-tetrazole)) of Examples 1 to 9 and Comparative Example 3)
2.95 g (15.0 mmol) of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: potassium salt obtained in Production Example 2 and 1.91 g (7.50 mmol) of iodine were The reaction was carried out in 30 ml of methanol at room temperature for 1 hour. After removal of the solvent, 10 ml of water was added, liquid separation was performed with dichloromethane (20 ml × 3 times), the dichloromethane layer was collected, filtered through silica gel column chromatography (diethyl ether: hexane = 5: 1), and iodine and The starting potassium salt was removed, and the

target substance

5,5′-dithiobis (1-n-butyl 1H-tetrazole) was obtained in a yield of 35% (1.65 g, 5.25 mmol). For identification of the product, high performance liquid chromatography (conditions: hexane: 2-propanol = 95: 5 as a solvent was passed at a flow rate of 1 ml / min and detection was performed under irradiation with a wavelength of 237 nm) was used. Melting point measurement, ¹ H-NMR and ¹³ C-NMR analysis were also performed. The measurement conditions and results are shown below.

HPLC 18.9 min; ¹ H NMR (CDCl ₃ ) δ 0.84 (t, J = 7.46 Hz, 6H) 1.23 (sex, J = 7.46 Hz, 4H) 1.78 (quin, J = 7.46 Hz, 4H), 4.35 (t, J = 7.46 Hz, 4H); ¹³ C NMR (CDCl ₃ ) δ 13.39, 19.59, 31.47, 48.36, 151.75.

[Production Example 4] (Synthesis of reduced products of Examples 1 to 9 and Comparative Example 3 (1-n-butyl-5-mercapto-1,2,3,4-tetrazole: lithium salt))
0.404 g (2.55 mmol) of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Preparation Example 1 and 0.0922 g (1.28 mmol) of lithium carbonate in 15 ml of methanol The mixture was reacted for 1 hour under ultrasonic irradiation. The remaining solid was filtered, and after removing the solvent, washed with dichloromethane, dried, and the target substance 1-n-butyl-5-mercapto-1,2, in a yield of 34% (0.145 g, 0.867 mmol). , 3,4-tetrazole: lithium salt was obtained. The results of melting point measurement, ¹ H-NMR and ¹³ C-NMR analysis of the product are shown below.

mp = 93.0 ° C; ¹ H NMR (DMSO) δ 0.83 (t, J = 7.18 Hz, 3H), 1.19 (sex, J = 7.18 Hz, 2H), 1.63 (quin, J = 7.18 Hz, 2H), 4.02 ( t, J = 7.18 Hz, 2H); ¹³ C NMR (DMSO) δ 14.06, 19.75, 31.03, 45.05, 167.69.

[Production Example 5] (reduced form of Examples 1, 4, 6, 9 and Comparative Example 3 (1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethyl Synthesis of imidazolium salt)
A solution of 0.174 g (1.10 mmol) of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Preparation Example 1 in 3 ml of methanol was dissolved in 1-ethyl in an aqueous solvent. The solution was added dropwise to -3-methylimidazolium carbonate (0.330 g, 1.00 mmol, 52.2% inH ₂ Ow / w) and allowed to react for 1 minute. The solvent was removed and the target substance 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazo was obtained in a yield of 98% (0.263 g, 0.980 mmol). A lithium salt was obtained. The results of ¹ H-NMR and ¹³ C-NMR analyzes of the product are shown below.

¹ H NMR (CDCl ₃ ) δ 0.94 (t, J = 7.18 Hz 3H), 1.37 (sex, J = 7.18 Hz, 2H), 1.52 (t, J = 7.37 Hz, 3H), 1.85 (quin, J = 7.18 Hz, 2H), 4.05 (s, 3H), 4.26 (t, J = 7.18 Hz, 2H), 4.36 (q, J = 7.37 Hz, 2H), 7.56 (d, J = 1.80 Hz, 2H), 9.90 ( s, 1H); ¹³ C NMR (CDCl ₃ ) δ, 13.28, 15.11, 19.33, 30.46, 35.96, 44.61, 45.46, 121.65, 123.33, 136.15, 166.04.

[Production Example 6] (Synthesis of reduced products of Examples 5, 7, and 8 (1-n-butyl-5-mercapto-1,2,3,4-tetrazole: tetramethylammonium salt))
1 mol equivalent of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Preparation Example 1 dissolved in 3 ml of methanol is 1 mol equivalent of 50% methanol of tetramethylammonium. The solution was added dropwise to the solution and allowed to react for 1 hour. The solvent was removed, and the target substance 1-n-butyl-5-mercapto-1,2,3,4-tetrazole: tetramethylammonium salt was obtained in a yield of 95%. The results of ¹ H-NMR and ¹³ C-NMR analyzes of the product are shown below.

¹ H NMR (CDCl ₃ ) δ 0.94 (t, 3H), 1.36 (sex, 2H), 1.85 (quin, 2H), 3.4 (s, 12H), 4.24 (t, 2H), ¹³ C NMR (CDCl ₃ ) δ, 13.66, 19.84, 30.97, 55.73, 166.6

[Production Example 7] (Synthesis of reduced product of Example 2 (1-methyl-5-mercapto-1,2,3,4-tetrazole: MPPy salt))
1 mol equivalent of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Production Example 1 dissolved in methanol and 1-methyl-1-propylpyrrolidinium hydroxy 1 mol equivalent of methanol (MPPy-OH) dissolved in methanol was mixed, stirred for 3 hours, and then the solvent was distilled off by a rotary evaporator, whereby liquid 1-methyl-5-mercapto-1, 2,3,4-tetrazole: MPPy salt was synthesized. The reaction yield was 95%. The results of ¹ H-NMR analysis of the product are shown below.

¹ H NMR (CDCl ₃ ) δ 0.94 (t, 3H), 1.10 (t, 3H), 1.36 (sex, 2H), 1.85 (m, 4H), 2.28 (m, 4H), 3.26 (quin, 2H), 3.61 (m, 2H) 3.80 (m, 4H), 4.26 (t, 2H),

[Production Example 8] (Synthesis of reduced product of Example 3 (1-methyl-5-mercapto-1,2,3,4-tetrazole: DMPIm salt))
1 mol equivalent of 1-n-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Production Example 1 and 1,2-dimethyl-3-propylimidazolium dissolved in methanol 1 mol equivalent of hydroxide (DMPIm-OH) dissolved in methanol was mixed, stirred for 3 hours, and then the solvent was distilled off with a rotary evaporator, whereby 1-methyl-5-mercapto-1 which was liquid at room temperature was obtained. , 2,3,4-Tetrazole: DMPIm salt was synthesized. The reaction yield was 98%. The results of ¹ H-NMR analysis of the product are shown below.

¹ H NMR (CDCl ₃ ) δ 0.94 (t, 3H), 1.02 (t, 3H) 1.37 (sex, 2H), 1.85 (quin, 2H), 1.91 (sex, 2H)., 2.82 (s, 3H), 4.00 (s, 3H), 4.18 (t, 2H), 4.25 (t, 2H), 7.51 (d, 1H), 7.62 (d, 1H),

[Comparative Production Example 1] (Synthesis of oxidation-reduction pair precursor (1-sec-butyl-5-mercapto-1,2,3,4-tetrazole) of Comparative Example 9)
3.84 g (33.4 mmol) of sec-butyl isothiocyanate and 3.25 g (50.0 mmol) of sodium azide were reacted in 25 ml of pure water for 5 hours. After the reaction, extraction was performed using diethyl ether to remove impurities. The aqueous layer was acidified with concentrated sulfuric acid (pH = 1), and extracted again with diethyl ether three times. The ether layer was dried over anhydrous sodium sulfate, the solvent was removed, and the target substance 1-sec-butyl-5-mercapto-1,2,3,4 was obtained in a yield of 59% (3.10 g, 19.6 mmol). -Tetrazole was obtained. For identification of the product, high performance liquid chromatography (conditions: hexane: 2-propanol = 95: 5 as a solvent was passed at a flow rate of 1 ml / min and detection was performed under irradiation with a wavelength of 237 nm) was used. Further, IR measurement, ¹ H-NMR and ¹³ C-NMR analysis of the target substance were performed. The results are shown below.

HPLC 4.0 min; mp = 67.0 ° C; IR (KBr) 2758 (-SH); ¹ H NMR (CDCl ₃ ) δ 0.90 (t, J = 7.56 Hz, 3H), 1.52 (d, J = 6.78 Hz, 3H) , 1.84-2.08 (m, 2H), 4.80 (sex, J = 6.78 Hz, 1H), 14.17 (br s, 1H); ¹³ C NMR (CDCl ₃ ) δ 10.47, 19.23, 28.57, 56.11, 163.40.

[Comparative Production Example 2] (Synthesis of oxidation-reduction pair precursor (1-sec-butyl-5-mercapto-1,2,3,4-tetrazole: potassium salt) of Comparative Example 9)
0.272 g (1.72 mmol) of 1-sec-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Comparative Production Example 1 and 0.113 g (0.816 mmol) of potassium carbonate were mixed with methanol (15 ml). ), And reacted for 1 hour under ultrasonic irradiation. The residual solid was filtered, the solvent was removed, washed with dichloromethane, dried, and the target substance 1-sec-butyl-5-mercapto-1,2, in a yield of 96% (0.323 g, 1.64 mmol). , 3,4-tetrazole: potassium salt was obtained. The results of melting point measurement, ¹ H-NMR and ¹³ C-NMR analysis of the product are shown below.

mp = 162.0 ° C; ¹ H NMR (DMSO) δ 0.70 (t, J = 7.47 Hz, 3H), 1.25 (d, J = 7.05 Hz, 3H), 1.63-1.83 (m, 2H), 4.69 (sex, J = 7.05 Hz, 1H); ¹³ C NMR (DMSO) δ 11.01, 20.24, 29.06, 52.69, 167.36.

[Comparative Production Example 3] (Synthesis of Oxide of Comparative Example 9 (5,5′-dithiobis (1-sec-butyl1H-tetrazole))
1-sec-butyl-5-mercapto-1,2,3,4-tetrazole: 2.81 g (14.4 mmol) of potassium salt and 1.82 g (7.18 mmol) of iodine obtained in Comparative Production Example 2, The reaction was carried out in 30 ml of methanol at room temperature for 1 hour. After removing the solvent, 10 ml of water was added, liquid separation was performed with dichloromethane (20 ml × 3 times), and the dichloromethane layer was collected and filtered with silica gel column chromatography (diethyl ether: hexane = 5: 1) to remove iodine. The starting potassium salt was removed by recrystallization (hexane: 2-propanol = 95: 5), and the

target substance

5,5′-dithiobis (1- (1)) was obtained in a yield of 29% (1.31 g, 4.14 mmol). sec-Butyl 1H-tetrazole was obtained, and the product was identified by high performance liquid chromatography (condition: hexane: 2-propanol = 95: 5 as a solvent at a flow rate of 1 ml / min and detection under irradiation at a wavelength of 237 nm. In addition, the melting point of the target substance, ¹ H-NMR and ¹³ C-NMR analysis were performed, and the results are shown below.

HPLC 14.80 min; mp = 67.0 ° C; ¹ H NMR (CDCl ₃ ) δ 0.79 (t, J = 7.46 Hz, 6H) 1.59 (d, J = 6.68 Hz, 6H) 1.86-2.05 (m, 4H), 4.70 ( sex, J = 6.68 Hz, 2H); ¹³ C NMR (CDCl ₃ ) δ 10.51, 20.59, 29.80, 58.30, 150.60.

[Comparative Production Example 4] (Synthesis of reduced product of Comparative Example 9 (1-sec-butyl-5-mercapto-1,2,3,4-tetrazole: lithium salt))
0.267 g (1.69 mmol) of 1-sec-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Comparative Production Example 1 and 0.0626 g (0.847 mmol) of lithium carbonate in 15 ml of methanol The mixture was reacted for 1 hour under ultrasonic irradiation. The remaining solid was filtered, the solvent was removed, washed with dichloromethane, dried, and the target substance 1-sec-butyl-5-mercapto-1,2, in a yield of 14% (0.0380 g, 0.231 mmol). , 3,4-tetrazole: lithium salt was obtained. The results of melting point measurement, ¹ H-NMR and ¹³ C-NMR analysis of the target substance are shown below.

mp = 270.0 ° C or higher; ¹ H NMR (DMSO) δ 0.71 (t, J = 7.47 Hz, 3H), 1.26 (d, J = 6.58 Hz, 3H), 1.64-1.84 (m, 2H), 4.70 (sex, J = 6.58 Hz, 1H); ¹³ C NMR (DMSO) δ 11.06, 20.25, 29.08, 52.68, 167.36.

[Comparative Production Example 5] (Synthesis of reduced product of Comparative Example 9 (1-sec-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazolium salt))
A solution of 0.171 g (1.09 mmol) of 1-sec-butyl-5-mercapto-1,2,3,4-tetrazole obtained in Comparative Production Example 1 in 3 ml of methanol was dissolved in 1-ethyl in an aqueous solvent. -3-Methylimidazolium carbonate (0.330 g, 1.00 mmol, 52.2 wt% aqueous solution) was added dropwise and reacted for 1 minute. The solvent was removed, and the target substance 1-sec-butyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazo in a yield of 96% (0.258 g, 0.960 mmol) A lithium salt was obtained. The results of melting point measurement, ¹ H-NMR and ¹³ C-NMR analysis of the target substance are shown below.

¹ H NMR (CDCl ₃ ) δ 0.84 (t, J = 7.18 Hz, 3H), 1.42 (d, J = 7.05 Hz, 3H), 1.53 (t, J = 6.70 Hz, 3H), 1.80-1.99 (m, 2H), 4.06 (s, 3H), 4.37 (q, J = 6.70 Hz, 2H), 4.88 (sex, J = 7.05 Hz, 1H), 7.60 (d, J = 1.80 Hz, 2H), 10.00 (s, 1H); ¹³ C NMR (CDCl ₃ ) δ 10.48, 15.40, 19.65, 28.92, 36.29, 44.96, 53.60, 121.77, 123.50, 136.83, 165.88.

The redox couples used in Comparative Examples 1, 2, 4, 5, 6, 7, and 8 were synthesized based on the descriptions in Non-Patent Document 6,

Patent Documents

1 and 2, or commercially available materials, respectively. did.

[Photoelectric conversion efficiency and durability evaluation of solar cells]
Evaluation of the solar cell produced by the above was implemented with the following method. For performance evaluation, a xenon lamp solar simulator with AM filter XES-502S (purchased from Kansai Scientific Machinery Co., Ltd.), after adjusting the spectrum of AM1.5G, under the irradiation condition of 100 mW / cm ² , the potentio The load characteristic (IV characteristic) by the stat was evaluated.

The evaluation value of the solar cell includes open circuit voltage Voc (V), short circuit current density Jsc (mA / cm ² ), form factor FF (−), conversion efficiency η (%). Was evaluated based on the degree of conversion efficiency. In addition, the device performance retention rate in the dark and at room temperature was also evaluated.

The light irradiation intensity was calculated by using a spectrum analyzer (LS-100, manufactured by Eihiro Seiki Co., Ltd.) by comparing the integrated value of irradiation light in the region of λ: 400 to 800 nm with the value of reference sunlight.

[Evaluation with ionic liquid electrolyte system]
Table 1 shows the results of IV characteristic evaluation and stability evaluation of the photoelectric conversion elements of Examples and Comparative Examples using an ionic liquid as a solvent for the electrolyte layer 5 under simulated sunlight irradiation conditions.

As can be seen from the results shown in Table 1, the photoelectric conversion elements of Examples 1 to 4 according to the present invention are equivalent to the element of Comparative Example 1 using the same ionic liquid as a solvent and using a conventional iodine-based redox pair. The above photoelectric conversion performance is shown under simulated sunlight irradiation conditions. Further, 1-methyl-5-mercapto-1,2,3,4-tetrazole: 1-methyl-3-ethylimidazolium salt shown in

Patent Document

2, and 5,5′-dithiobis (1-methyl- Compared with Comparative Example 2 using 1H-tetrazole) as the redox couple, Example 1 of the present invention shows higher device performance. This indicates that the reverse electron transfer from the working electrode to the electrolyte due to the steric hindrance effect rather than the adverse effect of the decrease in carrier mobility due to the increase in molecular size due to the change of the methyl group of the tetrazole ring to the n-butyl group. It is considered that the contribution of improving the charge separation efficiency due to the suppression effect is greater.

Moreover, when Example 1 and Example 4 are compared, the compound (reduced form) represented by the general formula (2) is excessive with respect to 1 mol of the compound (oxidized form) represented by the general formula (1). It can be seen that the device performance is better when used. The reason for this is not clear, but when the reductant is used in excess, the oxidant (T ₂ ) and the reductant (T ⁻ ) become a charge transfer complex (denoted as T ₂ · T ⁻ → T ₃ ⁻ ). It is considered that the charge transfer performance is improved by promoting the formation of. Another reason is that the charge exchange reaction between the oxidant and the reductant is more likely to occur when the reductant is excessive.

Comparative Example 3 using a Pt electrode as the counter electrode is inferior in element performance to Example 1 using a PEDOT electrode as the counter electrode, and in particular, the value of FF is lowered. This is because PEDOT has higher catalytic activity for the sulfide-based redox couple used in the present invention than Pt. This is also confirmed from the interface reaction resistance analysis by impedance measurement. Therefore, it can be said that the photoelectric conversion element which shows high photoelectric conversion efficiency can be produced by using together the oxidation-reduction pair of this invention, and electroconductive polymer catalysts, such as PEDOT.

Further, Comparative Example 4 using 1-methyl-5-mercapto-1,2,3,4-tetrazole: tetramethylammonium salt shown in Non-Patent Document 6 as a reductant is obtained by adding a reductant to an ionic liquid. Since solubility is lower than the compound of this invention, it can melt | dissolve only about 0.5M, As a result, compared with Example 1, the photoelectric conversion performance is inferior.

Further, Comparative Example 5 using a sulfide redox having a thiadiazole skeleton disclosed in Patent Document 1 as a redox pair has a low solubility in a solvent of a disulfide compound that is an oxidant, and therefore, compared with Example 1. Since the photoelectric conversion performance was inferior and the electrolyte was unstable under high concentration conditions, the device performance retention after 30 days was reduced to about 50%. On the other hand, in Examples 1 to 3 of the present invention, the device performance hardly deteriorates even after 30 days. Therefore, a practical photoelectric conversion element can be produced by combining the redox couple of the present invention, a conductive polymer catalyst, and an ionic liquid.

[Evaluation in organic solvent electrolyte system]
Table 2 shows the results of IV characteristic evaluation under simulated sunlight irradiation conditions of the photoelectric conversion elements of Examples and Comparative Examples using 3-methoxypropionitrile, which is an organic solvent, as the solvent of the electrolyte layer 5.

The photoelectric conversion element of the present invention shown in Example 5 using the oxidation-reduction pair of the present invention is the same as that of Comparative Example 6 using the same 3-methoxypropionitrile as a solvent and a conventional iodine-based redox pair. Comparative example using 1-methyl-5-mercapto-1,2,3,4-tetrazole: tetramethylammonium salt shown in Non-Patent Document 6 as a reductant in addition to the photoelectric conversion performance close to the device Compared with 7, the performance is clearly superior. Comparing the characteristic values, it can be seen that the open circuit voltage value (Voc) and the short circuit current value (Jsc) are improved. Similar to the results in the above ionic liquid electrolyte system, this phenomenon greatly contributes to the effect of suppressing the reverse electron transfer from the working electrode to the electrolyte solution due to the steric hindrance effect by extending the alkyl chain length of the sulfide compound. It is thought that.

When Example 5 and Example 6 are compared, Example 5 in which the counter cation is a TMA salt shows superior photoelectric conversion performance than Example 6 in which the counter cation of the reductant is an EMIm salt. This is presumably because the TMA salt having a smaller cation molecular size has a lower viscosity of the electrolyte and improved carrier mobility.

Further, similarly to the results in the ionic liquid electrolyte system, the results of Examples 5 and 7 and 8 show that the device performance is better when the reductant concentration is higher than the oxidant concentration.

[Evaluation using heptamethine cyanine dye]
Table 3 shows the results of IV characteristic evaluation and stability evaluation under the simulated sunlight irradiation conditions of the photoelectric conversion elements of Examples and Comparative Examples using heptamethine cyanine dyes that absorb near infrared light as sensitizing dyes. Shown in

The photoelectric conversion element using the oxidation-reduction pair of the present invention shown in Example 9 uses 1-methyl-5-mercapto-1 shown in Non-Patent Document 6 using the same 3-methoxypropionitrile as a solvent. , 2,3,4-tetrazole: an excellent photoelectric conversion performance as compared with Comparative Example 8 in which the counter cation of tetramethylammonium salt was changed to the same 1-methyl-3-ethylimidazolium salt as in Example 9. Yes. Similar to the results in Table 2 using N719 dye, comparing each characteristic value shows that the open circuit voltage value (Voc) and the short circuit current value (Jsc) are improved. Therefore, it can be seen that the redox couple of the present invention also shows excellent performance for photoelectric conversion elements using heptamethine cyanine dyes.

Comparative Example 9 uses a redazole pair in which the tetrazole group substituent is a sec-butyl- group, but the short-circuit current value is inferior to that of Example 9. As a result, in the case of the redox couple having a branched alkyl group, the adverse effect of the decrease in carrier mobility accompanying the increase in the viscosity of the electrolyte due to the increase in the molecular size is greater than that of the redox couple having the linear alkyl group of the present invention. The reason is considered.

As described above, the photoelectric conversion device of the present invention is superior to the conventional iodine-based redox couple in terms of device performance and transparency, and the redox couple, ionic liquid, and organic conductivity of the present invention are high. By using the molecular counter electrode, a highly practical solar cell element excellent in performance, durability, cost, and design can be provided.

The photoelectric conversion element according to the present invention is suitably used as a photoelectric conversion element that can be used indoors and outdoors. Further, by utilizing the characteristics of the electrolyte of the present invention, it is particularly suitable for consumer equipment and the like that are required to be designed. Can be used. Furthermore, it can be used not only as a photoelectric conversion element but also as an optical sensor.

DESCRIPTION OF SYMBOLS 1 ... Transparent base | substrate 2 ... Transparent electrically conductive film 3 ... Porous metal oxide semiconductor (layer)
4 ... Sensitizing dye 5 ... Electrolyte layer 6 ... Catalyst layer 7 ... Electrode substrate 8 ... Electrode substrate (working electrode)
9 ... Counter electrode 10 ... Photoelectric conversion element

Claims

A redox couple comprising a compound represented by the general formula (1) and a compound represented by the general formula (2).

In the general formula (1), A is Li, K, or Na, or an ammonium compound represented by the general formula (3), an imidazolium compound represented by the general formula (4), or a general formula (5). The pyrrolidinium compound is shown. R 1 in the general formula (1) and the general formula (2) represents a linear alkyl group having 4 to 8 carbon atoms, and the plurality of R 1 are the same or partly or completely different from each other. .

In the general formulas (3) to (5), R 2 represents an alkyl group having 1 to 12 carbon atoms, and R 3 represents H or a methyl group. The plurality of R 2 are the same as each other or part or all of them are different.
It is a photoelectric conversion element provided with the semiconductor electrode, the counter electrode, and the electrolyte layer hold | maintained between these both electrodes, Comprising: The said electrolyte layer contains the oxidation-reduction pair described in Claim 1, The said counter electrode Contains a catalyst having catalytic activity for this redox pair.
The photoelectric conversion element according to claim 2, wherein the electrolyte layer contains an ionic liquid having a bis (fluorosulfonyl) imide anion represented by the following formula (6).
The photoelectric conversion element according to claim 2 or 3, wherein the catalyst contained in the counter electrode is a conductive polymer containing a polymer of 3,4-ethylenedioxythiophene or a derivative thereof.