JP5644588B2 - Dye-sensitized photoelectric conversion device, manufacturing method thereof, and electronic apparatus - Google Patents

Description

  The present disclosure relates to a dye-sensitized photoelectric conversion device, a method for manufacturing the same, and an electronic apparatus. For example, the dye-sensitized photoelectric conversion device suitable for use in a dye-sensitized solar cell, a method for manufacturing the same, and the dye-sensitized photoelectric conversion device are used. It relates to electronic equipment.

Solar cells, which are photoelectric conversion devices that convert sunlight into electrical energy, use sunlight as an energy source, and therefore have very little influence on the global environment, and are expected to become more widespread.
Conventionally, crystalline silicon solar cells using single crystal or polycrystalline silicon and amorphous silicon solar cells are mainly used as solar cells.

  On the other hand, the dye-sensitized solar cell proposed by Gretzell et al. In 1991 can obtain high photoelectric conversion efficiency, and unlike a conventional silicon-based solar cell, it does not require a large-scale device for production, and has a low It is attracting attention because it can be manufactured at low cost (for example, see Non-Patent Document 1).

  FIG. 11 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 102, a porous photoelectrode 103 holding a photosensitizing dye, an electrolyte layer 104, a counter electrode 105, an electrode substrate 106, and an illustration omitted. It is composed of a sealing material or the like.

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 porous photoelectrode 103 that is a negative electrode is provided in contact with the transparent conductive layer 102. As the porous photoelectrode 103, a porous semiconductor 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 semiconductor constituting the porous photoelectrode 103. As the electrolyte layer 104, an electrolytic solution containing a redox species (redox pair) or the like is used. The counter electrode 105 that is a positive electrode is formed of a platinum layer or the like, and is provided on the electrode 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 this light absorption is taken out to the porous photoelectrode 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 photoelectric conversion device having the transparent conductive layer 102 and the porous photoelectrode 103 as a negative electrode and the counter electrode 105 as a positive electrode.

  Unlike the conventional silicon-based solar cell, the production of the dye-sensitized solar cell does not require a vacuum processing step, and thus does not require a large-scale apparatus. In addition, there is an advantage in that an inexpensive oxide semiconductor such as titanium oxide can be used to manufacture with few steps and high productivity. In addition, there are various photosensitizing dyes that can absorb light in a wide wavelength range centered on the visible light region, so the wavelength of light to be absorbed can be selected by selecting the photosensitizing dye that is bound to the porous photoelectrode. The advantage is that light in a wide wavelength region can be used by combining a plurality of photosensitizing dyes and bonding them to a porous photoelectrode. 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 photoelectric conversion device.

  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. As one form, in order to prevent the light transmitted through the porous photoelectrode 103 from being absorbed by the electrolyte layer 104 and the counter electrode 105, the porous photoelectrode 103 has a light scattering function to improve the utilization rate of incident light. Technology for improving the photoelectric conversion efficiency is known.

  For example, Patent Document 1 includes 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 portion 204, and a counter electrode 205 as shown in FIG. A dye-sensitized solar cell 200 has been proposed.

The electrode 206 of the dye-sensitized solar cell 200 is made of a metal formed in a lattice shape or a plurality of strips, and the high refractive material thin film 207 is a thin film of a high refractive index material such as titanium oxide (rutile). 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 (TiO ₂ ) fine particles (rutile), the particle diameter is about 200 to 500 nm, and the thickness of the light reflecting particle layer 208 is about 5 to 10 μm. Is preferred. 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 diameter 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 incident 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 even if the light reflected by the light-reflecting particle layer 208 and returned to the light-absorbing particle layer 203 passes through the light-absorbing particle layer 203 again, this reflected light is reflected. Most of the light is totally reflected by the high refractive material thin film 207 and returned to the light absorbing particle layer 203 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-material thin film 207, whereby the light-absorbing particle layer It is confined in 203. For this reason, even if the light-absorbing particle layer 203 is thinned, incident light is effectively absorbed by the photosensitizing dye. The photoelectric 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. The high refractive material particles 218 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 203 instead of the light absorbing particle layer 203 and the light reflecting particle layer 208 having a laminated structure. For example, in Non-Patent Document 2, 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-like high-purity titanium oxide fine particles are added. Thus, an example in which a photoelectric conversion efficiency of 10% can be achieved is shown.

Japanese Patent Laid-Open No. 10-255863

Nature, 353, p.737-740,1991 Sumitomo Osaka Cement Co., Ltd., Technical Report 2005, Titanium oxide for dye-sensitized solar cells, p.36-40

  However, in the conventional general dye-sensitized solar cell 100, the method of increasing the thickness of the porous photoelectrode 103 increases the actual surface area, and the amount of photosensitizing dye that can be held in the unit projected area is increased. However, when the thickness of the porous photoelectrode 103 is increased, electrons transferred from the photosensitizing dye to the porous photoelectrode 103 are transferred to the transparent conductive layer 102. Since the diffusion distance increases until reaching the value, the loss of electrons due to charge recombination in the porous photoelectrode 103 also increases, and the internal resistance increases. Therefore, there is an optimum thickness for the porous photoelectrode 103, and the photoelectric conversion characteristics of the dye-sensitized photoelectric conversion device as a whole cannot be improved only by adjusting the thickness of the porous photoelectrode 103.

  Further, for the purpose of actively scattering light using the high refractive material particles 218 having a large particle diameter, a light reflecting particle layer 208 is formed as in Patent Document 1, or porous as in Non-Patent Document 2. To improve the light utilization rate by reducing the incident light that passes through the porous photoelectrode by mixing hexagonal star-like high-purity titanium oxide fine particles in the oxide fine particle layer constituting the porous photoelectrode Then, although the utilization factor of incident light increases, if the thickness of the light reflecting particle layer 208 or the light absorbing particle layer 203 is excessively increased, the internal resistance increases as described above, and thus the light is transmitted by this method. Even if the incident light is reduced, the photoelectric conversion characteristics as a whole are not improved.

Therefore, the problem to be solved by the present disclosure is that the incident light once transmitted through the porous photoelectrode can be reused without increasing the thickness of the porous photoelectrode more than necessary. It is to provide a dye-sensitized photoelectric conversion device such as a dye-sensitized solar cell that can obtain excellent photoelectric conversion characteristics by increasing the utilization factor of light, and a method for producing the same.
Another problem to be solved by the present disclosure is to provide a high-performance electronic device using the above-described excellent dye-sensitized photoelectric conversion device.

That is, in order to solve the above problems, the present disclosure
It has a structure in which an electrolyte layer is filled between a porous photoelectrode adsorbed with a photosensitizing dye and a counter electrode,
In the dye sensitized photoelectric conversion device, the electrolyte layer includes light scattering particles provided with a photosensitizing dye adsorption preventing layer on at least a part of a surface thereof.

In addition, this disclosure
Manufacture of a dye-sensitized photoelectric conversion device having a step of containing light scattering particles in which a photosensitizing dye adsorption preventing layer is formed on at least a part of the surface in an electrolyte layer filled between a porous photoelectrode and a counter electrode Is the method.

In addition, this disclosure
Having at least one photoelectric conversion device;
The photoelectric conversion device is
It has a structure in which an electrolyte layer is filled between the porous photoelectrode and the counter electrode,
The electronic device is a dye-sensitized photoelectric conversion device in which the electrolyte layer includes light scattering particles having a photosensitizing dye adsorption preventing layer provided on at least a part of a surface thereof.

In the present disclosure, as the porous photoelectrode, a porous semiconductor layer obtained by sintering semiconductor fine particles is typically used. The photosensitizing dye is adsorbed on the surface of the semiconductor fine particles constituting the porous semiconductor layer. As a material for the semiconductor fine particles, an elemental semiconductor typified by silicon, a compound semiconductor, a conductor having a perovskite structure, or the like can be used. These semiconductors are preferably n-type semiconductors in which conduction band electrons become carriers under photoexcitation and generate an anode current. Specifically, for example, titanium oxide (TiO ₂ ), zinc oxide (ZnO), tungsten oxide (WO ₃ ), niobium oxide (Nb ₂ O ₅ ), strontium titanate (SrTiO ₃ ), tin oxide (SnO ₂ ), etc. These semiconductors are used. Among these semiconductors, it is desirable to use TiO ₂ , especially anatase TiO ₂ . However, the type of semiconductor is not limited to this, and two or more types of semiconductors can be mixed or combined as needed. Further, the shape of the semiconductor fine particles may be any of granular, needle-like, rod-like, bell-shaped, ellipsoidal, capsule-like, etc., and a plurality of these may be combined to constitute a porous photoelectrode. .

  Although there is no restriction | limiting in particular in the particle size of said 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 forming a light-reflecting particle layer by depositing highly refractive material particles on the surface of the porous photoelectrode facing the counter electrode. The average particle size of the primary particles of the high refractive material particles is preferably about 20 to 500 nm, but is not limited thereto.

  The porous photoelectrode preferably has a large actual surface area including the surface of fine particles facing pores inside the porous photoelectrode made of semiconductor fine particles so that as many photosensitizing dyes can be bonded as possible. For this reason, the surface area of the porous photoelectrode configured to be usable as a dye-sensitized photoelectric conversion device is preferably 10 times or more, and 100 times or more the outer surface area (projected area) of the porous photoelectrode. More preferably. There is no particular upper limit to this ratio, but it is usually about 1000 times.

  If the thickness of the porous photoelectrode is excessively increased, the internal resistance increases as described above, and therefore it is necessary to set the thickness to an appropriate thickness. The optimum thickness of the porous photoelectrode is in the range of 0.1 to 100 μm, preferably in the range of 1 to 50 μm, and particularly preferably in the range of 3 to 30 μm.

  The photosensitizing dye bonded to the porous photoelectrode is not particularly limited as long as it exhibits a sensitizing action, but preferably has an acid functional group adsorbed on the surface of the porous photoelectrode. In general, the photosensitizing dye preferably has a carboxy group, a phosphoric acid group, and the like, and among them, those having a carboxy group are particularly preferable.

  The method for adsorbing the photosensitizing dye to the porous photoelectrode is not particularly limited. For example, alcohols, nitriles, nitromethane, halogenated hydrocarbons, ethers, dimethyl sulfoxide, amides, Dissolve in a solvent such as N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters, carbonates, ketones, hydrocarbons, water, and soak a porous photoelectrode A solution containing a photosensitizing dye can be applied on the porous photoelectrode. Further, deoxycholic acid or the like may be added for the purpose of reducing association between molecules of the photosensitizing dye. If necessary, an ultraviolet absorber can be used in combination.

  After the photosensitizing dye is adsorbed on the porous photoelectrode, the surface of the porous photoelectrode may be treated with amines for the purpose of promoting the removal of the excessively adsorbed photosensitizing 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.

  Any material can be used as the counter electrode material as long as it is a conductive substance, but it can be used if a conductive layer is formed on the side of the insulating material facing the electrolyte layer. It is. As the counter electrode material, an electrochemically stable material is preferably used. Specifically, platinum, gold, carbon, a conductive polymer, or the like is preferably used.

  In order to improve the catalytic action for the reduction reaction at the counter electrode, the surface of the counter electrode in contact with the electrolyte layer is preferably formed so that a fine structure is formed and the actual surface area is increased. For example, the surface of the counter electrode is preferably formed in a platinum black state if platinum, and in a porous carbon state if carbon. Platinum black can be formed by anodization of platinum or chloroplatinic acid treatment, and porous carbon can be formed by a method such as sintering of carbon fine particles or firing of an organic polymer.

  As the constituent of the electrolyte layer, an electrolytic solution, a gel-like or solid electrolyte can be used. Examples of the electrolyte include a solution containing a redox system (redox couple).

  The material of the light scattering particles may be basically any material as long as it has no reactivity with the electrolyte, but the refractive index is 0.3 or more in the visible light region than the electrolyte used. A large highly refractive material is preferred. The material of the light scattering particle is selected as necessary in consideration of the fact that the material having a larger refractive index difference from the electrolyte and having a smaller absorption of light having a wavelength that can be used for photoelectric conversion has a stronger scattered light intensity. It is. Since the refractive index of the electrolyte used generally is about 1.45 to 1.50, the refractive index of the light scattering particles is preferably 1.75 or more, and 1.80 or more. Is more preferred.

  The form of the light scattering particles is typically a spherical shape, but is not limited thereto, and may be an anisotropic shape. Examples of the anisotropic shape include a needle shape, a rod shape, a bell shape, an ellipsoidal shape, and a capsule shape. Particularly, the average major axis is 0.3 μm or more, and the ratio of the major axis to the minor axis is 2 or more. Although it is preferable, it is not limited to this. In addition, a combination of light scattering particles having different shapes, specifically, spherical or granular light scattering particles having a ratio of the major axis to the minor axis of less than 2, and the anisotropic light scattering particles are the same. It is also effective to combine light scattering particles having different particle diameters even with the above-mentioned shape.

  The photosensitizing dye adsorption preventing layer can be formed, for example, by adsorbing the dye to the light scattering particles or encapsulating the light scattering particles with a compound. Various dyes including the above-described photosensitizing dye can be used as the dye, and are selected as necessary. The compound may be an organic compound or an inorganic compound, and is selected as necessary. An example of a compound is a coadsorbent. In particular, when the material of the light scattering particles is an inorganic substance, for example, surface treatment with a methyl imidazolium compound is suitable. Two or more kinds of dyes or compounds can be mixed and used.

  The method of forming the photosensitizing dye adsorption preventing layer may be basically any method, and typically includes adsorption and coating. In addition, for the purpose of increasing the bonding strength and covering power, surface treatment can be performed in combination with two or more steps or two or more types of dyes or compounds.

  The dye-sensitized photoelectric conversion device is most typically configured as a solar cell. However, the dye-sensitized photoelectric conversion device may be other than a solar cell, for example, an optical sensor.

  Electronic devices may be basically any type, including both portable and stationary types, and specifically include mobile phones, mobile devices, robots, personal computers. Vehicle equipment, various household electrical appliances, industrial equipment, and the like. 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.

  In the present disclosure described above, the electrolyte layer of the dye-sensitized photoelectric conversion device includes light scattering particles in which a photosensitizing dye adsorption preventing layer is provided on at least a part of the surface of the high refractive index fine particles. The incident light once transmitted through the porous photoelectrode is scattered on the surface of the light scattering particles so that it returns to the inside of the porous photoelectrode to increase the utilization rate of the incident light. Desorption of the photosensitizing dye bonded to the surface can be effectively suppressed, and deterioration with time of photoelectric conversion characteristics caused by desorption of the photosensitizing dye supported on the porous photoelectrode can be suppressed.

  According to the present disclosure, the incident light once transmitted through the porous photoelectrode can be reused without increasing the thickness of the porous photoelectrode more than necessary. It is possible to realize a dye-sensitized photoelectric conversion device that can obtain high and excellent photoelectric conversion characteristics continuously. By using this excellent dye-sensitized photoelectric conversion device, a high-performance electronic device can be realized.

It is sectional drawing which shows the dye-sensitized photoelectric conversion apparatus which has the electrolyte layer which made the light scattering particle contain in the electrolyte layer of the conventional dye-sensitized photoelectric conversion apparatus. It is the model which shows the external appearance before and behind the acceleration test of the dye-sensitized photoelectric conversion apparatus which has the electrolyte layer which contained the light-scattering particle in the electrolyte layer of the conventional dye-sensitized photoelectric conversion apparatus. It is sectional drawing which shows the mode after the acceleration test of the dye-sensitized photoelectric conversion apparatus which has the electrolyte layer which made light-scattering particle contain in the electrolyte layer of the conventional dye-sensitized photoelectric conversion apparatus. It is sectional drawing which shows the dye-sensitized photoelectric conversion apparatus by 1st Embodiment. It is sectional drawing which shows the dye-sensitized photoelectric conversion apparatus by 2nd Embodiment. It is sectional drawing which shows the dye-sensitized photoelectric conversion apparatus by 3rd Embodiment. It is a basic diagram which shows the result of having measured the current-voltage characteristic of various dye-sensitized photoelectric conversion apparatuses. It is a basic diagram which shows the relationship between the photoelectric conversion efficiency of various dye-sensitized photoelectric conversion apparatuses, and the adsorption amount of a photosensitizing dye. It is a basic diagram which shows the photoelectric conversion efficiency with respect to the elapsed time of various dye-sensitized photoelectric conversion apparatuses. It is sectional drawing which shows the dye-sensitized photoelectric conversion apparatus by 4th Embodiment. It is sectional drawing which shows an example of the conventional common dye-sensitized solar cell. It is sectional drawing which shows the dye-sensitized solar cell described in patent document 1.

  The present inventors have conducted intensive research to solve the above-described problems. In the course of the research, the present inventors in the dye-sensitized photoelectric conversion device, the electrolyte layer as described above using, as light scattering particles, 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 electrolyte layer. When contained in a dispersed state, the incident light once transmitted through the porous photoelectrode is scattered on the surface of the light scattering particles, so that it returns to the porous photoelectrode again. It has been found that the photoelectric conversion characteristics of the dye-sensitized photoelectric conversion device can be improved.

FIG. 1 is a cross-sectional view showing a main part of a dye-sensitized photoelectric conversion device 40 having an electrolyte layer 42 in which light scattering particles 43 are contained in the electrolyte layer 42 of the dye-sensitized photoelectric conversion device 40.
In this dye-sensitized photoelectric conversion device 40, a transparent electrode 32 made of a transparent conductive layer such as FTO (fluorine-doped tin oxide (IV) SnO ₂ ) is provided on one main surface of a transparent substrate 31 such as glass. A porous photoelectrode 34 composed of a porous layer obtained by sintering semiconductor fine particles 33 which are fine particles of titanium oxide (TiO ₂ ) is provided on the transparent electrode 32, and is opposed to the counter electrode 35 of the porous photoelectrode 34. A light reflecting particle layer 37 configured to mix and deposit the semiconductor fine particles 33 and the highly refractive material particles 36 which are fine particles of spherical titanium oxide (TiO ₂ ) is provided on the surface. . One or more kinds of photosensitizing dyes 38 are bonded to the semiconductor fine particles 33 constituting the porous photoelectrode 34 and the light reflecting particle layer 37. On the other hand, a transparent conductive layer 41 is provided on one main surface of the counter substrate 39, and a counter electrode 35 is provided on the transparent conductive layer 41. An electrolyte layer 42 is provided between the light reflecting particle layer 37 configured to be deposited on the porous photoelectrode 34 on the transparent substrate 31 and the counter electrode 35 on the counter substrate 39. The electrolyte layer 42 includes light scattering particles 43 that are spherical titanium oxide (TiO ₂ ) fine particles in a dispersed form. The outer peripheral portions of the transparent substrate 41 and the counter substrate 39 are sealed with a sealing material (not shown).
As shown in FIG. 1, incident light once transmitted through the porous photoelectrode 34 and the light reflecting particle layer 37 is scattered on the surface of the light scattering particles 43, and then returns to the porous photoelectrode 34 again. The utilization factor can be increased, and the photoelectric conversion characteristics of the dye-sensitized photoelectric conversion device can be improved.

  However, the dye-sensitized photoelectric conversion device in which the light scattering particles 43 are contained in the electrolyte layer 42 is improved in photoelectric conversion efficiency immediately after fabrication than the dye-sensitized photoelectric conversion device in which the light scattering particles are not included in the electrolyte layer. The photoelectric conversion characteristics decrease with the passage of time, and after a certain period of time, the photoelectric conversion characteristics are deteriorated more than a dye-sensitized photoelectric conversion device that does not contain light scattering particles in the electrolyte layer. did.

2A and 2B are a plan view and a cross-sectional view of the dye-sensitized photoelectric conversion device 40 actually manufactured, and the plan view shows the dye-sensitized photoelectric conversion device 40 from the transparent substrate 31 side where light is incident. When viewed, the sectional view is a vertical section of the dye-sensitized photoelectric conversion device 40 cut by a plane orthogonal to the transparent substrate 31. 2A is a plan view and a cross-sectional view immediately after the production of the dye-sensitized photoelectric conversion device 40, and FIG. 2B is a plan view and a cross-sectional view after 300 hours have passed since the production of the dye-sensitized photoelectric conversion device 40 at an external temperature of 85 ° C. It is.
As shown in FIGS. 2A and 2B, immediately after the production of the dye-sensitized photoelectric conversion device 40, the boundary between the porous photoelectrode 34 carrying the photosensitizing dye and the counter electrode 35 that is visible under the electrolyte layer 42 is clear. However, after 300 hours have passed since the production of the dye-sensitized photoelectric conversion device 40 at an external temperature of 85 ° C., the photosensitizing dye is applied to the electrolyte layer 42 around the porous photoelectrode 34 carrying the photosensitizing dye. , The boundary between the porous photoelectrode 34 carrying the photosensitizing dye and the counter electrode 35 seen below the electrolyte layer 42 becomes unclear, and the porous photoelectrode 34 carrying the photosensitizing dye It was found that the concentration of the photosensitizing dye in was lower than that immediately after the production.

  Therefore, the present inventors have made further studies to solve the above problems. As a result, the deterioration of the photoelectric conversion characteristics described above is released to the electrolyte layer 42 by the desorption of the photosensitizing dye 38 bonded to the surface of the porous photoelectrode 34, and light scattering particles are passed through the electrolyte layer 42. This is because the concentration of the photosensitizing dye liberated in the electrolyte layer 42 is reduced by adsorbing and bonding to the photocathode 43, and the desorption of the photosensitizing dye 38 from the porous photoelectrode 34 is further promoted. The conclusion was reached.

FIG. 3 is a cross-sectional view of the main part showing the configuration of the dye-sensitized photoelectric conversion element 40 after 300 hours have passed at an external temperature of 85 ° C.
As shown in FIG. 3, the photosensitizing dye 38 desorbed from the surface of the porous photoelectrode 34 is released into the electrolyte layer 42, and the photosensitizing dye 38 is adsorbed and bonded to the light scattering particles 43. Desorption of the photosensitizing dye 38 from the porous photoelectrode 34 is promoted.
As described above, the detachment of the photosensitizing dye 38 is promoted, so that the photosensitizing dye 38 bonded to the surface of the porous photoelectrode 34 is remarkably reduced and the exposed portion of the surface of the porous photoelectrode 34 is increased. As a result, the amount of excited electrons is reduced and the dark current is increased, thereby deteriorating the photoelectric conversion characteristics over time.

  In order to solve the above problems, as a result of attempts to contain various light scattering particles dispersed in the electrolyte layer, a photosensitizing dye adsorption prevention layer is provided on at least a part of the surface of the light scattering particles. It was found that the light scattering particles can effectively suppress the progress of desorption of the photosensitizing dye bonded to the surface of the porous photoelectrode, and can suppress the deterioration of photoelectric conversion characteristics with time. It came to devise.

Hereinafter, modes for carrying out the invention (hereinafter referred to as “embodiments”) will be described. The description will be made in the following order.
1. First Embodiment (Dye-sensitized photoelectric conversion device and manufacturing method thereof)
2. Second Embodiment (Dye-sensitized photoelectric conversion device and manufacturing method thereof)
3. Third Embodiment (Dye-sensitized photoelectric conversion device and manufacturing method thereof)
4). Fourth Embodiment (Dye-sensitized photoelectric conversion device and manufacturing method thereof)

<1. First Embodiment>
FIG. 4 is a cross-sectional view showing the dye-sensitized photoelectric conversion device 10 according to the first embodiment.
As shown in FIG. 4, in this dye-sensitized photoelectric conversion device 10, a transparent conductive layer such as FTO (fluorine-doped tin oxide (IV) SnO ₂ ) is formed on one main surface of a transparent substrate 1 such as glass. A transparent photoelectrode 2 is provided, and a porous photoelectrode 4 composed of a porous layer obtained by sintering semiconductor fine particles 3 is provided on the transparent electrode 2, and the surface of the porous photoelectrode 4 facing the counter electrode 5 is provided on the surface. Is provided with a light-reflecting particle layer 7 configured to mix and deposit the semiconductor fine particles 3 and the high refractive material particles 6 which are, for example, spherical fine particles. One or more kinds of photosensitizing dyes 8 are bonded to the semiconductor fine particles 3 constituting the porous photoelectrode 4 and the light reflecting particle layer 7. On the other hand, a transparent conductive layer 11 is provided on one main surface of the counter substrate 9, and a counter electrode 5 is provided on the transparent conductive layer 11. An electrolyte layer 12 is provided between the light reflecting particle layer 7 configured to be deposited on the porous photoelectrode 4 on the transparent substrate 1 and the counter electrode 5 on the counter substrate 9. The electrolyte layer 12 contains spherical light scattering particles 13 in a dispersed form. The surface of the light scattering particle 13 has at least a part of a site (typically, but not limited to an OH group) on the surface of the light scattering particle 13 where the photosensitizing dye 8 is adsorbed, Most preferably, a photosensitizing dye adsorption preventing layer 14 is provided for the purpose of eliminating all of the photosensitizing dye. The outer peripheral portions of the transparent substrate 1 and the counter substrate 9 are sealed with a sealing material (not shown).

  The transparent substrate 1 is not particularly limited as long as it has a material and a shape that easily transmit light, and various substrate materials can be used, but a substrate material that has a particularly high visible light transmittance is used. Is preferred. In addition, a material having a high blocking performance for blocking moisture and gas to enter from the outside of the dye-sensitized photoelectric conversion device 10 and excellent in solvent resistance and weather resistance is preferable. Specifically, as the material of the transparent substrate 1, transparent inorganic materials such as quartz and glass, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyethylene, polypropylene, polyphenylene sulfide, polyvinylidene fluoride, acetylcellulose, bromo Examples thereof include transparent plastics such as modified phenoxy, aramids, polyimides, polystyrenes, polyarylates, polysulfones, and polyolefins. The thickness in particular of the transparent substrate 1 is not restrict | limited, It can select suitably considering the light transmittance and the performance which interrupts | blocks the inside and outside of a photoelectric conversion apparatus.

The transparent electrode 2 provided on the transparent substrate 1 is more preferable as the sheet resistance is smaller, specifically 500Ω / □ or less, more preferably 100Ω / □ or less. A known material can be used as the material for forming the transparent electrode 2 and is selected as necessary. Specifically, the material for forming the transparent electrode 2 is indium-tin composite oxide (ITO), fluorine-doped tin oxide (IV) SnO ₂ (FTO), tin oxide (IV) SnO ₂ , oxidation Zinc (II) ZnO, indium-zinc composite oxide (IZO), etc. are mentioned. However, the material which forms the transparent electrode 2 is not limited to these, It can also use combining 2 or more types.

The semiconductor fine particles 3 are selected as necessary from those already mentioned.
The photosensitizing dye 8 preferably has an acid functional group adsorbed on the surface of the porous photoelectrode. In general, the photosensitizing dye preferably has a carboxy group, a phosphoric acid group, and the like, and among them, those having a carboxy group are particularly preferable. Specific examples of the photosensitizing dye 8 include xanthene dyes such as rhodamine B, rose bengal, eosin and erythrosine, cyanine dyes such as merocyanine, quinocyanine and cryptocyanine, phenosafranine, fog blue, thiocin, and methylene blue. Examples include basic dyes such as chlorophyll, zinc porphyrin, and porphyrin compounds such as magnesium porphyrin. Others include azo dyes, phthalocyanine compounds, coumarin compounds, bipyridine complex compounds, anthraquinone dyes, and polycyclic quinone dyes. Etc. Among these, the ligand (ligand) includes a pyridine ring or an imidazolium ring, and a dye of at least one metal complex selected from the group consisting of Ru, Os, Ir, Pt, Co, Fe, and Cu is High quantum yield is preferable. In particular, cis-bis (isothiocyanato) -N, N-bis (2,2′-dipyridyl-4,4′-dicarboxylic acid) -ruthenium (II) or tris (isothiocyanato) -ruthenium (II) — A dye molecule having 2,2 ': 6', 2 "-terpyridine-4,4 ', 4" -tricarboxylic acid as a basic skeleton has a wide absorption wavelength range and is preferable. However, the photosensitizing dye 8 is not limited to these. Typically, one of these is used as the photosensitizing dye 8, but two or more kinds of photosensitizing dye 8 may be mixed and used. When two or more kinds of photosensitizing dyes are mixed and used, the photosensitizing dye 8 is preferably an inorganic substance having a property of causing MLCT (Metal to Ligand Charge Transfer) held in the porous photoelectrode 4. It has a complex dye and an organic molecular dye having the property of intramolecular CT (Charge Transfer) held by the porous photoelectrode 4. In this case, the inorganic complex dye and the organic molecular dye are adsorbed on the porous photoelectrode 4 in different conformations. The inorganic complex dye preferably has a carboxyl group or a phosphono group as a functional group bonded to the porous photoelectrode 4. The organic molecular dye preferably has a carboxyl group or a phosphono group and a cyano group, an amino group, a thiol group, or a thione group as functional groups bonded to the porous photoelectrode on the same carbon. The inorganic complex dye is, for example, a polypyridine complex, and the organic molecular dye is, for example, an aromatic polycyclic conjugated molecule having an electron donating group and an electron accepting group and having intramolecular CT properties.

The electrolyte constituting the electrolyte layer 12 is composed of an electrolytic solution, a gel-like or solid electrolyte. The electrolyte typically includes a solution containing a redox system (redox couple). Specifically, a combination of iodine (I ₂ ) and a metal iodide salt or organic iodide salt, or a combination of bromine (Br ₂ ) and a metal bromide salt or organic 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 include lithium (Li ⁺ ), sodium (Na ⁺ ), potassium (K ⁺ ), cesium (Cs ⁺ ), magnesium (Mg ²⁺ ), and calcium (Ca ²⁺ ). The cation constituting the organic compound is preferably a quaternary ammonium ion such as a tetraalkylammonium ion, a pyridinium ion, or an imidazolium ion, but is not limited thereto. The above can be mixed and used.

  In addition to the above, the electrolyte constituting the electrolyte layer 12 includes metal complexes such as a combination of ferrocyanate and ferricyanate, a combination of ferrocene and ferricinium ion, sodium polysulfide, alkylthiol and alkyl. A sulfur compound such as a combination with disulfide, a viologen dye, a combination of hydroquinone and quinone, or the like can also be used.

As the electrolyte of the electrolyte layer 12, an electrolyte combining iodine (I ₂ ) and a quaternary ammonium compound such as lithium iodide (LiI), sodium iodide (NaI), imidazolium iodide, among others, among others. preferable. The concentration of the electrolyte salt is preferably 0.05M to 10M, more preferably 0.2 to 3M with respect to the solvent. The concentration of iodine (I ₂ ) or bromine (Br ₂ ) is preferably 0.0005 to 1M, more preferably 0.001 to 0.5M. Moreover, in order to make it contain in the electrolyte layer 12 in the state which disperse | distributed the light-scattering particle | grains 13, it is preferable that electrolyte is a gel form, specifically, by mixing silica with the electrolyte solution containing said electrolyte. A method of gelling is preferred.

The material of the light scattering particles 13 may be basically any material that is not reactive with the electrolyte constituting the electrolyte layer 12, but the refractive index is more visible than the electrolyte used. A high refractive material having a size of 0.3 or more in the optical region is suitable. Considering the fact that the material of the light scattering particles 13 has a larger refractive index difference from the electrolytic solution, and the material that absorbs light having a wavelength that can be used for photoelectric conversion has a higher intensity of scattered light, as necessary. To be elected. Since the refractive index of a commonly used electrolyte is about 1.45 to 1.50, the refractive index of the light scattering particles is preferably 1.75 or more, and 1.80 or more. Is more preferred. Specific materials include metal oxides, metal sulfides, metal chlorides, iodides, bromides, titanic acid compounds, silicic acid compounds, chromic acid compounds, metal tellurides, selenium compounds, glasses, simple metals, minerals Inorganic pigments can be used. Examples of the metal oxide include titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), niobium oxide (Nb ₂ O ₅ ), copper oxide (Cu ₂ O), and aluminum oxide. (Al ₂ O ₃ ), zirconium oxide (ZrO), chromium oxide (Cr ₂ O ₃ ), cadmium oxide (CdO), magnesium oxide (MgO), ferric oxide (Fe ₂ O ₃ ), iron black (Fe ₃ O ₄ ), yttrium oxide (Y ₂ O ₃ ), europium oxide (Eu ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ), zinc oxide (ZnO), red lead (Pb ₃ O ₄ ) yellow iron oxide, etc. Can be mentioned. Examples of the metal sulfide include zinc sulfide (ZnS), barium sulfide (BaS), strontium sulfide (SrS), mercury sulfide (HgS), cadmium sulfide (CdS), and the like. Examples of the metal chloride include silver chloride (AgCl), cuprous chloride (CuCl), barium chloride (BaCl ₂ ), thallium chloride (TlCl), and the like. Examples of the iodide include potassium iodide (KI) and cesium iodide (CsI). Examples of the bromide include sodium bromide (NaBr) and thallium bromide (TlBr). Examples of the titanate compound include lead titanate (PbTiO ₂ ), strontium titanate (SrTiO ₃ ) and barium titanate (BaTiO ₂ ). Examples of the silicate compound include zircon (ZrSiO ₄ ). Examples of the chromic acid compound include barium yellow (BaCrO ₄ ) yellow lead (PbCrO ₄ ), zinc yellow (ZnCrO ₄ ), and strontium yellow (SrCrO ₄ ). Examples of metal tellurides include tellurium zinc (ZnTe). Examples of selenium compounds include arsenic selenide (As ₂ Se ₃ ). Examples of the glass include SF-2 optical glass, Ag ₂ S ₃ glass, and arsenic trisulfide glass. Examples of the carbide include carbon simple substance such as graphite and diamond, silicon carbide (β-SiC), and the like. If it is a metal simple substance, aluminum (Al), iron (Fe), platinum (Pt), germanium (Ge) etc. will be mentioned, for example. Examples of minerals include sapphire, emerald green, ebonite, spinel, barite, and the like. Examples of the inorganic pigment include lead white, yellow iron oxide, cadmium red, cobalt blue, chromium green, cadmium red, manganese purple, cobalt green, cobalt purple, and cerulean (CoO.nSnO ₂ ). In particular, when considering application to a dye-sensitized photoelectric conversion device using a photosensitizing dye having a particularly high sensitivity in the visible light region, a substance that is transparent in the visible light region has a higher efficiency of reflecting incident light. Therefore, titanium oxide (TiO ₂ ), zinc sulfide (ZnS), magnesium oxide (MgO) and the like that are transparent in the visible light region are more suitable, but are not limited to these, and the electrolyte layer 12 The provided bubbles can also be used as the light scattering particles 13, or a single or a mixture of two or more types of light scattering particles 13 can also be used.

  The particle diameter of the light scattering particle 13 is determined by setting the particle diameter that most effectively scatters incident light as the optimum particle diameter. Since the light scattering particles 13 are spherical, the particle size for scattering the light is proportional to the wavelength of the scattered light. Based on this, the optimum particle diameter of the light scattering particles 13 is determined by substituting the wavelength of incident light into a plurality of empirical formulas (see Non-Patent Document 2). For example, when the wavelength of incident light is 400 nm, the optimum particle size of the light scattering particles 13 is 0.15 to 0.22 μm as the average particle size of primary particles, and when the wavelength of incident light is 800 nm. The optimum particle size of the light scattering particles 13 is 0.30 to 0.45 μm as the average particle size of the primary particles. Based on these conditions, a plurality of spherical particles having a particle size corresponding to the wavelength distribution of incident light in the range of 0.15 to 0.45 μm are selected, and the blending ratio is appropriately determined from the wavelength distribution.

  The content of the light scattering particles 13 in the electrolyte layer 12 is preferably 1 to 50% by mass. When the content of the light scattering particles 13 is less than 1% by mass, the significant effect of the light scattering particles 13 cannot be obtained. On the other hand, when the content of the light scattering particles 13 exceeds 50% by mass, fluidity and infiltration into the porous photoelectrode 4 are impaired, and handling becomes difficult.

A substance adsorbed on the surface of the light scattering particle 13 to form the photosensitizing dye adsorption preventing layer 14 is a site (typically an OH group) on the light scattering particle 13 where the photosensitizing dye is adsorbed. Basically, it may be anything as long as it can be eliminated. Typically, the photosensitizing dye 8 is used, but is not limited thereto, and a co-adsorbent may be used. Examples of the co-adsorbent include phosphonic acid compounds, carboxylic acid compounds, isocyanate compounds, and silane compounds. It is done. Examples of the phosphonic acid compound include 1-decylphosphonic acid, decanephosphonic acid, octadecylphosphonic acid, and aminomethylphosphonic acid. Examples of the carboxylic acid compound include saturated fatty acids having different carbon numbers as exemplified by C _n H _m COOH. Examples of the isocyanate compound include alkyl isocyanates having different carbon numbers as exemplified by CH ₃ C _n NCO. Examples of silane compounds include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, hexyltrimethoxysilane, decyltrimethoxysilane, methylhydro Examples include gen siloxane and silicone oil.

  The method for adsorbing the substance onto the light scattering particles 13 is not particularly limited. For example, the substance may be an alcohol, nitrile, nitromethane, halogenated hydrocarbon, ether, dimethyl sulfoxide, amide, N-methylpyrrolidone. 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters, carbonates, ketones, hydrocarbons, water, and the like, and the light scattering particles 13 are immersed therein. Since adsorption is not limited to single layer adsorption, it is preferable that the amount of adsorbed material dissolved in the solvent is as large as possible.

  It is preferable that the electrolyte is a gel electrolyte in which a gelling agent is included in the electrolytic solution so that the light scattering particles 13 can be easily dispersed in the electrolyte layer 12. Gel electrolytes can be used as gel electrolytes by dissolving inorganic ceramic particles in addition to dissolving gelling agents, polymers, crosslinking monomers, and the like in the electrolyte composition. As for the ratio between the gelling agent and the electrolyte constituent, the more the electrolyte constituent, 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 and fluidity | liquidity and permeability become low. If it does so, since electrolyte solution will not fully infiltrate with respect to the porous photoelectrode 4 and the light reflection particle layer 7, there exists a possibility that a photoelectric conversion efficiency may fall. In order to solve this problem, the porous photoelectrode 4 and the light-reflecting particle layer 7 are filled with an electrolyte that easily infiltrates, and the electrolyte layer 12 is filled with a gel electrolyte in which light scattering particles 13 are dispersed. A multilayer electrolyte structure can be used. The electrolyte constituting the electrolyte layer 12 is not limited to a gel electrolyte, and may have a multilayer electrolyte structure with a sol electrolyte, a solid electrolyte, or the like. Further, in the multilayer electrolyte structure, the electrolyte layer 12 can be composed of a plurality of gel electrolytes having different refractive indexes, and incident light can be scattered at the interface formed in the electrolyte layer 12.

  The gel electrolyte may be basically any gel electrolyte as long as it has a low temperature dependency and has a high ionic conductivity equivalent to that of the electrolyte, such as a hydrogen bond, an ionic bond, or a coordinate bond. A so-called physical gel crosslinked by a chemical reaction or a so-called chemical gel crosslinked by a covalent bond by a chemical reaction may be used, but a chemically stable chemical gel is preferable. Moreover, even if the structure of the gel electrolyte is a homogeneous phase, it is separated into a support part that has mechanical strength and supports a solid shape and a conductive part that has high ionic conductivity and serves as a medium for electron transfer, so-called It may be a phase separation structure. In the phase separation structure, a micro phase separation type gel in which the support part is a solid phase and the conductive part is a liquid phase and is partially separated is preferable.

  As a material of the sealing material, it is preferable to use a material having light resistance, insulation, moisture resistance, and the like. Specific examples of the material for the sealing material include epoxy resin, ultraviolet curable resin, acrylic resin, polyisobutylene resin, EVA (ethylene vinyl acetate), ionomer resin, elastomer resin, ceramic, and various heat-sealing films.

  Moreover, when inject | pouring electrolyte solution, although an injection port is required, unless it is on the porous electrode 4 and the counter electrode 5 of the part facing this, the place of an injection port will not be specifically limited.

[Method for producing dye-sensitized photoelectric conversion device]
Next, a method for manufacturing the dye-sensitized photoelectric conversion device 10 will be described.
First, the transparent electrode 2 is formed by forming a transparent conductive layer on one main surface of the transparent substrate 1 by sputtering or the like.
Next, the porous photoelectrode 4 is formed on the transparent electrode 2. The method for forming the porous photoelectrode 4 is not particularly limited, but in consideration of physical properties, convenience, production cost, etc., it is preferable to use a wet film forming method. In the wet film forming method, a paste-like dispersion liquid in which the powder or sol of the semiconductor fine particles 3 is uniformly dispersed in a solvent such as water is prepared, and this dispersion liquid is applied or printed on the transparent electrode 2 of the transparent substrate 1. The method is preferred. There is no restriction | limiting in particular in the application method or printing method of a dispersion liquid, A well-known method can be used. Specifically, as a coating method, for example, a dipping method, a spray method, a wire bar method, a spin coating method, a roller coating method, a blade coating method, a gravure coating method, or the like can be used. Moreover, as a printing method, a relief printing method, an offset printing method, a gravure printing method, an intaglio printing method, a rubber plate printing method, a screen printing method, etc. can be used.

When using anatase type TiO ₂ as a material of the semiconductor fine particles 3, the anatase type TiO _2, the powder, sol, or may be used a slurry commercially available, known, such as titanium oxide alkoxide hydrolyzes You may form the thing of a predetermined particle size by the method of this. When using a commercially available powder, it is preferable to eliminate secondary agglomeration of the particles, and it is preferable to pulverize the particles using a mortar, ball mill or the like when preparing the paste-like dispersion. At this time, acetylacetone, hydrochloric acid, nitric acid, a surfactant, a chelating agent, and the like can be added to the paste-like dispersion in order to prevent the particles from which secondary aggregation has been eliminated from aggregating again. In addition, in order to increase the viscosity of the paste-like dispersion, polymers such as polyethylene oxide and polyvinyl alcohol, or various thickeners such as a cellulose-based thickener can be added to the paste-like dispersion.

  The porous photoelectrode 4 is formed by coating or printing the semiconductor fine particles 3 on the transparent electrode 2, and then electrically connecting the semiconductor fine particles 3 to improve the mechanical strength of the porous photoelectrode 4. In order to improve the adhesiveness, baking is preferable. Although there is no restriction | limiting in particular in the range of baking temperature, When the temperature is raised too much, since the electrical resistance of the transparent electrode 2 will become high, and also the transparent electrode 2 may melt | dissolve, 40-700 degreeC is preferable normally, 40- 650 ° C. is more preferable. The firing time is not particularly limited, but is usually about 10 minutes to 10 hours. Alternatively, the mixture of the high refractive material particles 6 and the semiconductor fine particles 3 may be deposited on the surface of the porous photoelectrode 4 opposite to the surface in contact with the transparent electrode 2 to provide the light reflecting particle layer 7 and fired. , Appropriately selected as necessary.

  For example, a dip treatment with a titanium tetrachloride aqueous solution or a titanium oxide ultrafine particle sol having a diameter of 10 nm or less may be performed for the purpose of increasing the surface area of the semiconductor fine particles 3 or increasing necking between the semiconductor fine particles 3 after firing. . When a plastic substrate is used as the transparent substrate 1 that supports the transparent electrode 2, the porous photoelectrode 4 is formed on the transparent electrode 2 using a paste-like dispersion liquid containing a binder, and the transparent electrode is formed by heating press. It is also possible to pressure-bond to 2.

  Next, the photosensitizing dye 8 is bonded to the porous photoelectrode 4 by immersing the transparent substrate 1 on which the porous photoelectrode 4 is formed in a solution in which the photosensitizing dye 8 is dissolved in a predetermined solvent. Let

On the other hand, the transparent conductive layer 11 and the counter electrode 5 are sequentially formed on the counter substrate 9 by sputtering or the like.
Next, the transparent substrate 1 and the counter substrate 9 are arranged so that the porous photoelectrode 4 and the counter electrode 5 face each other at a predetermined interval, for example, 1 to 100 μm, preferably 1 to 50 μm. And the sealing material (not shown) is formed in the outer peripheral part of the transparent substrate 1 and the counter substrate 9, and the space where the electrolyte layer 12 is enclosed is made.

Next, the photosensitizing dye adsorption preventing layer 14 is formed on the light scattering particles 13 included in the state dispersed in the electrolyte layer 12. Specifically, in the case of using TiO ₂ for the light scattering particles 13, the TiO ₂ particles are put into a solution containing a photosensitizing dye and / or a co-adsorbent that is sufficiently thicker than the single layer adsorption. Then, the photosensitizing dye adsorption preventing layer 14 is formed by sufficiently adsorbing and / or encapsulating the substance on the surface of the light scattering particles 13 by a process such as stirring and centrifugation.

The electrolyte layer 12 is a gel electrolyte, and is prepared by adding silica fine particles to the electrolytic solution and stirring. Alternatively, the electrolyte solution may be gelled by a method of forming a gel electrolyte by swelling an electrolyte solution in an organic compound, particularly a polymer. Typically, polyethylene oxide (PEO; [CH ₂ —CH ₂ —O] _{n is used.} ), Polyacrylonitrile (PAN; [CH ₂ (CN) —CH ₂ ] _n ), poly (vinylidene fluoride) (PVDF; [CH ₂ —CF ₂ ] _n ), polymethyl methacrylate (PMMA; [C (CH ₃ ) ( COOCH ₃ ) —CH ₂ ] _n ), poly (vinylidene fluoride) (PVDF; [CH ₂ —CF ₂ ] _n ) and hexafluoropropylene (HFP; CF ₃ —CF═CF ₂ ) copolymer PVDF-HFP, etc. The method of preparing the gel electrolyte by swelling the solution is suitable, but the method is not limited to these methods, and it is basically possible if the electrolyte can be gelled by a substance having a low reactivity with the electrolyte. May be any method may be when the electrolytic solution is an aqueous solution uses materials such as thickening polysaccharide of plant origin, such as agar or gelatin to prepare a gel electrolyte.

  The light scattering particles 13 in which the photosensitizing dye adsorption preventing layer 14 is formed on the gel electrolyte are added in a range where the content does not exceed 50 mass%, and the light scattering particles 13 are dispersed in the gel electrolyte by a step such as stirring. A light scattering gel electrolyte is prepared.

Next, a light scattering gel electrolyte solution is injected into a space in which the electrolyte layer 12 is sealed, for example, from a liquid injection port (not shown) formed in advance in the sealing material, thereby forming the electrolyte layer 12. Thereafter, the liquid injection port is closed. In the case of a multilayer electrolyte structure of an electrolytic solution and a light-scattering gel electrolytic solution, first, the electrolytic solution is injected from the injection port to sufficiently infiltrate the porous photoelectrode 4 and the light reflecting particle layer 7, and then A light-scattering gel electrolyte solution is injected to form an electrolyte layer 12. Thereafter, the liquid injection port is closed. Further, when the electrolyte is a gel electrolyte gelled using a polymer or the like, or an all solid gel electrolyte, a polymer solution containing an electrolyte and a plasticizer is cast on the porous photoelectrode 4 or the like. Apply by. 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, heating and pressurizing operations are performed as necessary so that the electrolyte solution of the electrolyte layer 12 sufficiently infiltrates the porous photoelectrode 4 and the light reflecting particle layer 7, or the electrolyte solution Can be further infused to sufficiently infiltrate the porous photoelectrode 4 and the light-reflecting particle layer 7.
Thus, the target dye-sensitized photoelectric conversion device 10 is manufactured.

[Operation of dye-sensitized photoelectric conversion device]
Next, the operation of the dye-sensitized photoelectric conversion device 10 will be described.

  When light is incident, the dye-sensitized photoelectric conversion device 10 operates as a photovoltaic cell having the counter electrode 5 as a positive electrode and the porous photoelectrode 4 as a negative electrode.

  That is, when the photosensitizing dye 8 supported on the porous photoelectrode 4 absorbs the photons transmitted through the transparent substrate 1 and the transparent electrode 2, the electrons in the photosensitizing dye 8 are excited from the ground state to the excited state. The Excited electrons are taken out to the conduction band of the porous photoelectrode 4 through the electrical coupling between the photosensitizing dye 8 and the porous photoelectrode 4 and pass through the porous photoelectrode 4 to form a transparent electrode. 2 is reached.

On the other hand, the photosensitizing dye 8 that has lost electrons is converted from the reducing agent in the electrolyte layer 12, for example, I ⁻ to the following reaction 2I ⁻ → I ₂ + 2e ^{−.
_{I 2 + I - → I 3}} -
To receive electrons and produce an oxidant, for example I ₃ ⁻ , in the electrolyte layer 12. 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 ^-
Then, electrons are received from the counter electrode 5 and reduced to the original reducing agent.

  The electrons flowing out from the transparent electrode 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 8 or the electrolyte layer 12.

  On the other hand, the incident light transmitted without being absorbed by the photosensitizing dye 8 carried on the porous photoelectrode 4 is scattered by the light reflecting particle layer 7, and the scattered photons are incident on the porous photoelectrode 4 again. Thus, light energy is converted into electric energy in the same manner as described above. Further, the light transmitted without being reflected by the light reflecting particle layer 7 is scattered by the light scattering particles 13 in the electrolyte layer 12, and the scattered photons are incident on the porous photoelectrode 4 again, similarly to the above. Light energy is converted into electrical energy.

  As described above, according to the first embodiment, the photosensitizing dye adsorption preventing layer 14 is provided on at least a part of the surface of the light scattering particles 13 contained in the electrolyte layer 12 in a dispersed state. Therefore, the detachment of the photosensitizing dye 8 supported on the porous photoelectrode 4 can be effectively suppressed. For this reason, deterioration with time of photoelectric conversion characteristics caused by the desorption of the photosensitizing dye 8 carried on the porous photoelectrode 4 can be suppressed. Thereby, it is not necessary to increase the thickness of the porous photoelectrode 4 and the light reflecting particle layer 7 more than necessary in order to increase the utilization rate of incident light, and the thickness can be made optimum. Further, since the light scattering particles 13 are dispersed in the electrolyte layer 12, the utilization factor of incident light can be improved. Further, since the electrolyte layer 12 is a gel electrolyte, the light scattering particles 13 in the electrolyte layer 12 are less likely to aggregate, so that the scattering efficiency of incident light by the light scattering particles 13 is improved. It is also possible to reduce the leakage of water and the volatilization of the solvent constituting the electrolytic solution. As described above, it is not necessary to make the porous photoelectrode 4 thick, and it is possible to realize a high-performance dye-sensitized photoelectric conversion device 10 having high photoelectric conversion efficiency and little deterioration with time of the photoelectric conversion efficiency.

<2. Second Embodiment>
FIG. 5 is a sectional view showing the dye-sensitized photoelectric conversion device 10 according to the second embodiment.
As shown in FIG. 5, the light scattering particle 13 includes a light scattering particle 13 a having a spherical shape with a particle size in the range of 0.15 to 0.22 μm as an average particle size of primary particles, and an average particle having a particle size of primary particles. The light scattering particles 13b having a spherical shape with a diameter in the range of 0.30 to 0.45 [mu] m are configured at a substantially equal ratio. The second embodiment is suitable for the case where incident light in which two wavelength components are 400 nm and 800 nm and two wavelength components are distributed at an equal ratio is scattered by the light scattering particles 13.
Other configurations and manufacturing method of the dye-sensitized photoelectric conversion device 10 are the same as those of the first embodiment.

  According to the second embodiment, in addition to the same advantages as those of the first embodiment, the following advantages can be obtained. That is, since a plurality of particle sizes of the light scattering particles 13 are set and contained in the electrolyte layer 12, by setting the particle size and content of the light scattering particles 13 according to the wavelength distribution of the incident light, the sodium lamp In particular, the utilization factor can be increased in such a line spectrum light or light obtained by synthesizing light of a specific spectrum such as LED illumination.

<3. Third Embodiment>
FIG. 6 is a cross-sectional view showing a dye-sensitized photoelectric conversion device 20 according to the third embodiment.
As shown in FIG. 6, in the dye-sensitized photoelectric conversion device 20, the photosensitizing dye adsorption preventing layer 14 is formed on at least a part of the surface of the light scattering particles 23 having an anisotropic shape in the electrolyte layer 12. What is provided is distributed.

The light scattering particle 23 may be basically any shape as long as it has an anisotropic shape, but is preferably an elongated shape having a ratio of the major axis to the minor axis of 2 or more. Examples of the shape include a needle shape, a rod shape, a spinning bell shape, an elliptical shape, and a capsule shape. In particular, when it is desired to effectively scatter all incident light in the visible light wavelength range of 400 nm to 800 nm, the shape of the light scattering particles 23 has an average major axis of 0.3 μm or more and a major axis with respect to the minor axis. The ratio may be 2 or more.
As the material of the light scattering particles 23, a high refractive material that has a refractive index of 0.3 or more larger than the electrolyte used and does not dissolve in the electrolyte is suitable. The material of the light scattering particle is selected as necessary in consideration of the fact that the material having a larger refractive index difference from the electrolyte and having a smaller absorption of light having a wavelength that can be used for photoelectric conversion has a stronger scattered light intensity. It is. Since the refractive index of the electrolyte used generally is about 1.45 to 1.50, the refractive index of the light scattering particles is preferably 1.75 or more, and 1.80 or more. Is more preferred.

  The content of the light scattering particles 23 in the electrolyte layer 12 is preferably 1 to 50% by mass. If the content of the light scattering particles 23 is less than 1% by mass, the significant effect of the light scattering particles 23 cannot be obtained. On the other hand, when the content of the light scattering particles 23 exceeds 50% by mass, fluidity and infiltration are impaired, and handling becomes difficult.

  Other configurations and manufacturing method of the dye-sensitized photoelectric conversion device 20 are the same as those in the first embodiment.

[Operation of dye-sensitized photoelectric conversion device]
When light is incident, the dye-sensitized photoelectric conversion device 20 operates as a photovoltaic cell having the counter electrode 5 as a positive electrode and the porous photoelectrode 4 as a negative electrode.

  That is, when the photosensitizing dye 8 supported on the porous photoelectrode 4 absorbs the photons transmitted through the transparent substrate 1 and the transparent electrode 2, the electrons in the photosensitizing dye 8 are excited from the ground state to the excited state. The Excited electrons are taken out to the conduction band of the porous photoelectrode 4 through the electrical coupling between the photosensitizing dye 8 and the porous photoelectrode 4 and pass through the porous photoelectrode 4 to form a transparent electrode. 2 is reached.

On the other hand, the photosensitizing dye 8 that has lost electrons is converted into the following reaction 2I ⁻ → I ₂ + 2e ⁻ from the reducing agent in the electrolyte layer 12, for example, I ^{−.
_{I 2 + I - → I 3}} -
To receive an electron and produce an oxidant, eg, I 3-in the electrolyte layer 12. The resulting oxidizing agent reaches the counter electrode 5 by diffusion, the reverse reaction of the reaction I ^3- → I ₂ + I ^-
I ₂ + 2e ^- → 2I ^-
Then, electrons are received from the counter electrode 5 and reduced to the original reducing agent.

  The electrons flowing out from the transparent electrode 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 8 or the electrolyte layer 12.

  On the other hand, the incident light transmitted without being absorbed by the photosensitizing dye 8 carried on the porous photoelectrode 4 is scattered by the light reflecting particle layer 7, and the scattered photons are incident on the porous photoelectrode 4 again. Thus, light energy is converted into electric energy in the same manner as described above. Further, the light transmitted without being reflected by the light reflecting particle layer 7 is scattered by the light scattering particles 23 in the electrolyte layer 12. At this time, since the light scattering particles 23 have an anisotropic shape, light in a wide wavelength range is effectively scattered. The scattered photons are incident on the porous photoelectrode 4 again, and the light energy is converted into electric energy as described above.

<Example 1>
A dye-sensitized photoelectric conversion device was produced as follows.
First, as the transparent electrode 2, a conductive glass substrate with an FTO layer for amorphous solar cells (manufactured by Nippon Sheet Glass Co., Ltd., sheet resistance 10 Ω / □, thickness 1.1 mm) is formed into a rectangle 15 mm long × 25 mm wide. processed. 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-out portion, and the porous photoelectrode 4 is formed in the remaining square region of 15 mm long × 15 mm wide.

Next, a paste dispersion of TiO ₂ was applied to the FTO layer in the rectangular region of the transparent electrode 2 to form a titanium oxide fine particle paste layer having a diameter of 5 mm and a thickness of 20 μm. At this time, using a screen printing machine and a circular screen mask, a transparent Ti-Nanoxide TSP paste (trade name; manufactured by Solaronix) layer is first formed on the FTO layer with a thickness of 7 μm, 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. Thereafter, the TiO ₂ fine particles were sintered on the FTO layer by holding at 500 ° C. for 30 minutes. A 0.1 M titanium chloride (IV) TiCl ₄ aqueous solution was added dropwise to the sintered TiO ₂ film and held at 70 ° C. for 30 minutes. Next, the titanium oxide porous layer was sufficiently washed with pure water and ethanol and dried. Thereafter, baking was performed again at 500 ° C. for 30 minutes. In these processes,
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. Thereafter, the ultraviolet light irradiation apparatus is used to irradiate the TiO ₂ sintered body with ultraviolet light for 30 minutes, and impurities such as organic substances contained in the TiO ₂ sintered body are oxidatively decomposed and removed by the photocatalytic action of TiO _2. The treatment for increasing the activity of the TiO ₂ sintered body was performed.

  As the photosensitizing dye 8, 23.8 mg of sufficiently purified Z907 was dissolved in 50 ml of a mixed solvent in which acetonitrile and tert-butanol were mixed at a volume ratio of 1: 1 to prepare a solution of the photosensitizing dye 8. . Z907 is cis-bis (isothiocyanato) (H2dcbpy) (dnbpy) ruthenium complex (where H2dcbpy is 4,4′-dicarboxy-2,2′-bipyridine and dnbpy is 4,4′-dinonyl-2) , 2′-bipyridine.).

Next, the porous photoelectrode 4 was immersed in this photosensitizing dye 8 solution at room temperature for 24 hours to hold the photosensitizing dye 8 on the surface of the TiO ₂ fine particles. Next, the porous photoelectrode 4 was washed sequentially with an acetonitrile solution of 4-tert-butylpyridine and acetonitrile, and then the solvent was evaporated in the dark and dried. As a result, a porous photoelectrode 4 on which the photosensitizing dye 8 was adsorbed was obtained.

Next, 1.65 g (1 mol / L) of 1,3-dimethyl-3-imidazolium iodide, 0.28 g (0.15 mol / L) of iodine (I ₂ ), 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 (the concentration in () above) 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.

  Next, in order to form a photosensitizing dye adsorption preventing layer on the light scattering particles 23, 184 mg of Z907 sufficiently purified as a dye to be adsorbed, mixed solvent of acetonitrile and tert-butanol at a volume ratio of 1: 1 Dissolved in 30 ml to prepare an adsorbent dye solution

  Next, 1 g of acicular titanium oxide fine particles FTL100 (trade name; manufactured by Ishihara Sangyo Co., Ltd.) having an anisotropic shape as the light scattering particles 23 is added to the adsorbing dye solution, and the mixture is stirred at room temperature for 86 hours. Z907 was adsorbed on the surface. Next, it was washed twice by centrifugation and vacuum-dried at 60 ° C. for 2 hours. As a result, anisotropically shaped light scattering particles 23 provided with the photosensitizing dye adsorption preventing layer 14 made of adsorbed Z907 were obtained.

Next, 1.65 g (1 mol / L) 1,3-dimethyl-3-imidazolium iodide, 0.28 g (0.15 mol / L) iodine (I ₂ ), 0.64 g 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 (the concentration in () above) 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.

Next, light scattering particles 23 on which the photosensitizing dye adsorption preventing layer 14 was formed were added to the gel electrolyte solution to prepare a light scattering gel electrolyte solution. The mass ratio in the light scattering gel electrolyte is: gel electrolyte: light scattering particles 23 = 80: 20
It is. The gel electrolyte containing the light scattering particles 23 was deposited on the porous photoelectrode 4 on the transparent electrode 2.

  On the other hand, as the counter substrate 9, similarly to the transparent substrate 1 provided with the transparent electrode 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 0.1 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. On the remaining FTO layer in a square area of 15 mm in length and 15 mm in width, a chromium (Cr) layer having a thickness of 50 nm and a platinum (Pt) layer having a thickness of 100 nm are sequentially laminated by sputtering, and the counter electrode 5 is formed. Was made.

  Next, using a dispenser, an ultraviolet (UV) curable adhesive was deposited on the transparent electrode 2 so as to be cured with a width of 2 mm from the outer periphery to the inner region of the square region. Thereafter, the respective square regions of the transparent substrate 1 provided with the transparent electrode 2 and the counter substrate 9 were opposed to each other so that the porous photoelectrode 4 and the counter electrode 5 face each other. The counter substrate 9 is provided with a hole having a diameter of 0.5 mm, and this hole functions as an air escape path for bonding.

  Next, after the hole provided in the counter substrate 9 is filled with an ultraviolet (UV) curable adhesive and sealed, the ultraviolet (UV) is irradiated to cure the ultraviolet (UV) curable adhesive, thereby increasing the dye. A photoelectric conversion device was completed.

<Example 2>
In order to form the photosensitized adsorption preventing layer 14 on the light scattering particles 23, DPA (1-decylphosphonic acid) that was sufficiently purified was used as an adsorbing substance. Otherwise, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

The desorption of the photosensitizing dye 8 adsorbed on the porous photoelectrode 4 in the dye-sensitized photoelectric conversion apparatus was verified.
First, five transparent electrodes 2 formed with porous photoelectrodes 4 adsorbed with Z907 as photosensitizing dye 8 produced in Example 1 were placed in a sealable container, and gel electrolysis in Example 1 was performed. Only the liquid is immersed so as to cover the entire porous photoelectrodes 4 and then sealed so that the gel electrolyte does not volatilize. This sample is referred to as “no light scattering particles”. On the other hand, 5 transparent electrodes 2 formed with porous photoelectrodes 4 adsorbed with photosensitizing dye 8 produced in Example 1 were placed in a sealable container different from “no light scattering particles”. After the light-scattering gel electrolyte solution, in which the light-scattering particles 23 are mixed in the same proportion as in Example 1, is immersed so as to cover the entire porous photoelectrode 4, the light-scattering gel electrolyte solution does not volatilize. Seal like so. This sample is referred to as “with light scattering particles”. After these two containers were left for 730 hours in an environment with an outside air temperature of 85 ° C., two of the five transparent electrodes 2 taken out of the container were replaced with the electrolyte solution only as the gel electrolyte solution, and the others were as in Example 1. In the same manner, dye-sensitized solar cells were produced. The remaining three transparent electrodes 2 taken out from the container were each measured for the amount of photosensitizing dye 8 adsorbed on the porous photoelectrode 4 after washing the porous photoelectrode 4. Table 1 shows the characteristics of the dye-sensitized photoelectric conversion devices manufactured. Moreover, the graph which compared the value of the open circuit voltage of each dye-sensitized photoelectric conversion apparatus and the short circuit current is shown in FIG. Moreover, the graph which showed the comparison of the photoelectric conversion efficiency of each dye-sensitized photoelectric conversion apparatus and the adsorption amount of the photosensitizing dye 8 is shown in FIG. In FIG. 8, the bar graph shows the conversion efficiency, and the line graph shows the amount of Z907 adsorbed by the photosensitizing dye 8.

  As shown in FIG. 8, the dye-sensitized photoelectric conversion device manufactured using the transparent electrode 2 with “light scattering particles” is dye-sensitized with the transparent electrode 2 without “light scattering particles”. Compared with the photoelectric conversion device, the adsorption amount of Z907, which is the photosensitizing dye 8 adsorbed on the porous photoelectrode 4, is decreased, and the photoelectric conversion efficiency is also decreased. Further, as shown in Table 1 and FIG. 7, the dye-sensitized photoelectric conversion device manufactured using the transparent electrode 2 “with light scattering particles” is manufactured using the transparent electrode 2 “without light scattering particles”. Both the open-circuit voltage and the short-circuit current are greatly reduced and the internal resistance is increased as compared with the dye-sensitized photoelectric conversion device. The decrease in the open circuit voltage is considered to be caused by the decrease in the amount of excited electrons due to the desorption of the photosensitizing dye 8 from the porous photoelectrode 4, and the decrease in the short circuit current is caused by the photosensitization from the porous photoelectrode 4. This is probably because the exposed portion of the surface of the titanium oxide forming the porous photoelectrode 4 increased and the dark current increased as the dye 8 was detached.

<Comparative example 1>
As the light scattering particles 23 added to the gel electrolyte, spherical titanium oxide fine particles P25 not provided with the photosensitizing dye adsorption preventing layer 15 were used. Otherwise, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

<Comparative example 2>
As the light scattering particles 23 added to the gel electrolyte, spherical titanium oxide fine particles TA300 not provided with the photosensitizing dye adsorption preventing layer 15 were used. Otherwise, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

<Comparative Example 3>
As the light scattering particles 23 added to the gel electrolyte, anisotropically shaped acicular titanium oxide fine particles FTL100 not provided with the photosensitizing dye adsorption preventing layer 15 were used. Otherwise, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

<Comparative example 4>
The gel electrolyte was used as an electrolyte as it was without adding highly refractive fine particles. Otherwise, a dye-sensitized photoelectric conversion device was produced in the same manner as in Example 1.

Table 2 shows the characteristics of the light scattering particles 23 used in Examples 1 and 2 and Comparative Examples 1 to 4.

While irradiating pseudo sunlight (AM1.5,100mW / cm ²⁾ using a circular mask area 0.188Cm ² In each of the examples and comparative examples, 24 ° C. The prepared dye-sensitized photoelectric conversion device photoelectric conversion efficiency Evaluated.

Table 3 shows an example of the characteristics of the dye-sensitized photoelectric conversion devices prepared in Comparative Examples 1 to 4.

  In Table 3, from the comparison of photoelectric conversion efficiency immediately after producing the dye-sensitized photoelectric conversion devices of Comparative Examples 1 to 3 and Comparative Example 4, when titanium oxide fine particles having a high refractive index were mixed into the electrolyte layer 12, It can be seen that there is an effect of improving the photoelectric conversion efficiency. In particular, the needle-shaped FTL100 with high scattering efficiency has a high degree of improvement in photoelectric conversion efficiency, and the photoelectric conversion efficiency is 7% compared to the photoelectric conversion efficiency when the electrolyte layer 12 is not mixed with the FTL100. A significant improvement is seen.

Table 4 is a table showing the change over time of the photoelectric conversion efficiency of the dye-sensitized photoelectric conversion devices prepared in Examples 1-2 and Comparative Examples 3-4.

  FIG. 9 is a diagram showing a change with time in photoelectric conversion efficiency of the dye-sensitized photoelectric conversion device in each example and each comparative example.

  In Table 4 and FIG. 9, from the comparison of the photoelectric conversion efficiency in the elapsed time of 116 hours between Examples 1-2 and Comparative Example 4 and Comparative Example 3, FTL100 in which the photosensitizing dye adsorption preventing layer 15 is not provided is used as the electrolyte layer. In the dye-sensitized photoelectric conversion device of Comparative Example 3 mixed with No. 12, the photoelectric conversion efficiency drastically decreases with time, and Comparative Example 4 does not mix FTL 100 with the electrolyte layer 12 at the time of 116 hours. It can be seen that the photoelectric conversion efficiency is lower than that of the dye-sensitized photoelectric conversion device. This is because, as shown in FIG. 3 described above, the dye-sensitized photoelectric conversion device of Comparative Example 3 is such that the photosensitizing dye 8 adsorbed on the porous photoelectrode 4 becomes light-scattering fine particles in the electrolyte layer 12 with time. More specifically, the photosensitizing dye 8 adsorbed on the porous photoelectrode 4 is desorbed and transferred to the electrolytic solution, and then adsorbed on the light scattering particles 23, thereby causing the electrolyte. The concentration of the photosensitizing dye 8 in the layer 12 decreases, and the photosensitizing dye 8 further desorbs. On the other hand, the dye-sensitized photoelectric conversion devices of Examples 1 and 2 in which the FTL 100 provided with the photosensitizing dye adsorption preventing layer 15 for preventing the adsorption of the photosensitizing dye 8 to the light scattering particles 23 is mixed with the electrolyte layer 12. Although the photoelectric conversion efficiency is decreased, the change is compared with the dye-sensitized photoelectric conversion apparatus of Example 3 in which FTL100 not provided with the photosensitizing dye adsorption preventing layer 15 is mixed with the electrolyte layer 12. The photoelectric conversion efficiency is maintained at a sufficiently high value as compared with the dye-sensitized discharge conversion device of Comparative Example 3 at a time when the elapsed time is 116 hours. This is because, for example, the photosensitizing dye 8 is detached from the porous photoelectrode 4 into the electrolyte layer 12. Initially, the photoelectric conversion efficiency rapidly decreases, but the photosensitizing dye 8 is present in the electrolyte layer 12. Is shifted to a certain level, the concentration of the photosensitizing dye 8 in the electrolyte layer 12 is saturated, and the light scattering particles 23 are provided with a photosensitizing dye adsorption preventing layer 15 for preventing the adsorption of the photosensitizing dye 8. Therefore, the adsorption of the photosensitizing dye 8 to the light scattering particles 23 does not occur, and it is considered that the desorption rate becomes gentle after 74 hours, and the decrease rate of the photoelectric conversion efficiency is also increased by the dye increase of Comparative Example 3. Compared with the photoelectric conversion device, it is about 1/3.

  From the comparison of photoelectric conversion efficiency at the elapsed time of 509 hours between Examples 1 and 2 and Comparative Example 4 and Comparative Example 3, Comparative Example 3 shows the photoelectric at the time after 509 hours have elapsed since the preparation of the dye-sensitized photoelectric conversion device. The conversion efficiency is greatly reduced to about 64% as compared with the photoelectric conversion efficiency immediately after the production, and the photoelectric conversion efficiency is significantly lower than that of the dye-sensitized photoelectric conversion device of Comparative Example 4. The photoelectric conversion efficiency remains at 85% as compared with the dye-sensitized photoelectric conversion device of Comparative Example 4. This is considered to be caused by the fact that the photosensitizing dye 8 adsorbed on the porous photoelectrode 4 migrates to the light scattering particles 23 in the electrolyte layer 12 with the passage of time described above, and 509 hours have passed since the production. The photosensitizing dye 8 moves into the electrolyte layer 12 at a later time, and the dye sensitization in Examples 1 and 2 and Comparative Example 4 in which the concentration of the photosensitizing dye 8 in the electrolyte layer 12 is almost saturated. In contrast to the photoelectric conversion device, the photosensitized photoelectric conversion device of Comparative Example 3 has the photosensitizing dye 8 in the electrolyte layer 12 adsorbed on the light scattering particles 23 in the electrolyte layer 12. The concentration of 8 is not saturated, and even after 509 hours have passed, the desorption rate of the photosensitizing dye 8 from the porous photoelectrode 4 maintains the rate after 74 hours have passed. It is considered that the photoelectric conversion efficiency also decreases in proportion to this. On the other hand, in the dye-sensitized photoelectric conversion device of Example 1 in which the FTL 100 provided with the photosensitizing dye adsorption preventing layer 15 is mixed in the electrolyte layer 12, although the photoelectric conversion efficiency is lowered, the change is slow. In both Examples 1 and 2, the photoelectric conversion efficiency at the time after 509 hours was maintained at a high value of 88% as compared with the photoelectric conversion efficiency immediately after the production, and the FTL 100 was mixed in the electrolyte layer 12. Even if it compares with the dye-sensitized photoelectric conversion apparatus of the comparative example 4 which is not made to carry out, both the photoelectric conversion efficiency of Examples 1-2 is maintaining the high value. Until 509 hours have passed, the photoelectric conversion efficiency of both Examples 1 and 2 is maintained at 105% or more as compared with the dye-sensitized photoelectric conversion device of Comparative Example 4 in which FTL100 is not mixed in electrolyte layer 12. doing.

  As described above, according to the third embodiment, the same advantages as those of the first embodiment can be obtained, and the light scattering fine particles 23 have an anisotropic shape. The effective particle size for transmitted light can be continuously changed. In particular, by using the light scattering particles 23 having an anisotropic shape, a large number of wavelength components can be continuously obtained only by containing the light scattering particles 23 having one kind of anisotropic shape in the electrolyte layer 12. Sunlight, which is continuous spectrum light, can be effectively scattered over the entire wavelength range, eliminating the need to contain spherical fine particles of various particle sizes according to the wavelength distribution, and one kind of anisotropic shape The incident light can be effectively scattered with a simple configuration of containing the light scattering particles 23 having the above.

<4. Fourth Embodiment>
FIG. 10 is a cross-sectional view showing a dye-sensitized photoelectric conversion device 30 according to the fourth embodiment.
As shown in FIG. 10, in this dye-sensitized photoelectric conversion device, light scattering particles 23 having an anisotropic shape are contained in the electrolyte layer 12 in a dispersed state, and spherical spacer fine particles 18 are further contained in the electrolyte. It is contained in the layer 12.

  The particle diameter of the spacer fine particles 18 is not less than the short diameter and not more than the long diameter of the light scattering particles 23 in which the average particle diameter of the primary particles has an anisotropic shape. The electrolyte layer 12 of the dye-sensitized photoelectric conversion device is formed very thin, and the spacer fine particles 18 are arranged so as to serve as a spacer connecting the porous photoelectrode 4 and the counter electrode 5. The light scattering particles 23 having an anisotropic shape are continuously arranged such that the major axis is approximately parallel to the surface of the counter electrode 5 and does not overlap in the direction perpendicular to the surface of the counter electrode 5.

The material of the spacer fine particles 18 may be basically any material as long as it has no reactivity with the electrolyte, but the refractive index is 0.3 or more in the visible light region than the electrolyte used. Large, highly refractive materials can also be used and are selected as needed. Since the refractive index of a commonly used electrolyte is about 1.45 to 1.50, the refractive index of the light scattering particles is preferably 1.75 or more, and 1.80 or more. Are more preferable, and specific materials include metal oxide, metal sulfide, metal chloride, iodide, bromide, titanic acid compound, silicic acid compound, chromic acid compound, metal telluride, selenium compound, glass For example, titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), niobium oxide (Nb ₂ O ₅ ), copper oxide (Cu ₂ O), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO), chromium oxide (Cr ₂ O ₃ ), cadmium oxide (CdO), magnesium oxide (MgO), ferric oxide (Fe ₂ O ₃ ) , Iron black (Fe ₃ O ₄ ), yttrium oxide (Y ₂ O ₃ ), europium oxide (Eu ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ), zinc oxide (ZnO), red lead (Pb ₃ O ₄ ) yellow iron oxide, etc. It is done. Examples of the metal sulfide include zinc sulfide (ZnS), barium sulfide (BaS), strontium sulfide (SrS), mercury sulfide (HgS), cadmium sulfide (CdS), and the like. Examples of the metal chloride include silver chloride (AgCl), cuprous chloride (CuCl), barium chloride (BaCl ₂ ), thallium chloride (TlCl), and the like. Examples of the iodide include potassium iodide (KI) and cesium iodide (CsI). Examples of the bromide include sodium bromide (NaBr) and thallium bromide (TlBr). Examples of the titanate compound include lead titanate (PbTiO ₂ ), strontium titanate (SrTiO ₃ ) and barium titanate (BaTiO ₂ ). Examples of the silicate compound include zircon (ZrSiO ₄ ). Examples of the chromic acid compound include barium yellow (BaCrO ₄ ) yellow lead (PbCrO ₄ ), zinc yellow (ZnCrO ₄ ), and strontium yellow (SrCrO ₄ ). Examples of metal tellurides include tellurium zinc (ZnTe). Examples of selenium compounds include arsenic selenide (As ₂ Se ₃ ). Examples of the glass include SF-2 optical glass, Ag ₂ S ₃ glass, and arsenic trisulfide glass. Examples of the carbide include carbon simple substance such as graphite and diamond, silicon carbide (β-SiC), and the like. If it is a metal simple substance, aluminum (Al), iron (Fe), platinum (Pt), germanium (Ge) etc. will be mentioned, for example. Examples of minerals include sapphire, emerald green, ebonite, spinel, barite, and the like. Examples of the inorganic pigment include lead white, yellow iron oxide, cadmium red, cobalt blue, chromium green, cadmium red, manganese purple, cobalt green, cobalt purple, and cerulean (CoO.nSnO ₂ ). In particular, since titanium oxide (TiO ₂ ), zinc sulfide (ZnS), magnesium oxide (MgO), and the like are transparent in the visible light region, dye sensitization using the photosensitizing dye 8 having particularly high sensitivity in the visible light region. When considering application to a photoelectric conversion device, a material that is transparent in the visible light region is more suitable because it has a higher efficiency of reflecting incident light, but is not limited thereto, and is not limited thereto. Alternatively, two or more kinds of light scattering particles 13 can be mixed and used.

  The content of the light scattering particles 23 in the electrolyte layer 12 is preferably in the range of 1 to 50% by mass, and is preferably not more than 50% by mass with the spacer fine particles 18 added. If the content of the light scattering particles 23 is less than 1% by mass, a significant effect of the light scattering particles 23 cannot be obtained. Conversely, the total content of the light scattering particles 23 and the spacer fine particles 18 exceeds 50% by mass. And fluidity | liquidity and invasiveness will be impaired and handling will become difficult.

  The method for adsorbing the substance to the light scattering particles 23 is not particularly limited. For example, the substance may be an alcohol, nitrile, nitromethane, halogenated hydrocarbon, ether, dimethyl sulfoxide, amide, N-methylpyrrolidone, 1, It is dissolved in a solvent such as 3-dimethylimidazolidinone, 3-methyloxazolidinone, esters, carbonates, ketones, hydrocarbons, and water, and the light scattering particles 23 are immersed in the solvent, or contains a photosensitizing dye. The solution can be applied onto the porous photoelectrode 4. Since adsorption is not limited to single layer adsorption, it is preferable that the amount of the substance dissolved in the solvent is as large as possible.

  It is also effective to provide the photosensitizing dye adsorption preventing layer 14 on at least a part of the surface of the spacer fine particles 18. The configuration of the photosensitizing dye adsorption preventing layer 14 is the same as that of the light scattering particle 23.

[Operation of dye-sensitized photoelectric conversion device]
When light is incident, the dye-sensitized photoelectric conversion device 30 operates as a photovoltaic cell having the counter electrode 5 as a positive electrode and the porous photoelectrode 4 as a negative electrode.

  That is, when the photosensitizing dye 8 supported on the porous photoelectrode 4 absorbs the photons transmitted through the transparent substrate 1 and the transparent electrode 2, the electrons in the photosensitizing dye 8 are excited from the ground state to the excited state. The Excited electrons are taken out to the conduction band of the porous photoelectrode 4 through the electrical coupling between the photosensitizing dye 8 and the porous photoelectrode 4 and pass through the porous photoelectrode 4 to form a transparent electrode. 2 is reached.

On the other hand, the photosensitizing dye 8 that has lost electrons is converted from the reducing agent in the electrolyte layer 12, for example, I ⁻ to the following reaction 2I ⁻ → I ₂ + 2e ^-
I ₂ + I ^- → I ₃ ^-
To receive electrons and produce an oxidant, for example I ₃ ⁻ , in the electrolyte layer 12. 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 ^-
Then, electrons are received from the counter electrode 5 and reduced to the original reducing agent.

  The electrons flowing out from the transparent electrode 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 8 or the electrolyte layer 12.

  On the other hand, the incident light transmitted without being absorbed by the photosensitizing dye 8 carried on the porous photoelectrode 4 is scattered by the light reflecting particle layer 7, and the scattered photons are incident on the porous photoelectrode 4 again. Thus, light energy is converted into electric energy in the same manner as described above. Further, the light transmitted without being reflected by the light reflecting particle layer 7 is scattered by the light scattering particles 23 in the electrolyte layer 12. At this time, since the light scattering particles 23 having an anisotropic shape are oriented so that the major axis is approximately parallel to the surface of the counter electrode 5, light in a wide wavelength range is effectively scattered. The scattered photons are incident on the porous photoelectrode 4 again, and the light energy is converted into electric energy as described above.

  According to the fourth embodiment, in addition to the same advantages as those of the first embodiment, the following advantages can be obtained. That is, the electrolyte layer 12 includes spacer fine particles 18 that are spherical and have an average diameter that is greater than or equal to the minor axis of the light scattering particles 23 and less than or equal to the major axis. The electrolyte layer 12 is thinly formed so as to be a spacer, and the light scattering particles 23 are oriented so that the major axis is approximately parallel to the surface of the counter electrode 5, so that the light scattering particles 23 are randomly oriented. The transmitted light can be efficiently scattered and returned into the porous photoelectrode 4, thereby increasing the light utilization rate.

Although the embodiments and examples of the present invention have been specifically described above, the present technology is not limited to the above-described embodiments and examples, and various modifications based on the technical idea of the present disclosure. Is possible.
For example, the numerical values, structures, configurations, shapes, materials, and the like given in the above-described embodiments and examples are merely examples, and different numerical values, structures, configurations, shapes, materials, etc. are used as necessary. Also good.

  DESCRIPTION OF SYMBOLS 1, 31 ... Transparent substrate, 2, 32 ... Transparent electrode, 3, 33 ... Semiconductor fine particle, 4, 34 ... Porous photoelectrode, 5, 35 ... Counter electrode, 6, 36 ... High refractive material particle, 7, 37 ... Light Reflective particle layer, 8, 38 ... Photosensitizing dye, 9, 39 ... Counter substrate, 10, 20, 40 ... Dye-sensitized photoelectric conversion device, 11, 41 ... Transparent conductive layer, 12, 42 ... Electrolyte layer, 13, 13a, 13b, 23, 43 ... light scattering particles, 14 ... photosensitizing dye adsorption preventing layer

Claims (13)

It has a structure in which an electrolyte layer is filled between a porous photoelectrode adsorbed with a photosensitizing dye and a counter electrode,
In a state of being dispersed in the electrolyte layer, light scattering particles provided with a photosensitizing dye adsorption prevention layer on at least a part of the surface are included ,
The photosensitizing dye adsorption-preventing layer is composed of a compound covering the surface of the light scattering particles.
Dye-sensitized photoelectric conversion device. The refractive index of the light scattering particles is 0.3 or more larger than the refractive index of the electrolyte layer ,
The dye-sensitized photoelectric conversion device according to claim 1. The electrolyte layer is made of a gel electrolyte .
The dye-sensitized photoelectric conversion device according to claim 1 or 2 . The light scattering particles have an anisotropic shape ,
The dye-sensitized photoelectric conversion device according to any one of claims 1 to 3 . The light scattering particles are made of titanium oxide ,
The dye-sensitized photoelectric conversion device according to any one of claims 1 to 4 . The light scattering particles have a particle size in the range of 0.15 μm to 0.45 μm .
The dye-sensitized photoelectric conversion device according to any one of claims 1 to 3 . The porous photoelectrode is composed of fine particles made of a semiconductor .
The dye-sensitized photoelectric conversion device according to any one of claims 1 to 6 . The fine particles made of the semiconductor are anatase-type titanium oxide .
The dye-sensitized photoelectric conversion device according to claim 7 . The compound is 1-decylphosphonic acid ,
The dye-sensitized photoelectric conversion device according to any one of claims 1 to 8 . The electrolyte layer is filled between the porous photoelectrode and the counter electrode, it has a step of incorporating in a state in which light scattering particles are dispersed forming a photosensitizing dye adsorption preventive layer on at least a portion of the surface,
The photosensitizing dye adsorption preventing layer is formed by encapsulating the light scattering particles with a compound.
A method for producing a dye-sensitized photoelectric conversion device. The light scattering particles are made of titanium oxide .
The manufacturing method of the dye-sensitized photoelectric conversion apparatus of Claim 10 . The compound is 1-decylphosphonic acid ,
The manufacturing method of the dye-sensitized photoelectric conversion apparatus of Claim 10 or Claim 11 . Having at least one photoelectric conversion device;
The photoelectric conversion device is
It has a structure in which an electrolyte layer is filled between the porous photoelectrode and the counter electrode,
In a state of being dispersed in the electrolyte layer, light scattering particles provided with a photosensitizing dye adsorption prevention layer on at least a part of the surface are included ,
The photosensitizing dye adsorption-preventing layer is composed of a compound covering the surface of the light scattering particles.
Electronic equipment that is a dye-sensitized photoelectric conversion device.

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