JP5225577B2 - Photoelectric conversion element and method for producing counter electrode for photoelectric conversion element - Google Patents

Description

  The present invention relates to a dye-sensitized photoelectric conversion element and a method for producing a counter electrode for the photoelectric conversion element.

  Solar cells as clean energy are attracting attention against the backdrop of environmental issues and resource issues. Among them, dye-sensitized solar cells have been proposed by Swiss Gretzel et al. It attracts attention as a photoelectric conversion element that can obtain high photoelectric conversion efficiency (see Non-Patent Document 1).

FIG. 7 is a cross-sectional view showing an example of a conventional dye-sensitized solar cell.
This dye-sensitized solar cell 100 includes a first substrate 101 on which a porous oxide semiconductor layer 103 carrying a sensitizing dye is formed on one surface, and a second substrate 105 on which a conductive layer 104 is formed. The main constituent element is an electrolyte layer made of, for example, a gel electrolyte enclosed between them. Note that since the porous oxide semiconductor layer 103 is porous, the electrolytic solution (electrolyte) penetrates into (at least a part of) the pores.

As the first substrate 101, a light transmissive plate material is used, and a transparent conductive layer 102 is disposed on the surface of the first substrate 101 in contact with the dye-sensitized semiconductor layer 103 in order to provide conductivity. A working electrode 108 is formed by the one substrate 101, the transparent conductive layer 102, and the porous oxide semiconductor layer 103.
As the second substrate 105, a conductive layer 104 made of, for example, carbon or platinum is provided on the surface in contact with the electrolyte layer 106 to react the electrolyte, and a counter electrode 109 is configured by the second substrate and the conductive layer 104. ing.

The first substrate 101 and the second substrate 105 are arranged at a predetermined interval so that the porous oxide semiconductor layer 103 and the conductive layer 104 face each other, and a sealing portion made of a thermoplastic resin is provided at the peripheral portion between the two substrates. Agent 107 is provided.
Then, the two substrates 101 and 105 are bonded to each other through the sealant 107, and the cells are stacked. Through the electrolyte injection port 110, oxidation / reduction of I ⁻ / I ₃ ⁻ or the like between the electrodes 108 and 109 is performed. An example is one in which an organic electrolyte solution containing a reducing pair is filled to form an electrolyte layer 106 for charge transfer.

As the counter electrode of such a dye-sensitized solar cell, in many cases, a platinum layer formed on a transparent conductive glass substrate is used. However, it cannot be said that the conductivity of the transparent conductive film is sufficiently high. In particular, when a large-area element is produced, it is necessary to compensate for the lack of conductivity, for example, by making the platinum layer significantly thicker.
As for the working electrode, there is an attempt to improve the lack of conductivity by arranging a metal grid for collecting current (for example, Patent Document 1). Moreover, the example which performed the same trial about a counter electrode with a working electrode is known (for example, patent document 2).
In addition, the conventional counter electrode has a very small reaction area of the electrolyte as compared with the working electrode having a roughness factor of 1000 or more.

There is an idea to solve the shortage of conductivity by replacing the counter electrode based on the conventional transparent conductive glass substrate with one based on metal plate and metal foil, but corrosion resistance against iodine electrolyte is required, Applicable materials are limited. An applicable material is titanium, but the current collector terminal cannot be soldered directly. In order to reduce the resistance to a level that can be satisfied only by contact by pressing the current collecting metal, a pressure that is not practical is required. Incomplete terminal bonding increases the contact resistance at the current collecting terminal interface, which hinders improvement in photoelectric conversion efficiency. In particular, the effect cannot be ignored for large elements.
JP 2003-203681 A Special Table 2002-536805 O '' Regan B., Graetzel M., A low cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films, Nature 1991; 353: 737-739

The present invention has been devised in view of such a conventional situation, and provides a photoelectric conversion element that is excellent in photoelectric conversion characteristics by reducing internal resistance while achieving both corrosion resistance and conductivity at the counter electrode. Is the primary purpose.
A second object of the present invention is to provide a method for producing a counter electrode that can easily obtain a counter electrode having different functions on both sides, that is, excellent conductivity and a reaction promoting function. .

The photoelectric conversion element according to claim 1 of the present invention has a porous oxide semiconductor layer carrying a sensitizing dye, and has a working electrode functioning as a window electrode, and at least partly via the electrolyte layer. A photoelectric conversion element comprising a counter electrode disposed opposite to a working electrode, wherein the counter electrode is formed by stacking a metal plate inactive to the electrolyte and a metal layer, the metal plate Is characterized in that one surface thereof is arranged facing the direction of the electrolyte layer, and the other surface is roughened and is in contact with the metal layer.
The photoelectric conversion element according to claim 2 of the present invention is characterized in that, in claim 1, one surface of the metal plate is roughened, and a reaction layer is disposed on the one surface .
According to a third aspect of the present invention, there is provided a counter electrode manufacturing method comprising a porous oxide semiconductor layer carrying a sensitizing dye, a working electrode functioning as a window electrode, and at least partly via an electrolyte layer. A method for producing a counter electrode for a photoelectric conversion element comprising a counter electrode arranged opposite to the working electrode, wherein both surfaces of the counter electrode are roughened simultaneously using a metal plate that is inert to the electrolyte. And a step of forming a metal layer on one roughened surface of the metal plate and a reaction layer on the other surface individually or simultaneously.

In the first photoelectric conversion element according to the present invention, the counter electrode is configured by stacking a metal plate inactive to the electrolyte and a metal layer. As for the said metal plate, the one surface has a part which contact | connects the said electrolyte layer, and the corrosion resistance with respect to electrolyte is ensured. On the other hand, the other surface of the metal plate is roughened and is in contact with the metal layer, so that the current collecting terminal can be soldered to ensure conductivity. Thereby, corrosion resistance and electroconductivity can be made compatible in a counter electrode, an internal resistance can be reduced and the photoelectric conversion element excellent in the photoelectric conversion characteristic can be provided.
Further, in the second photoelectric conversion element according to the present invention, by using the counter electrode as a clad material, in addition to ensuring excellent adhesion in the thickness direction of the counter electrode, as well as corrosion resistance against the electrolyte, It can also have excellent conductivity. Thereby, an internal resistance can be reduced and the photoelectric conversion element excellent in the photoelectric conversion characteristic can be provided.
Moreover, in the manufacturing method of the counter electrode which concerns on this invention, both surfaces can be roughened easily by using a metal plate inactive with respect to electrolyte, and roughening both surfaces simultaneously, and also electroconductivity. And corrosion resistance to the electrolyte can both be achieved. Furthermore, by performing a process of forming a metal layer on one roughened surface of the metal plate and a reaction layer on the other surface individually or simultaneously, the one surface has excellent conductivity due to the metal layer. In addition, the function of the reaction layer can be easily improved on the other surface. Therefore, this method serves to provide a counter electrode having different functions on both sides of the counter electrode, that is, having excellent conductivity and a reaction promoting function.

  Hereinafter, an embodiment of a photoelectric conversion element according to the present invention will be described with reference to the drawings.

<First embodiment>
FIG. 1 is a schematic cross-sectional view showing an embodiment of a photoelectric conversion element according to the present invention.
The photoelectric conversion element 1 is generally configured by a working electrode 14, a counter electrode 20, and an electrolyte layer 15 made of an electrolyte enclosed between them.

The working electrode 14 includes a transparent substrate 11, a transparent conductive film 12 formed on one surface 11a thereof, a porous oxide semiconductor layer 13 formed on one surface of the transparent conductive film 12 and carrying a sensitizing dye. It is composed of Since the porous oxide semiconductor layer 13 is porous, the electrolytic solution (electrolyte) penetrates into (at least a part of) the pores.
The counter electrode 20 is comprised from the metal plate 21 and the metal layer 22 distribute | arranged on the one surface 21a.
In the photoelectric conversion element 1, a laminated body in which the electrolyte layer 15 is sandwiched between the working electrode 14 and the counter electrode 20 is bonded and integrated by the sealing member 16 to function as a photoelectric conversion element.

  In the present invention, the counter electrode 20 is formed by stacking a metal plate 21 and a metal layer 22 that are inactive with respect to the electrolyte. The metal plate 21 has one surface 21b in contact with the electrolyte layer 15; The surface 21 a is roughened and is in contact with the metal layer 22.

In the present invention, the counter electrode 20 is formed by stacking a metal plate 21 and a metal layer 22 that are inert to the electrolyte. Here, the metal inert to the electrolyte means a metal that is hardly chemically corroded, and examples thereof include platinum (Pt), titanium (Ti), nickel (Ni), and the like. Therefore, as the metal plate 21, plate-like Pt, Ti, Ni or the like is used.
Such a metal plate 21 is disposed with its one surface 21 b facing the electrolyte layer 15, thereby ensuring corrosion resistance to the electrolyte. On the other hand, since the other surface 21a of the metal plate 21 is roughened and in contact with the metal layer 22, the current collecting terminal can be soldered and conductivity is ensured. As a result, the counter electrode 20 can be soldered to the current collecting terminal, and has both conductivity and corrosion resistance against the electrolytic solution. The photoelectric conversion element 1 provided with such a counter electrode 20 has reduced internal resistance and can obtain excellent photoelectric conversion characteristics. This effect is particularly effective in a large-area element that is greatly affected by internal resistance.

The type of the metal plate 21 is not particularly limited, but it is possible to select molybdenum (Mo) or the like in addition to the above-described Pt, Ti, Ni as a material that is not easily corroded by the electrolyte in direct contact. Is preferred.
Although details will be described later, a reaction layer 23 as shown in FIG. 3 may be provided on one surface 21 b of the metal plate 21 in contact with the electrolyte layer 15.

The surface of the metal plate 21 is roughened by a physical or chemical etching process. Thereby, the adhesiveness of the metal plate 21 and the said metal layer 22 improves. Further, since the oxide layer on the metal surface is removed during the roughening, the contact resistance can be reduced and the adhesion strength can be improved.
Although the surface roughening method of the metal plate 21 is arbitrary, for example, a physical method such as sand blasting or wet blasting, or a chemical method using various chemicals including acidic and alkaline materials can be used.

  The surface roughness of the metal plate 21 is not particularly limited, but the average surface roughness Ra is preferably 0.13 μm or more. The lower limit of the roughness may be sufficiently larger than that of a commercially available metal that has not been intentionally roughened, but if Ra is too small, the effect of increasing the surface area due to surface roughening is small. Regarding the upper limit, for example, when both surfaces of a metal plate are roughened and a reaction layer with an electrolyte is provided on one side, the effective upper limit of the surface area is naturally determined by the characteristics of the element. For example, in a dye-sensitized photoelectric conversion element, the upper limit of the current that can be generated per unit area is defined by incident light or the absorption wavelength range of the dye, so that the counter electrode 20 can cope with a higher current density. Even if a large surface area is given, it cannot be expected to contribute to power generation. In addition, the metal plate becomes thick and the weight increases. Furthermore, such roughness that the through hole is opened is not preferable.

  The metal layer 22 is provided with another metal layer 22 that can be soldered on the surface of the metal plate 21 so that the titanium metal and the current collecting metal (wiring) can be joined by soldering. The metal layer 22 is preferably made of a material that can be soldered and has higher conductivity than the metal plate 21. In particular, copper, silver, and gold are preferable.

When the metal layer 22 is formed by plating, an expensive vacuum process such as sputtering is not required. Moreover, since the metal layer 22 can be easily thickened, the conductivity of the counter electrode 20 can be made higher than that obtained by sputtering. Since it is easy to ensure the required conductivity, a thinner titanium plate can be used as the metal plate 21.
Further, when the metal layer 22 is formed after the surface roughening of the metal plate 21, the growth of the oxide layer on the titanium surface can be suppressed, and therefore the resistance at the metal plate / metal layer interface can be controlled to be lower.

Further, when the thickness of the metal plate 21 is a, the volume resistivity is α, the thickness of the metal layer 22 is b, and the volume resistivity is β, it is preferable that α> β.
Although not limited, it is preferable that a × (β / α) <b. Thereby, it becomes the metal layer 22 of lower resistance than the metal plate 21, and can ensure the more excellent electroconductivity.

In the counter electrode 20 of the present embodiment, a combination of titanium as the metal plate 21 and copper as the metal layer 22 is preferable. That is,
Corrosion resistance: Titanium ◎, Copper x
Conductivity: Titanium << Copper Soldering: Titanium x, Copper ○
Therefore, according to this combination, the counter electrode 20 having both higher conductivity and corrosion resistance against the electrolytic solution can be obtained.

As described above, a clad material made of copper and titanium can be used instead of a method of forming a copper layer on a titanium plate by a plating method. When a clad material is applied as the electrode material, it is easy to increase the thickness of the copper layer, so that the counter electrode 20 having better conductivity can be obtained. Moreover, if it is a clad material, a board | substrate can be produced at low cost rather than the sputtering method which requires an expensive apparatus.
Although it is possible to form a copper layer (metal layer 22) on the titanium plate (metal plate 21) by sputtering, when a clad material is applied as the metal plate 21, the copper layer can be made thicker. The counter electrode 20 having excellent conductivity can be easily obtained. On the other hand, it is conceivable to form titanium on copper by sputtering, but it is extremely difficult to form a titanium layer that does not include any pinholes and satisfies corrosion resistance.

  The counter electrode 20 of this embodiment can solder a connection terminal, and can achieve both high conductivity and excellent corrosion resistance. The photoelectric conversion element 1 provided with such a counter electrode 20 can obtain excellent photoelectric conversion characteristics in a large-area element greatly influenced by internal resistance.

The working electrode 14 is formed on one surface of the transparent conductive film 12 constituting the transparent conductive substrate 10 and is composed of a porous oxide semiconductor layer 13 carrying a sensitizing dye.
The transparent conductive substrate 10 is generally composed of a transparent base material 11 and a transparent conductive film 12 formed on one surface 11a thereof.

  As the transparent base material 11, a substrate made of a light-transmitting material is used, and any material can be used as long as it is usually used as a transparent base material such as glass, polyethylene terephthalate, polycarbonate, and polyethersulfone. . The transparent substrate 11 is appropriately selected from these. Moreover, as the transparent base material 11, the board | substrate which is excellent in a light transmittance as much as possible is preferable on a use.

The transparent conductive film 12 is a thin film formed on one surface 11a in order to impart conductivity to the transparent substrate 11. In the present invention, the transparent conductive film 12 is preferably a thin film made of a conductive metal oxide in order to obtain a structure that does not significantly impair the transparency of the transparent conductive substrate.
Examples of the conductive metal oxide that forms the transparent conductive film 12 include tin-added indium oxide (ITO), fluorine-added tin oxide (FTO), and the like. The transparent conductive film 12 is particularly preferably a single-layer film made of only FTO or a laminated film in which a film made of FTO is laminated on a film made of ITO.

  By making the transparent conductive film 12 a single-layer film made of only FTO or a laminated film in which a film made of FTO is laminated on a film made of ITO, the amount of light absorbed in the visible region is small, and the conductivity And a transparent conductive substrate having high heat resistance can be formed.

The porous oxide semiconductor layer 13 is provided on the transparent conductive film 12, and a sensitizing dye is supported on the surface thereof. The semiconductor for forming the porous oxide semiconductor layer 13 is not particularly limited, and any semiconductor can be used as long as it is generally used for forming a porous oxide semiconductor for a photoelectric conversion element. As such a semiconductor, for example, titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), or the like can be used. .

  As a method for forming the porous oxide semiconductor layer 13, for example, a dispersion obtained by dispersing commercially available oxide semiconductor fine particles in a desired dispersion medium, or a colloidal solution that can be prepared by a sol-gel method is used as necessary. After adding a desired additive, after forming a coating film by a known coating method such as a screen printing method, an ink jet printing method, a roll coating method, a doctor blade method, a spray coating method, etc. Can be applied.

  As the sensitizing dye, a ruthenium complex containing a bipyridine structure, a terpyridine structure or the like as a ligand, a metal-containing complex such as porphyrin or phthalocyanine, or an organic dye such as a derivative such as eosin, rhodamine or merocyanine can be applied. Among them, those exhibiting behaviors suitable for applications and semiconductors used can be selected without particular limitation.

  The electrolyte layer 15 is formed by impregnating an electrolyte solution between both electrodes including the porous oxide semiconductor layer 13, or the electrolyte solution is gelled (pseudo-solidified) using an appropriate gelling agent. Things are used.

  As the electrolytic solution, an organic solvent containing a redox species, a room temperature molten salt (ionic liquid), or the like can be used. In addition, the electrolyte is made solid by introducing an appropriate gelling agent (polymer gelling agent, low molecular gelling agent, various nanoparticles, carbon nanotubes, etc.), so-called gel electrolyte is used. It doesn't matter. There are no particular limitations on the solvent, but organic solvents such as acetonitrile, methoxyacetonitrile, propionitrile, propylene carbonate, ethylene carbonate, diethyl carbonate, γ-butyrolactone, imidazolium cations, pyrrolidinium cations, pyridinium cations, etc. A room temperature molten salt comprising a cation having a quaternized nitrogen atom and the like, an iodide ion, a bistrifluoromethanesulfonylimide anion, a dicyanoamide anion, a thiocyanate anion, or the like can be selected. The redox species is not particularly limited, but one formed by adding iodine / iodide ions, bromine / bromide ions, etc. can be selected. For example, in the former case, an iodide salt (lithium salt, quaternary salt) is selected. Graded imidazolium salt derivatives, tetraalkylammonium salts and the like may be used alone or in combination.) And iodine may be added alone or in combination. In addition, various additives such as 4-tert-butylpyridine, N-methylbenzimidazole, guanidinium salt derivatives may be added to the electrolytic solution as necessary.

  The sealing member 16 is not particularly limited as long as it has excellent adhesion to the counter electrode 20, and examples thereof include High Milan (manufactured by Mitsui DuPont Polychemical Co.) and Binnel (manufactured by DuPont).

  Since such a photoelectric conversion element 1 includes the counter electrode 20 capable of soldering the connection terminals and having both high conductivity and excellent corrosion resistance, the internal resistance is reduced and excellent photoelectric conversion characteristics are obtained. Can do. This effect is particularly effective in a large-area element that is greatly affected by internal resistance.

  FIG. 2 is a schematic cross-sectional view showing a modification of the photoelectric conversion element of FIG. 1 described above. In the photoelectric conversion element of FIG. 1, the sealing member 16 is sandwiched between the counter electrode 20 and the working electrode 14, whereas in the photoelectric conversion element of FIG. 2, the metal plate 21 constituting the counter electrode 20 is the working electrode 14. The sealing member 16 has a smaller area than that of the transparent base material 11 and the sealing member 16 is disposed so as to cover at least the side surfaces of the electrolyte layer 15 and the metal plate 21. The sealing member 16 shown in FIG. 2 is further disposed on the surface of the counter electrode 20 opposite to the working electrode 14 so as to cover the outer edge portion.

  According to the configuration of FIG. 2, since the sealing member 16 is disposed so as to cover at least the side surfaces of the counter electrode 20 having a smaller area than the working electrode 14 and the electrolyte layer 15, sealing is performed. While the choice of a stop member and a sealing method increases, the restriction | limiting of the distance between electrodes by a sealing member is also avoided, and the photoelectric conversion element which has the outstanding power generation characteristic can be provided.

<Second embodiment>
FIG. 3 is a schematic cross-sectional view showing the photoelectric conversion element according to this embodiment. In the following description, parts different from those of the first embodiment described above will be mainly described, and description of parts similar to those of the first embodiment will be omitted.
In the present embodiment, the counter electrode 20 is characterized in that one surface 21b of the metal plate 21 is roughened, and a reaction layer 23 with an electrolyte is disposed on the one surface 21b.

  The reaction layer 23 may be any material as long as the redox species in the electrolyte can smoothly cause a redox reaction on the surface of the reaction layer, and particularly preferably at least one of platinum, carbon, and a conductive polymer. Selected from materials containing The platinum layer can be formed by a technique such as vapor deposition, sputtering, printing, or heat treatment of chloroplatinate.

  The carbon layer can be formed by a technique such as vapor deposition, sputtering, or application of carbon powder. As the carbon material, graphitized carbon, amorphous carbon, carbon black, activated carbon, carbon nanotubes, fullerenes and the like can be used without particular limitation. The conductive polymer layer can be formed by techniques such as electrolytic polymerization, dispersion or solution coating. As the conductive polymer, for example, a polythiophene derivative such as poly (3,4-ethylenedioxythiophene: PEDOT) or a derivative such as polypyrrole or polyaniline can be used, and is not particularly limited.

  In particular, by roughening the reaction layer forming surface of the metal plate 21, the surface area of the reaction layer 21 is increased, the reaction area with the electrolyte is increased, and the reaction with the electrolyte when the photoelectric conversion element functions is more smoothly performed. Can proceed. Thereby, the photoelectric conversion element provided with the counter electrode 20 of this embodiment becomes more preferable in terms of photoelectric conversion efficiency.

Next, a method for manufacturing such a counter electrode 20 will be described.
The method for producing a counter electrode of the present invention comprises a step of simultaneously roughening both surfaces of a metal plate that is inert to the electrolyte, a metal layer on one roughened surface 21a of the metal plate, And a step of individually or simultaneously forming reaction layers on the surface 21b.
By using a metal plate that is inert to the electrolyte and simultaneously roughening both surfaces, both surfaces can be easily roughened, and both conductivity and corrosion resistance to the electrolyte can be achieved. Furthermore, by performing a process of forming a metal layer on one roughened surface of the metal plate and a reaction layer on the other surface individually or simultaneously, the one surface has excellent conductivity due to the metal layer. In addition, it is possible to easily impart a reaction promoting function by the reaction layer to the other surface. Therefore, this method serves to provide a counter electrode having different functions on both sides of the counter electrode, that is, having excellent conductivity and a reaction promoting function.

  The method for roughening the surface of the metal plate is not particularly limited. For example, physical methods such as sand blasting and wet blasting, and chemical methods using various chemical solutions including acidic and alkaline materials can be used.

Although the formation method of the metal layer 22 is not specifically limited, It is preferable to form by metal plating. According to the plating, an expensive vacuum process such as a sputtering method is not required. Moreover, since the metal layer 22 can be easily thickened, the conductivity of the counter electrode 20 can be made higher than that obtained by sputtering.
Further, when the metal layer 22 is formed after the surface roughening of the metal plate 21, the growth of the oxide layer on the surface of the metal plate can be suppressed, so that the resistance of the metal plate / metal layer interface can be controlled lower.

  Although the formation method of the reaction layer 23 is not specifically limited, If the reaction layer 23 is a platinum layer, it can form by methods, such as a vapor deposition method, a sputtering method, a printing method, and the heat processing of a chloroplatinate. If the reaction layer 23 is a carbon layer, it can be formed by a technique such as vapor deposition, sputtering, or application of carbon powder. If the reaction layer 23 is a conductive polymer layer, it can be formed by techniques such as electrolytic polymerization, dispersion or solution coating.

  The counter electrode 20 obtained as described above can be soldered to the connection terminal, and can achieve both high conductivity and excellent corrosion resistance. The photoelectric conversion element 1 provided with such a counter electrode 20 has reduced internal resistance and can obtain excellent photoelectric conversion characteristics.

  FIG. 4 is a schematic cross-sectional view showing a modification of the photoelectric conversion element of FIG. 3 described above. In the photoelectric conversion element of FIG. 3, the sealing member 16 is sandwiched between the counter electrode 20 and the working electrode 14, whereas in the photoelectric conversion element of FIG. 4, the metal plate 21 constituting the counter electrode 20 is the working electrode 14. The sealing member 16 has a smaller area than that of the transparent base material 11 and the sealing member 16 is disposed so as to cover at least the side surfaces of the electrolyte layer 15 and the metal plate 21. The sealing member 16 shown in FIG. 4 is further arranged on the surface of the counter electrode 20 opposite to the working electrode 14 so as to cover the outer edge portion.

  According to the configuration of FIG. 4, since the sealing member 16 is disposed so as to cover at least the side surfaces of the counter electrode 20 having a smaller area than the working electrode 14 and the electrolyte layer 15, sealing is performed. While the choice of a stop member and a sealing method increases, the restriction | limiting of the distance between electrodes by a sealing member is also avoided, and the photoelectric conversion element which has the outstanding power generation characteristic can be provided.

<Third embodiment>
FIG. 5 is a schematic cross-sectional view showing the photoelectric conversion element according to this embodiment. In the following description, parts different from those of the first embodiment described above will be mainly described, and description of parts similar to those of the first embodiment will be omitted.

In the present embodiment, the counter electrode 20C (20) is characterized by using a clad material in which portions 20Ca and 20Cb made of different members in the thickness direction are overlaid.
Here, the clad material means a material in which different kinds of metals are bonded together by rolling. By using the clad material as the counter electrode, in addition to ensuring excellent adhesion in the thickness direction of the counter electrode, it is possible to have excellent conductivity as an electrode as well as corrosion resistance to the electrolyte.

In the present embodiment, the counter electrode 20 has a two-layer structure in which a first portion 20Ca made of a metal inert to the electrolyte and a second portion 20Cb made of a solderable metal are arranged in an overlapping manner, The first portion 20Ca side is arranged so as to be in contact with the electrolyte layer 15. Thereby, since the counter electrode 20 has the 2nd site | part 20Cb, while being able to solder a current collection terminal, electroconductivity and corrosion resistance with respect to electrolyte solution are ensured simultaneously by presence of the 1st site | part 20Ca.
The photoelectric conversion element 1 provided with such a counter electrode 20 has reduced internal resistance and can obtain excellent photoelectric conversion characteristics. This effect is particularly effective in a large-area element that is greatly affected by internal resistance.

However, the counter electrode of the present invention is not limited to the above example. For example, a structure having three or more layers may be used, and the arrangement method is not limited to the above example.
Moreover, you may take the structure by which the reaction layer (not shown) with an electrolyte was distribute | arranged on one surface 21b of 1st site | part 20Ca which comprises a metal plate. Furthermore, similarly to the second embodiment described above, the one surface 21b of the first portion 20Ca constituting the metal plate may be roughened.

Whether the target counter electrode is a clad material can be confirmed from the following points.
Sputter-formed layers generally have different thicknesses: Sputter-formed layers are at most several hundred nm to several μm thick, whereas a clad material is a combination of foils having thicknesses of several μm to several tens μm or more. Become. In addition, although it is not impossible to form a thick film even by a plating method or the like, the state of the metal structure is also different in that case.

  In the case of the clad material as it is bonded: (Because it generally includes a rolling process at the time of production), it becomes long crystal grains having a uniform crystal orientation in the longitudinal direction of the metal foil (the rolling operation direction). This can be confirmed not only by directly observing the metal structure but also by the appearance of a sharp peak by X-ray diffraction. In particular, when the target is a copper layer, a sharp peak derived from the (111) plane appears.

  In the case of a clad material that has been annealed: If the object is a metal with a low recrystallization temperature, such as copper, silver, or gold, the crystal grains are very large with the same orientation as described above.

A plated layer or the like to which rolling has been applied can also be assumed, but in that case, it can also be determined as follows. In the case of the clad material, since it is bonded together while rolling, it has a structure in which the newly exposed surfaces are joined together while the oxide layer present in the surface layer is involved. That is, a metal bond is formed on the bonding surface in a state where the oxide layer is taken into an island shape. This structure can be confirmed by a transmission electron microscope (TEM) or the like. On the other hand, in a metal layer formed by a plating method or the like, the bonding interface exists in a state through an oxide layer.
By finding one of the above states, it is possible to determine whether the target counter electrode is a clad material or other methods.

  FIG. 6 is a schematic cross-sectional view showing a modification of the photoelectric conversion element of FIG. 5 described above. In the photoelectric conversion element of FIG. 5, the sealing member 16 is sandwiched between the counter electrode 20 and the working electrode 14, whereas in the photoelectric conversion element of FIG. 6, the metal plate 21 constituting the counter electrode 20 is the working electrode 14. The sealing member 16 has a smaller area than that of the transparent base material 11 and the sealing member 16 is disposed so as to cover at least the side surfaces of the electrolyte layer 15 and the metal plate 21. The sealing member 16 shown in FIG. 6 is further disposed on the surface of the counter electrode 20 opposite to the working electrode 14 so as to cover the outer edge portion.

  According to the configuration of FIG. 6, since the sealing member 16 is disposed so as to cover at least the side surfaces of the counter electrode 20 having a smaller area than the working electrode 14 and the electrolyte layer 15, sealing is performed. While the choice of a stop member and a sealing method increases, the restriction | limiting of the distance between electrodes by a sealing member is also avoided, and the photoelectric conversion element which has the outstanding power generation characteristic can be provided.

  The photoelectric conversion element of the present invention has been described above, but the present invention is not limited to the above example, and can be appropriately changed as necessary.

(First experiment example)
In order to investigate the effect of the electrode substrate according to the present invention, the following cladding materials were prepared, and the performance as a counter electrode of the dye-sensitized solar cell was evaluated.
In the counter electrodes T1 to T6, a metal plate having a material and thickness as shown in Table 1 is bonded to one surface of a metal plate (dimension 130 mm × 400 mm) having a material and thickness as shown in Table 1. Was used. A platinum layer was formed on the other surface of the metal plate by sputtering to produce a counter electrode.
For the counter electrodes T7 to T9, a pure titanium plate and a glass substrate with an FTO film were prepared for comparison, and a platinum layer was similarly formed on the surface to prepare a counter electrode.

In order to evaluate the characteristics of the prepared counter electrode, evaluation elements (Sample 1 to Sample 11) were manufactured in the following manner.
A silver circuit was formed in a lattice shape (and peripheral portion) by screen printing on a glass substrate (140 mm × 410 mm) having an FTO / ITO layer formed on the surface by spray pyrolysis (circuit width 300 μm, film thickness 5 μm). A silver paste for printing having a volume resistivity of 3 × 10 ⁻⁶ Ω · cm after sintering was used. Further, a low melting point glass paste was printed by screen printing so as to have a width of 600 μm so as to completely cover the silver circuit, and this was fired to form a shielding layer. Further, a paste containing TiO ₂ nanoparticles was applied on the substrate by screen printing, dried, and then fired at 500 ° C. for 60 minutes to form an oxide semiconductor porous film. This was immersed in a t-butanol / acetonitrile (1: 1) solution of a ruthenium bipyridine complex (N719 dye) for 24 hours or longer to support the dye to obtain a working electrode.

The electrolyte used was a mixture of 1-hexyl-3-methylimidazolium iodide and iodine mixed at a molar ratio of 10: 1 to LiI and 4-tert-butylpyridine. In addition, a solidified body obtained by adding SiO ₂ nanoparticles to this electrolytic solution (referred to as gel electrolyte) was also applied.
A liquid electrolyte or a gel electrolyte was applied to the working electrode described above, the prepared counter substrate was bonded (with the Pt surface inside), and the peripheral portion was sealed with an ultraviolet curable resin.

For the working electrode, lead wires were attached to several locations on the outer peripheral silver layer by soldering, and for the counter electrode (titanium substrate), lead wires were attached to several locations on the copper layer by soldering, and the characteristics were evaluated.
In the comparative counter electrode of the counter electrodes T7 to T9, since the pure titanium plate counter electrode in which the metal layer was not formed cannot be soldered, the lead wire for the terminal was taped and evaluated. As for the counter electrode of the glass substrate type, the terminal was attached from the FTO surface in the same manner as the working electrode by pasting the counter electrode and the working electrode slightly shifted.

The photoelectric conversion characteristics of the fabricated devices were evaluated under simulated solar irradiation with AM 1.5 and 100 mW / cm ² . The results are shown in Table 2. Here, the measurement was performed by collecting a plurality of lead wires and connecting a measurement terminal to the tip.

  As is apparent from Table 2, each sample (S1 to S8) of the example showed good photoelectric conversion characteristics, whereas each sample (S9, S10) of the comparative example had a significantly low output. In the sample (S9) in which the copper layer is not formed, the resistance at the counter electrode base material / lead wire interface is large, and in the sample (S10) using the glass substrate as the counter electrode, the conductivity of the transparent conductive film is insufficient. For this reason, it is considered that the cause is that they are greatly affected by the IR drop.

  As is apparent from the above, the use of the counter electrode of the present invention can reduce the resistance of the connection with the current collector (for example, lead wire) connected to the external circuit and the resistance of the counter electrode itself. When used for a solar cell, it can be seen that an excellent output can be obtained as compared with an element using a counter electrode to which such measures are not applied.

(Second experiment example)
A titanium plate (t40 μm, 300 μm) having a size of approximately 130 mm × 400 mm was prepared as a metal plate for the counter electrode.
One side of the titanium plate was roughened by hydrofluoric acid treatment or wet blasting so that the average surface roughness Ra was about 0.5 μm, 1 μm, and 10 μm.
Subsequently, a copper layer was provided on one roughened surface by electrolytic plating, and a platinum layer was formed on the other roughened surface to produce a counter electrode (T10 to T16).

For comparison, a copper layer was similarly provided by electrolytic plating on a titanium plate not subjected to roughening treatment (counter electrodes T17 to T19), but the adhesion was extremely low, and the operation was such that the surface was traced with an adhesive tape. Since the plating layer was easily peeled off, it could not be applied to the counter electrode of the dye-sensitized solar cell. Such peeling was not observed on the roughened substrate.
Further, for comparison, a titanium plate (counter electrode T20) in which a copper layer was not formed and a platinum plate (counter electrode T21) formed in the same manner on an FTO / ITO glass substrate were also produced.

In order to evaluate the characteristics of the produced counter electrode, evaluation elements (samples S12 to S24) were produced in the same manner as in the first experimental example.
The photoelectric conversion characteristics of the fabricated elements were evaluated in the same manner as in the first experimental example. The results are shown in Table 4.

  As is clear from Table 4, the examples (samples S12 to S20) showed good photoelectric conversion characteristics, whereas the comparative examples (samples S21 to S24) had a significantly low output. In the system in which the metal layer is not formed (samples S21 and S22), the resistance at the counter electrode base material / lead wire interface is large, and in the system using the glass substrate as the counter electrode (samples S23 and S24), the conductivity of the transparent conductive film This is considered to be caused by the large influence of IR drop due to the insufficiency.

  As can be seen from the above, the use of the counter electrode of the present invention can reduce the resistance of the connection with the current collector (for example, lead wire) connected to the external circuit and the resistance of the counter electrode substrate itself. It was found that when used as a counter electrode of a solar cell, an excellent output can be obtained as compared with an element using a counter electrode material that has not been subjected to such measures.

(Third experimental example)
A titanium plate (t40 μm, 300 μm) having a size of about 130 mm × 400 mm was prepared as a counter electrode base material.
Both surfaces of the titanium plate were roughened by hydrofluoric acid treatment or wet blasting so that the average surface roughness Ra was about 0.5 μm, 1 μm, and 10 μm.
A copper layer is provided by electrolytic plating on one of the roughened (or untreated) substrates, and a platinum layer or a PEDOT layer is formed on the other surface to form a counter electrode (T22- T29). The platinum layer was obtained by sputtering, and the PEDOT layer was obtained by dipping the substrate in an aqueous dispersion. For comparison, a platinum layer (counter electrode T30) formed on an ITO glass substrate in the same manner was also produced.

In order to evaluate the characteristics of the produced counter electrode, evaluation elements (samples S25 to S38) were produced in the same manner as in the first experimental example.
The photoelectric conversion characteristics of the fabricated elements were evaluated in the same manner as in the first experimental example. The results are shown in Table 6.

  As is clear from Table 6, in samples S25 to S33, the surface of the metal plate is roughened to increase the effective area, thereby using an untreated product and an ITO glass substrate that is inferior in conductivity (sample S34). ~ S38) Any of the higher outputs could be obtained.

  As is clear from the above, when the counter electrode according to the present invention is used, it is possible to easily ensure higher conductivity than that using a conventional glass substrate, and the effective area of the counter electrode is reduced by roughening the surface. It is possible to increase the output, and an output superior to that using an untreated metal plate can be obtained.

  The present invention is applicable to a dye-sensitized photoelectric conversion element and a method for manufacturing a counter electrode for the photoelectric conversion element. The photoelectric conversion element of the present invention is suitably used as a dye-sensitized solar cell.

It is a schematic sectional drawing which shows an example of the photoelectric conversion element which concerns on this invention. It is a schematic sectional drawing which shows the modification of the photoelectric conversion element of FIG. It is a schematic sectional drawing which shows another example of the photoelectric conversion element which concerns on this invention. It is a schematic sectional drawing which shows the modification of the photoelectric conversion element of FIG. It is a schematic sectional drawing which shows another example of the photoelectric conversion element which concerns on this invention. It is a schematic sectional drawing which shows the modification of the photoelectric conversion element of FIG. It is a schematic sectional drawing which shows an example of the conventional photoelectric conversion element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Photoelectric conversion element, 10 Transparent conductive substrate, 11 Transparent base material, 12 Transparent conductive film, 13 Porous oxide semiconductor layer, 14 Working electrode (window electrode), 15 Electrolyte layer, 16 Sealing member, 20 Counter electrode, 21 Metal plate, 22 metal layer, 23 reaction layer.

Claims (3)

It has a porous oxide semiconductor layer carrying a sensitizing dye, and has a working electrode that functions as a window electrode, and a counter electrode that is disposed at least partially facing the working electrode through an electrolyte layer. A photoelectric conversion element comprising:
The counter electrode is formed by stacking a metal plate that is inert to the electrolyte and a metal layer, and the metal plate is disposed so that one surface thereof faces the direction of the electrolyte layer and the other surface is rough. A photoelectric conversion element characterized by being planarized and in contact with the metal layer.  The photoelectric conversion element according to claim 1, wherein one surface of the metal plate is roughened, and a reaction layer is disposed on the one surface. It has a porous oxide semiconductor layer carrying a sensitizing dye, and has a working electrode that functions as a window electrode, and a counter electrode that is disposed at least partially facing the working electrode through an electrolyte layer. A method of manufacturing a counter electrode for a photoelectric conversion element,
Using a metal plate inert to the electrolyte, and simultaneously roughening both surfaces thereof;
Forming a metal layer on one of the roughened surfaces of the metal plate and forming a reaction layer on the other surface individually or simultaneously.

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