JP7014656B2 - Photoelectric conversion element - Google Patents

Description

The present invention relates to a photoelectric conversion element.

As a photoelectric conversion element, a photoelectric conversion element using a dye has been attracting attention because it is inexpensive and high photoelectric conversion efficiency can be obtained, and various developments have been made on a photoelectric conversion element using a dye.

As a photoelectric conversion element using such a dye, for example, the photoelectric conversion element of Patent Document 1 below is known. The following Patent Document 1 describes an electrolyte provided between a conductive substrate, a counter electrode facing the conductive substrate and having a catalyst layer, an oxide semiconductor layer provided on the conductive substrate, and the conductive substrate and the counter electrode. A photoelectric conversion element having a photoelectric conversion cell having a dye adsorbed on an oxide semiconductor layer and an electrolyte containing an imidazole compound is disclosed, and the concentration of the imidazole compound in the electrolyte is 0.01 to 0.2 M. It is disclosed that the leakage current can be suppressed by the above.

Japanese Unexamined Patent Publication No. 2016-134479

By the way, in a photoelectric conversion element using a dye, in order to suppress deterioration of the photoelectric conversion element due to intrusion of oxygen into the electrolyte and to enhance the effect of suppressing deterioration of power generation performance due to oxygen (hereinafter referred to as "oxygen resistance"). In addition, it is desirable to reduce the oxygen permeation rate of the sealing portion.

However, in the photoelectric conversion element described in Patent Document 1 described above, if the oxygen permeation rate of the sealing portion is reduced in a state where a catalyst metal such as platinum is used as the counter electrode catalyst layer, the oxygen resistance is improved, but the oxygen resistance is 20000. When placed under high illuminance of lux or higher, there was room for improvement in terms of the effect of suppressing deterioration of power generation performance with respect to light (hereinafter referred to as "light resistance").

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoelectric conversion element having excellent light resistance while having excellent oxygen resistance even when placed under high illuminance. ..

As a result of diligent studies to solve the above-mentioned problems, the present inventors have come to solve the above-mentioned problems by the following inventions.

That is, the present invention includes at least one photoelectric conversion cell, wherein the photoelectric conversion cell includes a first electrode substrate, a second electrode substrate facing the first electrode substrate, the first electrode substrate, or the second electrode substrate. It is formed by an oxide semiconductor layer provided on an electrode substrate, a sealing portion for joining the first electrode substrate and the second electrode substrate, and the first electrode substrate, the second electrode substrate, and the sealing portion. The second electrode substrate has a catalyst layer containing a catalyst metal, the electrolyte contains an imidazole compound, and the concentration of the imidazole compound in the electrolyte is 0.2 M or more. It is a photoelectric conversion element having a high value of 2 M or less and an oxygen permeation rate ratio r represented by the following formula (1) of 0.00040 to 0.00150 cm ³ (STP) / (day · mL).

Oxygen permeation rate ratio r = v / m (1)
(In the above formula (1), v represents the oxygen permeation rate (cm ³ (STP) / day) of the sealing portion represented by the following formula (2), and m represents the amount (mL) of the electrolyte. )

v = d × C × a / w (2)
(In the above formula (2), d represents the oxygen permeation coefficient (cm ³ (STP) · mm / (m ² · day · atm)) of the sealing portion, and a is the oxygen permeation area in the sealing portion. (M ² ) is represented, C represents the absolute value (atm) of the difference between the oxygen partial pressure inside the cell space and the oxygen partial pressure outside the cell space, and w is the width (mm) of the sealing portion. ) Represents)

The photoelectric conversion element of the present invention can have excellent light resistance while having excellent oxygen resistance even when placed under high illuminance.

The present inventors infer the reason why the above effect can be obtained by the photoelectric conversion element of the present invention as follows.

That is, in the photoelectric conversion element of the present invention, when the catalyst layer of the second electrode substrate contains the catalyst metal, the catalyst metal is dissolved in the electrolyte in a very small amount. When the photoelectric conversion element is placed under high illuminance in this state, the electrons excited by the first electrode substrate reduce the catalytic metal dissolved in the electrolyte and deposit it on the surface of the first electrode substrate, increasing the leakage current. Try to make it. At this time, if the amount of oxygen that penetrates into the electrolyte through the sealing portion is large, even if the catalyst metal is deposited, the catalyst metal is oxidized by the oxygen and dissolved in the electrolyte, and the state in which the leakage current is difficult to flow is maintained. To. However, if the amount of oxygen that penetrates into the electrolyte through the sealing portion is reduced in order to impart excellent oxygen resistance to the photoelectric conversion element, it becomes difficult for the precipitated catalyst metal to dissolve in the electrolyte due to oxygen, and leakage current occurs. Becomes easy to flow. On the other hand, when the imidazole compound is contained in the electrolyte, the imidazole compound is adsorbed on the catalyst metal and the leakage current from the catalyst metal is suppressed. At this time, if the concentration of the imidazole compound in the electrolyte is higher than 0.2 M and 2 M or less, the leakage current is effectively suppressed. In this way, the present inventors speculate that the above-mentioned effect may have been obtained by the photoelectric conversion element of the present invention.

In the photoelectric conversion element, it is preferable that the imidazole compound contains a benzimidazole compound.

In this case, the leakage current can be suppressed more sufficiently than when the imidazole compound uses an imidazole compound other than the benzimidazole compound.

In the present invention, "cm ³ (STP)" indicates that the volume of oxygen permeating the sealing portion is the standard state, that is, the volume measured under the conditions of 0 ° C. and 1 atm.

Further, in the present invention, the "oxygen permeation area in the sealing portion" means the product of the peripheral length of the outer circumference of the sealing portion and the height of the sealing portion. Here, the "perimeter of the outer circumference of the sealing portion" means "the circumference of the outer circumference of the sealing portion at the interface between the sealing portion and the first electrode substrate (hereinafter referred to as" first interface ")" and The shorter peripheral length of the "perimeter of the outer circumference of the sealing portion at the interface between the sealing portion and the second electrode substrate (hereinafter referred to as" second interface ")" is referred to as "at the first interface". When the "perimeter of the outer circumference of the sealing portion" and the "perimeter of the outer circumference of the sealing portion at the second interface" are the same length, the circumference is referred to. Further, the "height of the sealing portion" means the distance from the first interface to the second interface.

Further, in the present invention, the "width of the sealing portion" refers to the shorter of the "width of the sealing portion at the first interface" and the "width of the sealing portion at the second interface", and is referred to as "the width of the sealing portion". When the "width of the sealing portion at the first interface" and the "width of the sealing portion at the second interface" are the same width, the width is referred to.

According to the present invention, there is provided a photoelectric conversion element having excellent light resistance while having excellent oxygen resistance even when placed under high illuminance.

It is a cut surface end view which shows the embodiment of the photoelectric conversion element of this invention.

Hereinafter, embodiments of the photoelectric conversion element of the present invention will be described in detail with reference to FIG. FIG. 1 is a cut surface end view showing an embodiment of the photoelectric conversion element of the present invention.

As shown in FIG. 1, the photoelectric conversion element 100 includes one photoelectric conversion cell 50. The photoelectric conversion cell 50 is formed on the first electrode substrate 10, the second electrode substrate 20 facing the first electrode substrate 10, the oxide semiconductor layer 13 provided on the first electrode substrate 10, and the oxide semiconductor layer 13. The cell space formed by the sealing portion 30 for joining the adsorbed dye, the first electrode substrate 10 and the second electrode substrate 20, and the first electrode substrate 10, the second electrode substrate 20, and the sealing portion 30 is filled. The electrolyte 40 is provided. In the present embodiment, the second electrode substrate 20 has a conductive substrate 21 and a conductive catalyst layer 22, and the catalyst layer 22 contains a catalyst metal.

The electrolyte 40 contains an imidazole compound, and the concentration of the imidazole compound in the electrolyte 40 is higher than 0.2 M and 2 M or less.

Further, in the photoelectric conversion element 100, the oxygen permeation rate ratio r represented by the following formula (1) is 0.00040 to 0.00150 cm ³ (STP) / (day · mL).

Oxygen permeation rate ratio r = v / m (1)
(In the above formula (1), v represents the oxygen permeation rate (cm ³ (STP) / day) of the sealing portion 30 represented by the following formula (2), and m represents the amount of electrolyte (mL)).

v = d × C × a / w (2)
(In the above formula (2), d represents the oxygen permeation coefficient (cm ³ (STP) · mm / (m ² · day · atm)) of the sealing portion 30, and a is the oxygen permeation area in the sealing portion 30. (M ² ) is represented, C represents the absolute value (atm) of the difference between the oxygen partial pressure inside the cell space and the oxygen partial pressure outside the cell space, and w represents the width (mm) of the sealing portion 30. show)

The photoelectric conversion element 100 can have excellent light resistance while having excellent oxygen resistance even when placed under high illuminance.

Next, the first electrode substrate 10, the second electrode substrate 20, the oxide semiconductor layer 13, the sealing portion 30, the electrolyte 40, and the dye will be described in detail.

<First electrode substrate>
The first electrode substrate 10 includes a transparent substrate 11 and a transparent conductive layer 12 as an electrode provided on the transparent substrate 11 (see FIG. 1).

The material constituting the transparent substrate 11 may be a transparent material, and such transparent materials include, for example, borosilicate glass, soda lime glass, white plate glass, glass such as quartz glass, polyethylene terephthalate (PET), and the like. Insulating materials such as polyethylene naphthalate (PEN), polycarbonate (PC), and polyether sulfone (PES) can be mentioned. The thickness of the transparent substrate 11 is appropriately determined according to the size of the photoelectric conversion element 100, and is not particularly limited, but may be, for example, in the range of 50 μm to 40 mm.

Examples of the material constituting the transparent conductive layer 12 include conductive metal oxides such as tin-added indium oxide (ITO), tin oxide (SnO ₂ ), and fluorine-added tin oxide (FTO). The transparent conductive layer 12 may be a single layer or may be composed of a laminate of a plurality of layers composed of different conductive metal oxides. When the transparent conductive layer 12 is composed of a single layer, the transparent conductive layer 12 is preferably composed of FTO because it has high heat resistance and chemical resistance. The thickness of the transparent conductive layer 12 may be, for example, in the range of 0.01 to 2 μm.

<Second electrode substrate>
In the present embodiment, the second electrode substrate 20 includes a conductive substrate 21 and a conductive catalyst layer 22 (see FIG. 1).

The conductive substrate 21 is made of a metal material such as titanium, nickel, platinum, molybdenum, tungsten, aluminum, and stainless steel. In this case, the conductive substrate 21 serves both as a substrate and an electrode. Further, the conductive substrate 21 may be composed of a laminate in which the substrate and the electrode are separated and a transparent conductive layer made of a conductive oxide such as ITO or FTO is formed as an electrode on the above-mentioned insulating transparent substrate 11. good.

The thickness of the conductive substrate 21 is appropriately determined according to the size of the photoelectric conversion element 100, and is not particularly limited, but may be, for example, 5 μm to 4 mm.

The catalyst layer 22 contains a catalyst metal. Examples of the catalyst metal include platinum, gold, silver, palladium, rhodium and the like. When the conductive substrate 21 is made of a catalyst metal, the second electrode substrate 20 does not necessarily have to have the catalyst layer 22. In this case, the conductive substrate 21 also serves as the catalyst layer 22.

<Oxide semiconductor layer>
The oxide semiconductor layer 13 is composed of oxide semiconductor particles. Oxide semiconductor particles include, for example, titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), zinc oxide (ZnO), tungsten oxide (WO ₃ ), niobium oxide (Nb ₂ O ₅ ), strontium titanate (SrTiO ₃ ). , Tin oxide (SnO ₂ ) or two or more of these.

The thickness of the oxide semiconductor layer 13 is not particularly limited, but is usually 2 to 40 μm, preferably 10 to 30 μm.

<Sealing part>
The sealing portion 30 has an endless shape when the sealing portion 30 is viewed in the thickness direction of the sealing portion 30, and has an opening inside. The shape of the opening is not particularly limited, and examples of the shape of the opening include a circular shape and a polygonal shape such as a quadrangle.

The material constituting the sealing portion 30 is not particularly limited, but the material constituting the sealing portion 30 includes, for example, a modified polyolefin resin, a thermoplastic resin such as a vinyl alcohol polymer, and an ultraviolet curable resin. Resins such as. Examples of the modified polyolefin resin include ionomer, maleic anhydride-modified polyolefin, ethylene-vinylacetic acid anhydride copolymer, ethylene-methacrylate copolymer and ethylene-vinyl alcohol copolymer. Of these, maleic anhydride-modified polyolefin is preferable. In this case, higher adhesive strength can be obtained with respect to the first electrode substrate 10 and the second electrode substrate 20.

The oxygen permeation rate v of the sealing portion 30 is represented by the above formula (2) and is not particularly limited, but is preferably 0.00006 to 0.00030 cm ³ (STP) / day. In this case, unevenness in the output density in the surface (power generation surface) when the oxide semiconductor layer 13 is viewed from the first electrode substrate 10 side in a plan view is less likely to occur.

Further, C in the above equation (2) is an absolute value of the difference between the oxygen partial pressure inside the cell space and the oxygen partial pressure outside the cell space. For example, under atmospheric pressure, the oxygen partial pressure outside the cell space is usually 0.209 atm, and this oxygen partial pressure is usually sufficiently larger than the oxygen partial pressure inside the cell space, so that C is 0.209. It can be approximated to (atm). If the oxygen partial pressure outside the cell space changes, the value of C also changes.

Further, the oxygen permeation area a in the above formula (2) represents the product of the height (thickness) of the sealing portion 30 and the peripheral length of the outer periphery of the sealing portion 30.

Further, the width w in the above formula (2) represents the width of the sealing portion 30, and corresponds to the permeation distance of oxygen in the sealing portion 30.

The ratio (a / w) of the oxygen permeation area a and the width w in the above formula (2) is not particularly limited, but a / w is preferably 0.0012 to 0.0070. In this case, the oxygen resistance of the photoelectric conversion element 100 can be further improved by further improving the shape stability of the sealing portion 30.

The oxygen permeability coefficient d in the above formula (2) is not particularly limited, but is preferably 0.03 to 300 cm ³ (STP) · mm / (m ² · day · atm). In this case, oxygen permeation from the sealing portion 30 is compared with the case where the oxygen permeability coefficient d in the above formula (2) is less than 0.03 cm ³ (STP) · mm / (m ² · day · atm). The width w of the sealing portion 30 is set in order to keep the oxygen permeation rate ratio r within a certain range (0.00040 to 0.00150 cm ³ (STP) / (day · mL)) without making the velocity v extremely small. It is not necessary to make it extremely small, and more sufficient adhesive strength can be obtained between the sealing portion 30 and the first electrode substrate 10 and between the sealing portion 30 and the second electrode substrate 20. Further, the oxygen permeation ability of the sealing portion 30 can be further reduced as compared with the case where d in the above formula (2) is larger than 300 cm ³ (STP) · mm / (m ² · day · atm), and thus sealed. Deterioration of the electrolyte 40 due to oxygen permeation from the portion 30 can be more sufficiently suppressed. As a result, the oxygen resistance of the photoelectric conversion element 100 is further improved.

The oxygen permeability coefficient d in the above formula (2) is more preferably 0.15 to 300 cm ³ (STP) · mm / (m ² · day · atm). In this case, the material constituting the sealing portion 30 may be placed under reduced pressure in advance, and a material from which oxygen contained in the material constituting the sealing portion 30 has been removed can be used. This is because when the oxygen permeability coefficient d is 0.15 cm ³ (STP) · mm / (m ² · day · atm) or more, the oxygen permeability coefficient d is 0.15 cm ³ (STP) · mm / (m ² ·). This is because oxygen is more easily removed under reduced pressure as compared with the case where it is less than day · atm). Therefore, the oxygen permeation ability can be further reduced, and the deterioration of the oxygen resistance of the photoelectric conversion element 100 can be more sufficiently suppressed.

The height of the sealing portion 30 is not particularly limited, but is preferably 60 μm or less. In this case, as compared with the case where the height of the sealing portion 30 exceeds 60 μm, a large amount of oxygen is less likely to enter the inside of the cell space, the decrease in the output of the photoelectric conversion element 100 is more sufficiently suppressed, and the photoelectric conversion is performed. The element 100 can have better oxygen resistance. However, considering the adhesiveness of the sealing portion 30 to the first electrode substrate 10 and the second electrode substrate 20, the height of the sealing portion 30 is preferably 8 μm or more.

<Electrolyte>
The electrolyte 40 contains a redox pair, an organic solvent, and an imidazole compound.

The oxidation-reduction pair includes an oxidation-reduction pair containing a halogen atom such as an iodide ion / polyiodide ion (for example, I ⁻ / I _3- ⁾ , a bromide ion / poly bromide ion, and a zinc complex, an iron complex, and a cobalt complex. Redox pairs such as. The iodide ion / polyiodide ion can be formed by iodine (I ₂ ) and a salt (ionic liquid or solid salt) containing iodide (I ⁻ ) as an anion. When using an ionic liquid having iodide as an anion, only iodine may be added, and when using an organic solvent or an ionic liquid other than iodide as an anion, as an anion such as LiI or tetrabutylammonium iodide. A salt containing anionide (I ⁻ ) may be added.

Further, the electrolyte 40 usually contains an organic solvent. As the organic solvent contained in the electrolyte 40, acetonitrile, methoxyacetonitrile, methoxypropionitrile, propionitrile, ethylene carbonate, propylene carbonate, diethyl carbonate, γ-butyrolactone, valeronitrile, pivalonitrile and the like can be used.

Further, as the electrolyte 40, an ionic liquid may be used instead of the organic solvent. As the ionic liquid, for example, a known iodine salt such as a pyridinium salt, an imidazolium salt, or a triazolium salt, which is a room temperature molten salt that is in a molten state near room temperature is used. Examples of such a room temperature molten salt include 1-hexyl-3-methylimidazolium iodide, 1-ethyl-3-propylimidazolium iodide, 1-ethyl-3-methylimidazolium iodide, 1,2. -Dimethyl-3-propylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, or 1-methyl-3-propylimidazolium iodide is preferably used.

Further, as the electrolyte 40, a mixture of the ionic liquid and the organic solvent may be used instead of the organic solvent.

（上記式（１）中、Ｒ^１～Ｒ^４はそれぞれ独立に、水素原子、炭素数１～４の炭化水素基、－ＳＲ^５又は－ＯＲ^６を表す。Ｒ^５及びＲ^６はそれぞれ独立に、水素原子又は脂肪族炭化水素基を表す。） (Imidazole compound)
Electrolyte 40 contains an imidazole compound. As the imidazole compound contained in the electrolyte 40, for example, a benzimidazole compound or an imidazole compound represented by the following formula (1) (hereinafter referred to as “imidazole compound A”) can be used.

(In the above formula (1), R ¹ to R ⁴ independently represent a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, -SR ⁵ or -OR ⁶ , and R ⁵ and R ⁶ are independent of each other. Represents a hydrogen atom or an aliphatic hydrocarbon group.)

The benzimidazole compound may be an unsubstituted benzimidazole compound or a substituted benzimidazole compound having a substituent. Examples of the substituent include a hydrocarbon group, a nitrile group, a sulfonyl group, a phosphonyl group and the like.

In the benzoimidazole compound, examples of the hydrocarbon group as a substituent include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group, but fat is used from the viewpoint of more sufficiently suppressing leakage current. Group hydrocarbon groups are preferred. The number of carbon atoms of the aliphatic hydrocarbon group is not particularly limited, but is preferably 1 to 4. The aliphatic hydrocarbon group may be linear or branched, but it is linear because it has a larger intramolecular force against other molecules and it is easier to form a barrier layer that suppresses leakage current more densely. It is preferably in the form of a shape. Further, the aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated hydrocarbon group, but it is preferably a saturated aliphatic hydrocarbon group because it does not easily react with the oxidation-reduction pair in the electrolyte 40.

Further, the hydrocarbon group as a substituent may be one that replaces a hydrogen atom bonded to a carbon atom of a benzene ring or one that replaces a hydrogen atom bonded to an imidazole ring, but a hydrogen atom bonded to the imidazole ring may be used. It is preferable to replace it. In this case, the leakage current can be suppressed more sufficiently than in the case where the hydrocarbon group as the substituent replaces the hydrogen atom of the benzene ring.

Specific examples of the benzimidazole compound include, for example, 1-butylbenzimidazole (NBB), 1-methylbenzimidazole (NMB), trimethylbenzoimidazole, 1-propylbenzimidazole and 1,2-dimethylbenzimidazole. Will be. These may be used alone or in combination of two or more.

The imidazole compound A is represented by the above formula (1).

In the above formula (1), examples of the hydrocarbon group represented by R ¹ to R ⁴ include an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be linear or branched. Further, the aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated hydrocarbon group.

The carbon number of the aliphatic hydrocarbon group represented by R5 and R6 is not particularly limited, but is, for example, ¹ to ³ .

Specific examples of the imidazole compound A include 1-methylimidazole (MI), isopropylimidazole (IPI ), dimethylimidazole , ethylmethylimidazole, dimethylpropylimidazole, butylmethylimidazole, methylpropylimidazole and methylbenzoimidazole. Will be. These may be used alone or in combination of two or more.

Further, the imidazole compound may be composed of one kind of imidazole compound or may be composed of a plurality of kinds of imidazole compounds.

As the imidazole compound, a benzimidazole compound is preferable. In this case, the leakage current can be suppressed more sufficiently than in the case where the imidazole compound is an imidazole compound other than the benzimidazole compound.

The concentration of the imidazole compound in the electrolyte 40 is preferably 0.3 to 1.8 M.

When the concentration of the imidazole compound in the electrolyte 40 is within the above range, the leakage current can be suppressed more sufficiently than when the concentration of the imidazole compound in the electrolyte 40 is outside the above range.

The concentration of the imidazole compound in the electrolyte 40 is more preferably 0.5 to 1.65 M.

Further, an additive can be added to the electrolyte 40. Examples of the additive include 4-t-butylpyridine, guanidium thiocyanate and the like.

Further, as the electrolyte 40, a nanocomposite gel electrolyte, which is a pseudo-solid electrolyte obtained by kneading nanoparticles such as SiO ₂ , TiO ₂ and carbon nanotubes with the above electrolyte to form a gel, may be used, or polyvinylidene fluoride. , An electrolyte gelled with an organic gelling agent such as a polyethylene oxide derivative or an amino acid derivative may be used.

The ratio of the amount m of the electrolyte 40 to the oxygen permeation rate v of the sealing portion 30, that is, the oxygen permeation rate ratio r represented by the above formula (1) is 0.00040 to 0.00150 cm ³ (STP) / (day).・ ML). In this case, the photoelectric conversion element 100 can have better oxygen resistance than the case where r represented by the above formula (1) is out of the above range.

The r of the above formula (1) is preferably 0.00005 to 0.00100 cm ³ (STP) / (day · mL). In this case, unevenness in the output density in the surface (power generation surface) when the oxide semiconductor layer 13 is viewed from the first electrode substrate 10 side in a plan view is less likely to occur.

<Dye>
Examples of the dye include a ruthenium complex having a ligand including a bipyridine structure and a terpyridine structure, a photosensitizing dye such as an organic dye such as porphyrin, eosin, rhodinin, and merocyanin, and an organic dye such as a lead halide perovskite crystal. Examples include inorganic composite dyes. As the lead-halogenated perovskite, for example, CH ₃ NH ₃ PbX ₃ (X = Cl, Br, I) is used. Here, when a photosensitizing dye is used as the dye, the photoelectric conversion element 100 becomes a dye-sensitized electric conversion element, and the photoelectric conversion cell 50 becomes a dye-enhanced photosensitive electric conversion cell.

Among the above dyes, a photosensitizing dye composed of a ruthenium complex having a bipyridine structure or a ligand containing a terpyridine structure is preferable. In this case, the photoelectric conversion characteristics of the photoelectric conversion element 100 can be further improved.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the first electrode substrate 10 has a transparent substrate 11, and the oxide semiconductor layer 13 is provided on the transparent substrate 11 via the transparent conductive layer 12, but the oxide semiconductor layer 13 is the first. It may be provided on the conductive substrate 21 of the two-electrode substrate 20. However, in this case, the catalyst layer 22 is provided on the transparent conductive layer 12 of the first electrode substrate 10.

Further, in the above embodiment, the photoelectric conversion element 100 includes one photoelectric conversion cell 50, but the photoelectric conversion element may include a plurality of photoelectric conversion cells 50.

Hereinafter, the content of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

(Example 1)
First, a quadrangular opening was formed in a film of 5.4 cm × 5.4 cm to obtain a sealing portion forming body for forming a sealing portion. At this time, the constituent material of the sealing portion forming body is maleic anhydride-modified polyethylene (trade name: Binel 4164, manufactured by DuPont, oxygen permeability coefficient d: 195 cm ³ (STP) · mm / (m ² · day · atm). )) Was used.

Next, a laminate formed by forming a transparent conductive layer made of 0.6 μm FTO on a transparent substrate of 10 cm × 10 cm × 2.2 mm made of glass was prepared.

Next, a precursor of the oxide semiconductor layer was formed on the transparent conductive layer. The precursor of the oxide semiconductor layer is a rectangular titanium oxide porous film having a thickness of 5 cm × 5 cm × 10 μm by printing titanium oxide nanopaste on a transparent conductive layer and then heating and firing at 460 ° C. for 90 minutes. An oxide semiconductor layer made of the above was obtained. In this way, the structure was obtained.

On the other hand, a photosensitizing dye made of Z907 was dissolved in a mixed solvent of t-butanol and acetonitrile to obtain a dye solution.

Then, the structure obtained as described above was immersed in the dye solution overnight to adsorb the photosensitizing dye on the surface of the oxide semiconductor layer. Then, the sealing portion forming body prepared as described above was arranged on the transparent conductive layer so as to surround the oxide semiconductor layer.

Next, 0.15 mL of the electrolyte was added dropwise onto the oxide semiconductor layer. As the electrolyte, iodine, 1,2-dimethyl-3-propylimidazolium iodide, and 1-butylbenzimidazole (NBB) are added to a solvent composed of 3-methoxypropionitrile under an argon atmosphere. Obtained by. At this time, the concentrations of iodine, 1,2-dimethyl-3-propylimidazolium iodide and NBB in the electrolyte were set to 0.01M, 0.6M and 0.25M, respectively.

On the other hand, it is a facing substrate obtained by sputtering platinum on a titanium foil having a thickness of 0.04 mm so as to have a thickness of 5 nm, and is a second electrode substrate having a thickness of 5.4 cm × 5.4 cm × 0.04 mm. I prepared. At this time, on the surface of the titanium foil, the peripheral edge portion where the sealing portion was to be formed was masked so that the catalyst layer was not formed. Then, the sealing portion forming body obtained as described above was placed on the peripheral portion of the titanium foil of the second electrode substrate on which the catalyst layer was not formed, and bonded by the thermal laminating method. In this way, the second electrode substrate on which the sealing portion forming body was formed was prepared.

Then, the second electrode substrate on which the sealing portion forming body is formed is arranged so as to face the above structure via the sealing portion forming body, and the sealing forming body is pressed while heating at 190 ° C. to be transparent. The conductive layer and the second electrode substrate were adhered to each other. At this time, by applying sufficient stress to the sealing portion forming body, a sealing portion having a thickness (height) of 0.0050 cm (50 μm) and a width of 2 mm was obtained. Here, by setting the outer peripheral length of the sealing portion to 21 cm and the thickness (height) of the sealing portion to 0.0050 cm (50 μm), the height of the sealed portion and the peripheral length of the outer circumference of the sealed portion are set. The oxygen permeation area a, which is the product of the above, was 0.105 × 10 ^-4 m ² . In this way, a photoelectric conversion element was obtained.

For the photoelectric conversion element obtained as described above, the ratio of the amount m (mL) of the electrolyte represented by the following formula (1) to the oxygen permeation rate v (cm ³ (STP) / day) of the sealing portion. The oxygen permeation rate ratio r (cm ³ (STP) / (day · mL)) and the oxygen permeation rate v (cm ³ (STP) / day) represented by the following formula (2) were determined. The results are shown in Table 1. In the formula (2), the value of C is 0.209 (atm) because the oxygen partial pressure outside the cell space is 0.209 atm and the oxygen partial pressure inside the cell space is about 0 atm. Was used.

Oxygen permeation rate ratio r = v / m (1)
(In the above formula (1), v represents the oxygen permeation rate (cm ³ (STP) / day) of the sealed portion represented by the following formula (2), and m represents the amount of electrolyte (mL)).

v = d × C × a / w (2)
(In the above formula (2), d represents the oxygen permeation coefficient of the sealing portion (cm ³ (STP) · mm / (m ² · day · atm)), and a represents the oxygen permeation area (m) in the sealing portion. ² ), C represents the absolute value (atm) of the difference between the oxygen partial pressure inside the cell space and the oxygen partial pressure outside the cell space, and w represents the width (mm) of the sealing portion).

(Examples 2 to 4 and Comparative Examples 1 to 4)
Imidazole compound concentration in electrolyte, electrolytic mass m, oxygen permeation coefficient d of sealing part, height h, outer circumference length, height h × outer circumference length, oxygen permeation area a, width w, oxygen partial pressure p in the atmosphere, A photoelectric conversion element was produced in the same manner as in Example 1 except that the oxygen permeation rate v and the oxygen permeation rate ratio r were as shown in Table 1.

<Light resistance>
The photoelectric conversion elements of Examples 1 to 4 and Comparative Examples 1 to 4 obtained as described above were irradiated with 1 sun of pseudo-sunlight for 10 hours immediately after production, and then immediately irradiated with 200 lux of white light. The IV measurement was performed in 1 and the output value was calculated. Then, the output values of Examples 1 to 4 and Comparative Examples 1 to 4 were calculated as an output ratio R1 which is a relative value with the output value of Comparative Example 1 as 100. This output ratio R1 was used as an index of light resistance. The results are shown in Table 1. The output value of Comparative Example 1 was set to 100 (reference) because it is considered that the lower the concentration of the benzimidazole compound in the electrolyte, the lower the light resistance. Therefore, the concentration of the benzimidazole compound in the electrolyte in Comparative Example 1 is considered to be lower. Is the lowest among Examples 1 to 4 and Comparative Examples 1 to 4. The light source, illuminance meter, and power supply used for IV measurement are as follows.

Light source: White LED (product name "LEL-SL5N-F", manufactured by Toshiba Lighting & Technology Corporation)
Illuminance meter: Product name "Digital Illuminance Meter 51013", Yokogawa Meter & Instruments Power Supply: Voltage / Current Generator (Product name "R6246I", ADVANTEST)

The acceptance criteria for light resistance are as follows.
(Pass criteria) Output ratio R1 is larger than 100

<Oxygen resistance>
The photoelectric conversion elements of Examples 1 to 4 and Comparative Examples 1 to 4 are separately prepared, and these photoelectric conversion elements are heated in an oven at 85 ° C. in dry air for 1000 hours and then placed in a dark place at 20 ° C. 24. After allowing to stand for a while, IV measurement was performed in a state of irradiating with white light of 200 lux, and an output value was calculated. Then, the output values of Examples 1 to 4 and Comparative Examples 1 to 4 were calculated as an output ratio R2 which is a relative value with the output value of Comparative Example 2 as 100. This output ratio R2 was used as an index of oxygen resistance. The results are shown in Table 1. The output value of Comparative Example 2 was set to 100 (reference) because the larger the oxygen permeation rate ratio r of the sealed portion, the lower the oxygen resistance, and the oxygen permeation rate ratio r in Comparative Example 2 was from Example 1 to Example 1. This is because it is the largest of 4 and Comparative Examples 1 to 4. Further, as the light source, the illuminance meter and the power source used for the IV measurement, the same light source, the illuminance meter and the power source as those used for the measurement of the output ratio R1 were used. Further, in Table 1, "-" indicates that the output could not be calculated because the sealing portion was peeled off.

The acceptance criteria for oxygen resistance are as follows.
(Pass criteria) Output ratio R2 is greater than 100 or not "-"

As shown in Table 1, it was found that the photoelectric conversion elements of Examples 1 to 4 satisfy the acceptance criteria in terms of oxygen resistance and light resistance. On the other hand, it was found that the photoelectric conversion elements of Comparative Examples 1 to 4 did not satisfy the acceptance criteria in at least one of oxygen resistance and light resistance.

From the above results, it was confirmed that the photoelectric conversion element of the present invention has excellent light resistance while having excellent oxygen resistance even when placed under high illuminance.

10 ... 1st electrode substrate 13 ... Oxide semiconductor layer 20 ... 2nd electrode substrate 22 ... Catalyst layer 30 ... Sealing part 40 ... Electrolyte 50 ... Photoelectric conversion cell 100 ... Photoelectric conversion element

Claims (2)

With at least one photoelectric conversion cell
The photoelectric conversion cell
The first electrode substrate and
The second electrode substrate facing the first electrode substrate and
With the oxide semiconductor layer provided on the first electrode substrate or the second electrode substrate,
A sealing portion for joining the first electrode substrate and the second electrode substrate, and
The first electrode substrate, the second electrode substrate, and the electrolyte filled in the cell space formed by the sealing portion are provided.
The second electrode substrate has a catalyst layer containing a catalyst metal and has a catalyst layer.
The electrolyte contains an imidazole compound and contains
The concentration of the imidazole compound in the electrolyte is higher than 0.2 M and 2 M or less.
A photoelectric conversion element having an oxygen permeation rate ratio r represented by the following formula (1) of 0.00040 to 0.00150 cm ³ (STP) / (day · mL).

Oxygen permeation rate ratio r = v / m (1)
(In the above formula (1), v represents the oxygen permeation rate (cm ³ (STP) / day) of the sealing portion represented by the following formula (2), and m represents the amount (mL) of the electrolyte. )

v = d × C × a / w (2)
(In the above formula (2), d represents the oxygen permeation coefficient (cm ³ (STP) · mm / (m ² · day · atm)) of the sealing portion, and a is the oxygen permeation area in the sealing portion. It represents a (m ² ), C represents the absolute value (atm) of the difference between the oxygen partial pressure inside the cell space and the oxygen partial pressure outside the cell space, and w represents the width of the sealing portion (atm). Represents mm) The photoelectric conversion element according to claim 1, wherein the imidazole compound contains a benzimidazole compound.

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