JP2013251229A - Photoelectric conversion element and dye-sensitized solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element capable of reducing costs and improving short circuit current density.SOLUTION: In a photoelectric conversion element, a photoelectric conversion layer having a porous semiconductor layer, a collector electrode supported by a translucent supporting body and contacting with a part of the photoelectric conversion layer, a charge transport layer, and counter electrode are sequentially provided on a translucent supporting body. A reflective layer is provided between the photoelectric conversion element and the collector electrode. The reflective layer contacts with at least a part of a part except the part contacting with the collector electrode among the photoelectric conversion layer, and is covered by the collector electrode.

Description

  The present invention relates to a photoelectric conversion element and a dye-sensitized solar cell.

  As an alternative energy source to fossil fuels, solar cells that convert solar energy into electric energy have attracted attention. Currently, solar cells using crystalline silicon substrates, thin-film silicon solar cells, and the like have been put into practical use. However, the former solar cell has a problem that the manufacturing cost of the silicon substrate is high. The latter thin film silicon solar cell has a problem that the manufacturing cost is high because it is manufactured using various semiconductor manufacturing gases and complicated apparatuses. For this reason, although efforts have been made to reduce the cost per power generation output by increasing the efficiency of photoelectric conversion in any of the solar cells, the above problem has not been solved.

  As a new type of solar cell, a solar cell including a photoelectric conversion element using photoinduced electron transfer of a metal complex has been proposed (for example, Patent Document 1). In the photoelectric conversion element described in Patent Document 1, a photoelectric conversion layer that adsorbs a photosensitizing dye and has an absorption spectrum in a visible light region and an electrolytic solution are sandwiched between two glass substrates. A first electrode and a second electrode are formed on the surface of the glass substrate.

  When light is irradiated from the first electrode side, electrons are generated in the photoelectric conversion layer, and the generated electrons move from one first electrode to the opposing second electrode through an external electric circuit. The moved electrons are transported to ions in the electrolyte and return to the photoelectric conversion layer. Electrical energy can be extracted by such a series of electron movements. However, since the photoelectric conversion element uses a glass plate with a transparent conductive film, the cost of the entire dye-sensitized solar cell is affected by the cost of the transparent conductive film, and further cost reduction is becoming the limit.

  Under such circumstances, a solar cell including a photoelectric conversion element described in Patent Document 2 has been proposed as a new cell-shaped solar cell for a conventional dye-sensitized solar cell. In the photoelectric conversion element described in Patent Document 2, a transparent conductive film on the light incident side is not used, and a current collecting electrode is formed on a porous semiconductor layer on which a dye is supported. Electrons are taken out from

Japanese Patent Laid-Open No. 01-220380 JP 2001-283941 A

  In the photoelectric conversion element described in Patent Document 2, since a transparent conductive film is not used, cost reduction is expected. In addition, since there is no light absorption loss due to the transparent conductive film, the light transmittance from the light incident side is increased, and thus the current is expected to be improved. However, a photoelectric conversion element that does not use a transparent conductive film has a problem that a short-circuit current density (Jsc) is lower than a photoelectric conversion element that uses a transparent conductive film.

  This invention is made | formed in view of this point, The place made into the objective is providing the photoelectric conversion element which can anticipate cost reduction and the short circuit current density improved.

  The present inventors diligently studied to realize a highly efficient photoelectric conversion element that does not use a transparent conductive film. If a reflective layer is provided at a part of the interface between the collector electrode and the photoelectric conversion layer, the photoelectric conversion is performed. The inventors have found that the short-circuit current density of the device is improved, and have completed the present invention.

  Specifically, in the photoelectric conversion element of the present invention, a photoelectric conversion layer having a porous semiconductor layer on a translucent support, and a collector that is supported by the translucent support and is in contact with a part of the photoelectric conversion layer. An electric electrode, a charge transport layer, and a counter electrode are provided in this order. A reflective layer is provided between the photoelectric conversion layer and the current collecting electrode. The reflective layer is in contact with at least a portion of the photoelectric conversion layer other than the portion with which the collector electrode is in contact, and is covered with the collector electrode.

  The thickness of the current collecting electrode located between the photoelectric conversion layer and the charge transport layer is preferably thinner than the thickness of the reflective layer.

  The reflective layer preferably contains particles having an average particle size larger than the average particle size of the particles constituting the porous semiconductor layer.

  The reflective layer and the porous semiconductor layer are preferably made of a compound semiconductor material. Here, the compound semiconductor material means a semiconductor material in which plural kinds of elements are bonded to each other.

  The photoelectric conversion layer preferably includes a porous semiconductor layer, and a photosensitizer and a carrier transport material provided in the porous semiconductor layer.

  The dye-sensitized solar cell of the present invention includes the photoelectric conversion element of the present invention.

  According to the photoelectric conversion element of the present invention, cost reduction can be expected and an improvement in short-circuit current density can be expected.

It is sectional drawing which shows an example of a structure of the photoelectric conversion element of this invention. It is sectional drawing which shows an example of a structure of the conventional photoelectric conversion element. It is a top view which shows an example of a structure of the reflection layer in the photoelectric conversion element of this invention. It is a top view which shows another example of a structure of the reflection layer in the photoelectric conversion element of this invention. It is a top view which shows another example of a structure of the reflection layer in the photoelectric conversion element of this invention. 3 is a plan view showing a configuration of a reflective layer of Example 1. FIG. (A)-(b) is a top view which shows the method of forming the reflective layer of Example 3. FIG.

  Hereinafter, the photoelectric conversion element of the present invention will be described with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

<Photoelectric conversion element>
FIG. 1 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion element according to the present invention. In the photoelectric conversion element shown in FIG. 1, a photoelectric conversion layer 2 having a porous semiconductor layer on a translucent support 1, and a collector supported by the translucent support 1 and in contact with a part of the photoelectric conversion layer 2 The electric electrode 4, the charge transport layer 5, the counter electrode 6, and the counter electrode support body 7 are provided in this order. In the photoelectric conversion element shown in FIG. 1, the photoelectric conversion layer 2 and the charge transport layer 5 are preferably sealed with a sealing portion 8. As described above, since the transparent conductive film is not provided in the photoelectric conversion element illustrated in FIG. 1, the manufacturing cost of the photoelectric conversion element can be reduced.

  In the photoelectric conversion element shown in FIG. 1, when the translucent support 1 is used as a light receiving surface, light passes through the translucent support 1 and enters the photoelectric conversion layer 2, and electrons are generated in the photoelectric conversion layer 2. Is done. The generated electrons are taken out of the photoelectric conversion element through the collector electrode 4 and moved to the counter electrode 6 through the external electric circuit. The electrons moved to the counter electrode 6 move in the charge transport layer 5 and the current collecting electrode 4 and return to the photoelectric conversion layer 2.

  On the other hand, when the counter electrode support 7 is used as a light receiving surface, light passes through the counter electrode support 7, the counter electrode 6, the charge transport layer 5, and the collector electrode 4 and is incident on the photoelectric conversion layer 2. Is generated. The generated electrons are taken out of the photoelectric conversion element through the collector electrode 4 and moved to the counter electrode 6 through the external electric circuit. The electrons moved to the counter electrode 6 move in the charge transport layer 5 and the current collecting electrode 4 and return to the photoelectric conversion layer 2. In this case, the counter electrode 6 and the current collecting electrode 4 are preferably made of a translucent material. Further, when the counter electrode 6 and the current collecting electrode 4 are not excellent in translucency, a reflection mirror or the like is provided on the back surface of the translucent support 1 (the upper surface of the translucent support 1 in FIG. 1). The light can be collected from the back surface of the translucent support 1 to generate electric power.

  In the photoelectric conversion element shown in FIG. 1, a reflective layer 3 is provided between the photoelectric conversion layer 2 and the current collecting electrode 4. The reflective layer 3 is in contact with at least a portion of the photoelectric conversion layer 2 other than the portion with which the collector electrode 4 is in contact, and is covered with the collector electrode 4. Thus, since the current collecting electrode 4 is in contact with not only the reflective layer 3 but also the photoelectric conversion layer 2, the short-circuit current density can be increased.

  Specifically, the present inventors have intensively studied the reason why the internal short-circuit component increases and the reason why the short-circuit current density decreases in the photoelectric conversion element shown in FIG. Here, FIG. 2 is a cross-sectional view showing an example of the configuration of a conventional photoelectric conversion element.

  In the photoelectric conversion element shown in FIG. 2, the reflective layer 23 is uniformly formed in a layer shape between the photoelectric conversion layer 2 and the current collecting electrode 24. Here, electrons hardly flow through the reflective layer 23. For this reason, in the photoelectric conversion element shown in FIG. 2, electrons hardly move between the photoelectric conversion layer 2 and the current collecting electrode 24, so that the internal resistance component of the photoelectric conversion element increases. Thereby, a short circuit current density falls.

  However, in the photoelectric conversion element shown in FIG. 1, the collector electrode 4 is in contact with not only the reflective layer 3 but also the photoelectric conversion layer 2 as described above. Therefore, in the photoelectric conversion element shown in FIG. 1, compared to the photoelectric conversion element shown in FIG. 2, electrons generated in the photoelectric conversion layer 2 move quickly from the photoelectric conversion layer 2 to the current collecting electrode 4. The short circuit current density increases.

  In the photoelectric conversion element shown in FIG. 1, the reflective layer 3 is provided between the photoelectric conversion layer 2 and the current collecting electrode 4 with a gap. For this reason, in the photoelectric conversion element shown in FIG. 1, there is a portion where the photoelectric conversion layer 2 and the collecting electrode 4 are in contact with each other without sandwiching the reflective layer 3, so that electrons generated in the photoelectric conversion layer 2 are converted into the photoelectric conversion layer 2. It becomes easy to move from to the current collecting electrode 4. Thereby, the increase in the internal resistance component of the photoelectric conversion element is suppressed, and the short-circuit current density of the photoelectric conversion element further increases.

  Further, the reflective layer 3 has a function of scattering the light incident on the reflective layer 3 and causing it to enter the photoelectric conversion layer 2. Therefore, in the photoelectric conversion element shown in FIG. 1, the light scattered by the reflection layer 3 is reabsorbed by the photoelectric conversion layer 2. Thereby, the number of electrons produced | generated in the photoelectric converting layer 2 becomes large compared with the case where the reflection layer is not provided. Since the current collecting electrode 4 is also in contact with the photoelectric conversion layer 2, more electrons can be quickly moved to the current collecting electrode 4. Therefore, the further increase in the short circuit current density of a photoelectric conversion element can be aimed at. Below, the structural member of the photoelectric conversion element which concerns on this invention is each demonstrated.

<Translucent support>
The material which comprises the translucent support body 1 will not be specifically limited if it is a material which can generally be used for the support body of a photoelectric conversion element, and can exhibit the effect of this invention. However, since light transmissivity is required in the portion that becomes the light receiving surface of the photoelectric conversion element, the translucent support 1 is preferably made of a material having light transmissivity, such as soda glass, fused silica glass, Alternatively, it may be a glass substrate such as crystalline quartz glass, or may be a flexible film made of a heat resistant resin material. However, even when the translucent support 1 is used as a light-receiving surface, at least light having a wavelength having an effective sensitivity to a photosensitizer described later is substantially transmitted (transmission of the light). The ratio is, for example, 80% or more, preferably 90% or more), and does not necessarily have transparency to light of all wavelengths.

  Examples of the material constituting the flexible film (hereinafter referred to as “film”) include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polycarbonate (PC), and polyarylate (PA). , Polyetherimide (PEI), phenoxy resin, or Teflon (registered trademark).

  When forming another layer on the translucent support 1 with heating, for example, when forming a porous semiconductor layer on the translucent support 1 with heating at about 250 ° C., Among the materials constituting the film, it is particularly preferable to use Teflon (registered trademark) having heat resistance of 250 ° C. or higher.

  The translucent support 1 can be used when the completed photoelectric conversion element is attached to another structure. That is, the peripheral part of the translucent support body 1 which consists of a glass substrate etc. can be easily attached to another support body using a metal processing component and a screw.

  The thickness of the translucent support 1 is not particularly limited, and is preferably about 0.2 to 5 mm, for example.

<Photoelectric conversion layer>
The photoelectric conversion layer 2 has a porous semiconductor layer. It is preferable that a photosensitizer and a carrier transport material are provided in the porous semiconductor layer. Each will be described in turn below.

-Porous semiconductor layer-
In the present invention, the porous semiconductor layer is composed of a semiconductor material. Here, the porosity means that the specific surface area is 0.5 to 300 m ² / g, and that the porosity is 20% or more. Such a specific surface area is obtained by the BET method which is a gas adsorption method, and the porosity is obtained by calculation from the thickness of the porous semiconductor layer, the mass of the porous semiconductor layer, and the density of the semiconductor fine particles. Since the porous semiconductor layer has a specific surface area of 0.5 to 300 m ² / g, it can adsorb many photosensitizers, and thus can absorb sunlight efficiently. Further, by setting the porosity of the porous semiconductor layer to 20% or more, the carrier transport material can be sufficiently diffused, and the electrons can be smoothly returned to the photoelectric conversion layer 2.

The material which comprises a porous semiconductor layer will not be specifically limited if it is a material which can generally be used for a photoelectric conversion element, and can exhibit the effect of this invention. Such materials include, for example, titanium oxide, zinc oxide, tin oxide, iron oxide, niobium oxide, cerium oxide, tungsten oxide, barium titanate, strontium titanate, cadmium sulfide, lead sulfide, zinc sulfide, indium phosphide, A compound semiconductor material such as copper-indium sulfide (CuInS ₂ ), CuAlO ₂ , or SrCu ₂ O ₂ is preferable. As the material constituting the porous semiconductor layer, one of the above listed materials may be used alone, or two or more of the above listed materials may be used in combination. From the viewpoint of photoelectric conversion efficiency, stability and safety, it is preferable to use titanium oxide as a material constituting the porous semiconductor layer.

  In the present invention, when titanium oxide is used as the material constituting the porous semiconductor layer, the titanium oxide to be used is various types such as anatase type titanium oxide, rutile type titanium oxide, amorphous titanium oxide, metatitanic acid, or orthotitanic acid. Titanium oxide in a narrow sense may be used, titanium hydroxide may be used, and hydrous titanium oxide may be used. These titanium oxides may be used alone or in combination. Anatase-type titanium oxide and rutile-type titanium oxide can be in either form depending on the production method or thermal history, but anatase-type titanium oxide is common. From the viewpoint of easy adsorption of the photosensitizer, it is preferable to use a material having a high content of anatase-type titanium oxide as the material constituting the porous semiconductor layer, and a content of the anatase-type titanium oxide is 80. It is more preferable to use what is% or more. The method for producing titanium oxide is not particularly limited, and may be a known method described in various literatures such as a gas phase method or a liquid phase method (hydrothermal synthesis method or sulfuric acid method). Degussa A method developed by the company to obtain chloride by high-temperature hydrolysis may be used.

  The form of the porous semiconductor layer may be either single crystal or polycrystal. However, in terms of stability, difficulty in crystal growth, and manufacturing cost, the porous semiconductor layer is preferably a polycrystalline sintered body, and is a polycrystalline sintered body made of fine powder (nanoscale to microscale). Particularly preferred is a ligation.

  The porous semiconductor layer may be composed of particles made of compound semiconductor materials having the same size, or may be composed of particles made of compound semiconductor materials having different sizes. Since relatively large particles scatter incident light, it is considered that they contribute to an improvement in the light capture rate. If relatively small particles are used, the number of adsorption points of the photosensitizer is increased. Therefore, it is considered that relatively small particles contribute to an improvement in the adsorption amount of the photosensitizer.

  The average particle size of relatively large particles is preferably 10 times or more than the average particle size of relatively small particles. For example, the average particle size of relatively large particles is preferably 100 to 500 nm, and the average particle size of relatively small particles is preferably 5 to 50 nm. The particles having different sizes may be made of the same material or different materials. When particles having different sizes are made of different materials, it is preferable that relatively small particles are made of a material having a strong adsorption action. The average particle diameter may be calculated using a spectrum (XRD (X-ray diffraction) diffraction peak) obtained from X-ray diffraction measurement, or directly observed with a scanning electron microscope (SEM). May be required.

The thickness of the porous semiconductor layer is not particularly limited, and for example, about 0.1 to 100 μm is appropriate. Further, since the photosensitizer is adsorbed on the porous semiconductor layer, the surface area of the porous semiconductor layer is preferably large. For example, the BET specific surface area of the porous semiconductor layer is about 10 to 200 m ² / g. Is preferred.

-Method for forming porous semiconductor layer-
It does not specifically limit as a method of forming a porous semiconductor layer, A well-known method is mentioned. For example, there is a method in which a suspension containing particles made of any one of the above compound semiconductor materials is applied on the translucent support 1 and then at least one of drying and baking is performed.

  In this method, first, fine particles made of any one of the above compound semiconductor materials are suspended in a suitable solvent to obtain a suspension. Examples of such a solvent include glyme solvents such as ethylene glycol monomethyl ether, alcohols such as isopropyl alcohol, alcohol-based mixed solvents such as isopropyl alcohol / toluene, and water. Further, instead of such a suspension, a commercially available titanium oxide paste (for example, manufactured by Solaronix, Ti-nanoxide, T, D, T / SP, D / SP, R / SP) may be used.

  Subsequently, the obtained suspension is applied onto the translucent support 1 by a known method such as a doctor blade method, a squeegee method, a spin coating method, or a screen printing method, and at least one of drying and baking is performed. To form a porous semiconductor layer.

  It is preferable that the temperature, time, atmosphere, and the like necessary for drying and firing are appropriately set according to the type of material that constitutes the porous semiconductor layer. For example, the atmosphere includes an air atmosphere or an inert gas atmosphere, and the temperature and time include a range of about 50 to 800 ° C. and a time of about 10 seconds to 12 hours. This drying and baking may be performed once at a single temperature, or may be performed twice or more by changing the temperature.

  In the case where the porous semiconductor layer is composed of a plurality of layers, it is preferable to prepare a suspension containing particles made of different materials, and the application of the prepared suspension and at least one of drying and baking are performed. It is preferable to repeat it more than once.

  After forming the porous semiconductor layer, the electrical connection between the fine particles made of the material constituting the porous semiconductor layer is improved, the surface area of the porous semiconductor layer is increased, and the fine particles made of the material constituting the porous semiconductor layer For the purpose of reducing the defect level, the porous semiconductor layer may be treated with a predetermined liquid. The method for treating the porous semiconductor layer depends on the material constituting the porous semiconductor layer and cannot be generally stated. However, when the porous semiconductor layer is made of titanium oxide, the titanium oxide film is formed with a titanium tetrachloride aqueous solution or the like. A surface treatment is preferred.

-Photosensitizer-
The sensitizing dye that is adsorbed on the porous semiconductor layer and functions as a photosensitizer is not particularly limited, but various organic dyes that can absorb light in at least one of the visible light region and the infrared light region. There may be various metal complex dyes capable of absorbing light in at least one of the visible light region and the infrared light region. These pigments may be used alone or in combination of two or more.

  Examples of organic dyes include azo dyes, quinone dyes, quinone imine dyes, quinacridone dyes, squarylium dyes, cyanine dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes, porphyrin dyes, and perylenes. And dyes such as indigo dyes and naphthalocyanine dyes. In general, the extinction coefficient of an organic dye is larger than that of a metal complex dye in which a molecule is coordinated to a transition metal.

  As metal complex dyes, Cu, Ni, Fe, Co, V, Sn, Si, Ti, Ge, Cr, Zn, Ru, Mg, Al, Pb, Mn, In, Mo, Y, Zr, Nb, Sb, La, W, Pt, TA, Ir, Pd, Os, Ga, Tb, Eu, Rb, Bi, Se, As, Sc, Ag, Cd, Hf, Re, Au, Ac, Tc, Te, or Rh The thing of the form which the ligand coordinated to the metal atom is mentioned. The metal complex dye is preferably, for example, a porphyrin dye, a phthalocyanine dye, or a naphthalocyanine dye, more preferably a phthalocyanine dye or a ruthenium dye, and a ruthenium metal complex dye. More preferably.

  The metal complex dye is particularly preferably a ruthenium-based metal complex dye represented by chemical formulas (1) to (3). Examples of commercially available ruthenium-based metal complex dyes include trade name Ruthenium 535 dye, Ruthenium 535-bis TBA dye, or Ruthenium 620-1H3TBA dye manufactured by Solaronix.

  In order to strongly adsorb the sensitizing dye to the porous semiconductor layer, the sensitizing dye has a carboxyl group, alkoxy group, hydroxyl group, sulfonic acid group, ester group, mercapto group, or phosphonyl group in the molecule. It preferably has an interlock group. In general, the interlock group exists between the sensitizing dye and the porous semiconductor layer when the sensitizing dye is fixed to the porous semiconductor layer, and constitutes the excited state of the sensitizing dye and the porous semiconductor layer. It provides an electrical coupling that facilitates the transfer of electrons to and from the conduction band of the semiconductor material.

The adsorption amount of such a sensitizing dye is preferably 1 × 10 ⁻⁸ mol / cm ² or more and 1 × 10 ⁻⁶ mol / cm ² or less, preferably 5 × 10 ⁻⁸ mol / cm ² or more and 5 × 10. More preferably, it is ⁻⁷ mol / cm ² . If the adsorption amount of the photosensitizer is less than 1 × 10 ⁻⁸ mol / cm ² , the photoelectric conversion efficiency may be lowered. On the other hand, when the adsorption amount of the photosensitizer exceeds 1 × 10 ⁻⁶ mol / cm ² , there may be a problem that the open circuit voltage is lowered.

-Dye adsorption method-
A typical method for adsorbing a sensitizing dye to the porous semiconductor layer is, for example, a method in which the porous semiconductor layer is immersed in a solution in which the sensitizing dye is dissolved (hereinafter referred to as “dye adsorption solution”). As mentioned. At this time, if the dye adsorbing solution is heated, the effect of allowing the dye adsorbing solution to permeate deep into the fine pores of the porous semiconductor layer can be obtained.

Examples of the solvent for dissolving the sensitizing dye include alcohol, toluene, acetonitrile, tetrahydrofuran (THF), chloroform, and dimethylformamide. These solvents are usually preferably purified, and two or more types can be mixed and used. The concentration of the sensitizing dye in the dye adsorbing solution can be appropriately set according to conditions such as the type of the sensitizing dye to be used, the type of the solvent, and the dye adsorbing step, and is, for example, 1 × 10 ⁻⁵ mol / liter or more. Preferably there is. In order to improve the solubility of the sensitizing dye, it is preferable to prepare a dye adsorption solution while heating.

-Carrier transport material-
The carrier transport material is preferably a conductive material capable of transporting ions, as shown in <Charge transport layer> below, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a molten salt gel electrolyte. preferable. The carrier transport material contained in the porous semiconductor layer may be the same as the material constituting the charge transport layer 5 or may be different from the material constituting the charge transport layer 5.

  The method for providing the carrier transport material in the porous semiconductor layer is not particularly limited. For example, the porous semiconductor layer may be immersed in a solution containing a carrier transport material. The carrier transport material may be injected into the photoelectric conversion layer 2 after the counter electrode support 7 is bonded to the collector electrode 4 using the sealing portion 8. When the carrier transport material contained in the porous semiconductor layer is the same as the material constituting the charge transport layer 5, the carrier transport material is injected into a predetermined position, so that the charge transport layer 5 is formed and the carrier transport is performed at the same time. A method can be adopted in which the material is included in the porous semiconductor layer.

<Reflective layer>
The material constituting the reflective layer 3 is not particularly limited as long as it is a material that can generally be used for a photoelectric conversion element and can exhibit the effects of the present invention, and the materials listed as materials constituting the porous semiconductor layer. It is preferable that That is, the material constituting the reflective layer 3 is, for example, titanium oxide, zinc oxide, tin oxide, iron oxide, niobium oxide, cerium oxide, tungsten oxide, barium titanate, strontium titanate, cadmium sulfide. A compound semiconductor material such as lead sulfide, zinc sulfide, indium phosphide, copper-indium sulfide (CuInS ₂ ), CuAlO ₂ , or SrCu ₂ O ₂ is preferable. As a material constituting the reflective layer 3, one of the above listed materials may be used alone, or two or more of the above listed materials may be used in combination. From the viewpoint of photoelectric conversion efficiency, stability, and safety, it is preferable to use titanium oxide as a material constituting the reflective layer 3.

  In the present invention, when titanium oxide is used as the material constituting the reflective layer 3, the titanium oxide used is various narrow meanings such as anatase type titanium oxide, rutile type titanium oxide, amorphous titanium oxide, metatitanic acid, or orthotitanic acid. It may be titanium oxide, titanium hydroxide, or hydrous titanium oxide. These titanium oxides may be used alone or in combination. Anatase-type titanium oxide and rutile-type titanium oxide can be in either form depending on the production method or thermal history, but anatase-type titanium oxide is common. The method for producing titanium oxide is not particularly limited, and may be a known method described in various literatures such as a gas phase method or a liquid phase method (hydrothermal synthesis method or sulfuric acid method). Degussa A method developed by the company to obtain chloride by high-temperature hydrolysis may be used.

  The form of the reflective layer 3 may be either single crystal or polycrystal. However, in terms of stability, difficulty in crystal growth, and manufacturing cost, the reflective layer 3 is preferably a polycrystalline sintered body, and is a polycrystalline sintered body made of fine powder (nanoscale to microscale). The body is particularly preferred.

  The reflective layer 3 preferably includes particles having an average particle size larger than the average particle size of the particles constituting the porous semiconductor layer. As an example, the average particle size of the particles constituting the reflective layer 3 is preferably at least twice the average particle size of the particles constituting the porous semiconductor layer. It is more preferable that the average particle size is 3 to 20 times. In other words, when the average particle size of the particles constituting the porous semiconductor layer is 10 nm or more and 30 nm or less, the average particle size of the particles constituting the reflective layer 3 is preferably 30 nm or more and 600 nm or less. Thereby, the light which could not be absorbed by the photoelectric conversion layer 2 can be scattered. Therefore, since the optical path length of the light that could not be absorbed by the photoelectric conversion layer 2 is increased, the absorption of the light of the long wavelength light can be increased. In addition, since the light that could not be absorbed by the photoelectric conversion layer 2 can be scattered and reabsorbed by the photoelectric conversion layer 2, the amount of electrons generated in the photoelectric conversion layer 2 increases, and thus the photoelectric conversion The short circuit current density of the device further increases.

  When each of the porous semiconductor layer and the reflective layer 3 includes relatively small particles and relatively large particles, the average particle diameter of the relatively large particles in the reflective layer 3 is It is preferably larger than the average particle size of relatively large particles. For example, the average particle size of relatively large particles in the reflective layer 3 is preferably 2 times or more, more preferably 3 times or more 5 times the average particle size of relatively large particles in the porous semiconductor layer. Is less than double. In other words, when the average particle size of relatively large particles in the porous semiconductor layer is 50 nm or more and 500 nm or less, the average particle size of relatively large particles in the reflective layer 3 is 150 nm or more and 2500 nm or less. Is preferred. Even in this case, the above effects (that is, the effect of increasing the absorption of light of long wavelength light and the effect of further increasing the short-circuit current density of the photoelectric conversion element) can be obtained.

  When each of the porous semiconductor layer and the reflective layer 3 includes relatively small particles and relatively large particles, the ratio of relatively large particles in the reflective layer 3 (particles constituting the reflective layer 3) The ratio of the relatively large particles in the particles constituting the reflective layer 3 to the total number of particles is a ratio of relatively large particles in the porous semiconductor layer (the porous semiconductor relative to the total number of particles constituting the porous semiconductor layer) The ratio of the number of relatively large particles among the particles constituting the layer) may be higher. For example, the ratio of relatively large particles in the reflective layer 3 is preferably 2 times or more, more preferably 5 to 10 times the ratio of relatively large particles in the porous semiconductor layer. . Even in this case, the above effects (that is, the effect of increasing the absorption of light of long wavelength light and the effect of further increasing the short-circuit current density of the photoelectric conversion element) can be obtained.

  Here, when the reflective layer 3 includes relatively small particles and relatively large particles, the average particle size of the relatively large particles is more than 10 times the average particle size of the relatively small particles. Preferably there is. When the average particle size of the relatively large particle size is 100 to 500 nm, the average particle size of the relatively small particle size is preferably 5 to 50 nm. The relatively large particles and the relatively small particles may be made of the same material or different materials. The reflective layer 3 may be composed of particles having a single size. Moreover, the average particle diameter of the particles constituting the reflective layer 3 can be determined according to the same method as the method for measuring the average particle diameter of the particles constituting the porous semiconductor layer.

  The planar shape of the reflective layer 3 on the surface of the photoelectric conversion layer 2 located on the charge transport layer 5 side is not particularly limited. The reflective layer 3 may be arranged in a stripe shape as shown in FIG. 3 on the surface of the photoelectric conversion layer 2 located on the charge transport layer 5 side, or in a dot shape as shown in FIG. Alternatively, they may be arranged in a lattice pattern as shown in FIG. 3-5 is a top view which shows an example of a structure of the reflection layer in the photoelectric conversion element of this invention, respectively.

  The thickness of the reflective layer 3 is not particularly limited, but is preferably thicker than the thickness of the current collecting electrode 4 located between the photoelectric conversion layer 2 and the charge transport layer 5 as described later, for example, 0.2 nm or more It is preferable that it is 1000 micrometers or less. This will be described with reference to the collecting electrode 4 described later.

  The reflective layer 3 is provided between the photoelectric conversion layer 2 and the collector electrode 4, is in contact with the photoelectric conversion layer 2, and is covered with the collector electrode 4. Therefore, the reflective layer 3 is not in contact with the charge transport layer 5.

  Further, the number of the reflective layers 3 is not limited to the number shown in FIG. The current collecting electrode 4 is in contact with a part of the photoelectric conversion layer 2, and the reflection layer 3 is in contact with at least a part of the photoelectric conversion layer 2 other than the part in contact with the current collecting electrode 4 and the current collecting As long as it is covered with the electrode 4, the number of the reflective layers 3 may be one. However, if the reflective layer 3 is provided at intervals in the direction perpendicular to the thickness direction of the photoelectric conversion layer 2, electrons generated in the photoelectric conversion layer 2 are transferred from the photoelectric conversion layer 2 to the current collecting electrode 4. It is easy to secure a route to move to. Therefore, it is preferable that the reflective layer 3 is provided with a gap (for example, 0.2 μm or more and 1000 μm or less, preferably 1 μm or more and 500 μm or less) in a direction perpendicular to the thickness direction of the photoelectric conversion layer 2. .

-Method for forming the reflective layer-
The method for forming the reflective layer 3 is not particularly limited, and a known method similar to the method for forming the porous semiconductor layer may be used. For example, there may be mentioned a method in which a suspension containing particles made of any one of the above compound semiconductor materials is applied on a porous semiconductor layer and then dried and fired.

  In this method, first, fine particles made of any one of the above compound semiconductor materials are suspended in a suitable solvent to obtain a suspension. Examples of such a solvent include glyme solvents such as ethylene glycol monomethyl ether, alcohols such as isopropyl alcohol, alcohol-based mixed solvents such as isopropyl alcohol / toluene, and water. Further, instead of such a suspension, a commercially available titanium oxide paste (eg, Solaronix, Ti-nanoxide, T, D, T / SP, D / SP) may be used. Alternatively, a commercially available paste or commercially available particles may be mixed with the solvent to obtain a suspension, or a commercially available paste may be mixed with each other to obtain a suspension.

  At this time, it is preferable that the fine particles include particles larger than the average particle diameter of particles made of a material that constitutes the porous semiconductor layer. The relationship between the average particle diameter of the fine particles and the average particle diameter of the particles made of the material constituting the porous semiconductor layer, the specific size, and the like are as described above.

  Next, the obtained suspension is applied onto the porous semiconductor layer by a known method such as a doctor blade method, a squeegee method, a spin coating method, or a screen printing method, and at least one of drying and baking is performed and reflection is performed. Layer 3 is formed. Specifically, the reflective layer may be partially formed by using a screen having a predetermined pattern shape (screen printing method), or after the uniform formation of the reflective layer, laser scribe may be used to form one of the reflective layers. The portion may be removed. Thereby, for example, the reflective layer 3 shown in FIGS. 3 to 5 is formed.

  It is preferable that the temperature, time, atmosphere, and the like necessary for drying and firing are appropriately set according to the type of material constituting the reflective layer 3. For example, the atmosphere includes an air atmosphere or an inert gas atmosphere, and the temperature and time include a range of about 50 to 800 ° C. and a time of about 10 seconds to 12 hours. This drying and baking may be performed once at a single temperature, or may be performed twice or more by changing the temperature.

  When the reflective layer 3 is composed of a plurality of layers, it is preferable to prepare a suspension containing particles made of different materials, and the application of the prepared suspension and at least one of drying and baking are performed twice. It is preferable to repeat the above.

<Collector electrode>
In the present invention, the collecting electrode 4 is supported by the translucent support 1 and is in contact with not only the reflective layer 3 but also the photoelectric conversion layer 2. In addition, it is preferable that the current collecting electrode 4 is also provided outside the sealing portion 8 as shown in FIG. 1, so that the current collecting electrode 4 can be smoothly connected to the counter electrode 6 via an external electric circuit. Can be connected to.

  The current collecting electrode 4 preferably contains a carrier transport material, whereby the electrons moved to the counter electrode 6 can be smoothly moved to the photoelectric conversion layer 2. Here, the carrier transport material may be a conductive material capable of transporting ions as described in <Charge transport layer> below, and may be the same as the material constituting the charge transport layer 5, or the charge transport material. The material constituting the layer 5 may be different. The method for providing the carrier transporting material in the current collecting electrode 4 is not particularly limited, and the current collecting electrode 4 may be immersed in a solution containing the carrier transporting material, or the counter electrode support using the sealing portion 8. The carrier transport material may be injected into the current collecting electrode 4 after 7 is bonded to the current collecting electrode 4. Further, when the carrier transport material included in the current collecting electrode 4 is the same as the material constituting the charge transport layer 5, the charge transport layer 5 is formed at the same time as the carrier transport material is injected into a predetermined position. A method in which a carrier transport material is included in the current collecting electrode 4 can be employed.

The material constituting the current collecting electrode 4 is not particularly limited as long as it has conductivity, and may or may not have light transparency. However, in the case where the counter electrode support 7 is used as the light receiving surface, the light transmission is required as in the case of the light transmissive support 1. Moreover, it is preferable that the material which comprises the current collection electrode 4 does not have corrosivity with respect to carrier transport materials (electrolyte etc.). Specifically, the material constituting the current collecting electrode 4 is indium tin composite oxide (ITO), tin oxide (SnO ₂ ), tin oxide doped with fluorine (FTO), or zinc oxide (ZnO). A metal that does not exhibit corrosiveness to the carrier transport material such as titanium, nickel, or tantalum can also be used.

  Although the thickness of the current collection electrode 4 is not specifically limited, For example, it is preferable that it is about 0.02-50 micrometers. The thickness of the current collecting electrode 4 located between the photoelectric conversion layer 2 and the charge transport layer 5 is preferably thinner than the thickness of the reflective layer 3, for example, 1/10 or more times the thickness of the reflective layer 3. More preferably, it is not more than 2 times. In other words, when the thickness of the reflective layer 3 is 1 μm or more and 50 μm or less, the thickness of the collecting electrode 4 positioned between the photoelectric conversion layer 2 and the charge transport layer 5 is 0.1 μm or more and 25 μm or less. It is preferable that Thereby, absorption of the light by the current collection electrode 4 can be suppressed.

  The sheet resistance value of the current collecting electrode 4 is preferably as low as possible because FF (curve factor) can be improved, and particularly preferably 40Ω / □ or less.

  When the current collecting electrode 4 has a dense structure, it is preferable that a plurality of small holes are formed in the current collecting electrode 4. Here, the plurality of small holes function as paths for the carrier transport material. That is, the carrier transport material contained in the charge transport layer 5 can move between the porous semiconductor layer of the photoelectric conversion layer 2 and the counter electrode 6 through the inside of the plurality of small holes formed in the current collecting electrode 4. . The diameter of the small holes is preferably about 0.1 μm to 100 μm, and more preferably about 1 μm to 50 μm. The distance between the small holes is preferably about 1 μm to 200 μm, and more preferably about 10 μm to 300 μm. Such small holes are preferably formed by physical contact or laser processing. If it is difficult to form a small hole, a striped opening may be formed in the current collecting electrode 4. Thereby, the same effect as the case where a small hole is formed is acquired. The interval between the stripe-shaped openings is preferably about 1 μm to 200 μm, and more preferably about 10 μm to 300 μm.

  The formation method of the current collection electrode 4 is not specifically limited. For example, the reflective layer 3 is covered with the collector electrode 4 by a known method such as a sputtering method or a spray method, and on the surface of the photoelectric conversion layer 2 exposed from the reflective layer 3 and on the sealing portion 8. It is preferable to form the current collecting electrode 4.

<Charge transport layer>
In the present invention, the “charge transport layer” is configured by filling a space surrounded by the translucent support 1, the counter electrode support 7, and the sealing portion 8 with a carrier transport material. . The carrier transport material is preferably composed of a conductive material capable of transporting ions. Examples of suitable materials for the carrier transport material include a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a molten salt gel electrolyte. .

  The liquid electrolyte is preferably a liquid containing redox species, and is not particularly limited as long as it can be used in a battery or a solar battery. Specifically, the liquid electrolyte includes a redox species and a solvent capable of dissolving the redox species, a redox species and a molten salt capable of dissolving the redox species, or a redox species. What consists of the said solvent and the said molten salt is mentioned.

Examples of the redox species include I ⁻ / I ³⁻ , Br ²⁻ / Br ^{3 −} , Fe ²⁺ / Fe ³⁺ , or quinone / hydroquinone. Specifically, the redox species include metal iodide such as lithium iodide (LiI), sodium iodide (NaI), potassium iodide (KI), or calcium iodide (CaI ₂ ) and iodine (I ₂ ). It may be a combination. The redox species includes tetraalkylammonium iodide (TEAI), tetrapropylammonium iodide (TPAI), tetrabutylammonium iodide (TBAI), or tetraalkylammonium iodide (THAI) and iodine. It may be a combination. The redox species may be a combination of bromide with a metal bromide such as lithium bromide (LiBr), sodium bromide (NaBr), potassium bromide (KBr), or calcium bromide (CaBr ₂ ). Among these, a combination of LiI and I ₂ is particularly preferable.

  Examples of the solvent capable of dissolving the redox species include carbonate compounds such as propylene carbonate, nitrile compounds such as acetonitrile, alcohols such as ethanol, water, and aprotic polar substances. Among these, carbonate compounds or nitrile compounds are particularly preferable. Two or more kinds of these solvents can be mixed and used.

  The solid electrolyte is a conductive material that can transport electrons, holes, or ions, and can be used as an electrolyte for a photoelectric conversion element and has no fluidity. Specifically, a solid electrolyte includes a hole transport material such as polycarbazole, an electron transport material such as tetranitrofluororenone, a conductive polymer such as polyroll, a polymer electrolyte obtained by solidifying a liquid electrolyte with a polymer compound, iodine Examples thereof include p-type semiconductors such as copper halide and copper thiocyanate, or electrolytes obtained by solidifying liquid electrolytes containing molten salts with fine particles.

  The gel electrolyte is usually composed of an electrolyte and a gelling agent. The electrolyte may be, for example, the liquid electrolyte or the solid electrolyte.

  Examples of the gelling agent include polymer gels such as cross-linked polyacrylic resin derivatives, cross-linked polyacrylonitrile derivatives, polyalkylene oxide derivatives, silicone resins, or polymers having a nitrogen-containing heterocyclic quaternary compound salt structure in the side chain. And the like.

The molten salt gel electrolyte is usually composed of the gel electrolyte as described above and a room temperature molten salt.
Examples of the room temperature molten salt include nitrogen-containing heterocyclic quaternary ammonium salts such as pyridinium salts and imidazolium salts.

  The charge transport layer may contain the following additives as required. The additive may be a nitrogen-containing aromatic compound such as t-butylpyridine (TBP), dimethylpropylimidazole iodide (DMPII), methylpropylimidazole iodide (MPII), ethylmethylimidazole iodide ( It may be an imidazole salt such as EMII), ethylimidazole iodide (EII), or hexylmethylimidazole iodide (HMII).

  The concentration of the electrolyte is preferably in the range of 0.001 to 1.5 mol / liter, and particularly preferably in the range of 0.01 to 0.7 mol / liter. However, when the photoelectric conversion element according to the present invention has a catalyst layer (counter electrode 6) on the light receiving surface side, incident light passes through the electrolytic solution in the charge transport layer 5 and is a porous semiconductor in which a dye is adsorbed. Reach the layer. Thereby, a carrier is excited.

<Counter electrode>
The counter electrode 6 is provided on the counter electrode support 7 and is in contact with the charge transport layer 5. The counter electrode 6 is a pole on the opposite side to the collecting electrode 4. The material constituting the counter electrode 6 may be the same as the material constituting the current collecting electrode 4, or is preferably made of a light transmissive material when the counter electrode support 7 is a light receiving surface.

  The counter electrode 6 is preferably a laminate of a catalyst layer and a conductive layer. Here, the catalyst layer is preferably provided between the charge transport layer 5 and the conductive layer, and preferably has a function of activating the oxidation-reduction reaction of the electrolyte, such as platinum, carbon black, kettle. It is preferably made of chain black, carbon nanotube, fullerene or the like. In addition, when the catalyst layer has conductivity as described above, the counter electrode 6 may be formed only of the catalyst layer.

  The counter electrode 6 may be the same as the method for forming the current collecting electrode 4. When platinum is used as the counter electrode 6, the counter electrode 6 can be formed on the counter electrode support 7 by a known method such as sputtering, thermal decomposition of chloroplatinic acid, or electrodeposition. The thickness of the counter electrode 6 is not specifically limited, For example, about 0.5 nm-1000 nm are suitable.

  When carbon such as carbon black, ketjen black, carbon nanotube, or fullerene is used as a material constituting the counter electrode 6, the counter electrode 6 is formed by a screen printing method in which carbon dispersed in a solvent is pasted. The method of apply | coating on the counter electrode support body 7 can be used.

<Counter electrode support>
The counter electrode support 7 supports the counter electrode 6. The material which comprises the counter electrode support body 7 will not be specifically limited if it is a material which can generally be used for the support body of a photoelectric conversion element, and can exhibit the effect of this invention. When the counter electrode support 7 is used as a light receiving surface, it needs to be light transmissive. Therefore, the counter electrode support 7 is preferably made of any of the materials listed in the above <Translucent support>. However, the counter electrode support 7 may basically have light transmission properties or may not have light transmission properties. The counter electrode support 7 may be, for example, a plate or a film made of an inorganic material such as a metal, or a plate or a film made of an organic material such as a plastic when light transparency is not required. .

  As with the translucent support 1, the counter electrode support 7 can be used when the completed photoelectric conversion element is attached to another structure. That is, the peripheral part of the counter electrode support body 7 can be easily attached to another support body using a metal processed part and a screw.

  Although the thickness of the counter electrode support body 7 is not specifically limited, For example, it is preferable that it is about 0.2-5 mm.

<Sealing part>
The sealing portion 8 holds the translucent support 1 and the counter electrode support 7, has a function of preventing leakage of the charge transport layer 5, has a function of absorbing falling objects or stress (impact), and has a long-term It has a function of absorbing the deflection acting on each of the translucent support 1 and the counter electrode support 7 during the use.

  The material which comprises the sealing part 8 will not be specifically limited if it is a material which can generally be used for a photoelectric conversion element, and can demonstrate the above-mentioned function. Examples of such a material include an ultraviolet curable resin or a thermosetting resin, and specifically include a silicone resin, an epoxy resin, a polyisobutylene resin, a hot melt resin, or a glass frit. The sealing part 8 may be formed by using these alone, or the sealing part 8 may be formed by laminating two or more kinds of these materials in two or more layers.

  As the ultraviolet curable resin, model number: 31X-101 manufactured by Three Bond Co., Ltd. can be used. As the thermosetting resin, model number: 31X-088 manufactured by Three Bond Co., or a commercially available epoxy resin can be used.

  When silicone resin, epoxy resin, or glass frit is used as the material constituting the sealing portion 8, the pattern of the sealing portion 8 can be formed using a dispenser. In the case where a hot melt resin is used as a material constituting the sealing portion 8, the pattern of the sealing portion 8 can be formed by making a hole patterned in the sheet-like hot melt resin.

<Dye-sensitized solar cell>
The dye-sensitized solar cell according to the present invention includes an electrode including the photoelectric conversion element according to the present invention, a counter electrode, and carrier transport provided between the electrode including the photoelectric conversion element according to the present invention and the counter electrode. With layers. Thereby, the dye-sensitized solar cell with which the increase in a short circuit current density is anticipated can be provided.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. In the following, unless otherwise specified, the thickness of each layer was measured using a surface roughness shape measuring instrument (trade name: Dektak150, manufactured by Veeco).

<Example 1>
The photoelectric conversion element shown in FIG. 1 was produced. A glass substrate (Corning 7059) of 51 mm × 70 mm × thickness 1 mm was prepared as the translucent support 1.

<Formation of sealing part>
A screen plate having an opening width of 0.5 mm was placed on the glass substrate on which the insulating layer was formed and around the portion where the porous semiconductor layer was formed. A glass frit was applied on a glass substrate using a screen printing machine (Neurong Seimitsu Kogyo Co., Ltd., model: LS-34TVA), and leveling was performed for 1 hour at room temperature. The obtained coating film was pre-dried at 80 ° C. for 20 minutes and then baked at 450 ° C. for 1 hour. Thereby, the sealing part 8 was formed.

<Formation of porous semiconductor layer>
Screen plates were placed on the glass substrate at 1 cm intervals so that the size of the fired porous semiconductor layer was 5 mm × 5 mm × 12 μm. Titanium oxide paste (Solaronix, trade name: Ti-Nanoxide D / SP, average particle size 13 nm) is placed on a glass substrate using a screen printer (Neurong Seimitsu Kogyo Co., Ltd., Model: LS-34TVA). It was applied and leveled for 1 hour at room temperature.

  The obtained coating film was pre-dried at 80 ° C. for 20 minutes and then baked at 450 ° C. for 1 hour. Then, this series of steps was repeated twice. Thereby, a porous semiconductor layer made of titanium oxide was obtained.

<Formation of reflective layer>
A screen having a pattern having a stripe shape was disposed on the porous semiconductor layer. Titanium oxide paste (Solaronix, trade name: Ti-Nanoxide R / SP, average particle size of 100 nm or more) is applied on the porous semiconductor layer using the above screen printer and leveled at room temperature for 1 hour. Went.

  The obtained coating film was pre-dried at 80 ° C. for 20 minutes and then baked at 450 ° C. for 1 hour. The reflective layer 3 thus obtained had a planar shape shown in FIG. Specifically, six reflection layers 3 having a width of 0.5 mm are formed, the interval between the adjacent reflection layers 3 is 0.3 mm, and the interval between the reflection layer 3 located at the periphery and the end of the porous semiconductor layer. Was 0.25 mm. The thickness of the reflective layer 3 was 6 μm.

<Formation of current collecting electrode>
A metal mask having an opening of 6 mm × 10 mm was prepared. The prepared metal mask was placed on the glass substrate so that the upper surface of the porous semiconductor layer was exposed from the opening of the metal mask. Using an electron beam vapor deposition device ei-5 (manufactured by ULVAC, Inc.), a current collector electrode 4 made of titanium was formed with a target of titanium and a vapor deposition rate of 5 Å / S. The thickness of the current collecting electrode 4 was about 500 nm.

<Adsorption of sensitizing dye>
A mixed solvent (volume ratio of 1: 1) of acetonitrile (manufactured by Aldrich Chemical Company) and t-butyl alcohol (manufactured by Aldrich Chemical Company) was obtained. A sensitizing dye (manufactured by Solaronix, trade name: Ruthenium 620-1H3TBA) was dissolved in the above mixed solvent so that the concentration was 4 × 10 ⁻⁴ mol / liter. In this way, a dye adsorption solution was obtained.

  The glass substrate obtained in the above <formation of current collecting electrode> was cut into a desired size. The cut glass substrate was immersed in a dye adsorption solution at a temperature of 40 ° C. for 20 hours to adsorb the sensitizing dye to the porous semiconductor layer. The obtained laminate was washed with ethanol (manufactured by Aldrich Chemical Company) and dried at about 80 ° C. for about 10 minutes.

<Formation of counter electrode and counter electrode support>
A glass plate (manufactured by Nippon Sheet Glass Co., Ltd.) on which an SnO ₂ film was formed was prepared as the counter electrode support 7. Platinum was vapor-deposited on the surface of the glass plate to form a counter electrode 6 made of a platinum film having a thickness of 300 nm.

  An ultraviolet curing agent (manufactured by Three Bond Co., Ltd., model number: 31X-101) is applied on the sealing portion 8, and the counter electrode 6 and the collector electrode 4 are bonded using the ultraviolet curing agent applied on the sealing portion 8. Ultraviolet rays were irradiated after overlapping. As a result, the counter electrode 6 and the collecting electrode 4 were pasted together via the sealing portion 8.

<Preparation of charge transport material>
LiI (redox species, manufactured by Aldrich Chemical Company) is dissolved in acetonitrile as a solvent so that the concentration becomes 0.1 mol / liter, and I ₂ (oxidation-reduction) so that the concentration becomes 0.01 mol / liter. Seed, manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved. Further, t-butylpyridine (additive, TBP (4-tert-butylpyridine), manufactured by Aldrich Chemical Company) was dissolved in acetonitrile so as to have a concentration of 0.5 mol / liter, and the concentration was 0.6 mol / liter. Dimethylpropylimidazole iodide (DMPII, manufactured by Shikoku Chemicals Co., Ltd.) was dissolved so that Thereby, an electrolyte was obtained.

  After injecting the electrolyte from the electrolyte injection hole previously vacated in the counter electrode 6 and the counter electrode support 7, the electrolyte injection hole using an ultraviolet curable resin (manufactured by Three Bond, model number: 31X-101 229) Was sealed. Thereby, the photoelectric conversion element in the present Example 1 was obtained.

When the obtained photoelectric conversion element was irradiated with light having an intensity of 1 kW / m ² (AM1.5 solar simulator), the short-circuit current density was 15.0 mA / cm ² .

<Example 2>
A photoelectric conversion element of Example 2 was manufactured according to the same method as Example 1 except that 16 reflective layers 3 having a center interval of 1 mm and a diameter of 1 mm were formed.

When the obtained photoelectric conversion element was irradiated with light having an intensity of 1 kW / m ² (AM1.5 solar simulator), the short-circuit current density was 13.5 mA / cm ² .

<Example 3>
A photoelectric conversion element of Example 3 was manufactured according to the same method as in Example 1 except that the reflective layer shown in FIG. 5 was formed using two types of screens. Specifically, the reflective layer 3 shown in FIG. 7A was formed using the first screen, and then the reflective layer 3 shown in FIG. 7B was formed using the second screen. 7A to 7B are plan views showing a method for forming the reflective layer of Example 3. FIG.

When the obtained photoelectric conversion element was irradiated with light having an intensity of 1 kW / m ² (AM1.5 solar simulator), the short-circuit current density was 14.5 mA / cm ² .

<Example 4>
Example 1 except that 13 reflective layers having a width of 0.2 mm were formed by forming a reflective layer over the entire upper surface of the porous semiconductor layer and then scraping off part of the reflective layer by laser scribing. The photoelectric conversion device of Example 4 was manufactured according to the same method as described above.

When the obtained photoelectric conversion element was irradiated with light having an intensity of 1 kW / m ² (AM1.5 solar simulator), the short-circuit current density was 14.5 mA / cm ² .

<Comparative Example 1>
A photoelectric conversion element of Comparative Example 1 was produced in the same manner as in Example 4 except that a part of the reflective layer was not scraped off by laser scribing. That is, in the photoelectric conversion element of Comparative Example 1, the reflective layer was uniformly provided between the photoelectric conversion layer and the current collecting electrode.

When the obtained photoelectric conversion element was irradiated with light having an intensity of 1 kW / m ² (AM1.5 solar simulator), the short-circuit current density was 11.0 mA / cm ² .

<Discussion>
As described above, in Examples 1 to 4, the short-circuit current density was higher than that in Comparative Example 1. The reason is considered as follows. In Examples 1 to 4, since the current collecting electrode is in contact with not only the reflective layer but also the photoelectric conversion layer, electrons generated in the photoelectric conversion layer quickly move from the photoelectric conversion layer to the current collecting electrode. Thereby, the short circuit current density of a photoelectric conversion element increases. In addition, in Examples 1 to 4, since the reflective layer is provided with a gap between the photoelectric conversion layer and the current collecting electrode, the photoelectric conversion layer and the current collecting electrode are not sandwiched between the reflective layers. There is a contact point. For this reason, electrons generated in the photoelectric conversion layer easily move from the photoelectric conversion layer to the current collecting electrode. Thereby, the increase in the internal resistance component of the photoelectric conversion element is suppressed, and thus the short-circuit current density of the photoelectric conversion element further increases.

  On the other hand, in Comparative Example 1, since the current collecting electrode does not contact the photoelectric conversion layer, electrons generated in the photoelectric conversion layer are unlikely to move quickly from the photoelectric conversion layer to the current collecting electrode. Therefore, the short circuit current density of the photoelectric conversion element is reduced. In addition, the reflective layer is uniformly provided between the photoelectric conversion layer and the current collecting electrode. Here, electrons hardly flow through the reflective layer. Therefore, in Comparative Example 1, electrons do not easily move between the photoelectric conversion layer and the current collecting electrode, so that the internal resistance component of the photoelectric conversion element increases. This also causes a decrease in the short circuit current density of the photoelectric conversion element.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Translucent support body, 2 Photoelectric conversion layer, 3 Reflective layer, 4 Current collection electrode, 5 Charge transport layer, 6 Counter electrode, 7 Counter electrode support body, 8 Sealing part.

Claims (6)

On the translucent support, a photoelectric conversion layer having a porous semiconductor layer, a collector electrode supported by the translucent support and in contact with a part of the photoelectric conversion layer, a charge transport layer, and a counter electrode Is a photoelectric conversion element provided in order,
A reflective layer is provided between the photoelectric conversion layer and the collecting electrode,
The reflective layer is in contact with at least a portion of the photoelectric conversion layer other than the portion with which the current collecting electrode is in contact, and is covered with the current collecting electrode.   2. The photoelectric conversion element according to claim 1, wherein a thickness of the current collecting electrode positioned between the photoelectric conversion layer and the charge transport layer is thinner than a thickness of the reflective layer.   3. The photoelectric conversion element according to claim 1, wherein the reflective layer includes particles having an average particle size larger than an average particle size of particles constituting the porous semiconductor layer.   The photoelectric conversion element according to claim 1, wherein the reflective layer and the porous semiconductor layer are made of a compound semiconductor material.   The photoelectric conversion element according to claim 1, wherein the photoelectric conversion layer includes the porous semiconductor layer, and a photosensitizer and a carrier transport material provided in the porous semiconductor layer.   The dye-sensitized solar cell provided with the photoelectric conversion element in any one of Claims 1-5.

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