JP2014229434A - Photoelectric conversion element and dye-sensitized solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element that is expected to lower a cost and that has a high short circuit current density.SOLUTION: In a photoelectric conversion element, a photoelectric conversion layer with a porous semiconductor layer, a reflection layer, a collector electrode supported by a translucent supporting body, a charge transport layer, and a counter electrode are sequentially provided on the translucent supporting body. A surface located at the reflection layer side of the photoelectric conversion layer has a first uneven part. Each of the reflection layer and the collector electrode has an uneven shape corresponding to the first uneven part.

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 with a high short circuit current density which can anticipate cost reduction. Another object of the present invention is to provide a dye-sensitized solar cell that can be expected to reduce costs and has a high short-circuit current density.

  The present inventors diligently studied to realize a high-efficiency photoelectric conversion element that does not use a transparent conductive film, and found that if the shape of the photoelectric conversion layer is devised, the short-circuit current density of the photoelectric conversion element increases. The present invention has been completed.

  In the photoelectric conversion element according to the present invention, a photoelectric conversion layer having a porous semiconductor layer on a translucent support, a reflective layer, a current collecting electrode supported by the translucent support, and a charge transport layer And a counter electrode are provided in order. The surface located in the reflective layer side among photoelectric conversion layers has a 1st uneven part. Each of the reflective layer and the current collecting electrode has an uneven shape corresponding to the first uneven portion.

  The uneven shape of the reflective layer preferably has a thin portion provided in the first recess of the first uneven portion and a thick portion in contact with the first protrusion of the first uneven portion. The current collecting electrode preferably has a surface with a surface roughness Ra of 0.3 μm or more and 5 μm or less. The reflective layer preferably contains particles having an average particle size larger than the average particle size of the semiconductor particles contained in the porous semiconductor layer. It is preferable that a 1st uneven | corrugated | grooved part has a striped 1st recessed part and a striped 1st convex part.

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

  According to the present invention, it is possible to provide a photoelectric conversion element that can be expected to reduce costs and that has a high short-circuit current density.

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 the 1st uneven | corrugated | grooved part of this invention. It is a top view which shows another example of the 1st uneven | corrugated | grooved part of this invention. It is a top view which shows another example of the 1st uneven | corrugated | grooved part of this invention. It is a top view which shows another example of the 1st uneven | corrugated | grooved part of this invention.

  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, a reflective layer 3, and a collecting electrode 4 supported by the translucent support 1 are formed on the translucent support 1. The charge transport layer 5 and the counter electrode 6 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 by a sealing portion 8, and the counter electrode 6 is preferably supported by a counter electrode support 7. Thus, since the photoelectric conversion element shown in FIG. 1 does not include a transparent conductive film, it can be manufactured at low cost.

  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.

  By the way, in order to increase the short-circuit current density, it is necessary to support a large amount of dye on the porous semiconductor layer. Therefore, it is preferable that the thickness of the porous semiconductor layer (in other words, the photoelectric conversion layer) is large. On the other hand, in a photoelectric conversion element not provided with a transparent conductive film, the electron diffusion length is short, so it is difficult to increase the short-circuit current density even if the thickness of the photoelectric conversion layer is increased. Therefore, the present inventors have intensively studied a method for increasing the short-circuit current density of a photoelectric conversion element not provided with a transparent conductive film. As a result, the surface located on the reflective layer side of the photoelectric conversion layer has the first uneven portion. It has been found that if each of the reflective layer and the collecting electrode has an uneven shape corresponding to the first uneven portion, the short-circuit current density is increased. Hereinafter, the reason will be described after describing “the first uneven portion” and “each of the reflective layer and the collecting electrode has an uneven shape corresponding to the first uneven portion”.

  The “first concavo-convex portion” has a first concave portion and a first convex portion, and is preferably configured by alternately arranging the first concave portion and the first convex portion. Also included are parts formed integrally. “The reflective layer and the collecting electrode each have a concavo-convex shape corresponding to the first concavo-convex portion” means that the surface located on the reflective layer side of the photoelectric conversion layer has the first concavo-convex portion. It means that each of the electric electrodes has an uneven shape corresponding to the first uneven portion. Preferably, each of the reflective layer and the current collecting electrode has an uneven shape by providing the reflective layer and the current collecting electrode in this order on the first uneven portion.

  In general, an electron is likely to be recombined when it travels a long distance. For this reason, electrons generated at a distance of a certain distance (for example, electron diffusion length) or less from the surface of the photoelectric conversion layer located on the reflective layer side reach the reflective layer and are easily taken out of the photoelectric conversion element. Therefore, if the surface located on the reflective layer 3 side of the photoelectric conversion layer 2 has the first uneven portion 21, the electrons generated inside the photoelectric conversion layer 2 rather than the electrons reaching the first protruded portion 21B. Is also considered to be able to reach the first recess 21A. Therefore, as shown in FIG. 2, the amount of electrons taken out from the photoelectric conversion layer 2 is larger than when the surface of the photoelectric conversion layer 102 located on the reflective layer 103 side is flat. 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 103 is provided between the photoelectric conversion layer 102 and the current collecting electrode 104, and the thickness thereof is uniform. In general, electrons hardly flow in the reflective layer. Therefore, in the photoelectric conversion element shown in FIG. 2, it is difficult for electrons to move between the photoelectric conversion layer 102 and the current collecting electrode 104, thereby causing an increase in internal resistance components and a decrease in short circuit current density. On the other hand, in the photoelectric conversion element shown in FIG. 1, the reflective layer 3 has an uneven shape corresponding to the first uneven portion 21 of the photoelectric conversion layer 2, and the uneven shape is in the first recess 21 </ b> A of the first uneven portion 21. It has the thin part 3A provided and the thick part 3B in contact with the first convex part 21B of the first uneven part 21. Therefore, the photoelectric conversion element shown in FIG. 1 has a portion (thin portion 3A) in which the distance between the photoelectric conversion layer 2 and the current collecting electrode 4 in the thickness direction of the photoelectric conversion element is relatively short. Therefore, the electrons can move to the current collecting electrode 4 through the thin portion 3A, and therefore move more easily to the current collecting electrode 4 than the photoelectric conversion element shown in FIG. Therefore, an increase in the internal resistance component can be prevented, and loss of the internal resistance can be prevented. Thereby, electrons are collected efficiently, and electrons generated inside the photoelectric conversion layer 2 are also collected efficiently.

  As described above, in the photoelectric conversion element shown in FIG. 1, the first uneven portion 21 is provided on the surface of the photoelectric conversion layer 2 located on the reflective layer 3 side. The generated electrons are also taken out from the photoelectric conversion layer 2, and thus the amount of electrons taken out from the photoelectric conversion layer 2 increases. Moreover, since the reflective layer 3 has a concavo-convex shape corresponding to the first concavo-convex portion 21 of the photoelectric conversion layer 2, electrons taken out from the photoelectric conversion layer 2 can be efficiently transferred to the outside of the photoelectric conversion element via the collector electrode 4. It can be taken out. For these reasons, the photoelectric conversion element shown in FIG. 1 can increase the internal short-circuit current density as compared with the case shown in FIG.

  Although the structure of the 1st uneven | corrugated | grooved part 21 is not specifically limited, It is preferable to determine the structure of the 1st uneven | corrugated | grooved part 21 so that it may have a surface whose surface roughness Ra of the current collection electrode 4 is 0.3 micrometer or more and 5 micrometers or less. In general, a small surface roughness Ra indicates that the surface is flat, and a large surface roughness Ra indicates that the surface is uneven. It is considered that the surface roughness Ra of the collecting electrode 4 increases when the unevenness difference of the first uneven portion 21 (also referred to as “the recessed amount of the first recessed portion 21A” or “the protruded amount of the first protruded portion 21B”) increases. . If the surface roughness Ra of the current collecting electrode 4 is 5 μm or less, it is considered that the unevenness difference of the first uneven portion 21 can be prevented from becoming too large. Therefore, since the volume of the porous semiconductor layer can be prevented from being reduced due to the provision of the first concavo-convex portion 21 in the photoelectric conversion layer 2, it is possible to prevent the amount of the dye supported from being reduced. On the other hand, if the surface roughness Ra of the current collecting electrode 4 is 0.3 μm or more, it is considered that the unevenness difference of the first uneven portion 21 can be prevented from becoming too small. Therefore, the effect by providing the 1st uneven | corrugated | grooved part 21 in the photoelectric converting layer 2 can fully be acquired. More preferably, the configuration of the first uneven portion 21 is determined so that the current collecting electrode 4 has a surface with a surface roughness Ra of 0.5 μm or more and 4 μm or less. In the present specification, the surface roughness Ra is defined as follows. Only the reference length is extracted from the roughness curve in the direction of the average line, the X axis is taken in the direction of the average line of the extracted portion, the Y axis is taken in the direction of the vertical magnification, and the roughness curve is expressed as y = f (x ), The value obtained by the following mathematical formula (1) expressed in micrometers (μm) is referred to as surface roughness Ra. Further, the surface roughness Ra of the surface of the collector electrode 4 located on the reflective layer 3 side may be 0.3 μm or more and 5 μm or less, and the surface of the collector electrode 4 located on the charge transport layer 5 side. The surface roughness Ra may be 0.3 μm or more and 5 μm or less, and the surface roughness Ra of the surface of the collector electrode 4 located on the reflective layer 3 side and the surface of the collector electrode 4 on the charge transport layer 5 side Both of the surface roughness Ra of the surface located at 0.3 may be 0.3 μm or more and 5 μm or less.

  For example, the first uneven portion 21 is formed on the photoelectric conversion layer 2 so that the surface roughness of the surface of the photoelectric conversion layer 2 on which the first uneven portion 21 is formed is at least 0.3 μm or more and 5 μm or less. Is preferred. More specifically, the unevenness difference of the first uneven portion 21 is preferably at least 0.3 μm and 4 μm, and more preferably 0.3 μm and 3 μm. Thereby, the current collection electrode 4 will have a surface where surface roughness Ra is 0.3 micrometer or more and 5 micrometers or less.

The configuration of the first uneven portion 21 may have, for example, the configuration shown in FIGS. 3-6 is a top view which shows an example of the 1st uneven | corrugated | grooved part 21, respectively. The first concavo-convex portion 21 shown in FIG. 3 is configured by alternately arranging striped first concave portions 21A and striped first convex portions 21B. At this time, it is preferable that the first recess 21A is formed in the range of 6 to 50. The width W of the first recess 21A is preferably 0.1 μm or more and 0.5 μm or less. The first concave portion 21A is preferably formed with an interval (ΔD ₁ ) of 0.1 μm or more and 0.5 μm or less. In other words, the width of the first convex portion 21B is 0.1 μm or more and 0.0.mu.m. It is preferably 5 μm or less.

In the first concavo-convex portion 21 shown in FIG. 4, first concave portions 21 </ b> A that are circular in plan view are arranged in a matrix, and the other portions constitute the first convex portions 21 </ b> B. That is, the 1st uneven part 21 shown in FIG. 4 is comprised by the some 1st recessed part 21A and the 1st 1st convex part 21B. At this time, it is preferable that the first recess 21A is formed in the range of 6 to 100. The diameter R of the first recess 21A is preferably 0.1 μm or more and 0.5 μm or less. The distance ΔD ₂ between the adjacent first recesses 21A is preferably 0.1 μm or more and 0.5 μm or less.

  The first uneven portion 21 shown in FIG. 5 is configured by alternately arranging first concave portions 21A having a square shape in plan view and first convex portions 21B having a square shape in plan view. At this time, each of the first concave portion 21A and the first convex portion 21B is preferably formed in the range of 5 to 50. One side of each of the first concave portion 21A and the first convex portion 21B is preferably 0.1 μm or more and 0.5 μm or less.

  As for the 1st uneven | corrugated | grooved part 21 shown in FIG. 6, the 1st recessed part 21A of planar view square is arrange | positioned at matrix form, and the other part comprises the 1st convex part 21B. That is, the 1st uneven part 21 shown in FIG. 6 is also comprised by the some 1st recessed part 21A and the 1st 1st convex part 21B. At this time, it is preferable that the number of the first recesses 21A is 5 or more and 50 or less. One side of the first recess 21A is preferably 0.1 μm or more and 0.5 μm or less.

  As described above, the uneven shape of the reflective layer 3 includes the thin portion 3A provided in the first recess 21A of the first uneven portion 21 and the thick portion 3B in contact with the first protrusion 21B of the first uneven portion 21. It is preferable that the thin portion 3A and the thick portion 3B are integrally formed. The thickness of the thin portion 3A is preferably equal to the depth of the first recess 21A, and is preferably 0.3 μm or more and 5 μm or less, for example. The thickness of the thick part 3B is preferably 2 μm or more and 10 μm or less.

  The uneven shape of the current collecting electrode 4 is preferably located between the photoelectric conversion layer 2 and the charge transport layer 5, and is configured by being in contact with each of the thin portion 3A and the thick portion 3B. It is preferable. Below, the structural member of the photoelectric conversion element shown in FIG. 1 is 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 transmission is required at the light receiving surface of the photoelectric conversion element, the light transmissive support 1 is preferably made of a light transmissive material, such as soda glass, fused quartz glass, or the like. 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 effective sensitivity to at least a dye described later is substantially transmitted (the transmittance of the light is, for example, 80% or more, preferably 90% or more), and need not necessarily be transparent to light of all wavelengths. The thickness of the translucent support 1 is not particularly limited, and is preferably about 0.2 to 5 mm, for example.

  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.

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

(Configuration of 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 a large amount of dye, 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.

A semiconductor material will not be specifically limited if it is a semiconductor material which can generally be used for a photoelectric conversion element, and can exhibit the effect of this invention. Such semiconductor materials are, 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 semiconductor material, 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 semiconductor material.

  When titanium oxide is used as the semiconductor material, the titanium oxide used may be various narrowly defined titanium oxides such as anatase type titanium oxide, rutile type titanium oxide, amorphous titanium oxide, metatitanic acid or orthotitanic acid, It may be 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. From the viewpoint of ease of dye adsorption, 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 the content of anatase-type titanium oxide is 80% or more. It is more preferable to use a certain one. 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 configured using particles (semiconductor particles) made of a semiconductor material having the same size, or may be configured using semiconductor particles having different sizes. Since relatively large semiconductor particles scatter incident light, it is considered that it contributes to an improvement in the light capture rate. If relatively small semiconductor particles are used, the number of dye adsorption points increases. Therefore, it is considered that relatively small semiconductor particles contribute to an improvement in the amount of dye adsorption.

  The average particle size of relatively large semiconductor particles is preferably 10 times or more than the average particle size of relatively small semiconductor particles. For example, the average particle size of relatively large semiconductor particles is preferably 100 to 500 nm, and the average particle size of relatively small semiconductor particles is preferably 5 nm to 50 nm. The semiconductor particles having different sizes may be made of the same material or different materials. When semiconductor particles having different sizes are made of different materials, it is preferable that relatively small semiconductor 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. Moreover, since a pigment | dye is adsorb | sucked to a porous semiconductor layer, it is preferable that the surface area of a porous semiconductor layer is large, for example, it is preferable that the BET specific surface area of a porous semiconductor layer is about 10-200 m < ² > / g.

(Formation of porous semiconductor layer)
It does not specifically limit as a formation method of 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 comprising 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.

(Formation of first uneven portion)
Various known methods can be applied as a method of forming the first uneven portion 21 described above. For example, a method of forming by laser scribing, a method of forming by mechanical grinding with a stylus, or a method of forming by screen printing using a screen plate on which a first concavo-convex portion is formed may be mentioned. Among these, if the 1st uneven | corrugated | grooved part 21 is formed by laser scribe, a high-definition scribe pattern can be formed. Accordingly, it is preferable to form the first uneven portion 21 by laser scribing.

  It is preferable to appropriately select the formation method according to the shape of the first uneven portion 21. The first concave portion 21A or the first convex portion 21B may be partially formed by laser scribing using a desired pattern, or a porous semiconductor layer is newly added to a portion different from the portion where the first concave portion 21A is formed. You may form in. Thereby, the 1st uneven | corrugated | grooved part 21 which has a desired shape can be formed.

(Dye)
The dye may be a variety of organic dyes that can be adsorbed on the porous semiconductor layer and function as a photosensitizer and can absorb light in at least one of the visible light region and the infrared light region, or visible light. Various metal complex dyes capable of absorbing light in at least one of the light region and the infrared light region may be used. 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 perylene dyes. A dye, an indigo dye or a naphthalocyanine dye is preferable. 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.

  Examples of the metal complex dye include Cu, Ni, Fe, Co, V, Sn, Si, Ti, Ge, Cr, Zn, Ru, Mg, Al, Pb, Mn, In, Mo, Y, Zr, Nb, and 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, etc. It is preferable that a ligand is coordinated to a metal atom. The metal complex dye is preferably, for example, a porphyrin dye, phthalocyanine dye or naphthalocyanine dye, more preferably a phthalocyanine dye or a ruthenium dye, and a ruthenium metal complex dye. Is more preferable.

  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 firmly adsorb the dye to the porous semiconductor layer, the dye must have an interlock group such as a carboxyl group, alkoxy group, hydroxyl group, sulfonic acid group, ester group, mercapto group or phosphonyl group in the molecule. Is preferred. In general, the interlock group is present between the dye and the porous semiconductor layer when the dye is fixed to the porous semiconductor layer, and the excited state of the dye and the conduction band of the semiconductor material constituting the porous semiconductor layer Provides electrical coupling that facilitates the transfer of electrons between the two.

The amount of dye adsorbed 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 ⁻⁷ mol / cm 2. ² is more preferable. If the amount of dye adsorbed is less than 1 × 10 ⁻⁸ mol / cm ² , the photoelectric conversion efficiency may be reduced. On the other hand, when the adsorption amount of the dye exceeds 1 × 10 ⁻⁶ mol / cm ² , there may be a problem that the open circuit voltage is lowered.

(Dye adsorption)
A typical example of the method for adsorbing the dye to the porous semiconductor layer is a method of immersing the porous semiconductor layer in a solution in which the dye is dissolved (hereinafter referred to as “dye adsorption solution”). 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 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 density | concentration of the pigment | dye in the solution for pigment | dye adsorption can be suitably set according to conditions, such as the kind of pigment | dye to be used, the kind of solvent, or a pigment | dye adsorption process, for example, it is preferable that it is 1 * 10 < ^-5 > mol / liter or more. 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. . 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, lead sulfide, zinc sulfide. A compound semiconductor material such as 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 semiconductor particles contained in 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 semiconductor particles contained in the porous semiconductor layer, and the semiconductor contained in the porous semiconductor layer It is more preferable that the average particle size is 3 to 20 times the average particle size. In other words, when the average particle size of the semiconductor particles contained in 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 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 the ratio of the relatively large particles in the porous semiconductor layer (the porosity relative to the total number of semiconductor particles contained in the porous semiconductor layer) It may be higher than the ratio of the number of relatively large particles among the semiconductor particles contained in the semiconductor layer. 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 semiconductor particles contained in the porous semiconductor layer.

  The thickness of the reflective layer 3 is not particularly limited, but is preferably larger than the thickness of the current collecting electrode 4 located between the photoelectric conversion layer 2 and the charge transport layer 5, for example, 0.2 nm or more and 1000 μm or less. It is preferable. This will be described in the following <collecting electrode>.

(Formation of 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 having an average particle size larger than the average particle size of the semiconductor particles contained in the porous semiconductor layer. The reason is 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 3 may be formed using a screen having a predetermined pattern shape (screen printing method). The formed reflection layer 3 preferably has an uneven shape corresponding to the first uneven portion 21 of the photoelectric conversion layer 2. When the formed reflective layer 3 does not have this concavo-convex shape, it is preferable that the concavo-convex shape corresponding to the first concavo-convex portion 21 is formed in the reflective layer 3 according to the method of forming the first concavo-convex portion 21.

  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>
The collector electrode 4 is supported by the translucent support 1, and specifically, provided on the sealing portion 8 and on the translucent support 1 positioned outside the sealing portion 8. It has been. Thereby, the current collection electrode 4 can be smoothly connected to the counter electrode 6 via an external electric circuit.

  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 includes indium tin composite oxide (ITO), tin oxide (SnO ₂ ), tin oxide doped with fluorine (FTO), zinc oxide (ZnO), etc. It is also possible to use a metal that does not show corrosiveness to a carrier transport material such as titanium, nickel, or tantalum.

  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 collecting electrode 4 is preferably as low as possible since the FF (curve factor) is improved, and is 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 includes 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 of The redox species is a combination of a tetraalkylammonium salt such as tetraethylammonium iodide (TEAI), tetrapropylammonium iodide (TPAI), tetrabutylammonium iodide (TBAI) or tetrahexylammonium iodide (THAI) and iodine. It may be. The redox species may be a combination of a 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, aprotic polar substances, and the like. 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 may be any material that can be used as an electrolyte of a photoelectric conversion element and does not have 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 a p-type semiconductor such as copper halide and copper thiocyanate, or an electrolyte obtained by solidifying a liquid electrolyte containing a molten salt 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 gelation such as a crosslinked polyacrylic resin derivative, a crosslinked polyacrylonitrile derivative, a polyalkylene oxide derivative, a silicone resin, or a polymer having a nitrogen-containing heterocyclic quaternary compound salt structure in the side chain. Agents 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, a glass frit, and the like. 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.

  As described above, in the photoelectric conversion element shown in FIG. 1, the photoelectric conversion layer 2 having a porous semiconductor layer, the reflective layer 3, and the light-transmissive support 1 are supported on the light-transmissive support 1. The collected current electrode 4, the charge transport layer 5, and the counter electrode 6 are provided in this order. The surface located on the reflective layer 3 side of the photoelectric conversion layer 2 has a first uneven portion 21. Each of the reflective layer 3 and the current collecting electrode 4 has an uneven shape corresponding to the first uneven portion 21. Thereby, electrons generated inside the photoelectric conversion layer 2 are also taken out from the photoelectric conversion layer 2. In addition, electrons taken out from the photoelectric conversion layer 2 can be efficiently taken out to the outside of the photoelectric conversion element via the collector electrode 4. Therefore, the internal short circuit current density can be increased as compared with the case shown in FIG.

  The uneven shape of the reflective layer 3 preferably has a thin portion 3A provided in the first recess 21A of the first uneven portion 21 and a thick portion 3B in contact with the first protrusion 21B of the first uneven portion 21. . Thereby, the electrons taken out from the photoelectric conversion layer 2 can be taken out more efficiently to the outside of the photoelectric conversion element via the collector electrode 4.

  The current collecting electrode 4 preferably has a surface with a surface roughness Ra of 0.3 μm or more and 5 μm or less. Thereby, while being able to fully acquire the effect by having provided the 1st uneven part 21 in photoelectric conversion layer 2, due to having provided the 1st uneven part 21 in photoelectric conversion layer 2, a porous semiconductor layer It can prevent that the volume of becomes small.

  The reflective layer 3 preferably includes particles having an average particle size larger than the average particle size of the semiconductor particles contained in the porous semiconductor layer. Thereby, since the light that could not be absorbed by the photoelectric conversion layer 2 can be scattered, the optical path length of the light that could not be absorbed by the photoelectric conversion layer 2 is increased, thereby increasing the absorption of light of long wavelength light. Can do. 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.

  The first uneven portion 21 preferably has a stripe-shaped first concave portion 21A and a stripe-shaped first convex portion 21B.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. In the following description, unless otherwise specified, the thickness of each layer and the surface roughness of each layer were 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 manufactured. First, a 51 mm × 70 mm × 1 mm thick glass substrate (Corning 7059) was prepared as the translucent support 1.

<Formation of sealing part>
A screen plate having an opening width of 0.5 mm was placed around a place on the glass substrate 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. Using a screen printer (Neurong Seimitsu Kogyo Co., Ltd., Model: LS-34TVA), a titanium oxide paste (Solaronix, trade name: Ti-Nanoxide D / SP, average particle size 13 nm) is placed on the glass substrate. 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 first uneven portion>
The first concave portion 21A of the first concave and convex portion 21 was formed by laser scribing on the surface of the formed 5 mm × 5 mm porous semiconductor layer. The first recesses 21A of the first concavo-convex portion 21 are formed in a line shape having a line width W (see FIG. 3) of 200 μm and a depth of 2 μm, and a line interval ΔD ₁ (see FIG. 3). 11 were formed with a thickness of 0.3 mm. Here, the line interval ΔD ₁ is the interval between the adjacent first concave portions 21A, and in other words, is the width of the first convex portion 21B. The first recess 21A of the first uneven portion 21 was also formed at the edge of the porous semiconductor layer. Thus, the first concave portion 21A was formed, and the first concave and convex portion 21 was formed on the surface of the porous semiconductor layer.

<Formation of reflective layer>
The same screen as that used to form the porous semiconductor layer was placed on the porous semiconductor layer on which the first uneven portion 21 was formed. 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 formed reflective layer 3 had an uneven shape corresponding to the first uneven portion 21 and its thickness 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 formed collecting electrode 4 had an uneven shape corresponding to the first uneven portion 21 and had a surface with a surface roughness Ra of 1 μm. The formed collecting electrode 4 had a thickness of 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 dye (manufactured by Solaronix, trade name: Ruthenium 620-1H3TBA) was dissolved in the 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. In this way, a photoelectric conversion layer having a thickness of 16 μm was formed.

<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.

The electrolyte is injected into the counter electrode 6 and the counter electrode support 7 from the electrolyte injection hole previously opened, and the electrolyte injection hole is sealed with an ultraviolet curable resin (manufactured by ThreeBond, model number: 31X-101 229). Stopped. 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 method described in Example 1 except that the configuration of the first uneven portion 21 was different. In Example 2, the first concave portions 21A of the first concave and convex portions 21 are formed in a linear shape having a line width W (see FIG. 3) of 200 μm and a depth of 2 μm, and a line interval ΔD _1. Fifteen were formed with 0.1 mm (see FIG. 3). Moreover, the current collecting electrode 4 had a surface with a surface roughness Ra of 3.2 μm. 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 3>
A photoelectric conversion element of Example 3 was manufactured according to the method described in Example 1 except that the configuration of the first uneven portion 21 was different. In Example 3, the first concave portions 21A of the first concave and convex portions 21 are formed in a linear shape having a line width W (see FIG. 3) of 200 μm and a depth of 4 μm, and a line interval ΔD _1. Fifteen were formed with 0.1 mm (see FIG. 3). Further, the collecting electrode 4 had a surface with a surface roughness Ra of 4.2 μm. 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 14.3 mA / cm ² .

<Example 4>
A photoelectric conversion element of Example 4 was manufactured according to the method described in Example 1 except that the configuration of the first uneven portion 21 was different. In Example 4, the first recesses 21A of the first concavo-convex portions 21 are formed in a line shape having a line width W (see FIG. 3) of 200 μm and a depth of 4 μm, and a line interval ΔD _1. Eleven lines were formed with 0.3 mm (see FIG. 3). Moreover, the current collecting electrode 4 had a surface with a surface roughness Ra of 3.7 μm. 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 14.7 mA / cm ² .

<Example 5>
A photoelectric conversion element of Example 5 was manufactured according to the method described in Example 1 except that the thickness of the photoelectric conversion layer was 20 μm and the configuration of the first uneven portion 21 was different. In the fifth embodiment, the first concave portions 21A of the first concave and convex portions 21 are formed in a linear shape having a line width W (see FIG. 3) of 200 μm and a depth of 4 μm, and a line interval ΔD _1. Eleven lines were formed with 0.3 mm (see FIG. 3). In addition, the current collecting electrode 4 had a surface with a surface roughness Ra of 4 μm. 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 18.1 mA / cm ² .

<Example 6>
A photoelectric conversion element of Example 6 was manufactured according to the method described in Example 1 except that the configuration of the first uneven portion 21 was different. In Example 6, the first recesses 21A of the first concavo-convex portions 21 are formed in a line shape having a line width W (see FIG. 3) of 200 μm and a depth of 6 μm, and a line interval ΔD _1. Eleven lines were formed with 0.3 mm (see FIG. 3). Moreover, the current collecting electrode 4 had a surface with a surface roughness Ra of 4.9 μm. 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 14.2 mA / cm ² .

<Example 7>
A photoelectric conversion element of Example 7 was manufactured according to the method described in Example 1 except that the configuration of the first uneven portion 21 was different. In Example 7, the first recesses 21A of the first concavo-convex portions 21 are formed in a line shape having a line width W (see FIG. 3) of 200 μm and a depth of 1 μm, and a line interval ΔD _1. Eleven lines were formed with 0.3 mm (see FIG. 3). Moreover, the current collecting electrode 4 had a surface with a surface roughness Ra of 0.5 μm. 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 14.8 mA / cm ² .

<Example 8>
A photoelectric conversion element of Example 8 was manufactured according to the method described in Example 1 except that the thickness of the photoelectric conversion layer was 20 μm and the configuration of the first uneven portion 21 was different. In Example 8, the first recesses 21A of the first concavo-convex portions 21 are formed in a line shape having a line width W (see FIG. 3) of 200 μm and a depth of 6 μm, and a line interval ΔD _1. Eleven lines were formed with 0.3 mm (see FIG. 3). Moreover, the current collecting electrode 4 had a surface with a surface roughness Ra of 4.8 μm. 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 18.3 mA / cm ² .

<Example 9>
A photoelectric conversion element of Example 9 was manufactured according to the method described in Example 1 except that the configuration of the first uneven portion 21 was different. In the ninth embodiment, the first concave portions 21A of the first concave and convex portions 21 are formed in a linear shape having a line width W (see FIG. 3) of 200 μm and a depth of 8 μm, and a line interval ΔD _1. Eleven lines were formed with 0.3 mm (see FIG. 3). The collecting electrode 4 had a surface with a surface roughness Ra of 5.2 μm. 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 12.0 mA / cm ² .

<Example 10>
A photoelectric conversion element of Example 10 was manufactured according to the method described in Example 1 except that the first uneven portion shown in FIG. 6 was formed. In Example 10, 13 first concave portions 21A (1 mm square in plan view) of the first concave and convex portions 21 were formed by laser scribing on the surface of the 5 mm × 5 mm porous semiconductor layer. Thus, the 1st uneven | corrugated | grooved part 21 was formed in the surface of a porous semiconductor layer. Moreover, the current collecting electrode 4 had a surface with a surface roughness Ra of 4.0 μm. 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 11>
A photoelectric conversion element of Example 11 was manufactured according to the method described in Example 1 except that the first uneven portion shown in FIG. 4 was formed. In Example 11, the 1st recessed part 21A (1 mm diameter by planar view) of the 1st uneven | corrugated | grooved part 21 was formed with laser scribe with respect to the surface of a 5 mm x 5 mm porous semiconductor layer. The locations where the first recesses 21A were formed were the same in Example 10 and Example 11. Thus, the 1st uneven | corrugated | grooved part 21 was formed in the surface of a porous semiconductor layer. Moreover, the current collecting electrode 4 had a surface with a surface roughness Ra of 4.1 μm. 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 .

<Comparative Example 1>
A photoelectric conversion element of Comparative Example 1 was manufactured according to the same method as in Example 1 except that the photoelectric conversion element was manufactured without forming the first uneven portion. That is, in the photoelectric conversion element of Comparative Example 1, the reflective layer was provided between the photoelectric conversion layer and the current collecting electrode so that the thickness thereof was uniform. The current collecting electrode had a surface with a surface roughness Ra of 0.2 μm. 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 .

  As shown in Table 1, in Examples 1 to 11, the short circuit current density was higher than that in Comparative Example 1. The reason is considered as follows. In Examples 1-11, since the 1st uneven | corrugated | grooved part 21 is formed in the surface located in the reflection layer 3 side among the photoelectric converting layers 2, the electron produced inside the photoelectric converting layer 2 is also a photoelectric converting layer. 2 is taken out. In addition, since the reflective layer 3 has a concavo-convex shape corresponding to the first concavo-convex portion 21, the electrons extracted from the photoelectric conversion layer 2 can be efficiently extracted outside the photoelectric conversion element via the collector electrode 4. Can do. On the other hand, in Comparative Example 1, since the surface of the photoelectric conversion layer located on the reflection layer side is flat, it is difficult to take out electrons generated in the photoelectric conversion layer 2 from the photoelectric conversion layer 2. In addition, since the thickness of the reflective layer is uniform, electrons do not easily move between the photoelectric conversion layer and the current collecting electrode, and thus increase the internal resistance component of the photoelectric conversion element.

  When Examples 1-8 were compared with Example 9, the short circuit current density was higher in Examples 1-8 than in Example 9. The reason is considered as follows. In Examples 1 to 8 and Example 9, a stripe-shaped first concave portion and a stripe-shaped first convex portion are formed. In Examples 1-8, surface roughness Ra of a current collection electrode is 5.0 micrometers or less. On the other hand, in Example 9, since the surface roughness Ra of the collecting electrode is larger than 5.0 μm, the adsorption amount of the dye supported on the photoelectric conversion layer is lower than those in Examples 1-8.

  From the results of Examples 1 to 11, it was found that the internal short circuit density can be increased without being limited to the shape of the first uneven portion 21.

  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, 2,102 Photoelectric conversion layer, 3,103 Reflective layer, 3A Thin part, 3B Thick part, 4,104 Current collection electrode, 5 Charge transport layer, 6 Counter electrode, 7 Counter electrode support body, 8 Sealing part, 21 1st uneven | corrugated | grooved part, 21A 1st recessed part, 21B 1st convex part.

Claims (5)

On the translucent support, a photoelectric conversion layer having a porous semiconductor layer, a reflective layer, a current collecting electrode supported by the translucent support, a charge transport layer, and a counter electrode are sequentially provided. ,
The surface located on the reflective layer side of the photoelectric conversion layer has a first uneven portion,
Each of the reflective layer and the current collecting electrode is a photoelectric conversion element having an uneven shape corresponding to the first uneven portion.   The said uneven | corrugated shape of the said reflection layer has a thin part provided in the 1st recessed part of the said 1st uneven part, and a thick part which contact | connects the 1st convex part of the said 1st uneven part. Photoelectric conversion element.   The photoelectric conversion element according to claim 1, wherein the current collecting electrode has a surface having a surface roughness Ra of 0.3 μm or more and 5 μm or less.   The photoelectric conversion element according to claim 1, wherein the first concavo-convex portion includes a striped first concave portion and a striped first convex portion.   The dye-sensitized solar cell provided with the photoelectric conversion element in any one of Claims 1-4.

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