JP4932196B2 - Electrode and photoelectric conversion element - Google Patents

Description

The present invention, as a counter electrode used in the photoelectric conversion element such as a dye-sensitized solar cell, a photoelectric conversion device having an electrode及beauty before Symbol electrodes constructed from porous carbon member.

  Dye-sensitized solar cells were developed by Gretzell et al. In Switzerland, and have the advantages of high photoelectric conversion efficiency and low manufacturing costs, and are attracting attention as new types of solar cells (for example, patents) Documents 1 and 2 and Non-Patent Document 1).

  As a schematic structure of the dye-sensitized solar cell, it has a porous film made of oxide semiconductor fine particles (nanoparticles) such as titanium dioxide on a transparent conductive electrode substrate and carrying a photosensitizing dye. A working electrode and a counter electrode provided opposite to the working electrode are provided, and an electrolyte containing a redox pair is filled between the working electrode and the counter electrode. In this type of dye-sensitized solar cell, the oxide semiconductor fine particles are sensitized by a photosensitizing dye that absorbs incident light such as sunlight, and an electromotive force is generated between the working electrode and the counter electrode. It functions as a photoelectric conversion element that converts energy into electric power.

As the electrolyte, it is common to use an electrolytic solution obtained by dissolving a redox pair such as I ⁻ / I ₃ ^{— in} an organic solvent such as acetonitrile. In addition, a configuration using a non-volatile ionic liquid, There are known a configuration in which a liquid electrolyte is gelled with an appropriate gelling agent to make it pseudo-solid, a configuration using a solid semiconductor such as a p-type semiconductor, and the like.
The ionic liquid is also called a room temperature melting salt, and is a salt composed only of positive and negatively charged ions existing as a stable liquid in a wide temperature range including around room temperature. Since this ionic liquid has substantially no vapor pressure and is free from concerns such as volatilization and ignition like a general organic solvent, it is expected as a means for solving cell characteristic deterioration due to volatilization.

For the counter electrode, an electrode having a platinum film formed by vapor deposition or sputtering on a transparent conductive electrode substrate or metal plate is mainly used.
However, platinum is expensive, and depending on the electrolyte, platinum may be dissolved, leading to deterioration of power generation characteristics. For this reason, by using a counter electrode using chemically stable carbon, a dye-sensitized solar cell excellent in long-term stability has been developed (see, for example, Patent Documents 3 to 6).
However, when such a carbon counter electrode is used, there is a drawback that power generation characteristics are deteriorated as compared with a counter electrode having platinum.
Japanese Patent No. 2664194 JP 2001-160427 A JP 2003-142168 A Japanese Patent Laid-Open No. 2004-111216 Japanese Patent Laid-Open No. 2004-127849 JP 2004-152747 A M. Graetzel et al., Nature (UK), 1991, No. 737, p. 353

  The present invention has been made in view of the above circumstances, and provides an electrode suitable as a counter electrode that provides a photoelectric conversion element having high power generation efficiency and excellent long-term stability, a method for manufacturing the electrode, and a photoelectric conversion element using the electrode. The purpose is to do.

An electrode according to claim 1 of the present invention is an electrode that forms a counter electrode that is disposed with at least a part of an electrolyte layer with respect to a working electrode, and the counter electrode is at least porous on the side in contact with the electrolyte layer It is comprised from a carbon member, The space | gap which exists in the said porous carbon member is large, so that it approaches the said electrolyte layer in the thickness direction, It is characterized by the above-mentioned.
The electrode according to claim 2 of the present invention is characterized in that, in claim 1, the porous carbon member has a multilayer structure .
The photoelectric conversion element according to claim 3 of the present invention is a working electrode having a porous oxide semiconductor layer having a sensitizing dye supported on the surface thereof, facing the porous oxide semiconductor layer side of the working electrode. A counter electrode, and a photoelectric conversion element comprising at least an electrolyte layer in at least a part between the two electrodes, wherein the counter electrode is composed of at least a porous carbon member on the side in contact with the electrolyte layer, The voids inherent in the porous carbon member are characterized by being larger in the thickness direction as they approach the electrolyte layer.

Since the electrode according to the present invention is composed of at least a porous carbon member on the side in contact with the electrolyte layer, and the voids in the porous carbon member are larger in the thickness direction as it approaches the electrolyte layer, The electrolyte easily penetrates into the porous carbon member from the side of the electrolyte layer having a large void, and the electrode reaction proceeds smoothly. Moreover, since a space | gap is so small that it leaves | separates from an electrolyte layer, it can also suppress that the solution which passes a porous carbon member and makes an electrolyte layer leaks. Therefore, according to the present invention, it is possible to obtain an electrode suitable as a counter electrode for a photoelectric conversion element, which can improve the power generation efficiency as compared with the conventional carbon electrode and can maintain power generation characteristics excellent in long-term stability.
In the electrode manufacturing method according to the present invention, at least a step of applying a carbon paste to one surface of a substrate to form a carbon member, and a step of heat-treating the carbon member to form a porous carbon member are provided. By providing the porous carbon member, the voids in the porous carbon member are large in the thickness direction so as to approach the electrolyte layer, and the electrode that improves the power generation efficiency can be easily manufactured as a counter electrode.
Furthermore, since the photoelectric conversion element using the electrode according to the present invention includes the above electrode as a counter electrode, it is possible to provide a photoelectric conversion element having excellent long-term stability and high power generation efficiency.

The present invention will be described below.
The present invention is an electrode forming a counter electrode disposed at least partially with respect to the working electrode, wherein the counter electrode is composed of at least a porous carbon member on the side in contact with the electrolyte layer, The voids present in the porous carbon member are characterized by being larger in the thickness direction as they approach the electrolyte layer.
That is, if there are many voids in the porous carbon member, the electrolyte easily infiltrates into the porous carbon member, and the area where the electrolyte and the electrode are in contact with each other increases. Power generation efficiency can be obtained. However, when the voids in the porous carbon member are increased, the mechanical strength of the porous carbon member is reduced, so that the porous carbon member is fragile, and when the porous carbon member is formed on the substrate, the adhesion with the substrate is also reduced. Therefore, it will be easily peeled off. Therefore, in the porous carbon member of the present invention, the internal voids have a dense region and a sparse region, and the closer to the electrolyte layer, the larger the void becomes a sparse region, which modulates in the thickness direction. In addition, as a photoelectric conversion element, for example, a dye-sensitized solar cell is assembled. Thereby, the photoelectric conversion element from which the outstanding conversion efficiency is obtained can be manufactured.

  In addition, the porous carbon member may be a film or a substrate, and when the porous carbon member is formed on the substrate as a film, the surface on the region side where the voids are dense is in contact with the substrate, and the surface on the region side where the voids are sparse is the electrolyte and A photoelectric conversion element shall be comprised by forming a porous carbon member (film | membrane) on a base material so that it may contact | connect. As a result, it is possible to obtain excellent conversion efficiency, as well as maintaining the mechanical strength of the porous carbon member and improving the adhesion with the substrate on which the porous carbon electrode is provided. Can be manufactured.

Next, a case where a porous carbon member is used as a film will be described as an embodiment of the electrode of the present invention. FIG. 1 is a schematic cross-sectional view showing the structure of a photoelectric conversion element using the electrode of the present invention.
As shown in FIG. 1, the photoelectric conversion element 1 of the present invention has a window on the side where light enters a transparent substrate having a three-layer structure including a first base material 2, a transparent conductive film 4, and a porous oxide semiconductor layer 5. The electrode 8 is the working electrode, while the electrode composed of the second base material 3 and the porous carbon member 7 is the counter electrode 9, and the electrolyte (electrolyte or electrolyte gel) 6 is sandwiched between the window electrode 8 and the counter electrode 9. It is what.

The first base material 2 is not particularly limited as long as it is a transparent member having electrical conductivity that conducts electricity by forming a film (layer) made of a conductive material on the surface and having high light transmittance. As the first base material 2, a glass plate is generally used, but other than the glass plate, for example, plastics such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polycarbonate (PC). A ceramic polishing plate such as a sheet, titanium oxide, or alumina can be used. Here, the surface refers to the surface of the base material surface that forms the transparent conductive film 4 and the like and is disposed to face the porous carbon member 7 that acts as the counter electrode 9.
In addition, the first base material 2 is a conductive material that can withstand high heat of about 500 ° C. when titanium dioxide (TiO ₂ ) is baked on the substrate on which a transparent conductive film is formed later as the porous oxide semiconductor 5 for supporting the dye. Heat resistant glass is desirable.

The transparent conductive layer 4 is a conductive film having a high light transmittance made of a conductive material formed on the first substrate 2. As the transparent conductive layer 4, for example, a transparent oxide semiconductor such as tin-added indium oxide (ITO), tin oxide (SnO ₂ ), or fluorine-added tin (FTO) is used alone or in combination of a plurality of types. However, it is not particularly limited, and a material that meets the purpose of use in terms of light transmittance and conductivity may be selected. Further, in order to provide a conductive assist (collecting current) effect, a metal wiring or the like may be added within a range that does not significantly impair the light transmittance.
And it is set as the window electrode board | substrate by forming the transparent conductive layer 4 on the 1st base material 2. FIG.

Although there are no particular limitations on the material and formation method of the porous oxide semiconductor layer 5, for example, titanium dioxide (TiO ₂ ), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ). , Zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), etc., alone or in combination of two or more, is a porous thin film mainly composed of oxide semiconductor particles. It can be obtained from a colloidal solution obtained by the gel method.
As a method for forming a porous film, for example, colloidal solutions and dispersions (including additives as necessary), various coating methods such as screen printing, inkjet printing, roll coating, doctor blade, spin coating, spray coating, etc. In addition to coating by coating, electrophoretic electrodeposition of fine particles, combined use of a foaming agent, etc. may be used. The porous oxide semiconductor layer 5 carries a sensitizing dye.

  As the sensitizing dye, for example, a ruthenium complex containing a bipyridine structure, a terpyridine structure or the like as a ligand, a metal-containing complex such as porphyrin, phthalocyanine, or an organic dye such as erosine, rhodamine, or merocyanine can be used. An appropriate material can be selected without particular limitation depending on the use and the porous semiconductor membrane to be used.

  Further, the second base material 3 is a substrate on which the porous carbon member 7 used for the counter electrode 9 is provided. Like the first base material 2, it is common to use a transparent glass plate. However, in addition to the transparent glass plate, for example, it is possible to use an inexpensive titanium (Ti) plate or carbon plate that has better electrical conductivity than the transparent conductive glass, can be freely designed in thickness, and is inexpensive.

The porous carbon member 7 is formed by, for example, forming a carbon film by applying or printing a carbon paste containing a solvent on the second substrate 3 and evaporating the solvent contained by heating the carbon film. A void is formed in the carbonaceous material 7. The voids formed in the porous carbon member 7 have a modulated porosity in the thickness direction.
Specifically, as shown in FIG. 2, the porous carbon member 7 has a region 7 </ b> A in which the voids are dense and a region 7 </ b> B in which the voids are sparse, and the region 7 </ b> A where the voids are dense is far from the electrolyte 6. The region 7 </ b> B, which is in the region and has a small gap, is arranged in the vicinity of the electrolyte 6. Thereby, the counter electrode 9 provided with the electrode using the porous carbon member 7 whose porosity is modulated in the thickness direction is formed on one surface of the second base material 3.

Such a porous carbon member in which the void ratio is modulated in the thickness direction may be configured to evaporate the solvent by adjusting the heat treatment temperature of the carbon film containing the solvent, for example. After stacking carbon films with different contents, heat treatment is repeated each time the carbon film is heated at once to evaporate the solvent or form a carbon film with different solvent contents. The solvent may be evaporated to form a multilayer structure.
When the porous carbon member is integrally formed by subjecting the carbon film to heat treatment, the number of manufacturing process steps is reduced and the porous carbon member can be efficiently performed. Further, if the heat treatment is performed every time the carbon film is formed, the gas (solvent) component can be efficiently removed. When the porous carbon member is formed in a multilayer structure, the size of the gap can be easily changed in the thickness direction, and a free design according to the purpose can be made.

  In particular, the size of the voids present in the porous carbon member 7 is, for example, in a distant region from the electrolyte 6 layer, that is, in the region 7A where the voids are dense, in consideration of adhesion to the second substrate 3 and power generation efficiency. 20 nm or less (0 to 20 nm), on the other hand, it is good to set it as 50 nm-10 micrometers in the area | region 7B vicinity of the electrolyte 6 layer, ie, area | region 7B where a space | gap is sparse. That is, if the region 7A exceeds 20 nm, there is a possibility that sufficient adhesion to the second base material 3 cannot be obtained. On the other hand, if the region 7B is less than 50 nm, more sufficient power generation efficiency can be obtained. There is a possibility that it cannot be done.

Moreover, the electrolyte solution 6 refers to an aqueous solution having electrical conductivity in which the electrolyte is dissociated in the solution to generate cations and anions. As the electrolytic solution 6, for example, an organic solvent containing a redox pair, an ionic liquid (room temperature molten salt), or the like can be used.
The oxidation-reduction pair is not particularly limited. For example, iodine / iodide ion, bromine / bromide ion, etc. can be selected. In the former case, iodide salt (lithium salt, quaternized imidazolium salt, tetra Butylammonium salt and the like can be used alone or in combination, and iodine can be added alone or in combination.
Examples of the organic solvent include volatile electrolytes using acetonitrile, methoxyacetonitrile, propionitrile, ethylene carbonate, propylene carbonate, diethyl carbonate, γ-butyrolactone, and the like.
In addition, as the ionic liquid, for example, a room temperature meltability of a liquid at room temperature using a compound having a quaternized nitrogen atom such as a quaternized imidazolium derivative, a quaternized pyridinium derivative, or a quaternized ammonium derivative as a cation. There is salt. By using an ionic liquid as the electrolyte, safety and durability can be improved.

In addition, a so-called gel electrolyte obtained by quasi-solidifying such an electrolytic solution by suppressing the fluidity by introducing an appropriate gelling agent and filler may be used.
Various additives such as lithium salt and tert-butylpyridine may be further added to the electrolytic solution 6 as necessary. Further, a polymer solid electrolyte having a charge transporting ability as in the case of such an electrolytic solution may be used.

  Thus, according to this embodiment, even when a carbon counter electrode is used, the porosity of the voids present in the porous carbon member is configured to be greatly modulated on the electrolyte layer side in the thickness direction. This makes it possible to obtain excellent conversion efficiency. Moreover, since the porous carbon member can be produced using a printing method, the counter electrode can be provided easily and inexpensively. Moreover, the electrode using the porous carbon member of the present invention can be formed without reducing the adhesion to the substrate even when the porous carbon member is formed as a film on the substrate. .

FIG. 3 is a schematic cross-sectional view showing a structural example of a photoelectric conversion element including an electrode as a counter electrode according to the present invention, and shows a case where it is applied to a dye-sensitized solar cell.
This photoelectric conversion element 100 includes a first substrate 101 having a porous semiconductor electrode 103 (hereinafter also referred to as a dye-sensitized semiconductor electrode) 103 carrying a sensitizing dye formed on one surface, and a conductive film 104. The main component is the second substrate 105 and the electrolyte layer 106 made of, for example, a gel electrolyte enclosed between them.

  In other words, the photoelectric conversion element 100 shown in FIG. 3 includes a working electrode (window electrode) 108 having a porous oxide semiconductor layer 103 in which a sensitizing dye is supported on the surface, and a porous oxide semiconductor layer of the working electrode. A counter electrode 109 disposed on the side of the counter electrode 109 and an electrolyte layer 106 at least in part between the two electrodes are provided.

  At this time, in particular, the counter electrode 109 is composed of at least the porous carbon member 104 on the side in contact with the electrolyte layer 106, and the void existing in the porous carbon member increases in the thickness direction as it approaches the electrolyte layer 106. What was comprised in this is preferable.

Next, as an embodiment of the photoelectric conversion element using the electrode according to the present invention, a case where a porous carbon member is formed on a substrate as a film and used as an electrode will be described.
First, a window electrode substrate is formed by forming a transparent conductive film 102 on a first substrate such as a glass plate. As a method for forming the transparent conductive film, a known method may be used depending on the material of the transparent conductive film. For example, a sputtering method, a CVD method (vapor phase growth method), an SPD method (spray pyrolysis deposition method). A thin film made of an oxide semiconductor such as tin-added indium oxide (ITO) is formed by a vapor deposition method or the like. Thereby, an electroconductive board | substrate is comprised. And if this transparent conductive film is too thick, the light transmittance is inferior, while if it is too thin, the conductivity is inferior, so that both the light transmittance and the conductivity are taken into consideration. The film is formed to a thickness of about 10 μm.

Next, a window electrode as a working electrode is formed by forming a porous oxide semiconductor layer on the transparent conductive film. As a method for forming a porous oxide semiconductor layer, for example, a titanium dioxide (TiO ₂ ) powder is mixed with a dispersion medium to prepare a paste, and this is used for a screen printing method, an ink jet printing method, a roll coating method, a doctor blade. It coats on a conductive substrate by a method, a spin coat method, etc. This porous oxide semiconductor layer is formed to a thickness of about 1 μm to 50 μm.
And a pigment | dye is carry | supported by a porous oxide semiconductor layer by immersing the window pole in which the porous oxide semiconductor layer was formed in a pigment | dye liquid.

On the other hand, on a second substrate such as a titanium (Ti) plate, a carbon film having a polyethylene glycol content changed as a solvent is applied or printed to form a carbon film, which is then heated to contain polyethylene By evaporating the glycol, a counter electrode having a porous carbon member is formed.
As a method for forming a porous carbon member, for example, in the case of a two-layer structure, first, a first carbon paste containing polyethylene glycol as a solvent is applied onto a second substrate by a screen printing method or the like, A carbon film is formed. Next, this carbon film is baked, for example, at 120 ° C. for 30 minutes. As a result, polyethylene glycol as a solvent evaporates from the carbon film, and voids are generated at the evaporated locations, thereby forming the first layer of the porous carbon member. After the firing, when the first layer of the fired porous carbon member is cooled to, for example, around 80 ° C., a second carbon paste with a changed content of polyethylene glycol is subsequently applied onto the first layer to form a carbon film. Form and fire again at 120 ° C. for 30 minutes. Thereby, the 2nd layer of a porous carbon member is formed on the 1st layer of a porous carbon member, and it can be set as the porous carbon member of a two-layer structure. Therefore, a porous carbon member having a multi-layer structure can be formed by repeating this step for the desired number of layers to be laminated.
At this time, the size of the gap is desirably 20 nm or less in the vicinity region of the second base material and 50 nm to 10 μm in the remote region.

  Then, the porous oxide semiconductor layer of the window electrode and the porous carbon member of the counter electrode are arranged to face each other, and an electrolyte solution is filled as an electrolyte layer therebetween, and sealing is performed, whereby the counter electrode according to the present invention is provided. A dye-sensitized solar cell is manufactured as the photoelectric conversion element. In FIG. 3, reference numeral 107 denotes a sealing material, and 110 denotes an electrolyte solution inlet.

(Example)
EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.
First, in order to confirm that the electrode of the present invention is composed of a porous carbon member, and that the voids present in the porous carbon member are desirably large enough to approach the electrolyte layer sandwiched between the opposing working electrodes. Each counter electrode described below was prepared and its photoelectric conversion efficiency was measured.

  The carbon paste that forms the porous carbon member is polyvinylidene fluoride (hereinafter abbreviated as “PVdF”) as a binder for mesocarbon microbeads (carbon paste manufactured by Osaka Gas Co., Ltd., hereinafter abbreviated as “MCMB”). ) Was added as a first carbon paste with 10 wt% of N-methyl-2-pyrrolidone (hereinafter abbreviated as “NMP”) as a solvent, and 10 wt% of PVdF with respect to MCMB. , And 1 wt% of polyethylene glycol (molecular weight 20000), and an appropriate amount of NMP was added as a solvent to prepare a second carbon paste.

Next, as Example 1, a titanium plate having a size of 15 mm × 20 mm × 1 ^t was used as a base material, and the first carbon paste was applied on the upper surface, and baked at 120 ° C. for 30 minutes. Subsequently, the second carbon paste is applied to the upper surface of the fired first carbon paste, and is fired at 120 ° C. for 30 minutes, whereby a porous carbon member having a large void in the vicinity of the electrolyte layer is as large as 51 nm. Was prepared, and a counter electrode provided with 0.5 μm of a porous carbon member having a small pore size of 5 nm in the far side and 3 μm.

Further, as Comparative Example 1, a titanium plate having a size of 15 mm × 20 mm × 1 ^t was used as a base material, a second carbon paste was applied on the upper surface, and baked at 120 ° C. for 30 minutes. Subsequently, by applying the first carbon paste on the upper surface of the baked second carbon paste and baking it at 120 ° C. for 30 minutes, the size of the voids existing in the vicinity of the electrolyte layer is opposite to that in Example 1. A counter electrode comprising a porous carbon member having a thickness of 0.5 μm as small as 5 nm and a porous carbon member having a large void as large as 51 nm in the far side thereof was prepared.

Furthermore, as Comparative Example 2, a titanium plate having a size of 15 mm × 20 mm × 1 ^t was used as a base material, and the first carbon paste was applied on the upper surface and baked at 120 ° C. for 30 minutes. A counter electrode provided with 0.5 μm of a porous carbon member uniformly formed with a thickness of 5 nm or less was produced.

In addition, a heat-resistant glass having a size of 15 mm × 20 mm × 1 ^t is used as a first base material, and a thickness of 700 nm is formed as a transparent conductive layer made of an FTO / ITO bilayer film having a sheet resistance of 1 Ω / □ on the upper surface by SPD. Then, an electrode substrate was formed. In addition, a slurry dispersion aqueous solution of titanium oxide having an average particle diameter of 20 nm is applied onto the electrode substrate as a porous oxide semiconductor, dried, and treated at 450 ° C. for 1 hour, whereby a porous layer having a thickness of 7 μm is obtained. A quality oxide semiconductor layer was formed. This was immersed in an ethanol dye solution of ruthenium bipyridine complex (N3 dye) overnight to support the dye, thereby creating a window electrode.

Then, the prepared window electrode and each counter electrode are overlapped, and an ionic liquid containing iodine / iodide ion redox pair, 1-ethyl-3-methylimidazolium-bis (trifluoromethylsulfonyl), is used as an electrolytic solution. ) Imide (hereinafter abbreviated as “EMImTFSI”) was filled between both electrodes to form a test cell of a dye-sensitized solar cell, and the photoelectric conversion efficiency in the dye-sensitized solar cell was measured. At this time, the light irradiation condition was 100 mW / cm ² . The measurement results are shown in Table 1.
Moreover, the adhesiveness to the base material of each said counter electrode material was measured by the crosscut method (JISK5600). The measurement results are also shown in Table 1. In the adhesion column shown in Table 1, “good” indicates that 90% or more per unit area is not peeled off, and “defective” indicates that more than 10% is peeled off.

  As described above, the embodiment is based on the present invention in which the electrode is composed of a porous carbon member, and the voids in the porous carbon member are formed so as to be closer to the electrolyte layer sandwiched between the opposing working electrodes. It can be seen that the use of one counter electrode improves the photoelectric conversion efficiency and is desirable. Moreover, it can be seen that the counter electrode of Example 1 has good adhesion of the porous carbon member to the substrate.

  Next, in order to confirm that the photoelectric conversion efficiency is desirable even when compared with the counter electrode using other members by using the counter electrode having the structure based on Example 1, the counter electrodes described below are prepared. The photoelectric conversion efficiency was measured.

  First, 10 wt% of polyvinylidene fluoride (hereinafter abbreviated as “PVdF”) as a binder is mixed with mesocarbon microbeads (MCMB), and N-methyl-2-pyrrolidone (hereinafter referred to as a binder solvent). , Abbreviated as “NMP”) was added to prepare a first carbon paste. Next, 10 wt% of PVdF and 1 wt% of polyethylene glycol (molecular weight 20000) were mixed with respect to MCMB, and an appropriate amount of NMP was added as a binder solvent to prepare a second carbon paste. Further, 10 wt% of PVdF and 3 wt% of polyethylene glycol (molecular weight 20000) were mixed with MCMB, and an appropriate amount of NMP was added as a solvent to prepare a third carbon paste.

Then, as Example 2, a titanium plate having a size of 15 mm × 20 mm × 1 ^t was used as the second base material, and the first carbon paste was applied on the upper surface, and baked at 120 ° C. for 30 minutes. Subsequently, the second carbon paste was applied to the upper surface of the fired first carbon paste and fired at 300 ° C. for 30 minutes. Furthermore, the counter electrode which consists of a three-layer porous carbon member was produced by apply | coating a 3rd carbon paste on the upper surface of a 2nd carbon paste, and baking for 30 minutes at 300 degreeC.
When the cross section of the prepared counter electrode was observed with a scanning electron microscope (hereinafter abbreviated as “SEM”), the surface on which the third carbon paste was applied had many voids, and the first carbon paste in contact with the titanium plate was removed. In the coated part, there were few voids and the carbon was dense.

Next, as Example 3, a counter electrode made of a three-layered porous carbon electrode was prepared in the same manner as the counter electrode described in Example 2, using a carbon plate instead of a titanium plate.
When the cross section of the created counter electrode was similarly observed with an SEM, the surface on which the third carbon paste was applied had many voids as in the counter electrode described in Example 2, and the first carbon paste in contact with the carbon plate was applied. The part had few voids and carbon was dense.

Moreover, as Comparative Example 3, a counter electrode was prepared by using an FTO glass electrode substrate having a size of 15 mm × 20 mm × 3 ^t and covering the upper surface thereof with an electrode layer made of platinum by a sputtering method to a thickness of 100 nm.
Next, as Comparative Example 4, a counter electrode was produced by using a titanium plate having a size of 15 mm × 20 mm × 3 ^t and forming a carbon film with a thickness of 100 nm on the upper surface thereof by vapor deposition.
Further, as Comparative Example 5, a carbon plate having a size of 15 mm × 20 mm × 1 ^t was used as a counter electrode.
The production and evaluation of the cell were the same as in Example 1. The measurement results are shown in Table 2.

  As described above, in Examples 2 and 3 using the porous carbon electrode as the counter electrode, the power generation characteristics do not deteriorate as in the case where the conventional carbon as shown in Comparative Examples 4 and 5 is used as the counter electrode. It turns out that it becomes a desirable thing which has a photoelectric conversion efficiency equivalent to platinum as shown in the comparative example 3. Therefore, it can be used as a counter electrode using chemically stable carbon without using platinum which is expensive and may be dissolved depending on the electrolyte to cause deterioration of power generation characteristics, and has excellent long-term stability. A photoelectric conversion element can be provided.

It is a schematic sectional drawing which shows the structure of the photoelectric conversion element using the electrode which concerns on this invention. It is a partial expanded schematic sectional drawing which shows the electrode structure of the photoelectric conversion element of FIG. It is a schematic sectional drawing which shows the structural example of the dye-sensitized solar cell using the electrode which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Photoelectric conversion element (dye sensitized solar cell), 2 1st base material, 2nd base material, 4 transparent conductive layer, 5 porous oxide semiconductor layer, 6 electrolyte layer, 7 multilayer carbon member, 8 window pole ( Working electrode), 9 counter electrode, 10, 20 cell structure.

Claims (3)

An electrode that forms a counter electrode that is disposed with an electrolyte layer interposed at least in part with respect to the working electrode,
The electrode is characterized in that the side in contact with the electrolyte layer is composed of at least a porous carbon member, and the voids in the porous carbon member are larger in the thickness direction as they approach the electrolyte layer.   The electrode according to claim 1, wherein the porous carbon member has a multilayer structure. A working electrode having a porous oxide semiconductor layer carrying a sensitizing dye on its surface, a counter electrode disposed opposite to the working electrode on the porous oxide semiconductor layer side of the working electrode, and at least between these two electrodes A photoelectric conversion element comprising at least an electrolyte layer in part,
The counter electrode is composed of at least a porous carbon member on a side in contact with the electrolyte layer, and a void existing in the porous carbon member is larger in a thickness direction as it approaches the electrolyte layer. element.

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