JP6863858B2 - 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 attracted attention because it is inexpensive and high photoelectric conversion efficiency can be obtained, and various developments have been made on the photoelectric conversion element using a dye.

As a photoelectric conversion element using such a dye, for example, the dye-sensitized electric conversion element for low illuminance of Patent Document 1 below is known. The following Patent Document 1 describes a transparent conductive substrate having a transparent conductive film provided on a transparent substrate and a transparent substrate, and a working electrode provided with an oxide semiconductor layer provided on the transparent conductive substrate, and a counter electrode facing the working electrode. The photosensitizing dye adsorbed on the oxide semiconductor layer, the sealing portion connecting the working electrode and the counter electrode, and the electrolyte filled in the cell space surrounded by the working electrode, the counter electrode and the sealing portion. A dye-sensitized solar cell for low light having a concentration _{of I 3} ⁻ in an electrolyte of 10 mmol / L or less is disclosed.

Japanese Unexamined Patent Publication No. 2013-201099

However, the photoelectric conversion element described in Patent Document 1 described above has room for improvement in terms of durability when the concentration of polyhalide ions in the electrolyte is low (for example, when it is 0.05 M or less). Was there.

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 durability when the concentration of polyhalide ions in an electrolyte is low.

The present inventors have investigated the causes of the above-mentioned problems in the photoelectric conversion element described in Patent Document 1. As a result, in the photoelectric conversion element described in Patent Document 1, when the concentration of the polyhalide ion in the electrolyte is low (for example, when it is 0.05 M or less), the permeation rate of oxygen into the electrolyte is too high. The present inventors have noticed that the durability is lowered even if the permeation rate of oxygen into the electrolyte is too low. Therefore, as a result of further diligent research, the present inventors have made a ratio of the amount of oxygen permeated into the sealing portion per day, that is, the oxygen permeation rate into the sealing portion and the amount of electrolyte in the sealing portion. We have found that the above-mentioned problems can be solved when the above-mentioned problem is within a certain range, and have completed the present invention.

That is, the present invention includes at least one photoelectric conversion cell, and the photoelectric conversion cell includes an electrode substrate, an opposing substrate facing the electrode substrate, and an oxide semiconductor layer provided on the electrode substrate or the opposing substrate. An annular sealing portion that joins the electrode substrate and the facing substrate, and an electrolyte that fills the cell space formed by the electrode substrate, the facing substrate, and the sealing portion, and the electrolyte is a halide. It contains a redox pair consisting of an ion and a polyhalide ion, the concentration of the polyhalide ion in the electrolyte is 0.05 M or less, and R represented by the following formula (1) is 0.00040 to 0. It is a photoelectric conversion element having 00200 cm ³ (STP) / (day · mL).

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 durability when the concentration of the polyhalide ion in the electrolyte is low (when the concentration is 0.05 M or less).

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, it is possible to prevent a large amount of oxygen from entering the cell space with respect to the amount of electrolyte. Therefore, when light is incident on the photoelectric conversion element, the polyhalide ion in the electrolyte is considered to be due to the progress of the oxidation reaction from the halide ion to the polyhalide ion following the activation of the invading oxygen. The increase in concentration is less likely to proceed, and the decrease in maximum output operating current is sufficiently suppressed. Further, according to the photoelectric conversion element of the present invention, it is suppressed that oxygen does not completely penetrate into the cell space with respect to the amount of electrolyte, and the reduction reaction from the polyhalide ion to the halide ion causes the reaction. The decrease in the concentration of polyhalide ions in the electrolyte, which is thought to be the case, is less likely to proceed, and the decrease in the maximum output operating current is less likely to occur. As described above, according to the photoelectric conversion element of the present invention, the maximum output operating current is lowered even though the concentration of the polyhalide ion in the electrolyte is low and the rate of change in the concentration of the polyhalide ion is large. It becomes difficult. As a result, the decrease in the maximum output of the photoelectric conversion element is more sufficiently suppressed. Therefore, it is considered that the photoelectric conversion element of the present invention can have excellent durability when the concentration of the polyhalide ion in the electrolyte is low.

In the photoelectric conversion element, the oxygen permeability coefficient d in the formula (2) is preferably 46 to 195 cm ³ (STP) · mm / (m ² · day · atm).

In this case, the width w of the sealing portion is sufficiently increased as compared with the case where the oxygen permeation coefficient d in the above formula (2) ^{is less than 46 cm 3} (STP) · mm / (m ^{2 · day · atm).} This makes it possible to increase the adhesive area between the sealing portion and the electrode substrate and the adhesive area between the sealing portion and the opposing substrate, so that the adhesiveness between the sealing portion and the electrode substrate and the sealing can be increased. The adhesiveness between the stop and the facing substrate is further improved. As a result, the durability of the photoelectric conversion element is further improved. Further, since the oxygen permeability of the sealing portion can be further reduced as compared with the case where d in the above formula (2) is ^{larger than 195 cm 3} (STP) · mm / (m ^{2 · day · atm), the sealing portion} Oxidation of the adhesive surface between the electrode substrate and the electrode substrate and oxidation of the adhesive surface between the sealing portion and the opposing substrate are more sufficiently suppressed. Therefore, the deterioration of the adhesiveness between the sealing portion and the electrode substrate and the adhesiveness between the sealing portion and the opposing substrate is more sufficiently suppressed. As a result, the durability of the photoelectric conversion element is further improved.

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 annular sealing portion and the height of the sealing portion. Here, the "peripheral length of the outer circumference of the sealing portion" means "the peripheral length of the outer circumference of the sealing portion at the interface between the sealing portion and the electrode substrate (hereinafter, referred to as" first interface ")" and "sealing". The shorter of the "perimeter of the outer circumference of the sealing portion at the interface between the stop portion and the facing substrate (hereinafter referred to as" the second interface ")", which is the shorter circumference of the sealing portion at the first interface. When the "perimeter of the outer circumference" 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" is the shorter of the "width of the annular sealing portion at the first interface" and the "width of the annular sealing portion at the second interface". When the "width of the annular sealing portion at the first interface" and the "width of the annular 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 durability when the concentration of polyhalide ions in the electrolyte is low.

It is a cut surface end view which shows 1st Embodiment of the photoelectric conversion element of this invention. It is a cut surface end view which shows the 2nd Embodiment of the photoelectric conversion element of this invention.

Hereinafter, the first embodiment 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 a first 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 includes an electrode substrate 10, an opposing substrate 20 facing the electrode substrate 10, an oxide semiconductor layer 13 provided on the electrode substrate 10, a dye adsorbed on the oxide semiconductor layer 13, and an electrode substrate. An annular sealing portion 30 for joining the 10 and the facing substrate 20 and an electrolyte 40 filled in the cell space formed by the electrode substrate 10, the facing substrate 20 and the sealing portion 30 are provided.

The electrolyte 40 contains a redox pair composed of a halide ion and a polyhalide ion, and the concentration of the polyhalide ion in the electrolyte 40 is 0.05 M or less.

Further, in the photoelectric conversion element 100, R represented by the following formula (1) is 0.00040 to 0.00200 cm ³ (STP) / (day · mL).

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. Represent)

The photoelectric conversion element 100 can have excellent durability when the concentration of polyhalide ions in the electrolyte 40 is low.

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

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

The material constituting the transparent substrate 11 may be a transparent material, and examples of such a transparent material include 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 to 40,000 μm.

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.

<Opposite board>
In the present embodiment, the facing 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, 0.005 to 4 mm.

The catalyst layer 22 is made of platinum, a carbon-based material, a conductive polymer, or the like. Here, carbon nanotubes are preferably used as the carbon-based material. The facing substrate 20 does not have to have the catalyst layer 22 when the conductive substrate 21 has a catalytic function (for example, when it contains carbon or the like).

<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 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-vinyl acetate 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 electrode substrate 10 and the opposing 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 0.000016 to 0.00027 cm 3} (STP) / day. In this case, unevenness of the output density in the surface (power generation surface) when the oxide semiconductor layer 13 is viewed from the 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. Can be approximated to (atm). If the oxygen partial pressure outside the cell space changes, the value of C also changes.

Further, the 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 circumference 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 transmission area a and the width w in the above formula (2) is not particularly limited, but a / w is preferably 0.0005 to 0.0070. In this case, the durability 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 46 to 195 cm 3} (STP) · mm / (m ² · day · atm). In this case, the width w of the sealing portion 30 is sufficiently larger than that in the case where the oxygen permeation coefficient d in the above formula (2) ^{is less than 46 cm 3} (STP) · mm / (m ^{2 · day · atm).} Since it is possible to increase the size and increase the adhesive area between the sealing portion 30 and the electrode substrate 10 and the adhesive area between the sealing portion 30 and the opposing substrate 20, the sealing portion 30 and the electrode substrate 10 can be increased. The adhesiveness between the sealing portion 30 and the facing substrate 20 is further improved. As a result, the durability of the photoelectric conversion element 100 is further improved. Further, the oxygen permeability of the sealing portion 30 can be further reduced as compared with the case where d in the above formula (2) is ^{larger than 195 cm 3} (STP) · mm / (m ^{2 · day · atm), so that the sealing portion 30 can be sealed.} Oxidation of the adhesive surface between the portion 30 and the electrode substrate 10 and oxidation of the adhesive surface between the sealing portion 30 and the opposing substrate 20 are more sufficiently suppressed. Therefore, the deterioration of the adhesiveness between the sealing portion 30 and the electrode substrate 10 and the adhesiveness between the sealing portion 30 and the opposing substrate 20 is more sufficiently suppressed. As a result, the durability of the photoelectric conversion element 100 is further improved.

The oxygen permeability coefficient d in the above formula (2) ^{is more preferably 60 to 160 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. As a result, the oxygen permeation ability can be further reduced, and the decrease in durability of the photoelectric conversion element 100 due to the permeation of oxygen can be more sufficiently suppressed.

The height of the sealing portion 30 is not particularly limited, but is preferably 40 μm or less. In this case, as compared with the case where the height of the sealing portion 30 exceeds 40 μm, a large amount of oxygen is less likely to penetrate into the cell space, and when the photoelectric conversion element 100 is irradiated with light, the activity of the penetrated oxygen is reduced. The decrease in the maximum output operating current due to the progress of the oxidation reaction from the halide ion to the polyhalide ion following the conversion is more sufficiently suppressed. As a result, the decrease in the output of the photoelectric conversion element 100 is more sufficiently suppressed, and the photoelectric conversion element 100 can have more excellent durability. The height of the sealing portion 30 is preferably 25 μm or less. However, considering the adhesiveness of the sealing portion 30 to the electrode substrate 10 and the opposing substrate 20, the height of the sealing portion 30 is preferably 10 μm or more.

<Electrolyte>
As described above, the electrolyte 40 contains a redox pair composed of a halide ion and a polyhalide ion, and the concentration of the polyhalide ion in the electrolyte 40 is 0.05 M or less. When the concentration of the polyhalide ion in the electrolyte 40 exceeds 0.05 M, the output of the photoelectric conversion element 100 is less likely to decrease regardless of the value of R. However, the concentration of the polyhalide ion in the electrolyte 40 is preferably 0.002M or more. In this case, higher power generation performance can be obtained in an environment with high illuminance as compared with the case where the concentration of the polyhalide ion in the electrolyte 40 is less than 0.002M.

The redox pair may be any one composed of a halide ion and a polyhalide ion. Examples of such redox pairs include redox pairs such as iodide ion and polyiodide ion, bromide ion (bromine ion) and polybromide ion. The iodide ion and the 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 needs to be added, and when using an organic solvent or an ionic liquid other than iodide as an anion, it is used as an anion such as LiI or tetrabutylammonium iodide. iodide (I ^-) may be added salt containing.

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-propyl imidazolium iodide, 1-butyl-3-methyl imidazolium iodide, or 1-methyl-3-propyl imidazolium 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.

Further, an additive can be added to the electrolyte 40. Examples of the additive include LiI, 4-t-butylpyridine, guanidiam thiocyanate, 1-methylbenzimidazole, 1-butylbenzimidazole 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 into the 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, R represented by the above formula (1) is 0.00040 to 0.00200 cm ³ (STP) / (day · mL). is there. In this case, the decrease in the maximum output operating current is less likely to occur as compared with the case where R represented by the above equation (1) is out of the above range, and as a result, the decrease in the maximum output of the photoelectric conversion element 100 is more sufficient. It is suppressed. Therefore, the photoelectric conversion element 100 can have excellent durability when the concentration of the polyhalide ion in the electrolyte 40 is low.

The R of the above formula (1) is preferably 0.00090 to 0.00150 cm ³ (STP) / (day · mL). In this case, unevenness of the output density in the surface (power generation surface) when the oxide semiconductor layer 13 is viewed from the 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 containing a bipyridine structure, a terpyridine structure, and the like, a photosensitizing dye such as an organic dye such as porphyrin, eosin, rodanine, 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-sensitized electric conversion cell.

Among the above dyes, a photosensitizing dye composed of a ruthenium complex having a ligand containing a bipyridine structure or 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 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 opposed substrate 20. It may be provided on the conductive substrate 21 of the above. However, in this case, the catalyst layer 22 is provided on the transparent conductive layer 12 of the electrode substrate 10.

Further, in the above embodiment, the conductive substrate 21 and the catalyst layer 22 form the opposing substrate 20, but as in the photoelectric conversion element 200 shown in FIG. 2, the photoelectric conversion cell 250 serves as the opposing substrate. Insulating substrate 220 may be used instead of 20. In this case, the structure 202 is arranged in the space between the insulating substrate 220, the sealing portion 30, and the electrode substrate 10. The structure 202 is provided on the surface of the electrode substrate 10 on the insulating substrate 220 side. The structure 202 is composed of an oxide semiconductor layer 13, a porous insulating layer 203, and a counter electrode 201 in this order from the electrode substrate 10 side. Further, the electrolyte 40 is arranged in the above space. The electrolyte 40 is impregnated into the oxide semiconductor layer 13 and the porous insulating layer 203. Here, as the insulating substrate 220, for example, a glass substrate or a resin film can be used. Further, as the counter electrode 201, the same one as that of the facing substrate 20 can be used. Alternatively, the counter electrode 201 may be composed of a single porous layer containing, for example, carbon. The porous insulating layer 203 is mainly for preventing physical contact between the oxide semiconductor layer 13 and the opposing substrate 220 and impregnating the inside with the electrolyte 40. As such a porous insulating layer 203, for example, a fired oxide body can be used. In the photoelectric conversion element 200 shown in FIG. 2, only one structure 202 is provided in the space between the sealing portion 30, the electrode substrate 10, and the insulating substrate 220, but there are a plurality of structures 202. It may be provided. Further, although the porous insulating layer 203 is provided between the oxide semiconductor layer 13 and the counter electrode 201, it may be provided between the electrode substrate 10 and the counter electrode 201 so as to surround the oxide semiconductor layer 13. Good. Even with this configuration, physical contact between the oxide semiconductor layer 13 and the counter electrode 201 can be prevented.

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 having a size of 4.1 cm × 9.1 cm × a thickness of 20 μm to obtain an annular sealing portion forming body for forming a sealing portion. At this time, as the constituent material of the sealing portion forming body, maleic anhydride-modified polyethylene (maleic anhydride-modified PE) 1 (trade name: Binel 4164, manufactured by DuPont, density: 0.92 g / cm ³ , oxygen permeability coefficient). d: 195 cm ³ (STP) · mm / (m ² · day · atm)) was used.

Next, a laminate was prepared in which a transparent conductive layer made of 0.6 μm FTO was formed on a transparent substrate having a size of 5.5 cm × 11 cm × 2.2 mm made of glass.

Next, a precursor of the oxide semiconductor layer was formed on the transparent conductive layer. The precursor of the oxide semiconductor layer is a square oxide of 2.5 cm × 7.5 cm × thickness 20 μm by printing titanium oxide nanopaste on a transparent conductive layer, heating at 460 ° C. for 90 minutes and firing. An oxide semiconductor layer made of a titanium porous film was obtained. The structure was obtained in this way.

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 annular sealing portion forming body prepared as described above was arranged on the transparent conductive layer so as to surround the oxide semiconductor layer.

Next, 0.125 mL of the electrolyte was added dropwise onto the oxide semiconductor layer. The electrolyte was obtained by adding iodine and 1,2-dimethyl-3-propylimidazolium iodide to a solvent composed of 3-methoxypropionitrile under an argon atmosphere. At this time, _{the concentration of I 3} ⁻ in the electrolyte was set to 0.01 M.

On the other hand, a facing substrate having a thickness of 4.1 cm × 9.1 cm × 0.04 mm, which is an opposed 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, is prepared. did. At this time, on the surface of the titanium foil, masking was applied so that the catalyst layer was not formed on the peripheral edge portion where the sealing portion was to be formed. Then, the sealing portion forming body obtained as described above was placed on the peripheral portion of the titanium foil of the opposing substrate on which the catalyst layer was not formed, and bonded by the thermal laminating method. In this way, the opposed substrate on which the sealing portion forming body was formed was prepared.

Then, the opposing substrate on which the sealing portion forming body is formed is arranged so as to face the structure via the sealing portion forming body, and the sealing forming body is pressed while heating at 190 ° C. to form a transparent conductive layer. It was adhered to the facing substrate. At this time, by applying sufficient stress to the sealing portion forming body, an annular sealing portion having a thickness (height) of 10 μm and a width of 8 mm was obtained. Here, by setting the outer peripheral length of the sealing portion to 26.4 cm and the thickness (height) of the sealing portion to 10 μm, the product of the height of the sealing portion and the peripheral length of the outer circumference of the sealing portion is obtained. A certain transmission area a was set to 0.026 m ² . In this way, a photoelectric conversion element was obtained.

The photoelectric conversion element obtained as described above is represented by the ratio R of the amount m of the electrolyte represented by the following formula (1) and the oxygen permeation velocity v of the sealing portion, and the following formula (2). The oxygen permeation rate v was 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.

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 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 19, Comparative Examples 1 to 16, and Reference Examples 1 to 4)
Implemented except that the constituent materials of the sealing part, oxygen permeability coefficient d, outer peripheral circumference, height, permeation area a, width w, electrolyte amount m and I ₃ ^- concentration are as shown in Tables 1 to 3. A photoelectric conversion element was manufactured in the same manner as in Example 1.

In Comparative Examples 7 to 9 and Examples 13 to 14, an ethylene-vinyl alcohol copolymer (EVOH, trade name: EVAL, manufactured by Kuraray Co., Ltd., oxygen permeation coefficient d: 1 cm ^{3) was used as the resin constituting the sealing portion.} (STP) · mm / (m ² · day · atm)) was used, and in Comparative Examples 10 to 12 and Example 15, maleic anhydride-modified polyethylene (maleic anhydride-modified PE) was used as the resin constituting the sealing portion. For 2 (trade name: AMPLIFY GR 204, manufactured by Dow Chemical Company, density: 0.96 g / cm ³ , oxygen permeation coefficient d: 46 cm ³ (STP) · mm / (m ² · day · atm)) There was.

<Durability>
The IV curves of the photoelectric conversion elements of Examples 1 to 19, Comparative Examples 1 to 16 and Reference Examples 1 to 4 obtained as described above were measured in a state of being irradiated with white light of 200 lux immediately after production. _{The maximum output operating power Pm 0} (μW) calculated from this IV curve was calculated as “output 1”. The light source, illuminometer, and power supply used to measure the IV curve were 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)

Then, after leaving the photoelectric conversion element under white light irradiation of 20000 lux for 2000 hours, the IV curve is measured with the photoelectric conversion element irradiated with the white light of 200 lux again, and the maximum output operation calculated from this IV curve is performed. The power PW (μW) was calculated as “output 2”. Then, the output maintenance rate was calculated based on the following formula. The results are shown in Tables 1-3.

Output retention rate = output 2 / output 1

The acceptance criteria for durability are as follows.
(Pass criteria) Output maintenance rate must be 0.85 or higher

As shown in Tables 1 to 3, the photoelectric conversion elements of Examples 1 to 19 were found to satisfy the acceptance criteria in terms of durability. On the other hand, it was found that the photoelectric conversion elements of Comparative Examples 1 to 16 did not satisfy the acceptance criteria in terms of durability. From the results of Reference Examples 1 to 5, when the concentration of the polyhalide ion exceeds 0.05 M, the durability of the photoelectric conversion element does not change significantly regardless of the value of R represented by the formula (1). Ion.

From the above results, it was confirmed that the photoelectric conversion element of the present invention has excellent durability when the concentration of polyhalide ions in the electrolyte is low.

10 ... Electrode substrate 13 ... Oxide semiconductor layer 20 ... Opposing substrate 30 ... Sealing part 40 ... Electrolyte 50, 250 ... Photoelectric conversion cell 100, 200 ... Photoelectric conversion element 220 ... Insulating substrate (opposing substrate)

Claims (2)

With at least one photoelectric conversion cell
The photoelectric conversion cell
With the electrode substrate
Opposing substrate facing the electrode substrate and
With the oxide semiconductor layer provided on the electrode substrate or the facing substrate,
An annular sealing portion for joining the electrode substrate and the opposing substrate, and
The electrode substrate, the facing substrate, and the electrolyte filled in the cell space formed by the sealing portion are provided.
The electrolyte contains a redox pair consisting of a halide ion and a polyhalide ion.
The concentration of the polyhalide ion in the electrolyte is 0.05 M or less, and the concentration is 0.05 M or less.
A photoelectric conversion element having an R represented by the following formula (1) of 0.00040 to 0.00200 cm ³ (STP) / (day · mL).

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 oxygen permeability coefficient d in the formula (2) is 46 to 195 cm ³ (STP) · mm / (m ^{2 · day · atm).}

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