JP2012064485A - Dye-sensitized photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dye-sensitized photoelectric conversion device which is useful as a solar cell and exhibits improved utilization of light.SOLUTION: A dye-sensitized photoelectric conversion device 10 has at least the following constituents disposed therein in order from the light incident side: a light transmissive support 1; a light transmitting conductive layer 2 provided on the surface of the light transmissive support 1 on a side opposite to the light incident side; a porous semiconductor layer 3 which supports a photosensitization pigment 13; an electrolyte layer 4 which is disposed for an electrolyte to infiltrate into the porous semiconductor layer 3 and also composed of a high refractive index material whose refractive index is higher by 0.3 or more than that of the electrolyte, and further contains high refractive index fine particles 14 having an anisotropic shape whose major axis to minor axis ratio is 2 or greater; and a counter electrode 5. The high refractive index fine particles 14 should preferably consist of titanium oxide TiOfine particles, etc. whose average major axis is 0.3 μm or more and whose major axis to minor axis ratio is 2 or greater, and which comes in a shape, for example, like a needle, a rod, or an elliptic body.

Description

  The present invention relates to a dye-sensitized photoelectric conversion device useful as a solar cell or the like, and more particularly to a dye-sensitized photoelectric conversion device having an improved light utilization rate.

  Carbon dioxide is generated when fossil fuels such as coal and oil are used as energy sources. Carbon dioxide is one of the causative substances that cause global warming. In the use of nuclear energy, radioactive elements are generated and there is a risk of radioactive contamination. Moreover, these energy resources are limited and will eventually be exhausted. Therefore, reliance on these energy sources is problematic. In recent years, sunlight has attracted attention as an inexhaustible energy source to replace them. A solar cell is a photoelectric conversion device that converts the energy of sunlight into electrical energy, and uses sunlight as an energy source, and therefore has a very small influence on the global environment. For this reason, further spread of solar cells is expected.

  Various things are proposed as a principle and constituent material of a solar cell. Among them, solar cells using a semiconductor pn junction are currently most popular, and many solar cells using silicon as a semiconductor material are commercially available. However, manufacturing a solar cell using a pn junction requires a process for manufacturing a high-purity semiconductor material and a process for forming a pn junction. For this reason, there exists a problem that energy consumption in manufacturing processes, such as a high temperature process, is large. In addition, since the number of manufacturing processes is large and a large-scale apparatus such as a clean room or a vacuum apparatus is necessary, there is a problem that the manufacturing cost increases.

  On the other hand, a dye-sensitized solar cell using photoinduced electron transfer photosensitized by a dye has been proposed by Gretzel et al. (Patent Publication No. 2664194 (2nd and 3rd pages, FIG. 1)) and B (See O'Regan and M. Graetzel, Nature, 353, p. 737-740 (1991).)

  FIG. 6 is a cross-sectional view of a main part showing the structure of a general dye-sensitized solar cell 100. The dye-sensitized solar cell 100 mainly includes a transparent substrate 101 such as glass, a transparent conductive layer (negative electrode current collector) 102, a semiconductor electrode layer (negative electrode) 103 holding a photosensitizing dye, an electrolyte layer 104, a counter electrode. (Positive electrode) 105, counter substrate 106, and sealing material (not shown).

The transparent conductive layer 102 is made of ITO (Indium Tin Oxide) or FTO (fluorine-doped tin oxide), and is provided on the transparent substrate 101 as a negative electrode current collector. Function. The semiconductor electrode layer 103 that is a negative electrode is provided in contact with the transparent conductive layer 102. As the semiconductor electrode layer 103, a porous layer obtained by sintering fine particles of a metal oxide semiconductor such as titanium oxide TiO ₂ is often used. The photosensitizing dye is adsorbed on the surface of the metal oxide constituting the semiconductor electrode layer 103. As the electrolyte layer 104, an electrolytic solution containing a redox species (redox pair) or the like is used. The counter electrode 105 is composed of a platinum layer or the like, and is provided on the counter substrate 106.

  The dye-sensitized solar cell 100 is configured such that light enters from the transparent substrate 101 side. A part of the incident light is absorbed by the photosensitizing dye, and a part of the electrons excited by the light absorption is extracted to the semiconductor electrode layer 103. On the other hand, the photosensitizing dye that has lost electrons is reduced by the reducing agent in the electrolyte layer 104. The oxidizing agent generated in the electrolyte layer 104 by this reaction receives electrons from the counter electrode (positive electrode) 105 and is reduced. As a result, the dye-sensitized solar cell 100 operates as a photovoltaic cell having the transparent conductive layer 102 and the semiconductor electrode layer 103 as a negative electrode and the counter electrode 105 as a positive electrode.

  Dye-sensitized solar cells do not require a vacuum treatment process for manufacturing, so large-scale equipment is not required, and inexpensive oxide semiconductors such as titanium oxide are used to manufacture with low productivity and high productivity. There are advantages. In addition, there are various photosensitizing dyes that can absorb light in each wavelength region in a wide wavelength region centered on the visible light region. Therefore, the wavelength of light to be absorbed can be selected by changing the dye used, or multiple By combining these dyes, there is an advantage that light in a wide wavelength region can be used. In addition, it has the potential to be manufactured at a lower cost with higher productivity by a roll-to-roll process using a lightweight and flexible substrate such as plastic. For this reason, it has attracted much attention in recent years as a new generation solar cell.

  However, at present, the photoelectric conversion efficiency of the dye-sensitized solar cell is still lower than the photoelectric conversion efficiency of the silicon-based solar cell. Therefore, various efforts have been reported to improve photoelectric conversion efficiency. For example, a technique is known in which the semiconductor electrode layer 103 is provided with a light scattering function, the utilization rate of incident light is improved, and the photoelectric conversion efficiency is improved.

  For example, in Patent Document 1 described later, as shown in FIG. 7, a glass substrate 201, an electrode 206, a highly refractive material thin film 207, a light-absorbing particle layer 203, a light-reflecting particle layer 208, an electrolyte part 204, and a counter electrode A dye-sensitized solar cell 200 composed of 205 has been proposed. Patent Document 1 explains as follows.

  The electrode 206 is made of a metal formed in a lattice shape or a plurality of belt shapes. The high refractive material thin film 207 is a thin film of a high refractive index material such as titanium oxide (rutile), for example, and the film thickness is preferably about 50 to 100 nm. The light absorbing particle layer 203 is a layer in which the semiconductor fine particles 213 are deposited on the glass substrate 201 on which the high refractive material thin film 207 is formed and the photosensitizing dye is adsorbed. The semiconductor fine particles 213 are, for example, titanium oxide fine particles (anatase), and the particle diameter is preferably about 80 nm or less, and the thickness of the light absorption particle layer 203 is preferably about 10 μm or less. The light reflecting particle layer 208 is a layer obtained by depositing highly refractive material particles 218 on the light absorbing particle layer 203. The high refractive material particles 218 are, for example, titanium oxide fine particles (rutile), and the particle diameter is preferably about 200 to 500 nm, and the thickness of the light reflecting particle layer 208 is preferably about 5 to 10 μm. The electrolytic solution portion 204 includes the light absorbing particle layer 203 and the light reflecting particle layer 208, or is provided so that the electrolytic solution infiltrates the light absorbing particle layer 203 and the light reflecting particle layer 208.

  One of the features of the dye-sensitized solar cell 200 is that the particle size of the high refractive material particles 218 is controlled in a range of about 200 to 500 nm so that light scattering is maximized. Thereby, the light once transmitted through the light absorbing particle layer 203 can be efficiently reflected by the light reflecting particle layer 208 and returned to the light absorbing particle layer 203 again. Scattering by the light-reflecting particle layer 208 is performed so that the scattering angle of the first-order diffracted wave due to the scattering becomes an angle that causes scattering corresponding to total reflection between the electrolytic solution and the high-refractive material particles 218. The maximum is obtained when the particle size is controlled.

  Another feature of the dye-sensitized solar cell 200 is that the light reflected by the light-reflecting particle layer 208 and returned to the light-absorbing particle layer 203 is reflected even if it passes through the light-absorbing particle layer 203 again. Most of the light is totally reflected by the high refractive material thin film 207 and returned to the light absorbing particle layer 3 again. Note that the high-refractive-material thin film 207 acts in the same manner as the antireflection film for the incidence of light from the glass substrate 201 side, and thus does not reduce the transmission of incident light.

  Thus, the light once incident on the light-absorbing particle layer 203 of the dye-sensitized solar cell 200 repeats scattering by the light-reflecting particle layer 208 and total reflection by the high-refractive-index thin film 207, whereby light-absorbing particles. Confined within layer 203. For this reason, even if the light-absorbing particle layer 203 is thinned, incident light is effectively absorbed by the photosensitizing dye. The conversion efficiency can be significantly increased by improving the current collection efficiency and reducing the resistance by thinning the light absorbing particle layer 203.

  It is also possible to adsorb the photosensitizing dye also to the high refractive material particles 218 of the light reflecting particle layer 208 so that photoelectric conversion is performed also in the light reflecting particle layer 208 to increase the conversion efficiency. Further, in the dye-sensitized solar cell 200, the example in which the high refractive material particles 218 are deposited on the light absorbing particle layer 203 as the light reflecting particle layer 208 has been shown, but the high refractive material particles 218 are placed in the electrolytic solution portion 204. You may make it disperse | distribute. Further, the high refractive material particles 208 use titanium oxide particles having a particle size of 1.3 × π / k with respect to the wave number k of light, and the particle size is included in the range of about 200 to 500 nm. The

  In addition, a configuration is proposed in which coarse particles for the purpose of light scattering are added to the light-absorbing particle layer instead of the laminated structure such as the light-absorbing particle layer 203 and the light-reflecting particle layer 208 described above. . For example, in Non-Patent Document 1 described later, in order to realize a high-performance dye-sensitized solar cell, the particle size and shape of titanium oxide fine particles suitable for light scattering are studied, and hexagonal star-shaped high-purity titanium oxide fine particles An example is shown in which 10% photoelectric conversion efficiency could be achieved by adding.

  In the conventional semiconductor electrode layer 103 of the general dye-sensitized solar cell 100, titanium oxide fine particles having a particle diameter of several tens of nanometers are used so that a large surface area can be adsorbed. It is done. In this case, the transparency of the semiconductor electrode layer 103 is high, and the incident light is not sufficiently absorbed by the photosensitizing dye, and part of the light is transmitted through the semiconductor electrode layer 103. As a result, the absorption rate of the incident light is low. There is a problem of becoming enough. This is remarkable in the wavelength region where the absorption coefficient of the photosensitizing dye is low. As a countermeasure, when the thickness of the semiconductor electrode layer 103 is increased, the light absorption rate is improved. However, when the thickness is excessively increased, the conversion efficiency is decreased due to a decrease in the current collection efficiency and an increase in the internal resistance. That is, the thickness of the semiconductor electrode layer 103 has an optimum thickness, and the utilization rate of light energy cannot be improved only by adjusting the thickness of the semiconductor electrode layer 103.

  Therefore, a high-refractive material particle having a large particle diameter that easily scatters light is used to form the light-reflecting particle layer 208 as in Patent Document 1 or an oxide that constitutes a semiconductor electrode layer as in Non-Patent Document 1. Proposals have been made to reduce the amount of light transmitted through mixing in the fine particle layer and to improve the light utilization rate. With such a device, it is possible to increase the light absorption rate by increasing the optical path or confining light by utilizing the multiple scattering effect of light. However, if the thickness of the light reflecting particle layer 208 or the semiconductor electrode layer 103 is excessively increased, the internal resistance is increased, so that the transmitted light cannot be eliminated. The light transmitted through the semiconductor electrode layer 103 and the light reflecting particle layer 208 is absorbed by the electrolytic solution and the counter electrode and cannot be used.

  Further, Patent Document 1 describes that the high refractive material particles 218 may be dispersed in the electrolytic solution portion 204, but an example in which this is actually performed is not shown.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a dye-sensitized photoelectric conversion device that is useful as a solar cell or the like and has improved light utilization.

That is, the present invention, in order from the light incident side, at least,
A light transmissive substrate;
A light transmissive conductive layer provided on a surface of the light transmissive substrate opposite to the light incident side;
A porous semiconductor layer holding a photosensitizing dye;
High-refractive-index fine particles that are arranged so as to infiltrate the porous semiconductor layer and that are made of a high-refractive-index material having a refractive index that is 0.3 or more larger than that of the electrolytic solution and have an anisotropic shape An electrolyte layer containing,
The present invention relates to a first dye-sensitized photoelectric conversion device in which a counter electrode is disposed.

Also, in order from the light incident side, at least,
A light transmissive substrate;
A light transmissive conductive layer provided on a surface of the light transmissive support opposite to the light incident side; and
A porous semiconductor layer holding a photosensitizing dye;
The electrolyte solution is arranged so as to infiltrate the porous semiconductor layer. In addition, the electrolyte solution is made of a high refractive index material having a refractive index of 0.3 or more larger than that of the electrolyte solution, and two or more types of spherical shapes having different average particle diameters. An electrolyte layer containing fine particles of high refractive index;
The present invention relates to a second dye-sensitized photoelectric conversion device in which a counter electrode is disposed.

  According to the dye-sensitized photoelectric conversion device of the present invention, the electrolyte layer contains high refractive index fine particles made of a high refractive index material having a refractive index of 0.3 or more larger than that of the electrolytic solution. For this reason, the transmitted light once transmitted through the porous semiconductor layer can be efficiently scattered on the surface of the high refractive index fine particles and returned again into the porous semiconductor layer. Thereby, the utilization factor of light can be increased. As will be described later in the examples, in order to efficiently scatter transmitted light on the surface of the high refractive index fine particles, the refractive index of the high refractive index fine particles is set to be less than the refractive index of the surrounding electrolyte. It must be 3 or larger.

  At this time, when the high refractive index fine particles are spherical, the optimum particle diameter capable of scattering the transmitted light most effectively varies depending on the wavelength, and the wavelength of the transmitted light is 400 nm and 800 nm. It differs by about 2 times. In the second dye-sensitized photoelectric conversion device of the present invention, since the electrolyte layer contains two or more types of spherical high refractive index fine particles having different average particle diameters, transmitted light having a wavelength of 400 to 800 nm can be efficiently obtained. Can be scattered. On the other hand, in the first dye-sensitized photoelectric conversion device of the present invention, the electrolyte layer contains the high refractive index fine particles having the anisotropic shape. The high refractive index fine particles having the anisotropic shape change the effective particle diameter with respect to the transmitted light according to the change in the orientation direction thereof, and therefore the high refractive index fine particles having one kind of average particle diameter are light having a wavelength of 400 to 800 nm. Can be efficiently scattered.

It is the schematic which shows the cross-section of the dye-sensitized photoelectric conversion apparatus based on Embodiment 1 of this invention. It is the schematic which shows the cross-section of the dye-sensitized photoelectric conversion apparatus based on a modification. It is the schematic which shows the cross-section of the dye-sensitized photoelectric conversion apparatus based on Embodiment 2 of this invention. It is a graph which shows the current-voltage characteristic of the dye-sensitized photoelectric conversion apparatus by Example 6 and Comparative Examples 3-9 of this invention. It is a graph which shows the photoelectric conversion efficiency of the dye-sensitized photoelectric conversion apparatus by Example 6 and Comparative Examples 3-9 of this invention. It is the schematic which shows an example of the cross-sectional structure of the conventional common dye-sensitized solar cell. It is the schematic which shows the cross-section of the dye-sensitized solar cell shown by patent document 1. FIG.

  In the first dye-sensitized photoelectric conversion device of the present invention, the refractive index of the high refractive index fine particles is preferably 1.7 or more and the average major axis is preferably 0.3 μm or more.

  The ratio of the major axis to the minor axis of the high refractive index fine particles is preferably 2 or more.

  The anisotropic shape may be a needle shape, a rod shape, a spindle shape, an ellipsoid shape, or a capsule shape.

  Moreover, it is preferable that spherical or granular fine particles having a ratio of the major axis to the minor axis of less than 2 are further contained in the electrolyte layer. At this time, the spherical or granular fine particles are preferably made of a high refractive index material having a refractive index larger by 0.3 or more than that of the electrolytic solution. The average particle diameter of the spherical or granular fine particles is preferably not less than the short diameter and not more than the long diameter of the high refractive index fine particles.

  In the second dye-sensitized photoelectric conversion device of the present invention, it is preferable that the refractive index of the high refractive index fine particles is 1.7 or more.

  Further, it is preferable to add at least two kinds of the spherical high refractive index fine particles whose average particle diameter is different by a maximum of 2 times.

In the first and second dye-sensitized photoelectric conversion devices of the present invention, the high refractive index fine particles may be titanium oxide TiO ₂ fine particles.

  Moreover, it is good that the content rate of the said high refractive index fine particle in the said electrolyte layer is 1-50 mass%.

  Moreover, it is preferable that the electrolyte layer contains a gelling agent. The gelling agent is used for the purpose of turning a liquid electrolyte into a gel.

  Hereinafter, based on the embodiment of the present invention, details will be specifically described with reference to the drawings.

[Embodiment 1]
In Embodiment 1, an example suitable as a dye-sensitized solar cell will be described as an example of the dye-sensitized photoelectric conversion device described in claims 1 to 7 and 11 to 13.

  FIG. 1 is a schematic diagram showing a cross-sectional structure of a dye-sensitized photoelectric conversion device 10 according to Embodiment 1 of the present invention. The dye-sensitized photoelectric conversion device 10 mainly includes a light-transmitting substrate 1, a light-transmitting conductive layer (negative electrode current collector) 2, a porous semiconductor layer (negative electrode) 3 holding a photosensitizing dye, an electrolyte layer 4, It is composed of a counter electrode (positive electrode) 5, a counter substrate 6, and a sealing material (not shown).

The porous semiconductor layer (negative electrode) 3 is a porous layer made of metal oxide semiconductor fine particles such as titanium oxide TiO _2, and the photosensitizing dye 13 is held on the surfaces of the metal oxide semiconductor fine particles 11 and 12. Yes. The porous semiconductor layer (negative electrode) 3 includes a transmission layer 3a composed of semiconductor fine particles 11 having a small average particle diameter, semiconductor fine particles 11 having a small average particle diameter, and semiconductor fine particles 12 having a large average particle diameter. It is preferable to include a scattering layer 3b having a function of scattering transmitted light that has been transmitted without being absorbed by the layer 3a and returning it to the transmission layer 3a. Thereby, the utilization factor of light can be increased.

Further, as a feature of the present embodiment, high refractive index fine particles 14 having an anisotropic shape are included in the electrolyte layer 4. The high refractive index fine particles 14 are made of a high refractive index material having a refractive index larger by 0.3 or more than the electrolytic solution constituting the electrolyte layer 4. For this reason, the light once transmitted through the porous semiconductor layer 3 can be efficiently scattered on the surface of the high refractive index fine particles 14 and returned to the porous semiconductor layer 3 again. Thereby, the utilization factor of light can be further increased. As shown in the examples described later, in order to efficiently scatter transmitted light on the surface of the high refractive index fine particles 14, the refractive index of the high refractive index fine particles 14 is 0.3 compared to the refractive index of the surrounding electrolyte. More than that is necessary. Since the refractive index of the electrolytic solution is about 1.45 to 1.50, the refractive index of the high refractive index fine particles 14 is preferably about 1.75 to 1.80. For example, the high refractive index fine particles 14 are preferably titanium oxide TiO ₂ fine particles.

  When the high-refractive-index fine particles are spherical, the optimum particle diameter that can scatter the transmitted light most effectively varies depending on the wavelength. Therefore, to efficiently scatter the transmitted light, the particles of the high-refractive-index fine particles It is necessary to adjust the diameter to the wavelength of transmitted light. When the high-refractive-index fine particles are spherical fine particles having uniform optical properties without anisotropy, the optimum particle diameter Dopt at which light scattering is maximized can be calculated by Mie's scattering theory. . However, since the general formula of the Mie theory is very complicated, a plurality of empirical formulas have been proposed for the optimum particle diameter Dopt (see Non-Patent Document 1). In these empirical formulas, the optimum particle size is proportional to the wavelength.

Table 1 shows values of optimum particle diameters calculated based on these empirical formulas. Here, the spherical particles are titanium oxide, and the solvent is acetonitrile.

  As shown in Table 1, the optimum particle diameter (minimum value) of the high refractive index fine particles that most effectively scatter light with a wavelength of 400 nm is 0.15 to 0.22 μm. The optimum particle diameter of the high refractive index fine particles that most effectively scatter light having a wavelength of 800 nm is 0.30 to 0.45 μm (maximum value). Therefore, in order to efficiently scatter all the transmitted light having a wavelength of 400 to 800 nm, it is ideally necessary to add very many kinds of spherical fine particles having various particle diameters from the minimum value to the maximum value. Even if this is impossible in practice, it is necessary to add at least a plurality of types of spherical fine particles having a particle diameter that is twice as large as the maximum.

  On the other hand, in the present embodiment, since the high refractive index fine particles 14 have an anisotropic shape, the effective particle diameter with respect to the transmitted light continuously changes depending on the orientation direction. Therefore, in the high refractive index fine particles 14 having an anisotropic shape, high refractive index fine particles having an average major axis of 0.3 μm or more and a ratio of the major axis to the minor axis of 2 or more are used, as shown in Examples described later. If used, it is possible to efficiently scatter all light having a wavelength of 400 to 800 nm by adding only one kind. The anisotropic shape is not particularly limited, and examples thereof include a needle shape, a rod shape, a spindle shape, an ellipsoid shape, and a capsule shape.

  FIG. 2 is a schematic diagram showing a cross-sectional structure of a dye-sensitized photoelectric conversion device 20 based on a modification of the embodiment of the present invention. In the dye-sensitized photoelectric conversion device 20, the electrolyte layer 4 includes fine particles 15 that are spherical and have an average diameter that is greater than or equal to the minor axis of the high refractive index fine particles 14 and less than or equal to the major axis. When the electrolyte layer 4 is thinly formed so that the fine particles 15 become spacers between the porous semiconductor layer 3 and the counter electrode 5, the long diameter of the high refractive index fine particles 14 is larger than the thickness of the electrolyte layer 4. They are oriented so that they are approximately parallel to the plane, that is, approximately perpendicular to the path of transmitted light. As a result, compared with the case where the high refractive index fine particles 14 are randomly oriented, the transmitted light can be efficiently scattered and returned into the porous semiconductor layer 3, thereby increasing the light utilization rate. Can do.

  At this time, the spherical fine particles 15 are preferably made of a high refractive index material having a refractive index of 0.3 or more larger than that of the electrolytic solution. In this way, the spherical fine particles 15 also function as high refractive index material particles that efficiently scatter the transmitted light once transmitted through the porous semiconductor layer 3 on the surface and return the light into the porous semiconductor layer 3 again. To do.

The content of the high refractive index fine particles 14 in the electrolyte layer 4 is preferably 1 to 50% by mass.
If the content of the high refractive index fine particles 14 is less than 1% by mass, the significant effect of the high refractive index fine particles 14 cannot be obtained. If the content of the high refractive index fine particles 14 exceeds 50% by mass, handling becomes difficult.

  The electrolyte layer 4 preferably contains a gelling agent. In order to reduce the leakage of the electrolyte solution from the dye-sensitized solar cell 20 and the volatilization of the solvent constituting the electrolyte solution, in addition to dissolving the gelling agent, polymer, crosslinking monomer, etc. in the electrolyte composition, inorganic ceramics It is also possible to disperse the particles and use it as a gel electrolyte. As for the ratio of the gel material and the electrolyte composition, the more the electrolyte composition, the higher the ionic conductivity, but the lower the mechanical strength. On the contrary, when there are too few electrolyte components, although mechanical strength is large, ionic conductivity falls.

  Further, when the electrolyte is an electrolyte gelled using a polymer or the like, or an all solid electrolyte, a polymer solution containing an electrolyte and a plasticizer is applied on the semiconductor electrode layer by a casting method or the like. Thereafter, the plasticizer is volatilized and completely removed, and then sealed with a sealing material in the same manner as described above. This sealing is preferably performed using a vacuum sealer or the like in an inert gas atmosphere or in a reduced pressure. After sealing, it is possible to perform heating and pressurizing operations as necessary so that the electrolyte solution of the electrolyte layer sufficiently penetrates into the semiconductor electrode layer.

The other members of the dye-sensitized photoelectric conversion device 10 or 20 are the same as those of the conventional dye-sensitized solar cell. That is, the light transmissive substrate 1 is made of a glass plate or a plastic film such as PEN or PET. The light transmissive conductive layer (negative electrode current collector) 2 is made of ITO, FTO, or the like, and is provided on the light transmissive substrate 1. The electrolyte layer 4 is disposed between the porous semiconductor layer 3 and the counter electrode 5, and I ⁻ / I ₃ ⁻ (triiodide ion I ₃ ⁻ is present as ions by combining I ₂ with iodide ion I ^−. It is composed of an electrolytic solution containing a redox species (redox pair). The electrolytic solution is arranged so as to be able to infiltrate the porous semiconductor layer 3. The counter electrode 5 is made of a platinum layer, a carbon layer, or the like laminated on the base layer, and is provided on the counter substrate 6. The counter substrate 6 is made of a glass plate or a plastic film.

  When light is incident, the dye-sensitized photoelectric conversion devices 10 and 20 operate as a photovoltaic cell having the counter electrode 5 as a positive electrode and the semiconductor electrode layer 3 as a negative electrode.

  That is, when the photosensitizing dye 13 absorbs photons transmitted through the light-transmitting substrate 1 and the light-transmitting conductive layer 2, the electrons in the photosensitizing dye 13 are excited from the ground state to the excited state. Excited electrons are taken out to the conduction band of the porous semiconductor layer 3 through electrical coupling between the photosensitizing dye 13 and the porous semiconductor layer 3, and light is transmitted through the porous semiconductor layer 3. The conductive conductive layer 2 is reached.

On the other hand, the photosensitizing dye 13 that has lost electrons is converted from the reducing agent in the electrolyte layer 4, for example, I ⁻ to the following reaction 2I ⁻ → I ₂ + 2e ^{−.
_{I 2 + I - → I 3}} -
To receive electrons and produce an oxidizing agent, for example, I ₃ ⁻ in the electrolyte layer 4. The generated oxidant reaches the counter electrode 5 by diffusion, and the reverse reaction of the above reaction I ₃ ⁻ → I ₂ + I ⁻
I ₂ + 2e ^- → 2I ^-
Thus, electrons are received from the counter electrode 5 and reduced to the original reducing agent.

  The electrons flowing out from the light-transmissive conductive layer 2 to the external circuit return to the counter electrode 5 after performing electrical work in the external circuit. In this way, light energy is converted into electrical energy without leaving any change in the photosensitizing dye 13 or the electrolyte layer 4.

  In order to fabricate the dye-sensitized photoelectric conversion device 10 or 20, first, a fine particle layer made of metal oxide semiconductor fine particles is formed on the light transmissive conductive layer 2 provided on the light transmissive substrate 1, and then fired. Thus, a metal oxide semiconductor porous layer (porous semiconductor layer) 3 is formed. Next, a photosensitizing dye is adsorbed on the porous semiconductor layer 3. The method for adsorbing the dye is not particularly limited. For example, a solution in which a dye molecule is dissolved is prepared, and the light-transmitting substrate 1 on which the porous semiconductor layer 3 is formed is immersed in the dye solution, or porous. After the dye solution is soaked into the porous semiconductor layer 3 by applying, spraying, or dropping the dye solution to the porous semiconductor layer 3, the solvent is evaporated. Next, the light transmissive substrate 1 and the counter substrate 6 are disposed so that the porous semiconductor layer 3 and the counter electrode 5 face each other, and are bonded together with a sealant 7. Finally, an electrolyte solution is injected to form the electrolyte layer 4.

  The metal oxide semiconductor porous layer (porous semiconductor layer) 3 has a large actual surface area including the surface of fine particles facing pores in the porous layer so that a large amount of photosensitizing dye can be adsorbed. The actual surface area of the porous semiconductor layer 3 is preferably 10 times or more, more preferably 100 times or more the area (projected area) of the outer surface of the porous semiconductor layer 3.

  Generally, as the thickness of the porous semiconductor layer 3 increases and the number of semiconductor fine particles 11 or 12 contained per unit projected area increases, the actual surface area increases and the amount of dye that can be held per unit projected area increases. Therefore, the light absorption rate with respect to incident light becomes high. On the other hand, when the thickness of the porous semiconductor layer 3 increases, the distance that electrons transferred from the photosensitizing dye 13 to the porous semiconductor layer 3 diffuse until reaching the light-transmissive conductive layer 2 increases. The loss of electrons due to charge recombination in the semiconductor layer 3 also increases. Accordingly, the porous semiconductor layer 3 has a preferable thickness, but is generally 0.1 to 100 μm, and more preferably 1 to 30 μm.

  The other members of the dye-sensitized photoelectric conversion devices 10 and 20 are the same as those of the conventional dye-sensitized solar cell, but will be described in further detail below.

  The porous semiconductor layer is typically provided on a light transmissive conductive substrate. The light-transmitting conductive substrate may be a light-transmitting conductive layer formed on a conductive or non-conductive light-transmitting substrate, or may be a conductive light-transmitting substrate as a whole. . The material of the light transmissive substrate is not particularly limited, and various base materials can be used as long as they are light transmissive. This light-transmitting substrate is preferably one that is excellent in moisture and gas barrier properties, solvent resistance, weather resistance, and the like that enter from the outside of the dye-sensitized photoelectric conversion device. Specifically, quartz, sapphire, glass, etc. Optically transparent inorganic material substrate, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyethylene, polypropylene, polyphenylene sulfide, polyvinylidene fluoride, tetraacetylcellulose, brominated phenoxy, aramids, polyimides, polystyrenes, polyarylates Examples thereof include light-transmitting plastic substrates such as polysulfones and polyolefins. Among these, it is preferable to use a substrate having a high transmittance in the visible light region, but it is not limited thereto. As this light-transmitting substrate, it is preferable to use a light-transmitting plastic substrate in consideration of processability and lightness. The thickness of the light-transmitting substrate is not particularly limited, and can be freely selected depending on the light transmittance, the shielding property between the inside and outside of the dye-sensitized photoelectric conversion device, and the like.

  The lower the surface resistance (sheet resistance) of the light transmissive conductive substrate, the better. Specifically, the surface resistance of the light-transmitting conductive substrate is preferably 500Ω / □ or less, and more preferably 100Ω / □. When a light transmissive conductive film is formed on a light transmissive substrate, a known material can be used as the material of the light transmissive conductive film. Specifically, indium-tin composite oxide (ITO), Fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), tin oxide, zinc oxide, indium / zinc composite oxide (IZO), etc. are included, but are not limited to these. Two or more types can be used in combination. In addition, for the purpose of reducing the surface resistance of the light transmissive conductive substrate and improving the current collection efficiency, wiring made of a conductive material such as highly conductive metal or carbon is separately provided on the light transmissive conductive substrate. It may be provided. Although there is no restriction | limiting in particular in the electrically conductive material used for this wiring, It is desirable that corrosion resistance and oxidation resistance are high, and the leakage current of electrically conductive material itself is low. However, even a conductive material having low corrosion resistance can be used by separately providing a protective layer made of a metal oxide or the like. For the purpose of protecting the wiring from corrosion and the like, the wiring is preferably installed between the light-transmitting conductive substrate and the protective layer.

As a material for the semiconductor electrode layer, various metal oxide semiconductors, compounds having a perovskite structure, and the like can be used. At this time, the material of the metal oxide semiconductor fine particles is preferably an n-type semiconductor material in which conduction band electrons serve as carriers under photoexcitation to generate an anode current. Specific examples of such semiconductor materials include TiO ₂ , ZnO, WO ₃ , Nb ₂ O ₅ , SrTiO ₃ , and SnO ₂ , and among these, anatase TiO ₂ is particularly preferable. However, the material of the metal oxide semiconductor fine particles 2 is not limited to these. Also, two or more of these materials can be mixed and used. Furthermore, the semiconductor fine particles can take various forms such as particles, tubes, and rods as required.

  The thickness of the metal oxide semiconductor porous layer 1 is preferably 1 to 30 μm. When the thickness is less than 1 μm, sufficient photoelectric conversion efficiency cannot be obtained. As the thickness is increased, the photoelectric conversion efficiency is improved. However, when the thickness exceeds 30 μm, the effect of improving the photoelectric conversion efficiency due to the increase in the film thickness becomes poor. Therefore, the thickness is preferably 30 μm or less. The shape of the metal oxide semiconductor fine particles 2 is not particularly limited, and may be a general shape. The metal oxide semiconductor fine particles 2 preferably have an average primary particle diameter of 1 to 100 nm in order to transmit visible light.

  Although there is no restriction | limiting in particular in the particle size of semiconductor fine particle, 1-200 nm is preferable at the average particle diameter of a primary particle, Most preferably, it is 5-100 nm. It is also possible to improve the quantum yield by mixing semiconductor fine particles having an average particle size larger than the average particle size into semiconductor fine particles having an average particle size and scattering incident light by the semiconductor fine particles having a large average particle size. is there. In this case, the average particle diameter of the semiconductor fine particles to be mixed separately is preferably 20 to 500 nm.

  There are no particular restrictions on the method for producing the porous semiconductor layer comprising semiconductor fine particles, but in view of physical properties, convenience, production costs, etc., a wet film-forming method is preferred, and the semiconductor fine particle powder or sol is mixed with water or an organic solvent. It is preferable to prepare a paste uniformly dispersed in a solvent such as, and to apply a coating liquid layer on a light-transmitting conductive substrate. There is no restriction | limiting in particular in the method, For example, it can carry out by the well-known method, for example, the apply | coating method or the printing method. As a coating method, for example, a dip method, a spray coating method, a wire bar coating method, a spin coating method, a roller coating method, a blade coating method, a gravure coating method, and as a wet printing method, for example, a relief printing method, an offset printing method, It can be performed by a printing method, a gravure printing method, an intaglio printing method, a rubber plate printing method, a screen printing method, or the like. When crystalline titanium oxide is used as the material of the semiconductor fine particles, the anatase type is preferable from the viewpoint of photocatalytic activity. The anatase-type titanium oxide may be a commercially available powder, sol, or slurry, or may be made with a predetermined particle size by a known method such as hydrolysis of titanium oxide alkoxide. When using a commercially available powder, it is preferable to eliminate secondary agglomeration of the particles, and it is preferable to disperse the particles using a mortar, ball mill, ultrasonic dispersion device or the like when preparing the coating solution. At this time, acetylacetone, hydrochloric acid, nitric acid, a surfactant, a chelating agent, or the like can be added in order to prevent the particles after the secondary aggregation from being aggregated again. For the purpose of thickening, various thickeners such as polymers such as polyethylene oxide and polyvinyl alcohol, and cellulose-based thickeners can be added.

  The porous semiconductor layer made of semiconductor fine particles, in other words, the semiconductor fine particle layer preferably has a large surface area so that a large amount of photosensitizing dye can be adsorbed. For this reason, the surface area of the semiconductor fine particle layer coated on the substrate is preferably 10 times or more, more preferably 100 times or more the projected area. The upper limit is not particularly limited, but is usually about 1000 times. In general, as the thickness of the semiconductor fine particle layer increases, the amount of the supported dye increases per unit projected area and thus the light capture rate increases. However, the diffusion distance of injected electrons increases and the loss due to charge recombination also increases. . Accordingly, a preferable thickness exists in the semiconductor fine particle layer, but the thickness is generally 0.1 to 100 μm, more preferably 1 to 50 μm, and particularly preferably 3 to 30 μm. . The semiconductor fine particle layer is preferably fired in order to make the particles electronically contact each other after being applied to the substrate and to improve the film strength and the adhesion to the substrate. Although there is no restriction | limiting in particular in the range of baking temperature, Since resistance of a board | substrate will become high if it raises temperature too much and it may fuse | melt, it is usually 40-700 degreeC, More preferably, it is 40-650 degreeC. . The firing time is not particularly limited, but is usually about 10 minutes to 10 hours. After firing, for the purpose of increasing the surface area of the semiconductor fine particle layer or increasing the necking between the semiconductor fine particles, for example, chemical plating using a titanium tetrachloride aqueous solution or necking treatment using a titanium trichloride aqueous solution or a diameter of 10 nm or less. A dip treatment of the semiconductor ultrafine particle sol may be performed. In the case where a plastic substrate is used as the light-transmitting conductive substrate, it is possible to apply a paste containing a binder onto the substrate and perform pressure bonding to the substrate by a heating press.

  The photosensitizing dye to be held in the porous semiconductor layer is not particularly limited as long as it exhibits a sensitizing action. For example, xanthene dyes such as rhodamine B, rose bengal, eosin and erythrosine, merocyanine, quinocyanine, Cyanine dyes such as cryptocyanine, basic dyes such as phenosafranine, fog blue, thiocin and methylene blue, other azo dyes, porphyrin compounds such as chlorophyll, zinc porphyrin and magnesium porphyrin, phthalocyanine compounds, coumarin compounds, ruthenium Examples include Ru bipyridine complexes, terpyridine complexes, anthraquinone dyes, polycyclic quinone dyes, and squarylium dyes. Among them, a ruthenium Ru bipyridine complex whose ligand has a pyridine ring has a high quantum yield and is preferable as a photosensitizing dye. However, the photosensitizing dye is not limited to this, and can be used alone or in combination of two or more.

  The method for adsorbing the photosensitizing dye to the porous semiconductor layer is not particularly limited, but the above-described photosensitizing dye is, for example, alcohols, nitriles, nitromethane, halogenated hydrocarbons, ethers, dimethyl sulfoxide, amides, N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters, carbonates, ketones, hydrocarbons, water, and other solvents can be dissolved in the porous semiconductor layer. The dye solution can be applied onto the porous semiconductor layer. In addition, when a dye having high acidity is used, deoxycholic acid or the like may be added for the purpose of reducing association between the dye molecules.

  After adsorbing the photosensitizing dye, the surface of the porous semiconductor layer may be treated with amines for the purpose of promoting the removal of the excessively adsorbed dye. Examples of amines include pyridine, 4-tert-butylpyridine, polyvinylpyridine, and the like. When these are liquid, they may be used as they are, or may be used after being dissolved in an organic solvent.

As the electrolyte layer 4, an electrolytic solution, or a gel or solid electrolyte can be used. Examples of the electrolyte include a solution containing a redox system (redox _couple ). Specifically, a combination of iodine I ₂ and a metal iodide salt or an organic iodide salt, bromine Br ₂ and a metal bromide salt or an organic salt. A combination with a bromide salt is used. In addition, metal complexes such as ferrocyanate / ferricyanate and ferrocene / ferricinium ions, sulfur compounds such as sodium polysulfide and alkylthiol / alkyl disulfide, viologen dyes, hydroquinone / quinone, and the like can be used. The cations constituting the metal compound are lithium Li ⁺ , sodium Na ⁺ , potassium K ⁺ , cesium Cs ⁺ , magnesium Mg ²⁺ , calcium Ca ²⁺ , and the cation constituting the organic compound is a tetraalkyl. Quaternary ammonium ions such as ammonium ions, pyridinium ions, and imidazolium ions are suitable, but are not limited to these, and can be used alone or in admixture of two or more.

Among these, an electrolyte combining iodine I ₂ and a quaternary ammonium compound such as lithium iodide LiI, sodium iodide NaI, or imidazolium iodide is particularly preferable. The concentration of the electrolyte salt in the electrolytic solution is preferably 0.05M to 5M, more preferably 0.2M to 3M. The concentration of iodine I ₂ or bromine Br ₂ is preferably 0.0005M to 1M, and more preferably 0.001 to 0.3M.

  Solvents that make up the electrolyte include water, alcohols, ethers, esters, carbonates, lactones, carboxylic esters, phosphate triesters, heterocyclic compounds, nitriles, ketones, amides , Nitromethane, halogenated hydrocarbons, dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, and hydrocarbons, but are not limited thereto, It can be used alone or in admixture of two or more. Moreover, it is also possible to use a room temperature ionic liquid of a tetraalkyl, pyridinium, or imidazolium quaternary ammonium salt as a solvent.

  Any material can be used as the counter electrode as long as it is a conductive material, but even an insulating material can be used if a conductive catalyst layer is provided on the side facing the porous semiconductor layer. Is possible. However, it is preferable to use an electrochemically stable material as the material of the counter electrode, and specifically, platinum, gold, carbon, a conductive polymer, or the like is preferably used. For the purpose of improving the catalytic effect of redox, it is preferable that the side facing the porous semiconductor layer has a fine structure and has a large surface area. If it exists, it is desired to be in a porous state. The platinum black state can be formed by a method of anodizing platinum, a reduction treatment of a platinum compound, or the like, and the porous carbon can be formed by a method such as sintering of carbon fine particles or firing of an organic polymer. Moreover, it can also be used as a light-transmitting counter electrode by wiring a metal having a high redox catalyst effect such as platinum on a light-transmitting conductive substrate, or by reducing the surface of a platinum compound.

  When the dye-sensitized photoelectric conversion device has a so-called monolithic structure laminated on one light transmissive substrate and is provided with a porous insulating layer, the material is not particularly limited as long as the material does not have conductivity. In particular, zirconia, alumina, titania and silica are suitable. The porous insulating layer is composed of these oxide particles, and the porosity is preferably 10% or more. Although there is no restriction | limiting in the upper limit of a porosity, Usually, about 10 to 80% is preferable from a viewpoint of the physical strength of an insulating layer. When the porosity is 10% or less, the diffusion of the electrolyte is affected, and the cell characteristics are remarkably deteriorated. The pore diameter is preferably 1 to 1000 nm. When the thickness is 1 nm or less, the diffusion of the electrolyte and the impregnation of the dye are affected, and the cell characteristics are deteriorated. Furthermore, if the thickness is 1000 nm or more, the catalyst particles of the catalyst electrode layer enter the insulating layer, which may cause a short circuit. Although there is no restriction | limiting in the manufacturing method of this porous insulating layer, It is preferable that it is the sintered compact of the said oxide particle.

  The production method of the dye-sensitized photoelectric conversion device is not particularly limited. For example, the electrolyte composition can be liquid or gelled inside the photoelectric conversion device, and in the case of a liquid electrolyte composition before introduction, it is porous. The semiconductor layer and the counter electrode face each other, and the substrate portion on which the porous semiconductor layer is not formed is sealed so that these electrodes do not contact each other. At this time, although there is no restriction | limiting in particular in the magnitude | size of the clearance gap between a porous semiconductor layer and a counter electrode, Usually, it is 1-100 micrometers, More preferably, it is 1-50 micrometers. If the distance between the electrodes is too long, the photocurrent decreases due to the decrease in conductivity. The sealing method is not particularly limited, but it is preferable to use a material having light resistance, insulation, and moisture resistance. Epoxy resin, ultraviolet curable resin, acrylic adhesive, EVA (ethylene vinyl acetate), ionomer resin, ceramic Various heat-sealing films can be used, and various welding methods can be used. The method for injecting the electrolyte composition solution is not particularly limited, but a method in which the outer periphery is sealed in advance and the solution is injected under reduced pressure inside the cell in which the solution inlet is opened is preferable. In this case, a method of dropping a few drops of the solution at the injection port and injecting the solution by capillary action is simple. In addition, the injection operation can be performed under reduced pressure or under heating as necessary. After the solution is completely injected, the solution remaining at the inlet is removed and the inlet is sealed. Although there is no restriction | limiting in particular also in this sealing method, If necessary, it can also seal by affixing a glass plate or a plastic substrate with a sealing agent. In addition to this method, an electrolytic solution can be dropped on a substrate and bonded together under reduced pressure as in a liquid crystal drop injection (ODF: One Drop Filling) process of a liquid crystal panel. In the case of a gel electrolyte using a polymer or the like, or an all solid electrolyte, a polymer solution containing an electrolyte composition and a plasticizer is volatilized and removed by a casting method on the porous semiconductor layer. After completely removing the plasticizer, sealing is performed in the same manner as in the above method. This sealing is preferably performed using a vacuum sealer or the like under an inert gas atmosphere or under reduced pressure. After sealing, in order to fully immerse the electrolyte in the porous semiconductor layer, it is possible to perform heating and pressurizing operations as necessary.

  The dye-sensitized photoelectric conversion device can be produced in various shapes depending on the application, and the shape is not particularly limited. The dye-sensitized photoelectric conversion device is most typically configured as a dye-sensitized solar cell. However, the dye-sensitized photoelectric conversion device may be other than a dye-sensitized solar cell, for example, a dye-sensitized photosensor. Electronic devices may be basically any type, including both portable and stationary types, but specific examples include mobile phones, mobile devices, robots, personal computers. , In-vehicle equipment, various home appliances. In this case, the dye-sensitized photoelectric conversion device is, for example, a dye-sensitized solar cell used as a power source for these electronic devices.

[Embodiment 2]
In Embodiment 2, an example suitable as a dye-sensitized solar cell will be described as an example of the dye-sensitized photoelectric conversion device described in claims 8 to 10.

  FIG. 3 is a schematic diagram showing a cross-sectional structure of the dye-sensitized photoelectric conversion device 30 according to the second embodiment of the present invention. The dye-sensitized photoelectric conversion device 30 mainly includes a light-transmitting substrate 1, a light-transmitting conductive layer (negative electrode current collector) 2, a porous semiconductor layer (negative electrode) 3 holding a photosensitizing dye, an electrolyte layer 4, It is composed of a counter electrode (positive electrode) 5, a counter substrate 6, and a sealing material (not shown).

  The dye-sensitized photoelectric conversion device 30 is different from the dye-sensitized photoelectric conversion device 10 in that instead of the high refractive index fine particles 14 having an anisotropic shape, spherical high refractive index fine particles 21 having a small average particle diameter, and average particles This is the point that the transmitted light is efficiently scattered using the spherical high refractive index fine particles 22 having a large diameter. Other than this, the second embodiment is the same as the first embodiment.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples. In this example, the dye-sensitized photoelectric conversion device 10 (see FIG. 1) described in the embodiment was manufactured and its performance was evaluated.

<Preparation of dye-sensitized photoelectric conversion device>
(1) As the light-transmissive substrate 1 and the light-transmissive conductive layer 2, a conductive glass substrate with an FTO layer for amorphous solar cells (manufactured by Nippon Sheet Glass Co., Ltd., sheet resistance 10Ω / □, thickness 1.1 mm) Used, processed into a rectangle of 15 mm length × 25 mm width. The conductive glass substrate was subjected to ultrasonic cleaning using acetone, alcohol, an alkaline cleaning liquid, and ultrapure water in this order as a cleaning solvent, and then sufficiently dried. Of this conductive glass substrate, a region from one end in the horizontal direction to 10 mm is used as an electrode lead portion, and the porous semiconductor layer 3 is formed in the remaining square region of 15 mm in length × 15 mm in width.

  (2) Next, a titanium oxide fine particle paste layer having a diameter of 5 mm and a thickness of 20 μm was formed on the FTO layer in the square area of the conductive glass substrates 1 and 2. At this time, a transparent Ti-Nanoxide TSP paste (trade name; manufactured by Solaronix) is first formed on the FTO layer with a thickness of 7 μm using a screen printer and a circular screen mask, and then Ti containing scattering particles is formed. A -Nanoxide DSP paste (trade name; manufactured by Solaronix) layer was laminated to a thickness of 13 μm to form a titanium oxide fine particle paste layer having a total thickness of 20 μm.

(3) Next, using an electric furnace, the titanium oxide paste layer was baked at 500 ° C. for 30 minutes to produce a titanium oxide porous layer. After being allowed to cool, the titanium oxide porous layer was immersed in a 0.1 mol / L titanium tetrachloride TiO ₄ aqueous solution and kept at 70 ° C. for 30 minutes. Next, the titanium oxide porous layer was sufficiently washed with pure water and ethanol and dried. Thereafter, the porous titanium oxide layer was fired again at 500 ° C. for 30 minutes using an electric furnace. In these steps, the following formula: TiCl ₄ + 2H ₂ O → TiO ₂ + 4HCl
The necking between the titanium oxide fine particles in the titanium oxide porous layer is strengthened by the generated titanium oxide. Next, the excimer lamp was used to irradiate the titanium oxide porous layer with ultraviolet light for 3 minutes to perform a treatment for increasing the activity of the titanium oxide porous layer. At this time, impurities such as organic substances contained in the titanium oxide porous layer are oxidatively decomposed and removed by the catalytic action of titanium oxide.

(4) Next, the titanium oxide porous layer was immersed in a Z907 dye solution at room temperature for 24 hours to adsorb the photosensitizing dye Z907 to the titanium oxide porous layer. Z907 is cis-bis (isothiocyanato) (H ₂ dcbpy) (dnbpy) ruthenium complex (where H ₂ dcbpy is 4,4′-dicarboxy-2,2′-bipyridine and dnbpy is 4,4 ′ -Dinonyl-2,2'-bipyridine). As the dye solution, a solution in which Z907 was dissolved at a concentration of 0.5 mM in a mixed solvent in which tert-butyl alcohol and acetonitrile were mixed at a volume ratio of 1: 1 was used. Next, after the titanium oxide porous layer was washed with acetonitrile, acetonitrile was evaporated in the dark and the titanium oxide porous layer was dried. As a result, the porous semiconductor layer 3 on which the photosensitizing dye was adsorbed was obtained.

(5) Next, 1.65 g (1 mol / L) of 1,3-dimethyl-3-imidazolium iodide, 0.28 g of iodine I ₂ (0.15 mol / L), 0.64 g of N-butyl-benzimidazole (0.5 mol / L) and 0.09 g (0.1 mol / L) of guanidine thiocyanate were dissolved in 7.35 g of 3-methoxypropionitrile to prepare a liquid electrolyte composition (in the above ()). The concentration is the molar concentration of each component in the electrolyte composition.) After adding 0.16 g of silica fine particles R805 (trade name; manufactured by Nippon Aerosil Co., Ltd.) having a hydrophobic surface as a gelling agent to 1.84 g of the obtained electrolyte composition, a mixer (THINKY Corporation) was added. The gel electrolyte solution was prepared by thoroughly stirring the mixture. The mass ratio in the gel electrolyte is
Liquid electrolyte composition: silica fine particles R805 = 92: 8
It is.

(6) Next, acicular titanium oxide fine particles FTL100 (trade name; manufactured by Ishihara Sangyo Co., Ltd.) were added to the gel electrolyte as highly refractive fine particles to prepare a light scattering gel electrolyte. The mass ratio in the light-scattering gel electrolyte is: gel electrolyte: titanium oxide fine particles FTL100 = 95: 5
It is. This light-scattering gel electrolyte was applied to the porous semiconductor layer 3 on the conductive glass substrates 1 and 2.

  (7) On the other hand, as the counter substrate 6, similarly to the light transmissive substrate 1 and the light transmissive conductive layer 2 described above, a conductive glass substrate with an FTO layer for amorphous solar cells (manufactured by Nippon Sheet Glass Co., Ltd., sheet resistance 10Ω) / □, thickness 1.1 mm) was processed into a rectangle of 15 mm length × 25 mm width. Of this conductive glass substrate, a region from one end in the horizontal direction to 10 mm was used as the electrode lead-out portion. A counter electrode 5 was formed by sequentially laminating a chromium Cr layer having a thickness of 50 nm and a platinum Pt layer having a thickness of 100 nm on the remaining FTO layer having a square area of 15 mm in length and 15 mm in width by a sputtering method. .

  (8) Next, using a dispenser, an ultraviolet (UV) curable adhesive is applied onto the conductive glass substrates 1 and 2 so as to be cured at a width of 2 mm from the outer periphery to the inner region of the square region. It was. Thereafter, the square regions of the conductive glass substrates 1 and 2 and the counter substrate 6 were opposed to each other and bonded so that the porous semiconductor layer 3 and the counter electrode 5 face each other. The counter substrate 6 is provided with a hole having a diameter of 0.5 mm, and this hole functions as an air escape path for bonding.

  (9) Next, after the holes provided in the counter substrate 6 are filled with an ultraviolet (UV) curable adhesive and sealed, the ultraviolet (UV) is irradiated to cure the ultraviolet (UV) curable adhesive. Then, a dye-sensitized photoelectric conversion device was produced.

The mass ratio in the light-scattering gel electrolyte is expressed as follows: Gel electrolyte: FTL100 = 90: 10
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

The mass ratio in the light-scattering gel electrolyte solution is defined as gel electrolyte solution: FTL100 = 80: 20
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

The mass ratio in the light-scattering gel electrolyte is gel electrolyte: FTL100 = 70: 30
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

Using acicular titanium oxide fine particles FTL200 (trade name; manufactured by Ishihara Sangyo Co., Ltd.) as the high refractive fine particles, the mass ratio in the light-scattering gel electrolyte is gel electrolyte: titanium oxide fine particles FTL200 = 80: 20
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

As in Example 3, acicular titanium oxide fine particles FTL100 were used as the high refractive fine particles, and the mass ratio in the light-scattering gel electrolyte was determined as follows: Gel electrolyte: titanium oxide fine particles FTL100 = 80: 20
As a result, a dye-sensitized photoelectric conversion device was produced. However, a photosensitizing dye having a slightly different structure from Z907 was used as the photosensitizing dye.

[Comparative Example 1]
The gel electrolyte was used as an electrolyte as it was without adding highly refractive fine particles. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

[Comparative Example 2]
Acicular calcium carbonate fine particles Whiscal (trade name; manufactured by Maruo Calcium Co., Ltd.) are used as the high refractive fine particles, and the mass ratio in the light-scattering gel electrolyte is determined as follows: Gel electrolyte: calcium carbonate fine particles Whiscal = 80: 20
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

[Comparative Example 3]
As in Example 6, a photosensitizing dye having a slightly different structure from Z907 was used as the photosensitizing dye. Except this, it carried out similarly to the comparative example 1, and produced the dye-sensitized photoelectric conversion apparatus.

[Comparative Example 4]
Spherical titanium oxide fine particles ST01 (trade name; manufactured by Ishihara Sangyo Co., Ltd.) are used as the high refractive fine particles, and the mass ratio in the light-scattering gel electrolyte is gel electrolyte: titanium oxide fine particles ST01 = 80: 20
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 6.

[Comparative Example 5]
Spherical titanium oxide fine particles P25 (trade name; manufactured by Nippon Aerosil Co., Ltd.) are used as the high refractive fine particles, and the mass ratio in the light-scattering gel electrolyte is determined as follows: Gel electrolyte: titanium oxide fine particles P25 = 80: 20
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 6.

[Comparative Example 6]
Spherical titanium oxide fine particles PT501A (trade name; manufactured by Ishihara Sangyo Co., Ltd.) are used as the high refractive fine particles, and the mass ratio in the light scattering gel electrolyte is gel electrolyte: titanium oxide fine particles PT501A = 80: 20.
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 6.

[Comparative Example 7]
Spherical titanium oxide fine particles ST41 (trade name; manufactured by Ishihara Sangyo Co., Ltd.) are used as the high refractive fine particles, and the mass ratio in the light-scattering gel electrolyte is gel electrolyte: titanium oxide fine particles ST41 = 80: 20
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 6.

[Comparative Example 8]
Spherical titanium oxide fine particles TA300 (trade name; manufactured by Fuji Titanium Industry Co., Ltd.) are used as the high refractive fine particles, and the mass ratio in the light-scattering gel electrolyte is gel electrolyte: titanium oxide fine particles TA300 = 80: 20
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 6.

[Comparative Example 9]
Spherical titanium oxide fine particles G2 (trade name; manufactured by Showa Titanium Co., Ltd.) are used as the high refractive fine particles, and the mass ratio in the light-scattering gel electrolyte is gel electrolyte: titanium oxide fine particles G2 = 80: 20
It was. Except for this, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 6.

Table 2 is a table showing characteristics of the high refractive fine particles used in Examples 1 to 6 and Comparative Examples 2 and 4 to 9.

<Evaluation of dye-sensitized photoelectric conversion device>
While irradiating pseudo sunlight (AM1.5,100mW / cm ²⁾ using a circular mask 0.188Cm ^2, short-circuit current of the dye-sensitized photoelectric conversion device was produced, the open voltage, fill factor, and photoelectric conversion efficiency Was evaluated at 24 ° C.

Table 3 is a table | surface which shows the characteristic of the dye-sensitized photoelectric conversion apparatus produced in Examples 1-5 and Comparative Examples 1 and 2. FIG.

Table 4 is a table | surface which shows the characteristic of the dye-sensitized photoelectric conversion apparatus produced in Example 6 and Comparative Examples 3-9 contrasted with this. In the table, the example with two lines shows the results of two experiments.

  From the comparison of the photoelectric conversion efficiency between Comparative Example 1 and Examples 1 to 5 and the comparison of the conversion efficiency between Comparative Example 3 and Comparative Examples 4 to 9, the fine particles added to the electrolyte layer are as high as titanium oxide fine particles. It can be seen that the refractive index fine particles have an effect of improving the photoelectric conversion efficiency.

  On the other hand, the comparison between Comparative Example 1 and Comparative Example 2 shows that the conversion efficiency decreases slightly when calcium carbonate fine particles are added. This is presumably because the loss due to the increase in the internal resistance of the electrolyte layer due to the addition of the calcium carbonate fine particles is larger than the effect of scattering the transmitted light if the refractive index is about the same as calcium carbonate. However, since the reduction in conversion efficiency is slight, if the fine particles have a refractive index slightly larger than the refractive index of calcium carbonate, the effect of scattering the transmitted light by adding the fine particles is greater in the internal resistance of the electrolyte layer. It is expected to outweigh the losses from the increase. Since the refractive index of calcium carbonate in the minor axis direction is about 1.68, the refractive index required for the high refractive index fine particles is expected to be about 1.75 to 1.8, which is a little larger than that. Since the refractive index of the electrolyte solution is about 1.45 to 1.5, it can be seen that the high refractive index fine particles only need to have a refractive index that is about 0.3 larger than the refractive index of the electrolyte solution.

  From the comparison between Examples 1 to 4, when the addition rate of the high refractive index fine particles is up to 20% by mass, the photoelectric conversion efficiency improves as the addition rate increases, but when the addition rate reaches 30% by mass, the addition rate increases. It turns out that conversion efficiency falls a little compared with the case where it is 20 mass%. This is because, since the addition rate exceeds 20% by mass, the effect of scattering the transmitted light by the addition of the fine particles reaches a peak, and the loss due to the increase in the internal resistance of the electrolyte layer by the addition of the fine particles is exceeded. Conceivable.

  4 and 5 are a graph showing current-voltage characteristics and a graph showing photoelectric conversion efficiency of the dye-sensitized photoelectric conversion devices according to Example 6 and Comparative Examples 3 to 9 of the present invention, respectively. In these examples, the same photosensitizing dye is used, and the addition rate of the high refractive index fine particles is the same as 20% by mass, so the photoelectric conversion efficiency is directly compared to examine the effect of the high refractive index fine particles. Can do. From FIG. 5, in Comparative Examples 4 to 9, in which the high refractive index fine particles are spherical fine particles having one kind of average particle diameter, the photoelectric conversion is performed when the average particle diameter is larger than 0.2 μm and in the vicinity of 0.39 μm. It turns out that the efficiency is the best. Further, as shown in FIG. 5, in Example 6 using needle-shaped fine particles FTL100 (trade name; manufactured by Ishihara Sangyo Co., Ltd.) having a major axis of 1.68 μm and a minor axis of 0.13 μm as the high refractive index fine particles. The photoelectric conversion efficiency higher than any of Comparative Examples 4 to 9 was obtained. As described above, the high refractive index fine particles having an anisotropic shape change the effective particle diameter with respect to the transmitted light according to the change in the orientation direction, so the high refractive index fine particles with one kind of particle diameter. This is considered to be because the transmitted light can be scattered efficiently.

  Referring to the empirical formula for the optimum particle diameter Dopt described in the first embodiment and the results of Comparative Examples 3 to 9, it has an anisotropic shape in order to efficiently scatter all the transmitted light having a wavelength of 400 to 800 nm. It can be concluded that the average major axis of the high refractive index fine particles is 0.3 μm or more, and the ratio of the major axis to the minor axis is preferably 2 or more.

  Although the present invention has been described based on the embodiments and examples, it is needless to say that the present invention is not limited to these examples and can be appropriately changed without departing from the gist of the invention. .

  The present invention provides a dye-sensitized photoelectric conversion device such as a dye-sensitized solar cell with good light utilization efficiency, and contributes to its popularization.

DESCRIPTION OF SYMBOLS 1 ... Light transmissive board | substrate, 2 ... Light transmissive conductive layer (negative electrode collector),
3 ... Semiconductor electrode layer (negative electrode) holding photosensitizing dye, 3a ... Transmission layer, 3b ... Scattering layer,
4 ... electrolyte layer, 5 ... counter electrode (positive electrode), 6 ... counter substrate, 10 ... photosensitized solar cell,
11 ... Semiconductor fine particles having a small average particle diameter, 12 ... Semiconductor fine particles having a large average particle diameter,
13 ... Photosensitizing dye, 14 ... High refractive index fine particles having anisotropic shape, 15 ... Spherical fine particles,
DESCRIPTION OF SYMBOLS 100 ... Photosensitized solar cell, 101 ... Transparent substrate, 102 ... Transparent conductive layer (negative electrode collector),
103 ... Semiconductor electrode layer (negative electrode) holding a photosensitizing dye, 104 ... Electrolyte layer,
105 ... Counter electrode (positive electrode), 106 ... Counter substrate, 200 ... Photosensitized solar cell,
201 ... Glass substrate, 203 ... Semiconductor electrode layer (negative electrode), 204 ... Electrolyte part,
205 ... Counter electrode (positive electrode), 206 ... Electrode (negative electrode current collector)

Japanese Patent Laid-Open No. 10-255863 (claims 1, 2 and 11, page 3, FIG. 1)

Sumitomo Osaka Cement Co., Ltd., Technical Report 2005, Titanium oxide for dye-sensitized solar cells, p.36-40

Claims (13)

In order from the light incident side, at least,
A light transmissive substrate;
A light transmissive conductive layer provided on a surface of the light transmissive support opposite to the light incident side; and
A porous semiconductor layer holding a photosensitizing dye;
High-refractive-index fine particles that are arranged so as to infiltrate the porous semiconductor layer and that are made of a high-refractive-index material having a refractive index that is 0.3 or more larger than that of the electrolytic solution and have an anisotropic shape An electrolyte layer containing,
A dye-sensitized photoelectric conversion device in which a counter electrode is disposed.   2. The dye-sensitized photoelectric conversion device according to claim 1, wherein the high refractive index fine particles have a refractive index of 1.7 or more and an average major axis of 0.3 μm or more.   The dye-sensitized photoelectric conversion device according to claim 1, wherein a ratio of a major axis to a minor axis of the high refractive index fine particles is 2 or more.   The dye-sensitized photoelectric conversion device according to claim 1, wherein the anisotropic shape is a needle shape, a rod shape, a spindle shape, an ellipsoid shape, or a capsule shape.   2. The dye-sensitized photoelectric conversion device according to claim 1, wherein spherical or granular fine particles having a ratio of a major axis to a minor axis of less than 2 are further contained in the electrolyte layer.   The dye-sensitized photoelectric conversion device according to claim 5, wherein the spherical or granular fine particles are made of a high refractive index material having a refractive index of 0.3 or more larger than that of the electrolytic solution.   The dye-sensitized photoelectric conversion device according to claim 5, wherein an average particle diameter of the spherical or granular fine particles is not less than a short diameter and not more than a long diameter of the high refractive index fine particles. In order from the light incident side, at least,
A light transmissive substrate;
A light transmissive conductive layer provided on a surface of the light transmissive support opposite to the light incident side; and
A porous semiconductor layer holding a photosensitizing dye;
The electrolyte solution is arranged so as to infiltrate the porous semiconductor layer. In addition, the electrolyte solution is made of a high refractive index material having a refractive index of 0.3 or more larger than that of the electrolyte solution, and has two or more types of spherical shapes having different average particle diameters. An electrolyte layer containing fine particles of high refractive index;
A dye-sensitized photoelectric conversion device in which a counter electrode is disposed.   The dye-sensitized photoelectric conversion device according to claim 8, wherein the refractive index of the high refractive index fine particles is 1.7 or more.   9. The dye-sensitized photoelectric conversion device according to claim 8, wherein at least two kinds of the spherical high refractive index fine particles different in the average particle diameter by a maximum of 2 times are added. The dye-sensitized photoelectric conversion device according to claim 1 or 8, wherein the high refractive index fine particles are titanium oxide TiO ₂ fine particles.   The dye-sensitized photoelectric conversion device according to claim 1 or 8, wherein a content of the high refractive index fine particles in the electrolyte layer is 1 to 50% by mass.   The dye-sensitized photoelectric conversion device according to claim 1 or 8, wherein the electrolyte layer contains a gelling agent.