JP2010140812A - Function element, manufacturing method therefor, and dye-sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance performance of a function element, by reducing the energy barrier in the grain boundary of particulate groupings which constitute the function element of a photoelectric transfer element, or the like, of a dye-sensitized solar cell. <P>SOLUTION: A gel precursor 25 to become a function film 24 is coated on the surface of particulate nucleus 23 to form particulates 22. The particulates 22 are, for example, arranged on a substrate 10 by coating or the like and are collected by pressurization or the like. Then, the precursor 25 is calcined to form the function film 24. The adjoining function films 24 of the particulates 22 are made to be integrally continuous. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a functional element composed of an aggregate of fine particles and a method for producing the functional element, and in particular, a functional element suitable for a photoelectric conversion element of a dye-sensitized solar cell, a reaction part of a fuel cell, and the production thereof. It is about the method.

  In a dye-sensitized solar cell generally known as a so-called Gretzell type (see Patent Document 1), a photoelectric conversion element is provided on a base material including a conductive film. The photoelectric conversion element is composed of a porous titanium oxide film on which a sensitizing dye such as a ruthenium complex is adsorbed. Titanium oxide crystal particles are aggregated to make it porous. As a result, the specific surface area of the photoelectric conversion element is increased, the light absorption amount of the dye, and hence the charge transport amount, is increased, thereby improving the power generation efficiency.

The titanium oxide porous membrane is usually produced as follows (see Patent Document 2 etc.). A titanium alkoxide or the like is hydrothermally synthesized to produce a colloidal solution containing fine particles of titanium oxide crystals having a particle size of about 10 nm to 1 μm. This colloidal solution is applied to a substrate made of a transparent electrode. Thereafter, it is fired at a high temperature. As a result, the fine particles of titanium oxide crystals are solid-welded (necked) to obtain a porous titanium oxide film.
Japanese Patent No. 2664194 JP 2005-302509 A

However, in the aggregate of crystal particles produced in this way, adjacent particles are solid-phase bonded (necked). The directions of the crystal planes of these fine particles are random to each other. Therefore, a grain boundary resistance, that is, an energy barrier is formed between adjacent fine particles. The grain boundary resistance hinders the conductivity of carrier electrons and lowers the power generation efficiency as a photoelectric conversion element. If the particle size is increased, the grain boundary density is decreased and the resistance is decreased, but the surface area contributing to power generation is decreased, so that the power generation efficiency is decreased. If the particle size is reduced to increase the surface area that contributes to power generation, the grain boundary density increases and the resistance increases.
The present invention has been made in view of the above circumstances, and its object is the grain boundary resistance of a fine particle assembly applied to various functional elements including a photoelectric conversion element of a dye solar cell. The purpose is to reduce the energy barrier of the device and improve the performance of the functional device.

In order to solve the above problems, the present invention is a method for producing a functional element including a fine particle assembly,
A precursor generating step for generating a gel-like precursor to be a functional film responsible for the function of the functional element;
Coating the precursor on the surface of fine particle nuclei to obtain fine particles; and
An assembly step of assembling and arranging a large number of the fine particles;
A firing step of firing the aggregated fine particles;
It is characterized by performing.

  By assembling the fine particles, adjacent fine particles can be brought into contact with each other. Then, the gel-like precursors of adjacent fine particles are continuously connected. By firing the aggregate of the fine particles, the functional film can be generated by sintering the precursor. The functional film covers each particle nucleus. In addition, adjacent functional films of fine particles are integrally connected. When the functional film is crystalline, the crystal plane directions of the functional films of adjacent fine particles are aligned and are crystallized integrally. Therefore, the energy barrier such as the grain boundary resistance of the fine particle aggregate can be reduced, and the performance of the functional element can be improved. By assembling the fine particles into a three-dimensional network structure, the functional element can be made porous and the specific surface area of the functional element can be increased.

Further, the present invention is a functional element composed of an aggregate of fine particles,
The fine particles have fine particle nuclei and a functional film coated on the surface of the fine particle nuclei, and the functional films of adjacent fine particles are integrally continuous.
Thereby, the energy barrier at the grain boundary of the fine particle aggregate can be reduced, and the performance of the functional element can be enhanced.
The term “continuous in one piece” means a state in which the functional films of adjacent fine particles are connected without interposing an interface, and is not limited to the case where there is no interface at the bonding portion between the functional films of adjacent fine particles. In addition, the case where the interface does not exist in a part of the bonding portion and the interface exists in the remaining part is included. In the case where the functional film is crystalline, the term “continuous integrally” includes a state in which the crystal plane directions of the functional films of adjacent fine particles are aligned with each other.

The particle diameter of the fine particle nuclei is preferably 1 nm to 1 μm, and more preferably 1 nm to 30 nm.
The grain boundary density increases as the particle diameter of the fine particle nuclei and thus the particle diameter of the fine particles become smaller. On the other hand, according to the present invention, it is possible to keep the energy barrier of the entire functional element low even if the grain boundary density increases by making the functional films of adjacent fine particles continuous. Therefore, in the case of a functional element whose function increases as the specific surface area increases, the specific surface area can be increased by sufficiently reducing the particle size without concern for an increase in the energy barrier.

It is preferable that the aggregate of fine particles has a three-dimensional network structure.
Thereby, the functional element can be made porous and the specific surface area can be increased.

The precursor is preferably generated by a sol-gel method using at least one compound selected from a metal salt, a metal alkoxide, and an organometallic complex as a starting material. Examples of metal salts include titanium salts. Examples of the metal alkoxide include titanium tetraalkoxide. Examples of the organometallic complex include bistoluene titanium.
It is preferable that the selected compound contains at least one metal element selected from Ti, Zn, Sn, In, W, V, Al, Fe, Sr, and Ga.

The functional film preferably contains a metal chalcogenide compound.
The metal chalcogenide compound refers to a compound containing a metal and an oxygen group element (for example, O, S, Se, Te, Po). The metal chalcogenide compound preferably contains at least one metal element selected from Ti, Zn, Sn, In, W, V, Al, Fe, Sr, and Ga. Examples of the metal chalcogenide compound include TiO ₂ , ZnO, ZnS, and the like.
The functional film may contain a plurality of metal chalcogenide compounds.

  The thickness of the functional film is preferably 1 nm to 100 nm, and more preferably 1 nm to 10 nm.

In the assembly step of the functional element manufacturing method according to the present invention, it is preferable that the fine particles are placed on a substrate and pressed.
By pressurization, the arrangement density of the fine particles can be increased, and the fine particles can be reliably assembled. When the fine particle nuclei are in contact with each other, the adjacent fine particles can be reliably brought into contact with each other while serving as a stopper, and further, the functional precursors of the adjacent fine particles can be reliably made continuous.

In the assembly step of the functional element manufacturing method according to the present invention, the fine particles may be sprayed onto the base material so as to collide with each other.
A spraying device such as a spray gun may be used for spraying the fine particles. The particles can be brought into contact with each other by the impact of the collision.

Further, the present invention is a method for producing a dye-sensitized solar cell, wherein a functional element is produced by the functional element production method, and the functional element is a photoelectric conversion element,
The precursor is a precursor of a semiconductor film, the fine particles are collected on a transparent electrode and fired, and a sensitizing dye is supported on the fired fine particle aggregate.

  According to this method for producing a dye-sensitized solar cell, a gel-like semiconductor film precursor is generated, and the gel-like semiconductor film precursor is coated on fine particle nuclei. The obtained fine particles are collected and arranged on the transparent electrode. Thereby, the gel-like semiconductor film precursors of adjacent fine particles can be made continuous. The assembled fine particles are fired. By baking, the gel-like semiconductor film precursor can be made into a solid phase semiconductor film. Thereby, an aggregate of fine particles formed by coating fine particle nuclei with a semiconductor film can be obtained. Adjacent fine particle semiconductor films in this fine particle aggregate can be made to continue integrally. A sensitizing dye is supported on the fine particle aggregate. Thereby, the photoelectric conversion element of a dye-sensitized solar cell can be obtained. Since this photoelectric conversion element is composed of an aggregate of fine particles, it can have a three-dimensional network structure, that is, a porous structure, and can secure a specific surface area. In addition, since the semiconductor films of adjacent fine particles are continuously connected, the grain boundary resistance can be reduced. Therefore, the particle size of the fine particles can be reduced and the specific surface area can be sufficiently increased without concern for an increase in internal resistance of the photoelectric conversion element. As a result, the photoelectric conversion efficiency of the photoelectric conversion element can be increased, and as a result, the power generation efficiency of the dye-sensitized solar cell can be increased.

Furthermore, the present invention provides a dye-sensitized solar cell having the functional element as a photoelectric conversion element, wherein the functional film is a semiconductor film supporting a sensitizing dye, and the aggregate of the fine particles is a three-dimensional network. It has a structure and is in contact with a transparent electrode.
By making the fine particle aggregate into a three-dimensional network structure, the photoelectric conversion element can be made porous, and the specific surface area of the photoelectric conversion element can be secured. Further, adjacent semiconductor films of fine particles are continuous. Therefore, the grain boundary resistance can be reduced. Therefore, the particle size of the fine particles can be reduced and the specific surface area can be sufficiently increased without concern for an increase in internal resistance of the photoelectric conversion element. As a result, the photoelectric conversion efficiency of the photoelectric conversion element can be increased, and as a result, the power generation efficiency of the dye-sensitized solar cell can be increased.

The sensitizing dye absorbs light and releases a charge. As the sensitizing dye, for example, an organometallic complex such as a ruthenium complex is preferably used.
The semiconductor film receives charges from the sensitizing dye and transports them to the transparent electrode. For example, titanium oxide is preferably used as the semiconductor film.
The thickness of the semiconductor film is preferably 1 nm to 100 nm. Furthermore, the thickness of the semiconductor film is preferably 1/10 or less of the absorption wavelength of the sensitizing dye. As a result, the semiconductor film can sufficiently perform the photoelectric conversion function and the charge transport function, and the semiconductor film can be prevented from becoming unnecessarily thick, and the particle size of the fine particles can be prevented from increasing. The surface area can be reliably increased.

  The fine particle nucleus for the dye-sensitized solar cell may be made of a translucent material. Thereby, the light can sufficiently reach the inside of the photoelectric conversion element, and the photoelectric conversion efficiency can be improved. A glass bead etc. are mentioned as a fine particle nucleus which has translucency.

  According to the present invention, the energy barrier at the grain boundary of the fine particle aggregate can be reduced, and the performance of the functional element can be improved.

A preferred embodiment of the present invention will be described.
The functional element of the present invention refers to an element having a predetermined function. Examples of the predetermined function include an optical function, an electrical function, a chemical function, a physical function, and the like. Specifically, there are a photoelectric conversion function, a charge transport function, a semiconductor function, a catalyst function, a heat transfer function, and the like. Can be mentioned. For example, the functional element can be applied to a photoelectric conversion element of a dye-sensitized solar cell, a reaction part of a fuel cell, an electrode, and the like.

  The functional element includes an aggregate of fine particles. Fine particles are stacked in the thickness direction, and the fine particle aggregate has a three-dimensional network structure. As a result, the functional element is porous.

  Each fine particle constituting the fine particle aggregate includes a fine particle nucleus and a functional film coated on the surface of the fine particle nucleus.

  The fine particle nucleus constitutes the fine particle nucleus, that is, the central portion. The fine particle nucleus serves as a support for supporting the functional film or a precursor described later. The fine particle nucleus has mechanical strength for supporting the functional film and the precursor described later, and further has mechanical strength that can withstand the pressurization described later and thermal strength that can withstand the firing temperature. The fine particle nucleus may be composed of a conductive material such as metal, may be composed of an insulator such as resin or ceramic, and may be composed of a light-transmitting material such as glass. Plural kinds of fine particle nuclei with different materials may be mixed in the fine particle aggregate. The fine particle nucleus may be composed of the same component as the functional film.

  The particle diameter of the fine particle nuclei is, for example, 1 nm or more and 1 μm or less, preferably 1 nm or more and 30 nm or less. A plurality of types of fine particle nuclei having different sizes may be mixed in the fine particle aggregate. Thereby, a fine particle aggregate can be made into arbitrary porous shapes.

The shape of the fine particle nucleus may be a sphere with a controlled particle size, a plate shape or a rod shape, or an arbitrary shape such as a star shape. Plural kinds of fine particle nuclei having different shapes may be mixed in the fine particle aggregate. Thereby, a fine particle aggregate can be made into arbitrary porous shapes.
A single particle aggregate may contain a plurality of types of particle nuclei having different materials, sizes, and shapes.

  The fine particle nuclei of adjacent fine particles in the fine particle aggregate may be in contact with each other or may be separated from each other. A functional film may be interposed so as to fill a space between adjacent fine particle nuclei.

The functional film is coated on the surface of the fine particle nucleus. The functional film is an element having the predetermined function in the functional element. The functional film may be responsible for the above function alone, or the functional film may be responsible for the above function in cooperation with other elements of the functional element. For example, in a photoelectric conversion element of a dye-sensitized solar cell, a functional film made of a semiconductor such as titanium oxide exhibits a photoelectric conversion function in cooperation with a sensitizing dye supported on the functional film. In the photoelectric conversion element of the dye-sensitized solar cell, the functional film made of a semiconductor such as titanium oxide has a charge transport function and a semiconductor function by itself.
The fine particle nuclei need not have the predetermined function, but it does not exclude having the predetermined function. The fine particle nuclei may have the same or lower function than the functional film or a higher function. The functional film and the fine particle nucleus may cooperate with each other to perform the predetermined function.

The thickness of the functional film is, for example, 1 nm or more and 100 nm or less, and preferably 1 nm or more and 10 nm or less. The thickness of the functional film of the plurality of fine particles may be different from each other.
The total particle diameter of the fine particles including the fine particle nucleus and the functional film is preferably about several nm to 1 μm, and more preferably about 10 nm to 50 nm.

  The component of the functional film is appropriately selected according to the function of the functional element. The functional film preferably contains a metal chalcogenide compound. The metal element of the metal chalcogenide compound is selected from Ti, Zn, Sn, In, W, V, Al, Fe, Sr, Ga, and the like. The metal chalcogenide compound may contain two or more metal elements. The functional film may be a mixture containing two or more metal chalcogenide compounds. The functional film is preferably crystalline. The functional film may be a semiconductor.

  Adjacent fine particle functional films are integrally continuous without an interface. In other words, there is no interface or only a partial interface at the bonding portion between the adjacent functional films of the fine particles, and the functional films are integrated and straddle between the adjacent fine particles. When the functional film is crystalline, the directions of the crystal planes of the functional films of adjacent fine particles are aligned.

An example of a method for manufacturing a functional element will be described.
[Precursor generation step]
A gel-like precursor to be a functional film is generated. The gel-like precursor is produced by a sol-gel method using, for example, a metal salt, metal alkoxide, organometallic complex or the like as a starting material. The starting metal salt, metal alkoxide, or organometallic complex is preferably a kind of organometallic chalcogenide. A starting material such as a metal salt, metal alkoxide, or organometallic complex is dissolved in a solvent and subjected to hydrolysis, dehydration, polymerization, condensation, and the like to obtain a gel-like precursor.

[Coating process]
The above gel-like precursor is coated on the surface of the fine particle nucleus to obtain fine particles having a gel surface.

[Placement process, assembly process]
A large number of fine particles obtained as described above are arranged and assembled on a substrate. Thereby, the fine particles come into contact with each other, and a fine particle aggregate having a three-dimensional network structure is obtained. Furthermore, the gel-like precursors of adjacent fine particles are continuously integrated with each other.

  The substrate may be a flat plate shape or a container shape as long as it can support the fine particles and thus the functional elements. The substrate is attached to the product with the functional element fixed. For example, in a dye-sensitized solar cell, a glass substrate coated with a transparent conductive film may be used as a base material.

A dispersion liquid in which fine particles are dispersed in a dispersion medium may be applied to a substrate. As the dispersion medium, water, ethanol, acetone or the like can be used.
More preferably, the fine particles applied (arranged) on the substrate are pressurized. As a result, the fine particles gather and the arrangement density increases, the fine particle nuclei of the adjacent fine particles can be brought into contact with each other, and the gel-like precursors of the adjacent fine particles can be reliably continuous. The pressurization may be performed, for example, using a flat press machine having a flat press plate, or using a roll press machine having a roller. Adjust the pressure appropriately. If the applied pressure is too large, the three-dimensional network structure of the fine particle aggregate may be destroyed, the fine particle nuclei may be damaged, or the substrate may be damaged. If the applied pressure is too small, contact of the fine particles and continuation of the gel-like precursor are insufficient.

  Using a spray gun, the fine particles may be sprayed vigorously on the base material, and the fine particles may collide with each other on the base material. Then, due to the impact of the collision, the fine particles come into contact with each other, and the gel-like precursors of the adjacent fine particles are continuously integrated.

[Baking process]
The fine particle aggregate is heated, and the precursor is fired. The firing temperature is preferably about 400 to 600 ° C. When the firing temperature is too high, the burden on the firing apparatus is large. If the firing temperature is too low, it cannot be fired sufficiently. Firing may be performed by heat treatment, or may be performed by treatment such as microwave, UV irradiation, or plasma irradiation.

  By the firing step, the gel-like precursor is sintered to become a solid-state functional film. Further, the dispersion medium is removed by evaporation. Adjacent fine particle functional films are in a continuous state without intervening the interface. When the functional film is crystalline, the crystal plane directions of the functional films of adjacent fine particles are aligned with each other and are crystallized integrally. Therefore, the energy barrier at the grain boundary of the fine particle aggregate can be reduced. As a result, the performance of the functional element can be improved.

Next, specific embodiments in which the present invention is applied to a dye-sensitized solar cell will be described with reference to the drawings.
As shown in FIG. 1, the dye-sensitized solar cell 1 includes a support base 10, a photoelectric conversion element 20, an electrolyte layer 30, and a counter electrode 40.

  The support base 10 includes a transparent substrate 11 and a transparent electrode 12. The transparent substrate 11 is composed of, for example, a glass substrate. A transparent electrode 12 is coated on the surface of the transparent substrate 11. The transparent electrode 12 is made of a transparent conductive material such as fluorine-added tin oxide or indium tin oxide, and has a thin film shape.

  A photoelectric conversion element 20 is laminated on the transparent electrode 12 in a film shape. The photoelectric conversion element 20 is a functional element having a photoelectric conversion function. The photoelectric conversion element 20 includes an aggregate 21 of a large number of fine particles 22. The fine particle aggregate 21 has a three-dimensional network structure. As a result, the photoelectric conversion element 20 is a porous body.

  Each fine particle 22 constituting the fine particle aggregate 21 has a fine particle nucleus 23 and a semiconductor film 24. The fine particle nuclei 23 are made of glass of a translucent material, but are not limited to this, and may be made of resin, ceramic, metal, or the like. The fine particle nucleus 23 may be composed of a semiconductor, may be composed of the same semiconductor component as the semiconductor film 24, and may be composed of, for example, rutile type titanium oxide. The fine particle nucleus 23 has a spherical shape with a controlled particle size. The particle diameter of the fine particle nucleus 23 is, for example, about 1 nm to 1 μm, and preferably about 1 nm to 30 nm.

The surface of the fine particle nucleus 23 is covered with a semiconductor film 24 as a functional film. As a material of the semiconductor film 24, it is preferable to use titanium oxide. Here, anatase-type titanium oxide is used as the material of the semiconductor film 24. Anatase-type titanium oxide is an n-type metal oxide semiconductor that transports electrons and is a kind of metal chalcogenide.
As shown by a broken line in FIG. 1, the semiconductor film 24 carries a sensitizing dye 26. As the sensitizing dye 26, for example, a ruthenium complex dye is used.

  The thickness of the semiconductor film 24 is, for example, about 1 nm to 100 nm, and preferably about 1 nm to 10 nm. Further, the thickness of the semiconductor film 24 is preferably 1/10 or less of the absorption wavelength of the sensitizing dye 26. In general, the absorption wavelength of the sensitizing dye 26 is included in the wavelength range of visible light, and is, for example, about 300 to 800 nm.

  The semiconductor film 24 cooperates with the sensitizing dye 26 to exhibit a photoelectric conversion function, and the semiconductor film 24 alone exhibits a charge transport function. That is, when light is absorbed by the sensitizing dye 26 and the electrons of the sensitizing dye 26 are excited, the semiconductor film 24 takes in the excited electrons and transports them to the transparent electrode 12. Furthermore, the semiconductor film 24 has a semiconductor function that prevents backflow of electrons.

  Adjacent semiconductor films 24 of the fine particles 22 are integrally continuous. That is, the semiconductor film 24 straddles between the adjacent fine particle nuclei 23 without an interface. At the junction of adjacent fine particles 22, the crystal plane directions of the semiconductor films 24 of these fine particles 22 are aligned with each other.

  The electrolyte layer 30 is filled between the photoelectric conversion element 20 and the counter electrode 40. A part of the electrolyte layer 30 is filled inside the porous photoelectric conversion element 20. The electrolyte layer 30 is composed of an electrolyte solution. As the electrolyte solution, for example, a redox pair of iodide ions / triiodide ions is used.

  The counter electrode 40 is made of a transparent conductive film and faces the support substrate 10. A catalyst 42 is supported on the surface of the counter electrode 40 facing the support substrate 10. For example, platinum is used as the catalyst 42.

A method for producing the dye-sensitized solar cell 1 will be described.
[Precursor generation step]
For example, using an organic titanium compound such as titanium tetrapropoxide as a starting material, the starting material is dissolved in a solvent such as isopropyl alcohol, and the gel-like semiconductor film precursor 25 is prepared by a sol-gel method.

[Coating process]
As shown in FIG. 2, a gel-like precursor 25 is coated on the surface of the fine particle nucleus 23 to obtain fine particles 22 whose surface layer is a gel.

[Arrangement process]
The fine particles 22 are dispersed in a dispersion medium such as water, ethanol, and acetone to obtain a fine particle dispersion. This fine particle dispersion is applied (arranged) on the transparent electrode 12 of the substrate 10.

[Pressure process (aggregation process)]
The fine particle dispersion after application is pressurized. As a result, as shown in FIG. 3, the fine particles 22 are gathered to increase the arrangement density, and the fine particle aggregate 21 having a three-dimensional network structure is formed. In the fine particle aggregate 21, the fine particle nuclei 23 of the adjacent fine particles 22 are in contact with each other. Further, the gel-like semiconductor film precursors 25 of the adjacent fine particles 22 are continuously integrated.

[Baking process]
Next, the base material 10 is put into a firing furnace, and the fine particle aggregate 21 on the base material 10 is fired. The firing temperature is preferably about 400 to 600 ° C, more preferably about 500 ° C. The firing (condensation reaction) temperature can be lower than the firing (solid-phase reaction) temperature of the titanium oxide crystal particles in a general dye-sensitized solar cell manufacturing technique (see Patent Document 2). The firing time is, for example, about 1 hour, but is not limited thereto. As a baking furnace, a heating furnace may be used, a microwave baking furnace may be used, an ultraviolet irradiation apparatus may be used, and a plasma irradiation apparatus may be used.

  By performing the firing step, the dispersion medium is evaporated and removed. Furthermore, as shown in FIG. 4, the gel-like precursor 25 is sintered (condensed) and crystallized to obtain a semiconductor film 24 made of titanium oxide crystals. At the time of crystallization, the crystal plane directions of the semiconductor films 24 of the adjacent fine particles 22 are aligned with each other, and the semiconductor films 24 of the adjacent fine particles 22 are continuously integrated with each other without an interface. In this way, the fine particle aggregate 21 is obtained. The fine particle aggregate 21 has a porous structure in which the fine particles 22 are combined in a three-dimensional network.

[Dye support process]
Subsequently, the fine particle aggregate 21 is immersed in a sensitizing dye-containing solution. As a result, the sensitizing dye 26 is carried on the surface of the semiconductor film 24 as shown in FIG. Thus, the photoelectric conversion element 20 is formed.

[Counter electrode placement process, electrolyte filling process]
Next, the counter electrode 40 is disposed above the photoelectric conversion element 20 with the electrolyte layer 30 interposed therebetween. After disposing the counter electrode 40, the electrolyte layer 30 may be filled. Thereby, the dye-sensitized solar cell 1 is obtained.

In the photoelectric conversion element 20 of the dye-sensitized solar cell 1, not only are the fine particles 22 laminated in a three-dimensional network shape to be porous, but also the semiconductor films 24 of the adjacent fine particles 22 are integrally continuous. Therefore, the grain boundary resistance (energy barrier) between adjacent fine particles 22 is sufficiently small. Therefore, even if the particle diameter of the fine particle 22 is small and the grain boundary density of the fine particle aggregate 21 is high, the internal resistance of the fine particle aggregate 21 can be sufficiently suppressed. Therefore, the particle size of the fine particles 22 can be sufficiently reduced without increasing the internal resistance of the fine particle aggregate 21, and the specific surface area of the photoelectric conversion element 20 can be increased. As a result, the photoelectric conversion efficiency of the photoelectric conversion element 20 and thus the power generation efficiency can be sufficiently increased.
By setting the thickness of the semiconductor film 24 to 1/10 or less of the absorption wavelength of the sensitizing dye 26, the semiconductor film 24 can sufficiently exhibit the photoelectric conversion function and the charge transport function, and the semiconductor film 24 is necessary. The increase in the particle diameter of the fine particles 22 can be prevented by preventing the increase in thickness. Therefore, the specific surface area of the photoelectric conversion element 20 can be reliably increased.
Since the fine particle nuclei 23 are made of glass of a translucent material, incident light can sufficiently reach the inside of the photoelectric conversion element 20, and the photoelectric conversion efficiency and thus the power generation efficiency can be improved.
When the fine particle nuclei 23 are omitted and only the semiconductor film precursor 25 is applied to the substrate 10 and fired, a photoelectric conversion element made of a nonporous dense semiconductor film is formed. Therefore, the specific surface area of the photoelectric conversion element is small, and it is difficult to ensure sufficient power generation efficiency.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, the functional film may be amorphous.
The functional film may contain a metal compound (for example, metal nitride) other than the metal chalcogenide in addition to or instead of the metal chalcogenide.
The fine particle aggregate may have a two-dimensional network structure. The functional element may not have a porous or network structure depending on the application.
The method for producing the functional element and the method for producing the dye-sensitized solar cell may be modified as appropriate.
You may change suitably the order of each process of the manufacturing method of a functional element. You may change suitably the order of each process of the manufacturing method of a dye-sensitized solar cell. A plurality of processes may be executed in parallel. For example, the precursor generation step and the coating step may be performed in parallel. The assembly process and the firing process may be performed in parallel. As the dispersion liquid evaporates in the course of the firing step, the fine particles may gather. You may perform a pressurization process and a baking process in parallel.

It is sectional drawing which shows one Embodiment of this invention and shows the structure of a dye-sensitized solar cell typically. It is sectional drawing which shows typically the microparticles | fine-particles before the baking process in the said embodiment. It is sectional drawing which shows the manufacturing method of the said dye-sensitized solar cell typically in the state of an assembly process. It is sectional drawing which shows the manufacturing method of the said dye-sensitized solar cell typically in the state of a baking process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dye-sensitized solar cell 10 Base material 11 Transparent substrate 12 Transparent electrode 20 Photoelectric conversion element (functional element)
21 Fine particle assembly 22 Fine particle 23 Fine particle nucleus 24 Semiconductor film (functional film)
25 Precursor 26 Sensitizing dye 30 Electrolyte layer 40 Counter electrode 42 Catalyst

Claims (17)

A method for producing a functional element including a fine particle assembly,
A precursor generating step for generating a gel-like precursor to be a functional film responsible for the function of the functional element;
Coating the precursor on the surface of fine particle nuclei to obtain fine particles; and
An assembly step of assembling and arranging a large number of the fine particles;
A firing step of firing the aggregated fine particles;
A method of manufacturing a functional element, characterized in that   The method for producing a functional element according to claim 1, wherein a particle diameter of the fine particle nucleus is 5 nm to 1 μm.   3. The functional device according to claim 1, wherein the precursor is generated by a sol-gel method using at least one compound selected from a metal salt, a metal alkoxide, and an organometallic complex as a starting material. Production method.   The functional compound according to claim 3, wherein the compound contains at least one metal element selected from Ti, Zn, Sn, In, W, V, Al, Fe, Sr, and Ga. Method.   The functional film generated from the precursor by the firing contains a metal chalcogenide compound containing at least one metal element selected from Ti, Zn, Sn, In, W, V, Al, Fe, Sr, and Ga. The method for manufacturing a functional element according to claim 1, wherein:   The method for producing a functional element according to claim 1, wherein the precursor contains an organic semiconductor.   In the said assembly | attachment process, the said microparticles | fine-particles are arrange | positioned on a base material and it pressurizes, The manufacturing method of the functional element of any one of Claims 1-6 characterized by the above-mentioned.   In the said assembly | attachment process, the said microparticles | fine-particles are sprayed on a base material so that it may collide with each other, The manufacturing method of the functional element of any one of Claims 1-7 characterized by the above-mentioned. A method for producing a dye-sensitized solar cell, comprising producing a functional element by the method according to claim 1 and using the functional element as a photoelectric conversion element,
Production of a dye-sensitized solar cell, wherein the precursor is a precursor of a semiconductor film, the fine particles are aggregated on a transparent electrode, fired, and a sensitizing dye is supported on the fired fine particle aggregate Method.   It is composed of an aggregate of fine particles, the fine particles have fine particle nuclei and a functional film coated on the surface of the fine particle nuclei, and the functional films of adjacent fine particles are integrally continuous. Functional element.   The functional device according to claim 10, wherein the aggregate of fine particles has a three-dimensional network structure.   The functional element according to claim 10 or 11, wherein a particle diameter of the fine particle nucleus is 1 nm to 1 µm.   The functional element according to claim 10, wherein the functional film has a thickness of 1 nm to 100 nm.   11. The functional film contains a metal chalcogenide compound containing at least one metal element selected from Ti, Zn, Sn, In, W, V, Al, Fe, Sr, and Ga. The functional element according to any one of ˜13.   It is a dye-sensitized solar cell which has a functional element of any one of Claims 10-14 as a photoelectric conversion element, Comprising: The said functional film is a semiconductor film which carry | supported the sensitizing dye, The collection of the said microparticles | fine-particles A dye-sensitized solar cell, wherein the body is in contact with the transparent electrode in a three-dimensional network structure.   The dye-sensitized solar cell according to claim 15, wherein the thickness of the semiconductor film is 1/10 or less of the absorption wavelength of the sensitizing dye.   The dye-sensitized solar cell according to claim 15 or 16, wherein the fine particle nuclei are made of a translucent material.

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