JP2009037779A - Photoelectric conversion element, manufacturing method of electron transport layer, manufacturing method of the photoelectric conversion element, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element capable of realizing higher photoelectric conversion efficiency, a manufacturing method of an electron transport layer capable of efficiently manufacturing an electron transport layer which can smoothly accept electrons from redox ions, a manufacturing method of a photoelectric conversion element, capable of efficiently manufacturing a photoelectric conversion element, equipped with such an electron transport layer, and an electronic equipment of high reliability, equipped with such a photoelectric conversion element. <P>SOLUTION: A solar cell 1 is provided with a first electrode 3 fitted on a base board 2, a second electrode 6 set facing the first electrode 3 and supported by an opposed base board 7, an electron transport layer 4 positioned at a first electrode 3 side between the electrodes 3, 6, a dye layer D, in contact with the electron transport layer 4, and an electrolyte layer 5 positioned in between the electron transport layer 4 and the second electrode 6 containing electrolyte solution containing the redox ions. The electron transport layer 4 is structured of a dense layer 41 and an aggregate of fibrous matters, constituted of a semiconductor material and is equipped with a porous part 42 containing holes of a size large enough for the redox ion to pass through. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element, a method for manufacturing an electron transport layer, a method for manufacturing a photoelectric conversion element, and an electronic device.

  2. Description of the Related Art Conventionally, photoelectric conversion elements using silicon, so-called solar cells, have attracted attention as environmentally friendly power supplies. Among solar cells using silicon, there are single crystal silicon type solar cells used for artificial satellites and the like. However, as practical ones, especially solar cells using polycrystalline silicon and amorphous silicon are used. Practical use of solar cells for industrial use and home use has begun.

However, all of these solar cells using silicon are expensive to manufacture and require a great deal of energy for manufacturing, and thus cannot always be said to be energy-saving power sources.
A dye-sensitized solar cell that has been developed as a next-generation solar cell to replace this, has a low manufacturing cost, and has a low manufacturing energy has been proposed.

The dye-sensitized solar cell is configured to have a semiconductor layer (electron transport layer) supporting a dye and an electrolyte solution between a transparent electrode and a counter electrode, and electrons and holes generated in the dye by receiving light ( Carriers) are drawn into a transparent electrode and a counter electrode, respectively, and generate a potential difference therebetween.
For example, Patent Document 1 proposes a dye-sensitized solar cell in which a semiconductor layer (electron transport layer) is formed of a titanium oxide polycrystalline material. The dye is adsorbed on the surface of the titanium oxide polycrystalline material, and electrons generated in the dye move to the electrode through the semiconductor layer. This creates a potential difference between the two electrodes.

However, the polycrystalline material of titanium oxide has a problem that the electron transport ability to move electrons from the dye to the electrode is not sufficient.
In order to solve this problem, an attempt has been made to improve the photoelectric conversion efficiency by providing a light reflecting layer that reflects incident light.
However, this light reflecting layer causes a problem that the movement of redox ions responsible for the movement of carriers in the electrolytic solution is hindered. For this reason, the contact opportunity between a redox ion and a pigment | dye reduces, and photoelectric conversion efficiency cannot fully be improved.
Japanese Patent No. 2664194

  An object of the present invention is to provide a photoelectric conversion element capable of realizing higher photoelectric conversion efficiency, a method for producing an electron transport layer capable of efficiently producing an electron transport layer capable of smoothly receiving electrons from the redox ions, and such an electron transport layer. It is providing the manufacturing method of the photoelectric conversion element which can manufacture the photoelectric conversion element provided with efficiently, and a reliable electronic device provided with this photoelectric conversion element.

Such an object is achieved by the present invention described below.
The photoelectric conversion element of the present invention includes a first electrode,
A second electrode provided opposite to the first electrode;
An electron transport layer located between the first electrode and the second electrode;
A dye layer in contact with the electron transport layer;
An electrolyte layer located between the electron transport layer and the second electrode and containing an electrolyte containing redox ions;
At least a portion on the electrolyte layer side of the electron transport layer is composed of a porous portion made of a fibrous material made of a semiconductor material and capable of passing the redox ions. .
Thereby, the photoelectric conversion element which can implement | achieve higher photoelectric conversion efficiency is obtained.

In the photoelectric conversion element of the present invention, the semiconductor material preferably contains a metal oxide as a main component.
Metal oxides can exist stably in the atmosphere and are inexpensive. For this reason, a long-life and inexpensive photoelectric conversion element can be obtained by using a metal oxide as a semiconductor material.

In the photoelectric conversion element of the present invention, it is preferable that the fibrous material has an average fiber diameter of 1 μm or less and substantially no fiber having a fiber diameter of 5 μm or more.
As a result, pores large enough for redox ions to pass through more reliably are formed inside and on the surface of the porous portion. As a result, there are more opportunities for contact between the redox ions and the dye layer.

In the photoelectric conversion element of the present invention, the aggregate of the fibrous materials preferably has a network structure in which a plurality of the fibrous materials are three-dimensionally combined.
Thereby, a plurality of pores are almost uniformly distributed inside and on the surface of the porous portion. Thereby, photoelectric conversion is performed uniformly throughout the electron transport layer. As a result, the part which does not contribute to photoelectric conversion in an electron carrying layer can be decreased, and the photoelectric conversion efficiency of a photoelectric conversion element can be improved more.

In the photoelectric conversion element of the present invention, a part of the electron transport layer is composed of a porous portion composed of an aggregate of the fibrous materials,
The portion other than the porous portion of the electron transport layer is preferably composed of a dense portion composed of an aggregate of particles having an average particle diameter smaller than the average fiber diameter of the fibrous material.
Thereby, the dense part has a high density and a large surface area. As a result, more dense pigment can be carried on the dense part. Then, more redox ions can come into contact with the dense part having a large amount of dye.

In the photoelectric conversion element of the present invention, the light reflectance of the porous portion in the electron transport layer is preferably larger than the light reflectance of the dense portion.
Thereby, light can be confined more efficiently in the electron transport layer. As a result, the amount of light used for photoelectric conversion is further increased, and the photoelectric conversion efficiency of the photoelectric conversion element can be increased.

In the photoelectric conversion element of the present invention, it is preferable that the porous portion is fixed to the dense portion.
Thereby, since the porous part can be in direct contact with the dense part, the electron transfer between them can be performed smoothly.
In the photoelectric conversion element of the present invention, it is preferable that the porous portion is bonded to the dense portion using a metal oxide or a precursor thereof.
Thereby, the dense part and the porous part can be more strongly joined while preventing the electron mobility from being significantly lowered at the joining interface between the dense part and the porous part. For this reason, a highly reliable electron transport layer that can prevent interfacial peeling over a long period of time is obtained.

In the photoelectric conversion element of the present invention, the average thickness of the porous portion is preferably 10 to 80% of the average thickness of the dense portion.
Thereby, the ratio of a dense part and a porous part can be optimized, and the light absorption rate in an electron carrying layer can fully be raised. As a result, the amount of light used for photoelectric conversion is further increased, and the photoelectric conversion efficiency of the photoelectric conversion element can be increased.

In the photoelectric conversion element of the present invention, the pore size of the porous portion is preferably 30 to 30000 times the ion diameter of the redox ion.
Thereby, the redox ions can smoothly move inside the porous portion without hindering the movement of the redox ions.
In the photoelectric conversion element of the present invention, it is preferable that the redox ions in the electrolytic solution are substantially I ₃ ⁻ and I ⁻ .
Thereby, the photoelectric conversion efficiency of a photoelectric conversion element can be raised more.

In the photoelectric conversion element of the present invention, when the content of I ₃ ⁻ is A [mol / L] and the content of I ⁻ is B [mol / L] in the electrolytic solution, A / (A + B) is It is preferable that it is 0.3-0.6.
Thereby, the efficiency of carrier movement of the electrolytic solution is particularly high, and the photoelectric conversion efficiency of the photoelectric conversion element can be particularly increased.

The method for producing an electron transport layer of the present invention comprises a step of producing a fiber structure containing a precursor of the semiconductor material on a substrate for recovery from a solution containing the precursor of the semiconductor material;
Peeling the fiber structure from the recovery substrate;
Firing the peeled fiber structure and changing it to an aggregate of fibrous materials composed of a semiconductor material;
An electron transport layer in which at least a portion on the side opposite to the electrode is formed of a porous portion through which redox ions can pass by laminating the aggregate of the fibrous materials on one surface side of the layered electrode. Forming a step,
An electron transport layer used for a photoelectric conversion element is manufactured.
As a result, heat treatment at a higher temperature is possible, so that the range of heat treatment conditions can be expanded. Further, according to the method using the recovery substrate, it is possible to avoid the first electrode being exposed to the heat treatment at a high temperature. For this reason, the range of selection of the constituent material of the first electrode is expanded. As a result, for example, a photoelectric conversion element having high photoelectric conversion efficiency and excellent flexibility can be obtained.

In the method for producing an electron transport layer of the present invention, a dense part composed of an aggregate of particles having an average particle diameter smaller than the average fiber diameter of the fibrous material is previously formed on one surface of the electrode. And
After that, the fibrous material aggregate is laminated on the dense portion, and the solution containing the precursor of the semiconductor material is infiltrated into the laminated fibrous aggregate, and then the electrode is baked. Thus, it is preferable to fix the dense part and the porous part.
Thereby, the electron carrying layer which can confine light efficiently can be manufactured reliably.

The method for producing an electron transport layer of the present invention comprises a step of laminating a fiber structure containing a precursor of the semiconductor material on one surface side of a layered electrode from a solution containing a precursor of the semiconductor material;
A porous electrode through which redox ions can pass through at least a portion opposite to the electrode by firing a layered electrode laminated with the fiber structure and changing it to an aggregate of fibrous materials composed of a semiconductor material. A step of forming an electron transport layer composed of parts,
An electron transport layer used for a photoelectric conversion element is manufactured.
Thereby, the electron carrying layer which can receive the electron from a redox ion smoothly can be manufactured efficiently.

In the method for producing an electron transport layer of the present invention, a dense part composed of an aggregate of particles having an average particle diameter smaller than the average fiber diameter of the fibrous material is previously formed on one surface of the electrode. And
Then, it is preferable to laminate | stack the said fiber structure on this dense part.
Thereby, the electron carrying layer which can confine light efficiently can be manufactured reliably.

In the manufacturing method of the electron carrying layer of this invention, it is preferable to produce the said fiber structure from the said solution by the electrospinning method.
As a result, the solution can be efficiently formed into very fine fibers, and finally fine fiber particles can be efficiently produced.
The photoelectric conversion element manufacturing method of the present invention includes a step of forming a dye layer so as to be in contact with the electron transport layer manufactured by the electron transport layer manufacturing method of the present invention,
Disposing a counter electrode on the opposite side of the electrode via the electron transport layer and the dye layer;
Filling the electrolyte solution containing the redox ions between the electrode and the counter electrode.
Thereby, the photoelectric conversion element which can implement | achieve higher photoelectric conversion efficiency can be manufactured efficiently.
The electronic device of the present invention includes the photoelectric conversion element of the present invention.
As a result, a highly reliable electronic device can be obtained.

Hereinafter, a photoelectric conversion element, a method for manufacturing an electron transport layer, a method for manufacturing a photoelectric conversion element, and an electronic apparatus according to the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.
Hereinafter, the case where the photoelectric conversion element of this invention is applied to a solar cell is demonstrated to an example.
<Photoelectric conversion element>
<< First Embodiment >>
First, a first embodiment of a solar cell will be described.

FIG. 1 is a longitudinal sectional view schematically showing a first embodiment when the photoelectric conversion element of the present invention is applied to a solar cell, and FIG. 2 is an enlarged view schematically showing a part of the solar cell shown in FIG. 3 and 5 are schematic diagrams for explaining a method of manufacturing the solar cell shown in FIG. In the following description, for convenience of explanation, in FIGS. 1 to 5, the upper side is described as “upper” and the lower side is described as “lower”.
A solar cell 1 shown in FIG. 1 includes a first electrode 3 provided on a substrate 2, and a second electrode (counter electrode) supported by a counter substrate 7 disposed to face the first electrode 3. ) 6, between these electrodes 3, 6, the electron transport layer 4 located on the first electrode 3 side, the dye layer D in contact with the electron transport layer 4, the electron transport layer 4 and the second electrode 6 And an electrolyte layer 5 in contact with the dye layer D. A partition wall 8 is provided over the entire periphery of the edge between the electrodes 3 and 6. An electron transport layer 4, a dye layer D, and an electrolyte layer 5 are provided in a space defined by the electrodes 3 and 6 and the partition walls 8.

Further, the electrolyte layer 5 has an electrolytic solution containing redox ions.
In such a solar cell 1, when light enters, electrons are excited mainly in the dye layer D, and electrons (e ⁻ ) and holes (h ⁺ ) are generated. Among these, electrons move to the electron transport layer 4, holes move to the electrolyte layer 5, and a potential difference (photoelectromotive force) is generated between the first electrode 3 and the second electrode 6. A current (photoexcitation current) flows through the circuit 10.

Hereinafter, the configuration of each unit will be described.
In the present embodiment, the substrate 2 and the counter substrate 7 are for supporting the first electrode 3, the electron transport layer 4, the dye layer D, and the second electrode 6, and are configured by flat plate members. ing.
As shown in FIG. 1, the solar cell 1 according to the present embodiment receives, for example, light such as sunlight (hereinafter simply referred to as “light”) from the substrate 2 and the first electrode 3 side described later. It is intended to be used (irradiated). For this reason, each of the substrate 2 and the first electrode 3 is preferably substantially transparent (colorless transparent, colored transparent, or translucent). Thereby, light can be efficiently made to reach the dye layer D described later.

Examples of the constituent materials of the substrate 2 and the counter substrate 7 include a glass material, a ceramic material, a resin material, and a metal material such as aluminum.
Of these, the constituent materials of the substrate 2 and the counter substrate 7 are particularly preferably resin materials. Since the resin material is rich in flexibility, the flexibility of the solar cell 1 can be increased. Moreover, since the resin material is lightweight, the portability and manufacturability of the solar cell 1 can also be improved.

  Here, as a resin material constituting the substrate 2 and the counter substrate 7, for example, polyolefin such as polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVAC), modified polyolefin, polyamide (example: Nylon 6), liquid crystal polymers such as thermoplastic polyimide, aromatic polyester, polyphenylene oxide, polyphenylene sulfide (PPS), polysulfone (PSU), polycarbonate (PC), polymethyl methacrylate, polyether, polyether ether ketone, polyether imide Polyacetal, styrene, polyvinyl chloride, polyurethane, polyester such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, polybutadiene Various types of thermoplastic resins such as transpolyisoprene, fluororubber, chlorinated polyethylene, and the like, copolymers, blends, polymer alloys, etc. mainly include one or two of these The above can be mixed and used.

Among these, as the resin material, polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polysulfone (PSU), polypropylene (PP) or polyimide (PI) is preferably used. It is done.
Further, polycarbonate, polyethylene terephthalate or polyethylene naphthalate is more preferable. Since these resin materials are relatively excellent in heat resistance and chemical resistance, a substrate made of such a resin material has excellent durability in heat treatment and liquid phase process when the solar cell 1 is manufactured. .

In addition, since these resin materials have high translucency, more light can reach the dye layer D, and the photoelectric conversion efficiency of the solar cell 1 can be increased. Furthermore, since it is cheap and easily available, there is an advantage that the manufacturing cost of the solar cell 1 can be reduced.
The average thicknesses of the substrate 2 and the counter substrate 7 are appropriately set depending on the constituent material, the use of the solar cell 1 and the like, and are not particularly limited, but can be set as follows, for example.

  When the substrate 2 and the counter substrate 7 are each made of a hard material, the average thickness is preferably about 0.1 to 1.5 mm, and more preferably about 0.3 to 1.2 mm. When the substrate 2 and the counter substrate 7 are each made of a flexible material, the average thickness is preferably about 0.5 to 500 μm, and more preferably about 10 to 300 μm.

Note that the counter substrate 7 may be omitted as necessary.
A first electrode 3 is provided on the substrate 2 (one surface side of the substrate 2). The first electrode 3 receives electrons generated in the dye layer D, which will be described later, via the electron transport layer 4 and transmits the electrons to the external circuit 10 connected thereto.
Examples of the constituent material of the first electrode 3 include metal oxides such as indium tin oxide (ITO), tin oxide containing fluorine atoms (FTO), indium oxide (InO ₂ ), and tin oxide (SnO ₂ ). Materials, metal materials such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, tantalum or alloys containing them, carbon materials such as graphite, etc. Two or more types can be used in combination (for example, as a multi-layer laminate).

The average thickness of the first electrode 3 is appropriately set depending on the constituent material thereof, the use of the solar cell 1, and the like, and is not particularly limited, but can be set as follows, for example.
When the first electrode 3 is made of a metal oxide material (transparent conductive metal oxide material), the average thickness is preferably about 0.05 to 5 μm, and preferably about 0.1 to 1.5 μm. It is more preferable that Further, when the first electrode 3 is made of a metal material or a carbon material, the average thickness is preferably about 0.01 to 1 μm, more preferably about 0.03 to 0.1 μm. .

In addition, the 1st electrode 3 is not limited to the shape shown in figure, For example, the thing etc. of the shape which has several comb teeth may be sufficient. In this case, since the light passes between the plurality of comb teeth and reaches the dye layer D, the first electrode 3 may not be substantially transparent. Thereby, the range of selection of the constituent material, the formation method (manufacturing method), and the like of the first electrode 3 can be expanded.
The first electrode 3 can also be used by combining (for example, laminating) such a comb-like electrode and a layered electrode.

An electron transport layer 4 is provided on the first electrode 3.
The electron transport layer 4 has at least a function of transporting electrons generated in the dye layer D. For this reason, the electron transport layer 4 is made of an electron transport material.
In such an electron transport layer 4, as shown in FIGS. 1 and 2, the portion on the first electrode 3 side is an aggregate of granular bodies 410 of an electron transport material (hereinafter referred to as “dense portion”). 41, and the portion on the electrolyte layer 5 side is composed of an aggregate (hereinafter referred to as “porous portion”) 42 of needles (fibers) 420 of an electron transport material.

Further, as shown in FIG. 2, the dense part 41 and the porous part 42 carry the dye d inside and on the surface, respectively.
Here, each of the dense portion 41 and the porous portion 42 has a large number of pores for supporting the dye d. In the present specification, these are represented by the ratio (volume) of the pores. Rate). That is, the dense portion 41 is called a “dense portion” because it is relatively dense compared to the porous portion 42, and the porous portion 42 is relatively porous compared to the dense portion 41. Therefore, it shall be called “porous part”.

1 and 2, the size of the granular body 410 constituting the dense portion 41 and the size of the needle-like body 420 constituting the porous portion 42 are exaggerated with respect to the size of the solar cell 1, respectively. It is shown as
Here, the electron transport material is not particularly limited as long as it has a function of transporting electrons, and examples thereof include a semiconductor material and a metal material.

Among these, as the semiconductor material, various inorganic or organic n-type semiconductor materials can be used alone or in combination of two or more. Among these, examples of the inorganic n-type semiconductor material include titanium oxide such as titanium dioxide (TiO ₂ ), titanium monoxide (TiO), and dititanium trioxide (Ti ₂ O ₃ ), zinc oxide (ZnO), and oxide. The main component is a metal oxide such as tin (SnO ₂ ). Metal oxides can exist stably in the atmosphere and are inexpensive. For this reason, by using a metal oxide as a semiconductor material, a long-life and inexpensive solar cell 1 can be obtained.

Among these, as a metal oxide, what has titanium dioxide as a main component is preferable. Titanium dioxide is particularly excellent in the ability to transport electrons and is highly sensitive to light, so that even metal oxide itself can generate electrons. As a result, the power generation efficiency (photoelectric conversion efficiency) of the solar cell 1 is further improved.
In addition, since the crystal structure of titanium dioxide is stable, semiconductor materials mainly composed of titanium dioxide have little secular change (deterioration) and stable performance even when exposed to harsh environments. It has the advantage that it can be obtained continuously for a long time.
Further, as titanium dioxide, any of those whose crystal structure is mainly composed of anatase type, those composed mainly of rutile type, and a mixture of anatase type and rutile type may be used. Good.

In addition, examples of the metal material include gold, silver, platinum, and the like, and one or more of these can be used in combination.
The particle (particle) 410 of the electron transport material has a shape that is relatively close to a sphere. Such a granular material 410 is easy to manufacture and tends to have a high density when a plurality of granular materials 410 are assembled. For this reason, the dense part 41 has a large surface area. As a result, the dense portion 41 can carry more dye d.

Moreover, as long as the surfaces of the plurality of adjacent particles 410 made of a plurality of electron transport materials are in contact with each other, they can take charge of electron transport, but are preferably joined (necked). Thereby, the electron mobility between each granular material 410 can be raised. As a result, the photoelectric conversion efficiency of the solar cell 1 can be increased.
The average particle size of the granular material 410 is not particularly limited, but is preferably about 1 nm to 1 μm, and more preferably about 5 to 50 nm. Thereby, the dense part 41 having a larger surface area can be configured while maintaining the manufacturability of the granular material 410.
Moreover, although the average thickness of the dense part 41 is not specifically limited, It is preferable that it is about 3-30 micrometers, and it is more preferable that it is about 5-20 micrometers. By setting the average thickness of the dense portion 41 within the above range, the function of the dense portion 41 is sufficiently exhibited, and the dense portion 41 is prevented from being too thick to increase the electrical resistance component. can do.

  On the other hand, the needle-like body 420 of the electron transport material has a long and thin fiber shape (needle shape). For this reason, in the aggregate formed by a plurality of needle-like bodies 420 having such a shape, that is, the porous portion 42, the needle-like bodies 420 interfere with each other to easily form a gap, and the packing density decreases. . Therefore, the porous portion 42 has a large number of pores inside and on the surface. As a result, as shown in FIG. 2, the pores have a size that allows the redox ions 51 in the electrolyte layer 5 to sufficiently pass therethrough.

  By the way, the redox ion 51 is an ion that can be responsible for carrier movement by mutually taking an oxidation / reduction state. When the redox ions 51 can pass through the inside of the porous portion 42, that is, the inside of the electron transport layer 4, there are more opportunities for contact between the redox ions 51 and the dye layer D, and carriers generated in the dye layer D (positive Hole) can be efficiently moved to the second electrode 6 via the redox ions 51.

  In particular, as shown in FIG. 2, when the electron transport layer 4 is composed of a laminated body of the dense portion 41 and the porous portion 42, the dye d carried on the porous portion 42 can reduce the redox ions 51. Electrons move efficiently. In addition, since the dense portion 41 carries more dye d, more electrons move with respect to the redox ions 51. As a result, for example, increasing the amount of electron movement in the electron transport layer 4 can increase the photoelectric conversion efficiency of the solar cell 1 as compared with the case where the entire electron transport layer 4 is formed of a dense portion.

Such needle-like bodies 420 can bear electron transport as long as their surfaces are in contact with each other, but are preferably joined (necked). Thereby, the electron mobility between each acicular body 420 can be raised. As a result, the photoelectric conversion efficiency of the solar cell 1 can be increased.
Here, the needle-like body 420 has an average fiber diameter of preferably 1 μm or less, and more preferably 0.7 μm or less. Moreover, it is preferable that there is substantially no fiber having a fiber diameter of 5 μm or more.

  Here, the fact that there is substantially no fiber having a fiber diameter of 5 μm or more means that a fiber having a fiber diameter in the above range is not observed at any point in an electron microscope. When fibers having an average fiber diameter exceeding 5 μm are included, the ratio of the holes for allowing redox ions 51 to pass through the inside and the surface of the porous portion 42 is not preferable.

Further, it is preferable that the fiber length of the needle-like body 420 does not substantially have a length of 60 μm or less.
Here, the fact that there is substantially no fiber having a fiber length of 60 μm or less means that both ends of the fiber are not observed in 2000 times electron microscope observation centering on an arbitrary point. When fibers having a fiber length of 60 μm or less are included, the ratio of the holes for allowing redox ions 51 to pass inside and on the surface of the porous portion 42 is not preferable.

Note that the ion diameter of the redox ion 51 shown in FIG. 2 is exaggerated with respect to the size of the pores formed in the porous portion 42.
Moreover, although the average thickness of the porous part 42 is not specifically limited, It is preferable that it is about 1-15 micrometers, and it is more preferable that it is about 3-10 micrometers. By setting the average thickness of the porous portion 42 within the above range, the function of the porous portion 42 is fully exhibited, and the porous portion 42 is prevented from being too thick to increase the electrical resistance component. Can do.

  Moreover, in the porous part 42 shown in FIG. 1 and FIG. 2, the network-like structure where the some acicular body 420 is combined three-dimensionally is constructed | assembled. In the porous portion 42 having such a structure, a plurality of pores formed inside and on the surface thereof are distributed substantially uniformly throughout the entire porous portion 42. In the electron transport layer 4 having such a structure, photoelectric conversion is performed uniformly throughout. As a result, a portion of the electron transport layer 4 that does not contribute to photoelectric conversion can be reduced, and the photoelectric conversion efficiency of the solar cell 1 can be further increased.

  Here, as described above, since the redox ions 51 can pass through the pores formed in and on the surface of the porous portion 42, the size thereof is sufficiently larger than the ion diameter of the redox ions 51. It is preferable. Specifically, the pore size is preferably about 30 to 60,000 times, more preferably about 50 to 30000 times the ion diameter of the redox ion 51. If the holes have such a size, the redox ions 51 can smoothly move inside the porous portion 42 without hindering the movement of the redox ions 51. For this reason, the carrier mobility in the solar cell 1 becomes high, and the photoelectric conversion efficiency can be further improved.

More specifically, the size (inner diameter) of the holes varies depending on the ion diameter of the redox ions 51, but is preferably about 20 to 10000 nm, and more preferably about 50 to 5000 nm.
Here, the light reflectance of the porous portion 42 is preferably larger than the light reflectance of the dense portion 41. Thereby, light can be more efficiently confined in the electron transport layer 4. This is because the light transmitted through the dense portion 41 can be efficiently reflected to the dense portion 41 side by the porous portion 42, so that the light absorption rate in the dense portion 41 is improved. is there. As a result, the amount of light used for photoelectric conversion is further increased, and the photoelectric conversion efficiency of the solar cell 1 can be increased.

In this case, it is preferable that the porous portion 42 has a particularly high reflectance with respect to visible light. Thereby, the solar cell 1 which shows high photoelectric conversion efficiency especially with respect to sunlight is obtained.
The average thickness of the porous portion 42 is preferably about 10 to 80%, more preferably about 20 to 70% of the average thickness of the dense portion 41. By setting the average thickness of the porous portion 42 within the above range, the ratio of the dense portion 41 and the porous portion 42 can be optimized, and the light absorption rate in the electron transport layer 4 can be sufficiently increased. .

Further, the constituent material of the granular body 410 and the constituent material of the needle-like body 420 may be different from each other, but are preferably the same type. Thereby, the electron mobility between the dense part 41 and the porous part 42 can be further increased.
The porous portion 42 is integrally fixed to the dense portion 41 as shown in FIGS. 1 and 2. Thereby, since the porous part 42 can be in direct contact with the dense part 41, the electron movement between these is made smoothly. That is, it is possible to prevent the electron movement from being hindered at the interface between the porous portion 42 and the dense portion 41.

The electron transport layer 4 is in contact (supported) with the dye d by, for example, adsorption, bonding (covalent bond, coordinate bond), or the like.
As described above, the dye d has a function of generating electrons and holes by receiving light, and is supported on the surfaces of the granular body 410 and the needle-shaped body 420 as shown in FIG. Thereby, the electrons generated in the dye d can be efficiently transferred to the electron transport layer 4.

As this pigment | dye d, a pigment and dye can be used individually or in mixture. In addition, it is preferable to use a pigment from the viewpoint of less deterioration and deterioration over time and a dye from the viewpoint of better adsorbability (bonding) to the electron transport layer 4.
Here, as the pigment, for example, phthalocyanine pigment, azo pigment, anthraquinone pigment, azomethine pigment, quinophthalone pigment, isoindoline pigment, nitroso pigment, perinone pigment, quinacridone pigment, perylene pigment, Organic pigments such as pyrrolopyrrole pigments, dioxazine pigments, carbon pigments, chromate pigments, sulfide pigments, oxide pigments, hydroxide pigments, ferrocyanide pigments, silicate pigments Examples thereof include inorganic pigments such as pigments and phosphate pigments, and one or more of these can be used in combination.

On the other hand, as the dye, for _{example, RuL 2 (SCN) 2,} RuL ( manufactured by Solaronics, _{Inc.) 2 Cl 2, RuL 2 CN} 2, Rutenium535-bisTBA, [RuL 2 metal complexes such as _{(NCS 2) 2 H 2} O Examples include dyes, cyan dyes, xanthene dyes, azo dyes, hibiscus dyes, blackberry dyes, raspberry dyes, pomegranate juice dyes, chlorophyll dyes, and the like. Use one or more of these in combination. Can do. In addition, L in the said composition formula shows 2,2'-bipyridine, or its derivative (s).

  The space defined by the first electrode 3, the second electrode 6, and the partition wall 8 is filled with an electrolytic solution containing redox ions 51. The electrolytic solution also penetrates into the pores in the dense portion 41 and the pores in the porous portion 42. In the electrolyte layer 5 containing such an electrolytic solution, the redox ions 51 can come into contact with the dye d over a wide area, so that carriers are efficiently moved through the redox ions 51. As a result, the photoelectric conversion efficiency of the solar cell 1 can be increased.

The electrolyte solution included in the electrolyte layer 5 is liquid or gel.
Among these, liquid electrolytes include, for example, I / I ₃ series, Br / Br ₃ series, Cl / Cl ₃ series, F / F ₃ series halogen series, quinone / hydroquinone series redox electrolytes ( An electrolyte solution obtained by dissolving one or a combination of two or more of redox substances (electrolyte components) in a solvent (or a mixed solvent thereof) such as various water, acetonitrile, ethylene carbonate, propylene carbonate, polyethylene glycol, and the like. Can be configured.

Such a redox ion 51 preferably contains an I / I ₃ system, ie, I ₃ ⁻ and I ⁻ , more preferably substantially I ₃ ⁻ and I ^−. . The electrolytic solution containing such redox ions 51 can further increase the photoelectric conversion efficiency of the solar cell 1.
The concentration (content ratio) of the redox ions 51 in the electrolytic solution is not particularly limited, but is preferably about 0.1 to 25 wt%, and more preferably about 0.5 to 15 wt%.

In the I / I ₃ electrolyte, the ratio of I ₃ ⁻ and I ⁻ may be any, but the content of I ₃ ⁻ in the electrolyte is A [mol / L]. When the content of I ⁻ is B [mol / L], A / (A + B) is preferably about 0.3 to 0.6, more preferably about 0.4 to 0.5. . By setting the ratio of I ₃ ⁻ and I ^{− in} such a range, the efficiency of carrier movement of the electrolytic solution becomes particularly high, and the photoelectric conversion efficiency of the solar cell 1 can be particularly increased.

The gel electrolyte can be constituted by, for example, a liquid electrolyte as described above held in a gel substrate (gel substrate).
Examples of the gel base material include those mainly composed of thermoplastic resins, those mainly composed of thermosetting resins, those mainly composed of copolymers, and mainly composed of compounds having a siloxane bond. A thing etc. can be used, Furthermore, arbitrary 2 or more types of these can also be used in combination.

Among these, examples of the thermoplastic resin include polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), and the like. They can be used in combination.
Moreover, as a thermosetting resin, a polyimide resin (PI), an epoxy resin, a carboxylic acid resin, a urea resin etc. are mentioned, for example.

  The copolymer is obtained by polymerizing at least two types of compounds (copolymer precursors), for example, ionic polymerization (cationic polymerization, anionic polymerization), radical polymerization, or the like in combination. For example, epoxy copolymer, vinyl ether copolymer, oxedan copolymer, urethane acrylate copolymer, epoxy acrylate copolymer, ester acrylate copolymer, acrylate copolymer Examples include coalescence.

Accordingly, as the compound (copolymer precursor), for example, any two or more of urethane, polyacene, polyacetylene, polyethylene, polycarbon, polypyrrole, polyaniline, active sulfur, and the like are appropriately selected and used. be able to.
Examples of the compound having a siloxane bond include polysiloxane, polydimethylsiloxane, polyalkylphenylsiloxane, and polymetallosiloxane in which a part of silicon atoms is substituted with other metal atoms (for example, aluminum, titanium, etc.). .

The average thickness of the electrolyte layer 5 (excluding the portion entering the electron transport layer 4) is not particularly limited, but is preferably about 1 to 500 μm, and more preferably about 10 to 300 μm. More preferably, the thickness is about 10 to 100 μm.
A second electrode 6 facing the first electrode 3 is provided on the electrolyte layer 5 (on the side opposite to the first electrode 3).

Examples of the constituent material of the second electrode 6 include metal oxides such as indium tin oxide (ITO), tin oxide containing fluorine atoms (FTO), indium oxide (InO ₂ ), and tin oxide (SnO ₂ ). Materials, aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, alloys such as tantalum or alloys containing these, or various carbon materials such as graphite, etc. One kind or a combination of two or more kinds can be used.

Further, the second electrode 6 may be used by combining (for example, stacking) layered electrodes.
In addition, the average thickness of the second electrode 6 is appropriately set depending on the constituent material, the use of the solar cell 1, and the like, and is not particularly limited.
Such a solar cell 1 can be manufactured as follows, for example.

[1] First, a substrate 2 is prepared, and a first electrode 3 is formed on the substrate 2 as shown in FIG.
The first electrode 3 can be formed by, for example, a vapor deposition method, a sputtering method, a printing method, or the like.
[2] Next, the electron transport layer 4 is formed on the first electrode 3.
[2-1] First, a dispersion liquid in which a plurality of granules 410 are dispersed in a dispersion medium is applied onto the first electrode 3. Thereby, the liquid film 411 can be formed on the first electrode 3 as shown in FIG.
In this case, for example, a spin coating method, a dip coating method, a squeegee printing method, a screen printing method, a droplet discharge method, or the like is used.

[2-2] Next, the dispersion medium in the liquid coating 411 is volatilized and removed. Thereby, the liquid film 411 is dried and solidified to obtain a film.
As a method for removing the dispersion medium in the liquid film, for example, a method of natural drying, a method of blowing a gas such as air or nitrogen gas, a method of freeze drying, a method of heat treatment at a relatively low temperature, or the like can be performed. .

[2-3] Next, heat treatment is performed on the obtained coating film. By this heat treatment, the granular bodies 410 in the coating are partially joined (necked).
For example, when the granular material 410 is titanium oxide particles, the heat treatment temperature is preferably about 300 to 700 ° C., more preferably about 400 to 600 ° C.
The heat treatment time varies slightly depending on the heat treatment temperature, but is preferably about 1 to 180 minutes, more preferably about 5 to 60 minutes.

Examples of the heat treatment atmosphere include an oxidizing atmosphere and an inert atmosphere.
In this way, an aggregate of granular bodies 410 shown in FIG. 3C, that is, a dense portion 41 is obtained. As described above, since the dense portion 41 has a large number of pores inside and on the surface, it can carry a larger amount of dye. For this reason, the solar cell 1 with high photoelectric conversion efficiency is obtained.

[2-4] Next, a solution containing a precursor of an electron transport material is prepared.
Next, the solution is supplied onto the dense portion 41 while being formed into a fiber. The molding / supply method is not particularly limited, but it is preferable to use an electrospinning method as shown in FIG. The electrospinning method is a method of forming a solution into a fiber shape by drawing the solution into a fine fiber shape using an electric attractive force.

  FIG. 4D shows an outline of an example of an electrospinning apparatus 300 that performs an electrospinning method. This apparatus includes a container 301 for storing a solution 421 containing the above-described electron transport material precursor, a nozzle 302 for injecting the solution 421 stored in the container 301 toward the dense portion 41, and a nozzle 302. A circuit 303 for applying a voltage. The solution 421 includes a polymer material such as a binder and is set to have a relatively high viscosity. The dense portion 41 is electrically grounded through a ground wire 304.

When a high voltage (for example, about several kV to several tens kV) is applied between the nozzle 302 and the dense part 41, the solution 421 of the nozzle 302 is ejected to the dense part 41 at a high speed by electrical attraction. .
According to such an electrospinning method, the solution can be efficiently formed into very fine fibers. As a result, finally, fine fibrous particles can be efficiently produced.
Next, the solution 421 formed into a fiber is subjected to a heat treatment as shown in FIG. 4 (e) to react the precursor of the electron transport material in the solution (for example, hydrolysis, polycondensation, etc.). . Thereby, a fibrous electron transport material, that is, the needle-like body 420 is produced.

Further, along with this heat treatment, the needle-like bodies 420 and the needle-like bodies 420 that are in contact with the dense portion 41 are partially joined. In this way, the porous portion 42 shown in FIG. 4F is formed on the dense portion 41, and the electron transport layer 4 is formed.
Here, as the precursor of the electron transport material, for example, when titanium oxide is used as the electron transport material, titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide, etc. The organic titanium compound can be used.

At this time, the temperature of the heat treatment is preferably about 300 to 700 ° C., and more preferably about 400 to 600 ° C., for example, when titanium oxide is used as the electron transport material.
The heat treatment time varies slightly depending on the heat treatment temperature, but is preferably about 1 to 180 minutes, more preferably about 5 to 60 minutes.

Examples of the heat treatment atmosphere include an oxidizing atmosphere and an inert atmosphere.
If necessary, the obtained electron transport layer 4 may be pressurized so that the dense portion 41 and the porous portion 42 are pressure-bonded. Thereby, the crimping | compression-bonding strength between the dense part 41 and the porous part 42 improves, and it can prevent more reliably peeling in these interfaces.

[3] Next, the electron transport layer 4 is brought into contact with a dye solution D1 containing a dye (sensitizing dye). Thereby, the dye enters the electron transport layer 4.
As a method of bringing the dye solution into contact with the electron transport layer 4, for example, as shown in FIG. 5G, a method of immersing the substrate 2 provided with the electron transport layer 4 in the dye solution D1 (immersion method), an electron Although a method (a spraying method) for supplying the dye solution to the transport layer 4 in a shower form can be used, an immersion method is particularly preferable. According to this dipping method, the dye can be supported efficiently and uniformly on the electron transport layer 4.

  In this case, the time for immersing the electron transport layer 4 in the dye solution D1 is not particularly limited, but is preferably about 0.5 to 72 hours, and more preferably about 2 to 24 hours. Thereby, a necessary and sufficient amount of the dye can be supported on the electron transport layer 4. In addition, although the time to immerse may be made longer than the said upper limit, it cannot expect the further increase in a load.

Further, the temperature of the dye solution D1 at this time is not particularly limited, but is preferably about 20 to 100 ° C, more preferably about 50 to 90 ° C. Thereby, it is possible to efficiently support the dye on the electron transport layer 4 while preventing deterioration of the dye, discoloration, a decrease in photoelectric conversion ability, and the like due to heat.
For the electron transport layer 4 immersed in the dye solution D1, the dye solution D1 is dried as necessary.
The dye liquid D1 can be dried by a method similar to the method for removing the dispersion medium.

[4] Next, the counter substrate 7 is prepared, and the second electrode 6 is formed on the counter substrate 7.
The second electrode 6 can be formed by the same method as the first electrode 3.
[5] Next, as shown in FIG. 5 (h), the counter substrate 7 including the second electrode 6 is arranged so that the first electrode 3 and the second electrode 6 face each other. A partition wall 8 is provided over the entire periphery of the edge between the first electrode 3 and the second electrode 6. Thereby, a liquid-tight space 9 defined by the first electrode 3, the second electrode 6 and the partition wall 8 is obtained.
A part of the partition wall 8 is provided with a through hole (not shown) communicating with the space 9 and the outside of the space 9.
The partition wall 8 is made of, for example, various adhesives such as epoxy adhesives and silicone adhesives, various resin materials such as epoxy resins and silicone resins, and the like.

[6] Next, as shown in FIG. 5 (i), an electrolytic solution is injected into the space 9 through the through hole and filled. The injected electrolyte solution also penetrates into the electron transport layer 4. Thereby, the electrolyte layer 5 is formed.
Subsequently, the through hole is sealed with the constituent material of the partition wall 8.
In addition, what is necessary is just to gelatinize electrolyte solution by the effect | action of a gelatinizer, after inject | pouring the electrolyte solution containing a gelatinizer into the space 9 when making electrolyte solution into a gel form.

[7] Next, the ends of the external circuit 10 are connected to the first electrode 3 and the second electrode 6, respectively.
As described above, the solar cell (photoelectric conversion element of the present invention) 1 is manufactured.
In FIG. 1, the electron transport layer 4 is divided into a dense portion 41 and a porous portion 42, but the entire electron transport layer 4 may be composed of the porous portion 42. Even in such a case, the redox ions 51 can pass through the holes formed in and on the surface of the electron transport layer 4. For this reason, the carrier mobility in the solar cell 1 becomes high, and there can exist an effect of an improvement in photoelectric conversion efficiency.

<< Second Embodiment >>
Next, a second embodiment of the solar cell will be described.
FIG. 6 is a longitudinal sectional view schematically showing a second embodiment when the photoelectric conversion element of the present invention is applied to a solar cell, and FIGS. 7 and 8 illustrate a method for manufacturing the solar cell shown in FIG. It is a schematic diagram for.

Hereinafter, although the solar cell concerning 2nd Embodiment is demonstrated, it demonstrates centering around difference with the solar cell concerning the said 1st Embodiment, and the description is abbreviate | omitted about the same matter.
As shown in FIG. 6, the solar cell 1 according to this embodiment has an electron transport layer 4 that is fixed and bonded by covering the dense portion 41 and the porous portion 42 with a covering portion 43, The same as in the first embodiment.

  Since the electron transport layer 4 having such a configuration includes the covering portion 43 formed so as to continuously cover the dense portion 41 and the porous portion 42, the electron transport layer 4 is provided between the dense portion 41 and the porous portion 42. Can be securely fixed and bonded. Thereby, the dense part 41 and the porous part 42 can be joined more firmly while preventing the electron mobility from being significantly reduced at the joining interface between the dense part 41 and the porous part 42. For this reason, the highly reliable electron carrying layer 4 which can prevent interface peeling for a long term can be obtained.

Such a coating | coated part 43 is comprised with the metal oxide or its precursor.
Examples of such metal oxides include various metal oxides used as semiconductor materials in the first embodiment.
Examples of the metal oxide precursor include a material that generates a metal oxide in association with a chemical reaction such as hydrolysis or polycondensation. Specifically, metal alkoxide, titanium tetrachloride, etc. Can be used.

Next, a method for manufacturing the electron transport layer 4 according to the present embodiment will be described.
First, as shown in FIG. 7A, a solution 421 containing a precursor of an electron transport material is supplied into a separately prepared recovery substrate 305 while forming into a fiber shape. As this forming / supplying method, for example, an electrospinning method as shown in FIG. In addition, as the precursor of the electron transport material, for example, the organic titanium compounds described in the first embodiment can be used.

FIG. 7A schematically shows an example of an electrospinning apparatus 300 that performs an electrospinning method. The configuration of this apparatus is the same as that of the first embodiment. In the present embodiment, the solution 421 is supplied onto the recovery substrate 305. For this reason, the collection substrate 305 is electrically grounded by the ground wire 304.
When a high voltage (for example, about several kV to several tens of kV) is applied between the nozzle 302 and the recovery substrate 305, the solution 421 of the nozzle 302 is jetted onto the recovery substrate 305 at high speed due to electrical attraction. . Thereby, the fiber structure 422 is formed on the recovery substrate 305.

Next, as shown in FIG. 7B, the formed fiber structure 422 is peeled from the collection substrate 305.
Next, as shown in FIG. 7C, the peeled fiber structure 422 is subjected to heat treatment. Thereby, the porous part 42 comprised by the fibrous electron transport material, ie, the acicular body 420, can be produced. The conditions for this heat treatment are the same as those in the first embodiment.
On the other hand, in the same manner as in the first embodiment, the first electrode 3 is formed on the substrate 2 and the dense portion 41 is formed on the first electrode 3.

And as shown in FIG.8 (d), the porous part 42 produced on the dense part 41 is piled up.
Next, as shown in FIG. 8E, a solution 423 containing a precursor of a semiconductor material is infiltrated into the laminated body of the dense portion 41 and the porous portion 42. In addition, the penetration method is not particularly limited, and examples thereof include a dipping method and a spraying method, and a method of dropping the solution 423 on the laminate as shown in FIG.

  Next, after being immersed in the solution 423, the substrate 2 provided with the dense portion 41 and the porous portion 42 is baked as shown in FIG. As a result, the solution 423 that has permeated the dense portion 41 and the porous portion 42 is baked, and the covering portion 43 shown in FIG. 6 is formed. As a result, the dense portion 41 and the porous portion 42 are fixed by the covering portion 43, and the electron transport layer 4 shown in FIG. 6 is obtained. The firing (heat treatment) conditions are the same as those in the first embodiment.

In addition, if necessary, the dense portion 41 and the porous portion 42 may be pressurized and bonded together.
As described above, the electron transport layer 4 used in the solar cell (photoelectric conversion element of the present invention) 1 according to this embodiment is manufactured.
As described above, in the present embodiment, by using the recovery substrate 305, it is possible to avoid the substrate 2 and the first electrode 3 from being exposed to a high temperature. Accordingly, the fiber structure 422 can be heat-treated at a higher temperature, so that the range of heat treatment conditions can be expanded. As a result, the degree of necking of the needle-like body 420 can be widely controlled, and the photoelectric conversion efficiency can be improved.

  Further, for example, the first electrode 3 is made of a material with low heat resistance but excellent electrical characteristics, or the substrate 2 is made of a material with low heat resistance but excellent optical characteristics and high flexibility. You will be able to That is, the range of selection of the constituent materials for the substrate 2 and the first electrode 3 is increased. As a result, finally, the solar cell 1 having high photoelectric conversion efficiency and excellent flexibility can be obtained.

<Electronic equipment>
The electronic device of the present invention includes such a solar cell 1.
Hereinafter, the electronic apparatus of the present invention will be described with reference to FIGS. 9 and 10.
FIG. 9 is a plan view showing a calculator to which the electronic device of the present invention is applied, and FIG. 10 is a perspective view showing a mobile phone (including PHS) to which the electronic device of the present invention is applied.

A calculator 100 illustrated in FIG. 9 includes a main body 101, a display unit 102 provided on the upper surface (front surface) of the main body 101, a plurality of operation buttons 103, and a solar cell installation unit 104.
In the configuration shown in FIG. 9, five solar cells 1 are connected in series to the solar cell installation unit 104.
A mobile phone 200 shown in FIG. 10 includes a main body unit 201, a display unit 202 provided on the front surface of the main body unit 201, a plurality of operation buttons 203, an earpiece 204, a mouthpiece 205, and a solar cell installation unit 206. ing.

In the configuration shown in FIG. 10, a plurality of solar cells 1 are connected in series so that the solar cell installation unit 206 surrounds the periphery of the display unit 202.
As mentioned above, although the photoelectric conversion element of this invention, the manufacturing method of an electron carrying layer, the manufacturing method of a photoelectric conversion element, and an electronic device were demonstrated based on each embodiment of illustration, this invention is not limited to these. .

For example, in each figure, the needle-like bodies (fibrous materials) of the porous portion in the electron transport layer are arranged in a relatively regular manner, but this arrangement state may be any, and partially or entirely It may be an irregular array.
Moreover, each part which comprises a photoelectric conversion element and an electronic device can be substituted with the thing of the arbitrary structures which can exhibit the same function.

The photoelectric conversion element of the present invention can be applied not only to solar cells but also to various elements (light receiving elements) that receive light and convert it into electrical energy, such as optical sensors and optical switches. It is.
Moreover, in the photoelectric conversion element of this invention, the incident direction of light may be from the reverse direction unlike the thing of illustration. That is, the incident direction of light is arbitrary.
Moreover, in the manufacturing method of the electron carrying layer of this invention, and the manufacturing method of a photoelectric conversion element, the process for arbitrary objectives may respectively be added 1 or 2 or more.

Next, specific examples of the present invention will be described. In addition, this invention is not restrict | limited by this Example.
1. Manufacture of solar cell (photoelectric conversion element) (Example 1)
The solar cell (photoelectric conversion element) shown in FIG. 1 was manufactured as follows.

[1A] First, a glass substrate (average thickness 1 mm) provided with an FTO film (first electrode) having an average thickness of 1 μm was prepared.
[2A] Then, a liquid material used for forming a dense portion of the electron transport layer on the FTO film was prepared. This was done as follows.
First, a dispersion (paste) containing a substantially spherical titanium dioxide (anatase, manufactured by Catalyst Chemical Industry) powder having an average particle diameter of 20 nm was prepared. And this dispersion liquid was apply | coated on the FTO film | membrane by the squeegee printing method, and the liquid film was formed.

[3A] Next, the liquid film was heated at 450 ° C. to remove the dispersion medium in the liquid film, thereby obtaining a dense part having an average thickness of 10 μm.
[4A] Next, 1.23 parts by weight of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd., special grade) is added to 1 part by weight of titanium tetranormal butoxide (manufactured by Wako Pure Chemical Industries, Ltd., first grade) to obtain a uniform solution. Got. By adding 1 part by weight of ion-exchanged water with stirring to this solution, a gel was formed in the solution. The produced gel was dissociated by further stirring, and a clear solution could be prepared.

To the prepared solution, 0.016 part by weight of polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., first grade, average molecular weight 300,000 to 500,000) was mixed to prepare a titanium dioxide precursor solution. This solution was supplied onto the dense part while being formed into a fiber by electrospinning.
Next, the fibrous material is heated to 600 ° C. over 10 hours in an air atmosphere using an electric furnace, and then held at 600 ° C. for 2 hours, whereby a porous structure having a network structure composed of titanium dioxide is formed. Got a part. The average fiber diameter was 300 nm, and fibers with a fiber length of 100 μm or less were not observed.
Moreover, the obtained porous part had a high light reflectance compared with the dense part obtained by the said process [3A].

[5A] Next, the porous portion was pressed against the dense portion to fix them. As a result, an electron transport layer was obtained on the FTO film.
[6A] Next, cis-bis (isothiocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylato) -ruthenium (II) bis-tetrabutylammonium (N719) as a pigment, acetonitrile and t-butyl alcohol Was dissolved in a solvent mixed at a volume ratio of 1: 1 to prepare a dye solution. In addition, the density | concentration (content rate) of N719 pigment | dye in a pigment | dye solution was 0.3 mM.
Next, the glass substrate with an electron transport layer prepared in the above [1A] to [5A] was immersed in the dye solution, left in a dark place for 12 hours, and then taken out.
The glass substrate taken out was washed with ethanol and then dried at room temperature. Thereby, the pigment | dye was carry | supported in the electron carrying layer.
[7A] Next, a glass substrate (opposing substrate, average thickness 1 mm) comprising an FTO film (average thickness 1 μm) and a platinum film in this order was prepared.
[8A] Next, two glass substrates were arranged at a predetermined interval so that the platinum film and the electron transport layer face each other, and the edges were sealed with an epoxy adhesive except for a part.

[9A] Next, an electrolytic solution was injected from the portion that was not sealed. This electrolytic solution dissolves DMPII (1,2-Dimethyl-3-Propylimidazolium lodide), TBP (t-Butylpyridine), I ₂ and LiI (lithium iodide) in acetonitrile (solvent) under nitrogen atmosphere. Prepared. The concentration of each electrolyte, DMPII is 0.6M, TBP was 0.5M, _{I 2} is 0.05 M, LiI is a 0.1 M. The redox ions in the electrolyte were I ₃ ⁻ and I ⁻ , and the ratio thereof was 5: 7.
Moreover, the size of the void | hole formed in the porous part was 300 to 1000 times with respect to the ion diameter of this redox ion.
[10A] Next, the part that was not sealed was sealed with an epoxy adhesive to obtain a solar cell.

(Example 2)
First, a dense part was formed on the FTO film in the same manner as in the steps [1A] to [3A].
Next, 1.23 parts by weight of acetic acid (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) was added to 1 part by weight of titanium tetranormal butoxide (manufactured by Wako Pure Chemical Industries, Ltd., primary) to obtain a uniform solution. A gel was formed in the solution by adding 1 part by weight of ion-exchanged water to this solution while stirring. The produced gel was further dissociated by continuing stirring, and a clear solution could be prepared.

To the prepared solution, 0.016 parts by weight of polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., first grade, average molecular weight 300,000 to 500,000) was mixed to prepare a titanium dioxide precursor solution. From this solution, a fiber structure was formed on the collection substrate while being formed into a fiber by electrospinning.
Next, the fiber structure is peeled from the recovery substrate, and the peeled fiber structure is heated to 600 ° C. for 10 hours in an air atmosphere using an electric furnace, and then held at 600 ° C. for 2 hours to obtain carbon dioxide. A porous part having a network structure composed of titanium was obtained. The average fiber diameter was 300 nm, and fibers with a fiber length of 100 μm or less were not observed.

Next, the obtained porous part was overlapped on the dense part, and a solution obtained by diluting the above transparent solution with ion-exchanged water was dropped and immersed. Next, the temperature is raised to 500 ° C. for 10 hours using an electric furnace in an air atmosphere, and then held at 500 ° C. for 2 hours to join the dense portion and the porous portion, and the dense portion and the porous portion are joined. An electron transport layer composed of a laminate with a mass part was obtained.
Next, a solar cell was obtained in the same manner as in the above steps [6A] to [10A].

(Comparative Example 1)
A solar cell was obtained in the same manner as in Example 1 except that the steps [4A] to [5A] were omitted. That is, thereby, a solar cell in which the porous portion was omitted was obtained.
The thickness of the dense part formed in the step [3A] was set to 15 μm by increasing the thickness of the liquid film formed in the step [2A].

(Comparative Example 2)
A solar cell was obtained in the same manner as in Example 1 except that the step [4A] was replaced with the following step [4B].
[4B] Next, a dispersion (paste) containing a substantially spherical titanium dioxide (anatase, manufactured by Catalyst Kasei Kogyo) powder having an average particle diameter of 400 nm was prepared. And this dispersion liquid was apply | coated on the FTO film | membrane by the squeegee printing method, and the liquid film was formed.
Subsequently, this liquid film was heated at 450 ° C. to remove the dispersion medium of the liquid film, thereby obtaining a porous portion having an average thickness of 5 μm.

2. Evaluation The current-voltage characteristics of the solar cells produced in each Example and each Comparative Example were measured using an IV tester under the condition of AM 1.5 (100 mW / cm ² ) using a solar simulator. And the open circuit voltage, short circuit current, form factor (fill factor), and photoelectric conversion efficiency of each solar cell were calculated | required.

Note that the open circuit voltage is a state where nothing is connected to both electrodes of the solar cell, the voltage generated between both electrodes, the short-circuit current is the current flowing through the circuit in the state where both electrodes of the solar cell are short-circuited, and the shape The factor is defined as maximum output / (open circuit voltage × short circuit current), respectively.
Further, the photoelectric conversion efficiency is a ratio of output electric energy to irradiated light energy.
The measurement results are shown in Table 1.

As is clear from Table 1, the solar cells obtained in each example had higher photoelectric conversion efficiency than the solar cells obtained in each comparative example.
In particular, the solar cell obtained in Example 1 showed the highest value of the shape factor as well as the photoelectric conversion efficiency.

It is a longitudinal cross-sectional view which shows typically 1st Embodiment at the time of applying the photoelectric conversion element of this invention to a solar cell. FIG. 2 is an enlarged view schematically showing a part of the solar cell shown in FIG. 1. It is a schematic diagram for demonstrating the manufacturing method of the solar cell shown in FIG. It is a schematic diagram for demonstrating the manufacturing method of the solar cell shown in FIG. It is a schematic diagram for demonstrating the manufacturing method of the solar cell shown in FIG. It is a longitudinal cross-sectional view which shows typically 2nd Embodiment at the time of applying the photoelectric conversion element of this invention to a solar cell. It is a schematic diagram for demonstrating the manufacturing method of the solar cell shown in FIG. It is a schematic diagram for demonstrating the manufacturing method of the solar cell shown in FIG. It is a top view which shows the calculator to which the electronic device of this invention is applied. It is a perspective view which shows the mobile telephone (PHS is also included) to which the electronic device of this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Solar cell 2 ... Substrate 3 ... 1st electrode 4 ... Electron transport layer 41 ... Dense part 410 ... Granule 411 ... Liquid coating 42 ... Porous part 420 ... Acicular body 421 …… Solution 422 …… Fiber structure 423 …… Solution containing precursor of semiconductor material 43 …… Coating part D …… Dye layer D1 …… Dye solution d …… Dye 5… Electrolyte layer 51 …… Redox ion 6 …… Second electrode 7 …… Counter substrate 8 …… Partition wall 9 …… Space 10 …… External circuit 100 …… Calculator 101 …… Main unit 102 …… Display unit 103 …… Operation buttons 104 …… Solar cell installation Part 200 …… Cellular phone 201 …… Body part 202 …… Display part 203 …… Operation buttons 204 …… Earpiece 205 …… Speaker 206 …… Solar cell installation part 300 …… Electrospinning device 3 1 ...... container 302 ...... nozzle 303 ...... circuit 304 ...... ground wire 305 ...... collecting substrate

Claims (19)

A first electrode;
A second electrode provided opposite to the first electrode;
An electron transport layer located between the first electrode and the second electrode;
A dye layer in contact with the electron transport layer;
An electrolyte layer located between the electron transport layer and the second electrode and containing an electrolyte solution containing redox ions;
At least a portion of the electron transport layer on the electrolyte layer side is formed of a porous portion made of a fibrous material made of a semiconductor material and capable of passing the redox ions. Photoelectric conversion element.   The photoelectric conversion element according to claim 1, wherein the semiconductor material contains a metal oxide as a main component.   3. The photoelectric conversion element according to claim 1, wherein the fibrous material has an average fiber diameter of 1 μm or less and substantially no fiber having a fiber diameter of 5 μm or more.   The photoelectric conversion element according to any one of claims 1 to 3, wherein the aggregate of fibrous objects has a network structure in which a plurality of the fibrous objects are three-dimensionally combined. A part of the electron transport layer is composed of a porous portion made of an aggregate of the fibrous materials,
The part other than the porous part of the electron transport layer is constituted by a dense part composed of an aggregate of particles having an average particle diameter smaller than the average fiber diameter of the fibrous material. The photoelectric conversion element in any one of.   The photoelectric conversion element according to claim 5, wherein a light reflectance of the porous portion of the electron transport layer is larger than a light reflectance of the dense portion.   The photoelectric conversion element according to claim 5, wherein the porous portion is fixed to the dense portion.   The photoelectric conversion element according to claim 5 or 6, wherein the porous portion is bonded to the dense portion using a metal oxide or a precursor thereof.   The photoelectric conversion element according to claim 5, wherein an average thickness of the porous portion is 10 to 80% of an average thickness of the dense portion.   The photoelectric conversion element according to any one of claims 1 to 9, wherein a size of pores of the porous portion is 30 to 30000 times an ion diameter of the redox ions. The photoelectric conversion element according to claim 1, wherein the redox ions in the electrolytic solution are substantially I ₃ ⁻ and I ⁻ . In the electrolytic solution, when the content of I ₃ ⁻ is A [mol / L] and the content of I ⁻ is B [mol / L], A / (A + B) is 0.3 to 0.6. The photoelectric conversion element according to claim 11. Producing a fiber structure containing a precursor of the semiconductor material on a recovery substrate from a solution containing the precursor of the semiconductor material;
Peeling the fiber structure from the recovery substrate;
Firing the peeled fiber structure and changing it to an aggregate of fibrous materials composed of a semiconductor material;
An electron transport layer in which at least a portion on the side opposite to the electrode is formed of a porous portion through which redox ions can pass by laminating the aggregate of the fibrous materials on one surface side of the layered electrode. Forming a step,
The manufacturing method of the electron carrying layer characterized by producing the electron carrying layer used for a photoelectric conversion element. In advance, on one surface of the electrode, a dense part composed of an aggregate of particles having an average particle diameter smaller than the average fiber diameter of the fibrous material is formed,
After that, the fibrous material aggregate is laminated on the dense portion, and the solution containing the precursor of the semiconductor material is infiltrated into the laminated fibrous aggregate, and then the electrode is baked. The manufacturing method of the electron carrying layer of Claim 13 which adheres the said dense part and the said porous part by this. Laminating a fiber structure containing a precursor of the semiconductor material from a solution containing a precursor of the semiconductor material on one surface side of the layered electrode;
A porous electrode through which redox ions can pass through at least a portion opposite to the electrode by firing a layered electrode laminated with the fiber structure and changing it to an aggregate of fibrous materials composed of a semiconductor material. A step of forming an electron transport layer composed of parts,
The manufacturing method of the electron carrying layer characterized by producing the electron carrying layer used for a photoelectric conversion element. In advance, on one surface of the electrode, a dense part composed of an aggregate of particles having an average particle diameter smaller than the average fiber diameter of the fibrous material is formed,
Then, the manufacturing method of the electron carrying layer of Claim 15 which laminates | stacks the said fiber structure on this dense part.   The manufacturing method of the electron carrying layer in any one of Claim 13 thru | or 16 which produces the said fiber structure from the said solution by the electrospinning method. Forming a dye layer so as to be in contact with the electron transport layer produced by the method for producing an electron transport layer according to claim 13;
Disposing a counter electrode on the opposite side of the electrode via the electron transport layer and the dye layer;
A method for producing a photoelectric conversion element comprising: filling an electrolyte containing the redox ions between the electrode and the counter electrode.   An electronic apparatus comprising the photoelectric conversion element according to claim 1.

Images